Field of application

The invention here described refers to a piston and rod perfected for use in an internal combustion engine and configured so as to produce a considerable overall improvement in the engine's performance in all conditions in which said engine functions. Current state of the art

The state of the art comprises various types of piston and rod which, in combination, are orientated so as to improve the contact between the rod foot and piston, and in order to produce, in the way best suited for performance, the oscillation which typically occurs in a cross journal in a crank mechanism. The drive generated by the fluid (combusted gas or in compression) is generally unidirectional from the piston towards the rod foot, but often the forces of inertia, due to the mass of the piston and rod, with the reduction of the unidirectional drive of the fluid, invert the direction of the forces transmitted by the rod foot and the piston. Hence, technology features rods that are longer than the real length in that the centre of rotation of the rod foot on the piston is displaced towards the upper surface of the piston crown and therefore the rod is shorter in order to reduce the bulk of the engine while maintaining the same swept volume developed, in that the angle of oscillation is smaller than it is with the traditional piston pin. In their research, constructors of internal combustion engines have designed and engineered various ways of coupling the piston with the rod.

Current technology designed to reduce the dimensions of the engine comprises a previous document, EP 449278 A1 , which registers an oscillating connection between the piston and its rod, featuring a hemispherical concave surface in the section of an end plate at the foot of the rod; said rod in turn joined by a sliding coupling to a hemispherical convex surface in the lower central part of the piston crown and a tubular element, supported at the side skirt of the piston, and coupled with the lower surface, similarly hemispherical, of the said end plate of the rod foot. In addition, the previous document also describes various sliding members placed between the end plate of the piston to prevent wear in the piston rings and knocking due to the variations in the piston's alternating movement.

Similarly, though the solution proposed by the said document makes it possible to move the centre of relative rotation between piston and rod, of the sliding coupling at the foot of the rod, the complexity of the elements placed between them, which also create more spaces full of lubricating oil, does not make it possible to reduce the thickness of the walls and floors, and hence of the masses in play, and thus the said pistons have to be produced in cast aluminium or other equivalent light alloys. In other words, while pistons in light alloys make it possible to create complex internal structures in the piston, they also require an increase in piston size, with greater clearances in the diameters so as to allow the piston to function while cold, rather than warm, compared with the cylinder barrel. Also, being produced with a slightly conical profile, a sealed fit is obtained only when the engine is completely warmed, making it possible to achieve the parameters for reducing emissions established by anti air pollution norms.

Current technology recognises a composite piston registered under a previous document, EP 451011 A1 , featuring a spherical connection between the foot of the rod and the piston, said modification presenting a hemispherical shell designed to house the spherical rod head, creating in the hemispherical housing a central cavity for the forced lubrication of the oscillating contact. The pressurised oil flows in a channel along the axis of the rod's body and presents a one-way, spherical valve which opens in response to the flow of oil in the pressurised lubrication circuit; in addition, radial holes are provided in the axial channel upstream of the one-way valve to feed the oil for cooling the lower part of the piston skirt from the inside. The said hemispherical shell is water-tight and connected to the said piston skirt so as to receive, in the cavity between the outer surface of the shell and the inside of the piston, a hydraulic fluid, lubricating oil or gas under pressure to reduce any distortion to the shell from the axial driving force created by combusted gases in the endothermic engine.

Furthermore, such a configuration requires a piston more complex in design, given that the shell, fashioned in a material that tends to undergo slight distortion, must be applied to the skirt from the inside so as to create the water-tight fit in the cavity and allow the hydraulic fluid or gas to act on the outer surface of the shell, thus reducing distortion. In this way the bulk of the axial drive from gases combusted in the cylinder are transmitted to the rod, and thus to the drive shaft. The one-way valve ensures that the spherical coupling is lubricated and that the oil is fed into the ball joint between the shell and the rod foot, functioning as a hydraulic jack driven by the axial pressure generated by the alternating movement of the piston inside the cylinder. Thus, even when the coupling between the rod foot and the piston is of the oscillating kind, the piston being of more complex design in order to reduce friction, a simple conformation effective in reducing resistance to the flow is not engineered.

