Oil ring

Abstract

An oil ring comprises: a pair of scraper rings, which are formed along the circumferential direction of the oil ring using an annular wire as a base material and are independently arranged in the axial direction of the oil ring; and a spacer expander, which is arranged between the pair of scraper rings, and the base material of the upper scraper ring of the pair of scraper rings located on the crank chamber side of the internal combustion engine in the internal combustion engine is higher in wear resistance than the base material of the lower scraper ring of the pair of scraper rings located on the crank chamber side of the internal combustion engine.

Description

Technical Field

[0001] The present invention relates to an oil ring having a pair of scraper rings. Background Art

[0002] The internal combustion engine installed in ordinary automobiles adopts a structure obtained by attaching a combination of a piston ring (an example of a ring-shaped member) including a compression ring (pressure ring) and an oil ring to the ring groove of the piston. The compression ring has an air sealing function that suppresses the outflow of combustion gas from the combustion chamber side to the crank chamber side (gas leakage) by maintaining airtightness, and an oil sealing function that suppresses oil loss by scraping off excess oil that is not scraped off by the oil ring. The oil ring has an oil sealing function that suppresses the outflow of oil to the combustion chamber side (oil loss) by scraping off excess engine oil (lubricating oil) attached to the inner wall surface of the cylinder to the crank side, and a function to prevent the compression ring and piston from seizing accompanying the operation of the internal combustion engine by adjusting the oil amount so that the lubricating oil film is appropriately maintained on the inner wall surface of the cylinder.

[0003] Here, as an oil ring, a three-piece combined oil ring is widely used, which is composed of a pair of scraper rings (also called side rails) independently arranged in the axial direction of the oil ring and sliding on the inner wall surface of the cylinder, and a spacer expander provided between the pair of scraper rings and applying force to the pair of scraper rings toward the inner wall surface of the cylinder. In this regard, Patent Document 1 discloses an oil ring that reduces oil consumption and friction by making the outer peripheral surface shapes of an upper scraper ring provided on the combustion chamber side and a lower scraper ring provided on the crank chamber side of the pair of scraper rings different.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 008780

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-124288 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In the case of an oil ring having a pair of upper and lower scraper rings, the upper scraper ring disposed on the combustion chamber side slides under a more severe condition than the lower scraper ring disposed on the crank chamber side, so there is a tendency for the upper scraper ring to be more easily worn than the lower scraper ring. When the upper surface of the upper scraper ring is greatly worn due to long-term use, the gap (side clearance) between the upper groove wall of the ring groove and the upper scraper ring will increase, so the oil sealing function of the oil ring may be reduced.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technology capable of preventing a decrease in the oil seal function in an oil ring including a pair of scraper rings.

[0011] Solutions for solving problems

[0012] In order to solve the above-mentioned problems, the present invention adopts the following structure. That is, the present invention is an oil ring assembled to a piston in an internal combustion engine, comprising: a pair of scraper rings, formed along the circumferential direction of the oil ring using an annular wire as a base material, and independently arranged in the axial direction of the oil ring; and a spacer, arranged between the pair of scraper rings, the base material of the upper scraper ring of the pair of scraper rings located on the combustion chamber side of the internal combustion engine being higher in wear resistance than the base material of the lower scraper ring of the pair of scraper rings located on the crank chamber side of the internal combustion engine.

[0013] According to the present invention, by making the wear resistance of the base material of the upper scraper ring disposed on the combustion chamber side higher than the wear resistance of the base material of the lower scraper ring disposed on the crank chamber side, the wear of the upper scraper ring that slides under a more severe condition than the lower scraper ring can be reduced. As a result, the degradation of the oil seal function can be prevented.

[0014] Furthermore, in the present invention, the hardness of the base material of the upper scraper ring may be higher than the hardness of the base material of the lower scraper ring.

[0015] Furthermore, in the present invention, the hardness of the base material of the upper scraper ring may be higher than the hardness of the base material of the lower scraper ring by 30 Hv or more.

