CN118057038A - Bearing - Google Patents

Abstract

A bearing (101) includes an inner ring (1A) and an outer ring (1B) disposed on the outer peripheral side of the inner ring (1A). Only one of the raceway surface (11) of the inner ring (1A) and the raceway surface (12) of the outer ring (1B) is in the range of a first region having an arithmetic average roughness Ra of 0.1 μm or less, a skewness Rsk < 0, and a compressive residual stress of 700MPa or more.

Description

Bearing

Technical Field

The present disclosure relates to a bearing.

Background

As a method for prolonging the life of a bearing, the following techniques have been conventionally disclosed. The following technique is proposed in Japanese patent application laid-open No. 2004-263768: the low-cleanliness steel containing large nonmetallic inclusions is polished to crush nonmetallic inclusions and reduce the diameters, and the bearing life is prolonged. The following method is proposed in Japanese patent laid-open No. 2004-116569: the track surface is polished to have a surface hardness of HRC65 or more and a center line average roughness Ra of 0.1 μm or less.

Japanese patent laid-open publication No. 2019-095044 discloses the following technique: when the angle between the fiber flow and the raceway surface in the rolling member is large, early breakage of the bearing due to the fact that the gap between the nonmetallic inclusion in the rolling member and the base material acts as an opening crack is suppressed. Specifically, in patent document 3, a polishing process is performed on a surface corresponding to the raceway surface of the rolling member. Thus, the track surface has an arithmetic average roughness Ra of 0.1 μm or less, a skewness Rsk < 0, and a compressive residual stress of 700MPa or more. This makes it possible to fill the gap between the nonmetallic inclusion and the base material exposed on the raceway surface, and to suppress the gap between the nonmetallic inclusion and the base material from functioning as an opening crack.

Compared with the polishing process using a general grinding stone, the polishing process has the technical problems of longer processing time and higher processing cost. In the machining using the grindstone, the same shape as the raceway surface is used, and the entire surface of the raceway surface is machined at the same time. On the other hand, in the polishing process, the contact range of the raceway surface with the tool tip is smaller than that in the grinding process. In the polishing process, a raceway ring (turning member) having a surface to be a raceway surface is rotated, and a tool pressed against the surface is moved in the axial direction, thereby performing the process. Therefore, the polishing process takes longer than the process using a grindstone. In addition, the tools used for polishing work are more expensive than grindstones. In the polishing process, the cost of the tool spent for each bearing product becomes high as compared with the process using a grindstone. The above-mentioned patent documents do not address such a problem of polishing and a method for solving the problem.

Disclosure of Invention

The present disclosure has been made in view of the above technical problems. The purpose of the present disclosure is to provide a bearing that can achieve a longer life with a lower budget.

The bearing according to the present disclosure includes an inner ring and an outer ring disposed on an outer peripheral side of the inner ring. The range of only any one of the raceway surface of the inner ring and the raceway surface of the outer ring is a first region having an arithmetic average roughness Ra of 0.1 μm or less, a skewness Rsk <0, and a compressive residual stress of 700MPa or more.

The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a schematic cross-sectional view showing the structure of a deep groove ball bearing.

Fig. 2 is a schematic diagram showing a first example of the first region, with a part of the deep groove ball bearing of fig. 1 enlarged.

Fig. 3 is a schematic view showing the contact area of the balls in the raceway surface of the inner ring.

Fig. 4 is a schematic enlarged cross-sectional view of a region IV surrounded by a broken line in fig. 2.

Fig. 5 is a schematic diagram of a second example of a portion of the deep groove ball bearing of fig. 1 enlarged and showing a first region.

Detailed Description

Next, this embodiment will be described with reference to the drawings. For convenience of explanation, the axial direction a, the radial direction R, and the circumferential direction C are introduced.

This embodiment is applied to a deep groove ball bearing, for example. Fig. 1 is a schematic cross-sectional view showing the structure of a deep groove ball bearing. Referring to fig. 1, the deep groove ball bearing 101 mainly includes an inner ring 1A, an outer ring 1B, a plurality of balls 4, and a cage 15.

