JP2005195148A - Thrust needle roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-lived thrust needle roller bearing having effect on early breakage in surface damage such as peeling starting from a surface and also on normal load depending type rolling fatigue. <P>SOLUTION: In the thrust needle roller bearing 10A having a raceway ring 1 made of a thin steel plate and a needle roller 2, at least the raceway ring 1 has a nitrogen enriched layer on a surface layer part, and a residual austenite amount of the surface layer part is 5-25 vol.%. The austenite grain size number of the surface layer part is ≥11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thrust needle roller bearing, and more particularly to a thrust needle roller bearing for a car air conditioner / compressor and an automatic transmission.

  Thrust needle roller bearings are composed of needle rollers, cages, and bearing rings, and have a structure in which the needle rollers and the bearing rings are in line contact with each other. Therefore, high load capacity and high rigidity are achieved for a small bearing projected area. Has the advantage to be obtained. Therefore, the thrust needle roller bearing is suitable as a bearing used under severe usage conditions such as operation under lean lubrication or high-speed rotation, and is used in a car air conditioner / compressor or an automatic transmission.

  Such a thrust needle roller bearing is disclosed in, for example, the following Patent Document 1 (Japanese Patent Laid-Open No. 2002-70872).

  Oil used in car air conditioners and compressors has low viscosity, and the amount of oil has been reduced to improve compressor capacity (cooling capacity). Since it is used under such severe conditions under dilute lubrication, when the differential slip of the rollers is large, there is a risk of premature breakage due to surface damage such as surface-initiated peeling.

  In addition, from the viewpoint of energy saving, automobile manufacturers and automatic transmission manufacturers may use additives with conventional oils. Additive-added oils are inferior to ordinary oils in lubrication performance, so current thrust bearings with large roller differential slip are desired to be improved from the viewpoint of surface damage such as surface-origin peeling. .

  In addition, the use conditions of car air conditioners / compressors and automatic transmissions tend to be higher, and improvements are also desired from the viewpoint of internal origin type separation due to normal load-dependent rolling fatigue.

For this reason, there is a demand for a long-life bearing that is effective against early breakage due to surface damage such as surface-origin type delamination and also effective for internal-origin type delamination due to normal load-dependent rolling fatigue. .
JP 2002-70872 A

  The material of the raceway ring in the conventional thrust needle roller bearing is a material of a steel plate and a steel strip that can be pressed and has good workability and availability, such as low carbon structural steel, cold rolled steel plate, Steel strip, medium carbon steel or bearing steel is used. In addition, as heat treatment of the bearing ring, carburization or carbonitriding is performed when low carbon structural steel, cold rolled steel sheet or steel strip is used, and brightness is used when medium carbon steel or bearing steel is used. Quenching or induction hardening is performed.

  Further, bearing steel is used as the material of the roller of the conventional thrust needle roller bearing, and bright quenching or carbonitriding is performed for the heat treatment.

  In the case of a thrust needle roller bearing, damage such as surface-origin type peeling is induced by heat generated by differential sliding of the roller. However, it is desired to strengthen the bearing ring against surface damage such as this surface-origin type peeling.

  In addition, under conditions where a high load is applied, internal origin type peeling due to normal load-dependent rolling fatigue may occur, and a longer life is desired.

  The present invention has been made in view of such circumstances, and at least by changing the properties of the raceway, it is effective for early breakage due to surface damage such as surface-initiated peeling, and is dependent on normal load. An object of the present invention is to provide a long-lasting thrust needle roller bearing that is also effective in rolling fatigue of a mold.

  The thrust needle roller bearing of the present invention is a thrust needle roller bearing having a bearing ring and a needle roller made of a thin steel plate, and at least the bearing ring has a nitrogen-enriched layer in the surface layer portion, and the surface layer portion remains. The amount of austenite is 5% by volume or more and 25% by volume or less, and the austenite grain size number of the surface layer part is 11 or more.

