Rolling bearings

Abstract

To provide a low-cost rolling bearing that prevents galvanic corrosion of rolling bearings while simultaneously preventing creep caused by strain in the outer or inner ring during the rolling of the rolling elements. [Solution] The rolling bearing comprises an outer ring having an outer ring raceway surface on its inner diameter surface, an inner ring having an inner ring raceway surface on its outer diameter surface, and rolling elements arranged to roll freely between the outer ring raceway surface and the inner ring raceway surface, and has an insulating resin coating covering at least one of the outer diameter surface of the outer ring and the inner diameter surface of the inner ring. The insulating resin coating has recesses extending in the circumferential direction at positions where at least a portion overlaps with the outer ring raceway surface or the inner ring raceway surface when viewed from the radial direction of the outer ring or the inner ring.

Description

Technical Field

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

Background Art

[0002] Rolling bearings are widely used to support rotating parts of various rotating machines, such as the drive unit of an automobile. Generally, a rolling bearing includes an outer ring and an inner ring, and a plurality of rolling elements that are rotatably arranged between the outer ring and the inner ring.

[0003] For example, the outer diameter surface of the outer ring is fitted to a housing, which is a fixed member of the rotating machine, and the inner diameter surface of the inner ring is fitted to a rotating shaft. At this time, a phenomenon called creep may occur, in which the two rotate relative to each other between the outer diameter surface of the outer ring and the housing, or between the inner diameter surface of the inner ring and the rotating shaft. Creep causes wear of the outer diameter surface of the outer ring, the inner diameter surface of the inner ring, the housing, or the rotating shaft.

[0004] It is known that creep is roughly classified into wobbling creep due to the clearance between the outer diameter surface or the inner diameter surface of the outer ring or the inner ring and the housing or the rotating shaft, and strain creep due to the strain of the outer ring or the inner ring.

[0005] Strain creep occurs when a radial load is applied to the rolling bearing and the rolling elements roll. In such an environment, as the rolling elements roll, strains that cause circumferential expansion and contraction occur in the outer ring or the inner ring. The outer ring or the inner ring applies pressure to the housing or the rotating shaft due to the circumferential strain, and as a reaction, creep occurs when the outer ring or the inner ring receives a force to rotate. The rolling bearing described in Patent Document 1 provides a groove portion extending in the circumferential direction on the outer diameter surface of the outer ring or the inner diameter surface of the inner ring, that is, the fitting surface with the housing or the shaft member, in order to prevent strain creep. Thereby, the strain generated in the outer ring or the inner ring is not transmitted to the housing or the rotating shaft as pressure, and strain creep is suppressed.

[0006] Furthermore, in rolling bearings used in electric vehicle motors, leakage current can cause discharge between the rolling elements and the outer or inner ring, leading to electrolytic corrosion of the rolling elements, outer ring, or inner ring. In response to this, there are known rolling bearings, such as the one described in Patent Document 2, that prevent electrolytic corrosion by covering the surface of the outer or inner ring with an insulating resin material to suppress leakage current.

[0007] The rolling bearing described in Patent Document 3 has a coating layer consisting of multiple layers of highly lubricating lubricating layers and insulating layers on the outer diameter surface of the outer ring or the inner diameter surface of the inner ring. This improves lubrication when creep occurs, prevents wear between the outer diameter surface of the outer ring or the inner diameter surface of the inner ring and the housing or rotating shaft, and also prevents electrolytic corrosion due to leakage current. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2019-113126 [Patent Document 2] Japanese Patent Publication No. 2022-85600 [Patent Document 3] Japanese Patent Publication No. 2022-42162 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The rolling bearing described in Patent Document 1 attempts to counteract strain creep by providing a circumferentially extending groove in the axial center of the outer diameter surface of the outer ring or the inner diameter surface of the inner ring. However, because the groove is created by processing the metal raceway itself, it increases manufacturing time and costs. Furthermore, it is still difficult to sufficiently suppress the occurrence of creep. In addition, since the rolling bearing described in Patent Document 1 is composed only of metal members, it does not have a function to prevent galvanic corrosion. The rolling bearing described in Patent Document 2 has a function to prevent galvanic corrosion but does not have a function to prevent creep.

[0010] The rolling bearing described in Patent Document 3 achieves both the function of preventing wear during creep and the function of preventing galvanic corrosion by providing a lubricating layer and an insulating layer. However, since it is necessary to provide multiple layers on the raceway, the manufacturing process is time-consuming and costs are increased. Furthermore, this invention reduces friction during creep by using a lubricating layer, and does not have the effect of suppressing creep itself.

