Piston and piston ring combination structure

Abstract

To provide a technology of a combination structure of a piston and a piston ring of an internal combustion engine, the technology being capable of suppressing troubles due to direct contact between the piston ring and an inner wall of a piston ring groove.SOLUTION: A combination structure of a piston and a piston ring includes one or multiple partition rings to be attached together with one or multiple piston rings to a ring groove in an axial direction of the piston. The partition ring has an upper partition surface to face an upper groove wall surface of the ring groove, a lower partition surface to face a lower groove wall surface of the ring groove, an inner peripheral fitting surface to form a contact state between itself and a bottom groove wall surface of the ring groove, an outer peripheral separation surface to keep a predetermined clearance between itself and an inner wall of a cylinder of an internal combustion engine, and a pair of abutment end parts to form abutment. At least a part of the abutment of at least one of the one or multiple partition rings is closed against gas or oil to be flowed in the axial direction of the piston.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a combined structure of a piston and a piston ring. [Background technology]

[0002] The internal combustion engine mounted on a typical automobile employs a configuration in which a combination of piston rings including a compression ring (pressure ring) and an oil ring is fitted in a ring groove formed in the piston. In the axial direction of the piston, the compression ring is provided on the combustion chamber side, and the oil ring is provided on the crank chamber side, and they perform their functions by sliding on the inner wall surface of the cylinder. The oil ring, which is the furthest from the combustion chamber, has an oil seal function that suppresses the outflow of oil to the combustion chamber side (oil rising) by scraping off excess engine oil (lubricating oil) attached to the inner wall surface of the cylinder to the crank side, and a function that prevents the piston from seizing due to the operation of the internal combustion engine by adjusting the amount of oil so that a lubricating oil film is appropriately maintained on the inner wall surface of the cylinder. The compression ring has a gas seal function that suppresses the outflow of combustion gas from the combustion chamber side to the crank chamber side (blow-by) by maintaining airtightness, and an oil seal function that suppresses oil rising by scraping off excess oil that the oil ring could not scrape off.

[0003] As described above, a piston ring structure for assembling a combination of multiple piston rings to a piston usually employs a structure in which multiple ring grooves, the same number as the number of piston rings, are formed on the outer circumferential surface of the piston, and one piston ring is fitted into each ring groove. Meanwhile, in recent years, with the trend toward reducing the weight of internal combustion engines, efforts have been made to reduce the weight of pistons by shortening the axial length of the piston (hereinafter, axial length). In addition, efforts have been made to reduce the width (i.e., thickness in the axial direction) of piston rings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 1-21852 [Patent Document 2] Japanese Utility Model Application Publication No. 63-9442 [Patent Document 3] Jpn. Jpn. Published No. 55-2290 [Patent Document 4] Japanese Utility Model Application Publication No. 3-63745 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional internal combustion engines in which piston rings are assembled to pistons, the piston rings come into direct contact with the inner wall of the ring groove of the piston. As a result, with the recent improvement in thermal efficiency and higher output of engines, there have been problems such as adhesion between the piston rings and the inner wall of the ring groove and wear of the inner wall of the ring groove due to sliding between the piston rings and the inner wall of the ring groove. Therefore, there is a demand for a solution to such problems.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a technique capable of suppressing defects caused by direct contact between a piston ring and an inner wall of a ring groove of a piston in a combined structure of a piston and a piston ring of an internal combustion engine. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following configuration: That is, the present invention is a combination structure of a piston and a piston ring for an internal combustion engine, comprising a ring groove for mounting a piston ring provided on an outer peripheral surface of the piston, and one or more piston rings mounted in the ring groove. and a partition ring attached to the ring groove together with the one or more piston rings in the axial direction of the piston, wherein the partition ring has an upper partition wall surface facing an upper groove wall surface, which is a groove wall surface on the combustion chamber side of the internal combustion engine, of a pair of inner walls arranged opposite to each other in the ring groove, a lower partition wall surface facing a lower groove wall surface, which is a groove wall surface on the crank chamber side of the internal combustion engine, of the pair of inner walls arranged opposite to each other in the ring groove, an inner peripheral fitting surface provided on an inner peripheral portion of the partition ring and fitting with a bottom groove wall surface connecting an inner peripheral edge of the upper groove wall surface and an inner peripheral edge of the lower groove wall surface of the ring groove to form a contact state with the bottom groove wall surface, and an outer peripheral separating surface provided on an outer peripheral portion of the partition ring to ensure a predetermined separation distance between the partition ring and an inner wall of a cylinder of the internal combustion engine.

[0008] In the present invention, when a partition ring is attached between the upper groove wall or the lower groove wall of the ring groove and the piston ring, the partition ring functions as a piston land that separates the piston ring from the inner wall of the ring groove. Therefore, compared to a case where a partition ring is not attached between the upper groove wall or the lower groove wall of the ring groove and the piston ring, it is possible to reduce the number of contact points between the piston ring and the inner wall of the ring groove of the piston. Also, in the present invention, when a partition ring is attached between the piston rings, the partition ring functions as a piston land that separates the piston rings. Therefore, compared to a case where the piston rings are separated by a piston land, it is possible to reduce the number of contact points between the piston ring and the inner wall of the ring groove of the piston. As a result, according to the present invention, it is possible to suppress defects caused by direct contact between the piston ring and the inner wall of the ring groove of the piston.

[0009] Furthermore, when a partition ring is fitted between the piston rings, the partition ring functions as a substitute for a piston land that separates the piston rings, and thus it becomes possible to fit a plurality of piston rings in one ring groove. Therefore, according to the present invention, in an internal combustion engine in which a plurality of piston rings are assembled to a piston, the number of ring grooves can be reduced compared to the case where a ring groove is formed for each piston ring. This makes it easier to shorten the axial length of the piston. In addition, since the partition ring is a member separate from the piston, the constraints in terms of strength with respect to making the axial width thin are smaller compared to the piston land. Therefore, instead of the piston land, a partition ring having a thinner width than the piston land can be used. This also makes it easier to shorten the axial length of the piston. As a result, this can contribute to reducing the weight of the piston, and therefore the weight of the internal combustion engine. In addition, by reducing the number of ring grooves to be formed on the outer circumferential surface of the piston, the strength of the piston can be increased compared to the case where a ring groove is formed for each piston ring. This can contribute to increasing the output of the internal combustion engine. In addition, by adjusting the width of the partition ring to be fitted in the ring groove, a thin piston ring can be fitted without thinning the ring groove, improving design freedom.

[0010] In the present invention, a plurality of piston rings may be fitted in the ring groove, and the plurality of piston rings may include a top ring fitted between the upper groove wall surface of the ring groove and the upper partition surface of the partition ring, and a second ring fitted between the lower groove wall surface of the ring groove and the lower partition surface of the partition ring.

[0011] In the present invention, a plurality of piston rings are mounted in the ring groove, and the plurality of piston rings include a second ring mounted between the upper groove wall surface of the ring groove and the upper partition wall surface of the partition ring, and a second ring mounted between the lower groove wall surface of the ring groove and the upper partition wall surface of the partition ring. and an oil ring mounted between the partition ring and the lower partition wall surface.

[0012] Further, a combination structure of a piston and a piston ring according to the present invention includes a first partition ring as the partition ring, and a second partition ring attached to a position in the ring groove closer to the crank chamber than the first partition ring, wherein the first partition ring has a first upper partition wall surface as the upper partition wall surface, a first lower partition wall surface as the lower partition wall surface, a first inner peripheral fitting surface as the inner peripheral fitting surface, and a first outer peripheral spacing surface as the outer peripheral spacing surface, and the second partition ring has a second upper partition wall surface facing the first lower partition wall surface side of the first partition ring, a second lower partition wall surface facing the lower groove wall surface side of the ring groove, and an inner peripheral surface of the second partition ring, a second inner peripheral fitting surface that fits with the bottom groove wall surface to form a contact state with the bottom groove wall surface, and a second outer peripheral spacing surface that is provided on the outer peripheral surface of the second partition ring and ensures a predetermined spacing distance between the inner wall of the cylinder, and a plurality of piston rings are fitted in the ring groove, and the plurality of piston rings may include a top ring that is fitted between the upper groove wall surface of the ring groove and the first upper partition surface of the first partition ring, a second ring that is fitted between the first lower partition surface of the first partition ring and the second upper partition surface of the second partition ring, and an oil ring that is fitted between the lower groove wall surface of the ring groove and the second lower partition surface of the second partition ring.

[0013] In the present invention, the partition ring may have an upper protruding portion that is provided inside the upper partition wall surface in the radial direction of the piston and that protrudes toward the combustion chamber to be supported in the axial direction of the piston, thereby making it possible to restrict movement of the partition ring toward the combustion chamber.

[0014] In the present invention, the partition ring may have a lower protruding portion that is provided inside the lower partition wall surface in the radial direction of the piston and that protrudes toward the crank chamber to be supported in the axial direction of the piston, thereby making it possible to restrict movement of the partition ring toward the crank chamber.

[0015] In the present invention, the partition ring may have a pair of abutment ends that face each other to form abutment. In this way, like a piston ring, the partition ring can be attached to and detached from the ring groove by expanding the abutment. Also, the volume expansion of the partition ring due to thermal expansion can be absorbed by the extension in the circumferential direction.

[0016] The present invention may further include one or more of the partition rings, and at least a part of the joint of at least one of the one or more partition rings may be blocked from gas or oil flowing along the axial direction of the piston. This can suppress gas blow-by and oil rising, thereby reducing blow-by gas and oil consumption.

[0017] The piston and piston ring combination structure according to the present invention may include a plurality of the partition rings overlapping in the axial direction of the piston, and at least two adjacent partition rings among the plurality of partition rings may be fitted in the ring groove such that their joints do not overlap in the axial direction. In this way, the two adjacent partition rings cover each other's joints. This blocks the joints from gas or oil. As a result, gas blow-by and oil rising can be suppressed, and blow-by gas and oil consumption can be reduced.

[0018] Also, in the present invention, the pair of joint ends of the partition ring may be formed such that at least a part of a first joint end, which is one of the pair of joint ends, and at least a part of a second joint end, which is the other of the pair of joint ends, overlap in the axial direction of the piston. In this way, the first joint end and the second joint end prevent gas and oil from passing through the joint along the axial direction of the piston. As a result, at least a part of the joint is blocked from gas or oil flowing along the axial direction of the piston. As a result, gas blow-by and oil rising can be suppressed, and blow-by gas and oil consumption can be reduced.

[0019] In the present invention, the partition ring may further include a blocking portion that blocks the gap by filling the gap. This blocks the gap from gas or oil. As a result, gas blow-by and oil rising can be suppressed, and blow-by gas and oil consumption can be reduced.