  In the above thrust needle roller bearing, the nitrogen content in the surface layer portion is preferably 0.1% by mass to 0.7% by mass.

  In the thrust needle roller bearing of the present invention, the bearing ring is made of a material having a fine crystal grain size and heat resistance, so that the surface-origin type peeling (surface damage such as peeling and smearing) life and the internal origin type Both the peeling life can be improved.

  Specifically, a carbonitriding structure (nitrogen-enriched layer) that secures the 11th or higher austenite grain size can be obtained by processing materials such as bearing steel and medium carbon steel or by devising a heat treatment pattern. By obtaining such a structure, the resistance to the occurrence and development of cracks can be greatly increased. As a result, it is possible to suppress the generation of surface cracks due to surface heat generation due to slippage and tangential force. Furthermore, the inventors of the present application have found that a considerably long life can be achieved even with respect to internally-origin-type delamination cracks.

  In particular, for surface damage such as surface-initiated peeling, it is necessary to form a heat-resistant nitrogen-enriched layer in which fine carbides are deposited on the surface layer portion. In the present invention, a nitrogen-enriched layer is formed in the surface layer portion, the retained austenite is present in the surface layer portion in an amount of 5% by volume or more, and the austenite crystal grain size in the surface layer portion is as fine as 11 or more. Surface damage such as starting point peeling can be suppressed.

  In addition, the retained austenite present in the nitrogen-enriched layer of the surface layer is a factor that lowers the surface hardness. Therefore, after carbonitriding, reheat to a temperature lower than the temperature during carbonitriding and quenching. Therefore, it is necessary to reduce the amount of retained austenite as compared with the carbonitrided product. In this invention, since the retained austenite of the surface layer part is restrained to 25 volume% or less, the fall of surface hardness can be suppressed.

  Based on the above microstructure, further processing or heat treatment is applied to give a compressive stress to the surface layer and further increase the hardness, thereby extending the life. These processing and heat treatments include (b1) shot peening, (b2) barrel processing, (b3) rolling processing, (b4) carburization treatment + carbonitriding treatment, (b5) carbonitriding treatment + subzero treatment, (b6) A technique such as carbonitriding + secondary quenching + sub-zero treatment can be performed as it is or in combination with the techniques (b1) to (b6).

Further, at least one of the bearing rings and rollers is subjected to a carbonitriding process with the A ₁ transformation point or more, then after cooling to a temperature below the A ₁ transformation point, heated to a temperature lower than the carbonitriding quenching temperature And may be quenched from its quenching temperature.

In the step of performing the carbonitriding process at the carbonitriding temperature and then cooling to less than A ₁ point, it may be cooled to room temperature by oil cooling or the like, or may be a process of cooling to a temperature at which the austenite transformation ends at a predetermined value or more. Good. By the above production method, a metal structure having a nitrogen-enriched layer, fine austenite grains, and containing an appropriate amount of retained austenite can be obtained. For this reason, it is possible to improve both the surface starting type peeling life and the internal starting type peeling life. In addition, a thrust needle roller bearing can be obtained in which a change in size over time is suppressed.

  The nitrogen-enriched layer is formed by carbonitriding as described above, but the nitrogen-enriched layer may or may not be enriched with carbon.

  In such a microstructure, since it is cooled once from the carbonitriding process and then quenched from a quenching temperature lower than the temperature of the carbonitriding process, very fine austenite crystal grains can be obtained. The process of heating and quenching to a quenching temperature lower than the carbonitriding temperature is sometimes referred to as secondary quenching or final quenching from the order of the process.

  Further, the quenching temperature may be a temperature range in which the carbide and / or nitride and the austenite phase coexist at least in the surface layer portion of the carbonitrided steel.

