JP2019039561A - Rolling bearings, rolling bearings for automotive electrical equipment, and rolling bearings for speed reducers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing capable of suppressing generation of hydrogen embrittlement due to infiltration of hydrogen from the surface. A rolling bearing according to an embodiment includes an inner ring, an outer ring, and rolling elements arranged between the inner ring and the outer ring. The inner ring, the outer ring and the rolling elements are made of steel. A quench hardened layer is provided on at least one of the raceways of the inner and outer rings and the rolling surfaces of the rolling elements. The hydrogen diffusion coefficient in the quench-hardened layer is smaller than 2.6×10 −11 m 2 /s. [Selection diagram] Fig. 5

Description

  The present invention relates to a rolling bearing, a rolling bearing for automotive electrical accessory, and a rolling bearing for an speed reducer.

  When a rolling bearing is used under conditions where water is mixed, slipping or energized, water or lubricant decomposes (hereinafter, this reaction is referred to as a hydrogen generation reaction). Hydrogen is generated. The generated hydrogen enters the inside of the rolling bearing from the surface. Hydrogen in steel causes hydrogen embrittlement.

  Conventionally, a rolling bearing described in Japanese Patent Application Laid-Open No. 2000-282178 (Patent Document 1) and a rolling bearing described in Japanese Patent No. 4434685 (Patent Document 2) are known.

  In the rolling bearing described in Patent Document 1, a large amount of chromium (Cr) is added to the steel constituting the rolling bearing. This Cr forms a passive film on the surface of the rolling bearing. This passive film suppresses hydrogen from entering the inside of the rolling bearing from the surface.

  In the rolling bearing described in Patent Document 2, an oxide film is formed on the surface of the rolling bearing. This oxide film suppresses the occurrence of a hydrogen generation reaction on the surface of the rolling bearing.

JP 2000-282178 A Japanese Patent No. 4434685

  However, in the rolling bearing described in Patent Document 1, carbide is easily coarsened by adding a large amount of Cr. The coarsened carbide may become a stress concentration source.

  When the rolling bearing described in Patent Document 2 is used in a harsh environment, the oxide film easily peels off. On the new surface from which the oxide film has been peeled off, a hydrogen generation reaction may occur. Therefore, when the rolling bearing described in Patent Document 2 is used under a harsh environment, it is difficult to suppress the entry of hydrogen.

  The present invention has been made in view of the above-mentioned problems of the prior art. More specifically, this invention provides the rolling bearing which can suppress generation | occurrence | production of hydrogen embrittlement accompanying hydrogen infiltrating from the surface.

A rolling bearing according to an aspect of the present invention includes an inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring. The inner ring, outer ring and rolling elements are made of steel. A quench hardening layer is provided on at least one of the raceway surfaces of the inner ring and the outer ring and the rolling surface of the rolling element. The hydrogen diffusion coefficient in the quench hardened layer is less than 2.6 × 10 ⁻¹¹ m ² / s.

  In the above-described rolling bearing, the hardened hardened layer may contain nitrogen. In this case, the life of the rolling bearing is improved by increasing the hardness of the surface of the hardened hardened layer. In the rolling bearing described above, the nitrogen concentration in the hardened hardening layer may be 0.05 weight percent or more and 0.6 weight percent or less. If the nitrogen concentration in the hardened layer becomes too high, a large amount of Cr nitride is formed in the hardened layer, and the Cr concentration in the steel decreases. As a result, the hardenability of the hardened hardened layer decreases. Therefore, in this case, the hardenability of the hardened hardened layer can be ensured.

  In the rolling bearing described above, the volume ratio of the austenite phase in the hardened hardened layer may be 10 percent or more and 40 percent or less. The austenite phase has a smaller hydrogen diffusion coefficient than the martensite phase. Therefore, the larger the volume ratio of the austenite phase in the hardened layer, the lower the hydrogen diffusion coefficient of the hardened layer. On the other hand, the austenite phase in the hardened hardened layer may transform into a martensite phase while using a rolling bearing. Therefore, if the volume ratio of the austenite phase in the quench hardened layer is too large, the dimensional stability is lowered. Therefore, in this case, the hydrogen diffusion coefficient can be reduced while maintaining dimensional stability.

  In the above rolling bearing, the hardness of the hardened hardened layer may be 58 HRC or more and 64 HRC or less. Since the raceway surface and the rolling surface are required not to be deformed even when subjected to contact stress, the hardened hardened layer provided on the raceway surface or the rolling surface is required to have hardness. On the other hand, when the hardness of the quench-hardened layer is excessively high, the toughness decreases. Therefore, in this case, deformation of the raceway surface or the rolling surface due to application of contact stress can be suppressed while ensuring the toughness of the raceway surface or the rolling surface.

  In the above rolling bearing, the steel may be a high carbon chromium bearing steel. This high carbon chrome bearing steel may be SUJ2 or SUJ3.

The rolling bearing for an automotive electrical accessory according to one aspect of the present invention supports a shaft that is driven to rotate relative to a stationary member. A rolling bearing for an automotive electrical accessory includes an inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring. The inner ring, outer ring and rolling elements are made of steel. A quench hardening layer is provided on at least one of the raceways of the inner ring and the outer ring and the rolling surface of the rolling element, and the hydrogen diffusion coefficient in the quench hardening layer is 2.6 × 10 ⁻¹¹ m ² / s. small.

  In the above-described rolling bearing for automotive electrical equipment, the hardened hardened layer may contain nitrogen. In the above-described rolling bearing for automotive electrical equipment, the nitrogen concentration in the hardened hardened layer may be 0.05 weight percent or more and 0.6 weight percent or less.

