JP2008057671A - Piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain abrasion of a sliding surface by uniformizing bearing pressure in the peripheral direction, while securing the stable gas seal function, regardless of an operation state of an internal combustion engine, in a piston ring. <P>SOLUTION: Ring grooves 44, 45 and 46 are formed on an outer peripheral surface of a piston 14. A top ring 51, a second ring 52 and an oil ring 53 are fitted to these ring grooves 44, 45 and 46. In this top ring 51, inner peripheral parts 57a and 57b are formed of a material having a thermal expansion coefficient higher than outer peripheral parts 56a and 56b in an intermediate area B in the peripheral direction except for abutment end part areas A1 and A2 having the predetermined length in the peripheral direction from abutment end surfaces 51a and 51b opposed with an abutment clearance S. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piston ring mounted in a ring groove formed on an outer peripheral surface of a piston used for an internal combustion engine.

  In general, in an internal combustion engine, a cylinder head is assembled to an upper portion of a cylinder block and fastened by a plurality of fastening bolts. A plurality of cylinder bores are provided in series, and a piston is supported on each cylinder bore so as to be movable up and down. Has been. An intake port and an exhaust port are formed to face each combustion chamber defined by the cylinder head, the cylinder block, and the piston, and the intake port and the exhaust port can be opened and closed by an intake valve and an exhaust valve. In addition, an injector that injects fuel into the intake port (or the combustion chamber) is mounted, and an ignition plug that ignites the air-fuel mixture in the combustion chamber is mounted.

  Therefore, when the intake valve is opened, air is sucked into the combustion chamber from the intake port, fuel injected from the injector is sucked into the combustion chamber, and the air-fuel mixture is compressed by the piston rising, The high-pressure air-fuel mixture is led to the spark plug, ignites and explodes, so that driving force can be obtained. When the exhaust valve is opened, the exhaust gas after combustion is discharged from the exhaust port.

  In the internal combustion engine described above, a plurality of piston rings are mounted on the outer peripheral portion of the piston. A pressure ring such as a top ring and a second ring mounted on the upper side has a gas sealing function and a heat conduction function, and an oil ring mounted on the lower side has an oil control function. That is, the gas seal function ensures the confidentiality of the combustion chamber in the intake, compression, expansion, and exhaust strokes of the internal combustion engine, and in particular, the piston lowers due to the expansion of the combustion gas in the combustion chamber. At this time, the piston ring is in contact with the wall surface of the cylinder bore to ensure confidentiality so that the combustion gas does not leak into the crankcase through the gap between the cylinder bore and the piston. Further, the heat conduction function is to ensure the performance of the piston and the piston ring by releasing the heat of the piston to the cylinder bore side when the piston ring comes into contact with the wall surface of the cylinder bore. Further, the oil control function is to leave a minimum amount of lubricating oil on the wall surface of the cylinder bore and scrape and collect excess lubricating oil.

  By the way, the exhaust gas (blow-by gas) generated after combustion in the combustion chamber contains NOx (nitrogen oxide), HC (hydrocarbon), CO (carbon monoxide) and the like which are harmful components. The piston ring prevents this exhaust gas from leaking into the crankcase. In this case, the top ring and the second ring have their outer peripheral surface in contact with the wall surface of the cylinder bore by their own elastic force to ensure confidentiality and prevent leakage of exhaust gas from the combustion chamber into the crankcase.

  However, when the internal combustion engine is in a high rotation and high load state, the pressure and temperature of the exhaust gas in the combustion chamber are further increased and the cylinder bore is thermally expanded, but the followability to the top ring and the second ring is reduced. The confidentiality between the outer peripheral surface of the cylinder and the wall surface of the cylinder bore is lowered, and the leakage of exhaust gas from the combustion chamber into the crankcase cannot be sufficiently prevented.

  For solving such problems, for example, there are those described in Patent Documents 1 to 6 below. The piston ring of the engine described in Patent Document 1 is composed of a metal whose outer peripheral portion has a low coefficient of thermal expansion and whose inner peripheral portion has a high coefficient of thermal expansion. In addition, the piston ring described in Patent Document 2 has an inner metal made of a metal having a high thermal expansion coefficient integrated with an outer ring made of a heat-resistant and wear-resistant metal provided in contact with the inner diameter wall of the cylinder. It is a combination. The piston ring described in Patent Document 3 has a thickness that is thicker on the opposite side of the joint, and the other portions are thinner than the thickness on the opposite side of the joint. The piston ring of the internal combustion engine described in Patent Document 4 is provided with an unbalanced force generating mechanism that unbalances the surface pressure acting radially outward in the circumferential direction. The piston ring of the internal combustion engine described in Patent Document 5 has a back ring coupled to the inner peripheral surface of the ring body, and the expansion coefficient of the buck ring is larger than the expansion coefficient of the ring body. In the combination piston ring described in Patent Document 6, a resin ring made of an intermediate resin ring and an inner peripheral resin ring is fixed inside the metal ring, and the temperature at which the joint abuts between the intermediate resin ring and the inner peripheral resin ring is different. Is.

Japanese Patent Laid-Open No. 06-066371 Japanese Patent Laid-Open No. 61-136060 Japanese Utility Model Publication No. 56-015437 Japanese Utility Model Publication No. 62-084648 Japanese Utility Model Publication No. 55-139242 JP 2004-116648 A

  By the way, when the piston ring is installed in the ring groove of the piston, it is necessary to push the inner diameter so as to be larger than the outer diameter of the piston. Also, the piston ring is installed in the piston ring groove and installed in the cylinder. After that, in order to achieve close contact with the cylinder inner wall by generating tension on the cylinder inner wall, a cut called a joint is provided at one place. This joint has a role of absorbing a difference in thermal expansion between a low temperature and a high temperature. Therefore, the surface pressure distribution in the circumferential direction of the piston ring, that is, the surface pressure at which the outer peripheral surface of the piston ring presses the wall surface of the cylinder bore is highest in the vicinity of the joint end in the circumferential direction.

