Rolling bearings

Abstract

A rolling bearing having a long life is provided by suppressing the occurrence of surface-originated flaking on at least one of a first raceway surface, a second raceway surface, and a rolling surface. [Solution] The rolling bearing 1 comprises an inner ring 3, an outer ring 6, and a plurality of rolling elements 10. The inner ring 3 has a first raceway surface 4. The outer ring 6 has a second raceway surface 7. Each of the plurality of rolling elements 10 has a rolling surface 11. A first von Mises stress of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is smaller than the yield stress of a material constituting at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11.

Description

[Technical Field]

[0001] The present invention relates to a rolling bearing. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2011-7234 (Patent Document 1) discloses a rolling bearing including an inner ring having a first raceway surface, an outer ring having a second raceway surface, and a rolling element having a rolling surface and arranged between the inner ring and the outer ring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-7234 Summary of the Invention [Problem to be solved by the invention]

[0004] During use of a rolling bearing, contact stresses between the inner ring and the rolling elements continue to act on the inner ring and the rolling elements, and contact stresses between the outer ring and the rolling elements continue to act on the outer ring and the rolling elements. These contact stresses cause fatigue cracks to occur in at least one of the first raceway surface, the second raceway surface, and the rolling surface. When the rolling bearing is used for an extended period of time, the fatigue cracks propagate, causing flaking of at least one of the first raceway surface, the second raceway surface, and the rolling surface. This flaking is called surface-initiated flaking. An object of the present invention is to provide a rolling bearing with a long life by suppressing the occurrence of surface-initiated flaking in at least one of the first raceway surface, the second raceway surface, and the rolling surface. [Means for solving the problem]

[0005] The rolling bearing of the present invention comprises: The rolling bearing of the present invention is used under lean lubrication conditions.The bearing comprises an inner ring, an outer ring disposed on the outer periphery of the inner ring, and a plurality of rolling elements disposed between the inner ring and the outer ring. The inner ring has a first raceway surface. The outer ring has a second raceway surface opposing the first raceway surface. Each of the plurality of rolling elements has a rolling surface that contacts the first raceway surface and the second raceway surface. The first raceway surface is the surface of the inner ring with which the rolling elements contact. The second raceway surface is the surface of the outer ring with which the rolling elements contact. The rolling surface is the surface of the rolling elements that contact the first raceway surface and the second raceway surface. The first von Mises stress in at least one of the first raceway surface, the second raceway surface, and the rolling surface is smaller than the yield stress of a material that constitutes at least one of the first raceway surface, the second raceway surface, and the rolling surface. The first von Mises stress in at least one of the first raceway surface, the second raceway surface, and the rolling surface is smaller than the second von Mises stress in at least one of the inner ring, the outer ring, and the rolling elements having at least one of the first raceway surface, the second raceway surface, and the rolling surface, and the second von Mises stress is the maximum value of the von Mises stress in at least one of the inner ring, the outer ring, and the rolling elements. [Effects of the Invention]