[0016] Furthermore, in the present invention, the carbide occupancy area ratio in the surface of the base material of the upper scraper ring may be higher than the carbide occupancy area ratio in the surface of the base material of the lower scraper ring.

[0017] Furthermore, in the present invention, the material of the base material of the upper scraper ring may be different from the material of the base material of the lower scraper ring.

[0018] Effects of the Invention

[0019] According to the present invention, in the oil ring including the pair of scraper rings, it is possible to prevent the oil sealing function from being deteriorated. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a partial cross-sectional view of an internal combustion engine equipped with the oil ring according to the embodiment.

[0021] Figure 2 This is a schematic diagram showing the structure of a reciprocating friction testing machine.

[0022] Figure 3 It is a graph showing the wear amount ratio.

[0023] Figure 4It is a graph showing the wear amount ratio. DETAILED DESCRIPTION

[0024] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the configurations described in the following embodiments do not mean that the technical scope of the present invention is limited to these configurations.

[0025] [Overall composition]

[0026] Figure 1 FIG. 1 is a partial cross-sectional view of an internal combustion engine 100 including an oil ring 40 according to an embodiment. Figure 1 , a cross section perpendicular to the circumferential direction of the oil ring 40 is shown. Figure 1 As shown, in the internal combustion engine 100, a predetermined separation distance is reserved between the inner wall surface 10a of the cylinder 10 and the outer peripheral surface 20a of the piston 20 attached to the cylinder 10, thereby forming a piston gap PC1. In addition, an annular groove 30 having a substantially rectangular cross section is formed on the outer peripheral surface 20a of the piston 20. The annular groove 30 has: an upper wall 301 formed on the combustion chamber side; a lower wall 302 formed on the crank chamber side and facing the upper wall 301; and a connecting wall 303 connecting the inner peripheral edges of the upper wall 301 and the lower wall 302. The oil ring 40 of this embodiment is attached to the annular groove 30.

[0027] The oil ring 40 is assembled to the piston 20 by being attached to the ring groove 30, and is a sliding member that slides on the inner wall surface 10a of the cylinder 10 along with the reciprocating motion of the piston 20. The oil ring 40 is a so-called three-piece combined oil ring, such as Figure 1 As shown, a pair of scraper rings 1 and 2 and a spacer 3 are provided.

[0028] The following, such as Figure 1 As shown in FIG. 1 , the direction along the central axis of the oil ring 40 (axial direction) is defined as the “up-down direction”. In addition, in the axial direction of the oil ring 40, the combustion chamber side ( Figure 1 The upper side in the figure is defined as the “upper side”, and the opposite side, i.e. the crank chamber side ( Figure 1 In the following description of the oil ring 40, unless otherwise specified, the “circumferential direction” refers to the circumferential direction of the oil ring 40, the “radial direction” refers to the radial direction of the oil ring 40, and the “axial direction” refers to the axial direction of the oil ring 40. Figure 1The state in which the oil ring is assembled on the piston attached to the cylinder of the internal combustion engine is referred to as the "use state". In addition, in this specification, the "cylindrical shape" refers to a surface shape that includes a top portion that becomes the largest diameter in the piston ring and is curved in a convex manner toward the radial outside, and is set to include a "symmetrical cylindrical shape" in which the top portion is located at the center of the axial width of the ring, and an "eccentric cylindrical shape" in which the top portion is located closer to the crank chamber side than the center of the axial width of the ring. In addition, in this specification, the "tapered shape" refers to a surface shape that is inclined so as to expand in diameter as it approaches the crank chamber side.

[0029] The pair of scraper rings 1 and 2 are formed in an annular shape along the circumferential direction of the oil ring 40 and are independently separated from each other in the axial direction. Figure 1 As shown, the upper scraper ring 1 as one of a pair of scraper rings 1 and 2 is provided on the upper side (combustion chamber side) of the internal combustion engine 100, and the lower scraper ring 2 as the other of the pair of scraper rings 1 and 2 is provided on the lower side (crank chamber side) of the internal combustion engine 100.

