JP2009150415A - Thrust roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost long lifetime thrust roller bearing for a swash plate type compressor excellent in wear resistance. <P>SOLUTION: The thrust roller bearing includes raceway boards 12, 13 formed by applying heat treatment on cold-finished hoop of surface roughness Rmax≤2 μm provided by cold-rolling of high carbon steel containing 0.9-1.2wt% of carbon, 1.2-1.7wt% of chrome, 0.1-0.5wt% of manganese, and 0.15-0.35wt% of silicon. The raceway boards 12, 13 include a raceway surface 12a at one side in a thickness direction, a flat surface 12b at another side, and an edge part 12h higher than the flat surface 12g in thickness direction height at an edge of the flat surface 12g. Difference of the thickness direction height between the flat surface 12g and the edge part 12h is not greater than 0.02 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thrust roller bearing, and more specifically to a thrust roller bearing used in a swash plate type compressor of a car air conditioner.

  Conventionally, as a bearing for supporting a swash plate of a swash plate compressor used in a car air conditioner or the like, for example, described in Japanese Patent Application Laid-Open No. 2003-65226 (Patent Document 1) or Japanese Patent Application Laid-Open No. 2004-316930 (Patent Document 2). A thrust roller bearing for a swash plate compressor as described above is used.

  The thrust roller bearing rotates at a high speed of about 8000 (r / min), and a thrust load acts on a position (offset) deviated from the bearing rotation axis. Further, the lubricant used in the car air conditioner is a mixture of a refrigerant and refrigerating machine oil and has poor lubricity. As described above, the thrust roller bearing for a swash plate compressor is used under extremely severe conditions.

  The thrust roller bearing configured as described above is derived from its original structure, and differential slip occurs between the inner diameter side and the outer diameter side of the roller even during normal rotation. This slip has an adverse effect on the formation of an oil film on the rolling contact surface, and causes surface damage on the contact surface of the bearing disc and the roller.

In order to reduce the influence of this differential slip, the roller length of the roller may be shortened. However, when the roller length is shortened, the contact surface pressure of the rolling contact surface increases. Due to the increase of the contact surface pressure, a decrease in rolling fatigue life becomes a problem.
JP 2003-65226 A JP 2004-316930 A

  In the above thrust roller bearing, a mixture of refrigerant and refrigeration oil is used as a lubricant. Therefore, due to the demand for improved compressor efficiency, the lubricity of the lubricant tends to decrease more and more, such as a reduction in the mixing ratio of refrigeration oil. is there. Under such lean lubrication, the surface damage of the washer or roller due to differential slip tends to increase.

  As recent technical trends, resource saving, energy saving, and downsizing of component structures have further progressed, and usage conditions have become more severe. For this reason, a thrust roller bearing for a car air conditioner is also required to have a low cost, further less wear, and an improved peeling life.

  Accordingly, an object of the present invention is to provide a thrust roller bearing for a swash plate compressor that is low in cost, excellent in wear resistance, and has a long service life.

  The thrust roller bearing according to the present invention includes a thrust generated by a rotational movement of a main shaft of a swash plate compressor that reciprocates a piston and a reciprocating motion of the piston by rotating a swash plate fixed to the main shaft around the main shaft. In order to support a load, many are arranged at a position in contact with the swash plate. This thrust roller bearing has 0.9 wt% to 1.2 wt% carbon, 1.2 wt% to 1.7 wt% chromium, 0.1 wt% to 0.5 wt% manganese, and 0.15 wt% to There is provided a washer that is formed by subjecting a steel strip having a surface roughness of Rmax ≦ 2 μm, which is obtained by cold rolling a high carbon steel containing 0.35 wt% of silicon, to a heat treatment. The washer has a raceway surface on one side in the thickness direction, a flat surface on the other side, and an edge having a height in the thickness direction higher than the flat surface at the edge of the flat surface. And the difference of the thickness direction height of a flat surface and an edge is 0.02 mm or less.

  By using carbon steel having the above chemical components, the mechanical properties of the washer are improved. Specifically, it is possible to improve hardenability, improve rolling fatigue life and load resistance, reduce friction and wear, improve hardness, and prevent damage to the washer due to press working.

  In addition, the steel sheet manufactured through the cold rolling process can obtain the desired dimensions, surface smoothness, and hardness, so the turning process and surface to adjust the dimensions during the manufacturing process of the washer are smooth. The grinding step and the like can be omitted. Thereby, since the manufacturing process of a washer is simplified, the manufacturing cost of a thrust roller bearing can be reduced. Furthermore, the surface nitrogen-enriched layer obtained by the heat treatment is not removed.

  Furthermore, by setting the surface shape of the washer as described above, it is possible to obtain a thrust roller bearing that can relieve edge stress accompanying deformation of the washer and realize smooth rotation.

  Preferably, the edge part is formed in the outer edge part and inner edge part of a flat surface. And in the whole area of a washer, the difference of the height direction of a flat surface and an edge is 0.02 mm or less. The effect of the present invention can be achieved even if the above relationship is established only by a part of the washer, for example, the outer edge of the flat surface, the inner edge of the flat surface, or the peripheral edge of the through hole formed in the flat surface. Although it can be obtained, a higher effect can be expected if it is established in the entire area of the washer.