  Since the heating temperature during quenching is lower than the heating temperature during carbonitriding, the amount of undissolved carbide and / or nitride in the surface layer affected by the carbonitriding process is greater than that during carbonitriding. . For this reason, when the quenching temperature is in the above-mentioned coexisting temperature range, the ratio of the amount of undissolved carbide / nitride is increased and the ratio of the austenite amount is decreased at the quenching temperature than in the carbonitriding process. In addition, as determined from the iron-carbon binary phase diagram, in the coexistence region of carbide (cementite) and austenite, the concentration of carbon dissolved in austenite decreases as the quenching temperature decreases. In addition, since the steel used for the bearing has a low content of other alloy elements such as Si (silicon) and Mn (manganese), each temperature region and The generation layer can be discussed. Nitrogen, like carbon, forms a solid solution as an interstitial element in iron, and forms nitrides with iron similar to cementite in a given temperature range. Can do.

  When heated to the quenching temperature, the austenite grains become fine due to the large amount of undissolved carbides and / or nitrides that hinder the growth of the austenite grains. Further, the structure transformed from austenite to martensite by quenching has a slightly richer toughness than the structure quenched from the carbonitriding temperature because the carbon concentration is slightly lower in the case of the above heat treatment. That is, (c1) undissolved carbide / nitride having a larger amount than before, and (c2) a hardened structure having a carbon concentration lower than that of the conventional.

  The quenching temperature may be 780 ° C to 830 ° C. This temperature range can be applied to almost all steel materials, and the management of the quenching temperature can be simplified.

  Further, in at least one of the above-described raceway rings and rollers, cold working such as press working may be performed before carbonitriding.

  By applying such cold working, the nucleation density of austenite grains during heat treatment is increased, and a fine grain structure can be obtained.

  Furthermore, a compressive stress of 500 MPa or more may be applied to at least one of the raceway ring and the roller.

  As described above, it is possible to further extend the life by applying processing and heat treatment to the above-mentioned surface layer based on the above microstructure and applying compressive stress to the above surface layer.

  In addition, the austenite grain size number in this specification is the grain size number of austenite defined in the austenite grain size test method of JIS G 0551.

  In addition, the austenite crystal grains in this specification are austenite crystal grains that have undergone phase transformation during quenching heating, and this remains as a past history even after transformation to martensite by cooling. Say things.

  The austenite crystal grain may be a grain boundary that can be observed by performing a process of revealing the grain boundary, such as etching, on the gold phase sample of the target member. In the sense that it is a grain boundary at the time of heating just before low-temperature quenching, it may be referred to as prior austenite grains. The measurement may be obtained by converting the average value of the particle size number of JIS standard to the average particle size, or the length of the interval between the straight lines in the random direction superimposed on the gold phase structure by the intercept method or the like and associated with the grain boundary. May be taken, and a two-dimensional to three-dimensional interval length may be obtained by applying a correction coefficient.

  Residual austenite is measured using various X-ray diffraction methods, such as obtaining the diffraction intensity of an appropriate austenite phase index and taking the ratio of the diffraction intensity from the appropriate plane index of the ferrite phase. The At that time, the height of the diffraction peak may be used, or the area of the diffraction peak may be used. In addition, using the fact that the austenite phase is a non-magnetic material and the ferrite phase is a ferromagnetic material, it can also be measured by determining the magnetizing force with a magnetic balance or the like. In addition, it can measure easily using a commercially available measuring apparatus.

  In addition, the austenite phase is transformed into martensite during the low-temperature quenching, but the residual austenite remains untransformed to room temperature, for example, between adjacent martensite bundles transformed along different crystal planes. Refers to austenite. Therefore, there is no direct relationship with the austenite crystal grains in which the range of the average grain size is limited.