[0030] like Figure 1 As shown, the upper scraper ring 1 includes a base material 1a formed into a ring shape by a wire material for scraper ring and an outer peripheral coating 1b formed on the outer peripheral surface of the base material 1a. The upper scraper ring 1 has: an outer peripheral surface 11, an inner peripheral surface 12, an upper surface 13 and a lower surface 14. The outer peripheral coating 1b is formed on the outer peripheral surface 11. The axial width of the upper scraper ring 1 is defined by the upper surface 13 and the lower surface 14. The upper scraper ring 1 is configured such that the upper surface 13 of the upper scraper ring 1 is opposite to the upper wall 301 of the annular groove 30 in the use state, and slides on the inner wall surface 10a of the cylinder 10 with the outer peripheral surface 11 as a sliding surface.

[0031] like Figure 1 As shown, the lower scraper ring 2 includes a base material 2a formed into a ring shape by a wire material for scraper ring and an outer peripheral coating 2b formed on the outer peripheral surface of the base material 2a. The lower scraper ring 2 has: an outer peripheral surface 21, an inner peripheral surface 22, an upper surface 23 and a lower surface 24. The outer peripheral coating 2b is formed on the outer peripheral surface 21. The axial width of the lower scraper ring 2 is defined by the upper surface 23 and the lower surface 24. The lower scraper ring 2 is configured such that the lower surface 24 is opposed to the lower wall 302 of the annular groove 30 in the use state, and slides on the inner wall surface 10a of the cylinder 10 with the outer peripheral surface 21 as a sliding surface.

[0032] like Figure 1As shown, the spacer expander 3 is provided between a pair of scraper rings 1 and 2, and has self-tensioning force so as to expand the diameter in the use state. Therefore, the upper scraper ring 1 and the lower scraper ring 2 are urged radially outward by the spacer expander 3, and the outer peripheral surface 11 of the upper scraper ring 1 and the outer peripheral surface 21 of the lower scraper ring 2 press the inner wall surface 10a of the cylinder 10. Thus, the oil sealing function is obtained, and the oil film is formed in such a way that the engine oil existing on the inner wall surface 10a of the cylinder 10 has an appropriate thickness. It should be noted that the shape of the spacer expander of the present invention is not particularly limited.

[0033] like Figure 1 As shown, in the oil ring 40 of this embodiment, the outer peripheral surfaces 11 and 21 of the pair of scraper rings 1 and 2 are set to a symmetrical cylindrical shape with low friction. However, in the present invention, the shape of the pair of scraper rings is not limited to Figure 1 The shape shown. For example, in a pair of scraper rings, the outer peripheral surface of the upper scraper ring located on the upper side may be set to an eccentric cylindrical shape with excellent oil scraping performance, and the outer peripheral surface of the lower scraper ring located on the lower side may be set to a symmetrical cylindrical shape with low friction, or the outer peripheral surfaces of both sides may be set to an eccentric cylindrical shape. In this way, the oil consumption of the internal combustion engine 100 can be reduced while suppressing the increase in friction. In addition, the outer peripheral surface of the upper scraper ring may be set to a symmetrical cylindrical shape, and the outer peripheral surface of the lower scraper ring may be set to an eccentric cylindrical shape. In addition, the outer peripheral surface 11 of the upper scraper ring 1 may be set to a conical shape with excellent oil scraping performance, or the outer peripheral surfaces of both sides may be set to a conical shape. In addition, the outer peripheral surface of the upper scraper ring may be set to a conical shape, and the outer peripheral surface of the lower scraper ring may be set to a symmetrical cylindrical shape.