[0020] The present invention can also be specified as a partition ring. That is, the present invention may be a partition ring that is mounted in a ring groove for mounting a piston ring provided on the outer circumferential surface of a piston of an internal combustion engine in the axial direction together with one or more piston rings, and includes: an upper partition wall surface that faces the upper groove wall surface side, which is the groove wall surface on the combustion chamber side of the internal combustion engine, of a pair of inner walls arranged opposite to each other in the ring groove in a usage state in which the partition ring is mounted in the ring groove; a lower partition wall surface that faces the lower groove wall surface side, which is the groove wall surface on the crank chamber side of the internal combustion engine, of a pair of inner walls arranged opposite to each other in the ring groove in the usage state; an inner peripheral fitting surface that is provided on the inner peripheral part of the partition ring and that forms a contact state with the bottom groove wall surface by fitting with a bottom groove wall surface that connects the inner peripheral edge of the upper groove wall surface and the inner peripheral edge of the lower groove wall surface of the ring groove in the usage state; and an outer peripheral separating surface that is provided on the outer circumferential part of the partition ring and that ensures a predetermined separation distance between the inner wall of the cylinder of the internal combustion engine in the usage state. Effect of the Invention

[0021] According to the present invention, in a combined structure of a piston and a piston ring of an internal combustion engine, it is possible to suppress defects caused by direct contact between the piston ring and the inner wall of the ring groove of the piston. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a first embodiment. [Diagram 2] 1 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a first embodiment. [Diagram 3] FIG. 2 is a top view of a partition ring according to an embodiment. [Figure 4] 1 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a first modified example of the first embodiment. FIG. [Diagram 5] 1 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a second modified example of the first embodiment. FIG. [Figure 6] 10 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a third modified example of the first embodiment. FIG. [Figure 7] FIG. 6 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a second embodiment. [Figure 8] 10 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a first modified example of the second embodiment. FIG. [Figure 9] FIG. 11 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a second modified example of the second embodiment. [Figure 10] FIG. 11 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a third embodiment. [Figure 11] FIG. 11 is a partial cross-sectional view of an internal combustion engine equipped with a piston ring structure according to a fourth embodiment. [Figure 12] FIG. 13 is a diagram showing the positional relationship of the joints of two partition rings in the fourth embodiment. [Figure 13] FIG. 13 is a diagram for explaining the shape of the joint end portion of the partition ring according to the fifth embodiment. [Figure 14] FIG. 23 is a diagram for explaining the shape of abutment ends of a partition ring according to Modification 1 of Embodiment 5. [Figure 15] FIG. 23 is a diagram for explaining the shape of abutment ends of a partition ring according to Modification 2 of Embodiment 5. [Figure 16] FIG. 23 is a diagram for explaining the shape of abutment ends of a partition ring according to Modification 3 of Embodiment 5. [Figure 17] FIG. 13 is a diagram showing a partition ring according to Modification 3 of Embodiment 5 in a used state, as viewed along the axial direction. [Figure 18] FIG. 23 is a diagram for explaining the shape of abutment ends of a partition ring according to Modification 4 of Embodiment 5. [Figure 19] FIG. 13 is a diagram showing a partition ring according to Modification 4 of Embodiment 5 in a used state, as viewed along the axial direction. [Figure 20] FIG. 13 is a diagram for explaining a joint portion of a partition ring according to a sixth embodiment. [Figure 21] FIG. 1 is a cross-sectional view showing a variation of the partition ring. [Figure 22] FIG. 2 is a cross-sectional view showing a variation of the partition ring. [Diagram 23] FIG. 3 is a cross-sectional view showing a variation of the partition ring. [Figure 24] A cross-sectional view (4) showing a variation of the partition ring. [Diagram 25] A cross-sectional view (5) showing a variation of the partition ring. [Figure 26] A cross-sectional view (6) showing a variation of the partition ring. [Figure 27] A cross-sectional view (7) showing a variation of the partition ring. [Figure 28] A cross-sectional view (8) showing a variation of the partition ring. [Figure 29]A cross-sectional view (9) showing a variation of the partition ring. [Diagram 30] A cross-sectional view (10) showing a variation of the partition ring. [Diagram 31] FIG. 11 is a cross-sectional view showing a variation of the partition ring. [Diagram 32] A cross-sectional view (12) showing a variation of the partition ring. [Diagram 33] A cross-sectional view (13) showing a variation of the partition ring. [Diagram 34] A cross-sectional view (14) showing a variation of the partition ring. [Diagram 35] A cross-sectional view (15) showing a variation of the partition ring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the configurations described in the following embodiments are not intended to limit the technical scope of the invention unless otherwise specified.

[0024] <Embodiment 1> FIG. 1 is a cross-sectional view of an internal combustion engine 100 equipped with a piston and piston ring combination structure (hereinafter, piston ring structure) 110 according to the first embodiment. FIG. 2 is a partial cross-sectional view of the internal combustion engine 100 equipped with the piston ring structure 110 according to the first embodiment. FIG. 2 illustrates a cross section perpendicular to the circumferential direction of the piston ring. As shown in FIG. 1, the internal combustion engine 100 according to the embodiment has a cylinder 10 and a piston 20 attached to the cylinder 10. In the internal combustion engine 100, the combustion chamber side indicated by reference numeral 30 is the upper side, and the crank chamber side indicated by reference numeral 40 is the lower side. As shown in FIG. 2, the internal combustion engine 100 has two compression rings (pressure rings) including a top ring 1 and a second ring 2, and one oil ring. The piston 20 is fitted with a combination of three piston rings, including the piston ring 3.

[0025] [Overall configuration] As shown in FIG. 2, in the internal combustion engine 100, a piston gap PC1 is formed by ensuring a predetermined separation distance d between the outer peripheral surface 20a of the piston 20 and the inner wall surface 10a of the cylinder 10. In addition, a first ring groove 201 and a second ring groove 202 are formed in the outer peripheral surface 20a of the piston 20 in this order from the upper side (combustion chamber 30 side) with a predetermined interval in the axial direction of the piston 20. The piston ring structure 110 is a structure for assembling a piston ring to the piston 20 of the internal combustion engine 100. The piston ring structure 110 includes a first ring groove 201 and a second ring groove 202 for mounting the piston rings, which are provided in the outer peripheral surface 20a of the piston 20, a top ring 1, a second ring 2, an oil ring 3, and a partition ring 4. In this specification, when the top ring 1, the second ring 2, and the oil ring 3 are described without distinction, they are simply referred to as "piston rings". A piston ring is a sliding member that is assembled to a piston mounted in a cylinder of an internal combustion engine and slides on the inner wall surface of the cylinder with the reciprocating motion of the piston. As shown in FIG. 2, the state in which each piston ring and partition ring 4 are assembled to a piston 20 mounted in a cylinder 10 is referred to as a "use state". As shown in FIG. 2, the direction (axial direction) along the central axis of the piston 20, the piston ring, and the partition ring 4 is defined as the "upper and lower direction". In the axial direction of the piston ring and the partition ring 4, the combustion chamber 30 side in the internal combustion engine 100 (upper side in FIG. 2) is defined as the "upper side", and the opposite side, i.e., the crank chamber side (lower side in FIG. 2) is defined as the "lower side". As shown in FIG. 2, in the piston ring structure 110, the top ring 1, the second ring 2, and the partition ring 4 are mounted in the first ring groove 201, and the oil ring 3 is mounted in the second ring groove 202. Hereinafter, each configuration of the piston ring structure 110 will be described.

[0026] [Ring groove] The first ring groove 201 and the second ring groove 202 are formed on the entire circumference of the outer circumferential surface 20a as grooves with a rectangular cross section extending annularly around the axis of the piston 20. As shown in FIG. 2, the second ring groove 202 is formed at a position lower than the first ring groove 201 on the outer circumferential surface 20a of the piston 20. The first ring groove 201 and the second ring groove 202 are each formed to include a pair of groove walls (inner walls) arranged opposite each other vertically. Of the pair of groove walls, the upper groove wall is referred to as the upper groove wall W1, and the lower groove wall is referred to as the lower groove wall W2. In addition, in each of the first ring groove 201 and the second ring groove 202, the groove wall connecting the inner peripheral edge of the upper groove wall W1 and the inner peripheral edge of the lower groove wall W2 is referred to as the bottom groove wall W3. In this example, the first ring groove 201 corresponds to the "ring groove" according to the present invention. The connection portion (corner) between the upper groove wall W1 and the bottom groove wall W3 and the connection portion (corner) between the lower groove wall W2 and the bottom groove wall W3 may be rounded or C-shaped.

[0027] [Top ring] The top ring 1 is a compression ring that is assembled to the uppermost position of the piston 20 in the axial direction among the three piston rings. The top ring 1 in this example is formed in a so-called rectangular shape, and has a rectangular cross section. The top ring 1 has an outer peripheral surface 11, an inner peripheral surface 12, an upper surface 13, and a lower surface 14. The upper surface 13 and the lower surface 14 define the width of the top ring 1 in the axial direction. The outer peripheral surface 11 is formed into a barrel face that is curved so as to protrude radially outward. The top ring 1 is assembled to the piston 20 in the internal combustion engine 100 so that the upper surface 13, which is one of both end surfaces in the axial direction, faces upward and the lower surface 14, which is the other, faces downward, and the outer peripheral surface 11 is in sliding contact with the inner wall surface 10a of the cylinder 10. The top ring 1 has a self-tension such that the outer peripheral surface 11 presses against the inner wall surface 10a of the cylinder 10 in a used state. This provides a gas seal function and an oil seal function. In addition, the top ring according to the present invention The shape of the top ring is not limited to the above. Various shapes can be used for the top ring. For example, the outer peripheral surface of the top ring may be straight-faced or tapered. In addition, the cross-sectional shape of the top ring may be keystone, half keystone, or internal bevel.

[0028] [Second Ring] The second ring 2 is a compression ring that is assembled to the lower side of the top ring 1 in the axial direction of the piston 20. That is, the second ring 2 is assembled between the top ring 1 and the oil ring 3. The second ring 2 has an outer peripheral surface 21, an inner peripheral surface 22, an upper surface 23, and a lower surface 24. The upper surface 23 and the lower surface 24 define the width of the second ring 2 in the axial direction. The second ring 2 is formed in a so-called rectangular shape, and the outer peripheral surface 21 of the second ring 2 has a tapered shape that is inclined so that the diameter increases toward the lower side. In the internal combustion engine 100, the second ring 2 is assembled to the piston 20 so that the upper surface 23, which is one of both end surfaces in the axial direction, faces upward and the lower surface 24, which is the other, faces downward, and the outer peripheral surface 21 is in sliding contact with the inner wall surface 10a of the cylinder 10. The second ring 2 has a self-tension so that the outer peripheral surface 21 presses against the inner wall surface 10a of the cylinder 10 in a used state. This provides a gas seal function and an oil seal function. The shape of the second ring according to the present invention is not limited to the above. Various shapes can be adopted for the second ring. For example, the outer peripheral surface of the second ring may be a barrel face or a straight face. The second ring may be a scraper ring having an undercut or a napier ring. The cross-sectional shape of the second ring may be a keystone, half keystone, or internal bevel.

[0029] [Oil ring] Of the three piston rings, the oil ring 3 is the piston ring that is assembled to the lowest position in the axial direction of the piston 20. The oil ring 3 is a so-called three-piece type combined oil ring, and includes a pair of segments 31, 31 (an example of a pair of sliding parts) and a spacer expander 32 (an example of an expander), as shown in Fig. 2.