  Preferably, the variation in the height in the thickness direction of the edge is 0.01 mm or less in the entire area of the washer.

  Preferably, the difference in nitrogen concentration in the nitrogen-enriched layer formed on the wall surface on one side and the other side in the thickness direction of the washer is within 0.2 wt%. Moreover, it is preferable that the difference in the amount of retained austenite in the nitrogen-enriched layer formed on each of the wall surfaces on one side and the other side in the thickness direction of the washer is within 2 vol%. Furthermore, it is preferable that the difference in the area ratio of the spheroidized carbide in the nitrogen-enriched layer formed on each of the wall surfaces on one side and the other side in the thickness direction of the washer is within 5%.

  By omitting the grinding step after the heat treatment in the washer manufacturing process, the nitrogen-enriched layer formed on the surface of the washer by the heat treatment is not removed. As a result, the nitrogen concentration, the amount of retained austenite, and the area ratio of the spheroidized carbide in the nitrogen-enriched layer are substantially uniform on the one side wall surface and the other side wall surface in the thickness direction of the washer.

  In the present specification, “one side wall surface in the thickness direction” or “the other side wall surface in the thickness direction” refers to the raceway surface or the wall surface on the opposite side to the raceway surface in the thickness direction. On the other hand, the “surface” refers to the entire surface layer surface of the washer such as the wall surface, the outer peripheral surface, and the inner peripheral surface on one side and the other side in the thickness direction.

  Preferably, the tempering temperature of the washer is in the range of 230 ° C to 280 ° C. In order to make the retained austenite 10 vol% or less, the tempering temperature needs to be 230 ° C. or more. On the other hand, if the tempering temperature is 280 ° C. or higher, the hardness becomes HRC 60 or lower and the hardness required for the washer may not be maintained. Therefore, it is desirable to perform high temperature tempering within the range of 230 ° C to 280 ° C.

  Preferably, the area ratio of carbide in the nitrogen-enriched layer on the surface of the washer is 10% to 25%. By setting the area ratio of the carbide in the surface nitrogen-enriched layer within the above range, rolling fatigue life and sliding characteristics are improved.

  Preferably, the amount of retained austenite in the nitrogen-enriched layer on the surface of the washer is 10 vol% or less. By setting the amount of retained austenite in the surface nitrogen-enriched layer to 10 vol% or less, the rolling fatigue life and load resistance under a high load can be improved, and friction and wear can be reduced.

  Preferably, the particle size of the carbide in the nitrogen-enriched layer on the surface of the washer is 5 μm or less. As a result, the rolling fatigue life and load resistance under high loads can be improved, and friction and wear can be reduced.

  According to the present invention, by manufacturing the washer having the above shape from a steel plate having a predetermined chemical component, the lubricity is improved and the wear resistance and seizure resistance due to the reduction of the surface pressure are improved. Further, by making the surface shape of the washer as described above, the edge stress accompanying the deformation of the washer can be relieved. As a result, it is possible to obtain a swash plate type thrust roller bearing having a long life and capable of reducing costs.

  Furthermore, by adopting the above thrust roller bearing for a swash plate compressor, a long-life and highly reliable swash plate compressor can be obtained.

  With reference to FIGS. 8 to 10, swash plate compressors 51, 61, 71 employing a swash plate compressor thrust roller bearing 11 (hereinafter referred to as “thrust roller bearing 11”) according to the present invention will be described. 8 shows a swash plate compressor 51 of a swash plate type, FIG. 9 shows a swash plate compressor 61 of a double swash plate type, and FIG. 10 shows a swash plate compressor 71 of a variable capacity swash plate type. FIG.

  First, referring to FIG. 8, a swash plate type swash plate compressor 51 mainly includes a casing 52, a main shaft 57, a single-side inclined plate 58, and a piston 59. The swash plate compressor 51 is used, for example, to compress refrigerant vapor of a car air conditioner.

  The casing 22 fixes a head case 53 having a low pressure chamber 55 and a high pressure chamber 56 and a cylinder case 54 having a cylinder 54a in which a piston 59 reciprocates with bolts.

  The low pressure chamber 55 has a suction port (not shown) provided in the head case 53, a suction hole 55a communicating with the cylinder 54a, and a valve (not shown) for preventing the reverse flow of the refrigerant vapor from the suction hole 55a. Then, the refrigerant vapor sucked from the suction port is supplied to the cylinder 54a through the suction hole 55a.

  On the other hand, the high-pressure chamber 56 includes a discharge port (not shown) provided in the head case 53, a discharge port 56a communicating with the cylinder 54a, and a valve 56b that prevents the reverse flow of the refrigerant vapor from the discharge port 56a. Then, the refrigerant vapor inside the cylinder 54a compressed by the piston 59 is discharged to the high pressure chamber 56 through the discharge port 56a.

  The main shaft 57 is rotatably supported with respect to the casing 52 by radial roller bearings 57a. A single-sided inclined plate 58 is held inside the cylinder case 54.

  The single-sided inclined plate 58 is fixedly connected to the main shaft 57 while being inclined at a predetermined angle with respect to a plane orthogonal to the rotation axis of the main shaft 57. A piston 59 is connected by a rod on the circumference.

