Insulated rolling bearings

Abstract

The present invention provides an insulated rolling bearing in which, when an insulating coating is formed on the outer surface of the outer ring using heat-shrinkable resin, air bubbles are less likely to form on the insulating coating, and damage to the insulating coating during insertion of the bearing into the housing is prevented. [Solution] In an insulated rolling bearing in which the insulating coating 5 is made of a heat-shrinkable resin that shrinks when heated, the outer ring 1 has an outer peripheral surface 1a, a chamfered portion 1b, an axial end surface 1c, and an outer peripheral groove 1d, and the insulating coating 5 has an outer peripheral coating portion 5a, a chamfered coating portion 5b, an end surface coating portion 5c, and an outer peripheral groove coating portion 5d.

Description

Technical Field

[0001] This invention relates to an insulated rolling bearing.

Background Art

[0002] In a rolling bearing that supports the rotating shaft of a device using electricity, such as an electric motor or an alternator (generator), when an electric current flows inside the bearing, a spark may occur between the outer ring or the inner ring and the rolling elements, and the surface of the outer ring, inner ring, or rolling elements may be locally melted by the spark (electric corrosion). As a rolling bearing capable of preventing this electric corrosion, an insulated rolling bearing provided with an insulating coating on the outer ring is known (for example, Patent Document 1).

[0003] The insulated rolling bearing of Patent Document 1 has an outer ring, an inner ring disposed radially inside the outer ring, a plurality of rolling elements incorporated between the outer ring and the inner ring, and a resin insulating coating provided on the outer ring. This insulating coating is formed by insert molding (that is, a method of molding the insulating coating by injecting molten resin into the cavity inside the mold with the outer ring set in the mold).

[0004] When providing a resin insulating coating on the outer ring, it is mainstream to form the insulating coating by insert molding as in Patent Document 1. However, forming the insulating coating by insert molding requires large-scale equipment and molds, so there is a problem that the manufacturing cost of the insulated rolling bearing becomes high.

[0005] Therefore, in order to reduce the manufacturing cost of the insulated rolling bearing, an insulated rolling bearing provided with an insulating coating by a method different from insert molding, as proposed in Patent Document 2, has been proposed.

[0006] The insulated rolling bearing of Patent Document 2 is formed by arranging a tubular heat-shrinkable resin on the radially outer side of the outer ring and heating and shrinking the tubular heat-shrinkable resin to form a resin insulating coating that covers the outer peripheral surface and a pair of axial end faces of the outer ring.

Prior Art Documents

[0007] [Patent Document 1] Patent No. 3068311 [Patent Document 2] Japanese Patent Publication No. 2001-107974 [Overview of the project] [Problems that the invention aims to solve]

[0008] Incidentally, when the inventor of the present application prototyped an insulated rolling bearing as described in Patent Document 2, he encountered a problem in which, when a tubular heat-shrinkable resin was heated and shrunk, air was trapped between the tubular heat-shrinkable resin and the outer surface of the outer ring, causing bubbles to form in the insulating coating.

[0009] In other words, the insulated rolling bearing of Patent Document 2 has an outer ring whose outer surface is a cylindrical surface with a constant outer diameter along the axial direction. A tubular heat-shrinkable resin with an inner diameter larger than the outer diameter of the outer ring is placed radially outside this outer ring. When this tubular heat-shrinkable resin is heated and shrunk, the shrinkage rate of the tubular heat-shrinkable resin is not perfectly uniform depending on the axial position. As the tubular heat-shrinkable resin shrinks, air becomes trapped between the tubular heat-shrinkable resin and the outer surface of the outer ring, forming bubbles. These trapped bubbles cause blistering in the insulating coating.

[0010] If air bubbles form in the insulating coating on the outer surface of the outer ring, when inserting the insulated rolling bearing into the housing, the swollen portion of the insulating coating on the outer surface of the outer ring may catch on the housing, damaging a portion of the insulating coating. As a result, the insulating performance of the insulating coating may be significantly reduced.

[0011] The problem that this invention aims to solve is to provide an insulated rolling bearing that, when an insulating coating is formed on the outer surface of the outer ring using heat-shrinkable resin, is less prone to blistering of the insulating coating, and that prevents damage to the insulating coating when the bearing is inserted into the housing. [Means for solving the problem]

[0012] To solve the above problems, this invention provides an insulated rolling bearing with the following configuration. [Configuration 1] Outer ring and, An inner ring positioned radially inward of the outer ring, A plurality of rolling elements are incorporated between the outer ring and the inner ring, The outer ring has a resin insulating coating provided on it, In an insulated rolling bearing in which the insulating coating is formed of a heat-shrinkable resin that shrinks when heated, The outer ring has a cylindrical outer surface with a constant outer diameter along the axial direction, a pair of chamfered portions with a circular arc cross-section whose outer diameter gradually decreases axially outward from the outer surface, a pair of axial end faces extending radially inward from the pair of chamfered portions, and an outer groove extending circumferentially through the axial center of the outer surface. The insulating rolling bearing is characterized in that the insulating coating comprises a cylindrical outer circumferential coating portion that covers the outer circumferential surface of the outer ring, a pair of chamfer coating portions with a circular arc cross-section that cover the pair of chamfer portions of the outer ring, a pair of end face coating portions that cover the pair of axial end faces of the outer ring, and an outer groove coating portion that covers the outer circumferential groove in a recessed state relative to the outer circumferential coating portion.

