JP2006200724A - Thrust bearing for automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thrust bearing for an automatic transmission which has superior durability and noise characteristics at low costs. <P>SOLUTION: The thrust bearing 10 is arranged between components 101, 102, and 103 of a torque converter 100 of the automatic transmission, and supports load transmitting to the components. The thrust bearing 10 has raceway disks 11 which are used without grinding raceway surfaces of the raceway disks after applying quenching hardening, and the raceway disks are selected from a group of raceway disks which has a 40 μm or less the value adding three times of standard deviation of bending and waviness of raceway disks to an average value when measuring the bending and waviness of the randomly sampled raceway disks among the group of a plurality of raceway disks. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a thrust bearing for an automatic transmission, and more specifically, in a thrust bearing washer manufactured by quench hardening, the automatic having a washer used without grinding after hardening and hardening.・ It relates to thrust bearings for transmissions.

  Generally, thrust bearings are required to have improved functions such as improved durability (longer life) and improved acoustic characteristics (lower noise). On the other hand, as one of the factors that reduce the function of the thrust bearing, there is warpage and undulation of the washer.

  For example, if the washer / waviness of the thrust roller bearing is large, when the bearing is operated, only a part of the rolling surface of the roller, which is a rolling element, is pressed against the washer (per piece). This one-piece contact can cause oil film breakage between the rolling element roller and the washer. When oil film breakage occurs, metal contact is made between the roller and the washer, and the temperature of that portion rises. As a result, surface damage or surface-origin type peeling occurs, which may shorten the life of the bearing. In addition, due to the occurrence of contact, there is a possibility that the contact surface pressure between the roller and the washer exceeds the value predicted by design in the portion where the contact has occurred. In this case, the internal starting type peeling may occur at an early stage and the life of the bearing may be shortened.

  In addition, when the warp or undulation of the washer of the thrust bearing is large, noise and vibration during operation of the bearing increase. This is a major problem for bearings used in environments where low noise is required.

  On the other hand, in the cooling process of quenching of the annular body corresponding to the raceway, a method has been proposed in which the annular body is subjected to predetermined processing while the structure of the annular body is in the austenite state (see, for example, Patent Document 1). Thereby, the distortion of the annular body after quenching is suppressed.

  In addition, a method has been proposed in which straightening and tempering is performed on a ring-shaped member corresponding to the raceway at a predetermined processing rate. Thereby, the dimensional accuracy of the ring-shaped member after completion of the heat treatment is improved (for example, see Patent Document 2).

Further, a method has been proposed in which a ring-shaped member after cold working is restrained with a mold and heated. As a result, the ring-shaped member is sized and the processing stress is removed. As a result, deformation of the ring-shaped member that occurs during the subsequent heat treatment is suppressed (for example, see Patent Document 3).
Japanese Patent Laid-Open No. 8-225851 Japanese Patent Laid-Open No. 9-256058 Japanese Patent Laid-Open No. 11-43717

  However, in recent years, products in which thrust bearings are used as parts, such as automatic transmissions, have become increasingly sophisticated. Along with this, the thrust bearings used therein are required to have higher functions and higher accuracy, such as longer life and lower noise. In view of the importance of the role played by the thrust bearing, strict standards are often required for the accuracy of the thrust bearing. Furthermore, there is a demand for cost reduction of thrust bearings in order to improve the price competitiveness of products.

  Under such circumstances, in the thrust bearing manufactured by the manufacturing method disclosed in Patent Documents 1 to 3 described above, the accuracy of the thrust bearing washer is not sufficient at the end of the heat treatment, and its durability is Not enough. In particular, large variations in warpage and undulation are a major obstacle in setting standards when strict standards are required as described above. Moreover, it cannot be said that the acoustic characteristics are sufficient if recent high demand characteristics are taken into consideration. Further, sufficient accuracy can be obtained if grinding is performed after the heat treatment is completed, but this increases the manufacturing cost and cannot meet the above-mentioned demand for cost reduction. Furthermore, improving accuracy by a method of adding a heat treatment step is contrary to the demand for cost reduction.

  In particular, a thrust bearing used for an automatic transmission may be used by adding an additive to the oil used in this portion from the viewpoint of energy saving. Additive-added oil is inferior to ordinary oil in lubrication performance.For this reason, oil film breakage occurs at the differential sliding between the roller and the rolling surface of the thrust bearing, resulting in metal contact and heating of the contact area. In some cases, surface damage (smearing) or surface-origin peeling tends to occur, resulting in a decrease in durability.

  In addition, thrust bearings for automatic transmissions are subject to high-speed rotation and frequent large acceleration / deceleration fluctuations (according to fluctuations in acceleration) in order to transmit engine power. Furthermore, in the above-mentioned thrust bearings, the stress in parts is constantly increasing due to the reduction in size, weight and load, and measures are taken not only for surface damage but also for load-dependent internal origin type damage suppression. It has been demanded. The occurrence of damage on the surface and inside of a thrust bearing for an automatic transmission subjected to such a large and frequent acceleration may be increased by an increase in variations in warpage and swell of the washer. As described above, it is considered important to suppress variations in warpage and swell of the washer in order to suppress noise for improving driving comfort.

  Accordingly, an object of the present invention is to stably provide a thrust bearing for an automatic transmission that is low in cost and excellent in durability and acoustic characteristics.

  A thrust bearing for an automatic transmission according to the present invention is a thrust bearing that is disposed between torque converter components of an automatic transmission and is loaded with a load transmitted between the components. This thrust bearing is equipped with a washer that was used without being hardened after hardening and hardening. When the washer was measured for warpage and undulation of the washer randomly extracted from a group of plural washer The value obtained by adding three times the standard deviation of warpage and swell to the average value of the washer was taken from the track washer group of 40 μm or less.

  As described above, an increase in warpage and undulation of the washer has an adverse effect on the life and acoustic characteristics of the thrust bearing. The inventor has studied in detail the relationship between warpage and undulation of the washer and the acoustic characteristics of the thrust bearing. As a result, the acoustic characteristics of thrust bearings do not deteriorate with a linear relationship as warpage / waviness of the washer increases, but there is a critical value for warpage / waviness, and if this is exceeded, the acoustic characteristics deteriorate rapidly. And this critical value was found to be 40-50 μm. Therefore, if the upper limit of warpage and undulation of the washer group can be set to 40 μm or less, an automatic transmission thrust bearing having excellent acoustic characteristics can be stably manufactured. Further, if the warpage and the undulation are reduced, the probability of occurrence of the phenomenon such as the one-piece contact described above can be lowered, so that the life of the thrust bearing can be extended (durability can be increased). That is, it is possible to stably manufacture a thrust bearing having excellent durability in addition to acoustic characteristics. By applying such a thrust bearing, the reliability and durability of the automatic transmission can be improved.

  In general, a value obtained by adding three times the standard deviation to the average value is a value that is treated as a practical upper limit value in statistical quality control. Assuming that the distribution of warp / waviness of the thrust bearing washer is normal, in the case of a washer group whose average value of warp / waviness of the washer plus three times the standard deviation is 40 μm or less. In addition, the washer with a warp / waviness value exceeding 40 μm is 0.13% of the entire washer group, and 40 μm can be considered as the practical upper limit. Therefore, according to the washer of the present invention, it is possible to constitute a thrust bearing with excellent acoustic characteristics by having a practical upper limit of warpage and undulation of the washer constituting the washer group being 40 μm. A stable washer can be obtained stably. Further, by reducing the warpage and undulation of the washer as described above, it is possible to obtain a washer that can constitute a thrust bearing with excellent durability.

  In addition, in order to stably obtain a washer group that can constitute a thrust bearing with further excellent acoustic characteristics, the warpage and undulation of each washer group constituting the randomly extracted washer group were measured. In this case, it is preferable that a value obtained by adding three times the standard deviation to the average value of warpage / waviness is 30 μm or less. Further, in this case, since the warpage and undulation of the washer become smaller, the durability of the thrust bearing using the washer can be further improved.

  A thrust bearing for an automatic transmission according to the present invention is a thrust bearing that is disposed between torque converter components of an automatic transmission and is loaded with a load transmitted between the components. This thrust bearing is equipped with a washer that was used without being hardened after hardening and hardening. When the washer was measured for warpage and undulation of the washer randomly extracted from a group of plural washer The probability of detecting a washer with a warp / waviness of 40 μm or more is taken from a washer group having a probability of 0.1% or less. In other words, when the warpage and undulation of 1000 randomly extracted bearings are measured, the number of bearings of 40 μm or more is 1 or less.

  As described above, if the practical upper limit of warpage and undulation can be set to 40 μm or less, an automatic transmission thrust bearing having excellent acoustic characteristics can be stably manufactured.

  Here, when measuring the warpage and undulation of each washer group that constitutes the randomly extracted washer group, the probability that a washer with a warp and undulation of 40 μm or more is 0.1% or less. For example, it can be considered that 40 μm is the practical upper limit for the warpage and swell of the washer. Therefore, according to the thrust bearing for an automatic transmission having a washer taken from the washer group of the present invention, the practical upper limit of warpage and undulation of the washer constituting the washer group is 40 μm. Excellent acoustic characteristics can be obtained stably. It is also possible to obtain a thrust bearing for an automatic transmission that is excellent in durability.

  A thrust bearing for an automatic transmission according to the present invention is a thrust bearing disposed between components of a torque converter of the automatic transmission and loaded with a load transmitted between the components. This thrust bearing is provided with a washer used without being subjected to grinding after hardening and hardening, and the washer was taken from the washer group, and the washer group was manufactured, particularly hardened. A washer group belonging to one lot of the process (processed in one quenching process), and when the warp / waviness of the washer of the washer group was measured, the washer / waviness was 40 μm or more. The probability of detecting is 0.1% or less.

  Thereby, the thrust bearing for automatic transmissions excellent in acoustic characteristics similarly to the above can be constituted. Further, if the warpage and undulation are reduced, the probability of occurrence of the phenomenon such as the one-sided contact described above can be lowered, so that it is possible to obtain a thrust bearing for an automatic transmission having excellent durability.

  In addition, the number of the washer constituting the washer group can be 100, but is preferably 500, and more preferably 1000.