  The piston 59 is connected to the single-sided inclined plate 58, and reciprocates in the axial direction (vertical direction in FIG. 8) in the cylinder 54a as the main shaft 57 rotates. Further, a compression chamber for compressing the refrigerant vapor (in FIG. 8, the volume of the compression chamber is 0) is formed in a region surrounded by the cylinder 54a and the piston 59.

  The operation of the swash plate compressor 51 having the above configuration will be described.

  First, when the main shaft 57 rotates, the piston 59 attached to the one-side inclined plate 58 reciprocates within the cylinder 54a. When the piston 59 moves in the direction of increasing the volume of the compression chamber (downward in FIG. 8), the valve provided in the suction hole 55a is opened, and the refrigerant vapor passes from the low pressure chamber 55 through the suction hole 55a. Move to. At this time, the valve 56b provided at the discharge port 56a is closed to prevent the refrigerant vapor in the high-pressure chamber 56 from flowing back to the compression chamber.

  Next, when the piston 59 moves in the direction of decreasing the volume of the compression chamber (upward in FIG. 8), the piston 59 compresses the refrigerant vapor in the compression chamber and the valve 56b provided in the discharge port 56a is opened. Then, the compressed refrigerant vapor moves to the high pressure chamber 56 through the discharge port 56a. At this time, the valve provided in the suction hole 55 a is closed to prevent the refrigerant vapor in the compression chamber from flowing back to the low pressure chamber 55.

  In the swash plate compressor 51 having the above-described configuration, the piston 59 reciprocates as the single-sided inclined plate 58 rotates integrally with the main shaft 52. At this time, a thrust load is generated by the rotational movement of the main shaft 57 and the reciprocating movement of the piston 59. Therefore, for the purpose of supporting this thrust load, the thrust roller bearing 11 is disposed at a position in contact with the one-side inclined plate 58.

  As another form of the swash plate compressor, a swash plate type swash plate 61 in which the piston 69 is reciprocated by a double-sided inclined plate 68 fixed to the main shaft 67 as shown in FIG. 9, or as shown in FIG. There is a variable capacity swash plate type compressor 71 and the like in which a piston 79 is reciprocated by an inclined plate 78 attached to a main shaft 77 at a variable angle. The basic configuration is the same as that of the swash plate compressor 51 shown in FIG.

  Also in the swash plate compressors 61 and 71, since the inclined plates 68 and 78 receive a thrust load due to the rotational motion of the main shafts 67 and 77 and the reciprocating motion of the pistons 69 and 79, the inclined plates 68 and 78 are thrust roller bearings. 11 is supported.

  Next, with reference to FIGS. 1-6, the manufacturing method of the thrust roller bearing 11 which concerns on one Embodiment of this invention, and the washer 12 and 13 of the thrust roller bearing 11 is demonstrated. 1 is a diagram showing the thrust roller bearing 11, FIG. 2 is a flow chart showing the main manufacturing process of a polished steel plate as a starting material for the raceway 12 and 13, and FIG. 3 is the main production of the raceway 12 and 13. FIG. 4 is an enlarged view of part P in FIG. 1, FIG. 5 is an enlarged view of part R in FIG. 1, and FIG. 6 is an enlarged view of part Q in FIG.

  First, referring to FIG. 1, a thrust roller bearing 11 includes a plurality of rollers 14, a cage 15 that holds the plurality of rollers 14, and a pair of raceways that clamp the plurality of rollers 14 from the thickness direction of the cage 15. Boards 12 and 13 are provided. In addition, the thickness dimension of the washer disks 12 and 13 in this embodiment is 3 mm or less.

  The thrust roller bearing 11 having the above-described configuration has various advantages such as being able to increase the load capacity and rigidity in a simple manner, while differential slip occurs between the bearings 12 and 13 and 14. The roller 14 is purely rolled at the center in the length direction, and relative slip increases linearly as it approaches both ends. In particular, since the roller 14 has a long roller length, the difference in peripheral speed at both ends of the roller 14 is large, and the slip amount is large compared to other bearings.

  For this reason, the wear amount of the bearing discs 12 and 13 is increased in a portion where a large differential slip occurs, and surface-origin type separation occurs in the vicinity of the end of the rolling track. In particular, the thrust roller bearing 11 has a large number of rollers and a narrow internal space, so that the lubricating oil does not easily reach the raceway surface. As a result, surface-origin type peeling is likely to occur due to insufficient lubrication compared to other bearings.

  In addition, a large thrust load is applied to the bearing discs 12 and 13 employed in the thrust roller bearing 11 having the above-described configuration by the rotational motion of the main shafts 57, 67 and 77 and the reciprocating motion of the pistons 58, 68 and 78. Furthermore, a predetermined hardness and surface smoothness are required for the raceway surface on which the roller 14 rolls.

  Therefore, with reference to FIG. 2, a method for manufacturing a steel plate as a starting material for the washer 12 and 13 used in such an environment will be described. First, as materials, 0.9 wt% to 1.2 wt% carbon (C), 1.2 wt% to 1.7 wt% chromium (Cr), and 0.1 wt% to 0.5 wt% manganese (Mn). And a steel slab containing 0.15 wt% to 0.35 wt% of silicon (Si) and other inevitable impurities and iron (Fe) (S11). Moreover, the oxygen concentration in steel shall be 0.0010 wt% or less.