  In the above-described rolling bearing for automotive electrical equipment, the volume ratio of the austenite phase in the hardened hardened layer may be 10% or more and 40% or less. In the above-described rolling bearing for automotive electrical equipment, the hardness of the hardened hardened layer may be 58 HRC or more and 64 HRC or less.

The rolling bearing for the speed reducer according to one aspect of the present invention rotatably supports the planetary gear while being oil-lubricated in the speed reducer that transmits and reduces the rotation of the input shaft to the output shaft by using the planetary gear. A rolling bearing for an accelerator / decelerator includes an inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring. The inner ring, outer ring and rolling elements are made of steel. A quench hardening layer is provided on at least one of the raceway surfaces of the inner ring and the outer ring and the rolling surface of the rolling element, and the hydrogen diffusion coefficient in the quench hardening layer is 2.6 × 10 ⁻¹¹ m ² / s. small.

  In the above-described rolling bearing for the speed reducer, the hardened hardened layer may contain nitrogen. In the above-described rolling bearing for speed reducer, the nitrogen concentration in the hardened hardened layer may be 0.05 weight percent or more and 0.6 weight percent or less.

  In the above-described rolling bearing for speed reducer, the volume ratio of the austenite phase in the hardened hardened layer may be 10% or more and 40% or less. In the above-described rolling bearing for the speed reducer, the hardness of the hardened hardened layer may be 58 HRC or more and 64 HRC or less.

  According to the rolling bearing, the rolling accessory bearing for automobile electrical equipment, and the rolling bearing for speed increasing / decreasing device according to one embodiment of the present invention, it is possible to suppress the occurrence of hydrogen embrittlement due to the penetration of hydrogen from the surface.

It is sectional drawing of the rolling component 10 which concerns on 1st Embodiment. It is an enlarged view in the area | region II of FIG. 1 is a schematic diagram of a hydrogen diffusion coefficient measuring device 20. FIG. It is process drawing which shows the manufacturing method of the rolling component 10 which concerns on 1st Embodiment. It is sectional drawing of the rolling bearing 100 which concerns on 1st Embodiment. It is a graph which shows the rotation conditions in a rolling fatigue test. It is sectional drawing of the automotive electrical equipment auxiliary | assistant machine in which the rolling bearing 200 which concerns on 2nd Embodiment was used. It is sectional drawing of the rolling bearing 200 which concerns on 2nd Embodiment. It is sectional drawing of the gearbox 500 in which the rolling bearing 400 which concerns on 3rd Embodiment was used. It is sectional drawing of the rolling bearing 400 which concerns on 3rd Embodiment.

  A first embodiment 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 the description thereof will not be repeated.

(Configuration of the rolling component according to the first embodiment)
Below, the structure of the rolling component which concerns on 1st Embodiment is demonstrated.

  FIG. 1 is a cross-sectional view of a rolling component 10 according to the first embodiment. As shown in FIG. 1, the rolling component 10 according to the first embodiment is an inner ring (that is, a shaft washer) of a thrust ball bearing. However, the rolling component 10 is not limited to this. The rolling component 10 may be an outer ring (that is, a housing washer) of a thrust ball bearing. The rolling component 10 may be a rolling element of a thrust ball bearing.

  The rolling component 10 is made of steel. The steel used for the rolling component 10 is, for example, a high carbon chrome bearing steel defined in JIS standards (JIS 4805: 2008). The steel used for the rolling part 10 may be SUJ2 or SUJ3 defined in JIS standard (JIS 4805: 2008). The steel used for the rolling part 10 may be a high speed steel such as M50 defined in AMS6491.

  The rolling component 10 has a ring shape. The rolling component 10 has an upper surface 10a, a bottom surface 10b, an inner peripheral surface 10c, and an outer peripheral surface 10d. The bottom surface 10b is the opposite surface of the top surface 10a. The inner peripheral surface 10c and the outer peripheral surface 10d are connected to the upper surface 10a and the bottom surface 10b. The upper surface 10 a is a raceway surface of the rolling component 10.

  FIG. 2 is an enlarged view of region II in FIG. As shown in FIG. 2, the rolling component 10 has a hardened and hardened layer 11. The quench hardened layer 11 is on the surface of the rolling part 10. More specifically, the hardened and hardened layer 11 is on the upper surface 10 a (track surface) of the rolling component 10.

The hydrogen diffusion coefficient in the quench hardened layer 11 is smaller than 2.6 × 10 ⁻¹¹ m ² / s. The hydrogen diffusion coefficient in the quench hardened layer 11 may be 2.1 × 10 ⁻¹¹ m ² / s or less. The hydrogen diffusion coefficient in the quench hardened layer 11 may be 1.9 × 10 ⁻¹¹ m ² / s or less.

The hydrogen diffusion coefficient in the quench hardened layer 11 may be 1.6 × 10 ⁻¹¹ m ² / s or less. The hydrogen diffusion coefficient in the quench hardened layer 11 may be 1.4 × 10 ⁻¹¹ m ² / s or less. The hydrogen diffusion coefficient in the quench hardened layer 11 may be 0.15 × 10 ⁻¹¹ m ² / s or less.

  The hydrogen diffusion coefficient is measured by an electrochemical hydrogen permeation method. FIG. 3 is a schematic diagram of the hydrogen diffusion coefficient measuring apparatus 20. As shown in FIG. 3, the measuring device 20 includes an anode tank 21, a cathode tank 22, an anode electrode 23, a cathode electrode 24, a galvanostat 25, and a potentiostat 26. The anode tank 21 and the cathode tank 22 are divided by a test piece 27. The test piece 27 has a thickness L. The thickness L is, for example, 1 mm. The anode electrode 23 and the cathode electrode 24 are made of platinum (Pt).