  A thrust bearing for an automatic transmission according to the present invention is a thrust bearing that is disposed between torque converter components of an automatic transmission and is loaded with a load transmitted between the components. This thrust bearing is equipped with a washer that has been used without being ground after quench hardening, and a cross section perpendicular to the rolling surface of the washer is mirror-polished, and a surfactant is added to a saturated aqueous picric acid solution. After corroding the mirror-polished surface by immersion in a corrosive liquid, the area closed by the prior austenite grain boundary is 10% of the entire visual field when the central part of the cross section is observed at a magnification of 400 times with an optical microscope. % Or less. Here, the rolling surface of the washer means a surface on the side where the washer of the thrust bearing comes into contact with the rolling elements. The prior austenite grain boundaries are the grain boundaries formed when the steel structure of the washer is austenitized in the quenching process, and are preferentially corroded when the steel structure is corroded by a corrosive liquid. The boundary line that appears. Further, the measurement area for measuring the existence ratio of the area closed by the crystal grain boundary after corroding the mirror-polished surface as described above may be a square area of 225 μm × 175 μm in actual size. At this time, the region closed by the crystal grain boundary may be 10% or less, more preferably 5% or less of the entire measurement region.

  The present inventor examined the relationship between the prior austenite grain boundaries and the durability of the thrust bearing as follows.

In general, a thrust bearing washer is manufactured by quenching and hardening by carburizing heat treatment, bright heat treatment, and the like. In this case, the _washer is first heated to a temperature not _lower than the _Ac1 point, and the steel structure is austenitized to form a grain boundary. At this time, there are more lattice defects in the grain boundaries than in the grains. In addition, there are more impurity elements in the steel in the grain boundaries than in the grains. Thereafter, the washer is rapidly cooled to a temperature below the M _s point, and the steel structure becomes martensite. However, the part that was a grain boundary in the austenite state is a part that has different characteristics from the surrounding structure because it was an austenite grain boundary even after the structure was martensitic. Austenite grain boundaries). Since this prior austenite grain boundary is more easily corroded than the surrounding structure, its presence can be confirmed by corroding the structure after quenching.

  In this way, the prior austenite grain boundaries exist in the structure after quenching and have characteristics different from those of the surrounding structure, thus promoting the occurrence and propagation of cracks in the thrust bearing washer, and the durability of the thrust bearing. May be reduced.

  On the other hand, the present inventor did not sufficiently advance the formation of the prior austenite grain boundaries, specifically, mirror-polished the cross section perpendicular to the rolling surface of the washer, and added the surfactant to the saturated aqueous picric acid solution. When the central part of the cross section is observed with an optical microscope at a magnification of 400 times after corroding the mirror-polished surface by immersion in a corrosive solution to which 10 is added, the area closed by the crystal grain boundary is 10% of the entire visual field. % (Or by making the area closed at the crystal grain boundary 10% or less of the square measurement area of 225 μm × 175 μm in actual size) 10% or less. Has been found to be significantly improved. Therefore, according to the thrust bearing washer of the present invention, it is possible to provide a thrust bearing for an automatic transmission having excellent durability. In other words, the thrust bearing for an automatic transmission according to the present invention is excellent in use in an automatic transmission under severe conditions in terms of lubrication performance, differential slip, and frequency and size of acceleration / deceleration. Durability can be obtained.

  In addition, the durability of the thrust bearing for automatic transmission is clearly improved by setting the area closed by the grain boundaries to 10% or less of the entire field of view, but in order to further improve the durability, it is 5% or less. It is preferable to do.

  A thrust bearing for an automatic transmission according to the present invention is a thrust bearing that is disposed between torque converter components of an automatic transmission and is loaded with a load transmitted between the components. This thrust bearing is provided with a washer used without being subjected to grinding after hardening and hardening, and the thickness of the grain boundary oxide layer on the surface layer of the washer is 1 μm or less.

  The present inventor examined the relationship between the grain boundary oxide layer and the durability of the thrust bearing for automatic transmission as follows.

  As already described, the thrust bearing washer is generally manufactured by quenching and hardening by carburizing heat treatment, bright heat treatment, and the like. In this case, at the grain boundary of the surface layer portion of the washer, an alloy element such as Cr or Mn in the steel reacts with oxygen present in the atmospheric gas to form an oxide. Therefore, in the thickness direction of the washer disk, the amount of alloy elements in the steel in the layered part (hereinafter referred to as the grain boundary oxide layer in the surface layer part) from the outermost surface to the deepest part of the region where the oxide is formed Decreases. As a result, the grain boundary oxide layer on the surface layer of the washer is hard to be hardened by hardening, and the hardness after hardening may be reduced. Then, in a thrust bearing washer that is used without being subjected to grinding after quenching and hardening, the hardness (that is, the strength) of the surface layer portion is low, and damage starting from the surface layer portion is likely to occur. In addition, since the oxide formed in the grain boundary oxide layer has a significantly different hardness as compared with the surrounding steel structure, it may become a starting point of cracking. For the above reasons, a thrust bearing provided with a washer having a grain boundary oxide layer in the surface layer portion is likely to be damaged starting from the surface layer portion, and the durability (life) may be reduced. Further, surface damage is likely to occur due to the presence of the grain boundary oxide layer having low hardness.

  Here, in the thrust bearing washer that is used without grinding after quench hardening, the distance from the washer surface to the region where no grain boundary oxidation has occurred (that is, the thickness of the grain boundary oxide layer) Is usually about 2 μm to 10 μm. On the other hand, the present inventor has found that the durability of the thrust bearing is remarkably improved by making the thickness of the grain boundary oxide layer sufficiently small, specifically, by setting the thickness to 1 μm or less. Therefore, it is possible to provide a thrust bearing for an automatic transmission that is excellent in durability by using a washer having the above-described characteristics.

  Moreover, the deformation resistance of the surface layer portion can be improved by making the thickness of the surface grain boundary oxide layer very small as described above. For this reason, it acts in the direction which suppresses generation | occurrence | production of all the damages which the rolling surface of the said thrust bearing for automatic transmissions concerns, and can obtain the outstanding durability on the said severe conditions.

  Although the durability of the thrust bearing is clearly improved by setting the thickness of the grain boundary oxide layer to 1 μm or less, it is preferably 0.5 μm or less in order to further improve the durability.

  The torque converter includes an impeller coupled to an output shaft of the engine, a turbine coupled to the input shaft of the transmission and positioned so as to face the impeller, and a stator positioned between the impeller and the turbine. The thrust bearing for automatic transmission can be arranged between at least one of the impeller and the stator and between the turbine and the stator. With this configuration, the durability of the torque converter of the automatic transmission can be improved and noise can be suppressed.

  In the thrust bearing for an automatic transmission, the surface hardness of the washer is preferably 653 HV or more, and the internal hardness of the washer is 653 HV or more.

  When the surface hardness of the washer is lower than 653 HV, the rolling fatigue life of the thrust bearing is reduced. On the other hand, the fall of a rolling fatigue life can be avoided by making surface hardness into 653HV or more. Furthermore, by setting not only the surface but also the internal hardness to 653 HV or more, it is less likely to cause plastic deformation in the washer than the washer having only 653 HV or more on the surface, and more rolling fatigue of thrust bearings for automatic transmission The service life is improved. Here, the surface hardness refers to the hardness of the portion (rolling portion of the rolling surface) that contacts the roller on the surface of the washer. Further, the internal hardness refers to the hardness of the central portion of the cross section perpendicular to the surface in contact with the roller in the washer.

  In the above thrust bearing for automatic transmission, preferably, the material of the washer is steel containing 0.4 mass% or more and 1.2 mass% or less of carbon.

The upper limit of the hardness when quenching and hardening steel depends on the carbon content of the steel. In order to secure the above-mentioned hardness of 653 HV or more, the amount of carbon needs to be at least 0.4 mass%. On the other hand, when the amount of carbon increases, austenite (residual austenite) that remains without being martensite after quenching increases. If the amount of retained austenite is small, the effect is small, but if the amount of carbon is 1.2 mass% or more, the amount of retained austenite increases and the quenching hardness decreases. Residual austenite becomes martensite due to aging and causes dimensional changes. Furthermore, when the carbon content is 1.2% by mass or more, carbides (Fe ₃ C; cementite) are coarsened and agglomerated, and the toughness of the bearing disc is significantly deteriorated. Therefore, the hardness, dimensional stability, and toughness required for the washer constituting the automatic transmission thrust bearing with excellent durability by setting the carbon content to 0.4 mass% or more and 1.2 mass% or less. Can be secured.

  In the above thrust bearing for an automatic transmission, the washer is preferably configured using a member obtained by pressing a steel plate.

  Thereby, it can be set as a low cost washer compared with what uses the member shape | molded by methods, such as turning. As a result, the cost of the automatic transmission thrust bearing can be reduced.

  As is apparent from the above description, according to the present invention, there is provided a thrust bearing for an automatic transmission that has low durability and excellent durability and acoustic characteristics under severe lubrication environment and stress application conditions. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. Thrust bearings refer to thrust bearings for automatic transmissions.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a thrust bearing according to a first embodiment which is an embodiment of the present invention. FIG. 2 is a schematic plan view showing a measurement site of warpage and undulation of the washer of the thrust bearing of the first embodiment. FIG. 3 is a diagram showing an example of a profile obtained by measuring warpage / waviness. With reference to FIGS. 1-3, the structure of the thrust bearing of Embodiment 1 of this invention is demonstrated.

  Referring to FIG. 1A, the thrust bearing 10 includes, for example, a pair of washer disks 11, 11, a plurality of rolling elements 12, and an annular cage 13. The rolling element 12 is disposed between the pair of washer disks 11 and 11 in contact with the rolling surfaces 11A and 11A of the washer disks 11 and 11. Further, the rolling elements 12 are arranged at a predetermined pitch in the circumferential direction by the cage 13 and are held so as to be freely rollable. Thereby, each of the washer disks 11 and 11 can rotate relative to each other.