Current technology can be substantially improved by creating an oscillating coupling between the piston and the perfected rod, which overcomes the above- mentioned shortcomings and contributes to the reduction of the overall complexity of the solutions outlined, contributing further to a marked overall improvement in the mechanism's performance, even when the engine is cold, that is to say when the internal combustion engine is first ignited. Thus the technical challenge that underlies the invention herein described is that of creating an oscillating coupling between the rod foot and the piston that allows for a reduction of the parts used, while at the same time offering a simpler, lighter and more reliable solution both at low starting temperatures and also at temperatures attained when the internal combustion engine is in its fully operational phase.

A further, though not minor, aspect of the invention described herein is that of engineering a configuration with an increased capacity to lubricate those oscillating surfaces in contact between the rod foot and the piston.

Further again, another goal of the invention herein described is to engineer a configuration with an enhanced capacity for cooling the piston itself in such a way as to produce a considerable transfer of heat from the point where it accumulates as an effect of the combusted gases acting on the piston. Finally, a further aspect of the technical challenge outlined above is that of engineering a mechanism to prevent reciprocal rotation between piston and rod that can be quick and easy to create and which does not impact negatively on the results of lubrication and cooling obtained by a coupling without the antirotational mechanism.

Invention summary

The invention herein described solves this problem by proposing a piston and connecting rod perfected for use in an internal combustion engine comprising a piston rod foot, furnished with a concave spherical cup-socket on the internal surface, to form an oscillating coupling with the lower convex spherical surface of the piston crown; the said spherical cup-socket is furnished with an outer convex spherical surface which is concentric to the inner concave spherical surface; a retention ring presents an inner concave spherical surface coupled and sliding on the said outer convex spherical surface of said cup-socket; the ring in turn being connected in a movable fashion to the internal part of the piston skirt by means of blocking elements, exerting a radial action on the skirt; a channel running along the axis of the piston rod's body conveys lubricating oil under pressure from the crankpin; characterised in that the piston is provided with an accumulation chamber created on the piston crown adjacent to the said axial channel; a limiting valve, subject to the action of a loading spring, limits the outflow of the oil under pressure from the crankpin to a value greater than a minimum pressure value, and the oil flows towards the said accumulation chamber and the oscillating coupled surfaces.

In addition, in a perfected version: the above-mentioned blocking elements are inserted in radial holes in the piston skirt and distributed around the entire circumference of said skirt.

Moreover, in another version: the retention ring is made in two halves coupled on the inside of the piston skirt.

Furthermore, in yet another version: the spherical limiting valve can regulate the opening pressure to the value calibrated for the specific requirements of the piston rod. Further still, in a specifically constructed version: the retention ring is formed of two halves coupled inside the piston skirt; the two halves are a mirror image, one of the other, subdivided on the axial plane by a step-fit coupling and a joining pin.

Further yet, in a variant form of construction: a reciprocal antirotational mechanism between piston rod and piston is created with elements placed between the piston cup-socket and crown, aligned on the plane of reciprocal oscillation, and sliding, in its oscillation, on the rod's oscillating plane with respect to the piston.

Further still, in a perfected version: a reciprocal antirotational mechanism between the piston rod and piston is created with ball bearings lodged in housings on the internal concave spherical surface, and aligned on the reciprocal axial plane of oscillation and sliding, in their oscillation, in radial grooves, aligned with the plane of oscillation of the piston rod with respect to the piston, located on the lower convex surface of the piston crown.

In addition, in a preferred version: the flow of lubricating oil towards the accumulation chamber also performs a cooling function on the accumulation chamber walls, said chamber walls being engineered in the piston crown, adjacent to the walls of the combustion chamber.

Moreover, in a version which is even more perfected: the piston is engineered in steel.

Finally, an internal combustion engine equipped with alternating pistons with an oscillating coupling between piston and rod that is engineered as per one or more of the piston and rod features described previously.