[0006] According to the rolling bearing of the present invention, the occurrence of surface-initiated flaking on at least one of the first raceway surface, the second raceway surface, and the rolling surface can be suppressed, and a rolling bearing having a long life can be provided. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic, partially cutaway perspective view of a rolling bearing according to a first embodiment of the present invention. [Figure 2] 1 is a schematic, partially enlarged cross-sectional view of a rolling bearing according to a first embodiment of the present invention. [Figure 3] 1 is a graph showing the distribution of residual compressive stress imparted to the rolling bearings of Example 1 of the present invention and Comparative Examples 2 and 3. FIG. [Figure 4] FIG. 1 is a graph showing the distribution of equivalent stress acting on at least one of the inner ring, outer ring, and each rolling element in the thickness direction of the inner ring, outer ring, and at least one of the rolling elements of the rolling bearings of Example 1 of the present invention and Comparative Examples 1 to 3. [Figure 5] FIG. 10 is a graph showing the distribution of residual compressive stress imparted to the rolling bearings of Example 2 of the present invention and Comparative Examples 4 and 5. [Figure 6] FIG. 10 is a graph showing the distribution of equivalent stress acting on at least one of the inner ring, outer ring, and each rolling element in the thickness direction of the inner ring, outer ring, and at least one of the rolling elements of the rolling bearings of Example 2 of the present invention, Comparative Example 1, Comparative Example 4, and Comparative Example 5. [Figure 7] FIG. 1 is a graph showing the effect of the anisotropy of the residual compressive stress imparted to at least one of the first raceway surface, the second raceway surface, and the rolling surface of the rolling bearing according to embodiment 1 of the present invention on the relationship between the first residual compressive stress and the ratio of the equivalent stress acting on at least one of the inner ring, the outer ring, and each rolling element of the rolling bearing according to embodiment 1 of the present invention. [Figure 8] FIG. 1 is a graph showing the distribution of residual compressive stress in the thickness direction of at least one of the inner ring, the outer ring, and each rolling element, which is imparted to at least one of the first raceway surface, the second raceway surface, and the rolling surface by rolling each rolling element against the inner ring and the outer ring before use of the rolling bearing according to embodiment 1 of the present invention. [Figure 9] FIG. 4 is a schematic plan view of a rolling bearing according to a second embodiment of the present invention. [Figure 10] 10 is a schematic, partially enlarged cross-sectional view of a rolling bearing according to a second embodiment of the present invention, taken along the cross-sectional line XX shown in FIG. 9. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0009] (Embodiment 1) A rolling bearing 1 according to a first embodiment will be described with reference to Figures 1 to 8. As shown in Figures 1 and 2, the rolling bearing 1 of this embodiment includes an inner ring 3, an outer ring 6, and a plurality of rolling elements 10. The inner ring 3, the outer ring 6, and the plurality of rolling elements 10 are made of steel such as bearing steel. The steel that constitutes the inner ring 3, the outer ring 6, and the plurality of rolling elements 10 may be high-chromium bearing steel as specified in the JIS standard (JIS4805:2008). The steel that constitutes the inner ring 3, the outer ring 6, and the plurality of rolling elements 10 may be SUJ2 steel as specified in the JIS standard.

[0010] The inner ring 3 has a first raceway surface 4. The outer ring 6 has a second raceway surface 7 opposing the first raceway surface 4. The outer ring 6 is arranged on the outer peripheral side of the inner ring 3. A plurality of rolling elements 10 are arranged between the inner ring 3 and the outer ring 6. Each of the plurality of rolling elements 10 has a rolling surface 11 that contacts the first raceway surface 4 and the second raceway surface 7. The plurality of rolling elements 10 may be a plurality of rollers. The rolling bearing 1 may be a roller bearing. The rolling bearing 1 may further include a cage 15 that holds the plurality of rolling elements 10.

[0011] The outer ring 6 can rotate about the shaft 2 relative to the inner ring 3 via a plurality of rolling elements 10. While the outer ring 6 rotates about the shaft 2 relative to the inner ring 3, lubricating oil may be supplied to the rolling bearing 1. The rolling bearing 1 of this embodiment may be used under lean lubrication conditions (low Λ conditions), although this is not particularly limited. Lean lubrication conditions (low Λ conditions) are conditions under which the oil film parameter Λ defined by equation (1) is 1 or less.

[0012]

number

[0013] In equation (1), h min represents the minimum oil film thickness, and R q1 represents the root mean square roughness of the first raceway surface 4 or the second raceway surface 7, and R q2 represents the root mean square roughness of the rolling surface 11.

[0014] A first radius of curvature in the axial direction (y direction) of at least one rolling bearing 1 of the inner ring 3, the outer ring 6, and each rolling element 10 is different from a second radius of curvature in the circumferential direction (x direction) of at least one rolling bearing 1 of the inner ring 3, the outer ring 6, and each rolling element 10. In this embodiment, the first radius of curvature in the axial direction (y direction) of the inner ring 3 is different from the second radius of curvature in the circumferential direction (x direction) of the inner ring 3. The first radius of curvature in the axial direction (y direction) of the outer ring 6 is different from the second radius of curvature in the circumferential direction (x direction) of the outer ring 6. The first radius of curvature in the axial direction (y direction) of each rolling element 10 is different from the second radius of curvature in the circumferential direction (x direction) of each rolling element 10. Specifically, the first radius of curvature in the axial direction (y direction) of the inner ring 3 may be larger than the second radius of curvature in the circumferential direction (x direction) of the inner ring 3. The first radius of curvature in the axial direction (y direction) of the outer ring 6 may be larger than the second radius of curvature in the circumferential direction (x direction) of the outer ring 6. The first radius of curvature in the axial direction (y direction) of each rolling element 10 may be larger than the second radius of curvature in the circumferential direction (x direction) of each rolling element 10.