  And if the outer peripheral part is made of a metal having a low coefficient of thermal expansion and the inner peripheral part is made of a metal having a high coefficient of thermal expansion, like the piston ring of the engine of Patent Document 1 described above, the inner circumference is made to the outer peripheral part at high temperatures Since the portion expands greatly, the surface pressure of the entire piston ring increases, and the surface pressure at the abutment end portion increases locally. Then, when the piston moves up and down, the sliding resistance between the joint end of the piston ring and the wall surface of the cylinder bore is locally increased, and the joint end of the piston ring and the wall surface of the cylinder bore are locally worn. There is a problem that the consumption of lubricating oil increases or the amount of exhaust gas that leaks from the combustion chamber into the crankcase increases, resulting in worse fuel consumption, lower output, degraded lubricating oil, increased noise, etc. is there.

  Further, as described above, even if the piston ring is made of different materials on the inner side and the outer side as in Patent Documents 2 to 6 described above, as described above, the surface pressure of the entire stone ring is low and low. The surface pressure at the end of the abutment increases, and the amount of lubricating oil consumed increases or the amount of exhaust gas leakage increases with local wear.

  The present invention is for solving such a problem, and ensures a stable gas seal function regardless of the operating state of the internal combustion engine and reduces the surface pressure in the vicinity of the joint portion to reduce the surface pressure in the circumferential direction. An object of the present invention is to provide a piston ring that can suppress wear of a sliding surface by making the thickness uniform.

  In order to solve the above-described problems and achieve the object, the piston ring of the present invention has a substantially circular shape that is fitted in a ring groove formed on the outer peripheral surface of a piston for an internal combustion engine, and slides relative to the cylinder. A piston ring having an outer peripheral surface, an inner peripheral surface facing the piston, an upper surface, and a lower surface, and including a single abutment portion that divides the substantially circular shape in the radial direction, and is predetermined along the circumferential direction from the abutment end surface In the intermediate region in the circumferential direction excluding the abutting end region having a length, the inner peripheral portion is formed of a material having a higher thermal expansion coefficient than the outer peripheral portion.

  In the piston ring of the present invention, the intermediate region is characterized in that an outer peripheral portion is formed of a low thermal expansion material and an inner peripheral portion is formed of a high thermal expansion material.

  In the piston ring of the present invention, the abutment end region is characterized in that an outer peripheral portion is formed of a high thermal expansion material and an inner peripheral portion is formed of a low thermal expansion material.

  In the piston ring of the present invention, the abutment end region has an outer peripheral portion formed of a low thermal expansion material, an inner peripheral portion formed of a high thermal expansion material, and a low thermal expansion of the outer peripheral portion toward the abutment end surface. While the thickness of the material increases linearly or curvedly, the thickness of the high thermal expansion material in the inner peripheral portion decreases.

  In the piston ring of the present invention, the joint end region is formed of the same low thermal expansion material as the outer peripheral portion of the outer peripheral portion in the intermediate region, and the inner peripheral portion has a higher thermal expansion coefficient than the low thermal expansion material. The intermediate region is formed of a medium thermal expansion material having a lower coefficient of thermal expansion than that of the high thermal expansion material in the inner peripheral portion.

  In the piston ring of the present invention, the intermediate region is formed such that the thickness of the low thermal expansion material in the outer peripheral portion is the same as the thickness of the high thermal expansion material in the inner peripheral portion, and is opposed to the joint portion in the intermediate region in the radial direction. The abutment facing region is characterized in that the thickness of the high thermal expansion material in the inner peripheral portion is formed thinner than the thickness of the low thermal expansion material in the outer peripheral portion.

  According to the piston ring of the present invention, the piston ring for the internal combustion engine has a substantially circular shape that is attached to the ring groove formed on the outer peripheral surface of the internal combustion engine, and the outer peripheral surface that slides with respect to the cylinder and the inner peripheral surface that faces the piston. An intermediate region in the circumferential direction, excluding the abutment end region having a predetermined length along the circumferential direction from the abutment end surface, comprising an abutment portion that is composed of an upper surface and a lower surface and divides a substantially circular shape in the radial direction. Since the inner peripheral portion is made of a material having a higher thermal expansion coefficient than the outer peripheral portion, the inner peripheral portion expands more than the outer peripheral portion in the intermediate region at a high temperature, so that the tension in the intermediate region becomes higher. However, in the abutment end region, there is no difference in expansion between the outer peripheral portion and the inner peripheral portion, the tension in the abutment end portion region does not change, the surface pressure in the circumferential direction can be made uniform, and the piston can move up and down. Sometimes the abutting end of the piston ring The sliding resistance between the cylinder bore and the wall surface of the cylinder bore is not locally increased, and wear of sliding surfaces such as the joint end portion of the piston ring and the wall surface of the cylinder bore can be suppressed. Therefore, a stable gas sealing function can be secured.

  Hereinafter, embodiments of the piston ring according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a plan view showing a top ring as a piston ring according to a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1 is a cross-sectional view taken along the line III-III in FIG. 1 showing the mounting state of the top ring of the first embodiment, FIG. 4 is a schematic diagram showing the surface pressure distribution in the top ring of the first embodiment, and FIG. FIG. 6 is a cross-sectional view of the main part of the piston to which the piston ring is attached.