  Carbon (C) is an indispensable element for securing the strength required for the washer disks 12 and 13. Note that 0.9 wt% or more of carbon is required in order to make the hardness of the surfaces and cores of the washer disks 12 and 13 HRC 58 or more. On the other hand, if the carbon content exceeds 1.2 wt%, large carbides are generated on the surfaces of the bearings 12 and 13 to reduce the rolling fatigue life and load resistance, and increase friction and wear. Therefore, the carbon content is desirably in the range of 0.9 wt% to 1.2 wt%. “HRC” indicates Rockwell hardness.

  Chromium (Cr) also improves the hardenability and rolling fatigue life of the washer 12 and 13, secures hardness by carbide, reduces friction and wear, and improves load resistance. It is an indispensable element. In order to obtain a predetermined carbide, 1.2 wt% or more of chromium is required. On the other hand, even if an amount exceeding 1.7 wt% is added, no remarkable effect of addition is observed. Furthermore, if it exceeds 5.0 wt%, large carbides are produced, rolling fatigue life and load resistance are reduced, and friction and wear increase. Therefore, the chromium content is desirably in the range of 1.2 wt% to 1.7 wt%.

  Manganese (Mn) is an element used for deoxidation when manufacturing steel, and is an indispensable element as a starting material for the washer 12 and 13. In order to sufficiently remove oxygen in steel, 0.1 wt% or more of manganese is required. On the other hand, if it exceeds 0.5 wt%, the material becomes brittle, and the washer disks 12 and 13 may be damaged during press working. Therefore, the manganese content is desirably in the range of 0.1 wt% to 0.5 wt%.

  Silicon (Si) is an element unavoidable for steel materials, and the lower limit of the content is 0.15%. On the other hand, if it exceeds 0.35 wt%, the raceway 12 and 13 may be damaged during press working. Therefore, the silicon content is desirably in the range of 0.15 wt% to 0.35 wt%.

  Furthermore, oxygen forms oxides in steel and becomes a starting point for fatigue failure as a non-metallic inclusion, so that the rolling fatigue life and load resistance are reduced, and friction and wear are increased. Therefore, the oxygen concentration in the steel is desirably 0.0010 wt% or less.

  Next, a steel plate is obtained from the above material by hot rolling (S12). By rolling in a heated state, a huge cast structure becomes a fine and high-quality rolled structure. Moreover, since the work hardening of the material can be prevented by rolling in a temperature range equal to or higher than the recrystallization temperature, the thickness can be reduced at a stretch.

  In addition, you may further add the process of annealing the steel plate rolled after the hot rolling process. The crystal grains are refined by annealing, and the crystal orientation is adjusted, so that the surface accuracy and workability are improved.

  Next, pickling is performed for the purpose of rust prevention and removal of an oxide film (scale) attached to the surface of the steel sheet (S13). By removing the oxide film by pickling, production efficiency and product quality in subsequent steps can be improved. The pickling solution includes hydrochloric acid, sulfuric acid, nitric acid, etc., and 5 wt% to 15 wt% of dilute hydrochloric acid is often used at about 40 ° C. to 50 ° C.

  Next, a steel plate having a predetermined size is obtained by cold rolling, and mechanical properties such as hardness and surface smoothness required for the washer 12 and 13 are obtained (S14). By rolling at room temperature, a predetermined plate thickness can be obtained accurately and high smoothness can be obtained. Moreover, since the steel plate is work-hardened by rolling in a temperature region below the recrystallization temperature, the hardness of the steel plate is improved.

  In addition, the wall surface serving as the raceway surface of the raceways 12 and 13 is required to have a surface roughness of Rmax ≦ 1.6 μm from the viewpoint of smooth rolling of the rollers 14. As will be described later, after the shape processing of the bearing discs 12 and 13, only barrel processing that can remove the surface roughness can be performed, and therefore the surface roughness after the cold rolling step is preferably Rmax ≦ 2 μm. Furthermore, from the viewpoint of preventing breakage during press forming, it is desirable that the hardness after the cold rolling step be Hv220 or less. Here, “Rmax” indicates the maximum height, and “Hv” indicates the Vickers hardness.

  Here, the surface roughness, hardness, and plate thickness of the steel sheet obtained by the cold rolling process are the surface roughness of the rolling roll, the bending of the rolling roll, the rolling rate (ratio of the plate thickness before and after rolling), the rolling roll. It is affected by the gap (gap) and the rotation speed. Therefore, in order to obtain a desired surface roughness, hardness, and plate thickness, it is necessary to appropriately set these elements.

  The hot rolling step and the cold rolling step may each have a predetermined thickness in one rolling step, but may be divided into a plurality of times such as rough rolling, intermediate rolling, and finish rolling. It is good also as obtaining the thickness of.

  Next, with reference to FIG. 3, a method for manufacturing the washer 12, 13 according to one embodiment of the present invention will be described. FIG. 3 is a flowchart showing main manufacturing steps of the washer plates 12 and 13. First, a steel plate (polished steel plate) described with reference to FIG. 2 is adopted as a starting material (S21).

