A hydrodynamic sliding bearing member

TECHNICAL FIELD

The invention relates to a hydrodynamic sliding bearing member having a first sliding surface and configured for being slidably arranged in a circumferential direction relative to a second sliding surface of a second sliding member via a viscous fluid. The invention also relates to a hydrodynamic sliding bearing arrangement such as a journal bearing, a main bearing, a connecting rod bearing, comprising a hydrodynamic sliding bearing member.

Furthermore, the invention relates to an internal combustion engine for a vehicle comprising a hydrodynamic sliding bearing member. Moreover, the invention relates to a vehicle comprising a hydrodynamic sliding bearing member.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described in relation to a truck, the invention is not restricted to this particular vehicle, but may also be used in other type of vehicles such as cars, industrial construction machines, wheel loaders, etc. The invention may also be applied in any other type of mechanical devices that employ journal bearings.

BACKGROUND

In the field of engines and engines components, such as internal combustions engine, and in particular diesel-powered combustion engines, there is an increasing demand for reducing fuel consumption by improving efficiency of the components and/or re-designing some of the components making up the combustion engine.

One factor of particular importance for enabling a reduction in fuel consumption relates to the science of tribology, and more specifically to engine frictional losses, i.e. the power lost overcoming friction between mating surfaces and associated shear loss of different contacting media. Tribology refers to the science of friction, lubrication and wear.

Typically, there are at least two types of friction in the engine: mechanical friction due to mechanical contact, usually boundary and hydrodynamic (or viscous) friction due to shearing of oil. A majority of the engine modifications relating to reducing friction losses in engines merely addresses boundary friction. However, there are also some activities in finding solutions on how to reduce hydrodynamic friction losses within engine

components. For instance, it has been observed that the increase in fuel consumption is an effect of increased hydrodynamic friction losses of various engine components. In addition, hydrodynamic friction has a significant contribution to the total friction. However, it is not a simple task to design engine components with respect to mechanical friction and hydrodynamic friction since the effect of decreasing e.g. the viscosity of oil in order to decrease the average hydrodynamic friction between two components may result in an increase of the average mechanical friction between the components.

Thus, it would be desirable to reduce hydrodynamic friction losses without an increase of the mechanical friction losses.

A significant part of the total friction losses in engines are found in sliding bearing arrangements, such as journal bearings, main bearings or connecting rod bearings of a vehicle. As an example, for a journal bearing to work efficiently, a fluid film such as a viscous fluid should separate the sliding surfaces of the bearing. One significant function of the viscous fluid is to provide protection for moving parts, thereby reducing friction and wear of the machine. The viscous fluid may typically also contribute to cooling, debris removal and prevention of corrosion.

The sliding surfaces may be formed by, for instance, a shaft and a shell of the arrangement. A fluid film can be generated using both, or one of, hydrodynamic pressure build-up caused by the motion of the sliding surfaces, and, hydrostatic pressure caused by an oil pump delivering oil pressure directly to the component. In other words, lubrication reduces friction between the two surfaces in relative motion. The type of lubrication, i.e. the lubrication regime, is commonly categorised as boundary lubrication, mixed lubrication or hydrodynamic lubrication. When for instance a journal bearing operates under boundary lubrication, the sliding surfaces of the bearing member and the shaft member are mostly in direct contact with each other, despite the presence of a fluid, and friction is thereby at its highest level. Lower friction levels are achieved through the use of mixed lubrication, where the sliding surfaces are partially separated, partially in contact, by the lubricant. With respect to the latter regime, i.e. hydrodynamic lubrication, the sliding surfaces are essentially completely separated by the lubricant. In

hydrodynamic lubrication, the hydrodynamic pressure in the lubricant keeps the sliding surfaces of the bearing and shaft separated from each other. The hydrodynamic pressure is caused by the sliding motion. Accordingly, and in basic terms, the thickness of the film exceeds the combined roughness height of the surfaces. When a journal bearing is operating in the hydrodynamic lubrication regime, the coefficient of friction is generally lower than with boundary lubrication. Wear is generally not as severe in the hydrodynamic lubrication regime as in the boundary and mixed lubrication regime. This is partly due to that little, or no, direct metal-to-metal contact occurs in the hydrodynamic lubrication regime.

Sliding bearing arrangements such as journal bearings are relatively inexpensive compared to other bearings with a similar load rating. A sliding bearing arrangement can be as simple as two smooth surfaces with seals to retain the viscous fluid. In addition, a journal bearing is typically uncomplicated to manufacture, easy to assemble and disassemble, has low weight and capable of handling large transients in acceleration and load. However, one of the drawbacks with journal bearings is that the arrangement gives large frictional losses, in particular compared to e.g. rolling element bearings. One reason for this is that the journal bearing has significantly larger mating surface areas, i.e. sliding surface areas, compared to a rolling element bearing. In addition, the sliding velocity is typically much higher for a journal bearing compared to a rolling element bearing. To this end, a large contact area in combination with a high sliding speed gives high viscous frictional losses for journal bearings, i.e. high shearing of the fluid film.

Furthermore, hydrodynamic journal bearings are critical power transmission components that are carrying increasingly high loads because of the increasing power density in the vehicles. In order to reduce the friction losses in sliding bearing

arrangements, such as journal bearings, some researchers and developers have focused on making sliding surfaces smoother in the region where mechanical contact occurs. Smoother plateau surfaces have several benefits for the combustion engine such as less wear particles in running in phase etc. Rather to the contrary, in other proposed arrangements, a texture pattern has been provided on the sliding surfaces of the sliding bearing arrangement in order to obtain a more constant contact pressure and better conformability between surfaces as seen over the axial direction of the bearing arrangement after running-in has been completed.

For example, US 2005/0175263 A1 discloses a sliding device comprising a first sliding member and a second sliding member that are slidably arranged and supported through a viscous fluid. In addition, there is provided at least one pit on at least one of the first and second sliding members in order to generate a viscous fluid flow. In some examples, there is a set of pits arranged in a uniform pattern on one of the sliding surfaces. In this manner, a sliding device is provided that aims at reducing friction, while maintaining an anti-seizing property.

However, the positioning and/or the geometry of texture patterns and texture elements may have different effects depending on whether the sliding bearing arrangement operates in the boundary, mixed or the hydrodynamic lubrication regime. That is, the overall design of a journal bearing operating in the hydrodynamic lubrication regime may not be the same as in the boundary and/or mixed lubrication regime. On the contrary, if a texture pattern and/or texture elements intended for the hydrodynamic lubrication regime were used for the boundary lubrication regime, this type of pattern and/or elements would likely contribute to an increase in friction and possibly cause the system to seizure. To this end, research and development activities relating to sliding bearing arrangements operating in the hydrodynamic lubrication regime are generally demanding and complex assignments that require extensive knowledge of combustion engines and combustion engine components.

It would thus be desirable to provide a sliding bearing member of a sliding bearing arrangement and a sliding bearing arrangement capable of reducing friction losses more efficiently in the hydrodynamic lubrication regime and at a low cost, while minimizing the level of wear of the components making up the sliding bearing arrangement. SUMMARY

It is an object of the present invention to provide an improved hydrodynamic sliding bearing member for reducing friction losses in the hydrodynamic lubrication regime, which is also capable of reducing the risk of having lubrication leakage at an axial boundary of the bearing member.

According to a first aspect of the invention, the object is achieved by a

hydrodynamic sliding bearing member according to independent claim 1 . Further optional features of the invention are recited in the dependent claims.

Thus, according to the first aspect of the invention there is provided a

hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, and configured for being slidably arranged in the circumferential direction relative to a second sliding surface of a second sliding member via a viscous fluid to permit the hydrodynamic sliding bearing member to operate under hydrodynamic lubrication. The first sliding surface has opposite boundaries, as seen in the axial direction. In addition, the first sliding surface has a texture pattern, which comprises at least one texture element. Moreover, an area density of the texture element decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction.

Typically, although not strictly necessary, the texture pattern may comprise a plurality of texture elements. In addition, an area density of the texture elements decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction.

By the provision that the first sliding surface has a texture pattern, wherein the area density of the texture element(s) decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction A, it becomes possible to provide a hydrodynamic sliding bearing member which is capable of further reducing frictional losses in the hydrodynamic lubrication regime, while reducing lubrication leakages at the axial boundary of the hydrodynamic sliding bearing member.

The inventor has recognized that a significant part of the total friction losses in an internal combustion engine and its components are viscous friction losses, and has observed that a reduction of the viscous losses is beneficial for reduction of fuel consumption. By arranging the texture element(s) as mentioned above, the textured pattern is configured to generate a decrease in the average shear force of the sliding surfaces of the bearing member (or bearing arrangement) at the locations of the texture element(s) in order to minimize hydrodynamic (viscous) friction losses

Another advantage is that the hydrodynamic sliding bearing member has the potential to lower the hydrodynamic friction losses without any significant increase of the mechanical friction losses.

As mentioned above, one advantage by the provision that the area density of the texture elements (or the at least one texture element) decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction, is that the present invention contributes to reduce the risk of having a lubrication leakage at the axial boundary of the hydrodynamic sliding bearing member, thus decreasing the risk of material-to-material contact. In this context of the exemplary embodiments, the term "material" should be distinguished from the film separating the two members (first sliding bearing member and second sliding bearing member), thus the term "material" here typically refers to the solid parts (most commonly metal) of the component. An increased amount of material-to-material contact is considered to increase the boundary friction. That is, a leakage of lubrication at the axial boundary typically has a negative impact on the possibility of generating a hydrodynamic pressure at the hydrodynamic sliding bearing member. By improving the overall generation of

hydrodynamic pressure, the hydrodynamic friction is significantly reduced. In other words, leakage causes a decreased build-up of hydrodynamic pressure, thus increasing friction. Hence, by decreasing the area density of the texture element(s) towards at least one of the axial boundaries, the overall generation of hydrodynamic pressure is improved, thus decreasing friction. In this way, the texture arrangement of the present invention is optimized for a hydrodynamic sliding bearing member in terms of hydrodynamic friction losses.

Thus, decreasing the area density of texturing towards the axial boundaries produces less side leakage compared to increasing the area density of texturing towards the axial boundaries or keeping the area density constant across the axial width of the bearing, given that the average area density is equal in above three examples. Minimising the side leakage increases the generation of hydrodynamic pressure, thus decreasing friction.

A further benefit of providing the textured pattern with texture element(s) according to the above arrangement is that wear on sliding surfaces may be reduced because wear particle debris can be retained in the texture elements of the textured pattern. This type of wear is often denoted three-body abrasion. Three-body abrasion can be described with foreign (wear) particles entering the fluid film that separates two surfaces or are generated in material-to-material contact of the two surfaces; in this context, having foreign particles between two mating surfaces increases friction. In tribological contacts, the concentration of foreign particles can increase over time; both because particles can continuously be generated from contact between the mating surfaces and also because foreign particles can remain in the contact zone a significant amount of time, thus allowing for a

concentration of particles in the contact with time. The latter may cause the number of foreign particles that enter a tribological contact to be greater than the amount of particles that exit the tribological contact.

By improving entrapment of wear particles in the contact, which decreases the amount of three-body abrasion, the friction can be reduced in an even more efficient way compared to other prior art devices. In this manner, entrapment of wear particles is directly related to frictional issues.

Since decreasing engine frictional losses has a positive impact on fuel

consumption, the present invention also has a direct effect on the reduction of fuel consumption.

The hydrodynamic sliding bearing member according to the present invention can be used in various hydrodynamic sliding bearing arrangements, such as main bearings, journal bearings, connecting rod bearings etc. Thus, the invention is mainly applied for hydrodynamic sliding bearing arrangements, such as journal bearings etc., which have a transient behaviour during each revolution. In other words, the present invention is particularly useful for components (surfaces) that are rotatably (and slidably) arranged or configured to support a rotational motion in contrast to surfaces or components that are subjected to a reciprocating motion, such as a piston and cylinder liner. Hence, the term "slidably" or "slidably arranged" may herein refer to interacting surfaces in relative motion.

Typically, the texture pattern is applied for parts of the hydrodynamic sliding bearing member which have an excess of fluid film thickness on a part or the completed circumference surface having the smallest separation during operation. For largest frictional reduction, the amount of texture elements should be correlated to the amount of excess fluid film thickness. The texture elements are applied to decrease the contact area of the sliding (mating) surfaces and to decrease the total shear resistance of the fluid, thus decreasing friction. The shear resistance or drag losses within texture elements can be considered to be insignificant if the texture element depth is sufficiently large. In simple terms, without being bound by any theory, the shear resistance is to be considered as inversely proportional to the fluid film thickness in the texture elements. The fluid film thickness in texture elements should here be compared with an untextured surface and the typical fluid film thickness separating (untextured) components. A typical minimum fluid film thickness separating (untextured) components may be in the order of 1 -5 μηι. However, this range of the thickness is dependent on a multitude of parameters. Given that the fluid film thickness is 5 μηι, for a texture element with 100 μηι depth, the shear resistance within texture elements is approximately decreased with 95 % in the textures compared to the typical fluid film thickness separating the untextured components.

In other words, by using the texture pattern and the texture elements according to example embodiments of the present invention, the excess fluid film thickness can be utilized to decrease the frictional losses for a hydrodynamic sliding bearing member and a hydrodynamic sliding bearing arrangement operating in the hydrodynamic lubrication regime.

In view of some prior art devices, which aims at reducing friction in the boundary and/or mixed lubrication regimes by utilising various surface modification techniques, e.g. using texture patterns to improve conformability of the components, the present invention provides the effect of reducing frictional losses in the hydrodynamic regime in an optimal manner, and without any significant increase of the mechanical friction losses.

Typically, the hydrodynamic sliding bearing member extends in the axial direction A, the circumferential direction C and a radial direction R. Typically, the texture element extends in the axial direction A, the circumferential direction C and the radial direction R of the hydrodynamic sliding bearing member.

The expression "textured pattern" is expressly defined for purposes of the example embodiments of the present invention as a regular, repeated pattern of distinct elements (typically in the form of depressions) such as depressions in the form of closed voids or grooves in the surface. The substantial remainder of the surface may be defined by one or more plateaus. In addition, the texture pattern may in some example embodiments refer to one single texture element, in which the area density of the texture element is decreasing towards the axial boundary(s). It should be noted that surface irregularities can also exist on the plateau surface area, however, said irregularities are of a

significantly smaller wavelength and significantly smaller amplitude compared to texture elements. The textured pattern can be provided in any suitable way, such as by being machined via a milling, turning, or drilling operation, via chemical etching, water-jet cutting, abrasive blasting, or hydro-erosive grinding, or some combination of such operations. Other types of production methods than those listed above may also be used to produce texture elements.

In some example embodiments, the texture pattern comprises a set of axial rows of texture elements arranged in succession along the circumferential direction C, wherein the texture elements of at least one axial row are offset from the texture elements of another axial row, as seen in the axial direction A, so that a circumferential segment of the first sliding surface intersects at least one texture element in a substantial part of the first sliding surface. The circumferential segment extends in the circumferential direction. The circumferential segment typically extends across the entire circumferential length of the hydrodynamic sliding bearing member.

An advantage of this arrangement of the axial rows of texture elements is that the possibility of entrapment of wear particles is significantly improved since there is no path that is not obstructed by a texture element for the particles to travel a significant distance in the circumferential direction of the first sliding surface. In other words, there is a least one texture element to entrap the wear particle independently on the current travelling path of the wear particles across the axial direction. Thus, it becomes possible to further increase the efficiency of entrapping wear particles.

It should be readily appreciated that the provision that an area density of the texture element(s) decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction A, may refer to a given area of the first sliding surface, i.e. for a given surface element of the first sliding surface. However, in some example embodiments, the provision that an area density of the texture element(s) decreases towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction A, may refer to the entire area of the sliding surface.

In some example embodiments, the area density of the texture element(s) decreases towards at least one of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A, by decreasing at least one of an axial length E _A and circumferential length E _c of each texture element per unit area towards the axial boundary, as seen from the centre of the first sliding surface in the axial direction A.

This type of texture pattern is typically less complicated to design and

manufacture. In addition, this type of texture pattern may reduce the risk of having leakages at the axial boundaries in a simple, yet efficient manner. In addition, if the depth of the texture element(s) is varied along the texture pattern, this type of texture pattern may reduce the risk of having leakages at the axial boundaries even further.

The geometrical form of the texture elements can be described by an axial length and a circumferential length in the sliding bearing surface of the hydrodynamic sliding bearing member and a depth radially inward of the sliding bearing surface of the sliding bearing member. In other words, each texture element has an extension in the axial direction A, an extension in the circumferential direction C and an extension in the radial direction R of the hydrodynamic sliding bearing member.

A minimum axial length of the texture element may ordinarily be equal to or above 300 μηι. Analogously, a minimum circumferential length of the texture element may ordinarily be equal to or above 300 μηι. however, it should be readily appreciated that an axial length and/or circumferential length of 300 μηι is to be regarded merely as an example of when the effects of the invention may be particularly significant. Thus, for another examples embodiment, the effects may still obtained by a length of the texture elements outside this value. Thus, the axial length E _A of the texture elements may typically be at least equal to or above 300 μηι. Analogously, the circumferential length E _c of the texture elements may be at least equal to or above 300 μηι. This size of the texture element ensures that the boundary effects do not become too large so as to reduce the effects of the exemplary embodiments as mentioned above.

Boundary effects can be described with the following: When an arbitrary location on a mating surface starts to transvers a texture element, the shear friction losses do not decrease instantly. The generation of hydrodynamic pressure decreases much more rapidly for said motion than the shear friction losses. This means that if the texture elements are of too short elongation in the direction of motion, the relative decrease in generation of hydrodynamic pressure will be comparatively significantly larger than the decrease in shear friction loss, which will eventually increase the amount of material-to- material contact increasing boundary friction. If the textures are sufficiently large, boundary effects are reduced to an extent that is no longer significant.

However, it should be readily appreciated that a smaller size of the texture elements may be conceivable if the sliding motion of the hydrodynamic sliding bearing member is low in a certain application of the exemplary embodiments. Thus, in some example embodiments, it may be conceivable to reduce the axial length and/or the circumferential length below 300 μηι, and still obtain the effects of the exemplary embodiments as mentioned herein.

Still preferably, the axial length E _A of the texture elements may be between substantially 300 - 10 000 μηι. In addition, or alternatively, the circumferential length E _c of the texture elements may still preferably be between substantially 300-10 000 μηι.

Still preferably, the axial length E _A of the texture elements may be between substantially 1 000 - 10 000 μηι. In addition, or alternatively, the circumferential length E _c of the texture elements may still preferably be between substantially 1 000 - 10 000 μηι.

Still preferably, the axial length E _A of the texture elements may be between substantially 2 000 - 10 000 μηι. In addition, or alternatively, the circumferential length E _c of the texture elements may still preferably be between substantially 2 000 - 10 000 μηι.

The depth of the texture element(s) should typically be above 10 μηι. A depth of the texture elements may ordinarily be between substantially 20 - 200 μηι. In some example embodiments, a minimum depth of the texture element(s) may be substantially equal to 35 μηι. While it is presently believed that providing texture elements or depressions with depths less than 35 μηι, such as around 20 μηι, may, in some circumstances provide beneficial results, in some circumstances textures or depressions with depths around 30 μηι may actually increase friction, and it is presently believed that texture elements or depressions of at least 35 μηι and, likely, substantially greater than 35 μηι will provide most beneficial results.

According to one example embodiments, the hydrodynamic sliding bearing member comprises a texture pattern having a plurality of the texture elements, wherein the depth of the texture elements is between about 20 - 200 μηι. Still preferably, the depth of the texture elements should be between about 35 - 200 μηι. Still preferably, a minimum depth of the texture elements may be equal to or greater than 35 μηι. According to one example embodiments, the hydrodynamic sliding bearing member comprises a texture pattern having one texture element, wherein the depth of the texture element is between about 20 - 200 μηι. Still preferably, the depth of the one texture element should be between about 35 - 200 μηι. Still preferably, a minimum depth of the one texture element may be equal to or greater than 35 μηι.