  An anode liquid 28 is placed in the anode tank 21. The anolyte 28 is a 1 mol / L sodium hydroxide aqueous solution. The cathode tank 22 contains a catholyte 29. Catholyte 29 is a mixture of 0.05 mol / L sulfuric acid and thiouric acid. The anode electrode 23 is immersed in the anolyte 28. The cathode electrode 24 is immersed in the catholyte 29.

  One terminal of the galvanostat 25 is connected to the cathode electrode 24. The other terminal of the galvanostat 25 is connected to the test piece 27. One terminal of the potentiostat 26 is connected to the anode electrode 23. The other terminal of the potentiostat 26 is connected to the test piece 27.

  In the measurement of the hydrogen diffusion coefficient, a current is supplied to the test piece 27 by the galvanostat 25. Thereby, hydrogen is generated on the cathode solution 29 side of the test piece 27. The generated hydrogen enters the inside of the test piece 27 from the surface on the catholyte 29 side.

The hydrogen that has entered the inside of the test piece 27 moves while diffusing in the test piece 27. Hydrogen that reaches the surface of the test piece 27 on the anolyte 28 side is ionized. Thereby, an ionization current flows. When the time until the ionization current starts to flow is tb and the thickness of the test piece 27 is L, the hydrogen diffusion coefficient is obtained by L ² /(15.3×tb). Note that the measurement of the hydrogen diffusion coefficient is performed within a range of 20 ° C. or more and 25 ° C. or less.

  The quench hardened layer 11 contains a martensite phase and an austenite phase. The volume ratio of the austenite phase in the quench hardened layer 11 is preferably 10 percent or more and 40 percent or less.

  The volume ratio of the austenite phase in the quench hardened layer 11 is measured by X-ray diffraction. That is, the volume ratio of the austenite phase in the quench-hardened layer 11 is determined by measuring the intensity ratio between the diffraction peak of the austenite phase and the diffraction peak of the martensite phase in the quench-hardened layer 11.

  The quench hardening layer 11 may contain nitrogen. The nitrogen concentration in the hardened and hardened layer 11 is preferably 0.05 weight percent or more and 0.6 weight percent or less. The nitrogen concentration in the quench hardened layer 11 is measured by EPMA (Electron Probe Micro Analyzer).

  The hardness of the hardened and hardened layer 11 is preferably 58 HRC or more and 64 HRC or less. The hardness of the quench-hardened layer 11 is measured according to the method defined in JIS Z2245: 2016.

(Method for manufacturing a rolling part according to the first embodiment)
Below, the manufacturing method of the rolling component 10 which concerns on 1st Embodiment is demonstrated.

  FIG. 4 is a process diagram illustrating a method for manufacturing the rolling component 10 according to the first embodiment. As shown in FIG. 4, the manufacturing method of the rolling component 10 which concerns on 1st Embodiment has preparatory process S1, quenching process S2, tempering process S3, and post-processing process S4. The quenching step S2 is performed after the preparation step S1. The tempering step S3 is performed after the quenching step S2. The post-processing step S4 is performed after the tempering step S3.

  In preparation process S1, the processing target object used as rolling component 10 is prepared by performing the manufacturing method of rolling component 10 concerning a 1st embodiment. This processing object is a steel ring-shaped member when the rolling component 10 is an inner ring or an outer ring of a thrust ball bearing, for example. This processing object is a steel spherical member when the rolling component 10 is a rolling element of a thrust ball bearing, for example.

  The steel constituting the workpiece is, for example, bearing steel. Preferably, the steel constituting the workpiece is a high carbon chromium bearing steel defined in JIS standards (JIS 4805: 2008). The steel constituting the workpiece may be SUJ2 or SUJ3 defined in the JIS standard (JIS 4805: 2008). The steel constituting the workpiece may be a high speed steel such as M50 defined in AMS6491.

In the quenching step S2, the steel constituting the workpiece is quenched. The quenching step S2 has a heating step S21 and a cooling step S22. In the heating step S21, the workpiece is heated. In the heating step S21, the processing object, the object configuration to steel A ₁ point or more temperature (hereinafter may referred to the heating temperature) is heated to. The heating temperature is, for example, 800 ° C. or higher and 900 ° C. or lower.

  The processing object is heated in the heating step S21, for example, in a heating furnace. The atmosphere in the heating furnace is, for example, RX gas. A gas containing nitrogen may be added to the atmosphere in the heating furnace. A specific example of the nitrogen-containing gas is ammonia gas. In the heating step S21, after the workpiece is heated to the heating temperature, the workpiece is held at the heating temperature for a predetermined time (hereinafter referred to as a holding time).

  As the holding time becomes longer or the heating temperature becomes higher, in the heating step S21, carbon in the steel material constituting the workpiece is dissolved into the austenite phase. As the amount of carbon in the austenite phase increases, the residual austenite phase tends to increase. Therefore, the volume ratio of the austenite phase in the quenched and hardened layer 11 can be controlled by controlling the holding time and the heating temperature.

  When the amount of the austenite stabilizing element in the steel material constituting the workpiece is increased, the residual austenite phase tends to increase. Therefore, by using a steel type that contains a lot of alloy elements that are austenite stabilizing elements in the steel material that constitutes the workpiece, or by adding a gas containing nitrogen to the heating atmosphere in the heating step S21, The volume ratio of the austenite phase can be controlled.

  Nitrogen in the steel material constituting the object to be processed forms a nitride with Cr or the like in the steel material constituting the object to be processed. This nitride hardens the steel material constituting the workpiece by being finely dispersed in the steel material constituting the workpiece. In addition, since nitride serves as a hydrogen trap site, the hydrogen diffusion coefficient is reduced. Therefore, in the heating step S21, the hardness and hydrogen diffusion coefficient of the hardened hardened layer 11 can be controlled by controlling the concentration of the gas containing nitrogen, the heating temperature, and the holding time.