[0030] The pair of segments 31, 31 are formed in an annular shape around the axis of the oil ring 3, and are arranged side by side in the axial direction independently of each other. In the oil ring 3 according to this embodiment, the pair of segments 31, 31 have the same shape. However, in the present invention, the pair of segments may have different shapes. Hereinafter, when the pair of segments 31, 31 are to be distinguished from each other, the segment 31 provided on the upper side (combustion chamber 30 side) is referred to as the upper segment 31U, and the segment 31 provided on the lower side (crank chamber 40 side) is referred to as the lower segment 31L. When there is no need to distinguish between them, they are simply referred to as the segment 31. As shown in FIG. 2, the segment 31 has an outer peripheral surface 311, an inner peripheral surface 312, an upper surface 313, and a lower surface 314. The upper surface 313 and the lower surface 314 define the width of the segment 31 in the axial direction. In the internal combustion engine 100, the segment 31 is assembled to the piston 20 such that an upper surface 313, which is one of both end surfaces in the axial direction, faces upward and a lower surface 314, which is the other, faces downward, and the outer circumferential surface 311 is in sliding contact with the inner wall surface 10a of the cylinder 10. The spacer expander 32 is provided between the pair of segments 31, 31, and has a self-tensioning force so as to expand in diameter when in use. As a result, the upper segment 31U and the lower segment 31L are urged radially outward by the spacer expander 32, and the outer circumferential surface 311 presses the inner wall surface 10a of the cylinder 10. This provides an oil seal function. The shape of the oil ring according to the present invention is not limited to the above. The oil ring may be, for example, a so-called two-piece oil ring. The two-piece oil ring has an oil ring main body formed in an annular shape around the axis and a coil expander (an example of an expander) that urges the oil ring main body radially outward, and the oil ring main body has a coil expander protruding radially outward. The term "oil ring" refers to an oil ring in which a pair of rails (an example of a pair of sliding parts) that are aligned in the axial direction of the oil ring are formed. The oil ring may also be in a form that does not include a spacer expander or a coil expander and functions as a single unit.

[0031] [Partitioning] The partition ring 4 is a ring-shaped member that functions as a substitute for a piston land by being fitted in a ring groove (in this example, the first ring groove 201) together with one or more piston rings (in this example, the top ring 1 and the second ring 2). The partition ring 4 in this example is formed in a so-called rectangular shape, and a cross section perpendicular to the circumferential direction is rectangular. However, the present invention is not limited to this. The partition ring 4 has an outer peripheral separation surface 41, an inner peripheral fitting surface 42, an upper partition wall surface 43, and a lower partition wall surface 44. The upper partition wall surface of the partition ring may be parallel to the upper groove wall of the ring groove, or may be inclined relative to the upper groove wall. Similarly, the lower partition wall surface of the partition ring may be parallel to the lower groove wall of the ring groove, or may be inclined relative to the lower groove wall. In addition, each corner of the partition ring may be chamfered, step cut, or the like.

[0032] As shown in FIG. 2, the upper partition surface 43 faces the upper groove wall W1 of the first ring groove 201 in the use state. As a result, a space in which the top ring 1 can be attached is defined between the upper groove wall W1 and the upper partition surface 43. The lower partition surface 44 faces the lower groove wall W2 of the first ring groove 201 in the use state. As a result, a space in which the second ring 2 can be attached is defined between the lower groove wall W2 and the lower partition surface 44. The inner fitting surface 42 is provided on the inner periphery of the partition ring 4. The inner fitting surface 42 fits with the bottom groove wall W3 in the use state to form a contact state with the bottom groove wall W3. The inner fitting surface 42 in this example is in contact with the bottom groove wall W3 over the entire circumference. However, the present invention is not limited to this, and it is sufficient that at least a part of the inner fitting surface is in contact with the bottom groove wall. In addition, the inner circumferential fitting surface 42 of this example is fitted with the bottom groove wall W3 so that the partition ring 4 can slide on the bottom groove wall W3 along the axial direction. Therefore, the partition ring 4 is movable along the axial direction together with the top ring 1 and the second ring 2. However, the present invention is not limited to this. The inner circumferential fitting surface may be fitted with the bottom groove wall to such an extent that the partition ring cannot move along the axial direction. The outer circumferential separation surface 41 is provided on the outer periphery of the partition ring 4 and connects the outer circumferential edge of the upper partition wall surface 43 and the outer circumferential edge of the lower partition wall surface 44. In addition, the outer circumferential separation surface 41 secures a predetermined separation distance d1 between the inner wall surface 10a of the cylinder 10 in the usage state. In other words, the partition ring 4 is separated from the inner wall surface 10a of the cylinder 10. Here, FIG. 3 is a top view of the partition ring 4 according to the first embodiment (viewed from above in the axial direction). As shown in FIG. 3, the partition ring 4 includes a pair of joint ends 410, 420 that face each other to form a joint G1.

[0033] The material of the partition ring 4 is not particularly limited, but for example, steel, cast iron, Cu alloy, or aluminum alloy can be used. In addition, the surface of the partition ring 4 can be coated with a resin film, a nitriding film, a Ni-P plating film, a chrome plating film, or the like. Alternatively, a coating may be formed that includes at least one layer selected from the group consisting of a resin coating, a PVD coating, and a DLC coating. The term "resin coating" refers to a coating formed from a resin material. The term "nitriding coating" refers to a coating formed by infiltrating nitrogen into a metal surface through nitriding. The term "Ni-P plating coating" refers to a coating formed by electroless Ni-P plating. The term "chrome plating coating" refers to a coating formed by chrome plating. Chrome plating is also called industrial chrome plating. The term "PVD (physical vapor deposition) coating" refers to a coating formed by the PVD method. The term "DLC (Diamond Like Carbon) treated coating" refers to a coating that is mainly This refers to an amorphous hard carbon film composed of hydrocarbons and carbon allotropes. Such a coating is applied to the inner circumferential fitting surface 42, which is the contact portion between the partition ring 4 and other members, It is preferable to form the coating on the side partition wall surface 43 and the lower partition wall surface 44. By forming such a coating, the wear resistance and the like of the partition ring 4 can be increased, and defects due to direct contact between base materials, such as adhesion between the partition ring 4 and other members, can be prevented.

[0034] As shown in FIG. 2, in the piston ring structure 110, the top ring 1 is fitted between the upper groove wall W1 of the first ring groove 201 and the upper partition wall surface 43 of the partition ring 4, the second ring 2 is fitted between the lower groove wall W2 of the first ring groove 201 and the lower partition wall surface 44 of the partition ring 4, and the oil ring 3 is fitted in the second ring groove 202. In the piston ring structure 110, the lower surface 14 of the top ring 1 faces the upper partition wall surface 43 of the partition ring 4, and the upper surface 23 of the second ring 2 faces the lower partition wall surface 44 of the partition ring 4. Therefore, when the top ring 1 moves downward, the partition ring 4 abuts against the top ring 1, and when the second ring 2 moves upward, the partition ring 4 abuts against the second ring 2. In other words, the partition ring 4 is interposed between the top ring 1 and the second ring 2, and the top ring 1 and the second ring 2 are separated by the partition ring 4. In this way, in the piston ring structure 110, the partition ring 4 functions in place of a piston land separating the top ring 1 and the second ring 2, thereby forming a space surrounded by the lower surface 14 of the top ring 1, the upper surface 23 of the second ring 2, the outer peripheral separating surface 41 of the partition ring 4, and the inner wall surface 10a of the cylinder 10, which can adjust the pressure between the top ring 1 and the second ring 2 and function as an oil reservoir.

[0035] [Actions and Effects] As described above, the piston ring structure 110 according to the first embodiment includes the first ring groove 201 formed in the outer peripheral surface 20a of the piston 20, a plurality of piston rings (the top ring 1 and the second ring 2) mounted in the first ring groove 201, and the partition ring 4 mounted in the first ring groove 201 in line with the top ring 1 and the second ring 2 in the axial direction of the piston 20. The partition ring 4 has an upper partition wall surface 43 facing the upper groove wall W1 side of the first ring groove 201, a lower partition wall surface 44 facing the lower groove wall W2 side of the first ring groove 201, an inner peripheral fitting surface 42 that fits with the bottom groove wall W3 of the first ring groove 201 to form a contact state with the bottom groove wall W3, and an outer peripheral separating surface 41 that ensures a predetermined separation distance d1 between the partition ring 4 and the inner wall surface 10a of the cylinder 10.

[0036] In an internal combustion engine in which multiple piston rings are assembled to a piston, if a ring groove is formed for each piston ring, the interval between the ring grooves must be shortened in order to shorten the axial length of the piston. However, if the interval between the ring grooves is shortened, the piston land between adjacent ring grooves in the axial direction becomes thin, making it difficult to maintain the strength of the piston. In addition, from the viewpoint of the machining accuracy of the ring grooves, it is also difficult to shorten the axial length of the piston.

[0037] According to the piston ring structure 110, the partition ring 4 functions as a substitute for a piston land that separates the top ring 1 and the second ring 2, so that the top ring 1 and the second ring 2 can be fitted in the first ring groove 201. Therefore, it is not necessary to form a ring groove for fitting the top ring 1 and a ring groove for fitting the second ring 2 separately on the outer circumferential surface 20a of the piston 20. In other words, according to the piston ring structure 110, a plurality of piston rings (the top ring 1 and the second ring 2 in this example) can be fitted in one ring groove. As a result, in an internal combustion engine in which a plurality of piston rings are assembled to a piston, the number of ring grooves can be reduced compared to a case in which a ring groove is formed for each piston ring. This makes it easy to shorten the axial length of the piston 20. As a result, according to the piston ring structure 110, it is possible to contribute to reducing the weight of the piston, and therefore the weight of the internal combustion engine. In addition, the piston ring structure 110 can be formed in a single ring groove. By reducing the width of the piston ring and the partition ring, the axial length of the piston 20 can be shortened. Also, by reducing the number of ring grooves to be formed on the outer peripheral surface 20a of the piston 20, the strength of the piston can be increased compared to the case where a ring groove is formed for each piston ring. This contributes to increasing the output of the internal combustion engine.

[0038] Furthermore, according to the piston ring structure 110, the design constraints on the land volume can be relaxed. Here, the "land volume" refers to the volume of the space surrounded by the piston rings adjacent in the axial direction, the outer peripheral surface of the piston, and the inner wall surface of the cylinder. In this example, since the partition ring 4 functions as a substitute for the piston land, the volume of the space surrounded by the lower surface 14 of the top ring 1, the upper surface 23 of the second ring 2, and the outer peripheral surface 20a of the piston 20 corresponds to the land volume. Since the partition ring 4 is formed as a member separate from the piston 20, the constraints in terms of strength with respect to making the width in the axial direction thin are smaller than those of the piston land. Therefore, according to the piston ring structure 110, the degree of freedom in designing the land volume can be increased. This can improve the degree of freedom in designing the pressure adjustment function and the function as an oil reservoir.

[0039] In addition, since pistons are usually made of aluminum alloy, aluminum adhesion may occur at the contact points between the piston ring and the inner wall of the ring groove. In addition, the inner wall of the ring groove may be worn due to sliding between the piston ring and the inner wall of the ring groove. In this regard, in the piston ring structure 110, the partition ring 4 is interposed between the top ring 1 and the second ring 2 instead of the piston land, so that the contact points between the top ring 1 and the inner wall of the ring groove and the contact points between the second ring 2 and the inner wall of the ring groove can be reduced compared to the case where the piston rings are separated from each other by the piston land. Therefore, defects due to direct contact between the piston ring and the inner wall of the ring groove of the piston, such as aluminum adhesion, can be suppressed. In addition, by appropriately selecting the material and surface treatment of the partition ring 4, it is possible to prevent the occurrence of defects such as aluminum adhesion at the contact points between the top ring 1 or the second ring 2 and the partition ring 4, and to improve the wear resistance of the partition ring 4.