  Referring to FIG. 2, the measurement of warpage / waviness is performed at a position 1 mm from the inner diameter, a position 1 mm from the outer diameter, and a position at the center as indicated by a broken line. With reference to FIG. 3, the difference between the highest point and the lowest point of the height is read from the height profile obtained by the measurement, and the values are taken as the values of warpage and swell. When warpage and undulation are measured for a plurality of washer disks (bearing disk group) provided in the thrust bearing 10 of the first embodiment obtained by this measuring method, the average value of these values is three times the standard deviation. The value to which is added is 40 μm or less.

  Further, in the above-described thrust bearing washer 11 according to the present invention, almost no prior austenite grain boundaries can be observed in the center of the cross section perpendicular to the rolling surface 11A of the washer 11. This is presumably because the formation of prior austenite grain boundaries is not sufficiently advanced. The area closed by the prior austenite grain boundaries in this field of view is 10% or less of the entire field of view observed. Further, when a measurement area of 225 μm × 175 μm in actual size is set at the center of the visual field, the ratio of the area closed by the prior austenite grain boundary in the measurement area is 10% or less of the entire area. On the other hand, in a conventional thrust bearing washer, a clear prior austenite grain boundary can be observed at the center of the cross section perpendicular to the rolling surface 11A. This is considered to be because the formation of prior austenite grain boundaries is sufficiently advanced. The area closed by the prior austenite grain boundaries in this field of view is 90% or more of the entire field of view.

  Here, the observation of the prior austenite grain boundary at the center of the cross section perpendicular to the rolling surface 11A of the washer 11 can be performed, for example, by the following procedure. First, the washer disk 11 of the thrust bearing 10 is cut along a plane perpendicular to the rolling surface 11A. Next, the cross section is mirror-polished, and the polished surface is immersed in a corrosive solution at room temperature for 30 minutes to corrode. As the corrosive solution, a solution obtained by adding a surfactant to a picric acid saturated aqueous solution (JIS G 0551 Annex 1) was used. Thereafter, the central part of the cross section is observed with an optical microscope at a magnification of 400 times.

  The region closed by the prior austenite grain boundary in the center of the cross section perpendicular to the rolling surface of the washer disk 11 of the thrust bearing 10 according to the first embodiment observed by this observation method is 10% or less of the entire visual field. It is.

  In the washer disk 11 of the thrust bearing 10 according to the first embodiment, the thickness of the grain boundary oxide layer in the surface layer portion is 1 μm or less. On the other hand, in the conventional thrust bearing washer, the thickness of the grain boundary oxide layer in the surface layer is about 6 μm. Here, the observation of the grain boundary oxide layer in the surface layer portion of the washer 11 can be performed, for example, by the following procedure. First, the washer disk 11 of the thrust bearing 10 is cut along a plane perpendicular to the rolling surface 11A. Next, the cross-section is mirror-polished, and the polished surface is corroded by being immersed in 3% nital at room temperature. The immersion time is, for example, about 2 seconds to 10 seconds, but since the susceptibility to corrosion varies depending on the steel type, it can be set to an appropriate time for each washer while confirming the progress of corrosion. Then, the surface layer part just under a rolling surface is observed with an optical microscope. As described above, the thickness of the grain boundary oxide layer in the surface layer portion of the washer of the thrust bearing according to the first embodiment observed by this observation method was 1 μm or less.

  Next, a method for manufacturing the washer 11 and the thrust bearing 10 according to the first embodiment will be described.

  FIG. 4 is a diagram showing an example of a manufacturing process of the washer 11 in the first embodiment. With reference to FIG. 4, an example of the manufacturing process of the washer 11 of the first embodiment will be described.

  First, as a material for the washer 11 in the first embodiment, for example, S55C, SAE1070, SK5, SUJ2 can be selected. All of these materials are steel containing carbon of 0.4 mass% or more and 1.2 mass% or less. For example, the washer 11 is formed by press working using steel plates of these materials. Thereby, the washer disk 11 is configured using a member obtained by pressing and forming a steel plate. Next, quenching and tempering by induction heating are performed in a state in which the washer 11 is restrained in order to suppress warpage and undulation in the washer 11. As a result, the heating time in the quenching process is very short compared to carburizing heat treatment, bright heat treatment, etc., which are general quench hardening treatments, so the formation of prior austenite grain boundaries does not proceed sufficiently, and grain boundary oxidation Little layers are formed. Further, since the washer is restrained in the quenching and tempering process, warpage and undulation are suppressed. Furthermore, the surface hardness and internal hardness of the washer 11 are both 653 HV or higher. Next, finishing is performed by, for example, a tumbler without performing grinding.

  In addition, according to such a process, since induction heating equipment is comparatively small-scale and does not use carburizing gas etc. which should be handled with care, one line is formed together with the processing process (one line is made). be able to. Therefore, work in process before and after heat treatment does not occur. Thereby, the manufacturing cost can be reduced. Further, since product management becomes easy, quality control of piece-by-piece can be performed. As a result, the quality of the product is improved.

  Further, in a normal process, a warp / waviness is large at the end of tempering of the washer, and therefore, a press temper process for correction is often provided. On the other hand, in this process, since the restraint for suppressing warpage and undulation of the washer is performed in the quenching and tempering process, the warp and undulation of the washer 11 is small at the end of tempering. Therefore, the press temper process is not required, and the high precision washer 11 can be manufactured at low cost.

  Next, quenching and tempering in the heat treatment method for the washer 11 in the first embodiment will be described in detail.

  FIG. 5 is a diagram showing an example of a heat treatment apparatus used in the manufacturing process of the washer 11 in the first embodiment. With reference to FIG. 5, an example of a heat treatment method for washer 11 in Embodiment 1 will be described in detail.

  Referring to FIG. 5, induction heat treatment apparatus 3 includes induction coil 30, lower restraining jig 50 </ b> A, upper restraining jig 50 </ b> B, center shaft 51, and jig presser nut 53. The induction coil 30 has a cooling water discharge port 31 for discharging cooling water. The central shaft 51 has a bulging portion 511 at the lower end and a threaded portion 512 at the top. The jig presser nut 53 has a thread groove on the inner diameter side.

  Hereinafter, the heat treatment procedure will be described with reference to FIG.

  A central shaft 51 is inserted into the lower restraining jig 50A. The lower restraining jig 50A is disposed so as to contact the bulging portion 511 at the lower end of the central axis. A center shaft 51 is inserted into the washer disk 11 of the thrust bearing having a hole in the center. The washer 11 is disposed so as to contact the smooth upper surface of the lower restraining jig 50A. Although one washer disk 11 may be used, it is preferable to use a plurality of washer disks from the viewpoint of improving the efficiency of heat treatment. When heat treatment is performed on a plurality of sheets at the same time, the washer 11 is stacked in a range that can be heated by the induction coils 30 disposed on both sides of the central axis 51. The upper restraining jig 50 </ b> B is disposed such that the smooth lower surface thereof is in contact with the upper portion of the washer disk 11. The central shaft 51 is inserted into the upper restraining jig 50B. The jig presser nut 53 is fitted into the center shaft 51 so that the thread groove on the inner diameter side engages with the threaded portion 512 of the center shaft 51, and is tightened with a predetermined torque. As a result, the washer 11 is loaded with stress in the direction of pressing the rolling surface 11A on the entire rolling portion.

When a high-frequency current is passed through the induction coil 30, the washer 11 is induction-heated (heating process). The _washer 11 is heated to a temperature not _lower than the _Ac1 point and held for a predetermined time. Thereafter, energization is stopped and cooling water is sprayed onto the washer 11 through the cooling water discharge port 31 of the induction coil 30. Thereby, the washer 11 is rapidly cooled to a temperature below the M _s point (cooling step). According to the above procedure, the bearing disc 11 is hardened and hardened in a state where a stress in a direction to press the rolling surface is applied. At this time, in order to perform heating and cooling uniformly, a part other than the induction coil 30 in the induction heat treatment apparatus 3 is rotated relative to the induction coil 30 with the central axis 51 as a rotation axis as indicated by arrows. Is preferred.

The _Ac1 point means a point corresponding to a temperature at which the steel starts to transform from ferrite to austenite when the steel is continuously heated. Further, the M _s point means a point corresponding to a temperature at which martensite formation starts when the austenitized steel is cooled. Further, the rolling surface of the washer means a surface on the side where the rolling elements roll in the washer. Moreover, the rolling part of a bearing disc means the part where a rolling element rolls among rolling surfaces.

Furthermore, the induction coil 30 is again energized with a high-frequency current, and the washer 11 is heated to a temperature below the _Ac1 point. After that, the washer 11 is held at a predetermined temperature for a predetermined time, and then cooled by stopping heating (tempering step). According to the above procedure, the washer 11 is tempered in a state where a stress in a direction to press the rolling surface is applied. At this time, in order to perform heating uniformly, it is preferable to rotate the portion other than the induction coil 30 in the induction heat treatment apparatus 3 relative to the induction coil 30 with the central axis 51 as a rotation axis as indicated by an arrow. .

  Through the above steps, the prior austenite grain boundaries are not sufficiently formed, and the grain boundary oxide layer is hardly formed, and the washer 11 has at least a stress in a direction to press the rolling surface 11A. It is quenched and tempered while being loaded on the entire rolling part.

  The stress does not necessarily need to be continuously applied and can be released as necessary. From the viewpoint of suppressing deformation and reducing the number of processes, the washer 11 is restrained before the heat treatment is started, and the heat treatment is performed. It is desirable to continue restraint until the end. In addition, although the washer 11 can be heat-treated one by one, in order to further reduce the manufacturing cost of the washer 11, it is desirable to simultaneously carry out heat treatment of a plurality of washer.

  According to this heat treatment method, the formation of the prior austenite grain boundaries of the washer 11 can not be sufficiently advanced. Moreover, the thickness of the grain boundary oxide layer in the surface layer portion of the washer disk 11 can be 1 μm or less. Further, warpage / waviness of the washer 11 is suppressed, and the value obtained by adding three times the standard deviation to the average value of the warp / waviness of the washer group consisting of a plurality of washer 11 at the end of the heat treatment is 40 μm or less. can do.