The inner ring 1A is formed in an annular shape, and has an inner ring raceway surface 11 described later on an outer peripheral surface thereof. The outer ring 1B is formed in a ring shape, and has an outer ring raceway surface 12 on an inner peripheral surface. The outer ring 1B is disposed on the outer peripheral side of the inner ring 1A such that the inner ring raceway surface 11 faces the outer ring raceway surface 12.

The balls 4 are arranged at predetermined intervals on annular raceway surfaces along the circumferential direction of the inner ring 1A and the outer ring 1B by the cage 15, and are rotatably held on the raceways. The balls 4 have ball rolling surfaces 40, and the ball rolling surfaces 40 are in contact with the inner race track surface 11 and the outer race track surface 12. With this configuration, the inner ring 1A and the outer ring 1B of the deep groove ball bearing 101 can rotate relative to each other. The inner ring 1A, the outer ring 1B, and the balls 4 are made of, for example, SUJ2 of JIS standard. The holder 15 is made of, for example, SPCC of JIS standard.

Fig. 2 is a schematic diagram showing a first example of the first region, with a part of the deep groove ball bearing of fig. 1 enlarged. Referring to fig. 2, only a part of the inner race track surface 11 is in the first region 13. In the first region 13, the arithmetic average roughness Ra is 0.1 μm or less, the skewness Rsk < 0, and the compressive residual stress is 700MPa or more. The first region 13 may be a processing region subjected to polishing, for example, but may be a region in which the arithmetic average roughness Ra or the like satisfies the above-described numerical range by other methods. The first region 13 is formed in at least the central position of the contact region 14 of the inner race track surface 11 and the portion adjacent thereto in the axial direction a extending along the rotation axis of the inner race 1A and the outer race 1B (along the axis passing through the center line O (refer to fig. 1) of the centers of the inner race 1A and the outer race 1B). In particular, it is preferable that the center of the contact region 14 formed as the inner race track surface 11 is at the same position as the center of the first region 13. For example, when an axial load is applied, the positions of the balls 4 and the inner ring 1A and the outer ring 1B in the axial direction a may slightly deviate from each other. Even when some positional displacement occurs in this way, at least the first region 13 is a region including the center of the contact region 14 between the balls 4 and the raceway surfaces (the inner ring raceway surface 11 and the outer ring raceway surface 12) in the axial direction a.

In this case, the first region 13 is not formed at the end portions of one (left side in fig. 2) and the other (right side in fig. 2) of the inner ring raceway surface 11 in the axial direction a. On the other hand, it is preferable that the first region 13 is formed over the entire circumference of the inner race track surface 11 with respect to the circumferential direction C in which the plurality of balls 4 are arranged. That is, the first region 13 is preferably formed in the entire range in the circumferential direction C at the central portion of the inner ring raceway surface 11 in the axial direction a.

A portion of the inner ring raceway surface 11 in contact with the ball rolling surface 40 is seen in a plan view (i.e., a view line extending in the radial direction R) below the inner ring 1A in fig. 2 (different from the coordinate axes shown in fig. 2). The contact region 14, which is the portion where the inner race track surface 11 contacts the ball rolling surface 40, has an elliptical shape with a long diameter of 2a and a short diameter of 2 b. The elliptical shape of the contact region 14 is generally formed such that the long diameter 2a extends in the axial direction a and the short diameter 2b extends in the circumferential direction C.

For example, in the first region 13 subjected to polishing, the average value of compressive residual stress on the surface is 700MPa or more, and the average value of hardness on the surface is 60HRC or more. In the first region 13, the arithmetic average roughness Ra of the surface is 0.1 μm or less.