[0040] In addition, in the piston ring structure 110, a contact state is formed between the bottom groove wall W3 of the first ring groove 201 and the inner fitting surface 42 of the partition ring 4, so that the amount of oil and gas passing between the bottom groove wall W3 of the first ring groove 201 and the inner fitting surface 42 of the partition ring 4 can be reduced. In other words, oil rising and gas outflow from the inner periphery side of the partition ring 4 can be suppressed. In addition, since the bottom groove wall W3 of the first ring groove 201 and the inner fitting surface 42 of the partition ring 4 are in contact with each other, the heat of the piston 20 can be transferred from the bottom groove wall W3 to the piston ring via the inner fitting surface 42 of the partition ring 4, and the heat can be released to the cylinder 10 with which the piston ring slides. Note that, in the present invention, it is sufficient that at least a part of the inner fitting surface is in contact with the bottom groove wall.

[0041] Furthermore, the partition ring 4 has a pair of abutment ends 410, 420 that face each other to form abutment G1. The formation of the abutment G1 in the partition ring 4 makes it possible to attach and detach the partition ring 4 to the ring groove, and also makes it possible to replace the partition ring 4. The abutment G1 allows the partition ring 4 to absorb the volumetric expansion caused by thermal expansion by stretching in the circumferential direction. This makes it possible to suppress the volumetric expansion of the partition ring 4 due to thermal expansion proceeding radially inward, causing the inner peripheral fitting surface 42 of the partition ring 4 to bite into the bottom groove wall W3 of the first ring groove 201, or the volumetric expansion of the partition ring 4 proceeding radially outward, causing a change in the land volume. In addition, it is possible to suppress the application of excessive force to the partition ring 4 due to thermal expansion of the piston 20, and the partition ring 4 from biting into the piston. In addition, the formation of an appropriate abutment gap makes it possible to suppress the partition ring 4 from being broken into the piston. This prevents the abutment ends 410, 420 from hitting each other when the partition ring 4 thermally expands, and as a result, prevents a gap from being generated on the inner peripheral side of the partition ring 4.

[0042] The number of piston rings according to the present invention is not limited to three, and the types of piston rings are not limited to the above-mentioned top ring, second ring, and oil ring. For example, the multiple piston rings may be configured to include one compression ring and one oil ring, and the compression ring, the oil ring, and a partition ring may be mounted in one ring groove. In addition, the number of compression rings assembled to the piston may be three or more, and for example, the compression ring may be disposed at a position closer to the crank chamber side than the oil ring. In that case, the oil ring, the compression ring, and the partition ring may be mounted in one ring groove, and the partition ring may be interposed between the oil ring and the compression ring. In addition, the number of oil rings may be two or more, and a partition ring may be interposed between the oil rings.

[0043] [Modification of the first embodiment] The following describes modifications of the embodiment 1. In the following description, differences from the above-described piston ring structure 110 will be mainly described, and similar configurations will be denoted by the same reference numerals and detailed description will be omitted.

[0044] [Variation 1] 4 is a partial cross-sectional view of an internal combustion engine 100A equipped with a piston ring structure 110A according to Modification 1 of Embodiment 1. The piston ring structure 110A according to Modification 1 differs from the piston ring structure 110 in that the partition ring 4 is mounted in a second ring groove 202 in line with the second ring 2 and the oil ring 3 in the axial direction of the piston 20. In this example, the second ring groove 202 corresponds to the "ring groove" according to the present invention.

[0045] As shown in Fig. 4, in the piston ring structure 110A, the upper partition wall surface 43 of the partition ring 4 faces the upper groove wall W1 of the second ring groove 202, so that a space in which the second ring 2 can be fitted is defined between the upper groove wall W1 and the upper partition wall surface 43. In addition, the lower partition wall surface 44 of the partition ring 4 faces the lower groove wall W2, so that a space in which the oil ring 3 can be fitted is defined between the lower groove wall W2 and the lower partition wall surface 44. As shown in Fig. 4, in the piston ring structure 110A, the top ring 1 is fitted in the first ring groove 201, the second ring 2 is fitted between the upper groove wall W1 of the second ring groove 202 and the upper partition wall surface 43 of the partition ring 4, and the oil ring 3 is fitted between the lower groove wall W2 of the second ring groove 202 and the lower partition wall surface 44 of the partition ring 4. In the piston ring structure 110A, the lower surface 24 of the second ring 2 faces the upper partition wall surface 43 of the partition ring 4, and the upper surface 313 of the upper segment 31U faces the lower partition wall surface 44 of the partition ring 4. Therefore, when the second ring 2 moves downward, the partition ring 4 abuts against the second ring 2, and when the oil ring 3 moves upward, the partition ring 4 abuts against the oil ring 3. In other words, the partition ring 4 is interposed between the second ring 2 and the oil ring 3.

[0046] The piston ring structure 110A according to the first modification can also provide the same effects as the above-mentioned piston ring structure 110. That is, according to the piston ring structure 110A, multiple piston rings (in this example, the second ring 2 and the oil ring 3) can be mounted in one ring groove, and the number of ring grooves can be reduced. This makes it easy to shorten the axial length of the piston 20. As a result, the piston ring structure 110A can contribute to reducing the weight of the piston, and ultimately the weight of the internal combustion engine. In addition, the partition ring 4 functions as a substitute for a piston land that separates the piston rings from each other. By using this function, the number of contact points between the piston ring and the inner wall of the piston ring groove can be reduced compared to when the piston rings are separated by a piston land, which makes it possible to suppress problems caused by direct contact between the piston ring and the inner wall of the piston ring groove.

[0047] [Variation 2] FIG. 5 is a partial cross-sectional view of an internal combustion engine 100B equipped with a piston ring structure 110B according to Modification 2 of the embodiment 1. The piston ring structure 110B according to Modification 2 differs from the piston ring structure 110 in that only a first ring groove 201 is formed on the outer peripheral surface 20a of the piston 20, that a top ring 1, a second ring 2, and an oil ring 3 are attached to the first ring groove 201, and that a partition ring indicated by reference numeral 5 is attached to the first ring groove 201 in addition to the partition ring 4. In Modification 2, the first ring groove 201 corresponds to the "ring groove" according to the present invention. In addition, in Modification 2, the partition ring 4, the outer peripheral separating surface 41, the inner peripheral fitting surface 42, the upper partition wall surface 43, and the lower partition wall surface 44 correspond to the "first partition ring", the "first outer peripheral separating surface", the "first inner peripheral fitting surface", the "first upper partition wall surface", and the "first lower partition wall surface" according to the present invention, respectively. The partition ring 5 has an outer peripheral separating surface 51, an inner peripheral fitting surface 52, an upper partition wall surface 53, and a lower partition wall surface 54. In the second modification, the partition ring 5, the outer peripheral separating surface 51, the inner peripheral fitting surface 52, the upper partition wall surface 53, and the lower partition wall surface 54 correspond to the "second partition ring", the "second outer peripheral separating surface", the "second inner peripheral fitting surface", the "second upper partition wall surface", and the "second lower partition wall surface" according to the present invention, respectively. The partition ring 5 also corresponds to the "partition ring" according to the present invention.

[0048] 5, in the piston ring structure 110B, the partition ring 4 and the partition ring 5 are mounted in the first ring groove 201 together with the top ring 1, the second ring 2, and the oil ring 3 in the axial direction of the piston 20. An upper partition wall surface 43 of the partition ring 4 faces the upper groove wall W1 of the first ring groove 201, thereby defining a space between the upper groove wall W1 and the upper partition wall surface 43 in which the top ring 1 can be mounted. In addition, a lower partition wall surface 44 of the partition ring 4 faces the lower groove wall W2, thereby defining a space between the lower groove wall W2 and the lower partition wall surface 44 in which the second ring 2 and the oil ring 3 can be mounted.

[0049] In the piston ring structure 110B, the partition ring 5 is attached to a position lower than the partition ring 4 in the first ring groove 201. In the piston ring structure 110B, an upper partition wall surface 53 of the partition ring 5 faces the lower partition wall surface 44 of the partition ring 4, so that a space in which the second ring 2 can be attached is defined between the lower partition wall surface 44 of the partition ring 4 and the upper partition wall surface 53 of the partition ring 5. In addition, a lower partition wall surface 54 of the partition ring 5 faces the lower groove wall W2, so that a space in which the oil ring 3 can be attached is defined between the lower groove wall W2 and the lower partition wall surface 54.

[0050] In addition, the inner circumferential fitting surface 52 provided on the inner circumferential portion of the partition ring 5 is fitted with the bottom groove wall W3 in a usage state, thereby forming a contact state with the bottom groove wall W3. The inner circumferential fitting surface 52 of this example is in contact with the bottom groove wall W3 over the entire circumference. However, the present invention is not limited to this, and it is sufficient that at least a part of the second inner circumferential fitting surface is in contact with the bottom groove wall. In addition, the inner circumferential fitting surface 42 of this example is fitted with the bottom groove wall W3 so that the partition ring 4 can slide on the bottom groove wall W3 along the axial direction. Therefore, the partition ring 4 can move along the axial direction together with the top ring 1 and the second ring 2. However, the present invention is not limited to this. In addition, the outer circumferential separation surface 51 provided on the outer circumferential portion of the partition ring 5 ensures a predetermined separation distance d2 between the inner wall surface 10a of the cylinder 10 in a usage state. do.

[0051] 5, in the piston ring structure 110B, the top ring 1 is fitted between the upper groove wall W1 of the first ring groove 201 and the upper partition wall surface 43 of the partition ring 4, the second ring 2 is fitted between the lower partition wall surface 44 of the partition ring 4 and the upper partition wall surface 53 of the partition ring 5, and the oil ring 3 is fitted between the lower groove wall W2 of the first ring groove 201 and the lower partition wall surface 54 of the partition ring 5. That is, in the piston ring structure 110B, the partition ring 4 is interposed between the top ring 1 and the second ring 2, and the partition ring 5 is interposed between the second ring 2 and the oil ring 3. In this way, in the piston ring structure 110B, the partition ring 4 and the partition ring 5 function as substitutes for piston lands.

[0052] The piston ring structure 110B according to the second modification can also provide the same effect as the piston ring structure 110 described above. That is, according to the piston ring structure 110B, a plurality of piston rings (a top ring 1, a second ring 2, and an oil ring 3 in this example) can be fitted in one ring groove, and the number of ring grooves can be reduced. This makes it easier to shorten the axial length of the piston 20. In particular, in the second modification, three piston rings can be fitted in one ring groove, so that the structure of the piston 20 can be further simplified, and it becomes easier to shorten the axial length of the piston 20. In addition, the partition ring 4 and the partition ring 5 function as a substitute for a piston land that separates the piston rings from each other, and thus defects caused by direct contact between the piston rings and the inner wall of the ring groove of the piston can be suppressed.

[0053] [Variation 3] 6 is a partial cross-sectional view of an internal combustion engine 100C equipped with a piston ring structure 110C according to Modification 3 of Embodiment 1. The piston ring structure 110C according to Modification 3 differs from the piston ring structure 110 in that a retaining portion H1 is formed on a bottom groove wall W3 of the first ring groove 201.