  The internal combustion engine of the first embodiment is a multi-cylinder engine. As shown in FIG. 5, the cylinder head 11 is assembled on a cylinder block 12 and fastened by a plurality of fastening bolts (not shown). A plurality of cylinder bores 13 are formed in the cylinder block 12, and a piston 14 is slidably fitted to each cylinder bore 13. A crankshaft (not shown) is rotatably supported at the lower part of the cylinder block 12, and each piston 14 is connected to the crankshaft via a connecting rod 15.

  Corresponding to each cylinder bore 13 of the cylinder block 12, a combustion chamber 16 is formed in series above it. The combustion chamber 16 is surrounded by the inner wall surface of the cylinder bore 13, the lower surface of the cylinder head 11, and the top surface of the piston 14, and is inclined so that the central portion of the ceiling portion (lower surface of the cylinder head 11) is higher. It has a pent roof shape. An intake port 17 and an exhaust port 18 are opened above each combustion chamber 16, that is, on the lower surface of the cylinder head 11.

  An intake valve 19 and an exhaust valve 20 are positioned with respect to the intake port 17 and the exhaust port 18, respectively. The intake valve 19 and the exhaust valve 20 are supported by the stem guides 21 and 22 fixed to the cylinder head 11 so as to be movable in the axial direction. 17 and the exhaust port 18 are supported in a biasing direction. Further, the intake valve 19 and the exhaust valve 20 are connected to upper end portions of one end of roller rocker arms 25 and 26, and the other end portions of the roller rocker arms 25 and 26 are connected to lash adjusters 27 and 28 fixed to the cylinder head 11. The intake camshaft 29 has an intake cam 30 and the exhaust camshaft 31 has an exhaust cam 32 in contact with the roller rocker arms 25 and 26.

  Therefore, when the intake camshaft 29 and the exhaust camshaft 31 rotate in synchronization with the engine, the intake cam 30 and the exhaust cam 32 actuate the roller rocker arms 25 and 26, and the intake valves 19 and the exhaust valves 20 are moved at a predetermined timing. By moving up and down, the intake port 17 and the exhaust port 18 can be opened and closed, and the intake port 17 and the combustion chamber 16 and the combustion chamber 16 and the exhaust port 18 can communicate with each other.

  An injector 33 that directly injects fuel into the combustion chamber 16 is mounted on the side of the combustion chamber 16, that is, on the lower surface of the cylinder head 11 on the intake port 17 side. An ignition plug 34 is attached to the center of the ceiling of the combustion chamber 16, that is, the lower surface of the cylinder head 11 between the intake port 17 and the exhaust port 18. The vehicle is equipped with an electronic control unit (ECU), which can control the fuel injection amount and injection timing of the injector 33, the ignition timing by the spark plug 34, and the like. A fuel injection amount, an injection timing, an ignition timing, and the like are determined based on an engine operation state such as an air amount, a throttle opening (accelerator opening), and an engine speed.

  Further, as shown in FIGS. 5 and 6, the piston 14 described above is configured by mounting three piston rings 51, 52, 53 on the outer peripheral surface 42 of the piston main body 41. The piston body 41 has a cylindrical shape having an outer diameter slightly smaller than the inner diameter of the cylinder bore 13, and the outer peripheral surface 42 has a predetermined clearance from the inner wall surface of the cylinder bore 13. The piston main body 41 has a top surface 43 that defines the combustion chamber 16 at the top.

  The piston main body 41 has three ring grooves 44, 45, and 46 having a predetermined depth along the circumferential direction on the outer peripheral surface, and are formed at predetermined intervals in the vertical direction. Each ring groove 44, 45, 46 is provided with a top ring 51, a second ring 52, and an oil ring 53 as piston rings, and the outer peripheral surface 42 is a top land 42a, a second land 42b, and a third land 42c. It is partitioned.

  In this case, the top ring 51 and the second ring 52 located on the top surface 43 side of the piston main body 41 have a gas sealing function and a heat conduction function. That is, the top ring 51 and the second ring 52 can secure the confidentiality of the combustion chamber 16 in the intake, compression, expansion, and exhaust strokes of the engine, and in particular, the piston is caused by the expansion of the combustion gas in the combustion chamber 16. 14 descends under pressure, but the top ring 51 and the second ring 52 come into contact with the wall surface of the cylinder bore 13 with tension so that the exhaust gas does not leak into the crankcase through the gap between the piston 14 and the cylinder bore 13. It is functioning. Further, the top ring 51 and the second ring 52 have their outer peripheral surfaces in contact with the wall surface of the cylinder bore 13 so that the heat of the piston 14 is released to the cylinder bore 13 side and the performance of the piston 14, the top ring 51 and the second ring 52 is ensured. Can do.

  Further, the second ring 52 and the oil ring 53 mounted on the lower side of the second ring 52 have an outer peripheral surface in contact with the wall surface of the cylinder bore 13, so that the lubricating oil adhering to the wall surface of the cylinder bore 13 is scraped off when the piston 14 is lowered. A minimum amount of lubricating oil can be left on the wall surface of the cylinder bore 13 to recover excess lubricating oil.

  By the way, in the high rotation high load state of the internal combustion engine, the pressure and temperature of the combustion gas in the combustion chamber 16 are further increased and the cylinder bore 13 is thermally expanded, while the top ring 51 and the second ring 52 follow the cylinder bore 13. As a result, the tension is lowered and the leakage of exhaust gas from the combustion chamber 16 into the crankcase cannot be sufficiently prevented.