[0034] The oil ring 40 of this embodiment makes the base material 1a of the upper scraper ring 1 different from the base material 2a of the lower scraper ring 2. More specifically, the material of the base material 1a is different from the material of the base material 2a. The base material 1a of the upper scraper ring 1 is formed of SWRH72A, and its hardness is 450Hv or more and 550Hv or less. On the other hand, the base material 2a of the lower scraper ring 2 is formed of SUS440B, and its hardness is 300Hv or more and 420Hv or less. The hardness of the base material 1a is higher than that of the base material 2a, and the difference is 30Hv or more and 150Hv or less. However, the material of the base material of the scraper ring is not limited to the above materials. As the material of the base material of the scraper ring, SUS, SWRH, etc. can be exemplified. In addition, martensitic stainless steel, silicon-chromium steel, aluminum alloy, etc. can also be used as the material of the base material. In this case, the difference in hardness between the base material 1a and the base material 2a can be 270Hv or less, 200Hv or less, or 180Hv or less.

[0035] The peripheral coating 1b and the peripheral coating 2b of this example are formed as DLC-treated films with high wear resistance. It should be noted that the peripheral coating is not limited to the DLC-treated film, and can also be formed as a hard coating including at least one layer of a nitriding-treated film, a Ni-P-plated film, a chrome-plated film, a PVD-treated film, and a DLC-treated film. It should be noted that the configuration of the peripheral coating 1b of the upper scraper ring 1 and the peripheral coating 2b of the lower scraper ring 2 can also be different. In addition, in the present invention, the peripheral coating is not a necessary configuration, and either or both of the upper scraper ring and the lower scraper ring may not have a peripheral coating. In addition, a surface treatment coating including at least one layer of a coating, a resin coating, a chemical treatment coating, an oxidation treatment coating, a nitriding treatment coating, a Ni-P plating treatment coating, a chromium plating treatment coating, a PVD treatment coating, and a DLC treatment coating may be formed on the axial end surface (upper surface 13, lower surface 14) of the upper scraper ring 1 and the axial end surface (upper surface 23, lower surface 24) of the lower scraper ring 2. It should be noted that "coating" refers to a film formed by coating with a paint. In addition, "resin coating" refers to a coating formed by a resin material. Examples of "coating" and "resin coating" include resin coatings formed by water-based or oily resin coatings. "Chemical treatment coating" refers to a coating formed by chemical treatment. Examples of chemical treatment include ferroferric oxide treatment (blackening), phosphate treatment, chromate treatment, etc. In addition, examples of phosphate treatment include manganese phosphate treatment, zinc phosphate treatment, iron phosphate treatment, etc. "Nitriding coating" refers to a coating formed by allowing nitrogen to penetrate into the metal surface through nitriding treatment. "Oxidation coating" refers to a coating formed by oxidizing the metal surface through oxidation treatment. Examples of oxidation treatment include aluminum oxide film treatment. "Ni-P plated coating" refers to a coating formed by electroless Ni-P plating. In addition, "Chrome plated coating" refers to a coating formed by chromium plating. Chromium plating is also called industrial chromium plating. In addition, "PVD (physical vapor deposition) treated coating" refers to a coating formed by the PVD method. In addition, "DLC (Diamond Like Carbon) treated coating" refers to an amorphous hard carbon coating mainly composed of hydrocarbons and allotropes of carbon.

[0036] [About wear resistance]

[0037] Generally speaking, in the case of an oil ring having a pair of upper and lower scraper rings, the upper scraper ring disposed on the combustion chamber side slides under a more severe condition than the lower scraper ring disposed on the crank chamber side, so there is a tendency for the upper scraper ring to be more easily worn than the lower scraper ring. Therefore, when the upper surface (the surface on the combustion chamber side) of the upper scraper ring is greatly worn due to long-term use, the gap (side gap) between the upper groove wall of the ring groove and the upper scraper ring will expand, so the oil sealing function of the oil ring will be reduced, and the oil consumption in the high-speed rotation area of ​​the internal combustion engine may increase.