Fig. 3 is a schematic view showing the contact area of the balls in the raceway surface of the inner ring. Referring to fig. 2 and 3, at the central portion in the axial direction a, the balls 4 and the inner ring raceway surface 11 of the inner ring 1A are in contact with each other, and a plurality of elliptical-shaped contact areas 14 are generated at intervals in the circumferential direction C (the paper depth direction of fig. 2, i.e., the up-down direction of fig. 3). Since one contact area 14 is generated for one ball 4, the contact area 14 is generated in the number of balls 4. The contact surfaces of the balls 4 are pressed to different values from each other according to the load distribution in the deep groove ball bearing 101. Therefore, as shown in fig. 3, the long diameter 2a and the short diameter 2b of the contact region 14 of each ball 4 are different from each other. Specifically, the contact area 14 of the ball 4 having the largest contact surface pressure among the plurality of balls 4 has the largest value of the long diameter 2a and the short diameter 2 b. For example, as shown in fig. 3, the uppermost contact region 14 among the three arranged contact regions 14 is largest, and the contact region 14 at a position farther from the contact region 14 becomes smaller. In this way, the contact area 14 of the ball 4 having the largest contact surface pressure will be hereinafter referred to as "largest contact area 14".

The dimension of the first region 13 in the axial direction a is 120% to 150% of the major axis 2a of the largest contact region 14. However, in order to shorten the machining time, extend the life of the polishing tool, and reduce the machining cost, it is more preferable that the dimension of the first region 13 in the axial direction a is 100% or more and 120% or less of the largest long diameter 2a of the contact region 14. Further, it is more preferable that the dimension of the first region 13 in the axial direction a is 85% or more and 100% or less of the major axis 2a of the largest contact region 14.

Fig. 4 is a schematic enlarged cross-sectional view of a region IV surrounded by a broken line in fig. 2. Referring to fig. 4 and 3, the inner race track surface 11 includes a second region 13N other than the first region 13 in addition to the first region 13 satisfying the above numerical range such as the arithmetic average roughness Ra. The second region 13N does not satisfy the condition of the numerical range of the first region 13 on at least one of the above arithmetic average roughness Ra, the skewness Rsk, and the compressive residual stress of the first region 13. The second region 13N may be a non-processed region where polishing is not performed. The boundary between the first region 13 (e.g., a processed region) and the second region 13N (e.g., a non-processed region) is a boundary portion 13B (e.g., a processed boundary portion). That is, the inner race track surface 11 is constituted by the first region 13, the second region 13N, and the boundary portion 13B.

In the second region 13N, the arithmetic average roughness Ra is 0.1 μm or less. The average value of compressive residual stress on the surface of the second region 13N is 400MPa or less, and the average value of hardness on the surface is 58HRC or more. In order to make the second region 13N have such an arithmetic average roughness Ra, the second region 13N has an arithmetic average roughness Ra in the above-described numerical range by ultra-precision machining.

In the boundary portion 13B, the inner race track surface 11 forms a convex portion. The boundary portion 13B may have a certain width in a direction along the inner ring raceway surface 11 in the cross section (along the axial direction a and the radial direction R) of fig. 4. That is, the entire region protruding outward from the center line O of rotation with respect to the inner ring 1A by the convex portion in fig. 4 than the first region 13 and the second region 13N is referred to as a boundary portion 13B. Preferably, the height H of the protrusion protruding in the direction perpendicular to the tangent of the inner race track surface 11 is 0.4 μm or less. The direction perpendicular to the tangent line of the inner race track surface 11 is a direction outward from the inner race track surface 11 with respect to the center line O in which the inner race 1A rotates. The protruding portion protrudes from the inner race track surface 11 perpendicularly to the tangential line thereof toward the outer side of the rotation of the inner race 1A. More preferably, the height of the protruding portion is 0.4 μm or less. In addition, the convex portion of the boundary portion 13B of fig. 4 is inevitably formed due to, for example, polishing processing.