  Further, when the top ring 51 and the second ring 52 are mounted in the ring grooves 44 and 45 of the piston 14, it is necessary to expand the inner diameter of the piston 14 so that the inner diameter is once larger than the outer diameter of the piston 14. After being installed in the grooves 44 and 45 and installed in the cylinder, a tension is generated on the inner wall of the cylinder bore 13 so as to be in close contact with the inner wall of the cylinder. . In this joint, a joint gap is provided in order to absorb the difference in thermal expansion between the low temperature and the high temperature. Therefore, when the top ring 51 and the second ring 52 are mounted in the ring grooves 44 and 45 of the piston 14, the surface pressure distribution in the circumferential direction, that is, the surface pressure at which the outer peripheral surface presses the wall surface of the cylinder bore 13 is Thus, the vicinity of the abutment end is the highest. Then, when the piston 14 moves up and down, the sliding resistance between the outer peripheral surfaces of the top ring 51 and the second ring 52 and the wall surface of the cylinder bore 13 is locally increased, and these sliding surfaces are worn, It will cause problems.

  Therefore, in this embodiment, as shown in FIG. 1 to FIG. 3, each abutment end region A <b> 1, A <b> 2 having a predetermined length along the circumferential direction from the abutment end surface facing the abutment gap S at the top ring 51. In the intermediate region B in the circumferential direction excluding the outer peripheral portion, the inner peripheral portion is formed of a material having a higher coefficient of thermal expansion than the outer peripheral portion.

  Specifically, the top ring 51 is provided with two joint end regions A1 and A2 having a predetermined length along the circumferential direction from the joint end faces 51a and 51b facing each other with the joint gap S. An intermediate region B having a predetermined length is provided along the circumferential direction excluding the end regions A1 and A2. In the intermediate region B, the outer peripheral portion 54 is formed of a low thermal expansion material, and the inner peripheral portion 55 is formed of a high thermal expansion material. Moreover, in each joint end part area | region A1, A2, outer peripheral part 56a, 56b is formed with the high thermal expansion material, and inner peripheral part 57a, 57b is formed with the low thermal expansion material.

  In this case, the high thermal expansion material is made of, for example, manganese (Mn), nickel (Ni), or copper (Cu) alloy, and the low thermal expansion material is made of iron (Fe) or nickel (Ni) alloy. The outer peripheral portion 54 and the inner peripheral portion 55 in the intermediate region B, and the outer peripheral portions 56a and 56b and the inner peripheral portions 57a and 57b in the joint end region A1 and A2 are bonded together with welding, pressure bonding, or adhesive, respectively. Yes. Further, the outer peripheral portion 54 and the inner peripheral portion 55 in the intermediate region B, and the outer peripheral portions 56a and 56b and the inner peripheral portions 57a and 57b in the joint end portion regions A1 and A2 are welded or crimped, or adhesive, brazing, Bonded together with mechanical bonding.

  Therefore, in a low temperature state, the piston ring of the conventional example in which the outer peripheral portion is simply formed of the low thermal expansion material and the inner peripheral portion is formed of the high thermal expansion material, and the outer peripheral portion 54 in the intermediate region B is formed of the low thermal expansion material. In the first embodiment, the peripheral portion 55 is formed of a high thermal expansion material, the outer peripheral portions 56a and 56b in the joint end regions A1 and A2 are formed of a high thermal expansion material, and the inner peripheral portions 57a and 57b are formed of a low thermal expansion material. In the top ring 51, the tension (surface pressure received from the cylinder bore, hereinafter simply referred to as surface pressure) at the abutting end portion facing with the abutting gap S is locally larger than the tension (surface pressure) in other portions. ing.

  However, in the operating state of the internal combustion engine, the piston ring is heated by the combustion gas, and the end of the abutment is in a high temperature state exposed to the high temperature combustion gas. As indicated by the dotted line in FIG. 4, the inner peripheral portion expands larger than the outer peripheral portion, so that the tension (surface pressure) at the end of the joint facing the joint gap S is greater than the tension (surface pressure) at the other portion. Will become even larger. On the other hand, in the top ring 51 of the first embodiment, as shown by a one-dot chain line in FIG. 4, the inner peripheral portion 55 expands larger than the outer peripheral portion 54 in the intermediate region B, but it is opposite in the joint end region A1, A2. Since the outer peripheral portions 56a and 56b expand greatly compared to the inner peripheral portions 57a and 57b, the tension (surface pressure) of the joint end regions A1 and A2 is suppressed, and the joint end regions A1 and A2 are suppressed. In addition, the tension (surface pressure) in all regions including the intermediate region B is made uniform in the circumferential direction.

  Here, the operation of the internal combustion engine having the piston ring of this embodiment will be described.

  As shown in FIG. 5, when the engine is operated, the piston 14 rises and the air-fuel mixture in the combustion chamber 16 is compressed, and the high-pressure air-fuel mixture is ignited to expand and explode. The exhaust gas contains NOx, HC, and CO, which are harmful components. Therefore, when the piston 14 moves up and down, the top ring 51 and the second ring 52 mounted on the outer peripheral surface of the piston 14 are in sliding contact with the inner wall surface of the cylinder bore 13, so that the exhaust gas in the combustion chamber 16 is separated from the piston 14 and the cylinder bore 13. It is possible to prevent leakage into the crankcase through the gap.