In the cooling step S22, the workpiece is cooled. In the cooling step S22, the object to be processed is cooled from the heating temperature to a temperature not higher than the _MS point of the steel constituting the object to be processed (hereinafter referred to as a cooling temperature). The workpiece to be cooled in the cooling step S22 is performed using any conventionally known refrigerant. The refrigerant used for cooling the workpiece is, for example, oil or water.

  Note that the cooling temperature and cooling rate in the cooling step S22 affect the amount of martensite phase generated in the cooling step S22 (in other words, the amount remaining in the austenite phase even after the cooling step S22). Therefore, the volume ratio of the austenite phase in the quenched and hardened layer 11 can also be controlled by controlling the cooling temperature and the cooling rate.

In the tempering step S3, the steel constituting the workpiece is tempered. Tempering of the workpiece is performed by holding the workpiece at a temperature below A ₁ (hereinafter referred to as tempering temperature) for a predetermined time (hereinafter referred to as tempering time). The tempering temperature is, for example, 180 ° C. The tempering time is, for example, 2 hours.

  In the tempering step S3, the austenite phase that has not become the martensite phase even in the cooling step S22 is decomposed into a ferrite phase and a carbide phase. The amount of austenite phase that is decomposed into ferrite and carbide phases varies by controlling the tempering temperature and tempering time. Therefore, the volume ratio of the austenite phase in the quenched and hardened layer 11 can also be controlled by controlling the tempering temperature and the tempering time.

  In post-processing process S4, the post-processing with respect to a process target object is performed. In the post-processing step S4, for example, cleaning of the processing object, machining such as grinding and polishing of the processing object, and the like are performed. As described above, the rolling component 10 is manufactured.

(Configuration of the rolling bearing according to the first embodiment)
Below, the structure of the rolling bearing 100 which concerns on 1st Embodiment is demonstrated. FIG. 5 is a cross-sectional view of the rolling bearing 100 according to the first embodiment. As shown in FIG. 5, the rolling bearing 100 is a thrust ball bearing. However, the rolling bearing 100 is not limited to this.

  The rolling bearing 100 includes an inner ring 30, an outer ring 40, rolling elements 50, and a cage 60. The inner ring 30 and the outer ring 40 are arranged so that the respective raceway surfaces face each other. The rolling element 50 is disposed between the inner ring 30 and the outer ring 40. The cage 60 is disposed between the inner ring 30 and the outer ring 40. The cage 60 is provided with a through hole. By allowing the rolling elements 50 to pass through the through holes of the cage 60, the spacing between the rolling elements 50 in the circumferential direction is maintained. The cage 60 is made of, for example, a resin material. At least one of the inner ring 30, the outer ring 40, and the rolling element 50 is the rolling component 10 described above. That is, at least one of the raceway surfaces of the inner ring 30 and the outer ring 40 and the rolling surface of the rolling element 50 is provided with the above-mentioned quench hardening layer 11.

(Effects of rolling parts and rolling bearings according to the first embodiment)
Below, the effect of the rolling component 10 which concerns on 1st Embodiment, and the rolling bearing 100 which concerns on 1st Embodiment is demonstrated.

As described above, in the rolling component 10 according to the first embodiment, the hydrogen diffusion coefficient in the hardened and hardened layer 11 is smaller than 2.6 × 10 ⁻¹¹ m ² / s. Therefore, in the rolling component 10 according to the first embodiment, it takes a longer time for hydrogen that has entered from the surface to diffuse into the hardened and hardened layer 11. Therefore, according to the rolling component according to the first embodiment, it is possible to suppress the occurrence of hydrogen embrittlement due to the penetration of hydrogen from the surface.

  Nitrogen forms a nitride with the alloy elements in the steel constituting the rolling part 10. Therefore, when the quench hardening layer 11 contains nitrogen, the content of nitride in the quench hardening layer 11 increases, resulting in a decrease in the hydrogen diffusion coefficient of the quench hardening layer 11 and a quenching. The hardness of the cured layer 11 increases.

  When the nitrogen concentration in the quench-hardened layer 11 exceeds 0.6 weight percent, the amount of Cr that reacts with nitrogen to become a nitride increases. Cr that reacts with nitrogen to become nitride does not contribute to the improvement of the hardenability of the hardened hardened layer 11. On the other hand, when the nitrogen concentration in the quench-hardened layer 11 is less than 0.05 weight percent, the amount of nitride formed is small, and the influence on the hardness increase and the hydrogen diffusion coefficient reduction of the quench-hardened layer 11 is small. Therefore, when the nitrogen concentration in the hardened layer 11 is 0.05 weight percent or more and 0.6 weight percent or less, the hardening of the hardened layer 11 is performed while increasing the hardness and reducing the hydrogen diffusion coefficient due to the introduction of nitrogen. Imperviousness can be ensured.

  The austenite phase has a smaller hydrogen diffusion coefficient than the martensite phase. Therefore, the larger the volume ratio of the austenite phase in the hardened layer 11, the lower the hydrogen diffusion coefficient of the hardened layer 11. On the other hand, the austenite phase in the hardened and hardened layer 11 may be transformed into a martensite phase while using the rolling component 10. For this reason, if the volume ratio of the austenite phase in the quench hardened layer 11 is too large, the dimensional stability decreases. Therefore, when the volume ratio of the austenite phase in the quench hardened layer 11 is 10% or more and 40% or less, the hydrogen diffusion coefficient can be lowered while maintaining dimensional stability.

