TECHNICAL FIELD

[0001] The present subject matter relates to an internal combustion engine. More particularly, the present subject matter relates to a piston assembly of the internal combustion engine.

BACKGROUND

[0002] A piston, of a piston assembly, is a component of reciprocating engines, reciprocating pumps, gas compressors etc. Pistons are usually equipped with one or more piston rings. These are circular metal rings that fit into grooves in piston walls and assure a snug fit of the piston inside a cylinder block. They provide a seal to prevent leakage of compressed gases around the piston and to prevent lubricating oil from entering the combustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS [0003] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig.l is an exploded view of piston assembly as per one embodiment of the present invention.

[0005] Fig.la is an assembled view of piston assembly as per one embodiment of the present invention.

[0006] Fig.lb is a sectional view of piston assembly with one or more gas port as per one embodiment of the present invention.

[0007] Fig.lc is a zoom view of top land of piston assembly as per one embodiment of the present invention.

[0008] Fig.ld is a zoom view of top land of piston assembly with first piston ring groove as per one embodiment of the present invention

[0009] Fig.2 is a sectional view of piston assembly with one or more gas port on second land as per another embodiment of the present invention. [00010] Fig.2a is a zoom view of second land of piston assembly with second piston ring groove as per one embodiment of the present invention

[00011] Fig.3 is a sectional view of the piston assembly with one or more gas port on the top land and second land as per another embodiment of the present invention.

[00012] Fig. 4 is a graphical representation as per embodiment of the present invention.

DETAILED DESCRIPTION

[00013] A piston assembly is a primary component of a power unit e.g. an internal combustion engine. The main function of the piston assembly is to transform the pressure generated by burning air-fuel mixture into force, acting on a crankshaft through reciprocatory motion. The piston assembly also performs secondary functions like ensuring sealing of combustion chamber, preventing gas leakages from it and oil penetration into combustion chamber.

[00014] The shape of the piston of the piston assembly depends mainly on type of combustion engine. Gasoline (petrol) engine pistons tend to be lighter and shorter compared with the diesel engine pistons. The piston is connected to a connecting rod through a piston pin. The pin is kept in place in the piston by a pin retaining clip.

[00015] A piston crown is an upper part of the piston assembly. Conventionally. Piston assembly has three ring grooves, in which one or more piston rings are mounted. The top ring is called a compression ring, the middle one is a scraper ring and the bottom one is an oil control ring. The compression ring needs to seal the combustion chamber in order to prevent the inside gases from escaping into a cylinder block. The oil control ring scraps the oil from a cylinder wall, when the piston is on a power or exhaust stroke. The middle ring has a combined role of assuring compression in the cylinder and scrapping excess oil from the cylinder walls. Further, the piston assembly takes up the pressure exerted by combustion gases and coverts it into a reciprocating motion inside the cylinder block.

[00016] A piston skirt keeps the piston balanced inside the cylinder. It is usually covered with a low friction material to reduce the friction losses. A piston pin bore or boss hosting the piston pin, which connects the piston to the connecting rod. [00017] The main parameter in the one or more piston ring (referred as piston ring) of the piston assembly that affects sealing of the combustion gases is a radial outward normal force exerted by the piston ring against the block. This force is called as piston ring tangential load. The piston ring seals the combustion chamber through inherent and applied pressure. Inherent pressure is the internal spring force that expands the one or more piston ring based on the design and properties of the material used and the tangential load is achieved by the inherent pressure of the one or more piston ring. In conventional design of piston assembly, sealing of the combustion gases occur by pushing the piston rings against the block due to the fixed piston ring tangential load, that is, increased tangential load improves sealing of the gases. However, it directly affects friction of the piston rings in the internal combustion engine as friction is directly proportional to tangential load of piston rings with relation of F=pN, where m is a coefficient of friction between the piston rings and the block interface and N is the radial outward force. Thus, by this relation, higher piston ring tangential load in the conventional design leads to higher friction of the piston. In the scenario, when engine is running at lower RPM, even then the increased tangential force gets applied on the piston rings. This ensures the sealing of the gases but however, increases friction, results into poor mileage, and higher emissions of the vehicle as the engine is pushed to work harder. Thus, there is a contradictory challenge to reduce the piston rings tangential load to reduce friction while improving sealing of the combustion gases by the piston rings.