[0011] The present invention has been made in view of the above problems, and its purpose is to provide a rolling bearing at low cost that can prevent galvanic corrosion of the rolling bearing and at the same time prevent creep caused by strain in the outer or inner ring when the rolling elements are rolling. [Means for solving the problem]

[0012] The above objective of the present invention is achieved by the following configuration. (1) An outer ring having an outer ring raceway surface on its inner diameter surface, An inner ring having an inner ring raceway surface on its outer diameter surface, A rolling element is disposed to roll freely between the outer ring raceway surface and the inner ring raceway surface, A rolling bearing equipped with, The outer ring has an insulating resin coating that covers at least one of the outer diameter surface and the inner diameter surface of the inner ring, The insulating resin coating has a recess extending in the circumferential direction at a position where, when viewed from the radial direction of the outer ring or the inner ring, it overlaps with at least a portion of the outer ring raceway surface or the inner ring raceway surface. A rolling bearing characterized by the following. [Effects of the Invention]

[0013] According to the present invention, a rolling bearing can be provided at low cost that prevents galvanic corrosion of the rolling bearing and simultaneously prevents creep caused by strain in the outer or inner ring during the rolling of the rolling elements. [Brief explanation of the drawing]

[0014] [Figure 1]FIG. 1 is a schematic cross-sectional view taken perpendicular to the circumferential azimuth showing an example of a rolling bearing according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view taken perpendicular to the circumferential azimuth showing another example of a rolling bearing according to an embodiment of the present invention. [Figure 3] FIG. 3 is a graph showing analysis results of creep amounts in cases where the rolling bearing is not provided with a resin coating, is provided with a resin coating having no recess, and is provided with a resin coating having a recess. [Figure 4] FIG. 4 is a graph showing the time change of the surface pressure at the point where the surface pressure in the rolling bearing is maximum. [Figure 5] FIG. 12 is a graph showing the relationship between the thickness of the resin coating and the creep amount. [Figure 6] FIG. 15 is a diagram showing the surface pressure distribution in the housing when the rolling bearing is not provided with a resin coating. [Figure 7] FIG. 18 is a diagram showing the surface pressure distribution in the housing when the rolling bearing is provided with a resin coating having no recess. [Figure 8] FIG. 21 is a diagram showing the surface pressure distribution in the housing when the rolling bearing is provided with a resin coating having a recess. [Figure 9] FIG. 24 is a diagram showing the surface pressure distribution in the housing when the rolling bearing is provided with a resin coating having a recess formed deeper than that in FIG. 8. [Figure 10] FIG. 27 is a diagram showing the relationship between the depth of the recess of the resin coating and the surface pressure at the bottom and shoulder portions. [Figure 11] FIG. 30 is a diagram showing the relationship between the depth of the recess of the resin coating and the creep amount. [Figure 12] FIG. 33 is a schematic cross-sectional view taken perpendicular to the circumferential azimuth showing a resin coating according to Modification 1 of the present embodiment. [Figure 13] FIG. 36(a) is an enlarged view showing Region C in FIG. 32. FIG. 36(b) is an enlarged view showing the same range as Region C in FIG. 32 for a resin coating according to Modification 2 of the present embodiment. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a cross-sectional view perpendicular to the circumferential direction of an example of a rolling bearing according to an embodiment of the present invention. Figure 2 is a cross-sectional view perpendicular to the circumferential direction of another example of a rolling bearing according to an embodiment of the present invention.

[0016] As shown in Figures 1 and 2, the rolling bearing 10 comprises an outer ring 20 having an outer ring raceway surface 21 on its inner diameter surface, an inner ring 30 having an inner ring raceway surface 31 on its outer diameter surface, and rolling elements 50 arranged to roll freely between the outer ring raceway surface 21 and the inner ring raceway surface 31. In this embodiment, the rolling elements 50 are balls, and the outer ring raceway surface 21 and the inner ring raceway surface 31 are formed to extend in the circumferential direction, with a cross-sectional shape perpendicular to the circumferential direction being arc-shaped. Multiple rolling elements 50 are arranged in the circumferential direction between the outer ring raceway surface 21 and the inner ring raceway surface 31.

[0017] Furthermore, the outer ring 20 and the inner ring 30 are fitted to a mating member, which is either the housing 60 or the shaft member 70. In this embodiment, the outer ring 20 is fitted to the housing 60, the inner ring 30 is fitted to the shaft member 70, and the rolling bearing 10 rotatably supports the shaft member 70 relative to the housing 60.

[0018] Furthermore, the rolling bearing 10 has an insulating resin coating 100 that covers at least one of the outer diameter surface 22 of the outer ring and the inner diameter surface 32 of the inner ring on the outer ring 20 or the inner ring 30. Here, Figure 1 shows a case in which the rolling bearing 10 has an insulating resin coating 100 that covers the outer diameter surface 22 of the outer ring 20, and Figure 2 shows a case in which the rolling bearing 10 has an insulating resin coating 100 that covers the inner diameter surface 32 of the inner ring 30. That is, the outer ring 20 and inner ring 30 of the rolling bearing 10 according to this embodiment include cases in which the outer ring 20 and inner ring 30 are composed as shown in Figure 1, cases in which the outer ring 20 and inner ring 30 are composed as shown in Figure 2, and cases in which the outer ring 20 is shown in Figure 1 and the inner ring 30 is shown in Figure 2. Hereinafter, the insulating resin coating 100 may be simply referred to as the resin coating 100.