The features and benefits of the invention herein described, created with a perfected piston and rod for use in an internal combustion engine, are indicated in the following descriptions of some outline embodiments, intended to illustrate but not oversimplify, and which refer to the four illustrated drawing sheets appended.

Brief description of the drawings

Figure 1 represents a schematic section of a piston-piston rod foot group coupled as per a form of the invention here presented, with the reciprocal rotation feature between piston and piston rod, created on the plane containing the axis of the cylinder and the axis of the piston rod in its oscillating movement;

Figure 2 represents a perspective view of the piston rod foot with the hemispherical cup-socket and of part of the piston rod;

Figure 3 represents a perspective view of a schematic section, similar to the section in Figure 1 , of the form to be constructed, showing the reciprocal rotational capability between the piston rod and piston;

Figure 4 represents a perspective view of the two halves of a retention ring, here separated, which is designed to keep the piston rod foot seen in Figure 2 in position and in contact with the piston crown, as per the version depicted in Figures 1 -3;

Figure 5 represents a perspective view in a schematic section of a construction form in which reciprocal rotation between piston rod and piston is not possible;

Figure 6 represents a perspective view of the piston rod foot with a hemispherical cup-socket and of the piston rod designed for use in the construction form seen in Figure 5;

Figure 7 represents a perspective view of the piston with the convex spherical lower surface of the piston crown in which grooves have been created for the movement of the parts preventing rotation between piston and piston rod;

Figure 8 represents a view in schematic section of the construction form in Figure 5, which prevents reciprocal rotation between piston rod and piston; it is executed on the plane containing the cylinder axis and the piston rod axis in its oscillating movement;

Figure 9 represents a view in schematic section of the construction form in Figure 5, executed on a plane at right angles with respect to the schematic section in Figure 8;

Figure 10 represents a perspective view of the retention ring in two halves, here separated, designed to keep the piston rod foot in Figure 6 in position when in contact with the piston crown (Figure 7), located on the concave spherical surface of the piston rod foot, and the convex spherical surface located on the inside of the piston crown.

Detailed description of preferred embodiments of construction

In Figures 1 to 4, in a construction form for the perfected piston 1 and piston rod 2 in which the piston rod foot 3, whose centre of instantaneous rotation is P, presents an extremity 4 in a spherical cup-socket shape 5, concave on its internal surface 6, for coupling in oscillation with a convex spherical lower surface 7 of the crown 8 of the piston 1 . The extremity of the piston rod foot 4 features the said spherical cup-socket 5 equipped with a convex spherical external surface 9, being concentric to the concave internal spherical surface 6. A retention ring 10 presents an internal concave spherical surface 1 1 coupled and moving on the said external convex spherical surface 9 of the said cup-socket 5, forming the foot of the piston rod 3; the said ring is in turn connected in a movable fashion to the internal part of the piston 1 skirt 12 by means of blocking elements 13, threaded and acting radially on the piston skirt 12, and distributed around the entire circumference of said skirt.