According to some example embodiments, the area density of the texture elements decreases towards at least one of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A, by decreasing the quantity of texture elements towards at least one of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A.

It should be readily appreciated that decreasing the area density may either be linear or non-linear. That is, in some example embodiments, the quantity of texture elements towards at least one of the axial boundaries is decreasing linearly, as seen from the centre of the first sliding surface in the axial direction A. In other example

embodiments, the quantity of texture elements towards at least one of the axial boundaries may be decreasing non-linearly, as seen from the centre of the first sliding surface in the axial direction A.

It is to be noted that the quantity of texture elements and how the quantity of the texture elements should decrease towards the axial boundary, i.e. from a texture element at the centre of the first sliding surface to a texture element at the axial boundary is typically selected in view of the dimensions and shapes of the sliding bearing member and the texture elements, type of installation and purpose, as well as type of texture pattern.

According to some example embodiments, the area density of the texture element(s) decreases towards both of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A.

According to at least one example embodiment, a depth of the texture element(s) forming the textured pattern decreases towards at least one of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A. By the provision that the depth of the texture element(s) forming the textured pattern decreases towards at least one of the axial boundaries, it becomes possible to further reducing the risk of having fluid leakage at the axial boundary. This is due to that an increased depth will increase the leakage at the axial boundary, thus decreasing the hydrodynamic pressure and thus increasing friction. The depth of the texture elements and the relationship between a texture element at the centre of the first sliding surface and a texture element at the axial boundary is typically selected in view of the dimensions and shapes of the sliding bearing member and the texture elements as well as type of texture pattern.

However, without being bound by any theory, it is believed that the texture elements should be sufficiently deep so that the viscous film shear force within the texture elements is negligible, texture boundary effects excluded. Negligible viscous film shear force is here defined as that the viscous film shear force in texture elements, texture boundary effects not included, should typically be less than 5 % compared to the viscous film shear force acting between the plateaus of the two surfaces. By having texture elements with a negligible contribution to the viscous film shear force, it will also be possible to provide texture elements having a negligible contribution to the hydrodynamic pressure build-up. Since a negligible contribution to the hydrodynamic pressure build-up is obtained, it may be appreciated that the depth of the texture elements can be selected appropriately as long as the above mentioned viscous film thickness criteria is meet.

Alternatively, the depth of the texture element(s) forming the textured pattern may be kept constant towards at least one of the axial boundaries, as seen from the centre of the first sliding surface in the axial direction A.

Typically, the depth of the texture element(s) forming the textured pattern may be kept constant towards both axial boundaries, as seen from the centre of the first sliding surface in the axial direction A.

According to one example embodiment, an outer region of the first sliding surface adjacent an axial outer boundary is free from texture elements. Hereby, it becomes possible to further reduce the risk of fluid lubrication leakage or even avoid the risk of fluid lubrication leakage. The importance of reducing the risk of fluid lubrication leakage lies in that axial leakage has an effect on the hydrodynamic pressure build-up along all of the axial length L _c . Since the effect is largest at the axial boundaries, the risk is further improved by providing a region of no texture elements adjacent and around the axial boundaries to counteract the leakage in an efficient manner. As an example, the term "outer region" may refer to 5 % of the total area of the first sliding surface as seen in the axial distance. Still preferably, the extension of the outer region may be between 0.1 - 10 % of the total axial length of the sliding surface. Still preferably, the extension of the outer region may be between 0.1 - 5 % of the total axial length of the sliding surface.

Typically, the textured pattern comprises a plurality of texture elements in the form of depressions. It is to be noted that texture elements or depressions may also herein be denoted as closed voids. In one example, the textured pattern comprises one texture element in the form of a groove. In addition, it should be readily appreciated that the texture elements are typically configured for containing viscous fluid.

It is to be noted that the depth of the texture element may be defined as the depth in the radial direction, and further defined as the distance from the sliding surface to the bottom surface of the texture element.

In addition, the texture element may typically be regarded as depressions rather than that the plateau areas that are areas that extrude from the bottom surface of the texture element.

The shapes of the texture elements may be provided in several different forms. For instance, any one of the texture elements may have a cross-sectional shape in the form of a square, rectangle, circle, or ellipse. In this context of the present invention, it is to be noted that the cross-sectional shape here refers to the extension of the texture element in the circumferential direction and the radial direction.

In addition, or alternatively, the shape as seen in the axial direction and the circumferential direction may resemble a part of a rectangle. However, other shapes are conceivable such as a part of a circle, or part of an ellipse, or the like. In one example embodiment, the shape as seen in the axial direction and the circumferential direction is an ellipse.

According to one example embodiment, the cross-sectional shape of the texture element, as seen along the circumferential direction and the radial direction may resemble a rectangle. Since the circumferential direction typically refers to the sliding direction of the hydrodynamic sliding bearing member (and the sliding surface), the cross sectional shape may here also refer to the cross sectional shape of the texture element, as seen in the sliding direction and the radial direction. In this example embodiment, the texture element is formed by two opposite radial side walls projecting inwardly from the sliding surface in the radial direction and essentially arranged perpendicular to the circumferential direction of the sliding surface and by a bottom texture element surface extending between the opposite radial side walls. Typically, one of the radial side walls is a leading surface of the texture element and the other radial side wall is a trailing surface of the texture element. The bottom texture element surface is further essentially perpendicular arranged to the leading surface and the trailing surface. By having opposite radial side walls (leading surface and trailing surface) arranged perpendicular to the first sliding surface, the opposite radial side walls forms essentially right angles with the sliding surface. Thus, one of the radial side walls is a trailing surface and the other radial side wall is a leading surface, as seen in the sliding direction. By having a texture element with a trailing surface that forms a right angle with respect to the first sliding surface, boundary effects are minimized thus the friction within the texture will require a smaller sliding distance to reduce shear losses compared to is said angle would have been smaller. This may typically provide the additional effect that viscous film shear losses can be kept to at a minimum level. In this context, it should be readily appreciated that completely straight angles may be difficult to manufacture, and it is thus conceivable that the angles may refer to essentially straight angles considering the limitations of the selected machining methods. However, this type of cross sectional shape is typically not capable of providing an increase, or merely a very small increase, of the hydrodynamic pressure due to the somewhat sharp angle between the trailing surface of the texture element and the first sliding surface of the hydrodynamic first bearing member.

In order to gain an increase in the hydrodynamic pressure generation at the trailing surface, it has been observed that the trailing surface should be angled, or inclined, with respect to the sliding surface of the bearing member. However, it has also been observed that this type of cross sectional shape of having an inclined surface extending to the bottom surface of the texture element may be detrimental to the viscous film shear losses, i.e. it may typically lead to an increase in viscous film shear losses. This is partly due to that the length of the bottom surface of the texture element, as seen in the circumferential direction, is shorter compared to an essential rectangular shaped cross section since the extension of the texture element in the circumferential direction (here sliding direction) for the rectangular shaped cross section is defined by the length of the bottom surface of the texture element, while the circumferential length of the texture element with an inclined surface is defined by the length of the bottom surface of the texture element and the circumferential extension of the inclined trailing side wall. Thus, the extension of the bottom surface of the texture element having an inclined surface at the trailing region is shorter for the two types of cross sectional shapes provided that they have similar lengths along the circumferential direction.

Based on the effects of these two possible examples of cross sectional shapes of the texture element design, it has been observed that the shape may be improved in order to both gain an increase in the hydrodynamic pressure generation, while reducing the viscous film shear losses and enabling an increased fluid film thickness thus decreasing the likelihood of material-to-material friction and subsequent increase in contact friction and wear.

Accordingly, in one example embodiment, there is provided a texture element having a trailing region defined by a trailing surface extending from the first sliding surface to the bottom surface of the texture element. Moreover, a first section of the trailing surface is adapted to define a converging gap with a sliding surface of a second sliding member and extends a distance from the first sliding surface in the radial direction, which is smaller than 50% of the texture element depth.

By the provision that the first section of the trailing surface is adapted to define a converging gap with the sliding surface of the second sliding member and that the first section extends a distance from the first sliding surface in the radial direction, which is smaller than 50% of the texture element depth, there is provided a texture element which is capable of increasing the hydrodynamic pressure generation, by increasing the fluid film thickness separating the two active surfaces (first sliding surface and second sliding surface), thus reducing the viscous film shear losses. This type of configuration of the texture element shape further contributes to maintain the contact in the hydrodynamic lubrication regime, while minimizing any possible contribution from boundary friction.

In other words, there is provided a texture element shape that is both capable of increasing the hydrodynamic pressure generation, by utilising an optimal design at the trailing side of the texture, and, at the same time reducing the viscous film shear losses compared to a texture element shape having a leading surface (leading region) and a trailing surface (trailing region) that each forms a right angle with respect to the sliding surface, i.e. a texture shape having an essentially rectangular shaped cross section as seen in the circumferential direction and the radial direction.

To this end, the converging gap is configured to generate an increase in hydrodynamic pressure, which results in that the viscous film thickness separating the two active surfaces is increased. Due to an increase in the viscous film thickness, the hydrodynamic friction is reduced, thus reducing the viscous film shear losses, while minimizing any possible contribution from boundary friction.

Without being bound by any theory, it has been observed that when two surfaces move relative to each other via a viscous fluid (hydrodynamic lubrication), the viscous fluid will typically be dragged into the interface. Thus, a viscous fluid that enters the converging gap as defined by the first section of the texture element results in that the converging gap geometry contributes to an increase in hydrodynamic pressure as the defined gap converges towards the first sliding surface, which thus creates a hydrodynamic lift, and further forces the surfaces apart like a wedge.

In this context, the term "converging gap" refers to the geometry of the first section of the texture element, which upon a sliding motion of the first sliding surface relative to the second sliding surface generates a hydrodynamic pressure in the viscous fluid film in conjunction with the opposite second sliding surface of the second sliding member. In this manner, the example embodiments of the invention provides a texture element shape having an optimized surface for generating a hydrodynamic pressure in a viscous fluid film confined between the sliding surfaces of the bearing arrangement, i.e. between two solid surfaces with a relative sliding motion. Accordingly, the example embodiments are configured to utilize the hydrodynamic effect of the viscous fluid in the converging gap as defined by the first section in conjunction with the second sliding surface in order to minimize the frictional forces between the first sliding bearing member and the second sliding bearing member. In addition, it should be readily appreciated that the first section of the trailing surface of the texture element forms the converging gap with the sliding surface of the second sliding member during operation, i.e. when the first sliding surface is sliding relative to the second sliding surface so as to operate under hydrodynamic lubrication. In other words, the first section of the trailing surface is configured to form a converging gap with the sliding surface of the second sliding member during operation of the hydrodynamic sliding bearing member. That is, the first section of the trailing surface is configured to form a converging gap with the sliding surface of the second sliding member during operation of the hydrodynamic sliding bearing arrangement.

According to one example embodiment, there is thus provided a sliding surface comprising a texture pattern having a plurality of texture elements, wherein each texture element has a trailing region defined by a trailing surface extending from the first sliding surface to the bottom surface of the texture element. Moreover, a first section of the trailing surface of each texture element is adapted to define a converging gap with the sliding surface of the second sliding member and extends a distance from the first sliding surface in the radial direction, which is smaller than 50% of the texture element depth.

The configuration of the first section of the trailing surface may be designed in several different ways in order to define (form) a converging gap with a sliding surface of a second sliding member as will be described further herein.

In some example embodiments, the distance may even be smaller than 50% of the texture element depth. Preferably, the distance from the first sliding surface in the radial direction may be smaller than 40% of the texture element depth. Still preferably, the distance from the first sliding surface in the radial direction may be smaller than 25 % of the texture element depth. Still preferably, the distance from the first sliding surface in the radial direction may be smaller than 10 % of the texture element depth. Still preferably, the distance from the first sliding surface in the radial direction R may be smaller than 5 % of the texture element depth. Typically, the distance from the first sliding surface in the radial direction is at least more than 0 % of the depth of the texture element depth. According to one example, the distance from the first sliding surface in the radial direction is at least more than 2 % of the depth of the texture element depth. Hence, as an example, the distance from the first sliding surface in the radial direction is at least more than 2 % of the depth of the texture element depth, but smaller than 50% of the texture element depth. In another example, the distance from the first sliding surface in the radial direction is at least more than 5 % of the depth of the texture element depth, but smaller than 30% of the texture element depth.

In addition, the first section of the trailing surface may typically have an extension in the circumferential direction which is larger than 5% and smaller than 50% of the length of the texture element in the circumferential direction. Still preferably, the first section of the trailing surface may typically have an extension in the circumferential direction which is larger than 10% and smaller than 50% of the length of the texture element in the circumferential direction. Still preferably, the first section of the trailing surface may typically have an extension in the circumferential direction which is larger than 15% and smaller than 50% of the length of the texture element in the circumferential direction.

Typically, the first section may also have an axial extension, which is tapering along the circumferential direction in a direction away from a leading edge of the texture element. Other shapes of the first section may also be conceivable. According to one example embodiment, the tapered first section defines a convex curvature, as seen in the axial direction and in the circumferential direction.

According to one example embodiment, the degree of the curvature of the tapered first section of the trailing surface is greater than a curvature of the leading edge of the texture element. However, it is also conceivable that the degree of the curvature of the tapered first section is similar to the curvature of the leading edge of the texture element.

The trailing surface may in some example embodiments further be defined by a second section. Hence, the trailing surface is generally defined by the first section and the second section. Typically, although not strictly required, the second section of the trailing surface extending from the bottom surface has a normal with a different direction than a normal of the first section.

According to one example embodiment, said second section of said trailing surface extending from the bottom surface is arranged to extend essentially perpendicular from said bottom surface. However, in some example embodiments, the second section may be inclined with respect to the bottom surface by an angle between 45 - 90 degrees, as long as the first section is adapted to form the converging gap with the second sliding surface upon operation of the hydrodynamic sliding bearing member (arrangement).

In addition, the first section and the second section are typically connected at a transition point.

As mentioned above, the first section of the trailing surface may be adapted in several different ways in order to define (form) a converging gap with a sliding surface of a second sliding member as will be described further herein.

According to one example embodiment, the texture element has a cross sectional shape extending in the circumferential direction and a radial direction, said first section of the trailing surface being arranged to deviate from said first sliding surface by an angle a _c . In this manner, the first section of the trailing surface is adapted to define the converging gap with a sliding surface of a second sliding member by means of having the first section of the trailing surface arranged to deviate from the first sliding surface by an angle a _c .

It should be readily appreciated that the first sliding surface here refers to the plateau area of the first sliding surface. Accordingly, the texture element has a cross sectional shape extending in the circumferential direction and a radial direction, the first section of the trailing surface being arranged to deviate from the plateau area of the first sliding surface by the angle a _c .

Typically, the angle a _c may be between 0.1 - 5 degrees. In this way, there is provided a texture element shape configured to provide an optimal build-up of

hydrodynamic pressure. However, it should be readily appreciated that the size of angle ac may be set to another angle depending on the selection of manufacturing method having specific limitations. Also, operation conditions, sliding velocities, contact conditions oil film thickness and application of the texture element and the hydrodynamic sliding bearing member may cause a _c to be selected in a different interval then specified herein.

As an example, the angle a _c is about 0.5 degrees. In another example, the angle a _c is about 0.3 degrees. Still preferably, the angle a _c may be between 1 - 3 degrees.

Thus, it should be conceivable that the value of the angle a _c may be different for different bearing members and installations.

According to one example embodiment, the texture element has a cross sectional shape extending in the circumferential direction and the radial direction, said first section of the trailing surface being arranged to deviate from said first sliding surface by an angle ac, and wherein the first section is a straight wall surface as seen in the cross section extending in the circumferential direction and a radial direction. In this manner, it becomes possible to provide a texture element shape that is capable of increasing the hydrodynamic pressure generation, while reducing the viscous film shear losses and maintaining the contact in the hydrodynamic lubrication regime and minimizing any possible contribution from boundary friction.

Accordingly, in one example embodiment, there is provided a texture element having a trailing region, as seen in the sliding direction along the circumferential direction, said trailing region having a trailing surface defined by a first inclined section and a second section. Furthermore, the second section extends perpendicular from the bottom surface of the texture element to the first inclined section, wherein said second section has a length smaller than said texture element depth, in which the depth is defined by the distance between the sliding surface and the bottom surface of the texture element, as seen in radial direction. In addition, the first inclined section extends from the transition point to the sliding surface of the hydrodynamic sliding bearing member, wherein the first inclined section forms the angle a _c with the sliding surface of the hydrodynamic sliding bearing member.

In another example embodiment, the first section of the trailing surface is adapted to define (form) a converging gap with a sliding surface of a second sliding member by a curved wall surface. Thus, according to one example embodiment, the first section is a curved wall surface as seen in a cross section extending in the circumferential direction and a radial direction. Typically, the first section extends to the second section of the trailing surface, as mentioned herein. In this way, there is provided a texture element shape configured to provide an optimal build-up of hydrodynamic pressure.

In another example embodiment, the first section of the trailing surface is adapted to define (form) a converging gap with a sliding surface of a second sliding member by having a step shaped first section. Thus, according to one example embodiment, said first section is a step shaped section being defined by a first step surface extending essentially perpendicular from said sliding surface and a second step surface extending essentially perpendicular from said first surface to a second section.

Typically, although not strictly required, the texture element is defined by a leading region having a leading surface extending from said bottom surface to said first sliding surface by an angle of between 45 - 90 degrees.

In this context, it should be readily appreciated that completely straight angles (90 degrees) may be difficult to manufacture, and it is thus conceivable that the straight angles may refer to essentially straight angles considering the limitations of the selected machining method. According to one example embodiment, the texture element is defined by a leading region having a leading surface extending essentially perpendicular from said bottom surface to said first sliding surface.

Typically, the bottom surface may be essentially parallel to said sliding surface. By having a texture element, in which the bottom surface is essentially parallel to the sliding surface it is ensured that texture depth is sufficient along the tangential texture element length (length of the texture element in the circumferential direction), thus maintaining the desired fluid film thickness within the texture and thus not increasing the viscous shear losses.

This example embodiment of the shape of the texture element having an inclined second surface may, as mentioned above, be a part of any one of a main bearing, journal bearing or connecting rod bearing of an internal combustion engine of a vehicle.

In addition, or alternatively, the cross-sectional shape as seen in the axial direction and in the radial direction may resemble a part of a rectangle. However, other shapes are conceivable such as a part of a circle, or part of an ellipse.

Typically, an area between two adjacent texture elements may form a plateau area.

Optimally, although not strictly necessary, each of the plateau areas of the first sliding surface of the hydrodynamic sliding bearing member may be provided with a machined roughness (sometimes also denoted as a machined roughness pattern). As an example, the direction of the machined roughness may extend essentially along the entire axial length of the first sliding surface. Hence, the direction of the machined roughness may be orthogonal to the sliding direction (circumferential direction). By having plateau areas with a machined roughness pattern being orthogonal to the sliding direction (circumferential direction), the generation of the hydrodynamic pressure may increase even if a certain type of texture elements have a negative impact on the generation of the hydrodynamic pressure. Thus, it becomes possible to obtain a surface lay that is orthogonal with the sliding direction to improve the building-up of hydrodynamic pressure. The machined roughness may for instance refer to arithmetical mean roughness.

The surface area of the plateau area may be between about 20-95 percent of a total area of the first sliding surface. In this context of the present invention, the area of the sliding surface not being occupied by the texture elements may refer to the plateau area. The plateau area may also herein be denoted as a non-textured surface area, or simply as a plateau. Thus, a textured area of the texture pattern may be between about 5-80 percent of a total area of the first sliding surface. A textured area of the texture pattern between about 5-80 percent of a total area of the first sliding surface provides a sufficiently large area with zero friction and an improved utilization of the non-linear behavior of film thickness and oil film pressure which generates the largest possible relative average film thickness.

According to one example embodiment, the textured area of the texture pattern is between 30 - 50 percent. In this manner, the greatest possible reduction in friction is provided, while retaining the tribological contact in the hydrodynamic lubrication regime.