[0054] As shown in FIG. 6, in the piston ring structure 110C, a part of the bottom groove wall W3 of the first ring groove 201 is recessed radially inward to form a holding portion H1 for holding the partition ring 4. The holding portion H1 is formed as an inner wall of a groove formed around the entire circumference of the bottom groove wall W3, and holds the partition ring 4 to restrict the movement of the partition ring 4 along the axial direction. The holding portion H1 is formed including an upper restricting wall W31 and a lower restricting wall W32 arranged opposite to each other vertically, and a fitting wall W33 connecting the inner peripheral edge of the upper restricting wall W31 and the inner peripheral edge of the lower restricting wall W32. The upper restricting wall W31 restricts the upward movement of the partition ring 4 by contacting an upper partition wall surface 43 of the partition ring 4. The lower restricting wall W32 restricts the downward movement of the partition ring 4 by contacting a lower partition wall surface 44 of the partition ring 4. The fitting wall W33 fits with the inner fitting surface 42 of the partition ring 4. Here, in the piston ring structure 110C, the distance d3 between the upper regulating wall W31 and the upper groove wall W1 in the axial direction is set to be larger than the width t1 of the top ring 1 in the axial direction. This allows clearances to be formed between the top ring 1 and the upper groove wall W1 and between the top ring 1 and the upper partition wall surface 43. However, the present invention is not limited to this. For example, d3=t1 may be satisfied. Also, in the piston ring structure 110C, the distance d4 between the lower regulating wall W32 and the lower groove wall W2 in the axial direction is set to be larger than the width t2 of the second ring 2 in the axial direction. This allows clearances to be formed between the second ring 2 and the lower partition wall surface 44 and between the second ring 2 and the lower groove wall W2. However, the present invention is not limited to this. For example, d4=t2 may be satisfied.

[0055] The retaining portion H1 can be combined with other aspects of the present invention. For example, in the piston ring structure 110A, the partition ring 4 may be retained by the retaining portion H1. In the piston ring structure 110B, either the partition ring 4 or the partition ring 5 may be retained by the retaining portion H1, or two retaining portions H1 may be formed, and both the partition ring 4 and the partition ring 5 may be retained by the retaining portion H1, respectively.

[0056] <Embodiment 2> 7 is a partial cross-sectional view of an internal combustion engine 200 equipped with a piston ring structure 120 according to embodiment 2. The piston ring structure 120 according to embodiment 2 will be described below, focusing on the differences from the piston ring structure 110 according to embodiment 1, and similar configurations will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0057] 7, the piston ring structure 120 differs from the piston ring structure 110 in that a partition ring 6 is attached to a first ring groove 201 instead of the partition ring 4. The partition ring 6 differs from the partition ring 4 in that a cross section perpendicular to the circumferential direction is formed into a T-shape. In this example, the first ring groove 201 corresponds to the "ring groove" according to the present invention.

[0058] The partition ring 6 has an outer peripheral spacing surface 61, an inner peripheral fitting surface 62, an upper partition wall surface 63, a lower partition wall surface 64, an upper protruding portion 65, and a lower protruding portion 66. In this example, the partition ring 6 corresponds to the "partition ring" according to the present invention.

[0059] 7, in the piston ring structure 120, the partition ring 6, the top ring 1, and the second ring 2 are mounted in the first ring groove 201 in a line up in the axial direction of the piston 20. An upper partition wall surface 63 of the partition ring 6 faces the upper groove wall W1 of the first ring groove 201, thereby defining a space between the upper groove wall W1 and the upper partition wall surface 63 into which the top ring 1 can be mounted. In addition, a lower partition wall surface 64 of the partition ring 6 faces the lower groove wall W2, thereby defining a space between the lower groove wall W2 and the lower partition wall surface 64 into which the second ring 2 can be mounted.

[0060] In addition, the inner circumferential fitting surface 62 provided on the inner circumferential portion of the partition ring 6 is fitted with the bottom groove wall W3 in the usage state, thereby forming a contact state with the bottom groove wall W3. In this example, the inner circumferential fitting surface 62 is in contact with the bottom groove wall W3 over the entire circumference. However, the present invention is not limited to this, and it is sufficient that at least a portion of the second inner circumferential fitting surface is in contact with the bottom groove wall. In addition, the outer circumferential separating surface 61 provided on the outer circumferential portion of the partition ring 6 ensures a predetermined separation distance d5 between it and the inner wall surface 10a of the cylinder 10 in the usage state.

[0061] As shown in Figure 7, in the piston ring structure 120, the top ring 1 is fitted between the upper groove wall W1 of the first ring groove 201 and the upper partition surface 63 of the partition ring 6, the second ring 2 is fitted between the lower groove wall W2 of the first ring groove 201 and the lower partition surface 64 of the partition ring 6, and the oil ring 3 is fitted in the second ring groove 202.

[0062] The piston ring structure 120 according to the second embodiment can also provide the same effects as the piston ring structure 110 according to the first embodiment. That is, according to the piston ring structure 120, a plurality of piston rings (in this example, the top ring 1 and the second ring 2) can be mounted in one ring groove, and the number of ring grooves can be reduced. This makes it easy to shorten the axial length of the piston 20.

[0063] Further, in the piston ring structure 120, the partition ring 6 has an upper protruding portion 65 and a lower protruding portion 66. As shown in FIG. 7, the upper protruding portion 65 is provided inside the upper partition wall surface 63 in the radial direction of the piston 20, and protrudes toward the combustion chamber 30 with respect to the upper partition wall surface 63. The upper protruding portion 65 is provided inside the top ring 1 in the radial direction of the piston 20, that is, on the inner circumferential surface 12 side of the top ring 1. The upper protruding portion 65 is supported in the axial direction of the piston 20 by abutting against the upper groove wall W1 of the first ring groove 201. This restricts the upward movement of the partition ring 6. Here, in the piston ring structure 120, the protruding amount of the upper protruding portion 65 with respect to the upper partition wall surface 63, that is, the distance h1 between the top of the upper protruding portion 65 and the upper partition wall surface 63 in the axial direction, is set to be larger than the width t1 of the top ring 1 in the axial direction. This allows a clearance to be formed between the top ring 1 and the upper groove wall W1 or between the top ring 1 and the upper partition surface 63. However, the present invention is not limited to this. The upper protrusion 65 only needs to be configured so that a clearance can be formed between the top ring 1 and the upper partition surface 63 by being supported in the axial direction in contact with the inner wall of the first ring groove 201, and h1 may be set smaller than t1 according to the shape of the inner peripheral edge of the ring groove to ensure the clearance. The top of the upper protrusion 65 may be a flat surface parallel to the upper partition surface 63, or may not be a flat surface. The top may be a curved R surface or an inclined surface. The edge may be chamfered. The lower protrusion 66 is provided inside the lower partition surface 64 in the radial direction of the piston 20, and protrudes toward the crank chamber 40 with respect to the lower partition surface 64. The lower protrusion 66 is provided radially inward of the second ring 2, that is, on the inner circumferential surface 22 side of the second ring 2. The lower protrusion 66 is supported in the axial direction of the piston 20 by abutting against the lower groove wall W2 of the first ring groove 201. This restricts the partition ring 6 from moving downward.Here, in the piston ring structure 120, the amount of protrusion of the lower protrusion 66 from the lower partition surface 64, that is, the distance h2 between the top of the lower protrusion 66 and the lower partition surface 64 in the axial direction is set to be larger than the width t2 of the second ring 2 in the axial direction. This allows a clearance to be formed between the second ring 2 and the lower partition surface 64 and between the second ring 2 and the lower groove wall W2. However, the present invention is not limited to this. The lower protrusion 66 only needs to be configured so that a clearance can be formed between the top ring 1 and the lower partition surface 64 by being supported in the axial direction in contact with the inner wall of the first ring groove 201, and h2 may be set to be smaller than t2 according to the shape of the inner peripheral edge of the ring groove to ensure the clearance. In addition, the top of the lower protrusion 66 may be a flat surface parallel to the lower partition surface 64, or may not be a flat surface. The top may be a curved R surface or an inclined surface. In addition, a chamfer may be formed on the edge. Furthermore, the partition ring 6 may be movable in the axial direction, or the movement in the axial direction may be restricted.

[0064] As shown in FIG. 7, the upper protrusion 65 and the lower protrusion 66 are formed to include a part of the inner fitting surface 62. Therefore, the axial length of the inner fitting surface 62 is longer than the axial length of the outer circumferential separation surface 61. As a result, by lengthening the inner fitting surface 62 that contacts the bottom groove wall W3 of the first ring groove 201 in the axial direction, heat of the piston 20 is easily transferred from the bottom groove wall W3 to the partition ring 6, and heat can be easily released from the partition ring 6 to the cylinder 10 via the piston ring. The partition ring 6 may have only one of the upper protrusion 65 and the lower protrusion 66. In other words, the cross section of the partition ring 6 perpendicular to the circumferential direction may be formed in an L-shape.

[0065] [Modification of the second embodiment] The following describes a modification of the embodiment 2. In the following description, differences from the above-described piston ring structure 120 will be mainly described, and similar configurations will be denoted by the same reference numerals and detailed description will be omitted.

[0066] [Variation 1] 8 is a partial cross-sectional view of an internal combustion engine 200A equipped with a piston ring structure 120A according to Modification 1 of Embodiment 2. The piston ring structure 120A according to Modification 1 differs from the piston ring structure 120 in that the partition ring 6 is mounted in a second ring groove 202 in line with the second ring 2 and the oil ring 3 in the axial direction of the piston 20. In this example, the second ring groove 202 corresponds to the "ring groove" according to the present invention.

[0067] As shown in Fig. 8, in the piston ring structure 120A, an upper partition wall surface 63 of the partition ring 6 faces the upper groove wall W1 of the second ring groove 202, so that a space in which the second ring 2 can be fitted is defined between the upper groove wall W1 and the upper partition wall surface 63. In addition, a lower partition wall surface 64 of the partition ring 6 faces the lower groove wall W2, so that a space in which the oil ring 3 can be fitted is defined between the lower groove wall W2 and the lower partition wall surface 64. As shown in Fig. 8, in the piston ring structure 120A, the top ring 1 is fitted in the first ring groove 201, the second ring 2 is fitted between the upper groove wall W1 of the second ring groove 202 and the upper partition wall surface 63 of the partition ring 6, and the oil ring 3 is fitted between the lower groove wall W2 of the second ring groove 202 and the lower partition wall surface 64 of the partition ring 6.

[0068] Furthermore, in the piston ring structure 120A, the upper protrusion 65 is supported in the axial direction of the piston 20 by abutting against the upper groove wall W1 of the second ring groove 202. This restricts the upward movement of the partition ring 6. Here, in the piston ring structure 120A, the protrusion amount h1 of the upper protrusion 65 relative to the upper partition surface 63 is set to be larger than the width t2 of the second ring 2 in the axial direction. This allows a clearance to be formed between the second ring 2 and the upper groove wall W1 or between the second ring 2 and the upper partition surface 63. However, the present invention is not limited to this. In order to ensure the clearance, h1 may be set smaller than t2 according to the shape of the inner peripheral edge of the ring groove. Also, in the piston ring structure 120A, the lower protrusion 66 is supported in the axial direction of the piston 20 by abutting against the lower groove wall W2 of the second ring groove 202. This restricts the downward movement of the partition ring 6. Here, in the piston ring structure 120A, the protrusion amount h2 of the lower protruding portion 66 relative to the lower partition surface 64 is set to be larger than the axial width t3 of the oil ring 3. This makes it possible to form clearances between the oil ring 3 and the lower partition surface 64 and between the oil ring 3 and the lower groove wall W2. However, the present invention is not limited to this. In order to ensure the clearance, h2 may be set smaller than t3 depending on the shape of the inner peripheral edge of the ring groove.