[0038] In this regard, the oil ring 40 of the present embodiment makes the materials of the base material 1a and the base material 2a different so that the wear resistance of the base material 1a of the upper scraper ring 1 arranged on the combustion chamber side is higher than the wear resistance of the base material 2a of the lower scraper ring 2 arranged on the crank chamber side. Specifically, the material of the base material 1a is set to SWRH72A, and the material of the base material 2a of the lower scraper ring 2 is set to SUS440B, thereby making the hardness of the base material 1a higher than the hardness of the base material 2a. As a result, the wear of the upper scraper ring 1 can be reduced, and the reduction of the oil seal function can be prevented.

[0039] The wear resistance of the base material of the scraper ring was evaluated by a reciprocating friction test using a reciprocating friction tester. Figure 2 This is a schematic diagram showing the structure of a reciprocating friction tester. The reciprocating friction test performed by the reciprocating friction tester uses Figure 2 The test was conducted using a pin-on-plate reciprocating friction tester, the outline of which is shown in FIG. The upper test piece used in the reciprocating friction test is a pin simulating the base material of the scraper ring, and the material of the pin is the same as the wire material for the scraper ring. It should be noted that the diameter of the pin used for the upper test piece is 8 mm, and the top end (sliding surface) of the pin is a component that has been mirror-polished in such a way that the radius of curvature becomes 18 mm. In addition, the lower test piece uses a disk simulating a piston (equivalent to AC8A material).

[0040] In the reciprocating friction test, the lower test piece is stroked by the movable block, thereby sliding the lower test piece relative to the upper test piece. Lubricating oil is supplied to the sliding interface between the upper and lower test pieces using a tube pump and an air distributor. The test conditions at this time are as follows.

[0041] <Test conditions>

[0042] Stroke: 50mm

[0043] Loading capacity: 50N

[0044] Speed: 200cycle / min

[0045] Lubricating oil: 0W-20

[0046] The pin simulating the base material 1a of the upper scraper ring 1 was set as the upper test piece A, and the pin simulating the base material 2a of the lower scraper ring 2 was set as the upper test piece B. Reciprocating friction tests were performed and the wear amount was compared. The material of the upper test piece A was SWRH72A, which was the same as the base material 1a, and the material of the upper test piece B was SUS440B, which was the same as the base material 2a. Figure 3 is a graph showing the results of the reciprocating friction test, and is a graph showing the wear ratio. The results of the measurement show that the wear ratio of the upper test piece A and the upper test piece B is as follows: Figure 3 As shown, the upper test piece A:upper test piece B=0.2:1.0. It can be seen from this that the wear resistance of the base material 1a of the upper scraper ring 1 is higher than the wear resistance of the base material 2a of the lower scraper ring 2.

[0047] [Function / Effect]

[0048] As described above, the oil ring 40 of the present embodiment makes the materials of the base materials of the pair of scraper rings 1 and 2 different from each other so that the wear resistance of the base material 1a of the upper scraper ring 1 is higher than the wear resistance of the base material 2a of the lower scraper ring 2. Specifically, the material of the base material 1a is set to a SWRH material with a higher hardness than the SUS material as the material of the base material 2a. By making the wear resistance of the base material 1a higher than the wear resistance of the base material 2a, the wear of the upper scraper ring 1 can be reduced, and the reduction of the oil seal function can be prevented. According to such characteristics, the oil ring 40 of the embodiment can be applied to gasoline engines and engines using low-viscosity oil in which there are many opportunities for the scraper ring to directly contact the inner wall of the ring groove. However, the internal combustion engine to which the oil ring of the present invention is applied is not limited to these. Here, the oil ring 40 of the present embodiment makes the material of the base material 1a of the upper scraper ring 1 different from the material of the base material 2a of the lower scraper ring 2 to make the hardness of the base material 1a higher than the hardness of the base material 2a, thereby making the wear resistance of the base material 1a higher than the wear resistance of the base material 2a. The hardness difference between the substrate 1a and the substrate 2a is not particularly limited, but it is preferred that the hardness of the substrate 1a of the upper scraper ring 1 is 30 Hv or more higher than the hardness of the substrate 2a of the lower scraper ring 2, as in the oil ring 40 of the present embodiment. In addition, in the oil ring 40 of the present embodiment, the surface colors of the pair of scraper rings 1 and 2 are different from each other by making the materials of the substrates of the pair of scraper rings 1 and 2 different. Thus, the distinguishability of the pair of scraper rings 1 and 2 can be improved.