With regards to the arrangement of the texture elements, it is to be noted that the texture elements are typically arranged in a set of rows, as mentioned above, wherein at least one of the rows is located offset from another row, or several other rows.

Accordingly, at least a part of the plurality of the texture elements of the texture pattern is arranged in succession in a given area along the axial direction A. In addition, at least a part of the plurality of the texture elements of the texture pattern is further arranged in succession in a given area along the circumferential direction C.

In addition, or alternatively, at least a part of the plurality of the texture elements of the texture pattern is arranged in a grid pattern extending in succession along the axial direction A and the circumferential direction C.

As an example, the texture elements are spaced from one another along the axial direction A by at least 100 μηι. Typically, the distance is measured between a centre region of one texture element and a centre region of another texture element.

According to one example embodiment, the area density of the texture elements is further varied along the circumferential direction C. The area density can be varied in similar manner as mentioned above with respect to decreasing area density towards the axial boundary. In other words, the area density of the texture elements may be varied along the circumferential direction C by decreasing at least one of the axial length E _A and the circumferential length E _c of each texture element per unit along the length of the first sliding surface as seen circumferential direction C of the first sliding surface. Alternatively, the area density of the texture elements may be varied along the circumferential direction C by increasing at least one of the axial length E _A and the circumferential length E _c of each texture element per unit along the length of the first sliding surface as seen circumferential direction C of the first sliding surface.

In addition, or alternatively, the area density of the texture elements may be varied along the circumferential direction C by decreasing the quantity of texture elements along the length of the first sliding surface as seen circumferential direction C of the first sliding surface.

Alternatively, the area density of the texture elements may be varied along the circumferential direction C by increasing the quantity of texture elements along the length of the first sliding surface as seen circumferential direction C of the first sliding surface. It should be readily appreciated that decreasing or increasing the area density along the circumferential direction C may either be linear or non-linear.

In addition, it should be readily appreciated that decreasing or increasing the depth, quantity, or any one of the lengths of the element along the circumferential direction C may also either be linear or non-linear.

In one example embodiment, when the texture pattern comprises one single texture element, the texture element is an elongated continuous groove extending about the circumferential direction C and along the axial direction A as a spiral.

In this manner, the length of the texture element can be greatly bigger than the circumferential length of the hydrodynamic sliding bearing member. One advantage with this type of texture element is that the texture pattern becomes less complicated to produce on the sliding surface.

The invention also relates to a connecting rod of an internal combustion engine, which comprises a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions. In one example embodiment, the connecting rod big end comprises the hydrodynamic sliding bearing member. In addition, or alternatively, the connecting rod small end may comprise the hydrodynamic sliding bearing member.

The invention also relates to a journal bearing, which comprises a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions.

The invention also relates to a main bearing, which comprises a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions.

The invention also relates to a connecting rod bearing of an internal combustion engine, which comprises a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions. In one example embodiment, the connecting rod bearing is arranged in the connecting rod big end. In addition, or alternatively, the connecting rod bearing may be arranged in the connecting rod small end.

The invention also relates to hydrodynamic sliding bearing arrangement comprising a first sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions, and further a second sliding bearing member having a second sliding surface.

In some example embodiments, the first sliding bearing member is centred around the second sliding bearing member so that the hydrodynamic sliding bearing arrangement is configured to support a rotational motion between the first sliding bearing member and the second sliding bearing member. Further, as mentioned above, the first sliding bearing member is configured for being slidably arranged in the circumferential direction relative to the second sliding surface of the second sliding member via the viscous fluid to permit the hydrodynamic sliding bearing arrangement to operate under hydrodynamic lubrication.

In some example embodiments, the first sliding surface of the first sliding member is an inner circumferential surface and the second sliding surface of the second sliding bearing member is an outer circumferential surface. Further, the first sliding member is centred around the second sliding member so that the inner circumferential surface is allowed to slide about the outer circumferential surface via the viscous fluid upon rotation of the second sliding member relative to the first sliding member.

Typically, the inner circumferential surface is allowed to slide about the outer circumferential surface along the circumferential direction C.

It is to be noted the term "centred around" sometimes may refer to that the first sliding member is coaxially arranged about the second sliding member. Thus, the term centred around may refer to the term "coaxially arranged" throughout the description.

It is to be noted that the provision "upon rotation of the second sliding member relative to the first sliding member " may refer to that the first sliding member rotates, while the second sliding member is stationary. Alternatively, the provision "upon rotation of the second sliding member relative to the first sliding member" may refer to that the first sliding member is stationary, while the second sliding member rotates. Alternatively, the provision "upon rotation of the second sliding member relative to the first sliding member" may refer to that the first sliding member rotates and the second sliding member rotates. Sometimes the first sliding member may have a sliding velocity that is smaller than the velocity of the second sliding member. Further, as it further described herein, the first sliding bearing member may sometimes also be a part of the journal shaft, i.e. the inner sliding bearing member of the hydrodynamic sliding bearing arrangement.

According to one example embodiment, the first sliding bearing member comprises an upper shell and a lower shell defining the first sliding surface, in which the upper and lower shells are arranged in a bearing housing.

Typically, the hydrodynamic sliding bearing arrangement further comprises the viscous fluid. The viscous fluid is typically located in-between the first sliding bearing member and the second sliding bearing member.

The viscous fluid is typically a lubrication oil, which is well known to use in e.g. piston machines. The thickness of the viscous fluid may vary according to operation conditions etc. However, the minimum thickness of the viscous fluid may be between about 1 - 5 μηι, as defined by the smallest distance between a non-textured surface area of the first sliding surface and a non-textured surface area of the second sliding surface. However, it should be readily appreciated that this may also be dependent on a multitude or other parameters.

The invention also relates an internal combustion engine for a vehicle, which comprises a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions, wherein the first sliding surface of the hydrodynamic sliding bearing member is an inner surface of a main bearing and the second sliding surface of the second sliding bearing member is a journal shaft surface.

The invention also relates to an internal combustion engine for a vehicle, comprising a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions, and further comprising a journal shaft and a connecting rod. The connecting rod typically comprises a shaft extending between a connecting rod small end (i.e. a piston pin end) having a piston pin opening for receiving a piston pin and a connecting rod big end having a journal shaft opening for receiving a crankshaft journal. Further, the first sliding surface of the hydrodynamic sliding bearing is an inner surface of the journal shaft opening and the second sliding surface is a journal shaft surface, thereby supporting a rotational motion between the connecting rod and the journal shaft.

The invention also relates to a vehicle comprising a hydrodynamic sliding bearing member according to the first aspect and/or example embodiments as mentioned above with respect to the first aspect of the inventions. The invention also relates to a vehicle comprising a hydrodynamic sliding bearing arrangement according to the example embodiments as mentioned above with respect to the first aspect of the inventions and/or with respect to the example embodiments of the bearing arrangement, as described above.

Although the invention will be described in relation to a truck, the invention is not restricted to this particular vehicle, but may also be used in other type of vehicles such as buses, construction equipment, cars, industrial construction machines, wheel loaders, etc.

Furthermore, the invention may not be restricted to vehicles, but may also be used in other type of mechanical devices which utilise journal bearings.

Further, it should be readily appreciated that the exemplified tribological contacts operate in the hydrodynamic lubrication regime, meaning that surfaces are separated by the viscous fluid essentially at all times and no occurrence of material-to-material contact is likely to occur during normal operation of the hydrodynamic sliding bearing member. However, the description of complete separation may sometimes only to be recognised as an aid in clarifying the example embodiments, thus it should be readily appreciated that a real tribological contact of two mating surfaces may experience some material-to-material contact both because a small number of the asperities extending furthest from the surfaces might come into contact and also that three-body particles in the separating film might cause material-to-material contact.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a perspective view of a vehicle in the form of a truck, which is provided with a hydrodynamic sliding bearing arrangement comprising a hydrodynamic sliding member according to an example embodiment of the present invention; Fig. 2a schematically illustrates an exploded view of an example embodiment of parts of an internal combustion engine for a vehicle comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention;

Fig. 2b schematically illustrates the example embodiment of the internal combustion engine in fig. 2a in an assembled configuration, in which the internal combustion engine comprises a hydrodynamic sliding bearing member according to an example embodiment of the present invention;

Fig. 2c is a perspective view of a crankshaft of an internal combustion engine including a hydrodynamic sliding bearing member according to an example embodiment of the present invention, in which the hydrodynamic sliding bearing member is arranged on said crankshaft;

Fig. 2d is a perspective view of a hydrodynamic sliding bearing arrangement in the form of a main bearing comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention, in which the texture pattern is provided on an inner sliding surface of the main bearing;

Fig. 2e is a perspective view of an example embodiment of a connecting rod comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention, in which the texture pattern is provided on any one of the connecting rod big end inner surface and the connecting rod small end inner surface;

Fig. 2f schematically illustrates a cross sectional view of the example embodiment of the connecting rod in fig. 2d according to the present invention;

Fig. 2g is a perspective view of a hydrodynamic sliding bearing arrangement in the form of a main bearing comprising a hydrodynamic sliding bearing member according to another example embodiment of the present invention, in which the texture pattern is provided on an inner sliding surface of the main bearing;

Fig. 3 schematically illustrates a cross sectional view of an example embodiment of a hydrodynamic sliding bearing arrangement according to the present invention; Figs. 4a - 4i schematically illustrate various example embodiments of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to the invention, further, the hydrodynamic sliding bearing member is illustrated from a centre of the circumference corresponding to zero degrees, said surface extends between ± 180 degrees;

Fig. 5a schematically illustrates a more detailed view of an example embodiment of the present invention, e.g. the example embodiment in fig. 4a;

Fig. 5b is a top view of an example embodiment of a texture element of the texture pattern according to the invention, e.g. a texture element as illustrated in fig. 5a; Fig. 5c is a cross sectional view of an example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction;

Fig. 5d is a cross sectional view of another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction;

Fig. 5e is a cross sectional view of yet another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction;

Fig. 5f is a cross sectional view of yet another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction;

Fig. 5g is a cross sectional view of yet another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction; Fig. 5h is perspective view of the example embodiment of the texture element as illustrated in fig. 5b in conjunction with fig. 5e, in which a trailing region of the texture element is illustrated as seen in an axial direction, a circumferential direction and a radial direction;

Figs. 6a - 6b schematically illustrates cross sectional views of various example

embodiments of an inner first sliding surface of a hydrodynamic sliding bearing member, as seen in the axial direction A and the radial direction R, according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

Further, it is to be noted that throughout the description of the example

embodiments, the term "hydrodynamic sliding bearing member" may sometimes be denoted as the sliding bearing member, sliding member or simply as the bearing member. Analogously, the term "hydrodynamic sliding bearing arrangement" may sometimes be denoted as the sliding bearing arrangement, sliding arrangement or simply as the bearing arrangement.

Fig. 1 is a perspective view of a vehicle 1 . The vehicle includes an internal combustion engine 100 with a hydrodynamic sliding bearing member (although not shown in fig. 1 ) according to an example embodiment of the present invention. The

hydrodynamic sliding bearing member is here typically a journal bearing or a part of journal bearing. As will further be described hereinafter, the hydrodynamic sliding bearing member may typically be a part of a hydrodynamic sliding bearing arrangement. The hydrodynamic sliding bearing arrangement and/or the hydrodynamic sliding bearing member can be an integral part of a journal bearing, main bearing, connecting rod, connecting rod big end or connecting rod small end, as will be further described herein. Alternatively, the hydrodynamic sliding bearing member may be a separate part forming the hydrodynamic sliding bearing arrangement in cooperation with another engine component, such as parts of the crankshaft and the connecting rod, as further described herein. The hydrodynamic sliding bearing arrangement, the hydrodynamic sliding bearing member and possible installations of the components in a combustion engine of a vehicle are described in further detail with reference to figs. 2a - 2g, 3, 5a - 5h, and 6a - 6b. The texture pattern of the example embodiments is described with particular reference to figs. 4a - 4i and 5a - 5h.

For sake of simplicity, the vehicle 1 in fig. 1 is a truck, and the following example embodiments of the invention are described based on an exemplary truck to illustrate the configuration of hydrodynamic sliding bearing arrangement and the hydrodynamic sliding bearing member of the invention. However, such does not mean that the invention will be limited to an installation of the hydrodynamic sliding bearing arrangement and/or the hydrodynamic sliding bearing member in a truck. In contrary, the vehicle may be a car, industrial construction machine, wheel loader and the like, as one skilled in the art will recognise. Although not shown, it is also conceivable that the exemplary embodiments may be applied in any other type of mechanical devices that employ journal bearings, for instance a stationary application.

As will be readily understood from the description and with particular reference to figs 4a to 4i and fig. 5a, one example advantage of the example embodiments of the present invention is to reduce fuel consumption by reducing hydrodynamic friction losses in the internal combustion engine of the vehicle in an optimal way.

Referring now to the drawings and fig. 1 in particular, there is depicted a vehicle 1 in the form of a truck, which is provided with a hydrodynamic sliding bearing arrangement 10 comprising a hydrodynamic sliding member 20 according to an example embodiment of the present invention. Moreover, the hydrodynamic sliding bearing arrangement 10 and the hydrodynamic sliding member 20 are arranged in an internal combustion engine 100 of the vehicle 1 . The internal combustion engine can work, for instance, according to the four-stroke and/or two-stroke principle; however, additional modes of operation can exist. The combustion engine 100 may be a compression ignition, spark ignition engine or a piston compressor. The internal combustion engine 100 in fig. 1 is designed to work according to the diesel process. Since the components of an internal combustion engine are well-known, and the function and configuration of the engine can vary dependent on the type of vehicle, only a brief introduction of the engine will be described for the sake of a better understanding on how the present invention can be installed in an internal combustion engine of a vehicle, such as a truck. Accordingly, although not shown in the figures, the engine 100 may generally comprise a cylinder and a piston, which

reciprocates in the cylinder and is connected to a crankshaft so that the piston is set to reverse in the cylinder at an upper and lower dead centre position. As is also common, one end of the cylinder cavity is closed by an engine cylinder head. The piston is provided in its upper surface with a piston bowl, which forms a combustion chamber together with an inner surface of the cylinder head and walls of the cylinder. In other words, a combustion interface is formed between the combustion chamber and the cylinder head. In the cylinder head, one or more induction ports may be arranged. The connection between a respective induction port and the cylinder can be opened and closed with an induction valve disposed in each induction port. In general, one or more exhaust ports are further arranged in the cylinder head. In order to inject fuel into a combustion chamber of a combustion engine cylinder of the internal combustion engine, the engine typically comprises an injector. However, it should be readily appreciated that the engine 100 may include a plurality of injectors for injecting fuel into a combustion chamber of a combustion engine cylinder.

Fig. 2a schematically illustrates an exploded view of an example embodiment of parts of an internal combustion engine for a vehicle comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention, while Fig. 2b schematically illustrates the internal combustion engine in fig. 2a in an assembled configuration. As shown in figs. 2a and 2b, the internal combustion engine 100 here includes at least a set of pistons 19 connected to a set of connecting rods 15,

respectively. Typically, each piston 19 is connected to the connecting rod at the connecting rod small end 16. Furthermore, each connecting rod 15 is connected via the connecting rod big end to a crankshaft 18. The crankshaft is then connected to the engine block by one or several main bearings 14, as further described herein. This type of engine configuration is well known in the art and thus not further described herein. In order to provide a rotatable arrangement and/or support rotatable motion between relevant components, the internal combustion engine may include one or several bearings and/or bearing members. In this example embodiment, the bearing is a hydrodynamic sliding bearing arrangement. Alternatively, some of the current components of the combustion engine may include one or several bearing member(s) to form a bearing arrangement upon rotation of the components relative to each other. As an example, an inner surface of a connecting rod big end and an outer surface of crankshaft journal shaft may form a simple sliding bearing arrangement. In other words, as illustrated in fig. 2a and 2b, and further illustrated in individual figures in fig. 2c to 2g, the hydrodynamic sliding bearing member 20 according to the present invention can be installed as a separate or integral part in a hydrodynamic sliding bearing arrangement 10, for instance as a journal bearing 12. In addition, or alternatively, the hydrodynamic sliding bearing member 20 according to the present invention can be installed as a separate or integral part in the connecting rod 15. As an example, the hydrodynamic sliding bearing member 20 is installed, or incorporated, in the connecting rod small end 16 to form a connecting rod small end bearing 16'. In addition, or alternatively, the hydrodynamic sliding bearing member 20 is installed, or incorporated, in the connecting rod big end 17 to form a connecting rod big end bearing 17'.

In addition, or alternatively, the hydrodynamic sliding bearing member 20 may be installed as a separate part or integral part of a main bearing 14. In some example embodiments, the hydrodynamic sliding bearing member 20 is the main bearing.

It is to be noted that the general constructions of journal bearings, connecting rods, connecting rod end bearings, and main bearings etc. are well known in the art, and the wide variation of types of such components will not be further described herein, although one skilled in the art will not have difficulty in applying the disclosed technique to such components as may be required.

As mentioned above, the hydrodynamic sliding bearing member 20 and the hydrodynamic sliding bearing arrangement 10 according to any one of the example embodiments as will be described with references to figs. 4a - 4i, 5a - 5h, and 6a - 6b can be installed in an internal combustion engine of a vehicle. Figs. 2c to 2g provide some examples and further details on engine components which can include the hydrodynamic sliding bearing member 20 and the hydrodynamic sliding bearing arrangement 10.

Fig. 2c is a perspective view of the crankshaft of the internal combustion engine as shown in figs. 2a and 2b. The crankshaft 18 is typically supported by one or several main bearings 14. The function of a main bearing is mainly to support the rotational motion of the crankshaft. That is, the main bearing should typically hold the crankshaft in place and prevent the forces created by the piston and transmitted to the crankshaft by the connecting rods from dislodging the crankshaft, instead forcing the crank to convert the reciprocating movement into rotation. The main bearing is usually a journal bearing. It should be readily appreciated that although some small single-cylinder engines may have only one main bearing, designed to deal with the bending moment by the crank as a result of the force from the connecting rod, most engines may have at least a plurality of main bearings, as illustrated in figs. 2a, 2b and 2c. In this type of configuration, there is one main bearing at each end of the crankshaft. Typically, although not strictly necessary, some engines may have as many as one more than the number of crank pins. Many engines may have one main bearing at each end of the crankshaft and another in between each adjacent pair of connecting rod journals. However, not all engines conform to this generalization.

In order to facilitate the installation of the main bearings 14 onto the journal of the crankshaft 18, each main bearing may comprise two bearing halves. In other words, each bearing forms a half-circle. Each single bearing may thus be pressed into each of the journals of crankshaft until the bearing click into place.

Such installations and constructions of main bearings and crankshafts are well known in the art, and the wide variation of types of such components will not be further described herein, although one skilled in the art will not have difficulty in applying the disclosed technique to such components as may be required.

One example of a main bearing according to example embodiments of the invention is shown in fig. 2d. That is, fig. 2d is a perspective view of a hydrodynamic sliding bearing arrangement in the form of a main bearing comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention, in which a texture pattern 40 is provided on an inner sliding surface 22 of the main bearing.

It is to be noted that in this example embodiment, and in other example

embodiments, the main bearing 14 may form a hydrodynamic sliding bearing arrangement with the journal of the crank shaft 18. In other words, as shown in fig. 2c and 2d, there is provided a hydrodynamic sliding bearing arrangement 10 comprising a first sliding bearing member 20, which has a first sliding surface 22 (inner sliding surface) and a second sliding member 30, which has second sliding surface 32. In this example, the first sliding member 20 is centred about the second sliding member 30 so that the hydrodynamic sliding bearing arrangement 20 is configured to support a rotational motion between the first sliding member 20 and the second sliding member 30. Typically, the first sliding bearing member 20 is co-axially centred about the second sliding bearing member 30 so that the hydrodynamic sliding bearing arrangement 20 is configured to support a rotational motion between the first sliding member 20 and the second sliding member 30

In addition, a viscous fluid is contained between the surfaces 22 and 32. Optimal, although not strictly necessary, the viscous fluid is contained between the surfaces by means of a seal (not shown) extending around the circumferential boundaries of the members 20 and 30. Such constructions of sealing between sliding surfaces are well known in the art, and therefore not further described herein. Accordingly, in the example embodiment when the first sliding surface 22 of the first sliding bearing member 20 is an inner circumferential surface, the first sliding member 20 is configured to be centred about the second sliding bearing member 30 so that the inner circumferential surface is allowed to slide about the second sliding surface 32, which here corresponds to an outer circumferential surface of the second sliding member, via the viscous fluid 60 upon rotation of the second sliding member 30 relative the first sliding member 20.