  The surface (track surface) of the rolling component 10 is required not to be deformed even when subjected to contact stress. Therefore, the hardened and hardened layer 11 on the surface of the rolling component 10 is required to have hardness. On the other hand, if the hardness of the hardened hardened layer 11 is excessively high, the toughness decreases. Therefore, when the hardness of the hardened hardened layer 11 is 58 HRC or more and 64 HRC or less, deformation of the surface of the rolling component 10 due to application of contact stress while securing toughness on the surface of the rolling component 10 is achieved. Can be suppressed.

  As described above, at least one of the inner ring 30, the outer ring 40, and the rolling element 50 constituting the rolling bearing 100 according to the first embodiment is the rolling component 10. Therefore, according to the rolling bearing 100 which concerns on 1st Embodiment, generation | occurrence | production of hydrogen embrittlement accompanying hydrogen infiltrating from the surface can be suppressed.

(Rolling fatigue test)
Below, the rolling fatigue test implemented with respect to the rolling component 10 which concerns on 1st Embodiment is demonstrated.

<Sample material>
Table 1 shows the preparation conditions of the specimens subjected to the rolling fatigue test, the nitrogen concentration in the hardened and hardened layer 11, the volume ratio of the austenite phase in the hardened and hardened layer 11, and the hydrogen in the hardened and hardened layer 11. Indicates the diffusion coefficient. As shown in Table 1, the steel type used for Specimen 1 to Specimen 3 is SUJ2. The steel type used for the specimen 4 and specimen 5 is SUJ3. The steel type used for the specimen 6 is M50.

  The heating step S21 for the test material 1 and the test material 4 was performed at a heating temperature of 850 ° C. in an RX gas atmosphere. The heating step S21 for the test material 6 was performed at a heating temperature of about 1100 ° C. in an RX gas atmosphere. The heating step S21 for the sample material 2, the sample material 3, and the sample material 5 was performed in an RX gas atmosphere to which a heating temperature of 850 ° C. and ammonia gas were added. In the sample material 2 and the sample material 5, the concentration of ammonia gas is adjusted so that the nitrogen concentration in the quench-hardened layer 11 is 0.2 weight percent. The concentration of ammonia gas was adjusted so that the nitrogen concentration in the cured layer 11 was 0.4 weight percent. For Specimens 1 to 6, tempering step S3 was performed at a tempering temperature of 180 ° C. and a tempering time of 2 hours (120 minutes).

  The volume ratio of the austenite phase in the hardened and hardened layer 11 of the specimen 1 was 8.9 percent. The volume ratio of the austenite phase in the quenched and hardened layer 11 of the specimen 2 was 21.7%.

  The volume ratio of the austenite phase in the quenched and hardened layer 11 of the specimen 3 was 29.6 percent. The volume ratio of the austenite phase in the quenched and hardened layer 11 in the test material 4 was 20.3%. The volume ratio of the austenite phase in the quenched and hardened layer 11 of the specimen 5 was 31.8%. The volume ratio of the austenite phase in the quenched and hardened layer 11 of the specimen 6 was 3.3%.

The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the test material 1 was 2.63 × 10 ⁻¹¹ m ² / s. The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the specimen 2 was 2.09 × 10 ⁻¹¹ m ² / s.

The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the specimen 3 was 1.60 × 10 ⁻¹¹ m ² / s. The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the specimen 4 was 1.88 × 10 ⁻¹¹ m ² / s. The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the test material 5 was 1.40 × 10 ⁻¹¹ m ² / s. The hydrogen diffusion coefficient of the quenched and hardened layer 11 of the test material 6 was 0.15 × 10 ⁻¹¹ m ² / s.

<Rolling fatigue test method>
A thrust ball bearing was constructed using each specimen. The rolling element of this thrust ball bearing was a steel ball made of SUS440C. In this thrust ball bearing, as a lubricant, a mixture of glycol-based lubricant and pure water was used. As a result, this thrust ball bearing is in a state where hydrogen can enter from the raceway surface.

  In the rolling fatigue test, an axial load of 4.9 kN was applied to this thrust ball bearing (in this state, the maximum contact surface pressure between the raceway surface and the rolling element was 2.3 GPa by elastic Hertz contact calculation). And the inner ring is rotated relative to the outer ring. FIG. 6 is a graph showing rotation conditions in the rolling fatigue test. As shown in FIG. 6, the relative rotation of the inner ring with respect to the outer ring was performed with 0.5 second as one cycle.

  Among the 0.5 seconds, in the first 0.1 seconds, the rotation speed increased linearly from 0 rotations / minute to 2500 rotations / minute. In the next 0.3 seconds, the rotation speed was maintained at 2500 rpm. In the next 0.1 second, the rotational speed decreased linearly from 2500 rpm to 0 rpm.

<Rolling fatigue test results>
Table 2 shows the rolling fatigue test results. In Table 2, L ₁₀ and L ₅₀ were determined by fitting spallation life of the thrust ball bearing constituted by using each sample (the time until flaking occurs track surface) to 2 parametric Weibull distribution 10% lifetime and 50% lifetime, and e is the Weibull slope (shape parameter) of the 2-parameter Weibull distribution.

As shown in Table 2, the thrust ball bearing configured using the test materials 2 to 6 has a longer peel life than the thrust ball bearing configured using the test material 1. As described above, in the test material 1, the hydrogen diffusion coefficient of the quench hardened layer 11 is 2.6 × 10 ⁻¹¹ m ² / s or more, while in the test material 2 to the test material 6, The hydrogen diffusion coefficient of the cured layer 11 was less than 2.6 × 10 ⁻¹¹ m ² / s. From this comparison, it is experimental that the hardened hardened layer 11 has a hydrogen diffusion coefficient of less than 2.6 × 10 ⁻¹¹ m ² / s, thereby suppressing the occurrence of hydrogen embrittlement due to the penetration of hydrogen from the surface. It was made clear.