[0015] A first residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3 and the outer ring 6 of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 y0 is a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3 and the outer ring 6 of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. x0 Therefore, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is larger than e0 The first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 decreases. e0 is smaller than the yield stress of the material constituting at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. This can suppress the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. In this specification, equivalent stress means Mises stress.

[0016] On the other hand, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0is greater than the yield stress of the material that constitutes at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11, plastic deformation occurs in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. A fatigue crack occurs in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11, causing surface-initiated spalling.

[0017] Hereinafter, with reference to Examples 1 and 2 and Comparative Examples 1 to 5, the first residual compressive stress σ in at least one axial direction (y direction) of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 will be calculated. y0 a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11; x0 By making the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 larger than e0 indicates that decreases.

[0018] The contact between the inner ring 3 and each rolling element 10, and the contact between the outer ring 6 and each rolling element 10, can be considered to be Hertzian contact. The contact surfaces between the inner ring 3 and each rolling element 10, and the contact surfaces between the outer ring 6 and each rolling element 10, can be considered to be elliptical contact surfaces with a major radius a and a minor radius b. The major radius a refers to the radius of the contact ellipse in the major axis direction, and the minor radius b refers to the radius of the contact ellipse in the minor axis direction. The major axis direction of the contact ellipse is the axial direction of the rolling bearing 1 (y direction), and the minor axis direction of the contact ellipse is the circumferential direction of the rolling bearing 1 (x direction).

[0019] In Examples 1 and 2 and Comparative Examples 1 to 5, Hertz's theory was used to simulate the equivalent stress occurring in at least one of the inner ring 3, outer ring 6, and rolling elements 10, each of which has at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. Specifically, the maximum contact pressure P acting between the rolling surface 11 and at least one of the first raceway surface 4 and the second raceway surface 7 was calculated. maxThe equivalent stress of at least one of the inner ring 3, the outer ring 6 and each rolling element 10 was simulated when the stress was 3.0 GPa, the minor radius b was 1 mm, and at least one of the inner ring 3, the outer ring 6 and each rolling element 10 had the residual compressive stress distribution shown in Tables 1 and 2.

[0020] As shown in Table 1, in Example 1, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 x 3 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Example 1, the residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 y has a distribution B shown in Fig. 3 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. The negative sign on the vertical axis in Fig. 3 means that the stress applied to at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is a compressive stress.

[0021] [Table 1]

[0022] In Example 1, an anisotropic residual compressive stress is applied to at least one of the inner ring 3, the outer ring 6, and each rolling element 10. Specifically, a first residual compressive stress σ in the axial direction (y direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is applied. y0 is a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. x0 In this specification, a large compressive stress means that the absolute value of the compressive stress is large.

[0023] Furthermore, as shown in distributions A and B in FIG. 3, in the surface layer region of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11, the residual compressive stress σ in the axial direction (y direction) y is the residual compressive stress σ in the circumferential direction (x direction) xThe residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is larger than y may be maximum on at least one surface of the inner ring 3, outer ring 6 and each rolling element 10 (i.e., at least one of the first raceway surface 4, the second raceway surface 7 and the rolling surface 11) in the thickness direction of at least one of the inner ring 3, outer ring 6 and each rolling element 10.

[0024] In contrast, as shown in Table 1, in Comparative Example 1, no residual compressive stress is applied to the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Example 2, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is x and axial (y-direction) residual compressive stress σ y 3 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Example 3, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 x and axial (y-direction) residual compressive stress σ y 3 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Examples 2 and 3, isotropic residual compressive stress σ x ,σ y is granted.