[0019] As shown in Figure 1, the outer ring 20 is coated with a resin film 100 on its outer diameter surface 22, its outer end surface 23 which is continuous with the outer diameter surface 22 and perpendicular to the axis, and a region which is continuous with the outer end surface 23 and extends from both axial ends of the inner diameter surface of the outer ring 20 toward the outer ring raceway surface 21. Grooves 24 extending in the circumferential direction are formed between both axial ends of the inner diameter surface of the outer ring 20 and the outer ring raceway surface 21, and a portion of the resin film 100 on the inner diameter side is formed to fill the grooves 24. In this way, the resin film 100 and the outer ring 20 are fixed to each other.

[0020] The resin coating 100 formed on the outer ring 20 has a recess 104 that is recessed inward on the fitting surface 102, which is the surface facing the housing 60. The recess 104 is formed around the entire circumference of the outer ring 20 so as to extend in the circumferential direction. The recess 104 also has a bottom portion 108, which is the deepest recessed part on the inward diameter side. In this embodiment, the recess 104 formed in the resin coating 100 on the outer ring 20 side is formed in a position that overlaps with the outer ring raceway surface 21 at least in part when viewed from the radial direction of the outer ring 20. Here, "viewed from the radial direction of the outer ring 20" means viewing the outer ring 20 from a position separated in a direction perpendicular to the outer ring outer diameter surface 22. That is, the axial positions of the region on the inner diameter surface of the outer ring 20 where the outer ring raceway surface 21 is formed and the region on the outer ring outer diameter surface 22 where the recess 104 is formed coincide in at least part of the same location.

[0021] Furthermore, on the outer ring 20 side, the recess 104 of the resin coating 100 is recessed toward the inner diameter side, so shoulder portions 106 are formed on both axial ends of the recess 104, protruding from the outer diameter surface 22 of the outer ring over the entire circumference. That is, the recess 104 of the resin coating 100 on the outer ring 20 side is configured to be sandwiched between the shoulder portions 106 protruding from the outer diameter surface 22 of the outer ring. The shoulder portions 106 on the fitting surface 102 are in contact with the surface of the housing 60 that faces the outer ring 20. The shoulder portions 106 elastically deform so as to collapse when a predetermined load is applied to the rolling bearing 10. Here, the predetermined load is the radial load that acts when the rolling bearing 10 is incorporated into a rotating machine and the rotating machine is operating under normal operating conditions.

[0022] Furthermore, in this embodiment, the recess 104 is a curved surface that smoothly connects to the shoulder portion 106. That is, the recess 104 is formed as an inclined surface that slopes radially outward from the bottom portion 108 to the shoulder portion 106, towards both ends in the axial direction. Note that the recess 104 does not have to be an inclined surface; as will be described later, its cross-section perpendicular to the circumferential direction may be approximately U-shaped.

[0023] As shown in Figure 2, the inner ring 30 is coated with a resin film 100 on its inner diameter surface 32, its inner end surface 33 which is continuous with the inner diameter surface 32 and perpendicular to the axis, and a region which is continuous with the inner end surface 33 and extends from both axial ends of the outer diameter surface of the inner ring 30 in the direction of the inner raceway surface 31. Grooves 34 extending in the circumferential direction are formed between both axial ends of the outer diameter surface of the inner ring 30 and the inner raceway surface 31, and a portion of the resin film 100 on the outer diameter side is formed to fill the grooves 34. In this way, the resin film 100 and the inner ring 30 are fixed to each other.

[0024] The resin coating 100 formed on the inner ring 30 has a recess 104 that is recessed toward the outer diameter side on the fitting surface 102, which is the surface facing the shaft member 70. The recess 104 is formed around the entire circumference of the inner ring 30 so as to extend in the circumferential direction. The recess 104 also has a bottom portion 108, which is the deepest recessed part toward the outer diameter side. The recess 104 formed in the resin coating 100 on the inner ring 30 is also formed in a position that overlaps with the inner ring raceway surface 31 at least in part when viewed from the radial direction of the inner ring 30. Here, "viewed from the radial direction of the inner ring 30" means viewing the inner ring 30 from a position separated in a direction perpendicular to the inner diameter surface 32 of the inner ring. That is, the axial positions of the region on the outer diameter surface of the inner ring 30 where the inner ring raceway surface 31 is formed and the region on the inner diameter surface 32 where the recess 104 is formed coincide in at least part of the same location.

[0025] On the inner ring 30 side, the recess 104 in the resin coating 100 is recessed toward the outer diameter side of the inner ring 30, so shoulder portions 106 are formed on both axial ends of the recess 104, protruding from the inner diameter surface 32 of the inner ring over the entire circumference. The shoulder portions 106 on the fitting surface 102 are in contact with the outer circumferential surface of the shaft member 70. The shoulder portions 106 elastically deform so as to collapse when a predetermined load is applied to the rolling bearing 10.

[0026] Furthermore, in this embodiment, the recess 104 is a curved surface that smoothly connects to the shoulder portion 106. That is, the recess 104 is formed as an inclined surface that slopes radially inward from the bottom portion 108 to the shoulder portion 106, towards both ends in the axial direction. Note that the recess 104 does not have to be an inclined surface; its cross-section perpendicular to the circumferential direction may be approximately U-shaped.