[00018] Typically, in known art, a combination of a wedge shaped, pressure backed piston ring and piston, with piston rings located closely adjacent to top end of the piston is disclosed. A top land of the piston is relieved to allow the combustion gases to exert positive downward and outward pressure on the ring. This configuration has its own disadvantage that the wedge shaper piston and piston ring is configured to achieve the desired output that is to ensure sealing, but compromises durability of the piston and piston rings.

[00019] In another known art, an engine with piston and a non-contact bearing between the piston and a cylinder is disclosed. The non-contact bearing is included in a clearance gap between the piston and a bore. A bearing fluid is supplied to the clearance gap through the piston and/or the cylinder. This configuration has its own disadvantage that it is a complex configuration and also not cost effective. Further it also increases manufacturing time of lubrication flow path inside piston for decreasing friction.

[00020] Further, in another known art, piston with vertical and horizontal gas ports is disclosed to reduce tangential load. However, this configuration has its own disadvantage that the vertical gas port is prone to carbon clogging in passage of the port and the horizontal gas ports leads to poor sealing due to problem of accessibility of combustion gases to backside of pistons rings.

[00021] Hence, there exists a contradictory challenge of designing a piston assembly to reduce piston rings tangential load for reducing friction while improving sealing of combustion gases by piston rings of piston assembly.

[00022] Therefore, there is a need to have an improved piston assembly, which reduces the piston rings tangential load for reducing friction while improving sealing of the combustion gases by the piston rings of the piston assembly and also, overcoming all of the above problems and other problems of known art.

[00023] The present invention provides a solution to the above problems while meeting the requirements of minimum modifications in the utility box of the vehicle.

[00024] With the above objectives in view, the present invention discloses a piston assembly and more particularly an improved piston assembly having one or more gas port which reduces the tangential load and improves sealing of the combustion gases.

[00025] As per one aspect of the present invention, a piston assembly comprising one or more piston rings, a crown/head portion, piston skirt, piston pin, gas ports etc. is disclosed. The head portion comes into contact with combustion gases. Further, as per one aspect of the present invention, the gas ports having, a predetermined diameter, are disposed angularly/inclinedly on top land of piston assembly with respect to piston assembly mid plane axis. The holes are formed between a predetermined range of width of the top land from face of the head portion of the piston. This configuration ensures improved sealing between the piston rings and block, since the combustion gases exert a net downward and outward pushing force on backside of the piston rings with decreased tangential load which pushes the piston rings against the block. The combustion gases from a combustion chamber are channelized towards an inclined gas ports. Thus, this configuration provides sufficient radial pressure to be exerted between the block and the pistons rings which decreases the need of fixed tangential load continuously in the piston assembly. This configuration decreases the FMEP (friction mean effective pressure) loss, emission and increases fuel economy in the vehicle. This configuration also enhances durability of the piston rings. More precisely, this configuration provides variable tangential load that is the tangential force gradually increases from lower RPM to higher RPM of engine (engine operating parameter), as per the requirement, thereby reducing frictional loss.

[00026] Further "front" and "rear", and "left" and "right" referred to in the ensuing description of the illustrated embodiment refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the vehicle and looking forward.

[00027] The present invention is now described briefly in connection with the rendered drawings. It should be noted that like elements are denoted by the same reference numerals throughout the description. The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof. [00029] Fig. 1 is an exploded view of a piston assembly as per one embodiment of the present invention. As per one embodiment of the present invention, the piston assembly includes head portion a piston (105) having a head portion (107), a piston pin (106), a pair of attachment means (104a, 104b), one or more piston ring (101, 102, and 103). The one or more piston ring restricts the combustion gas from channelizing into a crankcase of an engine. The piston pin (106) connects the piston to a connecting rod (not shown) and provides a bearing for the connecting rod to pivot upon as per the movement of the piston. Further, the connecting rod converts reciprocating motion of the piston into rotation of a crankshaft (not shown). The crankshaft includes a rectangular pocket. The rectangular pocket reduces volume occupied by the component; hence, ensuring reduction of mass of the crankshaft by the relation that mass is equal to product of density and volume. Thus the reduction in volume leads to reduction of the mass of the component, thereby reducing the mass of the crankshaft. [00028] Fig. la is an assembled view of a piston assembly as per one embodiment. The piston assembly further includes a top land (109), a second land (111), a third land (113), a first piston ring groove (108), a second piston ring groove (112), where the one or more groove is axially spaced with each other, a piston skirt (114) and one or more gas port (110). The one or more ring groove is configured to receive one or more piston ring in the piston assembly. As per one embodiment of the present invention, the top land (109 ) is formed between the head portion (101) and second land (111 ). The third land (113 ) is an oil control ring which scraps the oil from a cylinder wall, when the piston assembly is on a power or exhaust stroke. As per one embodiment of the present invention, one or more gas port (110) (as shown in fig. la) is disposed on the top land (109 ) of the piston assembly (100) and is angularly disposed along the circumference of the top land 109 equidistance from each other. The one or more ring is disposed between the piston skirt and the head portion of the piston assembly.