  As described above, the quench hardening layer 11 of the test material 1 has a volume ratio of the austenite phase of less than 10%, while the quench hardening layer 11 of the test material 2 to the test material 5 has a volume of the austenite phase. The ratio was in the range of 10 percent to 40 percent. From this comparison, when the volume ratio of the austenite phase in the hardened hardened layer 11 is in the range of 10 percent or more and 40 percent or less, it is experimentally possible to suppress the occurrence of hydrogen embrittlement due to the penetration of hydrogen from the surface. It was made clear.

  The thrust ball bearing constructed using the test material 5 showed a longer peeling life than the thrust ball bearing constructed using the test material 4. As described above, the hardened and hardened layer 11 of the test material 4 does not contain nitrogen, while the hardened and hardened layer 11 of the test material 5 contains nitrogen. From this comparison, it was experimentally clarified that when the hardened and hardened layer 11 contains nitrogen, generation of hydrogen embrittlement accompanying hydrogen intrusion from the surface can be further suppressed.

(Configuration of the rolling bearing according to the second embodiment)
Below, the structure of the rolling bearing 200 which concerns on 2nd Embodiment is demonstrated. In the following, differences from the configuration of the rolling bearing 100 according to the first embodiment will be mainly described, and overlapping description will not be repeated.

  FIG. 7 is a cross-sectional view of an automotive electrical accessory using a rolling bearing 200 according to the second embodiment. As shown in FIG. 7, the automobile electrical accessory is, for example, an alternator 300. The automobile electrical accessory may be an idler pulley, a car air conditioner electromagnetic clutch, a fan coupling device, an intermediate pulley, an electric fan motor, or the like.

  The alternator 300 includes a rotor 301, a housing 302, a shaft 303, a stator 304, a pulley 305, and a rolling bearing 200. The housing 302 is disposed so as to surround the rotor 301. The shaft 303 is disposed so as to penetrate the central portion of the rotor 301 and the wall surface of the housing 302. The shaft 303 is rotationally driven by power generated by a power source such as an engine (not shown). A stator 304 is disposed inside the housing 302 so as to face the outer peripheral surface of the rotor 301.

  A rolling bearing 200 is disposed between the shaft 303 and the housing 302. The shaft 303 is rotatably supported by the housing 302 by the rolling bearing 200. That is, the rolling bearing 200 is a rolling bearing for automobile electrical accessory.

  A pulley 305 is attached to one end of the shaft 303 outside the housing 302. The pulley 305 has an annular shape. An engagement groove 305 a is formed on the outer peripheral surface of the pulley 305. A transmission belt (not shown) is hung on the engagement groove 305a.

  The shaft 303 is driven to rotate around the central axis by the transmission belt rotating by power from an engine (not shown) or the like. The rotor 301 rotates around the central axis of the shaft 303 together with the shaft 303. As a result, the rotor 301 rotates relative to the stator 304, and an electromotive force is generated in the coil of the stator 304 due to electromagnetic induction between the rotor 301 and the stator 304.

  FIG. 8 is a cross-sectional view of a rolling bearing 200 according to the second embodiment. As shown in FIG. 8, the rolling bearing 200 is, for example, a deep groove ball bearing. However, the rolling bearing 200 is not limited to this. The rolling bearing 200 includes an inner ring 31, an outer ring 41, rolling elements 51, and a cage 61. Although not shown, the rolling bearing 200 is filled with lubricating grease.

  The inner ring 31 has a ring shape. The inner ring 31 has an outer peripheral surface 31a. The outer peripheral surface 31 a constitutes a raceway surface of the inner ring 31. A shaft 303 is inserted into the inner ring 31. The outer ring 41 has a ring shape. The outer ring 41 has an inner peripheral surface 41a. The inner peripheral surface 41 a constitutes the raceway surface of the outer ring 41. The outer ring 41 is attached to the housing 302. The inner ring 31 and the outer ring 41 are arranged so that the outer peripheral surface 31a and the inner peripheral surface 41a face each other.

  The rolling element 51 has a spherical shape. The rolling element 51 is disposed between the inner ring 31 and the outer ring 41. More specifically, the rolling element 51 is disposed between the outer peripheral surface 31a and the inner peripheral surface 41a. The rolling element 51 has a surface 51a. The surface 51a constitutes a rolling surface of the rolling element 51.

  The inner ring 31, the outer ring 41, and the rolling element 51 are made of steel. The steel used for the inner ring 31, the outer ring 41, and the rolling element 51 is, for example, high carbon chrome bearing steel defined in JIS standards (JIS 4805: 2008). The steel used for the inner ring 31, the outer ring 41, and the rolling element 51 may be SUJ2 or SUJ3 defined in JIS standards. The steel used for the inner ring 31, the outer ring 41, and the rolling element 51 may be a high speed steel such as M50 defined in AMS6491. The hardened and hardened layer 11 is provided on at least one of the raceway surfaces of the inner ring 31 and the outer ring 41 and the rolling surface of the rolling element 51.

  The cage 61 has a ring shape. The cage 61 is disposed between the inner ring 31 and the outer ring 41. The retainer 61 is provided with a through hole. By allowing the rolling elements 51 to pass through the through holes of the retainer 61, the spacing between the rolling elements 51 in the circumferential direction is maintained. The cage 61 is made of, for example, a resin material.

  Since the manufacturing method of the inner ring 31, the outer ring 41, and the rolling element 51 is the same as the manufacturing method of the rolling component 10 according to the first embodiment, the description thereof is omitted here.