The upper surface 14 of the piston 8, exposed to combustion gases, is concave in shape so as to form a combustion chamber 15 concentric to the axis of the piston X, in view of the reciprocal rotation capability between piston 1 and piston rod 2, and the lower surface 7 of the piston crown features an accumulation chamber 16 for lubricating oil, adjacent to the wall 15 of said combustion chamber. The oil flows under pressure from the forced lubrication plant by means of an axial channel 17 in the body of the piston rod 2, and is restrained by a limiting valve 18 of the ball bearing type against the force provided by a loading spring, so as to allow the lubricating oil to maintain full flow at correct pressure in the crankpin, also when the oil feed pressure is lower; the oil flows into the accumulation chamber 16 discharged by the corresponding crankpin, here not depicted; the accumulation chamber is designed to feed the lubricating oil into the channels on the spherical surfaces where contact creates friction (6, 7, 9, 1 ): radial channels 19 are provided on the concave spherical surface 6; inclined channels 20 are provided on the concave spherical surface 1 1. On the skirt 12 for the piston 1 ring-shaped housings are provided for the retention rings and oil seal, well-known to the technology and not further described here, in sliding contact for the alternating motion between the piston 1 and the barrel C of the cylinder in which it is housed. In the forced-lubrication sliding motion, as mentioned above, the oil, which exits from the rim of the cup-socket 5, also fills the cavity 21 between the skirt 12, the piston crown 8 and the cup-socket 5, being pushed towards the radial exit holes 22, as well-known to the technology, and the axial ones 23, present on the said retention ring 10 and equally distributed around its entire circumference; thus, apart from the said spherical surfaces, the oil also lubricates the moving contact of the skirt 12 against the barrel C, and by means of further radial holes 24 aligned with the circular housing of the oil-seal ring, returns into the endothermic crankcase. Finally, the retention ring 10 is opportunely fashioned in two mirror- image halves 25, subdivided on an axial plane by a step-fit coupling 26 and with a connecting pin 27 between them, visible in figure 4. In Figures 5 to 10, a perfected version of the piston and piston rod can be seen, as per the invention here described, being designed in a form similar to that in Figures 1 to 4, here, however, equipped with the parts referred to in such a way as to prevent the free reciprocal rotation between piston and rod and allowing only oscillation. Corresponding parts in the various versions are indicated with identical references.

Thus the version without reciprocal rotation capability features a piston 31 coupled to a perfected piston rod 2 in which the foot of the piston rod 3, with its centre of instantaneous rotation P, features an extremity 34 shaped to conform to the spherical cup-socket 35, which is concave on its internal surface 6, for oscillating coupling with the lower surface 7 of the crown 38 of the piston 31 whose form is convex and spherical. The extremity of the piston rod foot 34 features the above-mentioned spherical cup-socket 35 provided with an external convex spherical surface 9 which is concentric to the internal concave spherical surface 6. A retention ring 40 presents an internal concave spherical surface 1 1 coupled and sliding on the said external convex spherical surface 9 of the said cup-socket 35, which constitutes the foot of the piston rod 3; said ring is in turn connected in a movable fashion to the inner part of the skirt 12 of the piston 31 by means of blocking elements, threaded and acting radially on the skirt 12, and distributed around the entire circumference of said skirt.

The upper surface 44 of the piston crown 38, exposed to the combustion gases, is concave in shape, so as to form a combustion chamber 15 concentric to the axis of the piston X, and presents on the lower surface 7 of the crown an accumulation chamber 16 for lubricating oil, which is adjacent to the wall of said combustion chamber 15. The oil flows under pressure from the forced lubrication plant along an axial channel 17 in the body of the piston rod 2, and is restrained by a limiting valve 8, opportunely of the ball-bearing type, against the action of a loading spring, so as to maintain the full flow of lubricating oil at correct pressure in the crankpin, also when the oil is fed at lower pressure; the oil flows into the accumulation chamber 16 discharged by the corresponding crankpin by means of the piston rod head 39; the rim 41 of the piston rod head does not present the usual notch to facilitate the discharge of the oil which has lubricated the crankpin, and prevent cracking. Thus, the accumulation chamber, receiving a large quantity of oil, feeds the channels which lead the said lubricating oil onto the spherical surfaces in sliding contact (6, 7, 9, 1 1): on the spherical concave surface 6 radial channels 19 are provided; on the concave spherical surface 1 1 inclined channels are provided 20. Circular housings are provided on the skirt 12 of the piston 31 for the retention rings and oil seal, well-known to the technology and not further described herein, in the sliding contact for the alternating movement between the piston 31 and the barrel C of the cylinder within which it is housed. While the forced lubrication is flowing, as mentioned above, the oil that flows over the rim of the cup-socket 35 also fills the circular cavity between the piston skirt 12, the crown 38 and the cup-socket 35, being forced towards the exit holes, both radial 22, as well-known in the technology, and axial 23, present on the said retention ring 40 and equally distributed over the entire circumference; thus the oil also lubricates the sliding contact of the skirt 12 with the barrel C, and, by means of further radial holes 24 corresponding to the circular housing for the oil-seal ring, returns to the endothermic engine's crankcase.