  In the present embodiment, the top ring 51 has the outer peripheral portion 54 of the intermediate region B formed of a low thermal expansion material and the inner peripheral portion 55 formed of a high thermal expansion material, while the outer periphery of the joint end region A1, A2 is formed. The portions 56a and 56b are formed of a high thermal expansion material, and the inner peripheral portions 57a and 57b are formed of a low thermal expansion material. Therefore, when the top ring 51 is in a high temperature state, in the intermediate region B, the inner peripheral portion 55 expands more than the outer peripheral portion 54, so that the tension in the intermediate region B increases, but the abutment end region A1. , A2 on the contrary, the outer peripheral portions 56a, 56b expand larger than the inner peripheral portions 57a, 57b, so that the tension in the joint end regions A1, A2 does not increase.

  Therefore, the surface pressure of the top ring 51 in the circumferential direction is made uniform, and the sliding resistance between the joint end of the top ring 51 and the wall surface of the cylinder bore 13 is locally increased when the piston 14 moves up and down. This prevents the exhaust gas in the combustion chamber 16 from leaking into the crankcase through the gap between the piston 14 and the cylinder bore 13. As a result, the amount of exhaust gas leaking from the combustion chamber 16 through the joint gap S to the crankcase is reduced, so that deterioration of lubricating oil stored in an oil pan (not shown) is suppressed.

  As described above, in the piston ring of the first embodiment, the ring grooves 44, 45 and 46 shown in FIG. 6 are formed on the outer peripheral surface of the piston 14, and the top ring 51 and the second ring are formed in the ring grooves 44, 45 and 46, respectively. 52, an oil ring 53 is mounted, and in this top ring 51 in the circumferential direction excluding the joint end regions A1 and A2 having a predetermined length along the circumferential direction from the joint end faces 51a and 51b facing each other with the joint gap S. In the intermediate region B, the inner peripheral portions 57a and 57b are formed of a material having a higher thermal expansion coefficient than the outer peripheral portions 56a and 56b.

  Therefore, at the high temperature, in the intermediate region B, the inner peripheral portion 55 expands more than the outer peripheral portion 54, so that the tension in the intermediate region B is increased, but in the joint end region A1, A2, the inner peripheral portion Since the outer peripheral portions 56a and 56b expand greatly compared to 57a and 57b, the tension at the joint end regions A1 and A2 is not increased, and the surface pressure in the circumferential direction can be made uniform, and the piston 14 During the vertical movement, the sliding resistance between the end of the top ring 51 and the wall surface of the cylinder bore 13 does not increase locally, and wear of the sliding surface such as the joint end of the top ring 51 and the wall surface of the cylinder bore 13 does not occur. Can be suppressed.

  Further, in the first embodiment, the top ring 51 is in the intermediate region B, and the inner peripheral portion 55 expands greatly with respect to the outer peripheral portion 54 as the temperature rises. As a result, the amount of exhaust gas leaking from the combustion chamber 16 through the joint gap S to the crankcase can be reliably reduced even in a high engine load region, and a stable gas sealing function can be achieved regardless of the operating state of the engine. Can be secured.

  FIG. 7 is a plan view of an essential part showing a top ring as a piston ring according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the second embodiment, as shown in FIG. 7, the top ring 61 has an outer peripheral portion 62 formed of a low thermal expansion material, an inner peripheral portion 63 formed of a high thermal expansion material, and the joint end surfaces 61a and 61b on the joint gap S side. The thickness of the low thermal expansion material in the outer peripheral portion 62 increases while the thickness of the high thermal expansion material in the inner peripheral portion 63 decreases.

  That is, as for the top ring 61, the outer peripheral part 62 is formed with the low thermal expansion material, and the inner peripheral part 63 is formed with the high thermal expansion material. The top ring 61 has two abutment end regions A1 and A2 having a predetermined length along the circumferential direction from the abutment end surfaces 61a and 61b facing each other with the abutment gap S, and the abutment end region A1. , A2 having a predetermined length along the circumferential direction except A2. In the intermediate region B, the thickness D1 of the outer peripheral portion 62 formed of the low thermal expansion material and the thickness D2 of the inner peripheral portion 63 formed of the high thermal expansion material are set to the same thickness. On the other hand, in the joint end regions A1 and A2, the thickness D1 of the outer peripheral portion 62 formed of the low thermal expansion material increases toward the joint end surfaces 61a and 61b, while the inner peripheral portion 63 formed of the high thermal expansion material. The thickness D2 decreases toward the joint end surfaces 61a and 61b, and the thickness D2 of the inner peripheral portion 63 at the joint end surfaces 61a and 61b is set to be substantially zero. In the abutment end regions A1 and A2, the thickness D1 of the outer peripheral portion 62 changes linearly or curvedly toward the abutment end surfaces 61a and 61b, while the thickness of the inner peripheral portion 63 is increased. It is desirable to form so that D2 changes so as to decrease linearly or curvedly toward the joint end surfaces 61a and 61b.

  For this reason, in the top ring 61 of the present embodiment, in a low temperature state, the tension (surface pressure) at the end of the abutment portion facing with the abutment gap S is locally greater than the tension (surface pressure) at the other portion. However, in the high temperature state, the inner peripheral portion 63 expands more than the outer peripheral portion 62, but in the joint end regions A1 and A2, the thickness D2 of the inner peripheral portion 63 formed of a high thermal expansion material is the joint. Since the amount of expansion decreases toward the end surfaces 61a and 61b, the amount of expansion decreases toward the joint end surfaces 61a and 61b, and the surface pressure of the joint end regions A1 and A2 is smaller than the surface pressure of the intermediate region B. As a result, the surface pressure in all the regions including the joint end regions A1 and A2 and the intermediate region B is made uniform in the circumferential direction.