[0027] In this embodiment, the recess 104 is formed in the area indicated by A in Figures 1 and 2. The outer ring raceway surface 21 and the inner ring raceway surface 31 are formed in the area indicated by B on the inner diameter surface of the outer ring 20 or the outer diameter surface of the inner ring 30 in Figures 1 and 2. The resin coating 100 is formed such that the recess 104 overlaps at least a portion of the area indicated by A with respect to the radial direction of the outer ring 20 or inner ring 30. In the example shown in Figures 1 and 2, the area indicated by A is larger than the area indicated by B, and the area indicated by A overlaps with the entire area indicated by B when viewed from the radial direction of the outer ring 20 or inner ring 30. In this embodiment, the recess 104 and the outer ring raceway surface 21 and inner ring raceway surface 31 are located in the axial center, and the centerlines O of the areas indicated by A and B coincide.

[0028] When a predetermined load is applied to the rolling bearing 10, the recess 104 is formed to a depth such that the bottom 108 of the recess 104 does not come into contact with the mating member. The predetermined load is the radial load that acts when the rolling bearing 10 is incorporated into a rotating machine and the rotating machine is operating under normal operating conditions. When no load is applied to the rolling bearing 10, the recess 104 forms a radial gap between itself and the mating member, i.e., the housing 60 or the shaft member 70. When a radial load is applied to the rolling bearing 10, the shoulder portion 106 of the resin coating 100 that comes into contact with the housing 60 or the shaft member 70 undergoes elastic deformation. Even at this time, a gap is maintained between the recess 104 and the housing 60 or the shaft member 70, and the axial center portion of the recess 104 does not come into contact with the housing 60 or the shaft member 70. Note that in Figure 1 and Figures 2, 12, and 13 described later, the depth of the recess 104 is exaggerated to show that it is formed to a depth that does not come into contact with the mating member. The actual depth of the recess 104 is shallower than shown in Figures 1, 2, 12, and 13.

[0029] The following describes the effect on creep caused by providing a resin coating 100 with recesses 104 on the rolling bearing 10, as well as the specific radial depth of the recesses 104 and the radial thickness of the resin coating 100. As shown in Figures 1 and 2, in the outer ring 20, the radial thickness of the thinnest part between the outer diameter surface 22 and the outer ring raceway surface 21 is defined as t1, and in the inner ring 30, the radial thickness of the thinnest part between the inner diameter surface 32 and the inner ring raceway surface 31 is defined as t2, the radial thickness of the bottom portion 108 of the resin coating 100 is defined as t3.

[0030] Figure 3 is a graph showing the analysis results of creep ratios for rolling bearings without an insulating resin coating, with an insulating resin coating without recesses, and with an insulating resin coating with recesses. In the following explanation of Figures 3 to 11, the insulating resin coating may be referred to simply as the resin coating. The creep ratio in Figure 3 is the ratio when the value for the case without a resin coating is set to 1. In Figure 3, the depth of the recesses in the case where the resin coating has recesses is set to 10 μm and 40 μm. Furthermore, Figures 3 and Figures 4 to 11 described later are analysis results using the finite element method for an outer ring with a diameter of 62 mm and a radial thickness, i.e., t1 in Figure 1, of 3 mm. Furthermore, in Figure 3 and Figures 4, 6-11 described later, the radial thickness t2 of the resin coating, that is, the radial thickness at the mating surface when the resin coating does not have recesses, and the radial thickness at the bottom of the mating surface when the resin coating has recesses, are set to 0.5 mm. In addition, in Figure 3 and Figures 4-11 described later, the load applied to the rolling bearing was analyzed as the load applied under normal operating conditions when the rolling bearing is incorporated into the rotating machine assumed in this embodiment. Specifically, the radial load applied to the rolling bearing was set to 7800 N.

[0031] As shown in Figure 3, the amount of creep in a rolling bearing with a resin coating is less than the amount of creep in a rolling bearing without an insulating coating. Furthermore, the amount of creep in a rolling bearing with a resin coating that has recesses is less than the amount of creep in a resin coating that does not have recesses. Moreover, the amount of creep when the depth of the recesses in the resin coating is 40 μm is less than the amount of creep when the depth of the recesses is 10 μm. In other words, it is considered that a creep prevention effect can be obtained by providing a resin coating, and an even greater creep prevention effect can be obtained by providing recesses in the resin coating.

[0032] Figure 4 is a graph showing the time variation of surface pressure at the point where the surface pressure is maximum in a rolling bearing. In Figure 4, the horizontal axis represents the passage of time, and the vertical axis represents the magnitude of the surface pressure. The dashed line graph represents the surface pressure at the axial center of a rolling bearing without a resin coating, and is the surface pressure at point P located in the axial center of the inner diameter surface 161 of the housing 160 shown in Figure 6 below. The dashed line graph represents the surface pressure at the axial center of a rolling bearing with a resin coating that does not have a recess, and is the surface pressure at point Q located in the axial center of the inner diameter surface 161 of the housing 160 shown in Figure 7 below. The solid line graph represents the surface pressure at the shoulder of a rolling bearing with a resin coating that has a recess, and is the surface pressure at point R located near the axial end of the inner diameter surface 161 of the housing 160 shown in Figure 9 below. In this case, the depth of the recess is set to 40 μm.