The mechanism for reciprocal antirotation between the piston rod 2 and the piston 31 is achieved with ball-bearings 32, sited in housings 33 and aligned along the reciprocal axis of oscillation, which is that shown in section in Figures 5 and 8, and sliding, in oscillation, within radial grooves 36, aligned on the plane of oscillation of the piston rod with respect to the piston, and present in the lower convex spherical surface 7 of the crown 38 of the piston 31 . In this way, rotation being thus prevented, discharges 37 for the mushroom valves, well-known to technology, are created on the upper surface 44 of the crown 38 of the piston.

Finally, the retention ring 40 is created, opportunely in two mirror-image halves 55, subdivided on the reciprocal axial plane of oscillation between the piston rod and the piston 31 joined by a step coupling 56 with a joining pin 57, as can be seen in Figure 10.

The above-mentioned versions differ in respect of the means employed to prevent the reciprocal rotation between the piston rod 2 and the piston 31 , said means being absent in piston 1 . Hence, the assembly and function are described together, after which the means for antirotation are described separately.

The oscillating coupling between the piston rod 2 and piston 1 , 31 is created with the extremity of the piston rod foot 3 by means of a cup-socket with a spherical design 5, 35 provided with two partial concentric spherical surfaces (concave 6 and convex 9) in the centre of instantaneous rotation P of the said piston rod foot 3. Said partial concentric surfaces are in turn joined by a sliding coupling with corresponding partial spherical surfaces (concave 1 1 and convex 7). The said surfaces are identically concentric to the centre of instantaneous rotation P of the piston rod foot, the convex one 7 being created first on the lower surface of the piston crown 8 or 38, and the concave one 1 1 being created second on a retention ring 10 or 40 housed inside the piston skirt 12 of the relative piston 1 , 31 , ensuring the correct oscillating position of the piston rod 2 on the piston.

Thus the oscillating motion occurs for the sliding movement, mediated by the lubricating oil, of said coupled partial spherical surfaces. The oil, which is driven under pressure by the lubricating circuit of the type well-known in internal combustion engine design, fills the accumulation chamber 16, always directly connected, throughout the piston rod's oscillation cycle, with the channel 17 and limiting valve 18. The valve consists of a ball-bearing with a contrast spring, and can be calibrated for a minimum opening pressure, so as to ensure upstream, that is in the coupling between the relative crankpin and the piston rod head, a pressure sufficient to maintain the coating of oil for lubrication meatus in the turning pair. Thus, only a minimum quantity of oil from the usual lubrication circuit spills over the edge of the crankpin, the bulk being driven along the axial channel

17 towards the piston rod 3. Once the pressure calibrated by the reduction valve

18 has been achieved, the said valve opens to allow the oil to pass towards the accumulation chamber 16. A drop in pressure below the calibrated value allows the valve to close to the flow of oil and ensure the lubrication of the crankpin. Whereas, if the pressure of the oil in the axial channel 17 remains above that calibrated in the limiting valve, the oil will continue to flow towards the piston rod foot and the sliding surfaces; as mentioned above, the oil will also fill the circular space in response to losses of the same, both via the radial lubrication holes 22 in the piston skirt 12, and via the axial holes 23 which discharge the oil in the crankcase. In addition, in the oscillation of the extremity 4 or 34 of the piston rod 3 the relative rim of the extremity 5 or 35 opens the discharge via the central aperture in the centre of the retention ring 0 or 40 in such a way as to effect an immediate discharge from the said circular cavity 21 and favour an exchange of oil in the accumulation chamber 16.

Thus, in the design for the piston rod foot 3 described herein, the quantity of oil that flows through it is much greater than in current designs for the coupling of pistons and piston rods in known endothermic engines. That is, with the invention described here, a flow of lubricating oil is also created which, coming into contact with the piston crown 8 or 38, and by conduction from the combustion chamber, exports the heat that is generated with each cycle, allowing the engine parts to contain their temperatures, in particular that of the piston crown.