  Therefore, when the piston moves up and down, the sliding resistance between the joint end of the top ring 61 and the wall surface of the cylinder bore does not increase locally, and the exhaust gas in the combustion chamber passes through the gap between the piston and the cylinder bore, and the crankcase. It is reliably prevented from leaking into As a result, the amount of exhaust gas leaking from the crankcase through the joint gap S from the combustion chamber is reduced, so that deterioration of the lubricating oil stored in the oil pan is suppressed.

  As described above, in the piston ring of the second embodiment, the outer peripheral portion 62 is formed of the low thermal expansion material and the inner peripheral portion 63 is formed of the high thermal expansion material in the top ring 61, and the joint end surface on the joint gap S side. While increasing the thickness of the low thermal expansion material of the outer peripheral portion 62 toward the 61a and 61b, the thickness of the high thermal expansion material of the inner peripheral portion 63 is decreased. In addition, it is preferable to form the variation | change_quantity which the thickness of the low thermal expansion material of the outer peripheral part 62 increases in the shape of a curve or a straight line as it goes to the joint end surface 61a, 61b from inside the joint end part area | region A1, A2.

  Therefore, at the high temperature, in the intermediate region B, the inner peripheral portion 63 expands more than the outer peripheral portion 62, so that the tension in the intermediate region B is increased, but in the joint end region A1, A2, the inner peripheral portion Since the thickness of 63 decreases toward the joint end surfaces 61a and 61b, the amount of expansion of the inner peripheral portion 63 decreases toward the joint end surfaces 61a and 61b, and the surfaces in the joint end regions A1 and A2 The pressure does not increase, the surface pressure in the circumferential direction can be made uniform, and the sliding resistance between the end of the top ring 61 and the inner wall surface of the cylinder bore locally increases when the piston moves up and down. In addition, wear of sliding surfaces such as the joint end of the top ring 61 and the wall surface of the cylinder bore can be suppressed.

  Further, in the second embodiment, the top ring 61 has an intermediate region B in which the inner peripheral part 63 expands greatly with respect to the outer peripheral part 62 as the temperature rises. As a result, the amount of exhaust gas leaking from the combustion chamber through the joint gap S to the crankcase can be reliably reduced even in a high engine load range, and a stable gas sealing function can be achieved regardless of the operating state of the engine. Can be secured.

  FIG. 8 is a plan view illustrating a top ring as a piston ring according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In Example 3, as shown in FIG. 8, the top ring 71 has an outer peripheral portion 72 formed of a low thermal expansion material, an inner peripheral portion 73 formed of a high thermal expansion material, and the joint end surfaces 71a and 71b on the joint gap S side. While the thickness of the low thermal expansion material of the outer peripheral portion 72 increases toward the upper side, the thickness of the high thermal expansion material of the inner peripheral portion 73 decreases, and at the central portion in the circumferential direction facing the joint gap S in the radial direction. The inner peripheral portion 73 is formed thinner than the outer peripheral portion 72.

  That is, as for the top ring 71, the outer peripheral part 72 is formed with the low thermal expansion material, and the inner peripheral part 73 is formed with the high thermal expansion material. The top ring 71 has two abutment end regions A1 and A2 having a predetermined length along the circumferential direction from the abutment end surfaces 71a and 71b facing each other with the abutment gap S, and the abutment end region A1. , A2 has an intermediate region B having a predetermined length along the circumferential direction except for A2, and is opposed to the joint gap S having a predetermined length along the circumferential direction at a position facing the joint gap S in the intermediate region B in the radial direction. Area C is set. In the intermediate region B excluding the joint facing region C, the thickness D1 of the outer peripheral portion 72 formed of the low thermal expansion material and the thickness D2 of the inner peripheral portion 73 formed of the high thermal expansion material are set to the same thickness. Has been. On the other hand, in the joint end regions A1 and A2, the thickness D1 of the outer peripheral portion 72 formed of the low thermal expansion material increases toward the joint end surfaces 71a and 71b, while the inner peripheral portion 73 formed of the high thermal expansion material. The thickness D2 decreases toward the abutting end surfaces 71a and 71b, and the thickness D2 of the inner peripheral portion 73 at the abutting end surfaces 71a and 71b is substantially zero. Further, in the abutting facing region C, the thickness D2 of the inner peripheral portion 73 formed of the high thermal expansion material is set to be thinner than the thickness D1 of the outer peripheral portion 72 formed of the low thermal expansion material.

  Therefore, in the low temperature state, in the top ring 71 of the present embodiment, the tension (surface pressure) at the joint end facing the joint gap S is locally greater than the tension (surface pressure) at the other part, The tension (surface pressure) at the joint facing portion facing the joint gap S is slightly larger than the tension (surface pressure) at the other portion. However, in the high temperature state, in the top ring 71, the inner peripheral portion 73 expands more than the outer peripheral portion 72. However, in the joint end regions A1 and A2, the thickness of the inner peripheral portion 73 formed of a high thermal expansion material. Since D2 decreases toward the end surfaces 71a and 71b, the amount of expansion decreases toward the abutment end surfaces 71a and 71b, and the surface of the abutment end region A1 and A2 as compared to the surface pressure of the intermediate region B. The pressure will be reduced. Further, in the abutment facing region C, the thickness D2 of the inner peripheral portion 73 formed of the high thermal expansion material is thinner than the thickness D1 of the outer peripheral portion 72 formed of the low thermal expansion material, so that the expansion amount decreases. As a result, the surface pressure of the joint facing region C is slightly reduced compared to the surface pressure of the intermediate region B. As a result, the surface pressure in the abutment end region A1, A2 and the abutment facing region C is reduced, and the load on the abutment end region A1, A2 and the abutment facing region C can be reduced.