[0049] [Modifications]

[0050] In the following description, the differences from the above-mentioned oil ring are mainly described, and detailed descriptions of the same configurations are omitted.

[0051] [Modification 1]

[0052] The oil ring 40 of the modification example 1 makes the material of the base material 1a of the upper scraper ring 1 and the material of the base material 2a of the lower scraper ring 2 the same, and makes the hardness of the base materials of the pair of scraper rings 1 and 2 different from each other, so that the wear resistance of the base material 1a of the upper scraper ring 1 is higher than the wear resistance of the base material 2a of the lower scraper ring 2. In the case of the modification example 1, for example, the hardness can be made different by making the heat treatment method different. According to the modification example 1, by making the hardness of the base material 1a of the upper scraper ring 1 higher than the hardness of the base material 2a of the lower scraper ring 2, the wear resistance of the upper scraper ring 1 can be improved, and the reduction of the oil seal function can be prevented. There is no particular limitation on the hardness difference between the base material 1a and the base material 2a, but it is preferred that the hardness of the base material 1a of the upper scraper ring 1 is higher than the hardness of the base material 2a of the lower scraper ring 2 by 30 Hv or more.

[0053] [Modification 2]

[0054] The carbide occupancy area ratio (carbide precipitation ratio) in the substrate surface of a pair of scraper rings 1 and 2 is made different from each other so that the wear resistance of the substrate 1a of the upper scraper ring 1 of the oil ring 40 of the modified example 2 is higher than the wear resistance of the substrate 2a of the lower scraper ring 2. The carbide occupancy area ratio refers to the ratio of the area occupied by carbides on the surface of the scraper ring. The carbide occupancy area ratio is obtained, for example, by obtaining an image of the substrate surface using a metal microscope after etching with Marble reagent, binarizing the obtained image, and calculating the area ratio of the white portion. However, the calculation method of the carbide occupancy area ratio is not limited to this.

[0055] In Modification 2, stainless steel having different carbon and chromium contents is used for the base material 1a of the upper scraper ring 1 and the base material 2a of the lower scraper ring 2. More specifically, the base material 1a of the upper scraper ring 1 is made of 17-chromium SUS material, which is a martensitic stainless steel containing a large amount of chromium, and the base material 2a of the lower scraper ring 2 is made of 13-chromium SUS material, which is a stainless steel containing a slightly smaller amount of chromium. However, the material of the scraper ring of the present invention is not limited thereto. In Modification 2, using the above-mentioned calculation method, the carbide occupancy area ratio of the base material 1a of the upper scraper ring 1 is 7.2% to 15.3%, and the carbide occupancy area ratio of the base material 2a of the lower scraper ring 2 is 0.2% to 2.0%. That is, in Modification 2, the carbide occupancy area ratio of the base material 1a of the upper scraper ring 1 is higher than the carbide occupancy area ratio of the base material 2a of the lower scraper ring 2, and the difference is 5.2% or more.

[0056] It should be noted that in the second modification, the materials of the substrate 1a of the upper scraper ring 1 and the substrate 2a of the lower scraper ring 2 may be the same. When the materials of the substrate 1a and the substrate 2a are the same, for example, by making the heat treatment method different, the size of the carbide can be changed, and the carbide occupancy area ratio can be made different. In addition, the carbide occupancy area ratio can be made different by making the materials of the substrates of the upper scraper ring 1 and the lower scraper ring 2 different from each other.