Typically, the inner circumferential surface is allowed to slide about the outer circumferential surface along the circumferential direction C.

The viscous fluid 60 is here located in-between the first sliding bearing member 20 and the second sliding bearing member 30.

To this end, the hydrodynamic sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to the second sliding surface 32 of a second sliding bearing member 30 via a viscous fluid 60 to permit the

hydrodynamic sliding bearing member to operate under hydrodynamic lubrication. That is, the first sliding surface 22 of the hydrodynamic sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to a second sliding surface 32 of a second sliding member 30 via a viscous fluid 60 to permit the

hydrodynamic sliding bearing arrangement (main bearing) to operate under hydrodynamic lubrication.

In the context of the exemplary embodiments of the invention herein, it is to be noted that hydrodynamic lubrication refers to that hydrodynamic pressure is generated by the viscous fluid and the sliding motion so that the sliding surfaces are maintained essentially separated from each other. Thus, by the provision that the viscous fluid permits the hydrodynamic sliding bearing member to operate under hydrodynamic lubrication refers to that the hydrodynamic pressure caused by the sliding motion maintains the sliding surfaces essentially separated from each other.

Moreover, each main bearing here includes a hydrodynamic sliding bearing member with a first sliding surface comprising a texture pattern 40 according to the present invention, and which is further described in relation to figs. 4a - 4i, 5a - 5h, and 6a - 6b. As an example, with particular reference to fig. 2c - d, fig. 3 and fig. 4a, the first sliding surface 22 has opposite boundaries 26, 28, as seen in the axial direction A, and a texture pattern 40 comprising a plurality of texture elements 42. Moreover, an area density of the texture elements 42 decreases towards at least one of the axial boundaries 26, 28, as seen from a centre of the first sliding surface 22 in the axial direction A. That is, the texture elements are distributed so that the area density is regarded as decreasing towards the boundary.

In other words, as shown in the figures, there is provided an internal combustion engine 100 for a vehicle 1 , comprising a hydrodynamic sliding bearing member 20 as described herein with respect to the various example embodiments, wherein the first sliding surface 22 of the hydrodynamic sliding bearing member 20 is an inner surface of a main bearing 14 and the second sliding surface 32 of the second sliding bearing member is a journal shaft surface, e.g. the crank shaft 18.

Alternatively, there is provided an internal combustion engine 100 for a vehicle 1 , comprising a hydrodynamic sliding bearing arrangement 10 as described herein with respect to the various example embodiments, wherein the hydrodynamic sliding bearing arrangement 10 includes the hydrodynamic sliding bearing member 20 with the first sliding surface 22 and the second sliding bearing member 30 with the second sliding surface 32. Further, the hydrodynamic sliding bearing member 20 is slidably arranged about the second sliding bearing member 30. In addition, the hydrodynamic sliding bearing member 20 is connected to the engine block. Moreover, the second sliding bearing member 30 is connected to the crank shaft 18. In this manner, the hydrodynamic sliding bearing arrangement 10 is arranged to support a rotational motion of the crank shaft relative to the engine block.

As shown in fig. 2a and 2c, the main bearing may also be provided as a bearing half. In other words, the main bearing forms a half-circle. The half-circle main bearing is typically arranged about the crankshaft at an appropriate distance along the crank shaft as seen in the axial direction.

Although it might be sufficient that only one of the main bearings comprises a hydrodynamic sliding bearing member as described herein, it is to be noted that an optimal technical effect is provided by installing a hydrodynamic sliding bearing member, according to the example embodiments, in all main bearings of the crankshaft.

Another example of a main bearing according to example embodiments of the invention is shown in fig. 2g. That is, fig. 2g is a perspective view of a hydrodynamic sliding bearing arrangement in the form of a main bearing comprising a hydrodynamic sliding bearing member according to an example embodiment of the present invention, in which a texture pattern 40 is provided on an inner sliding surface 22 of the main bearing. In this example embodiment, as is further described herein with respect to e.g. fig. 4i, the texture pattern 40 comprises one texture element 42 which extends about the

circumferential direction as a spiral of helix, but with a varied angle of inclination. Besides this difference, the example embodiment in fig. 2g may incorporate any one the features and/or effects as mentioned above with respect to other figures.

The hydrodynamic sliding bearing member 20 may also be installed in a connecting rod 15, as shown in figs. 2e and 2f. Fig. 2e shows a perspective view of a connecting rod comprising the hydrodynamic sliding bearing member according to an example embodiment of the present invention. In this example embodiment, the texture pattern 40 is provided on both the inner surface 22 of the connecting rod big end 17 and the inner surface 22' of the connecting rod small end 16. In another example embodiment, the texture pattern 40 may only be arranged on the connecting rod big end. Alternatively, the texture pattern 40 may only be arranged on the connecting rod small end.

Fig. 2f schematically illustrates a cross sectional view of the example embodiment of the connecting rod in fig. 2e according to example embodiments of the present invention.

As is shown in fig. 2f, the axial width of the upper part and the lower part of the small end bearing are different, the upper part of the hydrodynamic sliding bearing member arranged on the connecting rod small end 16, which sits closest to the cylinder head is significantly less wide (refer to the axial dimension) compared to the lower part of said hydrodynamic sliding bearing member that sits closest to the crank shaft. This reduction can be completed due to that it is the lower part of the hydrodynamic sliding bearing member that needs to cope with the combustion gas pressure resulting in a contact pressure acting on the lower part of the hydrodynamic sliding bearing member.

The upper part of the hydrodynamic sliding bearing member may only need to account for the contact pressure generated from inertia forces which are typically lower than the contact pressure resulting from the combustion phase. Thus, the axial width of the hydrodynamic sliding bearing member is here designed according to the contact pressure. It is to be noted that if this would not have been the case as eg. the small end bearing would have a contact width this would mean that a certain part of the axial width of the upper area of the hydrodynamic sliding bearing member would be superfluous. Since friction loss is related to the area of the hydrodynamic sliding bearing member said superfluous area would generate additional friction compared to the hydrodynamic sliding bearing member having optimised axial width. In perspective, the texture pattern as described herein according to example embodiments offers the reduction in area, but also, the reduction of friction by using the texture pattern can be achieved much more efficient than merely reducing the area. Typically, although not strictly necessary, the hydrodynamic sliding bearing arrangement is formed by the inner surface 22 of the connecting rod big end 17, corresponding to the first sliding surface, and the outer surface 32 of the journal (shaft) of the crankshaft 18 (shown in e.g. fig. 2a), corresponding to the second sliding surface. In other words, the first sliding bearing member 20 is a part of the connecting rod, while the second sliding member is the crankshaft.

Analogously, with respect to the connecting rod small end, the hydrodynamic sliding bearing arrangement may be formed by the inner surface 22' of the connecting rod small end 16, corresponding to the first sliding surface, and an outer surface of a piston pin of the piston 19 (shown in e.g. fig. 2a), corresponding to the second sliding surface.

In other words, the first sliding member 20' is here a part of the connecting rod, while the second sliding member is the piston pin.

Similar to the configuration as described in relation to figs. 2c and 2d, the first sliding surface 22 or 22' of the first sliding member 20 or 20' is thus an inner

circumferential surface. In addition, the first sliding member 20 or 20' is configured to be centred around the second sliding member so that the inner circumferential surface is allowed to slide about the second sliding surface (the outer circumferential surface of the second sliding member), via a viscous fluid 60 upon rotation of the first sliding member 20 or 20' relative to the second sliding member 30 or 30'.

Accordingly, with reference to e.g. figs. 1 , 2a and 2e, there is shown an internal combustion engine 100 for a vehicle comprising a hydrodynamic sliding bearing member 20 according to the example embodiments described herein, a journal shaft (crankshaft or piston pin)) and a connecting rod. The connecting pin comprises a shaft extending between a connecting rod small end defining a piston pin opening for receiving the piston pin and a connecting rod big end defining a journal shaft opening for receiving the crankshaft journal. The first sliding surface of the hydrodynamic sliding bearing member 20 is here an inner surface of the journal shaft opening and the second sliding surface is here a journal shaft surface (crankshaft outer surface). Thereby, the hydrodynamic sliding bearing member is configured for supporting a rotational motion between the connecting rod and the journal shaft (crankshaft).

In addition, or alternatively, the first sliding surface of the hydrodynamic sliding bearing member may be an inner surface of the piston pin opening and the second sliding surface may be piston pin surface (piston pin outer surface). Thereby, the hydrodynamic sliding bearing member is configured for supporting a rotational motion between the connecting rod and the piston pin. It is also conceivable, although not explicitly illustrated in the figures, that the hydrodynamic first sliding bearing member 20 is a separate part of the connecting rod, which is inserted into the connecting rod big end or the connecting rod small end. In this type of example embodiment, the hydrodynamic first sliding member may be attached to the connecting rod by a suitable process, as is well known in the art, so that the first sliding bearing member essentially becomes an integral part of the connecting rod.

Furthermore, in this type of example embodiment, the hydrodynamic first sliding bearing member 20 forms a hydrodynamic sliding bearing arrangement 10 together with a part of the crankshaft, as mentioned above. That is, the crankshaft is here the second sliding bearing member having a second sliding bearing surface. In this manner, there is provided a connecting rod bearing comprising the hydrodynamic first sliding bearing member and a part of the crankshaft. Alternatively, with respect to the connecting rod small end, the hydrodynamic first sliding bearing member 20 forms a hydrodynamic sliding bearing arrangement 10 together with a part of the piston pin, as mentioned above. That is, the piston pin is here the second sliding bearing member having a second sliding bearing surface. In this manner, there is provided a connecting rod bearing comprising the hydrodynamic first sliding bearing member and a part of the piston pin.

In other words, in one example embodiment, there is provided a connecting rod bearing of an internal combustion engine 100 comprising a hydrodynamic first sliding bearing member 20 according to any one of the example embodiments described hereinafter. The connecting rod bearing may for instance be installed into the connecting rod big end. Alternatively, the connecting rod bearing may be installed into the connecting rod small end.

As is evident from the above description, the hydrodynamic sliding bearing member may in some example embodiments be built into the object of use, e.g. the connecting rod. This type of bearing configuration may sometime be denoted as an integral bearing. Integral bearings are usually made from cast iron or hardened steel. In this context, the term "integral" may refer to that the bearing configuration is a part of the shaft or part of the connecting rod. Depending on the material, an integral bearing may be less expensive but it cannot be replaced. Alternatively, the hydrodynamic sliding bearing member may be provided in the form of a bushing, which is an independent bearing member that is inserted into a housing to provide the first sliding bearing surface. Such constructions of bearing arrangement are well known in the art, and may include solid sleeve, split and clenched bushings. Moreover, as mentioned above, the hydrodynamic sliding bearing member may in some example embodiments be a two-piece bearing member, also known as full bearings. This type of bearing arrangement is particularly useful as a main bearing for a crankshaft. A two-piece hydrodynamic sliding bearing member comprises two halves. Hence, in some example embodiments, there is provided a hydrodynamic sliding bearing arrangement comprising a hydrodynamic sliding bearing member having a first sliding surface, in which the hydrodynamic sliding bearing member (sometimes denoted as the first sliding bearing member) comprises an upper shell and a lower shell defining the first sliding surface. Further, the upper and lower shell may typically be arranged in a bearing housing. As is well known in the art, there are various systems used to keep the shells located. Thus this part of the construction is not further described herein.

In all example embodiments of the present invention as illustrated by the figures, and in other example embodiments, it is to be noted that the hydrodynamic sliding bearing arrangement may typically comprise the viscous fluid 60. As an example, in an operation mode of the exemplary embodiments, a thickness h of the viscous fluid 60 is between about 0.1 - 6 μηι, as defined by a distance between a non-textured surface area of the first sliding surface and a non-textured surface area of the second sliding surface. In other words, thickness h of the viscous fluid 60 may also refer to the separating distance between the first member 20 and the second member 30. Thus, it should be readily appreciated that the thickness may vary depending on the lubrication regime.

Turning now to fig. 3, there is depicted a cross sectional view of an example embodiment of a hydrodynamic sliding bearing arrangement according to the present invention. Accordingly, it is to be noted that fig. 3 may represent a cross sectional view of any one of the example embodiments described above with reference to the main bearing, journal bearing, connecting rod, connecting rod bearing and/or the hydrodynamic sliding bearing arrangement. Fig. 3 shows a simple construction of the bearing

arrangement according to example embodiment in order to describe how the

hydrodynamic sliding bearing member operates in the hydrodynamic lubrication regime. In other words, there is depicted the first hydrodynamic sliding bearing member 20 having the first sliding bearing surface 22. The first hydrodynamic sliding bearing member 20 is here formed by a part of journal shaft, e.g. the connecting rod 15 or the crankshaft. The first hydrodynamic sliding bearing member 20 with the first sliding bearing surface 22 extends in the circumferential direction C and in the axial direction A. The first sliding bearing surface 22 of the sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to a second sliding surface 32 of a second sliding member 30 via the viscous fluid 60. To this end, the first sliding bearing surface 22 moves upon rotation in the circumferential direction C over a stationary surface on a thin fluid film (viscous fluid 60). The direction of the rotation is illustrated by ω (omega). Accordingly, the rotational direction ω is throughout the description of the example embodiments denoted by the sliding direction when the example embodiments are illustrated in a plane view corresponding to a plane along the axial direction A and the circumferential direction C, as shown in e.g. in figs. 4a - 4i. In this type of configurations, the moving surface (first sliding bearing surface 22) will slide over the stationary surface (second sliding surface 32). In this manner, the hydrodynamic sliding bearing member 20 is permitted to operate under hydrodynamic lubrication. Analogously, the second hydrodynamic sliding bearing member 30 is permitted to operate under hydrodynamic lubrication. Thus, it should be readily appreciated that the hydrodynamic sliding bearing arrangement 10 is permitted to operate under hydrodynamic lubrication. In hydrodynamic lubrication, one surface floats over the other surface due to that a hydrodynamic film is formed by the geometry, the surface motion and the fluid viscosity which in combination contribute to an increase in the fluid pressure being sufficiently high to support the load. Further, the increased fluid pressure forces the surfaces apart and prevents surface contact. In this type of hydrodynamic bearing arrangements, the pressure in the oil film is maintained by (1 ) the rotation of the journal (e.g. the crankshaft) and (2) the hydrostatic pressure generated in the oil pump and fed to the bearing. It should be readily

conceivable that the latter is not present in all types of hydrodynamic bearing

arrangements. Instead the bearing may have splash lubrication / oil mist. To this end, the configuration is used to provide load support for a number of applications such as a rotating shaft, as mentioned above.

It should be readily appreciated that the first sliding surface may alternatively be defined by the journal shaft, while the second sliding surface 32 may be defined by the inner surface of the first sliding member, e.g. the connecting rod or the crankshaft depending on the installation of the configuration.

The first sliding surface 22 has opposite boundaries 26, 28 (not shown in fig. 3), as seen in the axial direction A, and a texture pattern 40 (not shown in fig. 3). The texture pattern comprises a plurality of texture elements 42.

However, although a certain type of texture pattern may be applied to a sliding bearing member in order to reduce friction in the boundary and/or mixed lubrication regime, it has been observed that this type of texture pattern may not be suitable for reducing friction losses in the hydrodynamic lubrication regime. This is partly due to that the exemplary embodiments as described herein utilise the non-linear relationship between contact pressure, generation of hydrodynamic pressure and fluid film thickness; in the boundary- and the mixed lubrication regime it may not beneficial, or not practically possible, to reduce the plateau-to-plateau separating fluid film thickness to decrease frictional losses. Instead, for decreasing frictional losses in said lubrication regimes one technique is to increase the oil film thickness by increasing the generation of

hydrodynamic pressure. If textures are significantly deeper than the separating fluid film thickness and have similar design as seen in Fig. 5c, this texture geometry will increase the friction in boundary- and mixed lubrication due to increased material-to-material contact thus increasing friction.

Thus, the positioning and/or the geometry of the texture pattern and the texture elements in the hydrodynamic lubrication regime may not be the same as in the boundary and/or mixed lubrication regime. On the contrary, if a texture pattern and/or texture elements intended for the hydrodynamic lubrication regime were used for the boundary lubrication regime, this type of pattern and/or elements would likely contribute to an increase in friction and possibly cause the system to seizure.

In addition, in spite of an increase in contact, it has been observed that friction decreases for textured surfaces relative to non-textured surfaces. The interaction between two opposing surfaces in sliding motion in which one of these surfaces is textured can be viewed from two perspectives: either the contact is between the plateaus of the two surfaces or the contact is between the plateau part of one surface and the texture element of the textured surface of another surface. In other words, either a part of the plateau area (non-textured part) of the first sliding member is sliding over a plateau area (non-textured part) of the second sliding member or a texture (or texture element) of the first sliding member is sliding over a plateau area of the second sliding member. However, for the textured surfaces, when the opposing surfaces passed a texture element, the fluid film thickness can be considered to be the same as the texture element depth, because the contact between first sliding surface and the second sliding surface is near or fully- flooded. The increase in metal to metal contact for the textured surfaces is understood to be due to a decrease in the build-up of hydrodynamic pressure. There are two causes for loss of hydrodynamic pressure: (1 ) because of leakage of fluid into the texture element; and (2) because less surface area is available for the generation of hydrodynamic pressure.

In view of the aforesaid, the following illustrative example may be used to further describe the correlation between the disclosed techniques of texture pattern, as described in relation to figs. 4a - 4i, 5a - 5h, and 6a - 6b, and the effect of reducing friction losses in the hydrodynamic lubrication regime.

The phenomena of decreasing viscous losses in tribological contact that encompass surface textures are related to the correlation between separation (distance) of mating surfaces and the generation of hydrodynamic pressure. This will be further described by means of an example to a surface having a texturing area density of 50 %, which means that 50 % of the surface area will consist of textures, while the remaining 50 % will be the area between the textures, herein referred as the plateau area or non- textured area. Further, in this example, it is assumed that the exemplified tribological contacts operate in the hydrodynamic lubrication regime, meaning that surfaces are separated by the viscous fluid essentially at all times and no occurrence of material-to- material contact. The description of complete separation is only to be recognised as an aid in clarifying this example, thus it should be readily appreciated that a real tribological contact of two mating surfaces may experience some material-to-material contact both because a small number of the asperities extending furthest from the surfaces might come into contact and also that three-body particles in the separating film might cause material-to-material contact.

It is also to be readily appreciated that the film thickness is here one of the key parameters (sliding velocity and viscosity are generally considered as the other two key parameters for determining the operating characteristics of tribological contacts) for determining the frictional response in the hydrodynamic lubrication regime. Furthermore, for a tribological contact, the film thickness, commonly denoted with h, is regarded as inversely proportional to shear (friction) force.

If the textures in this example are sufficiently large and deep, the hydrodynamic pressure (lift) generated from the textures and also the friction (drag) from the textures will be insignificant, due to that the film thickness separating the surfaces can be regarded as infinite within the texture. If the contribution of hydrodynamic pressure (lift) and friction (drag) are zero, it may be concluded that for the example with the surface having an area density of texturing of 50 %, it is believed that 50 % of the friction would be removed from the textured area, while the area of the plateau areas would have to carry twice the amount of fluid film pressure. If this doubling of fluid film pressure would generate a doubling of friction for the plateau area surface, the total friction for the textured surface in this example would be the same as for a smooth surface. However, it has been found that this is not applicable for the example, rather it has been concluded that textures that encompass correct dimensioning may be used to decrease friction in the hydrodynamic lubrication regime, as further described hereinafter.