[0025] As shown in Figure 4, the equivalent stress in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10 in Example 1 is lower than the equivalent stress in the surface layer region of Comparative Examples 2 and 3. The residual compressive stress imparted to at least one of the inner ring 3, outer ring 6, and each rolling element 10 reduces the equivalent stress acting on at least one of the inner ring 3, outer ring 6, and each rolling element 10 in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10. In this specification, the surface layer region refers to the region from the surface of at least one of the inner ring 3, outer ring 6, and each rolling element 10 (i.e., at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11) to the depth where the equivalent stress is minimal. In Figure 4, the horizontal axis indicates the position z / b in the thickness direction of at least one of the inner ring 3, outer ring 6, and each rolling element 10, normalized by the minor radius b of the osculating ellipse. The surface region may be, for example, a region where z / b is 0.2 or less. The surface region may be, for example, a region extending from the surface of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 (i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11) to a depth of 50 μm.

[0026] At least one surface layer region of the inner ring 3, the outer ring 6, and each rolling element 10 includes at least one surface of the inner ring 3, the outer ring 6, and each rolling element 10, i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. The first equivalent stress σ of Example 1 in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0 is lower than the first equivalent stress of Comparative Examples 2 and 3 in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. In Figure 4, the position z / b = 0 represents at least one surface of the inner ring 3, the outer ring 6, and each rolling element 10, i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11.

[0027] In the surface layer region, the equivalent stress of Example 1 and the first equivalent stress σ e0are lower than the equivalent stress and the first equivalent stress in the surface layer region of Comparative Example 2 and Comparative Example 3, respectively. The reason why the first radius of curvature of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 in the axial direction (y direction) is different from the second radius of curvature of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 in the circumferential direction (x direction) is different. Therefore, the contact stress between the inner ring 3 and each rolling element 10 in the axial direction (y direction) is different from the contact stress between the inner ring 3 and each rolling element 10 in the circumferential direction (x direction). The contact stress between the outer ring 6 and each rolling element 10 in the axial direction (y direction) is different from the contact stress between the outer ring 6 and each rolling element 10 in the circumferential direction (x direction). The anisotropic residual compressive stress in Example 1 can more effectively deal with the anisotropic contact stress between the inner ring 3 and each rolling element 10 and the anisotropic contact stress between the outer ring 6 and each rolling element 10 than the isotropic residual compressive stress in Comparative Examples 2 and 3.

[0028] In this way, the anisotropic residual compressive stress imparted to at least one of the inner ring 3, outer ring 6, and each rolling element 10 reduces the equivalent stress acting on at least one of the inner ring 3, outer ring 6, and each rolling element 10 in a surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10, including at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11. The equivalent stress in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10 becomes smaller than the yield stress of the material constituting at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11. Therefore, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11 can be suppressed.

[0029] As shown in Table 2, in Example 2, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 x 5 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Example 2, the residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 has a distribution C shown in FIG. yhas a distribution D shown in Fig. 5 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. The negative sign on the vertical axis in Fig. 5 means that the stress applied to at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is a compressive stress.

[0030] [Table 2]

[0031] In Example 2, an anisotropic residual compressive stress is applied to at least one of the inner ring 3, the outer ring 6, and each rolling element 10. Specifically, a first residual compressive stress σ in the axial direction (y direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is applied. y0 is a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. x0 is greater than.

[0032] Furthermore, as shown in distributions C and D in FIG. 5, the residual compressive stress σ in the axial direction (y direction) is small in the surface layer region of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. y is the residual compressive stress σ in the circumferential direction (x direction) x The residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is larger than y may be maximum inside at least one of the inner ring 3, outer ring 6 and each rolling element 10 in the thickness direction of at least one of the inner ring 3, outer ring 6 and each rolling element 10.

[0033] Specifically, the residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 y The position z / b in the thickness direction at which the residual compressive stress σ is maximized is greater than 0, and may be greater than 0.03, or may be greater than 0.05. yThe position z / b in the thickness direction at which is maximized may be smaller than 1.00, may be smaller than 0.90, or may be smaller than 0.80.

[0034] In contrast, as shown in Table 2, in Comparative Example 1, no residual compressive stress is applied to the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Example 4, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 is x and axial (y-direction) residual compressive stress σ y 5 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Example 5, the residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 x and axial (y-direction) residual compressive stress σ y 5 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In Comparative Examples 4 and 5, isotropic residual compressive stress σ x ,σ y is granted.