[0033] As shown in Figure 4, the surface pressure changes periodically with time. Furthermore, the period of change in surface pressure is the same as the period of time the rolling element passes near the point where the surface pressure is maximum. In other words, in a rolling bearing, it is thought that the surface pressure changes so that the area between the rolling bearing and the mating members such as the housing and shaft member, where the surface pressure is higher than the surrounding area, moves in the circumferential direction as the rolling element rolls.

[0034] Furthermore, Figure 4 shows that when a rolling bearing does not have a resin coating (dashed line), the change in surface pressure over time is large, while when a rolling bearing has a resin coating (dotted and solid lines), the change in surface pressure over time is relatively small. Also, comparing the case where the resin coating has recesses (solid line) with the case where there are recesses (dotted line), the change in surface pressure over time is smaller when there are recesses. By providing a resin coating with recesses on a rolling bearing, even if localized strain occurs in the axial center of the outer or inner ring during the rolling element's movement, the bottom of the recess does not contact the housing, and only the vicinity of the shoulder continues to contact the housing. As a result, the strain of the outer or inner ring is not transmitted to the housing or shaft members, and the shoulder elastically deforms, causing it to collapse, which is thought to reduce the change in surface pressure over time at the shoulder.

[0035] The analysis results in Figures 3 and 4 show a correlation between the amount of creep and the change in surface pressure over time. Specifically, when a rolling bearing does not have a resin coating, the change in surface pressure over time is large, and the amount of creep is also large. However, when a rolling bearing has a resin coating, and the resin coating has recesses, the change in surface pressure over time is small, and the amount of creep is also small. From the above, it is considered that strain creep occurs when the strain generated in the outer or inner ring due to the rolling of the rolling elements transmits surface pressure to the housing, and the surface pressure transmitted to the housing changes so that it moves in the circumferential direction. Based on these findings, the appropriate thickness of the resin coating and the depth of the recesses for preventing creep will be explained below.

[0036] First, we will explain the relationship between the radial thickness of the resin coating and the amount of creep. Figure 5 is a graph showing the relationship between the thickness of the resin coating and the amount of creep. In Figure 5, a resin coating with a uniform thickness t2 (=0mm, 0.25mm, 0.3mm, 0.4mm, 0.45mm, 0.5mm, 0.6mm, 0.8mm, 1mm, 1.5mm, 2mm) in the axial direction without any recesses is applied to an outer ring with a diameter of 62mm and a radial thickness t1 of 3mm, and the amount of creep when the radial thickness of the resin coating is changed is determined by the finite element method. That is, the resin coating used in the analysis in Figure 5 is the analysis result when t2=t3 is applied to resin coating 100 shown in Figure 1, and the radial thickness at the mating surface of the resin coating used in the analysis in Figure 3 is expressed as t2 regardless of the axial position. Also, in Figure 5, the amount of creep is expressed as a ratio to the amount of creep when no resin coating is applied, with the amount of creep being set to 1.

[0037] As shown in Figure 5, when the radial thickness t2 of the resin coating on the mating surface is between 0.25 mm and 2 mm, the creep ratio is 0.9 or less, and the amount of creep is reduced by about 10% to 20% compared to when no resin coating is provided. Furthermore, when the thickness t2 of the resin coating is within the above range, the creep ratio remains almost constant even if the thickness t2 of the resin coating is increased. Therefore, no superior effect on creep prevention can be confirmed by increasing the thickness t2 of the resin coating. On the other hand, increasing the thickness t2 of the resin coating is undesirable from a manufacturing standpoint, and in this embodiment, it is preferable that t2 be around 0.5 mm or less. Also, when t2 is 0.25 mm or less, the moldability during injection molding deteriorates. In other words, under the load conditions assumed in this embodiment, considering the creep prevention effect and the manufacturing standpoint such as the enlargement of the rolling bearing, increased material costs, and moldability, it is preferable that 0.25 mm ≤ t2 ≤ 0.5 mm. Furthermore, as shown in Figure 3, the amount of creep when a rolling bearing has a resin coating with recesses is smaller than the amount of creep when it has a resin coating without recesses. Therefore, it is considered that even if the dimensional relationship of 0.25 mm ≤ t2 ≤ 0.5 mm, which was suggested in the analysis shown in Figure 5 using a resin coating without recesses, is applied to a resin coating with recesses, it will still be able to sufficiently prevent creep.

[0038] In other words, as shown in Figure 1, when the rolling bearing 10 has a resin coating 100 on the outer diameter surface 22 of the outer ring 20, it is preferable that the radial thickness t2 of the bottom portion 108 of the resin coating 100 is 0.25 mm ≤ t2 ≤ 0.5 mm.

[0039] Furthermore, the above dimensional relationship is also considered applicable to the inner ring 30, which has a shape symmetrical to the outer ring 20. That is, as shown in Figure 2, even when the rolling bearing 10 has a resin coating 100 on the inner diameter surface 32 of the inner ring 30, it is preferable that the radial thickness t2 of the bottom portion 108 of the resin coating 100 is 0.25 mm ≤ t2 ≤ 0.5 mm.