  Moreover, when the nitrogen content in the surface layer is less than 0.1% by mass, there is no effect, and the rolling life particularly under the foreign matter mixing condition is reduced. When the nitrogen content is more than 0.7% by mass, voids called voids are formed, or the retained austenite increases too much, resulting in a short life. For the nitrogen-enriched layer formed on the raceway, the nitrogen content is the value at the surface layer of 50 μm on the raceway surface after grinding. For example, with EPMA (Electron Probe Micro-Analysis: wavelength dispersive X-ray microanalyzer) Can be measured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a thrust needle roller bearing according to an embodiment of the present invention. Referring to FIG. 1, this thrust needle roller bearing 10 </ b> A includes a pair of race rings 1, 1 made of a thin steel plate and a plurality of needle rollers 2 that roll between the pair of race rings 1, 1. And an annular cage 3 that holds the plurality of needle rollers 2 at a predetermined pitch in the circumferential direction. The bearing ring 1 has a through hole 1a for inserting a shaft or the like at the center.

  At least the bearing ring 1 of this thrust needle roller bearing 10A has a nitrogen-enriched layer in the surface layer portion, the amount of retained austenite in the surface layer portion is 5 volume% or more and 25 volume% or less, and the austenite crystal in the surface layer portion. The particle size number is 11 or more. Moreover, it is preferable that the nitrogen concentration of the surface layer part is 0.05 mass% or more and 0.4 mass% or less.

  In addition to the bearing ring 1, the needle roller 2 or the cage 3 has a nitrogen-enriched layer in the surface layer portion, and the amount of retained austenite in the surface layer portion is 5% by volume or more and 25% by volume or less. The austenite grain size number of the part may be 11 or more. Moreover, 0.05 mass% or more and 0.4 mass% or less may be sufficient as the nitrogen concentration of the surface layer part.

  In the above description, the configuration in which the plurality of needle rollers 2 are arranged in a single row has been described. However, as shown in FIG. 2, the plurality of needle rollers 2 may be arranged in a plurality of rows.

  Referring to FIG. 2, the thrust needle roller bearing 10 </ b> B has double-row needle rollers 2 including needle rollers 2 a on the inner diameter side and needle rollers 2 b on the outer diameter side. In this case, it is preferable that the retainer 3 is configured such that the two annular members 3a and 3b are overlapped with each other. An inner diameter side end portion of the annular member 3a is bent and crimped to the annular member 3b side, and an outer diameter side end portion of the annular member 3b is bent and crimped to the annular member 3a side. It is preferable. As a result, the two annular members 3a and 3b can be firmly clamped and firmly integrated.

  Here, the lengths L1 and L2 of the double-row needle rollers 2a and 2b are the same, but L1 ≦ L2 and L2 ≦ L1 can be selected depending on the use conditions. By making the length L2 of the needle roller 2b on the outer diameter side longer than the length L1 of the needle roller 2a on the inner diameter side, for example, 1.2 times longer, the load capacity on the outer diameter side can be increased. preferable.

  Since the configuration of the thrust needle roller bearing 10B other than the above is substantially the same as the configuration of the thrust needle roller bearing 10A described above, the same members are denoted by the same reference numerals and description thereof is omitted.

  Next, heat treatment including carbonitriding performed on at least one bearing component of the race ring 1, the needle roller 2 and the cage 3 in each of the thrust needle roller bearings 10A and 10B of the present embodiment will be described.

3 and 4 show a heat treatment method for forming the thrust needle roller bearing of the present invention. FIG. 3 is a heat treatment pattern showing a method of performing the primary quenching and the secondary quenching, and FIG. 4 is a method in which the material is cooled below the A ₁ transformation point temperature during the quenching, and then reheated and finally quenched. It is the heat processing pattern which shows. Both are examples of heat treatment of the thrust needle roller bearing of the present invention.

3, first the steel for the bearing parts are heated to the A ₁ transformation point or more carbonitriding temperature (845 ° C.), the carbonitriding steel for the bearing parts is performed at that temperature. In the temperature treatment T ₁ , carbon and nitrogen are diffused in the steel base, and the carbon is sufficiently dissolved in the steel. Thereafter, the steel for bearing parts is subjected to oil quenching from the temperature of treatment T ₁ and cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 230 ° C., but this tempering can be omitted.