[0069] [Variation 2] FIG. 9 is a partial cross-sectional view of an internal combustion engine 200B including a piston ring structure 120B according to Modification 2 of the embodiment 2. The piston ring structure 120B according to Modification 2 is different from the piston ring structure 120 in that only a first ring groove 201 is formed on the outer peripheral surface 20a of the piston 20, that a top ring 1, a second ring 2, and an oil ring 3 are attached to the first ring groove 201, and that a partition ring indicated by reference numeral 7 is attached to the first ring groove 201 in addition to the partition ring 6. In Modification 2, the first ring groove 201 corresponds to the "ring groove" according to the present invention. In addition, in Modification 2, the partition ring 6, the outer peripheral separating surface 61, the inner peripheral fitting surface 62, the upper partition wall surface 63, and the lower partition wall surface 64 correspond to the "first partition ring", the "first outer peripheral separating surface", the "first inner peripheral fitting surface", the "first upper partition wall surface", and the "first lower partition wall surface" according to the present invention, respectively. The partition ring 7 has an outer peripheral separation surface 71, an inner peripheral fitting surface 72, an upper partition wall surface 73, a lower partition wall surface 74, an upper protrusion 75, and a lower protrusion 76. In the second modification, the partition ring 7, the outer peripheral separation surface 71, the inner peripheral fitting surface 72, the upper partition wall surface 73, and the lower partition wall surface 74 are respectively referred to as a "second partition ring", a "second outer peripheral separation surface", a "second inner peripheral fitting surface", and a "second upper partition wall surface" according to the present invention. " and "second lower partition surface." The partition ring 7 also corresponds to the "partition ring" according to the present invention.

[0070] As shown in FIG. 9, in the piston ring structure 120B, the partition ring 6 and the partition ring 7 are mounted in the first ring groove 201 together with the top ring 1, the second ring 2, and the oil ring 3 in the axial direction of the piston 20. The partition ring 7 is mounted in the first ring groove 201 at a position lower than the partition ring 6. The upper partition wall surface 63 of the partition ring 6 faces the upper groove wall W1 of the first ring groove 201, so that a space in which the top ring 1 can be mounted is defined between the upper groove wall W1 and the upper partition wall surface 63. The upper partition wall surface 73 of the partition ring 7 faces the lower partition wall surface 64 of the partition ring 6, so that a space in which the second ring 2 can be mounted is defined between the lower partition wall surface 64 of the partition ring 6 and the upper partition wall surface 73 of the partition ring 7. The lower partition wall surface 74 of the partition ring 7 faces the lower groove wall W2, so that a space in which the oil ring 3 can be mounted is defined between the lower groove wall W2 and the lower partition wall surface 74. This makes it possible to fit three piston rings in one ring groove.

[0071] In addition, the inner circumferential fitting surface 72 provided on the inner circumferential portion of the partition ring 7 fits with the bottom groove wall W3 in the usage state, thereby forming a contact state with the bottom groove wall W3. In this example, the inner circumferential fitting surface 72 contacts the bottom groove wall W3 over the entire circumference. However, the present invention is not limited to this, and it is sufficient that at least a portion of the second inner circumferential fitting surface contacts the bottom groove wall. In addition, the outer circumferential separating surface 71 provided on the outer circumferential portion of the partition ring 7 ensures a predetermined separation distance d6 between itself and the inner wall surface 10a of the cylinder 10 in the usage state.

[0072] 9, the upper protrusion 75 of the partition ring 7 is provided inward of the upper partition wall surface 73 in the radial direction of the piston 20, and protrudes toward the combustion chamber 30 from the upper partition wall surface 73. The lower protrusion 76 is provided inward of the lower partition wall surface 74 in the radial direction of the piston 20, and protrudes toward the crank chamber 40 from the lower partition wall surface 74.

[0073] In the piston ring structure 120B, the upper protrusion 65 of the partition ring 6 abuts against the upper groove wall W1 of the first ring groove 201, thereby supporting the partition ring 6 in the axial direction of the piston 20. As a result, the upward movement of the partition ring 6 is restricted. In the piston ring structure 120B, the protrusion amount h1 of the upper protrusion 65 is set to be larger than the width t1 of the top ring 1 in the axial direction, and a clearance can be formed between the top ring 1 and the upper groove wall W1 and between the top ring 1 and the upper partition wall surface 63. However, the present invention is not limited to this. In order to ensure the clearance, h1 may be set to be smaller than t1 according to the shape of the inner peripheral edge of the ring groove. Also, in the piston ring structure 120B, the lower protrusion 66 of the partition ring 6 abuts against the upper protrusion 75 of the partition ring 7, thereby supporting the lower protrusion 66 and the upper protrusion 75 in the axial direction of the piston 20. As a result, the downward movement of the partition ring 6 and the upward movement of the partition ring 7 are restricted. Here, in the piston ring structure 120B, the sum of the projection amount h2 of the lower projection 66 and the projection amount h3 of the upper projection 75 is set to be larger than the width t2 of the second ring 2 in the axial direction. This makes it possible to form clearances between the second ring 2 and the lower partition surface 64 and between the second ring 2 and the upper partition surface 73. However, the present invention is not limited to this. Also, in the piston ring structure 120B, the lower projection 76 of the partition ring 7 is supported in the axial direction of the piston 20 by abutting against the lower groove wall W2 of the first ring groove 201. This restricts the partition ring 7 from moving downward. Here, in the piston ring structure 120B, the projection amount h4 of the lower projection 76 is set to be larger than the width t3 of the oil ring 3 in the axial direction. This This makes it possible to form clearances between the oil ring 3 and the lower protrusion 76 and between the oil ring 3 and the lower groove wall W2. However, the present invention is not limited to this. In order to ensure the clearances, h4 may be set smaller than t3 depending on the shape of the inner peripheral edge of the ring groove.

[0074] Note that the second embodiment can be combined with the other embodiments described above. For example, in the above-described piston ring structure 120B, the partition ring 4 of the piston ring structure 110B may be used instead of the partition ring 6. Also, the partition ring 5 of the piston ring structure 110B may be used instead of the partition ring 7. Also, when the partition ring 4 or the partition ring 6 is applied, it may be held by the holding portion H1 of the piston ring structure 110C.

[0075] <Embodiment 3> 10 is a partial cross-sectional view of an internal combustion engine 300 equipped with a piston ring structure 130 according to embodiment 3. The piston ring structure 130 according to embodiment 3 will be described below, focusing on the differences from the piston ring structure 110 according to embodiment 1, and similar configurations will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0076] The piston ring structure 130 includes a first ring groove 201, a second ring groove 202, and a third ring groove 203 for mounting piston rings provided on the outer peripheral surface 20a of the piston 20, a top ring 1, a second ring 2, an oil ring 3, and a partition ring 4. As shown in FIG. 10, the third ring groove 203 is formed at a position lower than the second ring groove 202 on the outer peripheral surface 20a of the piston 20. In the piston ring structure 130, the top ring 1 and the partition ring 4 are mounted in the first ring groove 201, the second ring 2 is mounted in the second ring groove 202, and the oil ring 3 is mounted in the third ring groove 203. In this example, the first ring groove 201 corresponds to the "ring groove" according to the present invention.

[0077] As shown in FIG. 10, in the piston ring structure 130, the partition ring 4 and the top ring 1 are mounted in the first ring groove 201 in line with each other in the axial direction of the piston 20. The upper partition wall surface 43 of the partition ring 4 faces the upper groove wall W1 of the first ring groove 201, so that the upper partition wall surface 43 is in contact with the upper groove wall W1. The lower partition wall surface 44 of the partition ring 4 faces the lower groove wall W2, so that a space in which the top ring 1 can be mounted is defined between the lower groove wall W2 and the lower partition wall surface 44. As shown in FIG. 10, in the piston ring structure 130, the top ring 1 is mounted between the lower groove wall W2 of the first ring groove 201 and the lower partition wall surface 44 of the partition ring 4. Therefore, when the top ring 1 moves upward, the partition ring 4 comes into contact with the top ring 1. In other words, the partition ring 4 is interposed between the upper groove wall W1 of the first ring groove 201 and the top ring 1.

[0078] The piston ring structure 130 according to the third embodiment can also provide the same effects as those of the above-described piston ring structure 110. That is, the partition ring 4 functions as a substitute for a piston land that separates the upper groove wall W1 of the first ring groove 201 and the top ring 1, thereby reducing the number of contact points between the top ring 1 and the inner wall of the ring groove. This makes it possible to suppress defects caused by direct contact between the piston ring and the inner wall of the piston ring groove.

[0079] The third embodiment can be modified as appropriate. For example, a partition ring 4 may be interposed between the lower groove wall W2 of the first ring groove 201 and the top ring 1. In addition, a partition ring 4 may be interposed between the upper groove wall W1 of the second ring groove 202 and the second ring 2, or between the lower groove wall W2 and the second ring 2. The partition ring 4 may be interposed between the upper groove wall W1 of the third ring groove 203 and the oil ring 3, or between the lower groove wall W2 and the oil ring 3. The third embodiment may be combined with the other embodiments described above. For example, in the above piston ring structure 110, the partition ring 4 may be interposed between the upper groove wall W1 of the first ring groove 201 and the top ring 1, or between the lower groove wall W2 and the second ring 2. In the above piston ring structure 110A, the partition ring 4 may be interposed between the upper groove wall W1 of the second ring groove 202 and the second ring 2, or between the lower groove wall W2 and the oil ring 3. In the above piston ring structure 110B, the partition ring 4 may be interposed between the upper groove wall W1 of the first ring groove 201 and the top ring 1, or between the lower groove wall W2 and the oil ring 3.

[0080] <Embodiment 4> 11 is a partial cross-sectional view of an internal combustion engine 400 equipped with a piston ring structure 140 according to embodiment 4. The piston ring structure 140 according to embodiment 4 will be described below, focusing on the differences from the piston ring structure 110 according to embodiment 1, and similar configurations will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0081] 11, the piston ring structure 140 according to the fourth embodiment differs from the piston ring structure 110 in that two partition rings (partition rings 4 and 5) are mounted in a first ring groove 201 so as to overlap in the axial direction of the piston 20. In this example, the first ring groove 201 corresponds to the "ring groove" according to the present invention.

[0082] As shown in FIG. 11, in the piston ring structure 140, the partition ring 4 and the partition ring 5 are mounted in the first ring groove 201 in line with the top ring 1 and the second ring 2 in the axial direction of the piston 20. The partition ring 5 is mounted in the first ring groove 201 at a position lower than the partition ring 4. Furthermore, the partition ring 4 and the partition ring 5 overlap in the axial direction. Specifically, the lower partition wall surface 44 of the partition ring 4 and the upper partition wall surface 53 of the partition ring 5 are in contact with each other. Therefore, no piston ring is interposed between the partition ring 4 and the partition ring 5. As shown in FIG. 11, in the piston ring structure 140, the top ring 1 is mounted between the upper groove wall W1 of the first ring groove 201 and the upper partition wall surface 43 of the partition ring 4, and the second ring 2 is mounted between the lower groove wall W2 of the first ring groove 201 and the lower partition wall surface 54 of the partition ring 5. That is, in the piston ring structure 140, two partition rings 4 and 5 are interposed between the top ring 1 and the second ring 2 in an overlapping manner. In this manner, in the piston ring structure 140, the partition ring 4 and the partition ring 5 cooperate to function in place of one piston land.