  By the above heat treatment method, the value obtained by adding 3 times the standard deviation to the average value of the warp / waviness is 40 μm or less, and the surface hardness and internal hardness of the washer 11 are 653 HV or more. 11 is mirror-polished on a cross section perpendicular to the rolling surface 11A, and the polished surface is immersed in a corrosive solution in which a surfactant is added to a saturated aqueous solution of picric acid to be corroded. When the central portion is observed, the area closed by the prior austenite grain boundaries is 10% or less of the entire field of view, and is the washer 11 of the thrust bearing 10 that is used without being ground after quench hardening. The thickness of the grain boundary oxide layer in the surface layer portion is 1 μm or less, and the material of the washer disk 11 is steel containing carbon of 0.4 mass% or more and 1.2 mass% or less. By pressing a steel plate A thrust bearing washer 11 constituted by using the obtained member can be manufactured. Moreover, by using this washer 11, the thrust bearing 10 provided with the washer 11 having the above-described configuration can be manufactured.

  In FIG. 1 (a), the rolling elements 12 are arranged in a single row, but may be arranged in a double row as shown in (b) to (e). Further, the shape of the cage 13 is not limited to the shape shown in FIG. 1A, and may be, for example, the shapes shown in FIGS. 1B to 1E. Further, in FIGS. 1A to 1C, the cage 13 is made of metal, but the material of the cage 13 is not limited to metal, for example, as shown in FIGS. 1D and 1E. Thus, the material may be a resin. Moreover, when it has the double-row rolling element 12, in FIG.1 (b)-FIG.1 (d), although the rolling element adjacent to radial direction is hold | maintained in the single holding | maintenance area | region provided in the holder | retainer. As shown in FIG. 1E, the holding regions may be separated, and the respective rolling elements 12 may be held in the plurality of holding regions.

  In the above-described thrust bearing heat treatment method, the case where the heat treatment is performed using the induction heat treatment apparatus 3 shown in FIG. 5 has been described. However, another heat treatment method obtained by modifying the heat treatment method can be selected.

  FIG. 6 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process of the washer 11 in the first embodiment. With reference to FIG. 6, the heat processing using the induction heat processing apparatus of the 1st modification is demonstrated.

  Referring to FIG. 6, induction heat treatment apparatus 3 in the first modification and induction heat treatment apparatus 3 in FIG. 5 described above have basically the same configuration. However, the induction heat treatment apparatus 3 of the first modified example does not have the central shaft 51 and the jig presser nut 53 that meshes with the central shaft 51, while the induction coil 30 is arranged on the inner diameter side of the washer 11. This is different from the induction heat treatment apparatus 3 of FIG.

  Hereinafter, the heat treatment procedure will be described with reference to FIG.

  The heat treatment procedure is basically the same as in FIG. However, unlike the case of FIG. 5, the upper restraining jig 50 </ b> B is not clamped by the jig pressing nut 53 and pressed against the washer 11, but pressure is applied by other means (for example, a hydraulic cylinder or the like). The Thereby, the stress of the direction which presses a rolling surface is loaded with respect to the whole rolling part of the washer 11 at least. Further, the heating for quenching and tempering is performed not only from the outer diameter side of the washer 11 but also from the inner diameter side.

  According to the first modification, the washer 11 is heated more uniformly than in the first embodiment. Therefore, it is advantageous for suppressing warpage and swell.

  FIG. 7 is a schematic sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process of the washer 11 in the first embodiment. With reference to FIG. 7, the heat processing using the induction heat processing apparatus of the 2nd modification is demonstrated.

  Referring to FIG. 7, induction heat treatment apparatus 3 in the second modification example and induction heat treatment apparatus 3 in FIG. 5 described above basically have the same configuration. However, the induction heat treatment apparatus 3 of the second modification example is different from the induction coil 30 in that the induction coil 30A for quenching and the induction coil 30B for tempering are arranged on both sides of the central axis 51, respectively, as shown in FIG. Different from the induction heat treatment apparatus 3 of FIG. The induction coil 30A for quenching is a second induction coil 30A1 that is adjacent to the first induction coil 30A1 for quenching and is disposed between the induction coil 30B for tempering. It consists of a quenching induction coil 30A2. The second quenching induction coil 30 </ b> A <b> 2 has a cooling water discharge port 31. Further, in the induction heat treatment apparatus 3 of FIG. 5, all the arranged washer plates 11 are configured to be heated at the same time, whereas in the second modified example, only a part of the washer plate 11 is configured to be capable of being heated. ing. Specifically, the height of the induction coils 30 </ b> A and 30 </ b> B is smaller than the height of the set plurality of washer disks 11 so that only the end surfaces of some of the washer disks 11 can be opposed. Furthermore, in the second modification, one or both of the induction coils 30A and 30B and the central axis 51 can move in the axial direction of the central axis 51, so that the central axis 51 is relative to the induction coils 30A and 30B. It is configured to be movable.

  Hereinafter, the heat treatment procedure will be described with reference to FIG.

  The lower restraining jig 50A, the upper restraining jig 50B, the washer 11 and the jig holding nut 53 are arranged in the same manner as in FIG. 5, and the stress in the direction to press the rolling surface of the washer 11 is at least The entire rolling part of the washer 11 is loaded.

Next, high frequency current is applied to the induction coils 30A and 30B, and the central shaft 51 moves relative to the induction coils 30A and 30B. Along with this, the washer 11 reaches a position between the energized first quenching induction coil 30A1. As a result, the _washer 11 is induction-heated to a temperature not _lower than the _Ac1 point. The heated washer 11 moves relative to the first quenching induction coil 30A1 and reaches a position sandwiched between the second quenching induction coils 30A2, and during the predetermined time A _c1. The temperature is kept above the point. Thereafter, heating of the washer 11 by the second quenching induction coil 30A2 is stopped, and cooling water is sprayed from the cooling water discharge port 31 to the washer 11 and rapidly cooled to a temperature below the M _s point. Is done. By the above procedure, quenching is performed in a state where stress in a direction to press the rolling surface 11A is applied to the washer disk 11. The heating time in this quenching process is very short compared to carburizing heat treatment, bright heat treatment, etc., which are general quench hardening processes, so the formation of prior austenite grain boundaries does not proceed sufficiently, and the grain boundary oxide layer is Little formed.

Furthermore, the washer 11 moves relative to the induction coils 30A and 30B and reaches a position sandwiched between the tempering induction coils 30B. Thereby, the washer 11 is heated to a predetermined tempering temperature below the _Ac1 point. The heated washer 11 moves relative to the tempering induction coil 30 </ b> B, and is air-cooled by leaving the heating range after a predetermined time. Thereby, tempering is implemented in the state which applied the stress of the direction which presses a rolling surface to the washer disk 11. FIG.

  Through the above-described steps, the washer 11 is quenched and tempered while stress in the direction of pressing the rolling surface is applied to at least the entire rolling part of the washer.

  According to the second modification, the washer 11 can be heat-treated even if the washer 11 is stacked beyond the length of the induction coils 30A and 30B.

(Embodiment 2)
The thrust bearing 10 according to the second embodiment and the thrust bearing 10 described with reference to FIGS. 1 to 3 in the first embodiment basically have the same configuration. However, in the first embodiment, the value obtained by adding three times the standard deviation to the average value of the warp / waviness of the washer group including the washer 11 provided in the thrust bearing 10 was 40 μm or less. In the second embodiment, when measuring the warpage / waviness of each of the randomly extracted washer disks 11 constituting the washer group, the probability of detecting the washer disk 11 having a warp / waviness of 40 μm or more is 0.1. % Or less.

  The warp / waviness of the washer 11 may be measured by the method described in the first embodiment based on FIG. 2 and FIG. 3 as described above. However, in the second embodiment, other measurement methods are used. It can also be done.

  FIG. 8 is a perspective view showing a modified example of the method for measuring the warpage / waviness of the washer applicable to the second embodiment. With reference to FIG. 8, the sorting instrument and the sorting method used in the modified example of the method for measuring warpage / waviness will be described.

Referring to FIG. 8, the slit gauge 20 has a slit 21 having a width T ₁ + d. Here, T ₁ is the thickness of the washer 11. Further, d is an upper limit value of warpage / swell.

  When the washer 11 is inserted into the slit 21, it can pass through if the warp / waviness of the washer 11 is not more than d, but cannot pass through if it exceeds d. Here, by setting d = 40 μm, it is possible to select the washer 11 having warpage / swell of 40 μm or more. As a result, when the washer group consisting of the washer 11 of the second embodiment is selected, the probability that a washer having a warp / waviness of 40 μm or more is 0.1% or less.

  The heat treatment method of the present embodiment is the same as the method described with reference to FIGS. 4 and 5 in the first embodiment, and the heat treatment method of the first modification or the second modification may be selected. it can.

(Embodiment 3)
FIG. 9 is a schematic partial sectional view showing an example of the configuration around the rolling elements of the thrust bearing according to the third embodiment of the present invention. With reference to FIG. 9, an example of a structure around the rolling elements of the thrust bearing of the present invention will be described.

  In the first embodiment and the second embodiment described above, the thrust bearing 10 includes a pair of washer disks 11, 11, a plurality of rolling elements 12, and an annular cage 13. The case where it has a flat shape has been described. In the third embodiment, referring to FIG. 9A, the thrust bearing 10 is implemented in that it includes, for example, a pair of washer disks 11, 11, a rolling element 12, and a cage 13. This is the same as Embodiment 1 and Embodiment 2. However, one washer 11 has an inner diameter flange 111 extending in the direction intersecting the rolling surface 11A on the radially inner side, and the other washer 11 intersecting the rolling surface 11A on the radially outer diameter side. It is different in that it has an outer diameter flange 113 extending in the direction of the movement. Further, an inner diameter flange projecting portion 112 projecting toward the radially outer diameter side is formed at the distal end portion of the inner diameter flange 111, and an outer diameter flange projecting portion projecting toward the radially inner diameter side is formed at the distal end portion of the outer diameter flange 113. Another difference is that 114 is formed. Therefore, due to the action of the inner diameter flange protrusion 112 and the outer diameter flange protrusion 114, the raceway disk 11, the retainer 13, and the rolling element 12 held by the retainer 13 are not separated.