Since the correlation between contact pressure, the generation of hydrodynamic pressure and film thickness is non-linear, the film thickness between the plateaus of a textured surface and the mating surface will not be reduced to 50 % for a textured surface compared to a smooth surface. Comparing the average film thickness for a textured surface with the film thickness for a smooth surface envisioning that the other key parameters (sliding velocity and viscosity) are unchanged: since the area of the textures are defined to have an infinite film thickness, the textured areas are not included in the calculation of average film thickness for the two surfaces. This leaves the plateau area of the textured surface, if the film thickness is reduced by 50 % for the surface having a textured area, the friction would be the same for the textured surface and the smooth surface, but since the generation of hydrodynamic pressure and film thickness is nonlinear, the film thickness will not be reduced to 50 % on the plateaus of the textured surface. Thus, the average film thickness will be higher for the textured surface

(compared to the reference smooth surface), which is the cause of the hydrodynamic friction reduction.

Thus, the purpose of the exemplary embodiments as described herein is to decrease the friction losses in mechanical contacts. The purpose of the texture pattern can be described as optimising the area of a supporting surface in a mechanical design. In practice, this means removing the surface when it is not needed to generate the required supporting function, for this type of circumstances the redundant surface generates increased friction losses. By arranging and adding texture elements, as described in relation to the exemplary embodiments, film thickness separating the plateaus of the two mating surfaces (first sliding surface and second sliding surface) will decrease; however, the global (accounting for both the contact within and outside of texture elements) average film thickness between the two surfaces will increase, thus decreasing friction. Further, since texture elements decrease the plateau-to-plateau film thickness, it may not be beneficial to add a texture element on a part of a component for which the separating film thickness is low, e.g. a position of a bearing that experiences high or severe contact load, low sliding speed, low viscosity (in this case equals to high temperature) or increase or decrease of any other parameter that may increase the contact severity. For other positions on said bearing arrangement, or bearing member, it may be more beneficial to add texture elements on the surface. In addition, it should be readily appreciated that it may not be certain that all frictional losses are generated by increased contact load, there might very well be positions on the bearing member for which separating film thickness is relatively large, but said positions may experience significant friction losses due to a relatively high sliding speed between the two mating surfaces (first sliding surface and second sliding surface). For such circumstances texturing of the dimensioning as described in herein can have a significant beneficial effect on decreasing friction losses.

In view of the above, it has been observed that textures (texture pattern and texture elements) that encompass correct dimensioning may be used to decrease friction losses in the hydrodynamic lubrication regime. Accordingly, the present invention provides the technical effect of providing a hydrodynamic sliding bearing member which is capable of further reducing frictional losses in the hydrodynamic lubrication regime. In addition, the inventor has recognized that a significant part of the total friction losses in an internal combustion engine and its components are hydrodynamic (viscous) friction losses, and has observed that a reduction of the viscous losses is beneficial for reduction of fuel consumption.

Thus, by arranging the texture elements as mentioned hereinafter, the texture pattern facilitates a global increase in the fluid film between the sliding surfaces of the bearing member (or bearing arrangement) at the locations of the texture elements in order to minimize hydrodynamic (viscous) friction losses. In this context, the term "global" typically refers to an increase in oil film thickness between textures and plateau of opposing surface and oil film thickness between the plateaus of the two surfaces, i.e. it takes into account bot the contact within and outside the texture elements. For positions in which texture elements are introduced, the fluid film between the plateaus of the two surfaces might decrease. There are several different possibilities for arranging the texture elements of the texture pattern on the hydrodynamic sliding bearing member. These possibilities will now be discussed with reference to the example embodiments shown in figs. 4a - 4i, 5a - 5h, and 6a - 6b.

Figs. 4a to 4i schematically illustrate various example embodiments of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to the invention.

The expression "textured pattern" is expressly defined for purposes of the present invention as a regular, repeated pattern of distinct elements (typically in the form of depressions) such as depressions in the form of closed voids or grooves in surface 22, the substantial remainder of the surface 22 being defined by what shall be referred to here as one or more plateaus 46. Other, more irregular and generally more microscopic depressions may define other, more irregular and generally more microscopic plateaus as is well known in the art, however, depressions and plateaus of that type are not of substantial interest with respect to this aspect of the present invention. The textured pattern 40 can be provided in any suitable way. Typically, the texture elements are machined by a suitable method, such as by being machined via a milling, turning, or drilling operation, via chemical etching, water-jet cutting, abrasive blasting, or hydro- erosive grinding, or some combination of such operations.

Optimally, although not strictly necessary, each of the plateau areas of the first sliding surface of the hydrodynamic sliding bearing member may be provided with a machined roughness. As an example, the machined roughness may extend essentially along the entire axial length of the first sliding surface. By having plateau areas with a machined roughness, the generation of the hydrodynamic pressure may increase even if the mating surfaces, i.e. the first sliding surface and the second sliding surface, accidently contact each other during operation of the hydrodynamic sliding bearing arrangement. The machined roughness may for instance refer to arithmetical mean roughness or other parameters as defined in ISO 4287:1997 and similar standards.

Turning now to Fig. 4a, there is depicted an example embodiment of a

hydrodynamic sliding bearing member of a hydrodynamic sliding bearing arrangement, e.g. as described above in relation to the example embodiments shown in figs. 1 - 3. As illustrated in fig. 4a, and also in the other example embodiments in figs. 4b - 6b, the hydrodynamic sliding bearing member 20 has a first sliding surface 22 extending in a circumferential direction C and in an axial direction A. For the sake of facilitating the illustration of the example embodiments, the first sliding member is illustrated in a plane view (corresponding to the plane A-C) although the circumferential direction C refers to the circumference of the first sliding member. The first sliding surface here has a length L _A in the axial direction A and a length L _c in the circumferential direction C. Since the first sliding member typically has a circular cross sectional shape as seen in a plane perpendicular to the axial direction A, and illustrated in e.g. fig. 3, it is also readily understood that the length L _c of the first sliding bearing member 20 in the circumferential direction C typically corresponds to the circumference of the first sliding member as seen in the circumferential direction C. Thus, the length L _c of the first sliding bearing member 20 in the circumferential direction C may be defined by a closed circle of 360 degrees. Accordingly, the first sliding bearing member 20, as shown in fig. 4a and figs. 4b - 4i, extends from -180 degrees to 180 degrees (as seen in the circumferential direction). The first sliding member 20 also has a centre region defined by the centre line T. Further, the first sliding bearing member 20 may have an outer region 24, and an intermediate region in-between the centre region and the outer region, as seen in the axial direction A. It is to be noted that although the centre region in this example embodiment, and in other example embodiments herein, is illustrated by the centre line T, the centre region may in some examples correspond to a region of about 5 - 10 % of the length L _A , as seen in the axial direction A. Analogously, the outer region 24 may in some examples correspond to a region of about 0.1 - 10 % of the length L _A , as seen in the axial direction A. Still preferably, the extension of the outer region may be between 0.1 - 5 % of the total axial length of the sliding surface 22.

As mentioned above, the hydrodynamic sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to the second sliding surface 32 of a second sliding member 30 (not shown in fig. 4a) via a viscous fluid 60 to permit the hydrodynamic sliding bearing member (or bearing arrangement) to operate under hydrodynamic lubrication. That is, the first sliding surface 22 of the hydrodynamic sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to a second sliding surface 32 of a second sliding bearing member 30 via a viscous fluid 60 to permit the hydrodynamic sliding bearing arrangement to operate under hydrodynamic lubrication.

As illustrated in fig. 4a and also in figs. 4b to 4i, the first sliding surface 22 has opposite boundaries 26, 28, as seen in the axial direction A, and a texture pattern 40 comprising a plurality of texture elements 42. The opposite boundaries 26, 28 extend along the circumferential direction, respectively.

Moreover, an area density of the texture elements 42 decreases towards the axial boundaries 26, 28, as seen from a centre of the first sliding surface 22 in the axial direction A. That is, the texture elements are distributed so that the area density is regarded as decreasing towards each boundary. The centre of the first sliding surface here refers to the centre line T.

As is illustrated in the fig. 4a, the texture pattern is in this example embodiment distributed across essentially the entire length L _A and the length L _c .

By having a texture pattern distributed across essentially the entire length L _A and the length L _c , it becomes possible to further improve the entrapment of wear particles.

As will be described hereinafter, the area density of the texture elements can be decreased in several different ways. In some example embodiments, e.g. as shown in fig. 4a, the area density of the texture elements 42 decreases towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, by decreasing an axial length E _A and a circumferential length E _c of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

Alternatively, although not shown, the area density of the texture elements 42 may decrease towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, by only decreasing the axial length E _A of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

Alternatively, the area density of the texture elements 42 may decrease towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, by only decreasing the circumferential length E _c of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

The dimensions of each texture element may vary depending on the size, installation and use of the first sliding bearing member. However, the axial length E _A of the texture elements is typically at least above 300 μηι. Analogously, the circumferential length E _c of the texture elements is typically at least above 300 μηι.

Still preferably, the axial length E _A of the texture elements is between about 300- 10 000 μηι. Analogously, the circumferential length E _c of the texture elements is between about 300 - 10 000 μπι.

Purely as an example, the axial length E _A of the texture elements may decrease linearly from 10 000 μηι to 300 μηι, as seen from the centre of the first sliding surface to an outer boundary. Alternatively, the axial length E _A of the texture elements may decrease non-linearly from 10 000 μηι to 300 μηι, as seen from the centre of the first sliding surface to an outer boundary.

In another example, the axial length E _A of the texture elements may decrease linearly from 10 000 μηι to 1 000 μηι, as seen from the centre of the first sliding surface to an outer boundary. Alternatively, the axial length E _A of the texture elements may decrease non-linearly from 10 000 μηι to 1 000 μηι, as seen from the centre of the first sliding surface to an outer boundary.

In the example embodiment in fig. 4a, the circumferential length E _c of the texture elements for a given circumferential segment D (extending along the circumferential direction C) at a given axial distance from the centre of the first sliding surface is kept constant along the entire length L _c (the extension of the first sliding surface in the circumferential direction C). However, it is also conceivable that the circumferential length Ec of the texture elements for a given circumferential segment D (extending along the circumferential direction C) at a given axial distance from the centre of the first sliding surface is varied along the length L _c .

As may gleaned from fig. 4a, and also in other figs of the various example embodiments, a plurality of the texture elements of the texture pattern may typically, although not strictly necessary, be arranged in succession in a given area along the axial direction A. Analogously, a plurality of the texture elements of the texture pattern may typically, although not strictly necessary, be further arranged in succession in a given area along the circumferential direction C. To this end, a plurality of the texture elements of the texture pattern are arranged in a grid pattern extending in succession along the axial direction A and the circumferential direction C.

The distances between the texture elements in the axial direction A and the circumferential direction C may vary according to various conditions of the hydrodynamic sliding bearing member, and are typically selected in view of the shape, geometry, effect, and installation of the member. As an example, however, the texture elements are here spaced from one another along the axial direction A by at least 100 μηι. In addition, or alternatively, the texture elements are here spaced from one another along the circumferential direction C by at least 100 μηι. However, if the texture elements are in the form of squares (quadratic or rectangular), as seen in the axial and the circumferential directions, the distance between the texture elements may even be less than 100 μηι.

Optimally, although strictly not required, the texture pattern 40 here comprises a set of axial rows of texture elements 47 _A - 47 _N arranged in succession along the circumferential direction C, as shown in fig. 5a, which is a detailed view of e.g. the example embodiment in fig. 4a. Further, as illustrated, the texture elements 42 of at least one axial row 47b are offset from the texture elements of another axial row 47a as seen in the axial direction A so that a circumferential segment D of the first sliding surface 22 intersects at least one texture element in a substantial part of the first sliding surface.

In other words, the texture elements 42 are here arranged in succession in axial rows 47 _A - 47 _N along the circumferential direction C. Further, the texture elements 42 of at least one axial row, e.g. the axial row 47 _b , are offset from the texture elements of another axial row, e.g. the axial row 47 _a , as seen in the axial direction A so that a circumferential segment D of the first sliding surface 22 intersects at least one texture element in a substantial part of the first sliding surface. In this manner, the texture elements are arranged so that wear particles transported along the circumferential direction, due to the sliding direction of the hydrodynamic sliding bearing member, would be entrapped by at least one texture element independently on the path of the particle across the axial direction A.

Typically, as shown in fig. 5a, every second axial row 47 _B is offset with an equal distance from an adjacent axial row 47 _A, 47 _c .

The texturing may also be oriented in an angled manner, although not shown in the figures.

Thus, in one example embodiment, not shown, the texture pattern 40 may comprise a set of axial rows of texture elements 47 _A - 47 _N arranged in succession along the circumferential direction C, wherein each axial row of the texture elements of the set of axial rows of texture elements 47 _A - 47 _N is inclined with respect to a line parallel to the axial direction A. As an example, each axial row of the texture elements may be inclined by 70 degrees with respect to a line parallel to the axial direction A. However, it should be appreciated that the angle of inclination may vary depending on dimensions, installation and application. In some example embodiment, the angle of inclination may be between 5 - 80 degrees. Still preferably, in some example embodiment, the angle of inclination may be between 50 - 70 degrees.

One advantage with inclined axial rows of the texture elements is that the plateau area can be reduced as seen in the circumferential direction due to increased ratio of texture element area as seen in the circumferential direction, thus wear of the plateau areas may be reduced due to that wear particles transported along the sliding direction is subjected to bigger areas of texture elements compared to axial rows being parallel to the axial direction. Another advantage of this arrangement is that the possibility of entrapment of wear particles is significantly improved since there is no path that is not obstructed by a texture element for the particles to travel a significant distance in the circumferential direction of the first sliding surface. In other words, there is a least one texture element to entrap the wear particle independently on the current travelling path of the wear particles across the axial direction. Thus, it becomes possible to further increase the efficiency of entrapping wear particles.

The configuration of inclined axial rows of texture elements, as described above, is also applicable to the example embodiments shown in figs. 4b - 4i, and in other example embodiments.

The texturing may also consist of continuous grooves with its longest length extending in the axial or the circumferential direction. Hence, in one example embodiment, the texture element is a groove extending along the entire circumferential direction, as shown in fig. 4g or fig. 4h. However, it should be readily appreciated that in some example embodiments, the texture element in the form of a groove may only extend over a substantial length of the length of the sliding surface in the circumferential direction.

Thus, fig. 4g schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction C and in an axial direction A, in which the first sliding surface 20 has a texture pattern 40 comprising a plurality of texture elements according to example embodiments. This example embodiment is similar to the example embodiment as described in relation to fig. 4a besides that the texture elements 42 are provided in the form of grooves extending along the entire circumferential direction C. In addition, the texture elements are inclined with respect to the centre T.

The texture pattern in this example embodiment extends essentially along the entire axial direction A and the entire circumferential direction C.

In this example embodiment, the area density of the texture elements 42 decreases by decreasing the axial length E _A of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A. In addition, the circumferential length E _c essentially corresponds to the length of the sliding surface 22.

Moreover, in this example embodiment, the area density of the texture elements 42 decreases by decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A. As shown in fig. 4g, this further means that the distance E _D between two adjacent texture elements increases as seen from the centre of the first sliding surface 22 in the axial direction A. It should be readily appreciated that the area density of the texture elements 42 may in some examples only decrease by decreasing the quantity of texture elements towards the axial boundaries 26, 28 or by decreasing the axial length E _A of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

Alternatively, in another example embodiment (not shown), the area density of the texture elements 42 may decrease towards only the axial boundary 26, as seen from the centre of the first sliding surface 22 in the axial direction A. Hence, the other half of the first sliding surface is free from texture pattern (texture elements), i.e. the half of the surface defined by the region between the centre region T and the axial boundary 28. Further, as mentioned above, in some example embodiments (although not shown), the texture elements are provided in the form of grooves, each groove extending a substantial length in the circumferential direction of the first sliding surface. In this context, the term substantial length may refer to 30 - 100 % of the entire length of the first sliding surface in the circumferential direction. Still preferably, the term substantial length may refer to 50 - 90 % of the entire length of the first sliding surface in the circumferential direction

In addition, each texture element is inclined with respect to the centre T of the circumferential direction of the first sliding surface.

Besides these differences between the example embodiment in fig. 4g and the example embodiment in fig. 4a, the example embodiment in fig. 4g may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a.

Fig. 4h schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction C and in an axial direction A, in which the first sliding surface 20 has a texture pattern 40 comprising a plurality of texture elements according to example embodiments. This example embodiment is similar to the example embodiment as described in relation to fig. 4g besides that the texture elements 42 are provided in the form of two set of grooves extending along the entire circumferential direction C. Each set of the texture elements are inclined with respect to the centre T. In addition, each set of texture elements are arranged so that the texture elements from the first set of texture elements intersect the texture elements from the second set of the texture elements.

The texture pattern in this example embodiment extends essentially along the entire axial direction A and the entire circumferential direction C.

In this example embodiment, the area density of the texture elements 42 decreases by decreasing the axial length E _A of each texture element per unit area towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A. In addition, the circumferential length E _c essentially corresponds to the length of the sliding surface 22.

Moreover, in this example embodiment, the area density of the texture elements

42 decreases by decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A. As shown in fig. 4g, this further means that the distance E _D between two adjacent texture elements in the same set of texture elements increases as seen from the centre of the first sliding surface 22 in the axial direction A. Alternatively, in another example embodiment (not shown), the area density of the texture elements 42 may decrease towards only the axial boundaries 26, as seen from the centre of the first sliding surface 22 in the axial direction A. Hence, the other half of the first sliding surface is free from texture pattern (texture elements), i.e. the half of the surface defined by the region between the centre region T and the axial boundary 28.

Besides these differences between the example embodiment in fig. 4h and the example embodiment in fig. 4a and fig. 4g, the example embodiment in fig. 4h may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a and fig. 4g.

In addition, in the example embodiments as described in relation to fig. 4g and fig.

4h, and in the example embodiment that will be described in relation to fig. 4i, it is to be noted that the area density may vary along the circumferential direction C. For instance, the area density may be lower in some regions than in other regions as seen along the circumferential direction C.

According to another example embodiment, as illustrated in fig. 4i, the texture element is provided in the form of a texture element extending in circular manner about the circumferential direction C and along the axial direction A. That is, the texture element 42 is here an elongated continuous groove extending about the circumferential direction C and along the axial direction A as a spiral. In this manner, the length of the texture element can be greatly bigger than the circumferential length of the hydrodynamic sliding bearing member 20. One advantage with this type of texture element is that the texture pattern becomes less complicated to produce on the sliding surface 22.

Thus, with particular reference to fig. 2g and 4i, there is provided a hydrodynamic sliding bearing member 20 having a first sliding surface 22 extending in a circumferential direction C and in an axial direction A. The sliding bearing member 20 is configured for being slidably arranged in the circumferential direction C relative to a second sliding surface of a second sliding member (although not shown in fig. 2g and fig. 4i) via a viscous fluid to permit the hydrodynamic sliding bearing member 20 to operate under hydrodynamic lubrication. The first sliding surface 22 has opposite boundaries 26, 28, as seen in the axial direction A. In addition, the texture pattern 40 here comprises one texture element 42, wherein an area density of the texture element 42 decreases towards the axial boundaries 26, 28, as seen from a centre of the first sliding surface 22 in the axial direction A.

Further, as shown in fig. 2g, the texture element here resembles a helix or spiral, i.e. a curve in the tree-dimensional space, extending around the circumferential length of the sliding surface 22 and towards the axial boundaries 26, 28. The spiral-shaped texture element is shown in fig. 4i, which shows the first sliding surface in an unfolded

configuration. Thus, in a two-dimensional view, as shown in fig. 4i, the texture pattern including one texture element here resembles the texture pattern in fig. 4g, although it should be understood that the texture element is in this example embodiment one single continuous groove. In other words, the texture element is here illustrated as a straight groove on a plane (surface 22), and when that plane is wrapped around a cylindrical surface of any kind, especially a right circular cylinder, the texture element resembles the shape of a curve of a screw, as shown in fig. 2g.