  Next, the steel plate is formed into the shape of the washer 12, 13 by press working (S22). Since the above-mentioned starting materials are already in a desired state such as plate thickness and surface roughness by the cold rolling process, steps such as turning can be omitted. As a result, the manufacturing process can be simplified, and the manufacturing cost of the thrust roller bearing 11 can be reduced. In addition, although this press work process is good also as a desired shape by one press work, it is good also as performing a press work in multiple times and obtaining a desired shape. Further, deburring may be performed after press working.

  Next, in order to obtain the mechanical properties required for the washer plates 12, 13, heat treatment including carbonitriding and high-temperature tempering at a tempering temperature of 230 ° C to 280 ° C is performed (S23). By performing the carbonitriding process, a nitrogen-enriched layer is formed on the surface layer of the washer 12, 13. This nitrogen-enriched layer is effective in improving rolling fatigue life and load resistance and reducing friction and wear. The “surface layer” refers to a layer having a thickness of 50 μm from the surface of the washer 12 or 13.

  Here, the nitrogen concentration in the surface nitrogen-enriched layer is preferably in the range of 0.1 wt% to 0.9 wt%. When the nitrogen concentration is less than 0.1 wt%, the above effect is low, and particularly the surface damage life is reduced. On the other hand, when the nitrogen concentration exceeds 0.9 wt%, voids called voids are generated in the material, or the amount of retained austenite increases so much that the hardness is lowered and the life is shortened. The nitrogen concentration can be measured by, for example, EPMA (wavelength dispersion X-ray microanalyzer).

  Moreover, by performing high temperature tempering, not only the high temperature resistance is improved, but also retained austenite is decomposed into tempered martensite and fine carbides of crystal grains (particle size of 5 μm or less). This is particularly effective for improving rolling fatigue life and load resistance under high load conditions and reducing friction and wear.

  In addition, in order to make a retained austenite 10 vol% or less, it is necessary to make tempering temperature 230 degreeC or more. On the other hand, if the tempering temperature is 280 ° C. or higher, the hardness becomes HRC 60 or lower and the required hardness for the washer 12 or 13 may not be maintained. Therefore, it is desirable to perform high temperature tempering within the range of 230 ° C to 280 ° C. The amount of retained austenite can be measured by comparing the diffraction intensities of martensite α (211) by X-ray diffraction and retained austenite γ (220).

  Further, from the viewpoint of improving the rolling fatigue life and the sliding characteristics, the more spheroidized carbide is more desirable. Specifically, the area ratio of the spheroidized carbide in the surface nitrogen-enriched layer is set within a range of 10% to 25%. When the area ratio is less than 10%, the rolling fatigue life and the effect of improving the sliding characteristics can hardly be expected. On the other hand, if the area ratio exceeds 25%, the toughness of the material deteriorates due to coarsening and aggregation of carbides. The area ratio of the spheroidized carbide is a value in the surface layer of 50 μm of the rolling surface after grinding, and after corroding the material surface with a picric acid alcohol solution (picral), using an optical microscope (400 times) Can be observed. In addition, the “spheroidized carbide” in this specification includes not only carbides but also nitrides.

  Furthermore, it is desirable that high temperature tempering is performed not only on the washer 12 and 13 but also on the cage 15. Thereby, since the hardness of the retainer 15 can be made lower than that of the roller 12, it is possible to prevent the surface of the roller 12 from being dented or scratched when assembled.

  Finally, the oxide film (scale) generated on the surface of the washer 12, 13 by the heat treatment is removed (S24). As scale removal processing, there are mechanical methods such as barrel treatment and blast cleaning, and chemical methods such as pickling described above.

  Here, the “barrel process” is a process in which the container is rotated or vibrated in a state where the washer 12, 13, compound, and media are put in the container (barrel). According to this method, the scale can be removed, and the effect of improving the deburring and surface roughness of the washer 12 and 13 can be expected. As described above, the surface roughness of the starting material of the washer 12, 13 is already Rmax ≦ 2 μm after the cold rolling process, so it is necessary for the washer 12, 13 without providing an independent grinding process. A surface roughness Rmax ≦ 1.6 μm can be obtained.

  Further, the load length ratio tp (hereinafter referred to as “TP value”) of the surface of the washer 12, 13 manufactured through the above steps is 95% or more, and the surface roughness parameter Rsk is −2 <Rsk <0. ing. Thereby, a certain amount of dent can be formed in the surface of the washer disks 12 and 13. This dent functions as an oil reservoir and improves oil film forming ability, seizure resistance, and wear resistance.

  The state of Rsk <0 is a state where no convex portion exists on the surface of the washer. That is, if the contact surfaces of the thrust roller bearings 11 are Rsk <0, stress concentration due to contact between the convex portions can be suppressed. On the other hand, when Rsk ≦ −2, minute convex portions are generated around the concave portion, and initial wear tends to occur. Therefore, by setting the value of Rsk within the above range, the oil film forming ability, seizure resistance, and wear resistance are improved, and the long washer disks 12, 13 can be obtained.