[0057] As described above, in variant 2, the substrates of a pair of scraper rings 1 and 2 are made different from each other so that the carbide occupancy area ratio of the substrate 1a of the upper scraper ring 1 is higher than the carbide occupancy area ratio of the substrate 2a of the lower scraper ring 2. By making the carbide occupancy area ratio of the substrate 1a of the upper scraper ring 1 higher than the carbide occupancy area ratio of the substrate 2a of the lower scraper ring 2, the wear resistance of the upper scraper ring 1 can be improved and the reduction of the oil seal function can be prevented. It should be noted that the difference in the carbide occupancy area ratio between the substrate 1a and the substrate 2a is not particularly limited. In addition, in variant 2, by making the carbide occupancy area ratio in the substrate surface of the pair of scraper rings 1 and 2 different, the surface colors of the pair of scraper rings 1 and 2 are made different. As a result, the distinguishability of the pair of scraper rings 1 and 2 can be improved.

[0058] The wear resistance of the base material of the scraper ring of the modified example 2 was evaluated by the above-mentioned reciprocating friction test. The pin simulating the base material 1a of the upper scraper ring 1 was set as the upper test piece C, and the pin simulating the base material 2a of the lower scraper ring 2 was set as the upper test piece D. The reciprocating friction test was performed respectively, and the wear amount was compared. The material of the upper test piece C used the same 17-chromium SUS material as the base material 1a, and the material of the upper test piece D used the same 13-chromium SUS material as the base material 2a. In addition, using the above-mentioned calculation method, the carbide occupancy area ratio of the upper test piece C was set to 7.2% to 15.3%, and the carbide occupancy area ratio of the upper test piece D was set to 0.2% to 2.0%, so that the difference in the carbide occupancy area ratio was 5.2% or more. Figure 4 is a graph showing the results of the reciprocating friction test, and is a graph showing the wear ratio. Figure 4 As shown, the result obtained is that the wear resistance of the upper test piece C of the upper scraper ring 1 having a large carbide occupied area ratio is higher than the wear resistance of the upper test piece D of the lower scraper ring 2 .

[0059] <Other>

[0060] As mentioned above, although the preferred embodiment of the present invention was described, the above-mentioned various aspects can be combined as much as possible.

[0061] Description of reference numerals:

[0062] 100: Internal combustion engine;

[0063] 10: Cylinder;

[0064] 20: Piston;

[0065] 30: ring groove;

[0066] 40: oil ring;

[0067] 1: Upper scraper ring;

[0068] 2: Lower scraper ring;

[0069] 3: septal dilator;

[0070] 1a, 2a: substrate.

Claims

1. An oil ring assembled on a piston in an internal combustion engine, comprising: A pair of scraper rings are formed along the circumferential direction of the oil ring using an annular wire as a base material and are independently arranged in the axial direction of the oil ring; and a spacer is arranged between the pair of scraper rings. The material of the substrate of the upper scraper ring is different from that of the lower scraper ring in the pair of scraper rings, so as to reduce the wear of the upper scraper ring in such a way that the wear resistance of the substrate of the upper scraper ring in the pair of scraper rings is higher than that of the substrate of the lower scraper ring in the pair of scraper rings, so as to reduce the wear of the upper scraper ring in such a way that the wear resistance of the substrate of the upper scraper ring in the pair of scraper rings is higher than that of the substrate of the lower scraper ring in the pair of scraper rings, and so that the surface colors of the pair of scraper rings are different from each other.

2. The oil ring according to claim 1, wherein: The hardness of the base material of the upper scraper ring is higher than the hardness of the base material of the lower scraper ring.

3. The oil ring according to claim 1 or 2, wherein: The hardness of the base material of the upper scraper ring is higher than the hardness of the base material of the lower scraper ring by 30 Hv or more.

4. The oil ring according to claim 1, wherein: The carbide occupancy area ratio in the surface of the base material of the upper scraper ring is higher than the carbide occupancy area ratio in the surface of the base material of the lower scraper ring.

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