Thereafter, the steel for the bearing component is reheated to a temperature lower than the temperature of the carbonitriding process (for example, 800 ° C.) at a temperature equal to or higher than the A ₁ transformation point, and the process T ₂ is performed by holding at that temperature. After that, oil quenching is performed from the temperature of the treatment T ₂ , and it is cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 230 ° C.

Referring to FIG. 4, first, steel for bearing parts is heated to a carbonitriding temperature (845 ° C.) that is equal to or higher than the A ₁ transformation point, and carbonitriding is performed on the steel for bearing parts at that temperature. In the temperature treatment T ₁ , carbon and nitrogen are diffused in the steel base, and the carbon is sufficiently dissolved in the steel. Thereafter, the steel for bearing parts is not quenched and cooled to a temperature below the A ₁ transformation point. Thereafter, the steel for the bearing component is reheated to a temperature lower than the temperature of the carbonitriding process (for example, 800 ° C.) at a temperature equal to or higher than the A ₁ transformation point, and the process T ₂ is performed by holding at that temperature. After that, oil quenching is performed from the temperature of the treatment T ₂ , and it is cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 230 ° C.

  By the carbonitriding process described above, a nitrogen-enriched layer that is a “carbonitriding layer” is formed on the surface layer of steel for bearing parts. Since the carbon concentration of steel used as a material in the carbonitriding process is high, carbon may not easily enter the steel surface from the normal carbonitriding process atmosphere. For example, in the case of steel with a high carbon concentration (steel of about 1% by mass), a carburized layer with a higher carbon concentration may be generated, or a carburized layer with a higher carbon concentration may be difficult to generate. However, the nitrogen concentration depends on the Cr (chromium) concentration, but in ordinary steel, it is as low as about 0.020 mass% or less, so a nitrogen-enriched layer is clearly formed regardless of the carbon concentration of the raw steel. The Needless to say, the nitrogen-enriched layer may be enriched with carbon.

  The above heat treatment is more effective for premature breakage due to surface damage such as surface-origin peeling, while carbonitriding the surface layer than carbonizing (ie, quenching once as it is followed by carbonitriding). In addition, since it is effective for internal origin type peeling due to normal load-dependent rolling fatigue, the life of the thrust needle roller bearing can be extended.

  FIG. 5A shows the austenite grain size of the bearing steel to which the heat treatment pattern shown in FIG. 3 is applied. For comparison, FIG. 5B shows the austenite grain size of the bearing steel obtained by the conventional heat treatment method. FIGS. 6A and 6B show the austenite grain sizes illustrated in FIGS. 5A and 5B. From the structure showing the austenite crystal grain size, the conventional austenite grain size is No. 10 in JI (Japanese Industrial Standard) standard grain size, and according to the heat treatment method of the present invention, No. 12 fine grain can be obtained. . Moreover, the average particle diameter of Fig.5 (a) was 5.6 micrometers as a result of measuring by the intercept method.

  Next, a car air conditioner / compressor using the thrust needle roller bearing 10B (FIG. 2) of the present embodiment will be described.

  FIG. 7 is a schematic cross-sectional view showing a configuration of a compressor using a thrust needle roller bearing according to an embodiment of the present invention. Referring to FIG. 7, for example, a swash plate type swash plate type compressor 100 is shown as a compressor. The swash plate compressor 100 is configured such that a piston 107 reciprocates via a shoe 109 sliding on the swash plate 103 by rotation of a swash plate 103 fixed to a main shaft 104.

  A main shaft 104 to which a swash plate 103 is fixed is rotatably supported in a housing 102 via a radial bearing 105. A plurality of cylinder bores 106 are formed in the housing 102 at equally spaced positions in the circumferential direction, and double-headed pistons 107 are slidably accommodated in the bores 106. A concave portion 108 is formed at the central portion of each piston 107 so as to straddle the outer peripheral portion of the swash plate 103, and a spherical seat is formed on the axially opposed surface of the concave portion 108 to seat a spherical or hemispherical shoe 109. I'm allowed. A shoe 109 is interposed between the swash plate 103 and the piston 107 and functions to smoothly convert the rotational motion of the swash plate 103 into the reciprocating motion of the piston 107.