The antirotation mechanism is created with two elements placed between the extremity 34 of the piston rod and the internal surface 7 of the piston crown 31 ; said elements are opportunely constituted of a ball bearing 32 inserted in a partially spherical housing 33 provided in the said extremity 34; each ball bearing remains inserted in its respective radial groove 36 so as to allow the cup-socket, that is the piston rod 2, to make an oscillating movement on the plane defined by the two aligned radial grooves 36. Even with the antirotation mechanism sudden discharges of lubricating oil from the circular cavity 21 occur with a marked outflow of oil from the accumulation chamber 16.

Following the creation of the perfected coupling between piston and piston rod, as per the above description, other known aluminium alloys or steel or other materials can be employed in the resized piston, both to export the heat generated in combustion, and for the design of the sliding surfaces which are more ample and well lubricated, so as to avoid the risk of concentrating Herzian pressures in the limited contact in the current versions. That is the dimensions required can be markedly less thick than is necessary when using aluminium alloys. The reduced thicknesses ensure safe transmission of heat even if steel has a lower heat- conduction coefficient, whereas when warm, its mechanical resistance coefficient is much higher, and thus the thickness of the walls of the piston skirt can be markedly reduced without a reduction in reliability.

Another significant result is obtained thanks to the dilatation features, whereby the dimensions of the piston vary according to whether it is hot or cold. With current technology the use of aluminium requires much greater clearance between the piston and the lining due to the elevated dilatation that is a feature of aluminium alloys. The use of steel, whose dilatation coefficient when warm is low compared with when it is cold, means that the piston can be engineered with reduced clearance and a more defined cylinder conformation. This translates into a significant reduction in the clearance between the piston and the barrel: when cold, the engine produces much less non combusted gas and smoke in the exhaust, making it possible to achieve the more stringent environmental pollution norms on emissions from internal combustion engines.

The benefits that derive from using the piston and piston rod perfected for use in an internal combustion engine as described above are outlined below.

The conformation for the coupling of piston and piston rod, whose sliding surfaces are partially spherical, makes it possible to engineer crank systems, pistons and rods that are smaller and lighter for engines of the same cylinder capacity. The power and performance obtained are improved, in particular given the overall reduction of weight in the crank mechanism and the specific lubrication and cooling in the piston crown. In addition, the construction form, both for engines that require the rotation of the piston on the piston rod, and for engines that require preventing rotation between rod and piston, proves very similar, and thus the two different types of coupling can be produced with the same procedures, since the only difference lies in the antirotation elements: the ball bearings 32, the housings 33, the conformation of the cup-socket 35, and the radial grooves 36 can be created at the end of the production cycle with further work on the pistons and rods.

In conclusion, the most evident benefits are the reduction of the clearance in the couplings and the piston profile, which is more cylindrical in steel, as well as the consequent reduction in non-combusted gas emitted into the environment. The latter benefit is especially evident when the engine is in the warming phase, since current versions produce a greater amount of smoke. This is because with a piston in aluminium more clearance is needed in the coupling, and the piston profile, which is conical, needs to be more accentuated given that aluminium alloys present greater dilatation at high temperatures compared with steel.

Thus also the greater mechanical resistance of a steel piston compared with an aluminium leads to higher specific performances, thus also to a better carburetion ratio, making poorer mixtures available, which, as is well known, generate higher temperatures in the combustion chamber. Other features of the invention here described, that is the capacity to cool the piston crown adjacent to the combustion chamber, as well as the greater resistance of steel at higher temperatures, ensure such results.

Obviously, the piston and piston rod perfected for use in an internal combustion engine, as described above, might be subject to numerous modifications by a technical expert in the field in order to meet specific contingent demands, all of which would fall within the protection of the invention here registered and as defined under the following claims. Thus, the reduction valve 18 might be engineered using a moving shutter without a ball bearing.