  Therefore, when the piston moves up and down, the sliding resistance between the joint end portion of the top ring 71 and the inner wall surface of the cylinder bore does not increase locally, and the exhaust gas in the combustion chamber passes through the gap between the piston and the cylinder bore and is cranked. Leakage into the case is reliably prevented. As a result, the amount of exhaust gas leaking from the combustion chamber through the joint gap S to the crankcase is reduced, so that deterioration of the lubricating oil stored in the oil pan is suppressed.

  Thus, in the piston ring of Example 3, the outer peripheral portion 72 is formed of a low thermal expansion material and the inner peripheral portion 73 is formed of a high thermal expansion material in the top ring 71, and the joint end surface on the joint gap S side. While increasing the thickness of the low thermal expansion material of the outer peripheral part 72 toward 71a, 71b, while reducing the thickness of the high thermal expansion material of the inner peripheral part 73, it is the circumferential direction opposite to the joint gap S in the radial direction. At the center portion, the inner peripheral portion 73 is formed thinner than the outer peripheral portion 72.

  Therefore, at the high temperature, in the intermediate region B, the inner peripheral portion 73 expands more than the outer peripheral portion 72, so that the tension in the intermediate region B is increased, but in the joint end region A1, A2, the inner peripheral portion Since the thickness of 73 decreases toward the joint end surfaces 71a and 71b, the expansion amount of the inner peripheral portion 63 decreases toward the joint end surfaces 61a and 61b, and the tension at the joint end regions A1 and A2 is high. In addition, in the abutment facing area C, since the thickness of the inner peripheral portion 73 is thinner than the thickness of the outer peripheral portion 72, the amount of expansion of the inner peripheral portion 73 is slightly reduced compared to the intermediate region B, The tension in the abutment facing area C is not so high, the tension at the high temperature in the abutment end area A1, A2 and the abutment facing area C can be reduced, and the load on the top ring 71 can be reduced. Top ring 7 The sliding resistance between the inner wall surface of the abutment end and the cylinder bore is not be higher locally, it is possible to suppress the wear of the sliding surfaces, such as walls of abutment end and the cylinder bore of the top ring 71.

  In the third embodiment, the top ring 71 has an intermediate region B in which the inner peripheral portion 73 expands greatly with respect to the outer peripheral portion 72 as the temperature rises. As a result, the amount of exhaust gas leaking from the combustion chamber through the joint gap S to the crankcase can be reliably reduced even in a high engine load range, and a stable gas sealing function can be achieved regardless of the operating state of the engine. Can be secured.

  FIG. 9 is a plan view of a principal part showing a top ring as a piston ring according to the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the Example mentioned above, and the overlapping description is abbreviate | omitted.

  In the fourth embodiment, as shown in FIG. 9, the top ring 81 has an abutment end face whose outer peripheral portion 82 is formed of a low thermal expansion material and whose inner peripheral portion 83 is formed of a high thermal expansion material, and which is opposed with an abutment gap S. In the joint end regions A1 and A2 having a predetermined length along the circumferential direction from 81a and 81b, the inner peripheral portions 84a and 84b have a higher coefficient of thermal expansion than the low thermal expansion material of the outer peripheral portion 82, and the inner peripheral portion 83 has a high thermal expansion material. It is formed of a medium thermal expansion material having a lower coefficient of thermal expansion.

  In other words, the top ring 81 has an outer peripheral portion 82 formed of a low thermal expansion material and an inner peripheral portion 83 formed of a high thermal expansion material. The top ring 81 has two abutment end regions A1 and A2 having a predetermined length along the circumferential direction from the abutment end surfaces 81a and 81b facing each other with the abutment gap S, and the abutment end region A1. , A2 having a predetermined length along the circumferential direction except A2. The inner peripheral portion 83 formed of the high thermal expansion material is provided only in the intermediate region B, and the inner peripheral portions 84a and 84b in the joint end region A1 and A2 are more thermally expanded than the low thermal expansion material of the outer peripheral portion 82. The medium thermal expansion material has a high rate and a lower thermal expansion coefficient than the high thermal expansion material of the inner peripheral portion 83.

  For this reason, in the top ring 81 of the present embodiment, in a low temperature state, the tension (surface pressure) at the joint end facing the joint gap S is locally greater than the tension (surface pressure) at other portions. However, in the high temperature state, the inner peripheral portion 83 expands more than the outer peripheral portion 82, but in the joint end regions A1 and A2, the inner peripheral portions 84a and 84b formed of the medium thermal expansion material are high thermal expansion materials. Therefore, the tension (surface pressure) of the abutment end regions A1 and A2 is reduced compared to the tension (surface pressure) of the intermediate region B, and the abutment end region A1. , A2 and intermediate region B, the tension (surface pressure) in all regions is made uniform in the circumferential direction.

  Therefore, when the piston moves up and down, the sliding resistance between the joint end of the top ring 81 and the wall surface of the cylinder bore does not increase locally, and the exhaust gas in the combustion chamber passes through the gap between the piston and the cylinder bore, and the crankcase. It is reliably prevented from leaking into As a result, the amount of exhaust gas leaking from the combustion chamber through the joint gap S to the crankcase is reduced, so that deterioration of the lubricating oil stored in the oil pan is suppressed.

  As described above, in the piston ring of the fourth embodiment, the outer peripheral portion 82 is formed of the low thermal expansion material and the inner peripheral portion 83 is formed of the high thermal expansion material at the top ring 81 and is opposed with the joint gap S. In the joint end regions A1 and A2 having a predetermined length along the circumferential direction from the joint end surfaces 81a and 81b, the inner peripheral portions 84a and 84b are higher in thermal expansion coefficient than the outer peripheral portion 82 and more than the inner peripheral portion 83. It is formed of a medium thermal expansion material having a low level.