  The swash plate 103 is fixed to the main shaft 104 and rotates together with the main shaft 104. Since the swash plate 103 functions to reciprocate the piston 107 as described above, a thrust load is generated in the axial direction of the main shaft 104. Therefore, the thrust needle roller bearing 10B is used as a support structure that receives the thrust load. As described above, the thrust needle roller bearing 10B has a pair of race rings 1 and 1, double row needle rollers 2a and 2b, and a cage 3. One of the pair of race rings 1 is assembled to the swash plate 103, and the other of the pair of race rings 1 is assembled to the housing 102 side.

  In the above embodiment, a swash plate type swash plate type compressor has been described as a compressor. However, the thrust needle roller bearing of the present invention is also applicable to other types of swash plate type compressors, scroll type compressors and the like. can do. Other types of swash plate compressors include, for example, a swash plate type swash plate compressor and a swash plate type variable capacity swash plate compressor.

  In the case of the swash plate type swash plate compressor 200, as shown in FIG. 8, a support structure that receives a thrust load between the connecting member 211 and the housing 202 and between the connecting member 211 and the swash plate 203. As shown, a double-row thrust needle roller bearing 10B according to the present embodiment is disposed. The connecting member 211 is a member for connecting the swash plate 203 and the piston 207. In the compressor 200, the swash plate 203 rotates with the rotation of the main shaft 204, whereby the connecting member 211 swings, whereby the piston 207 reciprocates in the cylinder via the piston rod 215.

  In the case of the swash plate type variable displacement swash plate compressor 300, as shown in FIG. 9, the present embodiment is implemented as a support structure for receiving a thrust load between the journal 303 corresponding to the swash plate and the piston support 312. A double-row thrust needle roller bearing 10B of the form is arranged. Further, between the housing 302 and the sleeve 314 of the main shaft 304, the double-row thrust needle roller bearing 10B of the present embodiment is disposed as a support structure that receives a thrust load.

  In this compressor 300, the journal 303 rotates with the rotation of the main shaft 304, whereby the piston support 312 swings, whereby the piston 307 reciprocates in the cylinder via the piston rod 315. In this compressor 300, it is possible to change the inclination angle of the journal 303 by sliding the sleeve 314 connected to the drive pin 313 in the axial direction with respect to the main shaft 304, thereby realizing a variable capacity. ing.

  Next, an automatic transmission using the thrust needle roller bearing 10B (FIG. 2) of the present embodiment will be described.

  FIG. 10 is a schematic cross-sectional view showing a configuration of an automatic transmission using a thrust needle roller bearing according to an embodiment of the present invention. Referring to FIG. 10, the automatic transmission normally includes a torque converter 400 and a planetary gear mechanism (not shown).

  The torque converter 400 mainly includes an impeller 401, a stator 402, and a turbine 403. The thrust needle roller bearing 10B according to the present embodiment as a support structure that receives a thrust load of the transmission is assembled, for example, between the impeller 401 and the stator 402, and between the stator 402 and the turbine 403.

  In this torque converter 400, an impeller 401 connected to the output shaft of the engine and a turbine 403 connected to the input shaft of the transmission are arranged so as to face each other. The stator 402 is attached to a stator shaft fixed to the casing via a one-way clutch 404. The stator 402 changes the flow direction of the fluid when returning the fluid flowing back between the impeller blade 401a and the turbine blade 403a formed in a bowl shape from the turbine 403 side to the impeller 401 side on the inner diameter side thereof. In other words, a forward rotational force is applied to the impeller 401 to amplify the transmission torque.

  As described above, the thrust needle roller bearing 10B between the impeller 401 and the stator 402 includes a pair of race rings 1, 1; double row needle rollers 2a, 2b; and a cage 3. Yes. One of the pair of track rings 1 is assembled to the impeller hub 401b, and the other of the pair of track rings 1 is assembled to the stator 402 side.