Referring again to fig. 2, the arrow in the radial direction R downward inside the ball 4 indicates the surface pressure applied from the ball rolling surface 40 to the inner race track surface 11 in order to bring the ball 4 into contact with the inner race track surface 11. The maximum arrow in the center of fig. 2 indicates the maximum contact surface pressure P _max, which is the maximum surface pressure for achieving the contact. In particular, when the arithmetic average roughness Ra of the second region 13N is 0.1 μm or less and the height H is 0.4 μm or less, the first region 13 may be a region (polished) to which only 50% or more of the maximum contact surface pressure P _max between the inner race surface 11 and the ball rolling surface 40 is applied to the inner race surface 11.

Fig. 5 is a schematic diagram of a second example of a portion of the deep groove ball bearing of fig. 1 enlarged and showing a first region. Referring to fig. 5, the outer ring raceway surface 12 of the outer ring 1B is different from that of fig. 2 in that it has a first region 13. In this case, the first region 13 may be polished. In this way, the first region 13 may be a range of only a part of the outer ring raceway surface 12 of the outer ring 1B.

The deep groove ball bearing 101 (see fig. 1) may have the features of both fig. 2 and 5. That is, the deep groove ball bearing 101 may have only a partial range of both the inner ring raceway surface 11 and the outer ring raceway surface 12 as the first region 13.

(Method for measuring parameters)

The measurement method of each parameter is as follows. The arithmetic average roughness Ra is a value calculated according to jis b0601, and is measured using a contact or non-contact surface roughness meter or the like. The compressive residual stress can be measured by cutting a part of the surface of the bearing member, then electropolishing the surface, and measuring the surface using an X-ray diffraction apparatus. The hardness of the raceway surface can be measured by a generally known rockwell hardness test. That is, the hardness of the raceway surface is calculated by measuring the pressing depth of the indenter in a state where a load is applied.

(Effects of action)

The bearing (deep groove ball bearing 101) of the present embodiment includes an inner ring 1A and an outer ring 1B disposed on the outer peripheral side of the inner ring 1A. Only one of the raceway surface of the inner ring 1A (inner ring raceway surface 11) and the raceway surface of the outer ring 1B (outer ring raceway surface 12) is in the range of a first region 13 having an arithmetic average roughness Ra of 0.1 μm or less, a skew Rsk < 0, and a compressive residual stress of 700MPa or more.

The polishing process is performed to a limited range in which only the necessity of the process is particularly high in the raceway surfaces of the inner ring 1A and the outer ring 1B of the bearing. Therefore, compared with the case where the entire raceway surface is polished, the processing time can be shortened, and the effect of prolonging the life of the bearing, which is the minimum achieved by the polishing, can be obtained. Further, the amount of the polishing tool used is smaller than that in the case of machining the entire raceway surface, and therefore wear and damage of the tool can be suppressed. Further, only a partial range of both the raceway surface of the inner ring and the raceway surface of the outer ring may be set as the first region 13. This can further enhance the above-described effects.

The bearing may further include rolling elements (balls 4) arranged on the raceway surface, and the first region 13 may have a size of 120% to 150% of the largest contact region 14 where the raceway surface (inner raceway surface 11, outer raceway surface 12) and the rolling surface (ball rolling surface 40) of the rolling elements contact each other in the axial direction a along which the rotational axes of the inner ring 1A and the outer ring 1B extend. In the case where there is a possibility that a large deviation may occur in the position and the range of the contact region 14 between the raceway surface and the rolling surface due to an impact load, vibration, or the like during the operation of the bearing, it is preferable to determine the range of the first region 13 in the above-described manner. In the case where the contact region 14 is greatly deviated from the intended region and sufficiently contacts the outside, if the contact portion is not the first region 13, damage and a low lifetime may be caused, and therefore, the first region 13 is preferably set to be wide from the viewpoint of safety. Thus, for example, if the first region 13 is 150% of the maximum long diameter 2a of the contact region 14, the range of the first region 13 can be reduced as compared with the case where the entire track surface is polished.