Accordingly, there is provided hydrodynamic sliding bearing member 20, as e.g. described above, wherein the texture element 42 is an elongated continuous groove extending about the circumferential direction C and along the axial direction A as a spiral. The groove typically has a number of revolutions, with the distance between them increasing as the groove approaches the axial boundary.

Further, as shown in fig. 4i, in this example embodiment, the area density of the texture elements 42 decreases by linearly or non-linearly increasing the angle of the inclination of the texture element. Typically, the angle of inclination may sometimes also be denoted the pitch of the texture element, i.e. the width of one complete turn of the texture element around the circumferential direction.

In other words, the distance E _D between two points of texture elements at a given circumferential length increases along the axial direction A, as seen from the centre of the first sliding surface 22 in the axial direction A.

An advantage of this arrangement is that the possibility of entrapment of wear particles is significantly improved since there is no path that is not obstructed by a texture element for the particles to travel a significant distance in the circumferential direction of the first sliding surface. In other words, there is a least one texture element to entrap the wear particle independently on the current travelling path of the wear particles across the axial direction. Thus, it becomes possible to further increase the efficiency of entrapping wear particles.

Besides the differences between the example embodiment in fig. 4i and the example embodiments in e.g. fig. 4a to 4h, the example embodiment in fig. 4i may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a.

Typically, in all example embodiments as described herein, the depth of the texture elements forming the textured pattern also decreases towards at least one of the axial boundaries, as seen from the centre of the first sliding surface 22 in the axial direction A. Alternatively, the depth of the texture elements forming the textured pattern may be kept constant along the axial direction A. The depth of the texture elements is further described and illustrated in figs. 6a and 6b hereinafter. Figs. 6a and 6b illustrate a cross sectional view along the cross section Q-Q in e.g. fig. 4f, and as seen in the axial direction A and the radial direction R.

In the example embodiment shown in fig. 4a, the texture pattern extends essentially along the entire axial direction A and the circumferential direction C of the hydrodynamic sliding bearing member 20. That is, the texture elements of the texture pattern are distributed essentially along the entire first sliding surface 22. In this manner, the effects of the texture pattern as described above can be utilized to decrease hydrodynamic frictions losses over essentially the entire first sliding surface 22.

In another example embodiment (although not shown), the distribution of the texture pattern can be limited to the main regions of the first sliding surface, i.e. the centre region and an intermediate region (i.e. the intermediate region refers to a region located between the centre region and an outer region). In other words, there is provided a first sliding surface 22, wherein an outer region 24 of the first sliding surface 22 adjacent an axial boundary 26, 28 is free from texture elements. Throughout the description, the outer region 24 refers to a region extending along the circumferential direction C, an in the axial direction A. The outer region is arranged adjacent the axial boundary 26. In addition, or alternatively, the outer region is arranged adjacent the axial boundary 28.

In this manner, it becomes possible to essentially avoid or further reduce the risk of fluid lubrication leakage compared to if the axial texturing area density was constant. Since the effect from axial leakage is typically largest at the boundaries, it has been observed that in some example embodiments, a distance or region of zero texture elements around the axial boundary may counteract the leakage in an efficient manner. The extension of the outer region may be between 0.1 - 10 % of the total axial length of the sliding surface 22. Still preferably, the extension of the outer region may be between 0.1 - 5 % of the total axial length of the sliding surface 22.

Fig. 4b schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according example embodiments. This example embodiment is similar to the example embodiment as described in relation to fig. 4a besides that the distribution of the texture pattern 40 is limited along the circumferential direction C. As shown in fig. 4b, the texture pattern in this example embodiment extends essentially along the entire axial direction A, but only a part in the circumferential direction C of the hydrodynamic sliding bearing member 20. That is, the texture elements of the texture pattern are distributed essentially along the entire first sliding surface 22, while the texture elements of the texture pattern are distributed essentially between - 60 degrees to 60 degrees along the circumferential direction C of the first sliding surface 22.

Accordingly, the first sliding surface 22 is free from texture element in a region that amounts to 120 degrees of the extension of the first sliding surface, which typically corresponds to 30 - 35 % of the first sliding surface, as seen in the circumferential direction C. In this manner, the hydrodynamic sliding bearing member is configured to provide a region that better withstands points of high contact pressure since the first sliding surface has an area of no texture pattern, thus allowing the surface to distribute the force at this non-textured area of the first sliding surface. To this end, the first sliding surface is configured according to contact pressure.

Besides this difference between the example embodiment in fig. 4b and the example embodiment in fig. 4a, the example embodiment in fig. 4b may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a.

Fig. 4c schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to example embodiments. This example embodiment is similar to the example embodiment as described in relation to fig. 4a and fig. 4b besides that the distribution of the texture pattern 40 is limited along the axial direction A (and in the circumferential direction C).

As shown in fig. 4c, the texture pattern in this example embodiment extends only in one half of the surface as seen in the entire axial direction A, and only a part in the circumferential direction C of the hydrodynamic sliding bearing member 20. Hence, the texture elements 42 are only arranged from the centre region T to one of the axial boundaries 26, as seen in the axial direction A, while the other half of the first sliding surface defined by a region between the centre region T and the axial boundary 28 is free from texture pattern (texture elements).

That is, in this example embodiments, the area density of the texture elements 42 decreases towards only one of the axial boundaries, as seen from the centre of the first sliding surface 22 in the axial direction A. In addition, the texture elements of the texture pattern are distributed essentially between - 60 degrees to 60 degrees along the circumferential direction C of the first sliding surface 22. Accordingly, the first sliding surface 22 is also free from texture element in a region that amounts to 120 degrees of the extension of the first sliding surface, which typically corresponds to 30 - 35 % of the first sliding surface, as seen in the circumferential direction C.

It is to be noted that in another example embodiment (not shown), the texture pattern may be arranged essentially along the entire extension of the surface as seen in the circumferential direction C, but only arranged from the centre region T to one of the axial boundaries 26, as seen in the axial direction A. Thus, the other half of the first sliding surface defined by the region between the centre region T and the axial boundary 28 is free from texture pattern (texture elements).

Besides these differences between the example embodiment in fig. 4c and the example embodiment in fig. 4a, the example embodiment in fig. 4c may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a, and/or in fig. 4b.

Turning now to fig. 4d, there is depicted an example embodiment in which the area density of the texture elements 42 decreases towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, by decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A. In this example embodiment, the area density of the texture elements decreases towards both of the axial boundaries, as seen from the centre of the first sliding surface 22 in the axial direction A.

It is to be noted that the provision decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, may typically also mean that the distance, in the axial direction A, between axially adjacent texture elements increases towards the axial boundaries 26, 28.

Hence, fig. 4d schematically illustrates a hydrodynamic sliding bearing member 20 having a first sliding surface 22 extending in the circumferential direction C and in the axial direction A, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to example embodiments. This example embodiment is essentially similar to the example embodiment as described in relation to fig. 4a besides that area density of the texture elements 42 decreases by decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

Alternatively, in another example embodiment (not shown), the area density of the texture elements 42 decreases towards only the axial boundaries 26, as seen from the centre of the first sliding surface 22 in the axial direction A by decreasing the quantity of texture elements towards only the axial boundaries 26, as seen from the centre of the first sliding surface 22 in the axial direction A. Hence, the other half of the first sliding surface is free from texture pattern (texture elements), i.e. the half of the surface defined by the region between the centre region T and the axial boundary 28.

As may be gleaned from fig. 4d, the size and shape of the texture elements are here essentially kept constant across the axial direction A and the circumferential direction C, except for the area in the centre of the sliding surface which is zero degrees in said figure. However, the size and shape may vary across any one of the axial direction A and the circumferential direction C.

Besides these differences between the example embodiment in fig. 4d and the example embodiment in fig. 4a, the example embodiment in fig. 4d may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a.

As an example, as mentioned in the example embodiment described in relation to fig. 4a, the texture pattern may optimally, although not strictly required, comprise a set of axial rows of texture elements 47 _A - 47 _N arranged in succession along the circumferential direction C. Further, as illustrated, the texture elements 42 of at least one axial row 47b are offset from the texture elements of another axial row 47a as seen in the axial direction A so that a circumferential segment D of the first sliding surface 22 intersects at least one texture element in a substantial part of the first sliding surface.

Fig. 4e schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in a circumferential direction and in an axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to example embodiments. This example embodiment is similar to the example embodiment as described in relation to fig. 4d besides that the distribution of the texture pattern 40 is limited along the circumferential direction C.

As shown in fig. 4e, the texture pattern in this example embodiment extends essentially along the entire axial direction A, but only a part in the circumferential direction C of the hydrodynamic sliding bearing member 20. That is, the texture elements of the texture pattern are distributed essentially along the entire first sliding surface 22, while the texture elements of the texture pattern are distributed essentially between - 60 degrees to 60 degrees along the circumferential direction C of the first sliding surface 22.

Accordingly, the first sliding surface 22 is free from texture element in a region that amounts to 120 degrees of the extension of the first sliding surface, which typically corresponds to 30 - 35 % of the first sliding surface, as seen in the circumferential direction C. In this manner, the hydrodynamic sliding bearing member is configured to provide a region that better withstands points of high severity, e.g. high contact pressure since the first sliding surface has an area of no texture pattern, thus allowing the surface to distribute the force at this non-textured area of the first sliding surface. To this end, the first sliding surface may be better configured according to contact pressure.

Besides this difference between the example embodiment in fig. 4e and the example embodiment in fig. 4d, the example embodiment in fig. 4e may incorporate any one of the features and/or effects as mentioned in relation to fig. 4d, and/or fig. 4a.

Fig. 4f schematically illustrates another example embodiment of a hydrodynamic sliding bearing member having a first sliding surface extending in the circumferential direction and in the axial direction, in which the first sliding surface has a texture pattern comprising a plurality of texture elements according to example embodiments. This example embodiment is essentially a combination of the texture pattern in the example embodiment in fig. 4a and the example embodiment in fig. 4d. In other words, as shown in fig. 4f, there is depicted an example embodiment in which the area density of the texture elements 42 decreases towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, by both by decreasing at least one of an axial length E _A and circumferential length E _c of each texture element per unit area towards said axial boundary 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A, and by decreasing the quantity of texture elements towards the axial boundaries 26, 28, as seen from the centre of the first sliding surface 22 in the axial direction A.

It should be readily conceivable that the distribution of the texture pattern across the axial direction A and the circumferential direction C may vary as mentioned above with respect to the figures 4b, 4c and 4e as well.

Besides these differences between the example embodiment in fig. 4f and the example embodiment in fig. 4a and/or fig. 4d, the example embodiment in fig. 4f may incorporate any one of the features and/or effects as mentioned in relation to fig. 4a and/or fig. 4d.

It is to be noted that the example embodiments of the hydrodynamic sliding bearing member, as described above in relation to figs. 4a - 4i, may be installed in any one of constructions described above. That is, the hydrodynamic sliding bearing member may be a part of a journal bearing, a main bearing, a connecting rod, a connecting rod bearing, a hydrodynamic sliding bearing arrangement or the like. In addition, the hydrodynamic sliding bearing member 20 may contribute to any one of the functions and the advantages as described with respect to the example embodiment in figs. 1 to 3.

Turning now to fig. 5a, there is depicted a detailed view of the example embodiment of the hydrodynamic sliding bearing member in fig. 4a. However, it should be 5 readily understood that the details, functions and effects described hereinafter in relation to fig. 5a, may likewise be applicable to the other example embodiments, e.g. the examples described in relation to figs. 4b - 4i.

As shown in fig. 5a, which is a part of the first sliding surface 21 between the centre of the surface, indicated with centre line T, and the axial boundary 26, the area

10 density of the texture elements 42 decreases towards the axial boundary 26, as seen from the centre of the first sliding surface 22 in the axial direction A, for instance by decreasing the axial length E _A and the circumferential length E _c of each texture element per unit area towards the axial boundary 26, as seen from the centre of the first sliding surface 22 in the axial direction A. In addition, in this example embodiment, the circumferential length E _c of

15 the texture elements for a given circumferential segment D (extending along the

circumferential direction C) at a given axial distance from the centre of the first sliding surface is kept constant along the entire length L _c (the extension of the first sliding surface in the circumferential direction C). However, it is also conceivable that the circumferential length E _c of the texture elements for a given circumferential segment D (extending along

20 the circumferential direction C) at a given axial distance from the centre of the first sliding surface is varied along the length L _c .

In addition, fig. 5a, shows an example of a texture pattern 40, which here comprises a set of axial rows of texture elements 47 _A - 47 _N arranged in succession along the circumferential direction C. Further, the texture elements 42 of every second axial row

25 47b, 47d etc. are offset from the texture elements of the axial row 47a, as seen in the axial direction A. In this manner, a circumferential segment D of the first sliding surface 22 intersects at least one texture element in a substantial part of the first sliding surface. In this context of the present invention, a circumferential segment D refers to a segment of the first sliding surface extending essentially along the entire circumferential direction C.

30 Furthermore, the term "substantial" here typically refers to the entire area or the first

sliding surface. That is, the term substantial may refer to 100 % of the first sliding surface. However, it should be conceivable that in some example embodiments, the term

"substantial" may refer to the area of the first sliding surface besides the outer region 24 of the first sliding surface. That is, the term substantial may here refer to 95 - 100 % of the

35 first sliding surface. Since the sliding surface comprises a texture pattern, there are also some areas on the sliding surface that are non-textured, as further illustrated in fig. 5a,. This type of non-textured area may typically be provided in the form of an essentially smooth surface area. An area between two adjacent texture elements forms a plateau area 46. As an example, the area of the plateau area is between about 20-95 percent of a total area of the first sliding surface. Accordingly, a textured area of the texture pattern may be between about 5-80 percent of a total area of the first sliding surface. In this manner, it becomes possible to provide a sufficiently large area with zero friction and an improved utilization of the non-linear behaviour of film thickness and fluid film pressure to generate a substantially large relative average film thickness.

In one example embodiment, the textured area of the texture pattern is between about 20-50 percent of a total area of the first sliding surface

As mentioned above, the depth of the texture elements in the example

embodiments as described in relation to figs. 4a to 4i, may either be varied along the axial direction A or kept constant along the axial direction A. This is illustrated in figs. 6a to 6b, which depict cross sectional views of various example embodiments of an inner first sliding surface of a hydrodynamic sliding bearing member according to any one of the example embodiments described above, and as seen in the axial direction A and the radial direction R. For sake of understanding, figs. 6a and 6b may reflect a cross sectional view along the cross section Q-Q in e.g. fig. 4f.

The depth of a texture element is here denoted by the reference E _R , since the depth typically refers to the extension of the texture element 42 in the radial direction of the first sliding bearing member 22.

In some example embodiments, it is contemplated that hydrodynamic friction may further be efficiently reduced by decreasing both the area density and the texture depth as seen from the centre of the first sliding surface 22. This is shown in fig. 6a, in which a depth E _R of the texture elements 42 forming the textured pattern 40 decreases towards at least one of the axial boundaries, as seen from the centre of the first sliding surface 22 in the axial direction A.

By the provision that the depth of the texture elements forming the textured pattern decreases towards at least one of the axial boundaries, it becomes possible to further reduce the risk of having fluid leakage at the axial boundary. This is due to that an increased depth will increase the leakage at the axial boundary, thus decreasing the hydrodynamic pressure and thus increasing friction. The depth of the texture elements and the relationship between a texture element at the centre of the first sliding surface and a texture element at the axial boundary is typically selected in view of the dimensions and shapes of the sliding bearing member and the texture elements as well as type of texture pattern. However, without being bound by any theory, it is believed that the texture elements should be sufficiently deep so that the viscous film shear force within the texture elements is negligible, texture boundary effects excluded. Negligible viscous film shear force is here defined as that the viscous film shear force in texture elements, texture boundary effects not included, should be less than 5 % compared to the viscous film shear force acting between the plateaus of the two surfaces. By having texture elements with a negligible contribution to the viscous film shear force, it will also be possible to provide texture elements having a negligible contribution to the hydrodynamic pressure build-up. Since a negligible contribution to the hydrodynamic pressure build-up is obtained, it may be appreciated that the depth of the texture elements can be selected appropriately as long as the above mentioned viscous film thickness criteria is meet.

The depth of the texture elements should typically be above 10 μηι. However, a depth of the texture elements may ordinarily be between substantially 20-200 μηι. In some example embodiments, a minimum depth of the texture elements may be substantially equal to 35 μηι. While it is presently believed that providing texture elements or depressions with depths less than 35 μηι, such as around 20 μηι, may, in some circumstances provide beneficial results, in some circumstances textures or depressions with depths around 30 μηι may actually increase friction, and it is presently believed that texture elements or depressions of at least 35 μηι and, likely, substantially greater than 35 μηι will provide most beneficial results.

Thus, purely as an example, the hydrodynamic sliding bearing member comprises a texture pattern having a plurality of the texture elements, wherein the depth of the texture elements is varied from 200 μηι at the centre of the first sliding surface 22, as seen in the axial direction A, to 20 μηι at the axial boundary of the first sliding surface.

In another example, as shown in e.g. fig. 6b, the depth E _R of the texture elements 42 are maintained constant, e.g. at a depth of 35 μηι.

The example embodiments of the hydrodynamic sliding bearing member, as is described in relation to figs. 4a - 6b, may be installed in any one of constructions described above. That is, the hydrodynamic sliding bearing member may be a part of a journal bearing, a main bearing, a connecting rod, a connecting rod bearing, a

hydrodynamic sliding bearing arrangement or the like. In addition, the hydrodynamic sliding bearing member 20 may contribute to the functions and the advantages as described with respect to the example embodiment in figs. 1 to 3. It should also be readily appreciated that in all example embodiments as illustrated in the figures herein, and in other example embodiments of the present invention, the hydrodynamic first sliding member is arranged on the shaft, i.e. the inner sliding member of the hydrodynamic sliding bearing arrangement. Thus, the texture pattern 40 comprising the plurality of texture elements according to the example embodiments may be arranged on the journal shaft or the like. That is, the texture pattern 40 comprising the plurality of texture elements may be arranged on the outer circumferential surface of the journal shaft, which is arranged inside of the inner circumferential surface of the other bearing member.

Accordingly, in some example embodiments (although not shown), the first sliding surface 22 of the first sliding member 20 may refer to an outer circumferential surface arranged within a second sliding member. Thus, the outer circumferential surface (here first sliding surface 22) is allowed to slide about the inner circumferential surface (the second sliding surface of the second sliding member) via the viscous fluid 60 upon rotation of the first sliding member 20 relative to the second sliding member 30.

In some example embodiments, the texture pattern 40 may be arranged on both the first sliding member 20 and the second sliding member 30. This type of example embodiment may include any one of the features and functions as described above in relation to the figures. Hence, a bearing arrangement may be provided which includes a first sliding member 20 having a texture pattern according to the example embodiments as described herein and a second sliding member 30 having a texture pattern according to the example embodiments as described herein.

In all example embodiments herein, it should be readily appreciated that the by the provision "upon rotation of the first sliding member 20 relative to the second sliding member 30" may refer to that the first sliding member rotates, while the second sliding member is stationary. Alternatively, the provision "upon rotation of the first sliding member 20 relative to the second sliding member 30" may refer to that the first sliding member is stationary, while the second sliding member rotates. Alternatively, the provision "upon rotation of the first sliding member 20 relative to the second sliding member 30" may refer to that the first sliding member rotates and the second sliding member rotates.

A further benefit of providing the textured pattern according to the example embodiments herein is that wear on the surfaces 22 and 32 can be reduced because debris can be retained in the textured pattern (texture elements). The surface texturing of the surface(s) could, however, in some circumstances, increase the wear levels due to the fact that there will be less fluid film (and probably more mechanical contact) separating the surfaces. However, it is also possible that the wear levels could decrease. A significant wear mechanism for components as mentioned and described herein is three- body-abrasion. It is expected that sufficiently deep elements, as mentioned herein, could trap wear particles and decrease wear of the surfaces 22 and 32.