  As described above, the thrust needle roller bearing 10B between the stator 402 and the turbine 403 also includes a pair of race rings 1, 1, double rows of needle rollers 2a, 2b, and a cage 3. Yes. One of the pair of track rings 1 is assembled to the turbine hub 403b, and the other of the pair of track rings 1 is assembled to the stator 402 side.

  In the above description, the case where the double-row thrust needle roller bearing 10B is provided in the car air conditioner / compressor or automatic transmission has been described, but instead of the double-row thrust needle roller bearing 10B, the single row shown in FIG. This thrust needle roller bearing 10A may be provided.

  Next, examples of the present invention will be described.

  A press workable steel plate made of SUJ2 material (JIS standard: high carbon chromium bearing steel), SCM415M (JIS standard: chromium molybdenum steel), and S70C (JIS standard: carbon steel for machine structural use) and A steel strip raceway (thickness 3 mm or less) and a roller were prepared. Various heat treatments were applied to the races. Examples of the heat treatment include heat pattern heat treatment (special heat treatment), carbonitriding treatment, quenching (sub-quenching, high-temperature quenching, and double quenching), and carburization as shown in FIGS.

  In special heat treatment, carbonitriding is performed by holding carbon nitride for a certain period of time at a temperature of 840 ° C in a mixed gas atmosphere of RX gas and ammonia gas, followed by primary quenching from that temperature and further tempering at a temperature of 230 ° C. I did it. Next, it was reheated to a temperature of 800 ° C. lower than the carbonitriding temperature, held at that temperature for a certain period of time, then subjected to secondary quenching, and further tempered at 230 ° C.

  In the carbonitriding process, the carbonitriding process was performed by holding at a temperature of 840 ° C. for a certain period of time, followed by quenching from that temperature and further tempering at a temperature of 230 ° C.

  In the carbonitriding process + quenching process, the carbonitriding process was performed by holding at a temperature of 840 ° C. for a certain period of time, followed by quenching from that temperature and further tempering at a temperature of 230 ° C. Subsequently, after reheating to 840 degreeC and hold | maintaining at that temperature for a fixed time, quenching was performed from the temperature and tempering was further performed at 230 degreeC.

  In the carburizing process, the carburizing process was performed at a temperature of 850 ° C. for a certain period of time, followed by quenching from that temperature and further tempering at a temperature of 230 ° C.

  In the sub-quenching treatment, after holding at a temperature of 850 ° C. for a certain time, quenching was performed from that temperature, and further tempering was performed at a temperature of 230 ° C.

  In the high-temperature quenching treatment, after holding at a temperature of 880 ° C. for a certain time, quenching was performed from that temperature, and tempering was further performed at a temperature of 230 ° C.

  In the twice-quenching treatment, after holding at a temperature of 840 ° C. for a certain time, the first quenching was performed from that temperature, and tempering was further performed at a temperature of 230 ° C. Next, after reheating to a temperature of 840 ° C. and holding at that temperature for a certain period of time, second quenching was performed from that temperature, and tempering was further performed at a temperature of 230 ° C.

  Table 1 shows the crystal grain number, the retained austenite amount, and the nitrogen content of the surface layer portion of the bearing ring subjected to each of these treatments.

  The crystal grain size was measured based on the JIS G 0551 steel austenite grain size test method. Moreover, the average value of 10 test samples created on the same conditions was calculated | required.

  The amount of retained austenite was measured at a depth of 0.05 mm below each surface at four positions on the raceway surface by X-ray diffraction. In addition, an average value of 10 test samples prepared under the same conditions (that is, an average value of 10 × 4 locations) was obtained.

  Further, the measurement of the nitrogen content in the surface layer portion of the race ring was performed by analysis using EPMA after cutting perpendicularly to the raceway surface. Moreover, the average value of the five test samples created on the same conditions was calculated | required.