The bearing may further include rolling elements (balls 4) arranged on raceway surfaces, and the first region 13 may have a size of 100% to 120% of the largest contact region 14 where the raceway surfaces (inner raceway surface 11, outer raceway surface 12) are in contact with the rolling surfaces (ball rolling surface 40) of the rolling elements in the axial direction a along which the rotational axes of the inner ring 1A and the outer ring 1B extend. Even if the deviation of the position and the range of the contact area 14 between the raceway surface and the rotation surface during the operation of the bearing is small compared with the case described in the previous paragraph, there is a possibility that the deviation of the position and the range of the contact area 14 between the raceway surface and the rotation surface may occur due to the accuracy of the size and the shape of the bearing, the deviation of the clearance, and the like. In this case, by setting the size of the first region 13 to be large as described above, even if the position and the range of the contact region 14 between the raceway surface and the rolling surface are deviated and are located significantly outward from the assumed position, damage and short lifetime can be suppressed by making the raceway surface at this position the first region 13. For example, if the first region 13 is 120% of the length diameter 2a of the largest contact region 14, the range of the first region 13 can be reduced as compared with the case where the entire track surface is polished.

The arithmetic average roughness Ra of the second region 13N excluding the first region 13 on the raceway surface of the bearing is 0.1 μm or less. In the boundary portion 13B that is a boundary between the first region 13 and the second region 13N, the height of the convex portion in the direction perpendicular to the tangent line of the track surface is 0.4 μm or less. As described above, this may be achieved when the size of the first region 13 is 120% or more and 150% or less of the longer diameter 2a of the largest contact region 14 where the raceway surface contacts the rolling surface of the rolling element, and when the size of the first region 13 is 100% or more and 120% or less of the longer diameter 2a of the largest contact region 14 where the raceway surface contacts the rolling surface of the rolling element.

The bearing in which the arithmetic average roughness Ra of the second region 13N is 0.1 μm or less and the height of the convex portion in the boundary portion 13B is 0.4 μm or less further includes rolling elements (balls 4) arranged on the raceway surface, and the first region 13 may have a size of 85% or more and 100% or less of the largest contact region 14 in which the raceway surface (inner race raceway surface 11, outer race raceway surface 12) and the rolling surface (ball rolling surface 40) of the rolling elements contact each other in the axial direction a in which the rotation axes of the inner race 1A and the outer race 1B extend.

In this way, as in the above, even when the contact area 14 is out of the first area 13 due to the use condition other than the assumption, the bearing can be prevented from having an extremely short life. That is, if the arithmetic average roughness Ra of the second region 13N is 0.1 μm or less, that is, the same level as the arithmetic average roughness Ra of the first region 13, the load applied to the ball rolling surface 40 is the same level as the first region 13 even in the second region 13N. Therefore, even if the ball rolling surface 40 is in contact with the second region 13N and a large surface pressure is applied, damage to the ball rolling surface 40 caused thereby can be suppressed and contact of the ball rolling surface 40 can be allowed.

In addition, even if the ball rolling surface 40 is in contact with the boundary portion 13B and a large surface pressure is applied, the height H of the convex portion of the boundary portion 13B is low, so that the possibility of damage to the ball rolling surface 40 by the boundary portion 13B can be reduced. If the dimension in the axial direction a of the first region 13 is 100% or less of the dimension of the contact region 14, the contact region 14 passes through the boundary (boundary portion 13B) of the first region 13 and the second region 13N and enters the second region 13N. Therefore, by reducing the protrusion height H of the boundary portion 13B, damage to the ball rolling surface 40 can be suppressed.

In addition, even if the first region 13 and the second region 13N have no significant difference in the arithmetic average roughness Ra, the two regions can be identified as long as there is a significant difference in the hardness and the residual compressive stress. Even when there is no difference in the average value of the hardness and the residual compressive stress of the first region 13 and the second region 13N, since the boundary portion 13B is provided between the first region 13 and the second region 13N, at least the first region 13 and the second region 13N can be identified as marks. In addition, particularly in the case where the first region 13 is a processing region to which polishing processing is performed, since polishing processing is performed to grind the roughness of a surface having a certain degree of roughness, characteristic fluctuations having the same period as the processing pitch are generated. Thereby, the first region 13 and the second region 13N can also be identified.