[00029] Fig. lb is a sectional view of the piston (105) as per one embodiment of the present invention. The one or more gas port is angularly/inclinedly disposed circumferentially on the top land at a predetermined angle A, where predetermined angle A is in range of 10-80 degree with respect to mid plane sliding axis (YY’) of the piston assembly (100). More than 80 degree and less than degree leads to clogging of one or more gas port (100) with carbon, thus affecting efficiency of the one or more gas port. The one or more gas port (110) is formed with a diameter D1 in predetermined range of 0.5mm to 2mm to channelize combustion gas inside the piston ring grooves. More than 2mm or less than 0.5mm impacts channelizing of the combustion gases in the piston ring grooves. As per one embodiment of the present invention, the one or more gas port (110) includes two ends where one end (110a) is in communication with a crevice volume (V) (as shown in fig. lc) formed between the piston assembly (100) and a wall of cylinder block (shown with dotted line) and another end (110b) is in communication with first piston ring groove (108), thus, ensuring channelizing of combustion gases into one or more rings of the piston assembly.

[00030] As per one embodiment of the present invention, the another end (110b) of the one or more gas port (110) is disposed at a predetermined radial distance X’ from an inner diameter of the first piston ring groove (108) (as shown in fig. Id), where X’ is a radial distance of a diameter of the top land (109) from the another end (110b) of the one or more gas port (110), configured on the first piston ring groove (108) of said one or more groove (108, 112). The predetermined distance X’ is in range of 5-80% of X in a radially outward direction, where X is a distance of the top land diameter from an inner surface of the first piston ring groove. Further, as per one embodiment of the present invention, the one end (110a) of one or more gas port (110) is disposed at a predetermined distance B with respect to height (H) of the top land from top surface of the first piston ring groove (108). The predetermined distance B is in the range of 10-90% of H. More than 90% and less than 10% impacts the efficiency of the one or more gas port (110) as disposed in the piston assembly.

[00031] A per one embodiment of the present invention, combustion gases from combustion chamber enters backside of one or more piston rings (101, 102, and 103) (as shown in fig. 1), through one or more inclinedly disposed gas port (110) and pushes the rings against the block (shown with dotted line), thereby, exerting a radial force between the one or more piston rings and the block. Hence, this configuration decreases the requirement of fixed/high tangential load of the one or more piston ring. In case, when the engine rpm is less, the tangential load applied by one or more piston ring is less and subsequently, when the rpm of the power unit is more, the additional tangential load as required is fulfilled by the gas which channelizes through the one or more gas port inside the inner periphery of the one or more piston ring, leading to thrusting the ring radially outwards thereby, providing tangential load as per the requirement depending upon the engine parameter. Thus, this reduces the requirement of high tangential load of the one or more piston rings which results in reduction of friction as generated between the one or more piston rings and the block. An inertia disc is disposed at right side of magneto rotor, left side of LH crankshaft web and at centre of stem of the LH crankshaft to reduce ideal rpm of the engine, thus ensuring reduction of vibration due to power stroke. More precisely, the friction between the one or more piston ring and the block and the tangential load exerted by the one or more piston ring is related by F =mN , where m is the coefficient of friction between the piston rings and the block & N is the radial outward contact thrust force exerted by the rings against the block i.e the piston rings tangential load. Hence, by reducing the tangential load, the friction between piston rings and block is also reduced. Thus, ensuring improved fuel economy ratio, reduced FMEPloss and better emission. This also improves the durability of the piston assembly. In another implementation, the piston skirt (114) is provided with one or more grooves disposed circumferentially along length of the piston skirt. The one or more grooves are provided with depth to hold the oil for lubricating components to reduce the friction between the components. As per one embodiment of the present invention, the combustion gases exert a net downward and outward pushing force on backside of the one or more piston ring with reduced tangential force. The gases channelizes through the one or more inclinedly disposed gas port pushes the one or more ring against the block, thus, ensuring improved sealing of the gases while reducing the friction between the one or more rings and the block resulting in less blowby losses (as shown in fig. 4). Thereby, this configuration ensures improved sealing with reduced tangential load, thus reducing friction by reducing requirement of the generation of inherent pressure through expansion of one or more piston ring.