  The “load length ratio tp” is a parameter indicating the surface roughness defined by the JIS standard (Japan Industrial Standards: B 0601-1994). Further, the cutting level of the load length ratio tp is 0.3 μm, and the ratio to the maximum height Ry is 5%. “Rsk” is a parameter indicating the surface roughness defined by the JIS standard (B 0601).

  Referring to FIG. 4, the radial bus bar shape passing through the center of the washer 12 is divided into a radially inner region 12b, a radially central region 12c, and a radially outer region 12d. And the radial direction center area | region 12c has a relatively low cross-sectional height compared with the radial direction inner area | region 12b and the radial direction outer area | region 12d, The maximum height difference is set to 30 micrometers or less. FIG. 4 is an enlarged view of 500 times in the vertical direction and 5 times in the horizontal direction. 4 corresponds to the center side of the roller bearing 11 in FIG. 1, and the left side in FIG. 4 corresponds to the outer peripheral side of the roller bearing in FIG.

  Thus, by making the cross-sectional height of the radial center region 12c of the washer 12 lower than the other portions, a uniform oil film can be formed without hindering the flow of the lubricating oil. As a result, the thrust roller bearing 11 excellent in lubricity can be obtained.

  In addition, when the raceway surface is made to be a completely flat surface by grinding as in a washer manufactured by a conventional manufacturing process, there is a possibility that edge stress may be generated at the contact portion due to an attachment error or the like. This is particularly noticeable at the inner and outer edges of the washer.

  On the other hand, when a load is applied to the thrust roller bearing 11 having the surface of the washer 12 as shown in FIG. 4, the raceway surface of the washer 12 is elastically deformed, and the radially inner region 12b, the radially outer region 12d, and the like. The maximum height difference is reduced to about several μm (1 μm to 9 μm). As a result, it is possible to reduce the local contact surface pressure, in particular, the contact surface pressure at the highest position (in FIG. 4, “radial direction inner region 12b”).

  Furthermore, the washer manufactured by the conventional manufacturing process has a non-uniform surface shape such as swell caused by heat treatment. This may promote local contact and obstruct the flow of the lubricating oil. However, in the washer 12 manufactured by the manufacturing process according to the embodiment of the present invention as shown in FIG. 3, the surface shape can be corrected to a uniform state by the tempering process (S23).

  The effect of the present invention can be obtained if at least one surface of the washer 12, that is, the raceway surface 12 a contacting the roller 14 has the above-mentioned surface shape. Further, since the surface of the washer 13 is the same, the description thereof is omitted.

  Referring to FIG. 5, the surface of the washer 12 manufactured in the above process has a flat surface 12e on one side in the thickness direction, and the depth in the thickness direction gradually increases from the edge of the flat surface 12e. An inclined portion 12f that is inclined in the direction is formed.

  If the tip of the inclined portion that is located farthest from the edge of the flat surface 12e in the radial direction is a point A, and a position that is 0.3 mm from the point A in the radial direction toward the flat surface 12e is a measurement position, this measurement is performed. The depth in the thickness direction of the inclined portion 12f at the position is set to be 0.02 mm to 0.3 mm. In this embodiment, the depth in the thickness direction at the measurement position is 0.1 mm. Further, the variation in the depth in the thickness direction of the inclined portion 12f at the measurement position is set to 40 μm or less over the entire circumference of the washer 12.

  The minimum value (0.02 mm) in the above numerical range is a value that can relieve the assumed edge stress of the contact surface pressure below the maximum contact surface pressure. On the other hand, the maximum value (0.3 mm) is a value that is not affected by the burrs (swelling) generated at the end of the opposite surface when the washer shape follows the backup surface due to the load acting on the washer 12. .

  In addition, the flat surface 12e in the thrust roller bearing 11 shown in FIG. 1 refers to the raceway surface 12a in contact with the roller 14 of the raceway 12. The inclined portion 12f is formed at the inner edge portion and the outer edge portion of the raceway surface 12a. Furthermore, when a hole is formed in the washer disk 12, an inclined portion is also formed at the outer edge portion thereof. Since the washer 13 has the same configuration, the description thereof is omitted.

  Further, referring to FIG. 6, in the washer 12 manufactured in the above process, a raceway surface 12a is formed on one side in the thickness direction, and a flat surface 12g parallel to the raceway surface 12a is formed on the other side. An edge portion 12h having a height in the thickness direction higher than that of the flat surface 12g is formed at the edge of the surface 12g.

  Then, the difference in height in the thickness direction between the flat surface 12g and the edge portion 12h (hereinafter referred to as “fogging amount”) is set to 0.02 mm or less. Further, the variation in the height in the thickness direction of the edge 12h is set to 0.01 mm or less over the entire area of the washer 12.

  In the washer 12 formed by press working, it is extremely difficult to reduce the amount of burrs at the edge 12h to zero. However, if the amount of burrs is greater than 0.02 mm, there is a high possibility that only the edge 12h will come into contact with the mating backup surface due to the influence of mounting errors due to deflection. When a load is applied in this state, the washer 12 is bent and the edge stress between the raceway surface 12a and 14 is increased, which causes rotation failure and damage to the thrust roller bearing 11. Therefore, in order to solve the above problem, it is desirable to satisfy the above numerical range.