In all example embodiments as described herein, and in other example

embodiments, the texture elements may each have one of a substantially circular, oval, or elliptical shape. It will be appreciated, however, that the texture elements can have other shapes, such as triangular, grooves, square, rectangular, diamond, etc. In addition, texture element shapes may include open or closed voids. That is, any one of the texture elements may have a cross-sectional shape in the form of a square, rectangle, circle, or ellipse.

With respect to the shape of the texture element, as seen in the axial direction A and in the circumferential direction C, the shape may typically resemble an ellipse, as shown in previous figures. As mentioned above, the texture element has a length E _A in the axial direction A and a length E _c in the circumferential direction C (see fig. 5a).

Fig. 5b is a top view of an example embodiment of a texture element of the texture pattern according to the invention, e.g. a texture element as illustrated in fig. 5a. In this example, the cross sectional shape is essentially an ellipse, extending in the axial direction A and in the circumferential direction C.

Before turning to some examples on the shape of the texture element, it should be noted that the sliding direction S here refers to the rotational direction of the second sliding bearing member 30 typically being arranged inside the circumference of the hydrodynamic (first) sliding bearing member 20. In other words, during a working mode of the hydrodynamic sliding bearing member 20 and the hydrodynamic sliding bearing arrangement 10, for instance when the hydrodynamic sliding bearing member 20 is part of a main bearing and the second sliding bearing member 30 is the journal shaft (e.g. the crank shaft 18 - as shown in e.g. fig. 2a), the second sliding bearing member 30 (journal shaft) is typically configured to rotate inside the hydrodynamic (first) sliding bearing member 20. In other words, the hydrodynamic sliding bearing member 20 is in these example embodiments considered essentially stationary, while the second sliding bearing member 30 slides in the sliding direction S inside the hydrodynamic (first) sliding bearing member 20, thus the hydrodynamic (first) sliding bearing member 20 is slidably arranged relative the second sliding bearing member 30. As mentioned above, the sliding direction S thus here corresponds to the circumferential direction C. That is, the sliding direction S here refers to the rotational direction of the second sliding bearing member 30. Typically, the second sliding bearing member 30 is arranged inside the circumference of the hydrodynamic (first) sliding bearing member 20. Hence, the sliding direction S here refers to the rotational direction of the second sliding bearing member 30, said second sliding bearing member 30 being slidably arranged inside the circumference of the hydrodynamic (first) sliding bearing member 20. Since, the circumferential direction C typically corresponds to the sliding direction S of the hydrodynamic sliding bearing member 30 (and the sliding surface 32), it is to be noted that in all example embodiments, the cross sectional shape of the texture element in the circumferential direction C and in the radial direction R may here also refer to the cross sectional shape of the texture element 42, as seen in the sliding direction S and the radial direction R. Further, regarding the cross sectional shape of the texture element in the circumferential direction C and the radial direction R, it is to be noted that several different shapes are conceivable depending on the effect, design, installation and working condition of the hydrodynamic sliding bearing member and the hydrodynamic sliding bearing arrangement. Some example

embodiments are described in relation to figs. 5c - 5g. These examples can reflect a cross section along any one of the cross section views J-J, M-M and l-l.

Typically, in all example embodiments, the texture element may be defined by a leading region 54 and the trailing region 50. Accordingly, the texture element may have a leading region and a trailing region with respect to the sliding direction of the opposite sliding bearing member, e.g. the second sliding bearing member 30. The leading region may herein be defined by the leading edge 54 (sometimes also referred to as the leading surface). The trailing region may e.g. correspond to the region 50 in the example embodiments as shown in fig. 5b - 5h. The trailing region 50 may typically constitute 30 % or less of the total area of the texture element as seen in the axial direction A and the circumferential direction C. Still preferably, the trailing region 50 may typically constitute 20 % or less of the total area of the texture element as seen in the axial direction A and the circumferential direction C. Still preferably, the trailing region 50 may typically constitute 10 % or less of the total area of texture element as seen in the axial direction A and the circumferential direction C. It should be conceivable that the trailing region is at least above 0 % of the total area of the texture element as seen in the axial direction A and the circumferential direction C. In addition, the texture element is here defined by a circumferential centre line Z (as shown in e.g. fig. 5b). Fig. 5b also show a plurality of cross section views J-J, M-M and l-l, which may have a cross sectional shape along the circumferential direction C and the radial direction R according to any one of the example embodiments described in relation to 5c - 5g.

Regarding the cross sectional shape of the texture element in the circumferential direction C and the radial direction R, it is to be noted that several different shapes are conceivable depending on the effect, design, installation and working condition of the hydrodynamic sliding bearing member and the hydrodynamic sliding bearing

arrangement. Some example embodiments will now be described in relation to Figs. 5c - 5g. These examples can reflect the cross section along any one of the cross section views J-J, M-M and l-l.

Fig. 5c shows one cross sectional view of an example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along the circumferential direction C and the radial direction R. In this example embodiment, the cross section shape of the texture element 42, as seen along the circumferential direction C and the radial direction R is a rectangle. Since the circumferential direction C typically refers to the sliding direction S of the hydrodynamic sliding bearing member 20 (and the sliding surface 22), the cross sectional shape may here also refer to the cross sectional shape of the texture element 42, as seen in the sliding direction S and the radial direction R. The texture element 42 is here formed by two opposite surfaces 52 and 54 projecting inwardly from the sliding surface S towards the radial direction R and essentially arranged perpendicular to the circumferential direction C of the sliding surface 22 and by a bottom texture element surface 56 extending between the opposite surfaces 52 and 54. The bottom texture element surface 56 is further essentially perpendicular arranged to the surfaces 52 and 54. By having opposite surfaces 52 and 54 arranged perpendicular to the sliding surface 22, the opposite surfaces, respectively, forms essentially right angles with the sliding surface 22. Thus, one of the surface is a trailing side wall 52 and the other surface is a leading side wall 54, as seen in the sliding direction S (typically corresponding to the circumferential direction C). By having a texture element with a leading surface a trailing surface that each forms a right angle with respect to the sliding surface, boundary effects are minimized. Thus, the friction within the texture will require a smaller sliding distance to reduce shear losses compared to if said angle would have been smaller. This may typically provide the additional effect that viscous film shear losses can be kept to at a minimum level. In this context, it should be readily appreciated that completely straight angles may be difficult to manufacture, and it is thus conceivable that the angles may refer to essentially straight angles considering the limitations of the selected machining method. However, this type of cross sectional shape is typically incapable of providing an increase, or merely a small increase, of the hydrodynamic pressure due to the sharp angle between the trailing surface of the texture element and the sliding surface of the first sliding bearing member.

In order to gain an increase in the hydrodynamic pressure generation at the trailing surface, it has been observed that the trailing surface should be angled, or inclined, with respect to the sliding surface of the bearing member, as is illustrated in fig. 5d. Thus, fig. 5d is a cross sectional view of another example embodiment of the texture element in fig. 5b. In this example embodiment, the trailing surface 52 is angled with an angle a _B with respect to the sliding surface 22, or with respect to a line perpendicular to the sliding surface 22. Typically, the value of the angle a _B is essentially 90 degrees. However, in some example embodiments, although not shown, the angle a _B may be between 45 - 90 degrees. Further, the trailing surface 52 here extends, in an inclined manner with the angle a _B , from the sliding surface 22 to the bottom surface of the texture element.

However, it has also been observed that this type of cross sectional shape of having an inclined trailing surface extending entirely from the first sliding surface 22 to the bottom surface 56 of the texture element may be detrimental to the viscous film shear losses, i.e. it may typically lead to an increase in viscous film shear losses. This is partly due to that the length of the bottom surface of the texture element, as seen in the circumferential direction, is shorter compared to an essential rectangular shaped cross section, as shown in fig. 5c, since the extension of the texture element in the

circumferential direction C (here sliding direction S) for the rectangular shaped cross section is defined by the length of the bottom surface of the texture element, i.e.

corresponds to the entire length E _c in fig. 5c, while the circumferential length of the texture element with an inclined trailing surface is defined by the length of the bottom surface of the texture element and the circumferential extension of the inclined trailing surface, as may be gleaned from fig. 5d. Thus, the extension of the bottom surface of the texture element having an inclined trailing surface is shorter for the two types of cross sectional shapes (fig. 5c and fig. 5d) provided that they have similar lengths along the

circumferential direction, i.e. circumferential length E _c . Also, by having an inclined trailing surface with an angle a _b extending from the bottom surface of the texture element gives a relatively high angle, considering the proposed depth of the texture. Steep angles are not optimal at generating hydrodynamic pressure; this is addressed with the texture design in fig. 5e.

Based on the effects of these two possible examples of cross sectional shapes of the texture element design, it has been observed that the shape may further be improved in order to both gain an increase in the hydrodynamic pressure generation, while reducing the viscous film shear losses and enabling an increased fluid film thickness thus decreasing the likelihood of material-to-material friction and subsequent increase in contact friction and wear.

One example is illustrated by fig. 5b together with fig. 5e and 5h. Fig. 5b is a top view of the example embodiment of the texture element of the texture pattern, e.g. a texture element as illustrated in fig. 5a, in which the shape of the texture element is illustrated along the axial direction A and the circumferential direction C. Fig. 5e is a cross sectional view of the example embodiment of the texture element, in which the shape of the texture element is illustrated along the circumferential direction C and the radial direction R, while fig. 5h is a perspective view of the example embodiment of the texture element of the texture pattern.

As is shown in fig. 5b in conjunction with fig. 5e and fig. 5h, there is provided a hydrodynamic sliding bearing member 20 having the first sliding surface 22 extending in the circumferential direction C and in the axial direction A, and configured for being slidably arranged in the circumferential direction C relative to a second sliding surface 32 of a second sliding member 30 via a viscous fluid to permit the hydrodynamic sliding bearing member to operate under hydrodynamic lubrication. The first sliding surface 20 has a texture pattern 40, which comprises at least one texture element 42. The texture element 42 has a trailing region 50 defined by a trailing surface 52 extending from the first sliding surface 22 to the bottom surface 56 of the texture element 42. Moreover, a first section 59 of the trailing surface 52 is adapted to define a converging gap G with a sliding surface 32 of a second sliding member and extends a distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R .

Although not shown in figs 5b, 5e and 5h, the first sliding surface has, as described in relation to figs. 4a - 4i, opposite boundaries 26, 28, as seen in the axial direction A. Further an area density of the texture element 42 decreases towards at least one of the axial boundaries 26, 28, as seen from a centre of the first sliding surface 22 in the axial direction A, which has been previously described in relation to any one of figs. 4a - 4i.

It should also be readily appreciated that the first sliding surface, as illustrated in figs. 5b - 5b herein, typically refers to the plateau area 46 of the first sliding surface 22.

By the provision that the first section 59 of the trailing surface 52 is adapted to define the converging gap G with the sliding surface 32 of the second sliding member and that the first section 59 extends a distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R , there is provided a texture element which is capable of increasing the hydrodynamic pressure generation thus increasing the fluid film thickness separating the two active surfaces (first sliding surface and second sliding surface), thus reducing the viscous film shear losses. This type of configuration of the texture element shape further contributes to maintain the contact in the hydrodynamic lubrication regime, while minimizing any possible contribution from boundary friction.

In other words, by having the first section 59 configured to form a converging gap G with the second sliding surface 32 (indicated e.g. by sliding member 30 in fig. 5e) during operation of the bearing arrangement, it becomes possible to gain an increase in the hydrodynamic pressure generation at the trailing region 50. This advantage is also provided by the example embodiments as described in relation to figs. 5f and 5g.

In this context, the term "converging gap" refers to the geometry of the first section of the trailing surface (trailing region) of the texture element, which upon a sliding motion of the first sliding surface relative to the second sliding surface generates a hydrodynamic pressure in the viscous fluid film in conjunction with the opposite second sliding surface of the second sliding member. In this manner, the example embodiments of the invention provides a texture element shape having an optimized surface for generating a hydrodynamic pressure in a viscous fluid film confined between the sliding surfaces of the bearing arrangement, i.e. between two solid surfaces with a relative sliding motion.

Accordingly, the example embodiments are configured to utilize the hydrodynamic effect of the viscous fluid in the converging gap as defined by the first section in conjunction with the second sliding surface in order to minimize the frictional forces between the first sliding bearing member and the second sliding bearing member.

In addition, it should be readily appreciated that the first section 50 of the trailing surface forms the converging gap G with the sliding surface 32 of the second sliding member during operation, i.e. when the first sliding surface is sliding relative to the second sliding surface so as to operate under hydrodynamic lubrication. The first sliding surface is sliding relative to the second sliding surface due to a rotation of the second sliding bearing member 30 relative to the first sliding bearing member 20.

In other words, the first section of the trailing surface is configured to form a converging gap with the sliding surface of the second sliding member during operation of the hydrodynamic sliding bearing member. That is, the first section of the trailing surface is configured to form a converging gap with the sliding surface of the second sliding member during operation of the hydrodynamic sliding bearing arrangement.

To this end, the first section of the trailing surface forms the converging gap with the sliding surface of a second sliding member when the first sliding surface and the second sliding surface are sliding relative to each other in the circumferential direction C. Typically, the first section of the trailing surface forms the converging gap with the sliding surface of a second sliding member when the first sliding surface and the second sliding surface are sliding relative to each other in the circumferential direction C due to a rotation of the second sliding member relative to the first sliding bearing member. As mentioned above, the converging gap further extends the distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R .

Turning now again to fig. 5e and fig. 5h, which show a cross-sectional view and a perspective view of the texture element shape, respectively, there is provided a texture element 42 having the trailing region 50, as seen in the sliding direction S along the circumferential direction C, wherein the trailing region 50 has the trailing surface 52 defined by the first section 59 and a second section 58. Moreover, the first section of the trailing surface is adapted to define the converging gap G with the sliding surface of a second sliding member (not shown in figs. 5e and 5h). In addition, the first section 59 extends a distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R .

However, it should be readily appreciated that the distance E _RB may even be smaller than 50% of the texture element depth E _R . Preferably, the distance E _RB from the first sliding surface 22 in the radial direction R may be smaller than 40% of the texture element depth E _R . Still preferably, the distance E _RB from the first sliding surface 22 in the radial direction R may be smaller than 25 % of the texture element depth E _R . Still preferably, the distance E _RB from the first sliding surface 22 in the radial direction R may be smaller than 10 % of the texture element depth E _R . Still preferably, the distance E _RB from the first sliding surface 22 in the radial direction R may be smaller than 5 % of the texture element depth E _R .

Purely as an example, the distance E _RB may be 20 μηι and the texture element depth E _R may be 40 μηι. In another example, the distance E _RB may be 30 μηι and the texture element depth E _R may be 50 μηι. However, other values on the distances are conceivable according to the example embodiments as described herein. It should also be conceivable that the distance E _RB from the first sliding surface 22 in the radial direction R is at least above 0 % of the depth of the texture element depth E _R . According to one example, the distance from the first sliding surface in the radial direction is at least more than 2 % of the depth of the texture element depth. Hence, as an example, the distance from the first sliding surface in the radial direction is at least more than 2 % of the depth of the texture element depth, but smaller than 50% of the texture element depth. In another 5 example, the distance from the first sliding surface in the radial direction is at least more than 5 % of the depth of the texture element depth, but smaller than 30% of the texture element depth.

In addition, the first section 59 of the trailing surface 52 here typically has an extension E _C B in the circumferential direction C which is larger than 5% and smaller than

10 50% of the length of the texture element 42 in the circumferential direction C. The length of the texture element 42 in the circumferential direction C is here denoted by the reference E _C . Still preferably, the first section of the trailing surface may typically have an extension in the circumferential direction which is larger than 10% and smaller than 50% of the length of the texture element in the circumferential direction. Still preferably, the first

15 section of the trailing surface may typically have an extension in the circumferential

direction which is larger than 15% and smaller than 50% of the length of the texture element in the circumferential direction. As is shown in the figures, the extension E _C B is a part of the entire length E _C of the texture element in the circumferential direction C

Further, as may be gleaned from fig. 5h, the first section 59 also has an axial

20 extension E _A i . Typically, although not strictly required the first section 59 is tapering along the circumferential direction C in a direction away from the leading edge 54 of the texture element 42. Other shapes of the first section may also be conceivable.

In the example embodiment as shown in fig. 5h, the tapered first section 59 here defines a convex curvature 82, as seen in the axial direction A and in the circumferential

25 direction C. Moreover, in this example embodiment, the degree of the curvature of the tapered first section 59 is similar to the curvature of the leading edge 54 of the texture element 42. In this context, the curvature of the tapered first section 59 here refers to the curvature of the first section as indicated by reference 82, while the curvature of the leading region is here indicated by e.g. leading edge 84. It is be noted that the extension

30 of the curvature of the first section in the radial direction is typically defined by the

extension of the first section in radial direction R, while the extension of the curvature of the leading region is typically defined by the extension of the leading region in the radial direction R, which thus typically extends to the bottom surface 56 of the texture element. Thus, the bottom surface of the remaining texture element here resembles a truncated

35 ellipse. However, the degree of the curvature of the tapered first section may differ from the curvature of the leading edge 54 of the texture element 42. As an example, although not shown, the degree of the curvature of the tapered first section of the trailing region is greater than a curvature of the leading edge of said texture element.

In this context, the curvature of the tapered first section 59 here refers to the curvature of the first section as indicated by reference 82, while the curvature of the leading region is here indicated by e.g. leading edge 84. It is be noted that the extension of the curvature of the first section in the radial direction is typically defined by the extension of the first section in radial direction R, while the extension of the curvature of the leading region is typically defined by the extension of the leading region in the radial direction R, which thus typically extends to the bottom surface 56 of the texture element. Thus, the bottom surface of the remaining texture element here resembles a truncated ellipse.

As mentioned above, the trailing surface 52 here also defines a second section 58 extending from the bottom surface 56. With particular reference again to fig. 5e, the second section 58 of the trailing surface 52 extending from the bottom surface 56 has a normal with a different direction than a normal of the first section 59. As an example, the second section 58 of the trailing surface 52 extending from the bottom surface 56 is arranged to extend essentially perpendicular from the bottom surface 56. However, it also possible that the second section 58 of the trailing surface 52 extending from the bottom surface 56 in some example embodiments may be inclined in relation to the bottom surface 56 as long as the first section is capable of forming a converging gap with the second sliding surface during operation of the hydrodynamic sliding bearing arrangement, as described above. Although the angle between the second section and the bottom surface may typically be 90 degrees it is to be noted that in some example embodiments, the inclination between the second section and the bottom surface may be arranged by an angle between 45 - 90 degrees, as long as the first section of the trailing region is capable of defining a converging gap as explained above.

As is shown in e.g. fig. 5e, the transition from the first section 59 to the second section 58 is defined by a transition point T _P . Thus, the first section 59 and the second section 58 are typically connected at a transition point T _P . To this end, the trailing surface 52 defines a first section extending from the sliding surface 22 to the transition point T _P and the second section 58 extending from the bottom surface 56 to the transition point T _P .

In other words, the distance E _RB may be defined by a distance between the first sliding surface 22 and the transition point T _P , as measured in the radial direction R. As is shown in fig. 5e, which is a cross-sectional view of the texture element, the texture element 42 in this example embodiment has a cross sectional shape extending in the circumferential direction C and a radial direction R, wherein the first section 59 of the trailing surface 52 is arranged to deviate from the first sliding surface 22 by an angle a _c .

In this manner, the first section of the trailing surface is adapted to define a converging gap with a sliding surface of a second sliding member by means of having the first section of the trailing surface arranged to deviate from the first sliding surface by an angle a _c .