(Effect of the rolling bearing according to the second embodiment)
Below, the effect of the rolling bearing 200 which concerns on 2nd Embodiment is demonstrated. In the following, differences from the effects of the rolling bearing 100 according to the first embodiment will be mainly described, and overlapping description will not be repeated.

  Rolling bearings for automotive electrical accessories are used in a high-temperature, high-speed rotating environment. At this time, grease enclosed in the rolling bearing is decomposed to generate hydrogen. The generated hydrogen enters the inside of each rolling part constituting the rolling bearing, thereby causing hydrogen embrittlement. However, in the rolling bearing 200, since the above-described hardened and hardened layer 11 is provided on at least one of the raceway surfaces of the inner ring 31 and the outer ring 41 and the rolling surfaces of the rolling elements 51, the rolling bearing 200 enters from the surface. It takes longer time for the diffused hydrogen to diffuse. Therefore, according to the rolling bearing 200, generation | occurrence | production of the hydrogen embrittlement accompanying hydrogen infiltrating from the surface can be suppressed.

(Configuration of the rolling bearing according to the third embodiment)
Below, the structure of the rolling bearing 400 which concerns on 3rd Embodiment is demonstrated. In the following, differences from the configuration of the rolling bearing 100 according to the first embodiment will be mainly described, and overlapping description will not be repeated.

  FIG. 9 is a cross-sectional view of a speed increaser 500 in which the rolling bearing 400 according to the third embodiment is used. As shown in FIG. 9, the speed increaser 500 includes an input shaft 501, an intermediate output shaft 502, an output shaft 503, a primary speed increaser 504, a secondary speed increaser 505, a housing 506, and a rolling mechanism. Bearing 400. That is, the rolling bearing 400 is a speed increasing roller bearing. In the following description, the rolling bearing 400 will be described as a speed increaser rolling bearing, but the rolling bearing 400 can also be used as a reduction gear rolling bearing.

  The primary speed increaser 504 is composed of a planetary gear mechanism. Specifically, the primary speed increaser 504 includes a carrier 504a, a planetary gear 504b, a ring gear 504c, and a sun gear 504d. The carrier 504a is integrated with the input shaft 501. The planetary gear 504b is installed on the carrier 504a. The sun gear 504d is integrated with the intermediate output shaft 502. The ring gear 504c is meshed with the planetary gear 504b and the sun gear 504d. Thus, the rotation of the input shaft 501 is transmitted to the intermediate output shaft 502 through the carrier 504a, the planetary gear 504b, and the ring gear 504c.

  The rolling bearing 400 rotatably supports the shaft of the planetary gear 504b. In addition, the rolling bearing 400 may similarly support the shafts other than the planetary gear 504b so as to be rotatable. The rolling bearing 400 is immersed in the lubricating oil 506b stored in the lubricating oil storage tank 506a in the housing 506. The lubricating oil 506b stored in the lubricating oil storage tank 506a is circulated by piping and a pump (not shown).

  Secondary speed increaser 505 has gears 505a to 505d. A gear train including the gears 505 a to 505 d transmits the rotation of the intermediate output shaft 502 to the output shaft 503. As described above, the speed increaser 500 increases the rotation speed of the input shaft 501 and transmits it to the output shaft 503.

  FIG. 10 is a cross-sectional view of a rolling bearing 400 according to the third embodiment. As shown in FIG. 10, the rolling bearing 400 is a deep groove ball bearing, for example. However, the rolling bearing 400 is not limited to this. The rolling bearing 400 includes an inner ring 32, an outer ring 42, rolling elements 52, and a cage 62.

  The inner ring 32 has a ring shape. The inner ring 32 has an outer peripheral surface 32a. The outer peripheral surface 32 a constitutes a raceway surface of the inner ring 32. The outer ring 42 has a ring shape. The outer ring 42 has an inner peripheral surface 42a. The inner peripheral surface 42 a constitutes a raceway surface of the outer ring 42. The inner ring 32 and the outer ring 42 are disposed so that the outer peripheral surface 32a and the inner peripheral surface 42a face each other.

  The rolling element 52 has a spherical shape. The rolling element 52 is disposed between the inner ring 32 and the outer ring 42. More specifically, the rolling element 52 is disposed between the outer peripheral surface 32a and the inner peripheral surface 42a. The rolling element 52 has a surface 52a. The surface 52a constitutes a rolling surface of the rolling element 52.

  The inner ring 32, the outer ring 42, and the rolling element 52 are made of steel. The steel used for the inner ring 32, the outer ring 42 and the rolling element 52 is, for example, a high carbon chromium bearing steel defined in JIS standards (JIS 4805: 2008). The steel used for the inner ring 32, the outer ring 42, and the rolling element 52 may be SUJ2 or SUJ3 defined in JIS standards. The steel used for the inner ring 32, the outer ring 42, and the rolling element 52 may be a high speed steel such as M50 defined in AMS6491. The hardened and hardened layer 11 is provided on at least one of the raceway surfaces of the inner ring 32 and the outer ring 42 and the rolling surface of the rolling element 52.

  The cage 62 has a ring shape. The cage 62 is disposed between the inner ring 32 and the outer ring 42. The retainer 62 is provided with a through hole. By allowing the rolling elements 52 to pass through the through holes of the cage 62, the spacing between the rolling elements 52 in the circumferential direction is maintained. The cage 62 is made of, for example, a resin material.

  Since the manufacturing method of the inner ring 32, the outer ring 42, and the rolling element 52 is the same as the manufacturing method of the rolling component 10 according to the first embodiment, the description thereof is omitted here.