  In addition, the edge part 12h in the thrust roller bearing 11 shown in FIG. 1 points out the inner edge part and outer edge part of the surface on the opposite side to the track surface 12a. Further, since the washer 13 has the same configuration, the description thereof is omitted.

  According to this invention, the mechanical properties of the washer 12 and 13 are improved, the rolling fatigue life, load resistance, lubricity, oil film formation, and seizure resistance are improved, and friction and wear are reduced. The As a result, long-life and highly reliable swash plate compressors 51, 61, 71 can be obtained.

  Further, by including a cold rolling process in the manufacturing process of the starting material (the process shown in FIG. 2), it is possible to obtain the plate thickness, hardness, surface roughness, and the like necessary for the bearing discs 12 and 13. If it does so, in the manufacturing process (process shown in FIG. 3) of the washer machines 12 and 13, it becomes possible to skip the process of turning or grinding. As a result, the manufacturing process of the washer 12 and 13 is simplified, and the manufacturing cost of the washer 12 and 13 can be reduced.

  Further, since the grinding process after the heat treatment is omitted, the nitrogen-enriched layer formed on the surface layer of the washer 12 or 13 is not removed. As a result, it is possible to obtain the bearings 12 and 13 with improved rolling fatigue life and load resistance and reduced friction and wear. Furthermore, the nitrogen concentration, the amount of retained austenite, and the area ratio of the spheroidized carbide in the nitrogen-enriched layer are substantially uniform on one side wall surface and the other side wall surface in the thickness direction of the washer 12, 13. Specifically, the difference in nitrogen concentration is within 0.2 wt%, the difference in the amount of retained austenite is within 2 vol%, and the difference in the area ratio of the spheroidized carbide is within 5%.

  Next, a test for confirming the effect of the present invention will be described with reference to FIG. 7 and Table 1. 7 shows a front view (left side) and a side view (right side) of the test apparatus 41 for the effect confirmation test, and Table 1 shows the composition of the test piece 44 and the test results.

  First, referring to FIG. 7, the test apparatus 41 is in contact with the test piece 44 attached to the cantilever 42 via the air slider 43, the lower surface of the test piece 44, and the rotation shaft 45 is rotated. A rotating member 46 that rotates, a weight 47 that applies a load to the test piece 44, and a load cell 48 that measures the load. A load of 50 N (maximum contact surface pressure 0.49 GPa) is applied to the contact portion between the test piece 44 and the rotating member 46.

  The test piece 44 is manufactured through the steps of FIGS. Specifically, in the heat treatment step of FIG. 3, Example 1 was subjected to carbonitriding and tempering at 280 ° C., Example 2 subjected to carbonitriding and tempering at 230 ° C., Ten each of four types of Comparative Example 1 subjected to carbonitriding and tempering at 180 ° C. and Comparative Example 2 subjected to ordinary heat treatment and tempering at 180 ° C. are prepared. Table 1 shows the amount of retained austenite (vol%), nitrogen concentration (wt%), and surface hardness (HRC) in each material.

  The surface of the test piece 44 is a flat surface having a surface roughness Ra of 0.10 μm to 0.15 μm. On the other hand, the surface of the rotating member 46 is a curved surface having a curvature radius of 60 mm, and the surface roughness Ra is set to 0.05 μm. And the shape of the contact part with the rotating member 46 of the test piece 44 is an elliptical shape (referred to as a “contact ellipse”) having a major axis of 0.63 mm and a minor axis of 0.31 mm.

  Furthermore, the lower part of the rotating member 46 is immersed in lubricating oil, and the contact portion between the test piece 44 and the rotating member 46 is lubricated. As the lubricating oil, multipurpose oil (VG68) is used. The oil film parameter Λ is set to about 0.3.

  Under the above test conditions, the wear volume ratio was calculated when the rotating shaft 45 having a diameter of 40 mm was rotated at a speed of 0.05 m / s (rotational speed: 24 r / min) for 60 minutes. The results are shown in Table 1. In addition, each value in Table 1 shows the average value of 10 test pieces. The wear volume ratio is a value based on Comparative Example 2.

  Referring to Table 1, it was confirmed that the amount of retained austenite in the test piece 44 decreases as the tempering temperature increases. The reason why the amount of retained austenite in Comparative Example 2 is small is that the amount of precipitated austenite by ordinary heat treatment is small compared to carbonitriding. On the other hand, the surface hardness decreased as the tempering temperature increased. Thereby, tempering is preferably performed within a range of 230 ° C. to 280 ° C. at a high temperature from the viewpoint of reducing the amount of retained austenite and at a low temperature from the viewpoint of improving the surface hardness.

  Further, the nitrogen concentration was 0.3 wt% to 0.4 wt% for each material subjected to carbonitriding treatment (Examples 1 and 2 and Comparative Example 1), whereas Comparative Example 2 subjected to ordinary heat treatment. Was 0 wt%.

  Further, the wear volume ratio of each material (Examples 1 and 2 and Comparative Example 1) subjected to carbonitriding is lower than that of Comparative Example 2 subjected to normal heat treatment, and is lower as the tempering temperature is higher. became. Thereby, it was confirmed that wear resistance is improved by carbonitriding and tempering at a higher temperature.