[0035] 6 , the equivalent stress in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10 in Example 2 is lower than the equivalent stress in the surface layer region of Comparative Examples 4 and 5. The residual compressive stress imparted to at least one of the inner ring 3, outer ring 6, and each rolling element 10 reduces the equivalent stress acting on at least one of the inner ring 3, outer ring 6, and each rolling element 10 in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10.

[0036] At least one surface layer region of the inner ring 3, the outer ring 6, and each rolling element 10 includes at least one surface of the inner ring 3, the outer ring 6, and each rolling element 10, i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. The first equivalent stress σ of Example 2 in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0is lower than the first equivalent stress of Comparative Examples 4 and 5 in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. In Figure 4, the position z / b = 0 represents at least one surface of the inner ring 3, the outer ring 6, and each rolling element 10, i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11.

[0037] In the surface layer region, the equivalent stress of Example 2 and the first equivalent stress σ e0 are lower than the equivalent stress and the first equivalent stress in Comparative Example 4 and Comparative Example 5, respectively. The reason why the first radius of curvature of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 in the axial direction (y direction) is different from the second radius of curvature of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 in the circumferential direction (x direction) is different. Therefore, the contact stress between the inner ring 3 and each rolling element 10 in the axial direction (y direction) is different from the contact stress between the inner ring 3 and each rolling element 10 in the circumferential direction (x direction). The contact stress between the outer ring 6 and each rolling element 10 in the axial direction (y direction) is different from the contact stress between the outer ring 6 and each rolling element 10 in the circumferential direction (x direction). The anisotropic residual compressive stress in Example 2 can more effectively deal with the anisotropic contact stress between the inner ring 3 and each rolling element 10 and the anisotropic contact stress between the outer ring 6 and each rolling element 10 than the isotropic residual compressive stress in Comparative Examples 4 and 5.

[0038] In this way, the anisotropic residual compressive stress imparted to at least one of the inner ring 3, outer ring 6, and each rolling element 10 reduces the equivalent stress acting on at least one of the inner ring 3, outer ring 6, and each rolling element 10 in a surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10, including at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11. The equivalent stress in the surface layer region of at least one of the inner ring 3, outer ring 6, and each rolling element 10 becomes smaller than the yield stress of the material constituting at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11. Therefore, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, second raceway surface 7, and rolling surface 11 can be suppressed.

[0039] As shown in Examples 1 and 2 in FIGS. 4 and 6, the first equivalent stress σ e0 is a second equivalent stress σ of at least one of the inner ring 3, the outer ring 6, and each rolling element 10, which has at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. e2 The second equivalent stress σ e2 is the maximum value of the equivalent stress inside at least one of the inner ring 3, the outer ring 6, and each rolling element 10. In other words, the equivalent stress ratio n shown in FIG. 7 may be less than 1. In this specification, the equivalent stress ratio n is defined as the ratio of the second equivalent stress σ e2 The first equivalent stress σ e0 is given by the ratio n (n=σ e0 / σ e2 ).

[0040] A first residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3 and the outer ring 6 of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 y0 is a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3 and the outer ring 6 of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. x0 Therefore, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is larger than e0 may decrease, and the ratio n of the equivalent stresses may become less than 1. The first equivalent stress σ e0 is smaller than the yield stress of the material constituting at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. The occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed.

[0041] The maximum contact pressure P acting between each rolling element 10 and at least one of the inner ring 3 and the outer ring 6 max First residual compressive stress σ y0The ratio may be -0.7 or more, -0.6 or more, or -0.5 or more. Therefore, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0 is a second equivalent stress σ of at least one of the inner ring 3, the outer ring 6, and each rolling element 10, which has at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. e2 The maximum contact pressure P between each rolling element 10 and at least one of the inner ring 3 and the outer ring 6 can be made smaller than max The first residual compressive stress σ y0 The ratio may be less than 0.0, may be equal to or less than −0.1, or may be equal to or less than −0.2.

[0042] The anisotropy of the residual compressive stress α is greater than 1. The anisotropy of the residual compressive stress α is the second residual compressive stress σ x0 The first residual compressive stress σ y0 is given by the ratio (α=σ y0 / σ x0 The anisotropy α of the residual compressive stress may be 1.3 or more, 1.5 or more, 1.75 or more, or 2.0 or more. The anisotropy α of the residual compressive stress is not particularly limited, but may be 20 or less, 10 or less, or 5.0 or less.