[0083] The piston ring structure 140 according to the fourth embodiment can also provide the same effects as the piston ring structure 110 according to the first embodiment. That is, according to the piston ring structure 140, a plurality of piston rings (in this example, the top ring 1 and the second ring 2) can be mounted in one ring groove, and the number of ring grooves can be reduced. This makes it easy to shorten the axial length of the piston 20.

[0084] In the piston ring structure 110 according to the fourth embodiment, the joints G1 of the partition rings 4, 5 are closed against gas or oil. Fig. 12 is a diagram showing the positional relationship of the joints G1 of the two partition rings 4, 5 in the fourth embodiment. Fig. 12 shows the partition rings 4, 5 in the piston ring structure 140 as viewed from the outside in the radial direction. As shown in Fig. 12, in the fourth embodiment, the two partition rings 4, 5 are arranged in the first ring grooves 41 and 42 such that the joints G1 do not overlap with each other in the axial direction. 201. That is, the two partition rings 4 and 5 are disposed so as to cover each other's joint G1. The joint G1 of the partition ring 4 is covered from below by the partition ring 5, and the joint G1 of the partition ring 5 is covered from above by the partition ring 4.

[0085] According to such a piston ring structure 140, the gaps of the partition rings 4, 5 are covered, so that gas is prevented from passing through the gaps G1 of the partition rings 4, 5 to flow to the back side (radial inner side) of the second ring 2, and oil is prevented from passing through the gaps G1 of the partition rings 4, 5 to flow to the back side (radial inner side) of the top ring 1. In other words, the outflow of gas to the crank chamber 40 side (blow-by) and the outflow of oil to the combustion chamber 30 side (oil rising) are suppressed, and blow-by gas and oil consumption can be reduced.

[0086] In the piston ring structure 140, the partition rings 4 and 5 are interposed between the top ring 1 and the second ring 2 in the first ring groove 201, but the position at which the two partition rings are attached is not limited to this. For example, in the piston ring structure 110A shown in FIG. 4, the two partition rings 4 and 5 may be interposed between the second ring 2 and the oil ring 3 in the second ring groove 202 in an overlapping manner. In addition, the number of partition rings attached in an overlapping manner is not limited to two, and may be a number greater than two. Of the multiple partition rings overlapping in the axial direction, at least two adjacent partition rings may be attached to the ring grooves such that their joints do not overlap in the axial direction.

[0087] <Embodiment 5> The partition ring according to the fifth embodiment will be described below. The partition ring according to the fifth embodiment differs from the partition rings according to the first to fourth embodiments in that the joints have a special shape. The partition ring according to the fifth embodiment is also applicable to the piston ring structures according to the first to fourth embodiments. In other words, the special shape of the joints described below is applicable to any of the above-mentioned partition rings 4, 5, 6, and 7. The partition ring according to the fifth embodiment will be described below, focusing on the differences from the partition ring 4 according to the first embodiment, and similar configurations will be denoted by the same reference numerals and detailed descriptions thereof will be omitted.

[0088] Fig. 13 is a diagram for explaining the shape of the joint end of the partition ring 4A according to the fifth embodiment. Fig. 13(A) illustrates the partition ring 4A in use as viewed from the outside in the radial direction, and Fig. 13(B) illustrates the partition ring 4A in use as viewed along the axial direction. Hereinafter, one of the pair of joint ends 410, 420 will be referred to as the first joint end 410, and the other will be referred to as the second joint end 420. In addition, the end face of the first joint end 410 will be referred to as the first end face 410a, and the end face of the second joint end 420 will be referred to as the second end face 420a.

[0089] As shown in Fig. 13(A), the joint G1 of the partition ring 4A has an angled shape (oblique joint) inclined with respect to the axial direction of the partition ring 4A. Specifically, the first end face 410a and the second end face 420a, which face each other to form the joint G1, are inclined with respect to the axial direction, so that the joint G1 has an angled shape. By forming the joint G1 in an angled shape, as shown in Fig. 13(B), a part of the first joint end 410 and a part of the second joint end 420 overlap with each other when viewed in the axial direction of the partition ring 4A.

[0090] According to the partition ring 4A of the fifth embodiment, the first joint end forming the joint G1 Since a part of the portion 410 and a part of the second joint end 420 overlap in the axial view, the first joint end 410 and the second joint end 420 prevent the gas or oil flowing along the axial direction of the piston 20 from passing through the joint G1. In other words, the joint G1 is blocked from the gas or oil flowing along the axial direction of the piston 20. In addition, by making the joint G1 an angle shape inclined with respect to the axial direction, the gap between the end faces 410a, 420a of the joint G1 can be made smaller than when the joint G1 is made a straight shape parallel to the axial direction. Such a partition ring 4A can suppress gas blow-by and oil rising, and reduce blow-by gas and oil consumption. The joint G1 may be inclined in the opposite direction to that shown in FIG. 13(A). In other words, in the embodiment shown in FIG. 13(A), the first joint end 410 is positioned below the second joint end 420, but the joint G1 may be inclined so that the second joint end 420 is positioned below the first joint end 410.

[0091] [Modification of the fifth embodiment] The following describes a modification of the embodiment 5. In the following description, differences from the above-described partition ring 4A will be mainly described, and similar configurations will be denoted by the same reference numerals and detailed description will be omitted.

[0092] [Variation 1] Fig. 14 is a diagram for explaining the shape of the abutment end of the partition ring 4B according to Modification 1 of Embodiment 5. Fig. 14(A) illustrates the partition ring 4B in use as viewed from the outside in the radial direction, and Fig. 14(B) illustrates the partition ring 4B in use as viewed along the axial direction.

[0093] As shown in FIG. 14(A), the joint G1 of the partition ring 4B has a step shape (stepped joint). Specifically, the first joint end 410 has a first convex portion 411 protruding toward the second joint end 420 in the circumferential direction, and the second joint end 420 has a second convex portion 421 protruding toward the first joint end 410 in the circumferential direction, and in a used state, the first convex portion 411 overlaps the second convex portion 421 in the axial direction. That is, the lower surface 411a of the first convex portion 411 and the upper surface 421a of the second convex portion 421 abut against each other. As the first convex portion 411 and the second convex portion 421 overlap in the axial direction, as shown in FIG. 14(B), a part of the first joint end 410 and a part of the second joint end 420 overlap when viewed in the axial direction of the partition ring 4B.

[0094] According to the partition ring 4B according to the first modification of the fifth embodiment, the first convex portion 411, which is a part of the first joint end portion 410 forming the joint G1, and the second convex portion 421, which is a part of the second joint end portion 420, overlap in the axial direction, so that the first convex portion 411 and the second convex portion 421 prevent the gas or oil flowing along the axial direction of the piston 20 from passing through the joint G1. That is, the joint G1 is blocked against the gas or oil flowing along the axial direction of the piston 20. Furthermore, the lower surface 411a of the first convex portion 411 and the upper surface 421a of the second convex portion 421 abut against each other, so that the gas or oil is prevented from passing between the first convex portion 411 and the second convex portion 421. The partition ring 4B can also reduce the blow-by gas and oil consumption. The shape of the joint may be upside down from that shown in FIG. 14(A). In other words, in the embodiment shown in Figure 14 (A), the first convex portion 411 of the first joint end 410 is positioned above the second convex portion 421 of the second joint end 420, but the second convex portion 421 may also be positioned above the first convex portion 411.

[0095] [Variation 2] Fig. 15 is a diagram for explaining the shape of the joint end of a partition ring 4C according to Modification 2 of the fifth embodiment. Fig. 15(A) illustrates the partition ring 4C in use as viewed from the outside in the radial direction, and Fig. 15(B) illustrates the partition ring 4C in use as viewed from the outside in the radial direction. 13 shows the partition ring 4C as viewed in the axial direction.

[0096] As shown in FIG. 15(A), the joint G1 of the partition ring 4C has a so-called hook step shape. The partition ring 4C is different from the partition ring 4B according to the first modification in that a first protrusion 412 is provided on a lower surface 411a of a first convex portion 411 of the first joint end 410, and a second protrusion 422 is provided on an upper surface 421a of a second convex portion 421 of the second joint end 420. In a use state, the second protrusion 422 abuts on the lower surface 411a of the first convex portion 411, and the first protrusion 412 abuts on the upper surface 421a of the second convex portion 421. As shown in FIG. 15(B), a part of the first joint end 410 and a part of the second joint end 420 overlap each other when viewed in the axial direction of the partition ring 4C.

[0097] The partition ring 4C according to the modified example 2 of the embodiment 5 can reduce blow-by gas and oil consumption, similarly to the partition ring 4B according to the modified example 1. Note that, similarly to the modified example 1, the shape of the abutment may be upside down from that shown in FIG.

[0098] [Variation 3] Fig. 16 is a diagram for explaining the shape of the abutment end of a partition ring 4D according to Modification 3 of Embodiment 5. Fig. 16(A) is a perspective view of the partition ring 4D in a used state, and Fig. 16(B) is a perspective view of the partition ring 4D in a free state. Fig. 17 is a diagram showing the partition ring 4D in a used state as viewed along the axial direction.

[0099] As shown in FIG. 16(A) and FIG. 16(B), the first joint end 410 has a first convex portion 411 protruding toward the second joint end 420 in the circumferential direction, and the second joint end 420 has a second convex portion 421 protruding toward the first joint end 410 in the circumferential direction, and in the use state, the first convex portion 411 is located outside the second convex portion 421 in the radial direction. Here, the surface of the first convex portion 411 facing inward in the radial direction is the first inner side surface 411b, and the surface of the second convex portion 421 facing outward in the radial direction is the second outer side surface 421b. The first inner side surface 411b and the second outer side surface 421b are inclined with respect to the axial direction and abut against each other in the use state. As a result, in the use state, a part of the second convex portion 421 overlaps a part of the first convex portion 411 in the axial direction. 17, the first convex portion 411, which is a part of the first joint end portion 410, and the second convex portion 421, which is a part of the second joint end portion 420, overlap each other in the axial view of the partition ring 4D. Therefore, the first convex portion 411 and the second convex portion 421 prevent gas and oil flowing along the axial direction of the piston 20 from passing through the joint G1. That is, a part of the joint G1 is blocked from gas or oil flowing along the axial direction of the piston 20. Furthermore, the first inner surface 411b of the first convex portion 411 and the second outer surface 421b of the second convex portion 421 abut against each other, thereby preventing gas and oil from passing between the first convex portion 411 and the second convex portion 421.

[0100] According to the partition ring 4D according to the third modification of the fifth embodiment, blow-by gas and oil consumption can be reduced, similarly to the partition ring 4B according to the first modification. The shape of the joint shown in FIG. 16 is a so-called angle joint in which the cross-sectional shape of the first convex portion 411 is substantially triangular, but the shape of the joint may be a so-called rectangular joint in which the cross-sectional shape of the first convex portion 411 is substantially quadrangular. The shape of the joint may be upside down from that shown in FIG. 16. That is, the first inner side surface 411b and the second outer side surface 421b may be inclined in the opposite direction to that shown in FIG. 16. The shape of the joint may be reversed in the circumferential direction from that shown in FIG. 16. That is, the first convex portion 411 may be provided at the second joint end portion 420, and the second convex portion 421 may be provided at the first joint end portion 410.