  In addition, although FIG. 9A demonstrated the case where the trackway 11 was a pair, the trackway 11 may be one as shown in FIGS. 9G to 9K. 9A illustrates the case where the washer 11 has the flanges 111 and 113. However, one or both of the flanges 111 have the flange 111 as shown in FIGS. 9C to 9F and FIG. 9K. , 113 may be omitted. 9A illustrates the case where the flanges 111 and 113 of the washer 11 have the protruding portions 112 and 114. However, one or both of the protruding portions 112 and 114 are protruding portions as shown in FIGS. 9B to 9K. It may be one without 112 and 114. In this case, the bearing disc 11 that does not have the protruding portions 112 and 114 and the retainer 13 and the rolling element 12 held by the retainer 13 are separable.

  The heat treatment method is basically the same as that in the first and second embodiments, but as described above, the washer disk 11 may have the flanges 111 and 113 in some cases. In this case, it is necessary to select another method for the heat treatment method of the thrust bearing 10 in the first and second embodiments. Hereinafter, an embodiment of the present invention when the washer 11 has flanges 111 and 113 will be described with reference to the drawings.

  FIG. 10 is a diagram showing an example of a heat treatment apparatus used in the manufacturing process of the washer 11 in the third embodiment. With reference to FIG. 10, an example of the heat processing method of the washer 11 in Embodiment 3 will be described in detail.

  Referring to FIG. 10, induction heat treatment apparatus 3 in the third embodiment and induction heat treatment apparatus 3 in the first embodiment shown in FIG. 5 have basically the same configuration. However, the washer disk 11 to be heat-treated in the third embodiment has an inner diameter flange 111. Therefore, for example, when two washer 11 are heat-treated, first, the first washer 11 rolls so that the entire rolling portion of the rolling surface 11A is in contact with the smooth upper surface of the lower restraining jig 50A. It is arranged with the surface 11A facing downward. Next, the second washer 11 is arranged above the first washer 11 with the rolling surface 11A facing upward. Further, an upper restraining jig 50B is disposed on the upper portion thereof so that the smooth lower surface thereof is in contact with the entire rolling portion of the rolling surface 11A. As a result, as in FIG. 5, the washer 11 is loaded with stress in the direction of pressing the rolling surface 11 </ b> A in the entire rolling portion of the washer 11.

  Next, the induction coil 30 is energized with a high-frequency current, and the subsequent heat treatment is performed in the same manner as in the first embodiment shown in FIG. In this way, the washer 11 having the inner diameter flange 111 is quenched and tempered while being loaded with stress in the direction of pressing the rolling surface 11A on at least the entire rolling part of the washer. In addition, since the heating time in this quenching process is extremely short compared to carburizing heat treatment and bright heat treatment, which are general quench hardening processes, the formation of prior austenite grain boundaries does not proceed sufficiently, and grain boundary oxidation Little layers are formed.

  FIG. 11 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process of washer 11 in the third embodiment. With reference to FIG. 11, the heat processing using the induction heat processing apparatus of the 1st modification is demonstrated.

  Referring to FIG. 11, induction heat treatment apparatus 3 in the first modification of the third embodiment and induction heat treatment apparatus 3 in the third embodiment shown in FIG. 10 have basically the same configuration. is doing. However, FIG. 10 has a central axis 51 as in FIG. 5 and has a configuration in which stress is applied to the washer 11 with the restraining jig 50 and the jig holding nut 53. In FIG. Similarly, the difference is that the induction coil 30 is arranged on the inner diameter side of the washer disk 11.

  Next, the heat treatment procedure of this modification will be described. First, as in the case of FIG. 10, the lower restraining jig 50A, the washer 11, and the upper restraining jig 50B are arranged. Then, without using the jig presser nut 53, pressure is applied to the upper restraining jig 50B in the same manner as in FIG. Next, the induction coil 30 is energized with a high-frequency current, and the subsequent heat treatment is performed in the same manner as in the first embodiment shown in FIG. In this way, the washer 11 having the inner diameter flange 111 is quenched and tempered while being loaded with stress in the direction of pressing the rolling surface 11A on at least the entire rolling part of the washer.

  FIG. 12 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process of washer 11 in the third embodiment. FIG. 13 is a schematic sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process of the washer 11 in the third embodiment. With reference to FIG. 12 and FIG. 13, the heat processing using the induction heat processing apparatus of the 2nd and 3rd modification is demonstrated.

  Referring to FIGS. 12 and 13, induction heat treatment apparatus 3 in the second and third modifications, and induction heat treatment apparatus in the third embodiment and the first modification shown in FIGS. 10 and 11 described above 3 has basically the same configuration. However, in FIG. 10 and FIG. 11, the washer 11 has an inner diameter flange 111, but in FIG. 12 and FIG. 13, the washer 11 is different in that it has an outer diameter flange 113. In this case, as shown in FIG. 12 and FIG. 13, if the washer 11 is restrained in a state where the outer diameter flange 113 is protruded radially outward of the restraining jigs 50A and 50B, the above-described FIG. 10 and FIG. As in the case, quenching and tempering can be performed while the washer 11 is restrained.

  Further, the method for measuring warpage and undulation is basically the same as that in the first and second embodiments, but the washer 11 may have the flanges 111 and 113 as described above. In this case, when the sorting method for the washer 11 described in the second embodiment with reference to FIG. 8 is used, it is necessary to partially modify the sorting method.

  FIG. 14 is a perspective view showing a method for selecting warpage / swell of the washer 11 when the washer 11 has an inner diameter flange 111. FIG. 15 is a perspective view showing a method of selecting warpage / swell of the washer 11 when the washer 11 has an outer diameter flange 113.

Referring to FIGS. 14 and 15, the slit gauge 20 has basically the same configuration as that of FIG. However, the difference is that the width of the slit 21 is T ₁ + T ₂ + d. Another difference is that the measuring jig 22 is used for sorting. Here, the measuring jig 22 has a cylindrical shape whose both bottom surfaces are parallel planes, and has a thickness T ₂ larger than the height of the flanges 111 and 113.

  The bottom surface of the measuring jig 22 and the rolling surface 11A of the washer 11 are aligned with each other and inserted into the slit 21. Then, if the warp / waviness of the washer 11 is d or less, it can pass through, but if it exceeds d, it cannot pass through. Here, by setting d = 40 μm, it is possible to select the washer 11 having warpage / swell of 40 μm or more. As a result, when the washer group composed of the washer 11 of the third embodiment is selected, the probability that a washer having warpage / swell of 40 μm or more is 0.1% or less.

(Embodiment 4)
When the washer 11 of the thrust bearing 10 has the inner diameter flange 111 or the outer diameter flange 113, another method is selected as the heat treatment method for the washer 11 in place of the method described in the first to third embodiments. You can also

  FIG. 16 is a diagram showing an example of an induction heat treatment apparatus used in the manufacturing process of the washer 11 in the fourth embodiment. With reference to FIG. 16, an example of the heat processing method of the washer 11 in Embodiment 4 is demonstrated in detail.

  Referring to FIG. 16, induction heat treatment apparatus 3 in the fourth embodiment and induction heat treatment apparatus 3 in FIG. 5 described above basically have the same configuration. However, in the fourth embodiment, the washer 11 has an inner diameter flange 111. 16 is different from the induction heat treatment apparatus 1 shown in FIG. 5 in that the induction heat treatment apparatus 3 shown in FIG. The intermediate portion restraining jig 50C has, for example, an inner diameter larger than the inner diameter of the washer 11, and further has a cylindrical shape whose upper and lower surfaces are parallel and smooth.

  Next, a heat treatment procedure will be described with reference to FIG.

  The first washer 11 is placed in contact with the lower restraining jig 50A and with the rolling surface 11A facing upward. The intermediate portion restraining jig 50 </ b> C is arranged so as to overlap therewith so that the smooth lower surface is in contact with at least the entire rolling portion of the rolling surface 11 </ b> A of the washer 11. Next, the second washer 11 is overlaid on the intermediate portion restraining jig 50C, and at least the entire rolling portion of the rolling surface 11A of the washer 11 is the smooth upper surface of the intermediate portion restraining jig 50C. It arrange | positions so that it may touch. A combination of the intermediate portion restraining jig 50C and the two washer disks 11 and 11 is used as a unit, and a plurality of these are stacked in a range where the induction coil 30 can be heated. An upper restraining jig 50B is disposed on the upper part, and is fastened by a jig presser nut 53 as in the case of FIG. As a result, the washer 11 is loaded with stress in the direction of pressing the rolling surface 11A on the entire rolling portion. In this state, the washer 11 is quenched and tempered while stress applied in the direction of pressing the rolling surface is applied to at least the entire rolling part of the washer as in the case of FIG. In addition, since the heating time in this quenching process is extremely short compared to carburizing heat treatment and bright heat treatment, which are general quench hardening processes, the formation of prior austenite grain boundaries does not proceed sufficiently, and grain boundary oxidation Little layers are formed.

  FIG. 17 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process of washer 11 in the fourth embodiment. FIG. 18 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process of washer 11 in the fourth embodiment. With reference to FIG. 17 and FIG. 18, the heat processing using the induction heat processing apparatus of the 1st and 2nd modification is demonstrated.

  Although the case where the center shaft 51 and the jig holding nut 53 are used has been described with reference to FIG. 16, the center shaft 51 and the jig holding nut 53 are attached to the center shaft 51 and the jig holding nut 53 as in the case of FIG. Instead, a configuration in which the induction coil 30 is disposed on the inner diameter side of the washer 11 may be used. Further, as in the induction heat treatment apparatus 3 shown in FIG. 18, a configuration in which the central shaft 51 is movable relative to the induction coils 30A and 30B may be used as in the case of FIG. In this case, the washer 11 is restrained in the same manner as in FIG. 16, and the subsequent heat treatment procedure is the same as in FIGS.

  FIG. 19 is a schematic cross-sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process of washer 11 in the fourth embodiment. FIG. 20 is a schematic cross-sectional view showing a fourth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 21 is a schematic cross-sectional view showing a fifth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. With reference to FIGS. 19-21, the heat processing using the induction heat processing apparatus of the 3rd, 4th, and 5th modification is demonstrated.