  From the results of Table 1, in the sample samples of the bearing rings subjected to special heat treatment, a nitrogen-enriched layer was confirmed in the surface layer portion in any of SUJ2, SCM415M and S70C, and the austenite grain size number in the surface layer portion was No. 11. The amount of retained austenite was 5% by volume or more and 25% by volume or less, and the nitrogen content in the surface layer portion was 0.1% by mass or more and 0.7% by mass or less.

  On the other hand, in the sample sample of the bearing ring subjected to the heat treatment other than the special heat treatment, one or both of the austenite grain size number of 11 or more and the retained austenite amount of 5 to 25 vol% were not obtained.

  Next, a thrust needle roller bearing was prepared by combining each of the above raceway rings, and a life test of the thrust needle roller bearing was performed. Table 2 shows the test conditions of the life test, and Table 3 shows the test results of the life test.

  From the results in Table 3, the thrust needle roller bearing having a bearing ring that has been subjected to special heat treatment has an L10 life (sample) compared to a thrust needle roller bearing having a bearing ring that has been subjected to heat treatment other than special heat treatment. 90% of the thrust needle roller bearings that can be used can be used without breaking, and the service life is long. Further, it can be seen that even if the bearing rings are made of the same material, the L10 life can be further improved and the life can be extended by applying special heat treatment not only to the race rings but also to the rollers.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be advantageously applied to a thrust needle roller bearing for a car air conditioner / compressor and an automatic transmission.

It is a schematic sectional drawing which shows the structure of the thrust needle roller bearing in one embodiment of this invention. It is other embodiment of this invention, and is a schematic sectional drawing which shows the structure of the thrust needle roller bearing by which the roller is arrange | positioned at double rows. It is a figure explaining the heat processing method of the thrust needle roller bearing of this invention. It is a figure explaining the modification of the heat processing method of the thrust needle roller bearing of this invention. It is a figure which shows the microstructure of a bearing component, especially an austenite grain. (a) is a bearing part of the example of the present invention, and (b) is a conventional bearing part. FIG. 6A is a diagram illustrating an austenite grain boundary illustrating FIG. 5A, and FIG. 6B is a diagram illustrating an austenite grain boundary illustrating FIG. It is sectional drawing which shows roughly the structure of a swash plate type swash plate type compressor. It is sectional drawing which shows roughly the structure of a swash plate type swash plate type compressor. It is sectional drawing which shows schematically the structure of a variable displacement swash plate type compressor of a swash plate type. It is sectional drawing which shows schematically the structure of the torque converter part of an automatic transmission.

Explanation of symbols

  1 bearing ring, 1a through hole, 2, 2a, 2b needle roller, 3 cage, 3a, 3b annular member, 10A, 10B thrust needle roller bearing, 100 double swash plate compressor, 102 housing, 103 swash plate, 104 Main shaft, 105 Radial bearing, 106 Cylinder bore, 107 Piston, 108 Recessed portion, 109 Shoe, 200 Single swash plate compressor, 202 Housing, 203 Swash plate, 204 Main shaft, 207 Piston, 211 Connecting member, 215 Piston rod, 300 Variable capacity Swash plate compressor, 302 housing, 303 journal, 304 spindle, 307 piston, 312 piston support, 313 drive pin, 314 sleeve, 315 piston rod, 400 torque converter, 401 impeller, 401a Nperaburedo, 401b impeller hub, 402 stator, 403 turbines, 403a turbine blades, 403b turbine hub, 404 one-way clutch.

Claims (2)

  In a thrust needle roller bearing having a raceway ring and a needle roller made of a thin steel plate, at least the raceway has a nitrogen-enriched layer in a surface layer portion, and the amount of retained austenite in the surface layer portion is 5 volume% or more and 25 volumes. %, And the surface layer portion has an austenite grain size number of 11 or more.   2. The thrust needle roller bearing according to claim 1, wherein a nitrogen content of the surface layer portion is in a range of 0.1 mass% to 0.7 mass%.

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