[0043] As shown in FIG. 7, as the anisotropy α of the residual compressive stress becomes larger than 1, the first residual compressive stress σ y0 The negative sign on the horizontal axis in FIG. 7 means that the stress applied to at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 is compressive stress. For example, when the anisotropy α of the residual compressive stress is equal to 1.3, the first residual compressive stress σ of 1650 MPa or less is y0 is the first equivalent stress σ e0 The second equivalent stress σ e2 Therefore, by making the anisotropy α of the residual compressive stress larger than 1, various first residual compressive stresses σ y0In more types of rolling bearings 1 having the above, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0 In more types of rolling bearings 1, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed.

[0044] In the surface layer region, a first residual compressive stress σ in the axial direction (y direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 y0 a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11; x0 Two methods are mainly described below. The first method is to perform shot peening or burnishing on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11.

[0045] The second method is to roll each rolling element 10 against the inner ring 3 and the outer ring 6 for a short time before using the rolling bearing 1 at a first maximum contact pressure that is higher than the second maximum contact pressure during normal use of the rolling bearing 1. The ratio of the high first maximum contact pressure to the second maximum contact pressure may be greater than 1.0 or may be greater than 1.3. The ratio of the high first maximum contact pressure to the second maximum contact pressure is not particularly limited, but may be less than 3.0 or 2.5 or less. For example, the first maximum contact pressure may be 5.6 GPa and the second maximum contact pressure may be 3.0 GPa. For example, by rolling each rolling element 10 against the inner ring 3 and the outer ring 6 at a first maximum contact surface pressure of 5.6 GPa before use of the rolling bearing 1, as shown in FIG. 8 , a first residual compressive stress σ is generated in at least one surface layer region of the inner ring 3, the outer ring 6, and each rolling element 10, including at least one surface of the inner ring 3, the outer ring 6, and each rolling element 10 (i.e., at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11). y0 The second residual compressive stress σ x0 can be larger than

[0046] The effects of the rolling bearing 1 of this embodiment will be described. The rolling bearing 1 of this embodiment comprises an inner ring 3, an outer ring 6 arranged on the outer periphery of the inner ring 3, and a plurality of rolling elements 10 arranged between the inner ring 3 and the outer ring 6. The inner ring 3 has a first raceway surface 4. The outer ring 6 has a second raceway surface 7 opposing the first raceway surface 4. Each of the plurality of rolling elements 10 has a rolling surface 11 that contacts the first raceway surface 4 and the second raceway surface 7. A first residual compressive stress σ in the axial direction (y direction) of the inner ring 3 and the outer ring 6 is generated in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. y0 is a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the inner ring 3 and the outer ring 6 of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. x0 is greater than.

[0047] A first radius of curvature of at least one of the inner ring 3, outer ring 6, and each rolling element 10 in the axial direction (y direction) of the rolling bearing 1 is different from a second radius of curvature of at least one of the inner ring 3, outer ring 6, and each rolling element 10 in the circumferential direction (x direction) of the rolling bearing 1. Therefore, the contact stress between the inner ring 3 and each rolling element 10 in the axial direction (y direction) of the rolling bearing 1 is different from the contact stress between the inner ring 3 and each rolling element 10 in the circumferential direction (x direction) of the rolling bearing 1. The contact stress between the outer ring 6 and each rolling element 10 in the axial direction (y direction) of the rolling bearing 1 is different from the contact stress between the outer ring 6 and each rolling element 10 in the circumferential direction (x direction) of the rolling bearing 1.

[0048] A first residual compressive stress σ in the axial direction (y direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. y0 a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11; x0 The first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be made larger than e0According to the rolling bearing 1 of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed, and a rolling bearing 1 having a long life can be provided.

[0049] In the rolling bearing 1 of this embodiment, the first equivalent stress σ e0 is a second equivalent stress σ of at least one of the inner ring 3, the outer ring 6, and each rolling element 10, which has at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. e2 The second equivalent stress σ e2 is the maximum value of equivalent stress inside at least one of the inner ring 3, the outer ring 6, and each rolling element 10. According to the rolling bearing 1 of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed, and a rolling bearing 1 with a long life can be provided.