  Referring to FIGS. 19 to 21, the induction heat treatment apparatus 3 in the third, fourth, and fifth modifications shown in FIGS. 19 to 21 and the above-described embodiment shown in FIGS. The form 4 and the induction heat treatment apparatus 3 of the first and second modifications have basically the same configuration. However, in FIG. 16 to FIG. 18, the washer 11 has an inner diameter flange 111, whereas in FIGS. 19 to 21, the washer 11 has an outer diameter flange 113. In this case, if the washer 11 is restrained in a state where the outer diameter flange 113 is protruded radially outward of the intermediate portion restraining jig 50C as shown in FIGS. In the same manner as described above, quenching and tempering can be performed while the washer 11 is restrained.

(Embodiment 5)
By combining the washer disk 11 having the inner diameter flange 111 or the outer diameter flange 113 and the washer disk 11 not having the inner diameter flange 111 and the outer diameter flange 113, another method for the heat treatment of the washer disk 11 is selected. You can also

  FIG. 22 is a diagram showing an example of an induction heat treatment apparatus used in the manufacturing process of the washer 11 in the fifth embodiment. FIG. 23 is a partially enlarged view showing an area XXIII in FIG. 22 in an enlarged manner. With reference to FIG. 22 and FIG. 23, an example of the heat processing method of the washer 11 in Embodiment 5 is demonstrated in detail.

  Referring to FIGS. 22 and 23, induction heat treatment apparatus 3 in the present embodiment and induction heat treatment apparatus 3 in FIG. 16 described above have basically the same configuration. However, the induction heat treatment apparatus 3 according to the fifth embodiment differs from the induction heat treatment apparatus 3 of FIG. 16 in that a bearing washer 11 having no flanges 111 and 113 is used instead of the intermediate portion restraining jig 50C. Yes.

  Next, a heat treatment procedure will be described with reference to FIG.

  The first washer 11 having the inner diameter flange 111 contacts the lower restraining jig 50A and is disposed with the rolling surface 11A facing upward. The washer 11 that does not have the flanges 111 and 113 is disposed so as to overlap with at least the entire rolling portion of the rolling surface 11A of the washer 11 having the inner diameter flange 111. Next, the second washer 11 having the inner diameter flange 111 is overlapped on the washer 11 not having the flanges 111 and 113, and at least the rolling surface 11A of the washer 11 having the inner diameter flange 111 is rolled. It arrange | positions so that the whole part may contact the washer disk 11 which does not have the flange 111,113. A plurality of washer disks 11 that do not have the flanges 111 and 113 may be arranged so that such an arrangement is possible. A plurality of these combinations of the washer disks 11 are stacked within a range in which the induction coil 30 can be heated with the combination of the washer disks 11 as one unit. Thereafter, in the same manner as in the case of FIG. 16, quenching and tempering are performed while stress in a direction in which the rolling surface 11 </ b> A is pressed is applied to at least the entire rolling portion of the washer 11. In addition, since the heating time in this quenching process is extremely short compared to carburizing heat treatment and bright heat treatment, which are general quench hardening processes, the formation of prior austenite grain boundaries does not proceed sufficiently, and grain boundary oxidation Little layers are formed.

  FIG. 24 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 25 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. With reference to FIG. 24 and FIG. 25, the heat processing using the induction heat processing apparatus of the 1st and 2nd modification is demonstrated.

  Although the case where the central shaft 51 and the jig holding nut 53 are used has been described with reference to FIG. 22, the central shaft 51 and the jig holding nut 53 are attached to the central shaft 51 and the jig holding nut 53 as in the case of FIG. Instead, a configuration in which the induction coil 30 is disposed on the inner diameter side of the washer 11 may be used. Further, as in the induction heat treatment apparatus 3 shown in FIG. 25, a configuration in which the central shaft 51 is movable relative to the induction coils 30A and 30B may be used as in the case of FIG. In this case, the washer 11 is restrained in the same manner as in FIGS. 22 and 23, and the subsequent heat treatment procedure is the same as in FIGS. 6 and 7.

  FIG. 26 is a schematic cross-sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 27 is a partially enlarged view showing an area XXVII in FIG. 26 in an enlarged manner. FIG. 28 is a schematic cross-sectional view showing a fourth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 29 is a schematic cross-sectional view showing a fifth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. With reference to FIGS. 26 to 29, heat treatment using the induction heat treatment apparatuses of the third, fourth, and fifth modifications will be described.

  26 to 29, the induction heat treatment apparatus 3 in the third, fourth, and fifth modifications shown in FIGS. 26 to 29 and the embodiment shown in FIGS. 22 to 25 described above. The fifth embodiment and the induction heat treatment apparatus 3 of the first and second modifications have basically the same configuration. However, in FIG. 22 to FIG. 25, the washer 11 has an inner diameter flange 111, whereas in FIGS. 26 to 29, the washer 11 has an outer diameter flange 113. In this case, as shown in FIGS. 26 to 29, if the washer 11 is constrained with the flange 113 protruding outward in the radial direction of the washer 11 without the flanges 111 and 113 as shown in FIGS. Quenching and tempering can be performed in a state in which the washer 11 is restrained in the same manner as the above-described method described with reference to FIGS.

(Embodiment 6)
FIG. 30 is a schematic sectional view showing the arrangement of thrust bearings of an automatic transmission (automatic transmission) according to Embodiment 6 of the present invention. An automatic transmission usually includes a torque converter 100 and a planetary gear mechanism (not shown).

  The torque converter 100 mainly includes an impeller 101, a stator 102, and a turbine 103. The thrust bearing for automatic transmission according to the present embodiment is, for example, a thrust bearing 10 assembled between the impeller 101 and the stator 102 and between the stator 102 and the turbine 103.

  In this torque converter 100, an impeller 101 connected to the output shaft of the engine and a turbine 103 connected to the input shaft of the transmission are arranged to face each other. The stator 102 is attached to a stator shaft fixed to the casing via a one-way clutch 104. The stator 102 changes the flow direction of fluid when returning the fluid flowing back between the impeller blade 101a and the turbine blade 103a formed in a bowl shape from the turbine 103 side to the impeller 101 side on the inner diameter side thereof. In other words, a forward rotational force is applied to the impeller 101 to amplify the transmission torque.

  The thrust bearing 10 between the impeller 101 and the stator 102 includes a roller 62, a cage 13, and a raceway disk 11 as an example of a rolling element. One raceway plate 11 is assembled to the impeller hub 101b, and the other raceway plate 11 is assembled to the stator 102 side.

  The thrust bearing 10 between the stator 102 and the turbine 103 includes a roller 62, a cage 13, and a raceway 11. One washer 11 is assembled to the turbine hub 103b, and the other washer 11 is assembled to the stator 102 side.

  In each of the thrust bearings 10 assembled between the impeller 101 and the stator 102 and between the stator 102 and the turbine 103, a single row roller 62 is used.

Both of the above thrust bearings are similar to the thrust bearing shown in FIG. That is, the rolling elements are shown in a single row, but may be in a double row and correspond to one of the following thrust bearings.
(1) It is equipped with a washer that was used without grinding after quenching and hardening, and the above washer is an average when measuring warpage and undulation of the washer randomly extracted from a group of plural washer The value obtained by adding three times the standard deviation of warpage / waviness to the value was taken from a track washer group of 40 μm or less.
(2) A bearing washer that has been used without being ground after quench hardening, and that washer is warped when measuring the warpage and undulation of the washer randomly extracted from a group of multiple washer. -It was taken from a group of track disks having a probability of detecting a track disk having a swell of 40 μm or more of 0.1% or less.
(3) A corrosive solution comprising a washer that has been used without being ground after quench hardening, a cross section perpendicular to the rolling surface of the washer is mirror-polished, and a surfactant is added to a picric acid saturated aqueous solution. When the central portion of the cross section is observed with an optical microscope at a magnification of 400 times after corroding the mirror-polished surface by immersion, the region closed by the crystal grain boundary is 10% or less of the entire field of view. .
(4) A washer used without grinding after quenching and hardening is provided, and the thickness of the grain boundary oxide layer in the surface layer portion of the washer is 1 μm or less.
(5) Further, the surface hardness of the above washer is 653 HV or more, and the internal hardness of the washer is 653 HV or more.
(6) Further, the material of the above washer is steel containing 0.4 mass% or more and 1.2 mass% or less of carbon.
(7) Further, the above-described bearing disc is configured by using a member obtained by pressing and forming a steel plate.

  FIG. 31 is an enlarged view showing a thrust bearing disposed between the stator 102 and the turbine 103. Between the rolling surface 11A of the stator-side washer 11 and the rolling surface 11A of the turbine-side washer 11 (or between the rolling surface of the impeller-side washer and the rolling surface of the stator-side washer. ) So that the roller 62 rolls. When the washer 11 is rotated, the retainer 13 is also rotated together with the washer 11, and the roller 62 rolls between the rolling surfaces 11A of the two washer 11 facing each other. Here, lubricating oil is supplied into the thrust bearing 10 from a hydraulic supply source (not shown) via an oil passage.

  Lubricating oil is supplied from the radially inner peripheral side of the thrust bearing 10 as indicated by an arrow b, for example, and then passes around the roller 62 and the space formed by the cage 13 as indicated by an arrow c. Lubricating between the side surface of 62 and the roller holding portion of the cage 13, between the end surfaces of the roller 62, and between the side surface of the roller 62 and the rolling surface 11A, the roller holding portion of the rolling surface 11A and the cage 13 is lubricated. However, it is discharged as shown by an arrow d through the space between the outer portions in the radial direction.

  As described above, in an automatic transmission, an additive may be mixed in the lubricating oil, and the lubricating performance may be deteriorated. When the respective parts are lubricated with the lubricating oil, the rolling surface 11A of the washer is likely to be damaged. In addition, thrust bearings used in automatic transmission torque converters receive high-speed rotation and frequent large acceleration / deceleration fluctuations (according to fluctuations in acceleration increase / decrease) in order to transmit power from the engine to the wheels. Increased sensitivity to surface damage.