Typically, although not strictly required, the angle a _c is between 0.1 - 5 degrees. In this way, there is provided a texture element shape configured to provide an optimal buildup of hydrodynamic pressure. As an example, the angle a _c is about 0.5 degrees. In another example, the angle a _c is about 0.3 degrees. Still preferably, the angle a _c may be between 0.3 - 3 degrees. Still preferably, the angle a _c may be between 1 - 3 degrees. It is to be noted that the angle a _c in fig. 5e is depicted slightly bigger than the above range in order to allow for an illustration of the dimensions, and thus only provide a schematic view of the configuration and the angle. However, it should be readily appreciated that the size of angle a _c may be set to another angle depending on the selection of manufacturing method having specific limitations. Also, operation conditions, sliding velocities, contact conditions oil film thickness and application of the texture element and the hydrodynamic sliding bearing member may cause a _c to be selected in a different interval then specified herein.

Thus, it should be conceivable that the value of the angle a _c may be different for different bearing members and installations.

It should also be readily appreciated that the first sliding surface here refers to the plateau area of the first sliding surface. Accordingly, the texture element has a cross sectional shape extending in the circumferential direction and the radial direction, the first section of the trailing surface being arranged to deviate from the plateau area of the first sliding surface by the angle a _c .

Typically, in some example embodiment, a minimum depth of the texture elements should be above 10 μηι, as further described herein.

With respect to the shape and geometry of the first section, it is conceivable that the first section may be designed in several different ways to form the converging gap G with the second sliding surface 32 (as shown in e.g. fig. 3). As an example, as shown in e.g. fig. 5e, the first section 59 is here a straight wall surface as seen in the cross section extending in the circumferential direction C and the radial direction R. Further, the straight wall surface is arranged to deviate from the first sliding surface 22 by the angle a _c .

Thus, the texture element has a cross sectional shape extending in the

circumferential direction C and the radial direction R, the first section 59 of the trailing surface 52 being arranged to deviate from the first sliding surface 22 by the angle a _c , and wherein the first section 59 is a straight wall surface as seen in the cross section extending in the circumferential direction C and the radial direction R. In this manner, it becomes possible to provide a texture element shape that is capable of increasing the hydrodynamic pressure generation, thus reducing the viscous film shear losses and maintaining the contact in the hydrodynamic lubrication regime and thus minimizing any possible contribution from boundary friction.

In other words, in this example embodiment as shown in e.g. fig 5e, the trailing surface 52 defines a second section 58 and a first inclined section 59. Furthermore, the second section 58 extends essentially perpendicular from the bottom surface of the texture element 56 to the first inclined section 59 of the trailing surface 52. The second section 58 has a length E _RC smaller than the depth E _R , in which the depth E _R is defined by the distance between the sliding surface 22 and the bottom surface of the texture element 56, as seen in the radial direction R. Only as an example, the distance of E _RC may be 50 % smaller than the depth E _R . Typically, the distance E _RC is determined by the extension of the first section 59, i.e. the distance E _RB , as mentioned above. In addition, the first inclined section 59 extends from the second section 58 to the sliding surface 22 of the hydrodynamic sliding bearing member 20, wherein the first inclined section 59 forms the angle a _c with the sliding surface 22 of the hydrodynamic sliding bearing member 20. Due to that the length E _RC of the second section 58 is smaller than the depth E _R of the texture element 42, the angle a _c is permitted to be significantly smaller than a right angle of a conventional texture element shape, i.e. a texture element having a right angle between the sliding surface and the trailing surface. As mentioned above, the angle a _c is typically between 0.1 - 5 degrees.

In this manner, it becomes possible to provide a texture element shape that is capable of increasing the hydrodynamic pressure generation, thus reducing the viscous film shear losses and maintaining the contact in the hydrodynamic lubrication regime.

In view of the above, fig. 5e illustrates an example embodiment of a sliding surface 22 comprising a texture pattern 40 having a plurality of texture elements 42 (although only one element is shown in the figure), wherein each texture element 42 extends in the axial direction A and the circumferential direction C and has a depth E _R in the radial direction R, where the depth is defined by the distance between the sliding surface 22 and the bottom surface 56 of the texture element 42. Further, each texture element 42 has the trailing region 50 as seen in the sliding direction S along the circumferential direction C, the trailing region 50 having the trailing surface 52 defined by the second section 58 and the first section 59. Moreover, in this example embodiment, the second section 58 extends essentially perpendicular from the bottom surface 56 of the texture element to the first section 59 of the trailing region 50, wherein the second section 58 has a length E _RC smaller than the depth E _R , and the first section 59 extends from the second section 58 to the sliding surface 22 of the hydrodynamic sliding bearing member 20. Typically, the second section 58 extends essentially perpendicular from the bottom surface 56 of the texture element to the transition point T _P , as defined by the intersection between the second section 58 and the first section 59 of the trailing region 50. Moreover, the first section 59 forms the angle a _c with the sliding surface 22 of the hydrodynamic sliding bearing member 20. Hereby, first section of the trailing surface is adapted to define the converging gap with the sliding surface of the second sliding member by means of having the first section of the trailing surface arranged to deviate from the first sliding surface by the angle a _c .

It should be noted that in all example embodiments described herein, the angle between the bottom surface 56 and the second section 58 is depicted as a right angle, however, this angle may slightly vary depending on the installation and type of texture element and texture pattern etc. In addition, due to operation conditions as well as manufacturing condition, this type of angle may slightly vary from a right angle as conceived by the skilled person. Thus, the figures are only to be considered as schematic figures with respect to right angles, dimensions and scale.

This example embodiment as described in relation to figs. 5b, 5e and 5h may, as mentioned above, be a part of any one of a main bearing, journal bearing or connecting rod bearing of an internal combustion engine of a vehicle, as described in relation to the figures 1 , 2a - 2g, 3, 4a - 4i, 5a and 6a - 6b, or any other type of bearing in a mechanical device such as a bushing. In addition, this example embodiment of the texture element shape may be arranged in any one of the texture patterns as described in relation to figs. 4a - 4i and 6a - 6b. As mentioned above, there are typically no generic values for the above parameters since the values of each parameter depends on the specific bearing operation and installation etc. Thus, for some applications, the first example embodiment as shown in e.g. fig. 5e may be selected, while for other applications it may be more optimal to select any one of the example embodiments as described in relation to figs. 5c, 5d, 5f or 5g etc.

Besides the shape of the first section of the trailing surface as described in relation to fig. 5 e and 5h, the first section of the trailing surface may be adapted in several other ways in order to define (form) a converging gap with a sliding surface of a second sliding member as will be described further herein.

Thus, in other example embodiments, as shown by e.g. fig. 5g, the first section 59 may be a curved wall surface as seen in a cross section extending in the circumferential direction C and the radial direction R. Fig. 5g is a cross sectional view of yet another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along a circumferential direction and a radial direction.

In this example embodiment, the first section 59 of the trailing surface 52 is adapted to define (form) the converging gap G with the sliding surface of the second sliding member by a curved wall surface. Thus, according to one example embodiment, the first section is a curved wall surface as seen in a cross section extending in the circumferential direction and a radial direction. Typically, the first section extends to the second section of the trailing surface, as mentioned herein. In this way, there is provided a texture element shape configured to provide an optimal build-up of hydrodynamic pressure.

In other words, as shown in fig. 5g, there is provided a hydrodynamic sliding bearing member 20 having a first sliding surface 22 extending in the circumferential direction C and in the axial direction A, and configured for being slidably arranged in the circumferential direction C relative to a second sliding surface 32 of a second sliding member 30 via a viscous fluid to permit the hydrodynamic sliding bearing member to operate under hydrodynamic lubrication. The first sliding surface 20 has a texture pattern 40, which comprises at least one texture element 42. The texture element 42 has a trailing region 50 defined by a trailing surface 52 extending from the first sliding surface 22 to the bottom surface 56 of the texture element 42. Moreover, a first section 59 of the trailing surface 52 is adapted to define a converging gap G with a sliding surface 32 of a second sliding member and extends a distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R . Further, the first section is a first curved section 59.

Thus, the texture element 42 has a trailing region 50, as seen in the sliding direction S along the circumferential direction C. In this example embodiment, the trailing region 50 has a trailing surface 52 defined by the second section 58 and the first curved section 59. Furthermore, the second section 58 extends essentially perpendicular from the bottom surface of the texture element 56 to the first curved section 59 of the trailing surface 52. The second section 58 has a length E _RC smaller than the depth E _R , in which the depth E _R is defined by the distance between the sliding surface 22 and the bottom surface of the texture element 56, as seen in the radial direction R. In addition, the first curved section 59 extends from the second section 58 to the sliding surface 22 of the hydrodynamic sliding bearing member 20, wherein the curvature of the first curved section 59 is convex, as shown in fig. 5g.

In this manner, it becomes possible to provide a texture element shape that is both capable of increasing the hydrodynamic pressure generation by utilising an optimal design at the trailing side of the texture, and, at the same time reducing the viscous film shear losses, generated by the main texture geometry.

In some example embodiments, the curvature may even be concave.

It should be readily appreciated that the radius of the curvature may be selected according to the contact condition and application of the texture element and the hydrodynamic sliding bearing member. Thus, the radius of the curvature may vary according to general design of the bearing, operating conditions such as load and sliding speed etc. Typically, in some example embodiment, a minimum depth of the texture elements should be above 10 μηι.

Besides the above difference between fig. 5g and fig. 5e, it is to be noted that other features and effects as described in relation to fig. 5b, 5e and 5h may likewise be incorporated into the example embodiment as shown in fig. 5g.

This example embodiment may, as mentioned above, also be a part of any one of a main bearing, journal bearing or connecting rod bearing of an internal combustion engine of a vehicle, as described in relation to the figures 1 , 2a - 2g, 3, 4a - 4i, 5a and 6a - 6b, or any other type of bearing in a mechanical device such as a bushing. In addition, this example embodiment of the texture element shape may be arranged in any one of the texture patterns as described in relation to figs. 4a - 4i and 6a - 6b.

As mentioned above, there are typically no generic values for the above parameters since the values of each parameter depends on the specific bearing operation and installation etc.

Yet, in other example embodiments, as shown by e.g. fig. 5f, the first section 59 may be a step shaped section being defined by a first step surface 59a extending essentially perpendicular from the sliding surface 22 and a second step surface 59b extending essentially perpendicular from the first surface 59a to the second section 58.

Fig. 5f is a cross sectional view of yet another example embodiment of the texture element in fig. 5b, in which the cross sectional view illustrates the cross sectional shape of the texture elements along the circumferential direction C and the radial direction R. In this example embodiment, the first section 59 of the trailing surface is adapted to define (form) the converging gap G with the sliding surface of the second sliding member by a step shaped section.

Accordingly, the first section of the trailing surface 52 is adapted to define (form) the converging gap G with the sliding surface of the second sliding member 30 by having a step shaped first section 59. Thus, according to this example embodiment, said first section is a step shaped section being defined by a first step surface 59a extending essentially perpendicular from the sliding surface 22 and a second step surface 59b extending essentially perpendicular from the first step surface 59a to a second section 58.

In other words, as shown in fig. 5f, there is provided a hydrodynamic sliding bearing member 20 having a first sliding surface 22 extending in the circumferential direction C and in the axial direction A, and configured for being slidably arranged in the circumferential direction C relative to the second sliding surface 32 of the second sliding member 30 via a viscous fluid to permit the hydrodynamic sliding bearing member to operate under hydrodynamic lubrication. The first sliding surface 20 has a texture pattern 40, which comprises at least one texture element 42. The texture element 42 has the trailing region 50 defined by the trailing surface 52 extending from the first sliding surface 22 to the bottom surface 56 of the texture element 42. Moreover, the first section 59 of the trailing surface 52 is adapted to define the converging gap G with the sliding surface 32 of the second sliding member and extends the distance E _RB from the first sliding surface in the radial direction R, which is smaller than 50% of the texture element depth E _R .

Thus, the texture element 42 here has a trailing region 50, as seen in the sliding direction S along the circumferential direction C, wherein the trailing region 50 has a trailing surface 52 defined by a second section 58, the first step surface 59a and the second step surface 59b. Furthermore, the second section 58 extends essentially perpendicular from the bottom surface of the texture element 56 to the second step surface 59b of the trailing surface 52. To this end, the second section 58 extends essentially perpendicular from the bottom surface of the texture element 56 to the transition point T _P . In this example embodiment, the second step surface 59b is essentially perpendicular arranged to the second section 58. Typically, the second step surface 59b is parallel to the bottom surface 56 and the sliding surface 22. Furthermore, the second step surface 59b extends from the second section 58 to the first step surface 59a of the trailing surface 52. In this example embodiment, the first step surface 59a is perpendicular arranged to the second step surface 59b. In addition, the first step surface 59a extends to the first sliding surface 22, as shown in fig. 5f. Typically, the first step surface 59a is parallel to the second section surface 58.

This type of shape of the trailing edge of the texture element may also be referred to as the Rayleigh step.

Besides the above difference between fig. 5f and fig. 5e, it is to be noted that other features and effects as described in relation to fig. 5b, 5e and 5h or 5g may likewise be incorporated into the example embodiment as shown in fig. 5f.

This example embodiment may, as mentioned above, be a part of any one of a main bearing, journal bearing or connecting rod bearing of an internal combustion engine of a vehicle, as described in relation to the figures 1 , 2a - 2g, 3, 4a - 4i, 5a and 6a - 6b, or any other type of bearing in a mechanical device such as a bushing. In addition, this example embodiment of the texture element shape may be arranged in any one of the texture patterns as described in relation to figs. 4a - 4i and 6a - 6b.

As mentioned above, there are typically no generic values for the above parameters since the values of each parameter depends on the specific bearing operation and installation etc.

Furthermore, it should be readily appreciated that the shape of the texture element 42 may form another shape than an ellipse. Thus, the shape of the texture element as seen in the axial direction A and in the circumferential direction C may be provided in several different geometries as long as the effects of the example embodiments can be provided by the texture element shape. For instance, it may be conceivable that the cross sectional shape in the axial direction A and the circumferential direction C may be a rectangle, circle, triangle, or any other suitable shape.

Furthermore, in all example embodiments as described in relation to figs. 5a - 5i, the texture element 42 may be defined by the leading region having a leading surface 54 extending from the bottom surface 56 to the first sliding surface 22 by an angle a _L of between 45 - 90 degrees. The angle a _L is herein defined by the angle between the bottom surface and the leading surface 54 (extending between the first sliding surface 22 and the bottom surface 56). As shown in the figures, the texture element 42 is here defined by a leading region having a leading surface 54 extending essentially perpendicular from said bottom surface 56 to said first sliding surface 22.

Moreover, in all example embodiments as described in relation to figs. 5a - 5i, the bottom surface 56 is typically essentially parallel to the sliding surface 22. A texture element having a bottom surface being essentially parallel to the sliding surface provides that the depth of the texture element along the tangential texture element length (length of the texture element in the circumferential direction) can be sufficiently deep for a substantial part of the texture element length, thus maintaining the desired fluid film thickness within the texture and thus not increasing the viscous shear losses.

In addition, a length of the bottom surface 56 here has an extension E _c in the circumferential direction C which is larger than 50 % and smaller than 85% of the length of the texture element 42 in the circumferential direction C.

Further, although a cross sectional shape resembling an ellipse has been used as the main reference for the shape of the texture element as seen in the direction A and direction C, it is to be noted that the cross sectional shape in the axial direction A and circumferential direction C may be a rectangle, circle, triangle, or any other suitable shape. As shown in fig. 5b, the cross sectional shape is essentially an ellipse, extending in the axial direction A and in the circumferential direction C. Thus, in all example embodiments as described herein, and in other example embodiments, the texture elements may each have one of a substantially circular, oval, or elliptical shape. It will be appreciated, however, that the texture elements can have other shapes, such as triangular, grooves, square, rectangular, diamond, etc. In addition, texture element shapes may include open or closed voids. That is, any one of the texture elements may have a cross-sectional shape in the form of a square, rectangle, circle, or ellipse.

It is also to be noted that although the example embodiments as described in relation to figs. 5b - 5i only depicts one texture element, the various examples of the texture element and examples of the first section having the converging gap may typically be utilized for at least a substantial part of all texture elements of the sliding surface(s). Still preferably, the various example embodiments of the texture element and the converging gap may typically be utilized for all texture elements of the sliding surface(s).

As mentioned above, it has been observed that hydrodynamic friction can be efficiently reduced by decreasing the texturing area density towards at least one of the axial boundaries, as seen from a centre of the first sliding surface in the axial direction. There are several possible ways in which area density can be varied, e.g. the texture elements might have a uniform size (axial and circumferential length, diameter, perimeter etc.), and the quantity of texture elements per unit area might be decreased so that the area density will be decreased. In addition, or alternatively, the size of texture elements decrease (axial length and circumferential length), and the quantity of texture elements per unit area might be kept constant to provide a decrease of the area density because texture elements with larger size decrease the amount of plateau area and texture elements with smaller size increase the amount of plateau area.

According to one example embodiment (not shown), the area density of the texture elements is further varied along the circumferential direction C. The area density can be varied in similar manner as mentioned above with respect to decreasing area density towards the axial boundary. In other words, the area density of the texture elements may be varied along the circumferential direction C by decreasing at least one of the axial length E _A and the circumferential length E _c of each texture element per unit along the length of the first sliding surface as seen circumferential direction C of the first sliding surface. Alternatively, the area density of the texture elements may be varied along the circumferential direction C by increasing at least one of the axial length E _A and the circumferential length E _c of each texture element per unit along the length of the first sliding surface as seen circumferential direction C of the first sliding surface.

In addition, or alternatively, the area density of the texture elements may be varied along the circumferential direction C by decreasing the quantity of texture elements along the length of the first sliding surface as seen in the circumferential direction C of the first sliding surface.

Alternatively, the area density of the texture elements may be varied along the circumferential direction C by increasing the quantity of texture elements along the length of the first sliding surface as seen in the circumferential direction C of the first sliding surface.

In addition, or alternatively, the depth of the texture elements may be varied along the circumferential direction C by increasing or decreasing the depth of the texture elements along the length of the first sliding surface as seen in the circumferential direction C of the first sliding surface.

It should be readily appreciated that decreasing or increasing the area density or increasing or decreasing the texture depth may either be linear or non-linear as a function of axial dimension and circumferential dimension.

In all example embodiments as described herein, and in other example embodiments, the hydrodynamic sliding bearing member 20 may be incorporated in a hydrodynamic sliding bearing arrangement 10, so that the hydrodynamic sliding bearing member 20 is a first sliding member according. Typically, the hydrodynamic sliding bearing arrangement 10 further comprises the second sliding member 30 having the second sliding surface 32.

Furthermore, in this type of arrangement, the first sliding member 20 is centred around the second sliding member 30 so that the hydrodynamic sliding bearing arrangement is configured to support a rotational motion between the first sliding member and the second sliding member. As an example, the first sliding surface 22 of the first sliding member 20 is an inner circumferential surface and the second sliding surface 32 of the second sliding bearing member 30 is an outer circumferential surface. The first sliding bearing member 20 is further centred around the second sliding bearing member 30 so that the inner circumferential surface is allowed to slide about the outer circumferential surface of the second sliding member, via the viscous fluid 60 upon rotation of the second sliding member 30 relative to the first sliding member 20.

Although not shown, it is to be noted that when the hydrodynamic sliding bearing member is installed in a hydrodynamic sliding bearing arrangement, the construction may optionally, although not strictly required, be further configured to form a sealed

arrangement in order to seal between the first sliding member and a second sliding member of the arrangement, as seen in the axial direction A.

As described by the example embodiments herein, one example advantage of the example embodiments of the hydrodynamic sliding bearing member, and the

hydrodynamic sliding bearing arrangement, is to reduce fuel consumption by reducing hydrodynamic friction losses in the internal combustion engine of the vehicle in an optimal way.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

It should be noted that the hydrodynamic sliding bearing members in figs. 2a - 6b are merely general schematic representations of a hydrodynamic sliding bearing member, and intended to show the underlying principle of the inventive concept. Accordingly, the components may include further features, functions and sub-components not shown in the figures.

Further, any of the features described above may be provided in combination or separaely and elements from one implemenation may applied without limitation in other implementations, for similart or distinct technical effects, as one skilled in the art may understand.

In the present application, the use of terms such as "including" is open-ended and is intended to have the same meaning as terms such as "comprising" and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as "can" or "may" is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.