[0050] Residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 y may be maximum on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 in the thickness direction of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. Therefore, the first equivalent stress σ acting on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0 According to the rolling bearing 1 of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed, and a rolling bearing 1 having a long life can be provided.

[0051] Residual compressive stress σ in the axial direction (y direction) of at least one of the inner ring 3, the outer ring 6, and each rolling element 10 y may be maximum inside at least one of the inner ring 3, the outer ring 6 and each rolling element 10 in the thickness direction of at least one of the inner ring 3, the outer ring 6 and each rolling element 10. Therefore, the first equivalent stress σ acting on at least one of the inner ring 3, the outer ring 6 and each rolling element 10e0 According to the rolling bearing 1 of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed, and a rolling bearing 1 having a long life can be provided.

[0052] In the rolling bearing 1 of this embodiment, the first residual compressive stress σ with respect to the maximum contact surface pressure acting between each of the plurality of rolling elements 10 and at least one of the inner ring 3 and the outer ring 6 is y0 The ratio may be equal to or greater than -0.7 and less than 0.0. Therefore, the first equivalent stress σ in at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 e0 decreases to the first equivalent stress σ e0 is the second equivalent stress σ of at least one of the inner ring 3, the outer ring 6, and each rolling element 10. e2 According to the rolling bearing 1 of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 can be suppressed, and a rolling bearing 1 having a long life can be provided.

[0053] In the rolling bearing 1 of this embodiment, the multiple rolling elements 10 may be multiple rollers. The anisotropic residual compressive stress imparted to at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 reduces the equivalent stress acting on the inner ring 3, the outer ring 6, and at least one of the rollers in surface layer regions R1, R2 of the inner ring 3, the outer ring 6, and at least one of the rollers, which includes at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11. The rolling bearing 1 of this embodiment can suppress the occurrence of surface-initiated flaking on at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11 of each roller, and can provide a rolling bearing 1 with a long life.

[0054] (Embodiment 2) A rolling bearing 1b according to embodiment 2 will be described with reference to Figures 9 and 10. The rolling bearing 1b of this embodiment has a similar configuration to the rolling bearing 1 of embodiment 1, but differs mainly in the following respects.

[0055] In the rolling bearing 1b of this embodiment, the multiple rolling elements 10b are multiple balls. The rolling bearing 1b may be a deep groove ball bearing. The radius of curvature of each rolling element 10b in the axial direction (y direction) is substantially equal to the radius of curvature of each rolling element 10b in the circumferential direction (x direction). Each rolling element 10b has a substantially isotropic shape in the axial direction (y direction) and the circumferential direction (x direction).

[0056] A first radius of curvature of at least one of the inner ring 3 and the outer ring 6 in the axial direction (y direction) of the rolling bearing 1b is different from a second radius of curvature of at least one of the inner ring 3 and the outer ring 6 in the circumferential direction (x direction) of the rolling bearing 1b. In this embodiment, the radius of curvature of the inner ring 3 in the axial direction (y direction) is different from the radius of curvature of the inner ring 3 in the circumferential direction (x direction). The radius of curvature of the outer ring 6 in the axial direction (y direction) is different from the radius of curvature of the outer ring 6 in the circumferential direction (x direction). Specifically, the radius of curvature of the inner ring 3 in the axial direction (y direction) may be larger than the radius of curvature of the inner ring 3 in the circumferential direction (x direction). The radius of curvature of the outer ring 6 in the axial direction (y direction) may be larger than the radius of curvature of the outer ring 6 in the circumferential direction (x direction).

[0057] In this embodiment, in the surface layer region of at least one of the inner ring 3 and the outer ring 6, including at least one of the first raceway surface 4 and the second raceway surface 7, the residual compressive stress σ in the axial direction (y direction) y is the residual compressive stress σ in the circumferential direction (x direction) x In this embodiment, the residual compressive stress σ in the axial direction (y direction) in the thickness direction of at least one of the inner ring 3 and the outer ring 6 is larger than y Distribution of residual compressive stress σ in the circumferential direction (x direction) x The distribution of the residual compressive stress σ in the axial direction (y direction) in the thickness direction of at least one of the inner ring 3 and the outer ring 6 in the first embodiment is y Distribution of residual compressive stress σ in the circumferential direction (x direction) x In this embodiment, no anisotropic residual compressive stress is applied to the rolling surface 11.