  Regardless of the lubrication performance of the oil, the above surface damage susceptibility increases the warpage and waviness of the washer, causing oil film breakage in the differential sliding between the roller of the thrust bearing and the rolling surface, resulting in metal contact and contact parts. Generates heat and promotes surface damage (smearing) and surface-origin peeling. By using the washer in any one of the above (1) to (7), the damage at the contact portion between the roller and the rolling surface is greatly reduced, and the durability can be improved.

  Embodiment 1 of the present invention will be described below.

  Of the contact portion between the rolling contact surface of the rolling bearing and the rolling element, plastic deformation may occur and remain at the maximum load portion. With respect to this residual deformation amount, if the sum of the deformation amount of the rolling element and the deformation amount of the rolling surface is 0.01% or less of the diameter of the rolling element, there is an adverse effect on the smooth rotation and fatigue life of the bearing. It is empirically known not to.

  Therefore, an experiment was conducted to measure the allowable static rolling element load between the thrust roller bearing of the present invention and the conventional thrust roller bearing and to compare the safety factor.

The experimental procedure will be described below. S55C, SAE1070, SK5, and SUJ2 were selected as materials for the experiment. A disk-shaped washer having an inner diameter of 25 mm, an outer diameter of 40 mm, and a thickness of 1 mm was produced by pressing. The heat treatment apparatus shown in FIG. 5 was used for the heat treatment. 40 wasting stacks were constrained and stressed in a direction to press the rolling surface was applied to at least the entire rolling part of the washer. Then, a high-frequency current (10 KHz) was applied to the induction coil, and the entire _washer was heated to a temperature of the _Ac1 point or higher by induction heating. After a predetermined time, heating was stopped and water was sprayed to cool the washer to a temperature below the M _s point. Further, while maintaining the constrained state of the washer, it was held at 220 ° C. to 230 ° C. for 10 seconds by induction heating, and was tempered by air cooling by stopping the heating (Examples A to D described later). Moreover, the other part stopped restraint and tempered by hold | maintaining at 160 degreeC for 2 hours in an atmospheric furnace (after-mentioned Example EH).

  On the other hand, as an example of a conventional thrust roller bearing, SPC, SCM415, SCM420, and SUJ2 were selected as materials (Comparative Examples A to D described later). The washer was produced by pressing as in this example. The washer of SPC, SCM415, and SCM420 was carburized by holding at 880 ° C. for 40 minutes in a carburizing furnace, then holding and holding at 820 ° C. for 10 minutes, and then quenching by oil cooling. Further, the SUJ2 washer was quenched by oil cooling after being held at 850 ° C. for 40 minutes in a bright heat treatment furnace. Then, tempering was performed by holding the washer at 160 ° C. for 2 hours. Furthermore, the process which reduces curvature and a wave | undulation was performed by the press temper (heating correction) for 1 hour at 200 degreeC.

  Warpage / waviness, surface hardness, and internal hardness of the washer after the heat treatment were measured. Warpage and undulation were measured by the method described in Embodiment 1 based on FIGS. 2 and 3 using a roundness measuring device. The surface hardness and internal hardness were measured using a Vickers hardness meter (load 1 kgf (9.8 N)). In addition, the surface hardness measured the hardness of the part (rolling part of a rolling surface) which contacts a roller in the surface of a bearing disc. Further, the internal hardness was measured by measuring the hardness of the central portion of the cross section perpendicular to the surface in contact with the roller in the washer.

  Table 1 shows the measurement results of warpage, waviness and hardness of the produced washer. Referring to Table 1, the value obtained by adding three times the standard deviation of warpage / waviness to the average value of warpage / waviness of the washer of Examples A to H was 40 μm or less. Further, there was no one washer with warp / swell of 40 μm or more, and the probability that a washer with warp / swell of 40 μm or more was detected was 0.1% or less. Furthermore, both surface hardness and internal hardness were 653HV or more.

  On the other hand, the value obtained by adding three times the standard deviation of warpage / waviness to the average value of warpage / waviness of the washer of Comparative Examples A to D was a value exceeding 40 μm. In addition, there was no one washer with a warp / swell of less than 40 μm, and the probability that a washer with a warp / swell of 40 μm or more was detected was 100%.

  The above experimental results are for a disk-shaped washer with an inner diameter of φ25 mm, an outer diameter of φ40 mm, and a thickness of 1 mm, but the same experiment was performed for a disk-shaped washer with an inner diameter of φ60 mm, an outer diameter of φ85 mm and a thickness of 1 mm. Also went. As a result, the maximum value of warpage and waviness of the washer produced by the heat treatment method according to the manufacturing method of the present invention is 28 μm, and so on, and the disk-like washer having the inner diameter φ25 mm, the outer diameter φ40 mm, and the thickness 1 mm. It was confirmed that the same effect as the case was obtained.

Next, thrust roller bearings were produced using the washer disks of Examples A to H and Comparative Examples A to D. Then, using an Amsler tester, a load was applied to the produced bearing to measure a load that generates a total permanent deformation amount of 0.01% of the diameter of the rolling element. From this measurement result, the safety factor was calculated. Here, the safety factor is expressed by Equation 1.
S ₀ = C ₀ / P _0max (1)
S ₀ : Safety factor, C ₀ : Basic static load rating, P _0max : Maximum static rolling element load Note that the lower the safety factor, the better the bearing characteristics.

  Table 2 shows the results of this experiment. Referring to Table 2, Examples A to H according to the present invention have smaller safety factor values than Comparative Examples A to C. This is because the washer of Comparative Examples A to C is hardened only in the surface layer portion, whereas the washer of Examples A to H of the present invention is uniformly hardened to the inside. This is probably because plastic deformation hardly occurs and the allowable static rolling element load increases.

  On the other hand, Comparative Example D and Examples D and H are made of the same material, and both are hardened to the inside of the washer. However, Examples D and H have smaller safety factor values than Comparative Example D. This is thought to be due to the following reasons.

As described above, in Examples D and H, the heating during quenching is performed by induction heating. Therefore, as compared with Comparative Example D in which the bright heat treatment is performed, the time for heating to a temperature higher than the _Ac1 point is very short. As a result, in Examples D and H, the formation of austenite grain boundaries is not progressing as much as in Comparative Example D. Therefore, it is considered that the deformation resistances of Examples D and H are higher than the deformation resistance of Comparative Example D, the allowable static rolling element load is improved, and the safety factor is lowered.

  In Comparative Example D, a low-hardness grain boundary oxide layer is formed on the surface layer portion of the washer by the bright heat treatment performed as the quenching process, whereas in Examples D and H, the quenching process takes a short time. The grain boundary oxide layer is hardly formed because of induction heating. Therefore, the washer of Examples D and H has higher deformation resistance at the surface layer than the washer of Comparative Example D. As a result, it is considered that the allowable static rolling element load in Examples D and H is higher than the allowable static rolling element load in Comparative Example D, and the value of the safety factor is low.

  FIG. 32 is an optical micrograph of the austenite grain boundaries of Example D (a) and Comparative Example D (b) of the present invention, taken during the observation. FIG. 32 (a) shows a washer made of SUJ2 which is an embodiment of the present invention (Example D), and FIG. 32 (b) shows a conventional washer made of SUJ2 (Comparative Example D). . FIG. 33 is a schematic diagram of the austenite grain boundaries of Example D (a) and Comparative Example D (b). The prior austenite grain boundaries were observed by the following procedure. First, the washer was cut along a plane perpendicular to the rolling surface. Next, the cross section was mirror-polished, and the polished surface was immersed in a corrosive solution at room temperature for 30 minutes to corrode. As the corrosive solution, a solution obtained by adding a surfactant to a saturated aqueous solution of picric acid was used. Thereafter, the central part of the cross section was observed with an optical microscope at a magnification of 400 times. In addition, observation was performed about five visual fields by changing a place in the center part of a cross section.

Referring to FIG. 32 (a), in Example D, the prior austenite grain boundaries could hardly be observed. This is considered to indicate that the formation of prior austenite grain boundaries is not sufficiently advanced as shown in FIG. The area closed by the prior austenite grain boundaries in this field of view was 10% or less of the entire field of view. The same was true for the other four fields of view. Further, in Examples A to C and E to H, the area closed by the prior austenite grain boundaries in the entire visual field was 10% or less of the entire visual field. This is considered to be because in Examples A to H, the heating at the time of quenching is performed by induction heating, and the time for heating to a temperature not _lower than the _Ac1 point is very short. On the other hand, with reference to FIG. 32B, in Comparative Example D, a clear prior austenite grain boundary could be observed. This is considered to indicate that the formation of prior austenite grain boundaries is sufficiently advanced as shown in FIG. The area closed by the prior austenite grain boundaries in this field of view was 90% or more of the entire field of view. The same was true for the other four fields of view. Further, in Comparative Examples A to C as well, the area closed by the prior austenite grain boundaries in the entire visual field was 90% or more of the entire visual field.

  FIG. 34 is an optical micrograph of the vicinity of the surface layer of the washer of Example D (a) and Comparative Example D (b) of the present invention. Observation near the surface layer of the washer was performed according to the following procedure. First, the washer was cut along a plane perpendicular to the rolling surface. Next, the cross-section was mirror-polished, and the polished surface was then corroded by being immersed in 3% nital at room temperature. The immersion time is, for example, about 2 seconds to 10 seconds, but since the susceptibility to corrosion differs depending on the steel type, the time was set to be appropriate for each washer while confirming the progress of corrosion. Then, the surface layer part just under a rolling surface was observed with the optical microscope.

Referring to FIG. 34A, in Example D, the grain boundary oxide layer is hardly observed, and it is confirmed that the thickness of the grain boundary oxide layer is 1 μm or less. In other Examples A to C and E to H, the thickness of the grain boundary oxide layer was similarly 1 μm or less. This is considered to be because in Examples A to H, the heating at the time of quenching is performed by induction heating, and the time for heating to a temperature not _lower than the _Ac1 point is very short. On the other hand, referring to FIG. 34B, it is confirmed that in Comparative Example D, a grain boundary oxide layer of about 6 μm was formed. In other Comparative Examples A to C, a grain boundary oxide layer of about 4 μm to 7 μm was formed.