(Effect of the rolling bearing according to the third embodiment)
Below, the effect of the rolling bearing 400 which concerns on 3rd Embodiment is demonstrated. In the following, differences from the effects of the rolling bearing 100 according to the first embodiment will be mainly described, and overlapping description will not be repeated.

  Since the speed reducer is often incorporated outdoors in wind power generators and the like, the rolling bearing for the speed reducer tends to mix water into the lubricating oil and increase the amount of hydrogen generated. In the rolling bearing 400, at least one of the raceway surfaces of the inner ring 32 and the outer ring 42 and the rolling surface of the rolling element 52 is provided with the above-described quench hardened layer 11. Takes longer to diffuse. Therefore, according to the rolling bearing 400, it is possible to suppress the occurrence of hydrogen embrittlement that accompanies the intrusion of hydrogen from the surface even under the above situation.

  Although the embodiment of the present invention has been described above, the above-described embodiment can be variously modified. Further, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The above embodiments are particularly advantageously applied to rolling parts and bearings using the rolling parts.

  10 rolling parts, 10a top surface, 10b bottom surface, 10c inner peripheral surface, 10d outer peripheral surface, 11 quench hardened layer, 20 measuring device, 21 anode tank, 22 cathode tank, 23 anode electrode, 24 cathode electrode, 25 galvanostat, 26 potentiostat, 27 test piece, 28 anolyte, 29 catholyte, 30, 31, 32 inner ring, 40, 41, 42 outer ring, 50 rolling element, 60, 61, 62 cage, 100, 200, 400 rolling bearing, 300 alternator, 301 rotor, 302 housing, 303 shaft, 304 stator, 305 pulley, 305a engagement groove, 500 speed increaser, 501 input shaft, 502 intermediate output shaft, 503 output shaft, 504 primary speed increaser, 504a carrier, 504b planetary gear, 504c ring gear, 5 4d Sun gear, 505 Secondary gear, 505a, 505b, 505c, 505d Gear, 506 Housing, 506a Lubricating oil storage tank, 506b Lubricating oil, L thickness, S1 preparation process, S2 Quenching process, S3 Tempering process , S4 post-processing step, S21 heating step, S22 cooling step.

Claims (17)

An inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring,
The inner ring, the outer ring and the rolling element are made of steel,
At least one of the raceway surfaces of the inner ring and the outer ring and the rolling surface of the rolling element is provided with a quench hardening layer,
A rolling bearing having a hydrogen diffusion coefficient in the quench-hardened layer of less than 2.6 × 10 ⁻¹¹ m ² / s.   The rolling bearing according to claim 1, wherein the quench hardened layer contains nitrogen.   The rolling bearing according to claim 2, wherein the nitrogen concentration in the quench-hardened layer is 0.05 weight percent or more and 0.6 weight percent or less.   The rolling bearing according to any one of claims 1 to 3, wherein a volume ratio of the austenite phase in the hardened hardened layer is 10 percent or more and 40 percent or less.   The rolling bearing according to any one of claims 1 to 4, wherein the hardness of the hardened hardened layer is 58 HRC or more and 64 HRC or less.   The rolling bearing according to any one of claims 1 to 5, wherein the steel is high-carbon chromium bearing steel.   The rolling bearing according to claim 6, wherein the high carbon chromium bearing steel is SUJ2 or SUJ3. A rolling bearing for automotive electrical equipment that supports a rotationally driven shaft rotatably with respect to a stationary member,
An inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring,
The inner ring, the outer ring and the rolling element are made of steel,
At least one of the raceway surfaces of the inner ring and the outer ring and the rolling surface of the rolling element is provided with a quench hardening layer,
A rolling bearing for automotive electrical equipment, wherein a hydrogen diffusion coefficient in the quench hardened layer is smaller than 2.6 × 10 ⁻¹¹ m ² / s.   The rolling bearing for automotive electrical equipment according to claim 8, wherein the quench hardened layer contains nitrogen.   The rolling bearing for automotive electrical equipment according to claim 9, wherein the nitrogen concentration in the hardened hardening layer is 0.05 weight percent or more and 0.6 weight percent or less.   The rolling bearing for automotive electrical equipment according to any one of claims 8 to 10, wherein a volume ratio of the austenite phase in the hardened hardened layer is 10 percent or more and 40 percent or less.   The rolling bearing for automotive electrical equipment according to any one of claims 8 to 11, wherein the hardness of the hardened hardened layer is 58HRC or more and 64HRC or less. A rolling bearing for a speed reducer that rotatably supports the planetary gear while being oil-lubricated in an speed reducer that transmits and reduces the rotation of the input shaft to the output shaft by using a planetary gear.
An inner ring, an outer ring, and a rolling element disposed between the inner ring and the outer ring,
The inner ring, the outer ring and the rolling element are made of steel,
At least one of the raceway surfaces of the inner ring and the outer ring and the rolling surface of the rolling element is provided with a quench hardening layer,
A rolling bearing for a speed ^reducer , wherein a hydrogen diffusion coefficient in the hardened hardening layer is smaller than 2.6 × 10 ⁻¹¹ m ² / s.   The rolling bearing for a speed reducer according to claim 13, wherein the quench hardened layer contains nitrogen.   The rolling bearing for speed reducer according to claim 14, wherein a nitrogen concentration in the hardened and hardened layer is 0.05 to 0.6 weight percent.   The rolling bearing for a speed reducer according to any one of claims 13 to 15, wherein a volume ratio of the austenite phase in the quench hardened layer is 10 percent or more and 40 percent or less.   The rolling bearing for a speed reducer according to any one of claims 13 to 16, wherein the hardness of the hardened hardened layer is 58HRC or more and 64HRC or less.