[00032] Fig. 2 is a sectional view of piston assembly with one or more gas port as per another embodiment of the present invention. As per another embodiment of the present invention, the one or more gas port is angularly/inclinedly disposed circumferentially on the second land at a predetermined angle A, where predetermined angle A is in range of 10-80 degree with respect to mid plane sliding axis (YY’) of the piston assembly (100). More than 80 degree and less than degree leads to clogging of one or more gas port (100) with carbon, which affects efficiency of the one or more gas port. The one or more gas port (110) is formed with a diameter D2 in predetermined range of 0.5mm to 2mm to channelize combustion gas inside the piston ring grooves. More than 2mm or less than 0.5mm impacts channelizing of the combustion gases in the one or more piston ring groove. As per one embodiment of the present invention, the one or more gas port (110) includes two ends where one end (110a) is in communication with a crevice volume (V) (as shown in fig. lc) formed between the piston assembly (100) and a wall of cylinder block (shown with dotted line) and another end (110b) is communication with second piston ring groove (108), thus, ensuring channelizing of combustion gases into one or more rings of the piston assembly.

[00033] As per one embodiment of the present invention, the another end (110b) of one or more gas port (110) is disposed at a predetermined distance X’ from an inner diameter of the second piston ring groove (112) (as shown in fig. 2a), where X’ is a radial distance of a diameter of the second land (111) from the another end (110b) of the one or more gas port (110), configured on the second piston ring groove (112) of said one or more groove (108, 112). The predetermined distance X’ is in range of 5-80% of X, where X distance of the second land diameter from an inner surface of second piston ring groove. Further, as per one embodiment of the present invention, the one end (110a) of the one or more gas port (110) is disposed at a predetermined distance B with respect to height (H) of the second land from top surface of the second piston ring groove (108). The predetermined distance B is in the range of 10-90% of H. More than 90% and less than 10% impacts the efficiency of the one or more gas port (110) as disposed in the piston assembly.

[00034] Fig. 3 is a sectional view of piston assembly with one or more gas port as per another embodiment of the present invention. As per one embodiment of the present invention, the one or more gas port is formed on top land surface and a second land surface for channelizing combustion gas into the one or more piston ring.

[00035] This configuration improves sealing of the combustion gases in the one or more piston ring with reduced tangential load as the combustion gases are directly channelize to the one or more piston ring through the one or more gas port in the piston assembly to regular the thrust force exerted by the piston ring thereby controlling the sealing tangential force depending on the engine speed which results in reduced friction also and related loss also.

[00036] This configuration also improves sealing of the gases in the one or more piston ring groove without undesirably increasing the tangential load of the one or more piston rings

[00037] The invention helps in overcoming the problem of increased friction between the piston assembly and the block. It also ensures improved sealing of the combustion gas from going into the crankcase while reducing friction between the components in a controlled manner.

[00038] Advantageously, the embodiments of the present invention, describes the potential modifications in the configuration of the one or more gas ports in the piston assembly.

[00039] Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention.

List of reference symbol:

Fig. 1:

100; Piston Assembly 107: Head portion 105: Piston

106: Piston Pin

104a, 104b: A pair of attachment means 101, 102, 103: One or more piston ring

Fig. la: 109: Top Land

111: Second Land 113: Third land 108: A first Piston Groove 112: A second piston groove 114: Piston Skirt

110: One or more gas port Fig. lb:

A: Predetermined Angle YY’ : Mid Plane Sliding Axis Dl: Diameter 110a: one end

110b: another end V: Crevice Volume

Fig. Id: X’ : Distance of another end of the one or more gas port

X: Predetermined distance B: Predetermined Distance