In the above-described case, if the dimension of the first region 13 in the axial direction a is further narrowed and is set to be equal to or smaller than the long diameter 2a of the largest contact region 14 in the axial direction a, the processing time can be further shortened. Specifically, for example, if the dimensions of the first region 13 and the contact region 14 in the axial direction a are made the same, the range of the first region 13 can be reduced as compared with the case where the entire track surface is polished.

The bearing may further include rolling elements (balls 4) disposed on the raceway surface, and even when the first region 13 has a size equal to or smaller than the long diameter 2a of the contact region 14, the first region 13 may be a region to which only a contact surface pressure of 50% or more of the maximum contact surface pressure P _max between the raceway surface and the rolling surface is applied. In this case, the area of the contact area 14 having a size of about 87% of the size becomes the first area 13, and the range of the first area 13 can be reduced as compared with the case where the entire track surface is polished.

In practice, only the region to which 50% or more of the maximum contact surface pressure P _max is applied is a region in which the bearing life may be shortened without performing the polishing process. This is because applying a larger face pressure increases the likelihood of injury. Therefore, in the case of performing the operation under the condition of high rotation accuracy in which the positional deviation of the contact region 14 is not easily caused, it is preferable to set the region where the maximum contact surface pressure P _max is applied to be 50% or more, which may cause the low lifetime, as the first region 13, and further narrow the first region 13. If only the portion where the contact surface pressure of the raceway surface and the rolling surface is high is polished, the effects of reducing the processing time and prolonging the service life of the tool can be obtained, and the effect of prolonging the service life of the bearing can be sufficiently obtained.

As described above, the dimension of the first region 13 in the axial direction a with respect to the contact region 14 can be calculated from the shape of the bearing, the dimensional accuracy, and the operating condition of the bearing. In the case of the shape, dimensional accuracy, and operating conditions of the bearing that easily cause the positional displacement of the contact region 14, it is preferable to make the dimension of the first region 13 in the axial direction a longer relative to the dimension of the contact region 14 in the axial direction a. In this case, due to the positional deviation, there is a possibility that the contact region 14 is generated at a position greatly separated in the axial direction from the contact position assumed when designing fig. 2. Therefore, even if the contact region 14 is formed at a position greatly separated in the axial direction from the contact position assumed at the time of design, the first region 13 is preferably provided in a larger range in the axial direction a from the viewpoint of preventing damage to the member. Conversely, in the case of the shape, dimensional accuracy, and operating conditions of the bearing in which the positional deviation of the contact region 14 is less likely to occur, it is sufficient that the contact region 14 is able to be within the shorter range even if the dimension of the first region 13 in the axial direction a is made shorter than the dimension of the contact region 14 in the axial direction a. By narrowing the first region 13, the machining time can be shortened, and the lifetime of the polishing tool can be increased, so that the machining cost can be reduced.

Example 1

The case where the maximum contact surface pressure P _max in fig. 2 and 5, that is, 3.00GPa acts on the outer ring raceway surface 12 of the deep groove ball bearing 101 of fig. 1 of the type called 6206 will be described as an example. In this case, the largest contact area 14 (see fig. 2 and 5) is in the shape of an ellipse with a major axis radius a=1.47 mm, a minor axis radius b=0.21 mm (minor axis diameter 2b=0.42 mm). Therefore, the diameter of the major axis of the contact region 14 is 2a=2.94 mm, which corresponds to about 40% of the length W (about 7.5 mm) of the inner ring raceway surface 11 and the outer ring raceway surface 12 in the axial direction a. When the contact region 14 having the dimension a in the axial direction a of 120% of the first region 13 is set in consideration of the accuracy of the shape and dimension of the bearing and the variation in the gap, the dimension L (see fig. 2 and 5) of the polished first region 13 in the axial direction a is 3.5mm. L=3.5 mm corresponds to about 50% of the lengths of the inner ring raceway surface 11 and the outer ring raceway surface 12 in the axial direction a.