[0040] The analysis results shown in Figure 4 suggest that the amount of creep is influenced by the change in surface pressure. Next, we will discuss the relationship between the depth of the recesses in the resin coating and the distribution of surface pressure. Below, we will explain the analysis results by focusing on the distribution of surface pressure at the contact surface between the outer ring or inner ring and the housing or rotating shaft, while varying the presence or absence of the resin coating and the depth of the recesses in the resin coating. Figure 6 shows the distribution of surface pressure in the housing when the rolling bearing does not have a resin coating. Figure 7 shows the distribution of surface pressure in the housing when the rolling bearing has a resin coating without recesses. Figure 8 shows the distribution of surface pressure in the housing when the rolling bearing has a resin coating with recesses. Figure 9 shows the distribution of surface pressure in the housing when the rolling bearing has a resin coating with recesses formed deeper than in Figure 8. As mentioned above, the surface pressures shown in Figures 6 to 9 are the analysis results at the moment when the surface pressure is maximum while the rolling bearing is rotating. Figure 6 shows the results of a finite element analysis of a rolling bearing with an outer ring having a diameter of 62 mm and a radial thickness (t1 in Figure 1) of 3 mm, without a resin coating. Figures 7-9 show the results of a finite element analysis of a rolling bearing with an outer ring having a diameter of 62 mm and a radial thickness (t1) of 3 mm, with a resin coating. The radial thickness (t2) at the bottom of the resin coating, i.e., the axial center, is assumed to be 0.5 mm. Regarding the depth of the recesses in the resin coating, Figure 7 shows the surface pressure distribution when the resin coating has no recesses and the recess depth is 0 μm, Figure 8 shows the recess depth is 10 μm (t3 in Figure 1 is 0.51 mm), and Figure 9 shows the surface pressure distribution when the recess depth is 40 μm (t3 in Figure 1 is 0.54 mm). The surface pressure distributions shown in Figures 6-9 are the results of analyzing the surface pressure at the contact surface between the outer ring and the housing. The figure shows the distribution of surface pressure on the inner diameter surface 161 of the housing 160, and this distribution can be considered as the distribution of surface pressure applied to the outer ring or resin coating that is in contact with the housing 160.

[0041] As shown in Figure 6, when the rolling bearing does not have a resin coating, the surface pressure on the inner diameter surface 161 of the housing 160 is higher at the axial center of the rolling bearing than at the surrounding area. This is thought to be because the rolling elements roll on the outer ring raceway surface located at the axial center, generating local strain at the axial center of the outer ring and applying local pressure to the housing 160. Furthermore, as shown in Figures 7-9, when the rolling bearing has a resin coating, it was found that as the depth of the recess is increased from 0 μm to 10 μm and 40 μm, the surface pressure on the inner diameter surface 161 of the housing 160 gradually decreases at the axial center (bottom of the resin coating) and gradually increases at both axial ends (shoulders of the resin coating). In particular, as shown in Figure 9, when the depth of the recess of the resin coating is 40 μm, it can be confirmed that the axial center of the resin coating is not in contact with the inner diameter surface 161 of the housing 160, and no surface pressure is generated.

[0042] The following describes the relationship between the depth of the recess in the resin coating, the magnitude of the surface pressure, and the amount of creep. Figure 10 shows the relationship between the depth of the recess in the resin coating and the surface pressure at the bottom and shoulders. Figure 11 shows the relationship between the depth of the recess in the resin coating and the amount of creep. In Figures 10 and 11, the depth of the recess t3-t2 is changed by changing the radial thickness at the shoulders of the resin coating, i.e., both ends in the axial direction, and the relationship between the depth of the recess, the surface pressure, and the amount of creep is analyzed. The vertical axis in Figure 10 represents the magnitude of the surface pressure, and the vertical axis in Figure 11 represents the magnitude of the creep. Furthermore, the surface pressure shown in Figure 10 is the result of the analysis of the surface pressure at the shoulders and bottom at the moment when the surface pressure is maximum while the rolling bearing is rotating.

[0043] As shown in detail in Figure 10, the relationship between the depth of the recess and the surface pressure increases as the depth of the recess gradually increases. Furthermore, the surface pressure at the bottom gradually decreases in the recess depth range from 0 μm to 25 μm, and no surface pressure is generated in the recess depth range of 25 μm or more. In other words, it was confirmed that when the recess depth is 25 μm or more, the bottom, located in the axial center of the recess, does not come into contact with the housing or shaft member.

[0044] Furthermore, as shown in Figure 11, which illustrates the relationship between the depth of the recess and the amount of creep, increasing the depth of the recess reduces the amount of creep, while increasing the depth of the recess to 25 μm or more results in the lowest value of creep. These results confirm that creep can be suppressed by increasing the depth of the recess so that the bottom does not come into contact with the housing or shaft member.

[0045] As shown in Figures 3 and 4, by providing a resin coating on a rolling bearing and further providing recesses in the resin coating, the change in surface pressure over time is suppressed, and the amount of creep is also suppressed. Furthermore, as shown in Figures 10 and 11, creep is suppressed by setting the depth of the recess to a depth where the bottom does not contact the housing (25 μm or more in this example).Therefore, in the present invention, regardless of the various dimensions of the outer ring or inner ring, by providing a resin coating with a recess having a depth where the bottom does not contact the housing or shaft member on the outer ring or inner ring, the change in surface pressure over time between the rolling bearing and the mating member can be suppressed, and the occurrence of creep can be effectively prevented.