  Therefore, at the high temperature, in the intermediate region B, the inner peripheral portion 83 expands more than the outer peripheral portion 82, so that the tension in the intermediate region B is increased, but in the joint end region A1, A2, the inner peripheral portion Since 84a and 84b are formed of a medium thermal expansion material having a higher thermal expansion coefficient than that of the outer peripheral part 82 and lower than that of the inner peripheral part 83, the expansion amount of the inner peripheral parts 84a and 84b is reduced. The surface pressure in the joint end regions A1 and A2 is not so high, and the surface pressure in the circumferential direction can be made uniform. When the piston moves up and down, the joint end portion of the top ring 81 and the inner wall surface of the cylinder bore The sliding resistance does not increase locally, and wear of sliding surfaces such as the joint end of the top ring 81 and the inner wall surface of the cylinder bore can be suppressed.

  In the fourth embodiment, the top ring 81 has an intermediate region B in which the inner peripheral portion 83 greatly expands with respect to the outer peripheral portion 82 as the temperature rises. As a result, the amount of exhaust gas leaking from the combustion chamber through the joint gap S to the crankcase can be reliably reduced even in a high engine load range, and a stable gas sealing function can be achieved regardless of the operating state of the engine. Can be secured.

  In each of the above-described embodiments, the lengths of the abutment end regions A1, A2, the intermediate region B, and the abutment facing region C are the diameters and thicknesses of the top rings 51, 61, 71, 81, the material, or the engine configuration. As a result, the surface pressure in the circumferential direction should be uniform in the temperature range to be used.

  Moreover, in each Example mentioned above, although the piston ring of this invention was applied to the top rings 51, 61, 71, 81, you may apply to a second ring.

  In each of the above-described embodiments, a cylinder injection type internal combustion engine that injects fuel directly into the combustion chamber has been described. However, the present invention can be applied to a port injection type internal combustion engine that injects fuel into an intake port. An effect can be produced.

  As described above, the piston ring according to the present invention can suppress wear of the sliding surface by achieving uniform surface pressure in the circumferential direction, and is suitable for use in any type of internal combustion engine. It is.

It is a top view showing the top ring as a piston ring which concerns on Example 1 of this invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 3 is a schematic diagram illustrating a surface pressure distribution in the top ring of Example 1. FIG. It is a longitudinal cross-sectional view of a general engine. It is principal part sectional drawing of the piston with which the piston ring was mounted | worn. It is a principal part top view showing the top ring as a piston ring which concerns on Example 2 of this invention. It is a top view showing the top ring as a piston ring which concerns on Example 3 of this invention. It is a principal part top view showing the top ring as a piston ring which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Cylinder head 12 Cylinder block 13 Cylinder bore 14 Piston 16 Combustion chamber 17 Intake port 18 Exhaust port 33 Injector 34 Spark plug 41 Piston main body 42 Outer peripheral surface 43 Top surface 44, 45, 46 Ring groove 51, 61, 71, 81 Top ring ( piston ring)
51a, 51b, 61a, 61b, 71a, 71b, 81a, 81b Abutment end face 52 Second ring (piston ring)
53 Oil ring (piston ring)
54, 56a, 56b, 62, 72, 82 Outer peripheral part 55, 57a, 57b, 63, 73, 83, 84a, 84b Inner peripheral part A1, A2 Abutment end area B Middle area C Abutment area S Abutment gap

Claims (6)

  A substantially circular shape is attached to a ring groove formed on an outer peripheral surface of a piston for an internal combustion engine, and includes an outer peripheral surface that slides on a cylinder, an inner peripheral surface that faces the piston, an upper surface, and a lower surface, In the piston ring including one abutment portion that divides the substantially circular shape in the radial direction, the inner circumference portion is an intermediate region in the circumferential direction excluding the abutment end portion region having a predetermined length along the circumferential direction from the abutment end surface. A piston ring formed of a material having a higher coefficient of thermal expansion than the outer periphery.   2. The piston ring according to claim 1, wherein the intermediate region has an outer peripheral portion formed of a low thermal expansion material and an inner peripheral portion formed of a high thermal expansion material.   The piston ring according to claim 2, wherein the abutment end region has an outer peripheral portion formed of a high thermal expansion material and an inner peripheral portion formed of a low thermal expansion material.   In the abutment end region, the outer peripheral portion is formed of a low thermal expansion material, the inner peripheral portion is formed of a high thermal expansion material, and the thickness of the low thermal expansion material of the outer peripheral portion is linear toward the abutment end surface. 3. The piston ring according to claim 2, wherein the thickness of the high thermal expansion material in the inner peripheral portion decreases while increasing in a curve.   The abutment end region has an outer peripheral portion formed of the same low thermal expansion material as the low thermal expansion material of the outer peripheral portion in the intermediate region, and the inner peripheral portion has a higher coefficient of thermal expansion than the low thermal expansion material and has an inner peripheral portion in the intermediate region. The piston ring according to claim 2, wherein the piston ring is formed of a medium thermal expansion material having a lower coefficient of thermal expansion than that of the high thermal expansion material.   The intermediate region is formed such that the thickness of the low thermal expansion material at the outer peripheral portion and the thickness of the high thermal expansion material at the inner peripheral portion are the same, and the joint opposing region that is radially opposed to the joint portion in the intermediate region is the inner peripheral portion. The piston ring according to any one of claims 2 to 5, wherein a thickness of the high thermal expansion material of the portion is formed to be thinner than a thickness of the low thermal expansion material of the outer peripheral portion.

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