[0058] The rolling bearing 1b of this embodiment has the same effects as the rolling bearing 1 of the first embodiment, as described below.

[0059] In the rolling bearing 1b of this embodiment, the plurality of rolling elements 10b are balls. At least one of the first raceway surface 4 and the second raceway surface 7 has a first residual compressive stress σ in the axial direction (y direction). y0 is the second residual compressive stress σ in the circumferential direction (x direction) x0 is greater than.

[0060] In rolling bearing 1b of this embodiment, a first radius of curvature of at least one of inner ring 3 and outer ring 6 in the axial direction (y direction) of rolling bearing 1b is different from a second radius of curvature of at least one of inner ring 3 and outer ring 6 in the circumferential direction (x direction) of rolling bearing 1b. Therefore, the contact stress between inner ring 3 and each ball in the axial direction (y direction) of rolling bearing 1b is different from the contact stress between inner ring 3 and each ball in the circumferential direction (x direction) of rolling bearing 1b. The contact stress between outer ring 6 and each ball in the axial direction (y direction) of rolling bearing 1b is different from the contact stress between outer ring 6 and each ball in the circumferential direction (x direction) of rolling bearing 1b.

[0061] A first residual compressive stress σ in the axial direction (y direction) of at least one of the first raceway surface 4 and the second raceway surface 7 y0 a second residual compressive stress σ in the circumferential direction (x direction) of at least one of the first raceway surface 4, the second raceway surface 7, and the rolling surface 11; x0 By making the first equivalent stress σ in at least one of the inner ring 3 and the outer ring 6 larger than e0 According to the rolling bearing 1b of this embodiment, the occurrence of surface-initiated flaking on at least one of the first raceway surface 4 and the second raceway surface 7 can be suppressed, and a rolling bearing 1b having a long life can be provided.

[0062] The first and second embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1, 1b rolling bearing, 2 shaft, 3 inner ring, 4 first raceway surface, 6 outer ring, 7 second raceway surface, 10, 10b rolling elements, 11 rolling surface, 15 cage.

Claims

1. A rolling bearing used under lean lubrication conditions, the rolling bearing comprising: an inner ring having a first raceway surface; an outer ring disposed on an outer peripheral side of the inner ring, the outer ring having a second raceway surface opposing the first raceway surface; and a plurality of rolling elements disposed between the inner ring and the outer ring, each of the plurality of rolling elements having a rolling surface in contact with the first raceway surface and the second raceway surface; the first raceway surface is a surface of the inner ring with which the plurality of rolling elements contact, the second raceway surface is a surface of the outer ring with which the plurality of rolling elements contact, and the rolling surface is a surface of the rolling element that contacts the first raceway surface and the second raceway surface, a first von Mises stress in at least one of the first raceway surface, the second raceway surface, and the rolling surface is smaller than a yield stress of a material constituting the at least one of the first raceway surface, the second raceway surface, and the rolling surface; a rolling bearing, wherein the first von Mises stress in the at least one of the first raceway surface, the second raceway surface, and the rolling surface is smaller than a second von Mises stress in at least one of the inner ring, the outer ring, and the plurality of rolling elements that have the at least one of the first raceway surface, the second raceway surface, and the rolling surface, and the second von Mises stress is a maximum value of the von Mises stress inside the at least one of the inner ring, the outer ring, and the plurality of rolling elements.

2. 2. The rolling bearing according to claim 1, wherein a ratio of a first residual compressive stress in an axial direction of the at least one of the inner ring and the outer ring of the first raceway surface, the second raceway surface, and the rolling surface to a second residual compressive stress in a circumferential direction of the at least one of the inner ring and the outer ring of the first raceway surface, the second raceway surface, and the rolling surface is greater than 1.

3. 3. The rolling bearing according to claim 1, wherein the plurality of rolling elements are a plurality of rollers.

4. the plurality of rolling elements are a plurality of balls, 4. The rolling bearing according to claim 1, wherein the at least one of the first raceway surface, the second raceway surface, and the rolling surface is at least one of the first raceway surface and the second raceway surface.

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