[0046] In this embodiment, t1 is 3 mm and t2 is 0.5 mm, and it is preferable that the depth of the recess 104 be set to at least 25 μm. That is, it is preferable that the radial thickness t3 of the shoulder portion 106 is 0.525 mm or more. On the other hand, if the shoulder portion 106 is formed to be thick in the radial direction, the radial displacement of the shaft member 70 due to the elastic deformation of the shoulder portion 106 may increase, or it may cause molding defects in the resin coating 100. It may also cause material creep of the shoulder portion 106. Therefore, it is preferable that the depth of the recess 104 be formed to a depth such that the bottom portion 108 does not come into contact with the housing 60 or the shaft member 70, but it should not be formed to be excessively deep.

[0047] In this embodiment, it is preferable to use a resin material containing polyphenylene sulfide, polybutylene terephthalate, polyethylene terephthalate, polytetrafluoroethylene, phenolic resin, epoxy resin, etc. for the resin coating 100. Furthermore, it is preferable to mix carbon fibers or glass fibers into the resin material in a proportion of 10% to 50% in order to improve strength. In addition, it is preferable that the resin coating 100 be formed by injection molding, which is low cost.

[0048] The rolling bearing 10 has an insulating resin coating 100 on at least one of the outer diameter surface 22 of the outer ring 20 or the inner diameter surface 32 of the inner ring 30. This prevents leakage current in the rotating machine from flowing between the outer ring 20, the rolling elements 50, and the inner ring 30. As a result, the occurrence of electrolytic corrosion can also be prevented.

[0049] Furthermore, in the rolling bearing 10, even if creep occurs, the resin coating 100 acts as a buffer, preventing wear between the outer ring 20 and the housing 60, or between the inner ring 30 and the shaft member 70.

[0050] Furthermore, the resin coating 100 according to the present invention only needs to be positioned so that it has a recess 104 between the outer diameter surface 22 of the outer ring 20 or the inner diameter surface 32 of the inner ring 30 and the mating member, such as the housing 60 or shaft member 70. Therefore, the resin coating 100 only needs to be fixed so as to cover at least the outer diameter surface 22 of the outer ring or the inner diameter surface 32 of the inner ring, and it is not necessary for the resin coating 100 to cover the end faces perpendicular to the axial direction of the outer ring 20 or inner ring 30, the inner diameter surface of the outer ring, or the outer diameter surface of the inner ring.

[0051] In the rolling bearing described in Patent Document 1, a groove is provided on the outer diameter surface of the outer ring or the inner diameter surface of the inner ring. This configuration aims to prevent creep by making it difficult for strain generated in the rolling bearing to be transmitted to the mating member. However, since the outer and inner rings are made of steel, when a load is applied to the rolling bearing, large forces are applied to both axial sides, which can cause localized unevenness in surface pressure, making it difficult to sufficiently suppress the occurrence of creep. Furthermore, the configuration of providing grooves in the steel outer and inner rings requires additional manufacturing steps.

[0052] In contrast, in this embodiment, grooves, or recesses 104, are provided in the resin coating 100, and the shoulder portion 106 is easily deformed by pressure, so when a load is applied to the rolling bearing 10, the contact area on the shoulder portion 106 increases. As a result, the change in surface pressure over time is suppressed, and the occurrence of creep can be suppressed. In addition, since at least one of the outer diameter surface 22 of the outer ring and the inner diameter surface 32 of the inner ring is covered with the insulating resin coating 100, galvanic corrosion due to metal-to-metal contact can be prevented. In other words, in this embodiment, by mounting the insulating resin coating 100 having recesses 104 to the rolling bearing, it is possible to provide a rolling bearing that is easy to manufacture and has creep prevention and galvanic corrosion prevention functions.

[0053] The following describes modifications of this embodiment. Figure 12 is a diagram showing a cross-section perpendicular to the circumferential direction of the resin coating according to Modification 1 of this embodiment. Figure 13(a) is a diagram showing an enlarged view of region C in Figure 12. Figure 13(b) is a diagram showing an enlarged view of the same area as region C in Figure 12 of the resin coating according to Modification 2 of this embodiment. The same configuration as in the previously described embodiment will not be described.

[0054] As shown in the modified example 1 in Figures 12 and 13(a), the recess 104 may have a uniform depth along the axial direction, except for the axial ends of the recess 104. In modified example 1, inclined surfaces are formed at both axial ends of the recess 104, and these inclined surfaces are connected to the shoulder portion 106.

[0055] As shown in the modified example 2 in Figure 13(b), the recess 104 has a uniform depth along the axial direction, and wall surfaces facing the axial center are formed at both axial ends of the recess 104. In the example in Figure 13, these wall surfaces are connected to the shoulder portion 106.