[0101] [Variation 4] Fig. 18 is a diagram for explaining the shape of the abutment end of a partition ring 4E according to Modification 4 of Embodiment 5. Fig. 18(A) is a perspective view of the partition ring 4E in a used state, and Fig. 18(B) is a perspective view of the partition ring 4E in a free state. Fig. 19 is a diagram showing the partition ring 4E in a used state as viewed along the axial direction.

[0102] As shown in FIG. 18(A) and FIG. 18(B), a first convex portion 411 is formed at the lower part of the outer periphery side of the first joint end 410, protruding toward the second joint end 420 in the circumferential direction. In addition, a second recess 423 into which the first convex portion 411 is fitted in the use state is formed in the second joint end 420 by cutting out the lower part of the outer periphery side of the second joint end 420. Here, the surface of the second recess 423 that faces the upper surface 411c of the first convex portion 411 in the use state is defined as the facing surface 423c. The upper surface 411c and the facing surface 423c are inclined with respect to the axial direction and abut against each other in the use state. As a result, in the use state, a part of the second joint end 420 overlaps a part of the first joint end 410 in the axial direction. Therefore, as shown in FIG. 19, a part of the first joint end 410 and a part of the second joint end 420 overlap in the axial direction of the partition ring 4E. Therefore, the first and second joint ends 410 and 420 prevent gas and oil flowing along the axial direction of the piston 20 from passing through the joint G1. That is, the joint G1 is closed to the gas or oil flowing along the axial direction of the piston 20. Furthermore, the upper surface 411c of the first convex portion 411 and the opposing surface 423c of the second concave portion 423 abut against each other, thereby preventing the gas and oil from passing between the first convex portion 411 and the joint end 420.

[0103] According to the partition ring 4E according to the fourth modification of the fifth embodiment, blow-by gas and oil consumption can be reduced, similarly to the partition ring 4B according to the first modification. The shape of the joint shown in FIG. 18 is a so-called angle joint in which the cross-sectional shape of the first convex portion 411 is substantially triangular, but the shape of the joint may be a so-called rectangular joint in which the cross-sectional shape of the first convex portion 411 is substantially quadrangular. The shape of the joint may be upside down from that shown in FIG. 18. That is, the first convex portion 411 may be formed on the upper part of the outer circumferential side of the first joint end portion 410, and the second recessed portion 423 may be formed on the upper part of the outer circumferential side of the second joint end portion 420. The shape of the joint may be upside down from that shown in FIG. 18 in the circumferential direction. That is, the first convex portion 411 may be provided on the second joint end portion 420, and the second recessed portion 423 may be provided on the first joint end portion 410.

[0104] As described above, in the fifth embodiment, the joint of the partition ring is formed into a special shape, so that at least a part of the joint is blocked from the gas or oil flowing along the axial direction of the piston. The shape of the joint of the partition ring according to the present invention is not limited to the shape described in the fifth embodiment. The special shape may be any shape in which at least a part of the first joint end and at least a part of the second joint end overlap when viewed in the axial direction. As such a special shape, in addition to the shapes of the partition rings 4A to 4E, for example, a double step shape, a double angle shape, or a double round shape may be adopted. In the present invention, the shape of the joint does not have to be a special shape, and may be a straight shape parallel to the axial direction.

[0105] <Embodiment 6> Next, a partition ring according to embodiment 6 will be described. The partition ring according to embodiment 6 differs from the partition rings according to embodiments 1 to 5 in that the joints are blocked by blocking members. The partition ring according to embodiment 6 is also applicable to the piston ring structures according to embodiments 1 to 4. Below, the partition ring according to embodiment 6 will be described focusing on the differences from the partition ring 4 according to embodiment 1, and similar configurations will be denoted by the same reference numerals and detailed descriptions thereof will be omitted.

[0106] FIG. 20 is a diagram for explaining a joint portion of a partition ring 4F according to the sixth embodiment. FIG. 20 shows the partition ring 4F in use as viewed along the axial direction.

[0107] As shown in Fig. 20, the partition ring 4F has a blocking portion 50 that blocks the gap G1 by filling the gap G1. This blocks the gap G1 from gas or oil. The blocking portion 50 is formed of a sealing material. As the sealing material for forming the blocking portion 50, various materials having excellent heat resistance can be used, such as highly heat-resistant resins such as PI (Polyimide) resin, PAI (Polyamide-imide) resin, silicone (silicon resin), and fluororesin, as well as copper-based soft metals.

[0108] According to the partition ring 4F of the sixth embodiment, the gap G1 is blocked by the blocking portion 50, so that gas and oil can be prevented from passing through the gap G1. As a result, gas blow-by and oil rising can be prevented, and blow-by gas and oil consumption can be reduced. According to such a partition ring 4F, blow-by gas and oil consumption can be reduced.

[0109] <Other> 21 to 35 are cross-sectional views showing variations of the partition ring. In FIG. 21 to FIG. 35, cross sections perpendicular to the circumferential direction of the partition ring are shown. The outer peripheral separation surface 41 of the partition ring 4a shown in FIG. 21 is formed by connecting a tapered surface inclined so as to widen from the upper partition wall surface 43 toward the lower side and a tapered surface inclined so as to widen from the lower partition wall surface 44 toward the upper side. The outer peripheral separation surface 41 of the partition ring 4b shown in FIG. 22 is formed by a tapered surface inclined so as to widen toward the lower side. The outer peripheral separation surface 41 of the partition ring 4c shown in FIG. 23 is formed by connecting a tapered surface inclined so as to narrow from the upper partition wall surface 43 toward the lower side and a tapered surface inclined so as to narrow from the lower partition wall surface 44 toward the upper side. The inner peripheral fitting surface 42 of the partition ring 4d shown in FIG. 24 is formed by curving so as to be recessed inward in the radial direction. The inner peripheral fitting surface 42 of the partition ring 4e shown in FIG. 25 is formed by connecting a tapered surface inclined so as to widen from the upper partition wall surface 43 toward the lower side and a tapered surface inclined so as to widen from the lower partition wall surface 44 toward the upper side. The upper partition wall surface 43 of the partition ring 4f shown in FIG. 26 is formed to be curved so as to bulge upward. The lower partition wall surface 44 of the partition ring 4f shown in FIG. 27 is formed with a groove 45 extending along the circumferential direction of the partition ring 4g. In the partition ring 4h shown in FIG. 28, the groove 45 is formed in the upper partition wall surface 43. In the partition ring 4i shown in FIG. 29, the groove 45 is formed in the outer peripheral separation surface 41. In the partition ring 4j shown in FIG. 30, the groove 45 is formed in the inner peripheral fitting surface 42. In addition, in the partition ring 4j, holes 46 communicating with the grooves 45 penetrate in the radial direction from the outer circumferential side to the inner circumferential side of the partition ring 4j. In the partition ring 4k shown in Fig. 31, grooves 45 are formed in both the outer circumferential separating surface 41 and the inner circumferential fitting surface 42. In addition, in the partition ring 4k, holes 46 penetrate in the radial direction from the grooves 45 on the outer circumferential side to the grooves 45 on the inner circumferential side.The upper partition wall surface 43 of the partition ring 4l shown in FIG. 32 is inclined downward as it goes radially outward. The lower partition wall surface 44 of the partition ring 4m shown in FIG. 33 is inclined upward as it goes radially outward. The partition ring 4l or the partition ring 4m can be combined with a compression ring having a keystone shape. The upper partition wall surface 43 may be inclined upward as it goes radially outward, or the lower partition wall surface 44 may be inclined downward as it goes radially outward. In addition, both the upper partition wall surface 43 and the lower partition wall surface 44 may be inclined. A chamfer 47 is formed at the lower corner on the outer periphery side of the partition ring 4n shown in FIG. 34. The chamfer 47 may be formed at the upper corner on the outer periphery side. In addition, the chamfer 47 may be formed at the upper corner or lower corner on the inner periphery side. In the partition ring 4n shown in FIG. A chamfering step 48 is formed at a lower corner on the outer periphery of the partition ring 4o. The chamfering step 48 may be formed at an upper corner on the outer periphery. The chamfering step 48 may also be formed at an upper corner or a lower corner on the inner periphery.

[0110] Although the preferred embodiments of the present invention have been described above, the above-mentioned various embodiments can be combined as much as possible. In addition, in the fourth to sixth embodiments, the means for blocking the abutment has been described, but the means for blocking the abutment in the present invention is not limited to the scope of the fourth to sixth embodiments, and may be a abutment shape or abutment blocking (or sealing) method having a similar abutment blocking (or sealing) function. In addition, in the present invention, when a plurality of partition rings are mounted in the ring groove, it is sufficient that at least a portion of the abutment of at least one partition ring is blocked against gas or oil flowing along the axial direction of the piston. [Explanation of symbols]

[0111] 100, 200, 300, 400: Internal combustion engine 110, 120, 130, 140: Piston and piston ring combination structure 10: Cylinder 20: Piston 201, 202: Ring groove 30: Combustion chamber 40: Crankcase 1: Top ring 2: Second Ring 3: Oil ring 4, 4A, 4B, 4C, 4D, 4E, 4F, 5, 6, 7: Partition ring

Claims

1. A piston and piston ring assembly structure for an internal combustion engine, comprising: a ring groove for mounting a piston ring provided on an outer peripheral surface of the piston; One or more piston rings mounted in the ring groove; and one or more partition rings that are mounted in the ring grooves together with the one or more piston rings in the axial direction of the piston, the partition ring has: an upper partition surface facing the upper groove wall surface, which is a groove wall surface on the combustion chamber side of the internal combustion engine, of a pair of inner walls arranged opposite to each other in the ring groove; a lower partition surface facing the lower groove wall surface, which is a groove wall surface on the crank chamber side of the internal combustion engine, of the pair of inner walls arranged opposite to each other in the ring groove; an inner peripheral fitting surface provided on an inner peripheral portion of the partition ring and fitting with a bottom groove wall surface connecting an inner peripheral edge of the upper groove wall surface and an inner peripheral edge of the lower groove wall surface of the ring groove to form a contact state with the bottom groove wall surface; an outer peripheral separating surface provided on an outer peripheral portion of the partition ring, which ensures a predetermined separation distance from an inner wall of a cylinder of the internal combustion engine; and a pair of joint end portions facing each other to form a joint, At least a part of the joint of at least one of the one or more partition rings is blocked from gas or oil flowing along an axial direction of the piston, A plurality of the partition rings overlapping in an axial direction of the piston, Among the plurality of partition rings, at least two adjacent partition rings are mounted in the ring grooves such that their joints do not overlap with each other in the axial direction. A combination structure of piston and piston ring.

2. The pair of joint ends of the partition ring are formed such that at least a part of a first joint end, which is one of the pair of joint ends, and at least a part of a second joint end, which is the other of the pair of joint ends, overlap in the axial direction of the piston.

2. A combination structure of a piston and a piston ring according to claim 1.

3. The partition ring further has a closing portion that closes the gap by filling the gap.

3. A combined structure of a piston and a piston ring according to claim 1 or 2.

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