  Embodiment 2 of the present invention will be described below.

  An experiment was conducted to compare the lifespan of the thrust roller bearing of the present invention and a conventional thrust roller bearing.

  The experimental procedure will be described below. For the thrust roller bearings of Examples A to H and Comparative Examples A to D produced in Example 1, a thrust load of 4 kN and a rotational speed of 5000 r / min. The life test was conducted under the condition of lubricating oil VG2.

  Table 3 shows the results of the life test. The test results are shown as a life ratio with the life of Comparative Example A as 1.

  With reference to Table 3, the lifetimes of Examples A to H were twice or more that of Comparative Examples A to D. This is considered to be due to the following reasons.

  As described above, the warpage and waviness of the washer of Examples A to H are smaller than those of Comparative Examples A to D. Therefore, no contact between the roller and the washer occurs. As a result, it is considered that the oil film was not cut and the local surface pressure did not increase, resulting in a long life. Further, as shown in Table 1, the warpage and waviness of the washer of Examples A to H are all 40 μm or less, while the warp and waviness of the washer of Comparative Examples A to D are all 50 μm or more. . That is, the warpage and undulation of the washer of Examples A to H is 40 μm or less, and as described above, the allowable static rolling element load of Examples A to H is higher than that of the comparative example, and the life of the bearing is long. It is thought that it became.

  In addition, as described above, in Examples A to H, the formation of austenite grain boundaries does not progress as much as Comparative Examples A to D. Therefore, the resistance to the occurrence and development of cracks is increasing. As a result, the generation and propagation of cracks originating from the surface due to roller sliding are suppressed. In addition, the generation and propagation of cracks are similarly suppressed with respect to cracks originating from the inside. It is considered that the life was prolonged due to the effect of suppressing the generation and propagation of such cracks.

  In Comparative Examples A to D, a grain boundary oxide layer is formed on the surface layer of the washer by carburizing treatment or bright heat treatment performed as a quenching step, whereas in Examples A to H, the quenching step is short. The grain boundary oxide layer is hardly formed because of induction heating. For this reason, it is considered that the occurrence of cracks at the surface starting point was suppressed and the life was prolonged.

  From the above, it can be seen that the thrust bearing of the present invention has a longer life compared to the conventional thrust bearing.

  Embodiment 3 of the present invention will be described below.

  An experiment was conducted to compare the acoustic characteristics of the thrust roller bearing of the present invention and a conventional thrust roller bearing. The experimental procedure will be described below.

  Thrust roller bearings were produced using the washer disks of Examples A to H and Comparative Examples A to D produced in Example 1. For this bearing, a thrust load of 100 N and a rotational speed of 1800 r / min. As for other conditions, a test for measuring the noise level of the bearing was conducted in accordance with Japanese Industrial Standard (JIS B 1548).

  FIG. 35 is a diagram showing the relationship between warpage and undulation of the washer of the thrust roller bearing and sound. In addition, the acoustic value in the range of each warp / swell in FIG. 35 is obtained by performing an acoustic measurement on each of the ten bearings and showing an average value thereof.

  Referring to FIG. 35, the acoustic value does not gradually increase with the increase in warpage and undulation, but it is about 79 to 81 dBA at 40 μm or less, but increases at around 40 to 50 μm, and is almost above that It is 84 dBA or more. From this, it is considered that there is a critical value in the vicinity where the value of warpage and undulation of the washer is 40 to 50 μm. Therefore, it can be seen that for thrust roller bearings used for applications in which acoustic characteristics are important, it is important to reliably suppress warpage and undulation to 40 μm or less.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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 thrust bearing for an automatic transmission according to the present invention includes a thrust bearing washer manufactured by quench hardening and can be particularly advantageously applied to an automatic transmission to which a large acceleration is frequently applied.

1 is a schematic cross-sectional view showing a thrust bearing according to a first embodiment. FIG. 3 is a schematic plan view showing a measurement site of warpage and undulation of the washer of the thrust bearing of the first embodiment. It is a figure which shows an example of the profile obtained by the measurement of curvature and a wave | undulation. 6 is a diagram showing an example of a manufacturing process of the washer 11 in the first embodiment. FIG. FIG. 3 is a diagram showing an example of an induction heat treatment apparatus used in the manufacturing process of the washer 11 in the first embodiment. FIG. 6 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the first embodiment. FIG. 7 is a schematic sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process of the washer 11 in the first embodiment. FIG. 10 is a perspective view showing a modified example of the method for measuring the warpage and waviness of the washer applicable to the second embodiment. 6 is a schematic partial cross-sectional view showing an example of a configuration around a rolling element of a thrust bearing according to Embodiment 3. FIG. FIG. 10 is a diagram showing an example of an induction heat treatment apparatus used in the manufacturing process of the washer 11 in the third embodiment. FIG. 11 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the third embodiment. FIG. 11 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the third embodiment. FIG. 10 is a schematic cross-sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the third embodiment. FIG. 6 is a perspective view showing a method for selecting warpage and undulation of the washer 11 when the washer 11 has an inner diameter flange 111. FIG. 6 is a perspective view showing a method for selecting warpage / swell of the washer 11 when the washer 11 has an outer diameter flange 113. FIG. 10 is a diagram showing an example of an induction heat treatment apparatus used in a manufacturing process of a washer 11 in a fourth embodiment. FIG. 12 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 10 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 10 is a schematic cross-sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 12 is a schematic cross-sectional view showing a fourth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 10 is a schematic cross-sectional view showing a fifth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fourth embodiment. FIG. 10 is a diagram showing an example of an induction heat treatment apparatus used in the manufacturing process of the washer 11 in the fifth embodiment. It is the elements on larger scale which expanded and showed the part of area | region XXIII of FIG. FIG. 10 is a schematic cross-sectional view showing a first modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 10 is a schematic cross-sectional view showing a second modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 10 is a schematic cross-sectional view showing a third modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. It is the elements on larger scale which expanded and showed the part of area | region XXVII of FIG. FIG. 12 is a schematic cross-sectional view showing a fourth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. FIG. 12 is a schematic cross-sectional view showing a fifth modification of the induction heat treatment apparatus used in the manufacturing process for washer 11 in the fifth embodiment. It is a figure which shows the arrangement | positioning location of the thrust bearing for automatic transmissions concerning Embodiment 6 of this invention. It is an enlarged view which shows the thrust bearing arrange | positioned between a stator and a turbine. It is an optical microscope photograph of the austenite grain boundary of Example D (a) and Comparative Example D (b). It is a schematic diagram of the austenite grain boundary of Example D (a) and Comparative Example D (b). It is an optical microscope photograph of the surface layer vicinity of the washer of Example D (a) and Comparative Example D (b) of the present invention. It is the figure which showed the relationship between the curvature and the wave | undulation of the washer of a thrust roller bearing, and a sound.

Explanation of symbols

  10 thrust bearing, 11 thrust bearing washer, 11A rolling surface, 111 washer inner diameter flange, 112 washer inner flange protrusion, 113 washer outer diameter flange, 114 washer outer flange protrusion, 12 Rolling element, 13 Cage, 20 Slit gauge, 21 Slit, 22 Measuring jig, 3 Induction heat treatment device, 30 Induction coil, 30A1 First induction coil, 30A2 Second induction coil, 30B Tempering induction coil, 31 Cooling water discharge port, 50A Upper restraint jig, 50B Lower restraint jig, 50C Middle restraint jig, 51 Center axis, 511 Center axis bulging part, 512 Center axis screw part , 53 Jig presser nut, 62 rollers, 100 Torque converter, 101 impeller, 101a impeller blade, 101b impeller Hub, 102 stator, 103 turbines, 103a turbine blades, 104 one-way clutch.

Claims (8)

A thrust bearing disposed between components of a torque converter of an automatic transmission and loaded with a load transmitted between said components;
It has a washer that was used without hardening after quench hardening.
The above-mentioned washer is a track whose value obtained by adding three times the standard deviation of the warp / waviness to the average value when the warp / waviness of the washer randomly selected from a group of washer is measured is 40 μm or less. Thrust bearings for automatic transmissions taken from the group of boards. A thrust bearing disposed between components of a torque converter of an automatic transmission and loaded with a load transmitted between said components;
It has a washer that was used without hardening after quench hardening.
The probability of detecting a washer having a warp / waviness of 40 μm or more is 0.1% or less when measuring the warp / waviness of a washer randomly extracted from a group of a plurality of washer. Thrust bearings for automatic transmissions, taken from the bearing group. A thrust bearing disposed between components of a torque converter of an automatic transmission and loaded with a load transmitted between said components;
It has a washer that was used without hardening after quench hardening.
The cross section perpendicular to the rolling surface of the bearing disc is mirror-polished, immersed in a corrosive solution obtained by adding a surfactant to a picric acid saturated aqueous solution to corrode the mirror-polished surface, and then magnified 400 times with an optical microscope. When the central part of the cross section is observed, the area closed by the prior austenite grain boundaries is 10% or less of the entire field of view. A thrust bearing disposed between components of a torque converter of an automatic transmission and loaded with a load transmitted between said components;
It has a washer that was used without hardening after quench hardening.
A thrust bearing for an automatic transmission, wherein a thickness of a grain boundary oxide layer in a surface layer portion of the washer is 1 μm or less.   The torque converter includes an impeller coupled to an output shaft of an engine, a turbine coupled to an input shaft of a transmission and positioned so as to face the impeller, and a stator positioned between the impeller and the turbine. 5. The automatic transmission thrust bearing according to claim 1, wherein the automatic transmission thrust bearing is disposed between at least one of the impeller and the stator and between the turbine and the stator.・ Thrust bearing for transmission.   The thrust bearing for an automatic transmission according to any one of claims 1 to 5, wherein a surface hardness of the washer is 653 HV or more, and an internal hardness of the washer is 653 HV or more.   The thrust bearing for an automatic transmission according to any one of claims 1 to 6, wherein a material of the bearing disc is steel containing 0.4 wt% or more and 1.2 wt% or less of carbon.   The thrust bearing for an automatic transmission according to any one of claims 1 to 7, wherein the bearing disc is configured by using a member obtained by pressing and forming a steel plate.