Example 2

In the case of using the deep groove ball bearing 101 similar to that of example 1, if the size of the first region 13 is 150% of the long diameter 2a of the largest contact region 14, the range of the first region 13 can be reduced by about 40% as compared with the case of polishing the entire raceway surface. In addition, compared with the case of polishing the entire track surface, the processing time can be reduced by about 40%, and the life of the polishing tool can be increased by 1.7 times.

If the size of the first region 13 is 120% of the long diameter 2a of the largest contact region 14, the range of the first region 13 can be reduced by about 50% as compared with the case where the entire track surface is polished. In addition, compared with the case of polishing the entire track surface, the processing time can be reduced by about 50%, and the life of the polishing tool can be increased by 2 times.

If the dimensions of the first region 13 and the contact region 14 in the axial direction a are made the same, the range of the first region 13 can be reduced by about 60% as compared with the case where the entire track surface is polished. In addition, compared with the case of polishing the entire track surface, the processing time can be reduced by about 60%, and the life of the polishing tool can be increased by 2.5 times.

When 6206 is used and only the region on which 50% or more of the maximum contact surface pressure P _max acts is set as the first region 13, the dimension of the first region 13 in the axial direction a is about 2.55mm. At this time, the size of the first region 13 is about 87% of the major diameter 2a of the largest contact region 14. Thus, the range of the first region 13 can be reduced by about 80% as compared with the case where the entire track surface is polished. In addition, compared with the case of polishing the entire track surface, the processing time can be reduced by about 80%, and the life of the polishing tool can be increased by 4.3 times.

The features described in the examples included in the above embodiments may be combined and applied as appropriate within the scope of technical contradiction.

It should be understood that although the embodiments of the present invention have been described, the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims (7)

1. A bearing, comprising:

An inner ring; and

An outer ring disposed on an outer peripheral side of the inner ring,

The range of only any one of the raceway surface of the inner ring and the raceway surface of the outer ring is a first region having an arithmetic average roughness Ra of 0.1 [ mu ] m or less, a skewness Rsk < 0, and a compressive residual stress of 700MPa or more.

2. A bearing according to claim 1, wherein,

Only a portion of the raceway surface of the inner ring and the raceway surface of the outer ring are in the first region.

3. A bearing according to claim 1 or 2, wherein,

The rolling element is disposed on the raceway surface, and the first region has a dimension in an axial direction along which the rotational axes of the inner ring and the outer ring extend, the dimension being 120% or more and 150% or less of a major diameter of a largest contact region where the raceway surface contacts the rolling surface of the rolling element.

4. A bearing according to claim 1 or 2, wherein,

Further comprising rolling elements arranged on the raceway surface,

The first region has a dimension of 100% to 120% of a major diameter of a largest contact region where the raceway surface contacts the rolling surface of the rolling element in an axial direction along which the rotation axes of the inner ring and the outer ring extend.

5. A bearing according to claim 1 or 2, wherein,

The arithmetic average roughness Ra of the second region excluding the first region on the track surface is 0.1 μm or less,

The height of the protruding portion in the direction perpendicular to the tangent line of the track surface in the boundary between the first region and the second region is 0.4 [ mu ] m or less.

6. The bearing of claim 5, wherein the bearing comprises a plurality of bearings,

Further comprising rolling elements arranged on the raceway surface,

The first region has a dimension of 85% to 100% of a major diameter of a largest contact region where the raceway surface contacts the rolling surface of the rolling element in an axial direction along which the rotation axes of the inner ring and the outer ring extend.

7. The bearing of claim 6, wherein the bearing comprises a plurality of bearings,

Further comprising rolling elements arranged on the raceway surface,

The first region is a region to which only a contact surface pressure of 50% or more of a maximum contact surface pressure of the raceway surface and the rolling surface of the rolling element is applied.