[0056] Furthermore, in this embodiment, the resin coating 100 preferably has a t2 of 0.25 mm ≤ t2 ≤ 0.5 mm and a recess depth of 25 μm or more, as described above, but the present invention is not limited thereto. Also, the surface shapes of the recess 104 and the shoulder portion 106 can be deformed as appropriate. Moreover, the present invention is not limited to the above resin material, and it is also possible to mix other fiber materials in any proportion for the purpose of improving the strength of the resin material. Furthermore, the resin coating 100 can be molded by methods other than injection molding.

[0057] As described above, the following matters are disclosed in this specification: (1) An outer ring having an outer ring raceway surface on its inner diameter surface, An inner ring having an inner ring raceway surface on its outer diameter surface, A rolling element is disposed to roll freely between the outer ring raceway surface and the inner ring raceway surface, A rolling bearing equipped with, The outer ring has an insulating resin coating that covers at least one of the outer diameter surface and the inner diameter surface of the inner ring, The insulating resin coating has a recess extending in the circumferential direction at a position where, when viewed from the radial direction of the outer ring or the inner ring, it overlaps with at least a portion of the outer ring raceway surface or the inner ring raceway surface. A rolling bearing characterized by the following. This configuration makes it possible to provide a low-cost rolling bearing that prevents galvanic corrosion of the rolling bearing while simultaneously preventing creep caused by strain in the outer or inner ring during the rolling motion of the rolling elements.

[0058] (2) The outer ring and the inner ring are fitted to a mating member which is a housing or shaft member. When a predetermined load is applied to the rolling bearing, the bottom of the recess does not come into contact with the mating member. The rolling bearing according to (1), characterized in that This configuration can enhance the creep prevention effect.

[0059] (3) The insulating resin coating is connected to the recess and has shoulders formed at both ends in the axial direction, The rolling bearing according to (1) or (2), characterized in that the shoulder portion is elastically deformable so as to collapse when a predetermined load is applied to the rolling bearing. This configuration suppresses changes in surface pressure over time, effectively preventing creep.

[0060] (4) The insulating resin coating covering the outer diameter surface of the outer ring is When the radial thickness of the bottom portion of the insulating resin coating is t2, 0.25mm ≤ t2 ≤ 0.5mm A rolling bearing according to any one of (1) to (3), characterized by the above. This configuration allows for creep prevention when a predetermined load is applied radially, and also prevents the resin coating from becoming excessively thick and causing the rolling bearing to enlarge.

[0061] (5) The insulating resin coating that covers the inner diameter surface of the inner ring is When the radial thickness of the bottom portion of the insulating resin coating is t2, 0.25mm ≤ t2 ≤ 0.5mm A rolling bearing according to any one of (1) to (4), characterized by the above. This configuration allows for creep prevention when a predetermined load is applied radially, and also prevents the resin coating from becoming excessively thick and causing the rolling bearing to enlarge.

[0062] (6) The insulating resin coating is formed by injection molding. A rolling bearing according to any one of (1) to (5), characterized in that... This configuration allows for the inexpensive and easy manufacture of insulating resin coatings. [Explanation of Symbols]

[0063] 10 bearings 20 Outer ring 21 Outer ring raceway surface 22 Outer ring outer diameter surface 23 Outer ring end face 24,34 grooves 30 Inner circle 31 Inner ring raceway surface 32 Inner diameter surface of inner ring 33 Inner ring end face 50 Rolling element 60 Housing 70 Shaft member 100 Insulating resin coating (resin coating) 102 Mating surface 104 recess 106 Shoulder 108 Bottom

Claims

1. An outer ring having an outer ring raceway surface on its inner diameter surface, An inner ring having an inner ring raceway surface on its outer diameter surface, A rolling element is disposed to roll freely between the outer ring raceway surface and the inner ring raceway surface, A rolling bearing equipped with, The outer ring has an insulating resin coating that covers at least one of the outer diameter surface and the inner diameter surface of the inner ring, The insulating resin coating has a recess extending in the circumferential direction at a position where, when viewed from the radial direction of the outer ring or the inner ring, it overlaps with at least a portion of the outer ring raceway surface or the inner ring raceway surface. A rolling bearing characterized by the following.

2. The outer ring and the inner ring are fitted to a mating member which is a housing or shaft member. When a predetermined load is applied to the rolling bearing, the bottom of the recess does not come into contact with the mating member. The rolling bearing according to claim 1, characterized in that...

3. The insulating resin coating is connected to the recess and has shoulder portions formed at both axial ends, When a predetermined load is applied to the rolling bearing, the shoulder portion is elastically deformable so as to collapse. A rolling bearing according to claim 1 or 2, characterized in that...

4. The insulating resin coating covering the outer diameter surface of the outer ring is When the radial thickness of the bottom portion of the insulating resin coating is t2, 0.25 mm ≤ t² ≤ 0.5 mm The rolling bearing according to claim 2, characterized in that...

5. The insulating resin coating that covers the inner diameter surface of the inner ring is When the radial thickness of the bottom portion of the insulating resin coating is t2, 0.25 mm ≤ t² ≤ 0.5 mm The rolling bearing according to claim 2, characterized in that...

6. The insulating resin coating is formed by injection molding. A rolling bearing according to claim 4 or 5, characterized in that...

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