  Next, another test for confirming the effect of the present invention will be described. The bearings used in the test were roller bearings having a roller diameter of 3 mm, a washer inner diameter of 60 mm, a washer outer diameter of 85 mm, and a washer thickness of 1.5 mm, and seven types of roller bearings with changed TP values and Rsk values ( Examples 3 and 4 and Comparative Examples 3 to 7).

  In the test, the life ratio when rotating at 5000 (r / min) in an atmosphere of 60 ° C. to 80 ° C. under a load of 1000 kgf was measured based on Comparative Example 5. Furthermore, multipurpose oil VG2 (oil film parameter 0.1) was used as the lubricating oil. Table 2 shows the TP value, Rsk value, and test result of the roller bearing used in the test.

  Referring to Table 2, it was confirmed that the bearing life was extended as the TP value increased and the Rsk value decreased. Further, if the TP value is the same, the smaller the Rsk value, the longer the bearing life (Example 4, Comparative Example 3). Similarly, if the Rsk values are the same, the larger the TP value, the longer the bearing life (Example 4, Comparative Example 4).

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The present invention is advantageously used in the manufacture of a washer for a thrust roller bearing for a swash plate compressor.

It is a figure which shows the thrust roller bearing for swash plate type compressors which concerns on one Embodiment of this invention. It is a flowchart which shows the main processes which manufacture a washer. It is a flowchart which shows the main processes which manufacture a washer from a steel plate. It is an enlarged view of the P section of FIG. It is an enlarged view of the R section of FIG. It is an enlarged view of the Q section of FIG. It is a figure which shows the test device for confirming the effect of this invention. It is a figure which shows the swash plate type swash plate type compressor. It is a figure which shows the swash plate type swash plate type compressor. It is a figure which shows a variable capacity swash plate type swash plate type compressor.

Explanation of symbols

  11 Thrust roller bearing, 12, 13 washer, 12a, 13a raceway surface, 12b radial inner region, 12c radial central region, 12d radial outer region, 12e, 12g flat surface, 12f inclined surface, 12h edge, 14 Roller, 15 Cage, 51, 61, 71 Swash plate compressor, 52 Casing, 53 Head case, 54 Cylinder case, 54a Cylinder, 55 Low pressure chamber, 55a Suction hole, 56 High pressure chamber, 56a Discharge port, 56b Valve, 57, 67,77 Main shaft, 57a Radial roller bearing, 58,68,78 Swash plate, 58,68,78 Piston.

Claims (10)

To support the rotational movement of the main shaft of the swash plate compressor that reciprocates the piston and the thrust load generated by the reciprocating movement of the piston by rotating a swash plate fixed to the main shaft around the main shaft. A thrust roller bearing arranged,
The thrust roller bearing includes 0.9 wt% to 1.2 wt% carbon, 1.2 wt% to 1.7 wt% chromium, 0.1 wt% to 0.5 wt% manganese, and 0.15 wt% to A bearing disc formed by subjecting a high-carbon steel containing 0.35 wt% of silicon to cold rolling of a high carbon steel with a heat treatment to a steel strip having a Rmax ≦ 2 μm thickness;
The washer has a raceway surface on one side in the thickness direction,
A flat surface on the other side, and an edge having a height in the thickness direction higher than that of the flat surface at the edge of the flat surface;
A thrust roller bearing, wherein a difference in height in the thickness direction between the flat surface and the edge portion is 0.02 mm or less. The edge is formed on the outer edge and the inner edge of the flat surface,
2. The thrust roller bearing according to claim 1, wherein a difference in height in a thickness direction between the flat surface and the edge portion is 0.02 mm or less in the entire area of the raceway.   The thrust roller bearing according to claim 1 or 2, wherein a variation in height in the thickness direction of the edge portion is 0.01 mm or less over the entire area of the raceway.   The thrust roller bearing according to any one of claims 1 to 3, wherein a difference in nitrogen concentration in a nitrogen-enriched layer formed on each of the wall surfaces on one side and the other side in the thickness direction of the bearing disc is within 0.2 wt%. .   The thrust roller bearing according to any one of claims 1 to 4, wherein a difference in the amount of retained austenite in a nitrogen-enriched layer formed on each of the wall surfaces on one side and the other side in the thickness direction of the bearing disc is within 2 vol%.   The thrust according to any one of claims 1 to 5, wherein the difference in the area ratio of the spheroidized carbide in the nitrogen-enriched layer formed on each of the wall surfaces on one side and the other side in the thickness direction of the washer is within 5%. Roller bearing.   The thrust roller bearing according to claim 1, wherein a tempering temperature of the washer is within a range of 230 ° C. to 280 ° C.   The thrust roller bearing according to any one of claims 1 to 7, wherein an area ratio of carbides in a nitrogen-enriched layer on the surface of the bearing disc is 10% to 25%.   The thrust roller bearing according to any one of claims 1 to 8, wherein the amount of retained austenite in the nitrogen-enriched layer on the surface of the raceway is 10 vol% or less.   The thrust roller bearing according to any one of claims 1 to 9, wherein a particle size of carbide in the nitrogen-enriched layer on the surface of the bearing disc is 5 µm or less.

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