[0013] With this configuration, an outer groove is provided that extends circumferentially through the axial center of the cylindrical outer surface of the outer ring. When the heat-shrinkable resin is placed on the radially outer side of the outer ring and heated to shrink it, the air between the heat-shrinkable resin and the outer surface of the outer ring can be released into the outer groove of the outer ring. Therefore, as the heat-shrinkable resin shrinks, less air remains between the heat-shrinkable resin and the outer surface of the outer ring, and blistering of the insulating coating is less likely to occur. Consequently, when inserting the insulated rolling bearing into the housing, damage to the insulating coating caused by the outer ring catching on the housing can be prevented.

[0014] [Configuration 2] The insulating rolling bearing according to configuration 1, wherein the outer circumferential groove covering portion is in contact with the bottom of the outer circumferential groove.

[0015] With this configuration, the outer groove covering portion of the insulating coating is in contact with the bottom of the outer groove of the outer ring, resulting in a large contact area between the insulating coating and the outer ring. Therefore, the fixing strength of the insulating coating to the outer ring is high, making it possible to prevent relative movement between the insulating coating and the outer ring in the circumferential direction during bearing rotation.

[0016] [Configuration 3] The insulating rolling bearing according to configuration 2, wherein an air reservoir is formed between the groove side of the outer circumferential groove and the outer circumferential groove covering portion.

[0017] [Structure 4] The groove bottom has a cylindrical groove bottom surface having a constant groove bottom diameter along the axial direction, and a pair of recessed portions with a smaller diameter than the groove bottom surface that extend circumferentially adjacent to both sides of the groove bottom surface in the axial direction. The insulating rolling bearing according to configuration 2, wherein the outer circumferential groove covering portion is in contact with the bottom surface of the groove, and an air reservoir is formed between the inner surface of the recessed portion and the outer circumferential groove covering portion.

[0018] When this configuration is adopted, since a pair of stealing portions are formed on both axial sides of the groove bottom surface of the outer ring's outer peripheral groove, when heating and shrinking the heat-shrinkable resin, the air existing between the heat-shrinkable resin and the groove bottom of the outer ring's outer peripheral groove can be released to the stealing portions of the groove bottom. As a result, it becomes possible to surely contact the insulating coating of the outer ring with the groove bottom surface of the outer ring's outer peripheral groove.

[0019] [Configuration 5] On the groove bottom, a knurling pattern in which ridges and valleys alternate is formed. The insulating rolling bearing according to Configuration 2, wherein the outer peripheral groove covering portion contacts the apex of the ridge portion, and an air pocket is formed between the inner surface of the valley portion and the outer peripheral groove covering portion.

[0020] When this configuration is adopted, since a knurling pattern is formed on the groove bottom of the outer ring's outer peripheral groove, when heating and shrinking the heat-shrinkable resin, the air existing between the heat-shrinkable resin and the groove bottom of the outer ring's outer peripheral groove can be released to the valleys of the knurling pattern. As a result, it becomes possible to surely contact the insulating coating of the outer ring with the groove bottom surface of the outer ring's outer peripheral groove.

[0021] Also, since the insulating coating is fixed to the outer ring by contact between the insulating coating and the ridges of the knurling pattern, the fixing strength of the insulating coating to the outer ring is high, and it is possible to surely prevent the insulating coating and the outer ring from relatively moving in the circumferential direction during bearing rotation.

[0022] [Configuration 6] The insulating rolling bearing according to any one of Configurations 2 to 5, wherein the groove depth of the outer peripheral groove from the outer peripheral surface is set to be 0.2 mm or more and 1.0 mm or less.

[0023] When this configuration is adopted, since the groove depth of the outer peripheral groove is set to be 1.0 mm or less, it is possible to surely contact the insulating coating of the outer ring with the groove bottom surface of the outer ring's outer peripheral groove.

[0024] [Configuration 7] On both axial ends of the inner periphery of the outer ring, annular recesses that open to the axial end surface of the outer ring and extend in the circumferential direction are formed. The insulating rolling bearing according to any one of configurations 1 to 6, wherein the insulating coating further has an inner diameter extension that extends radially inward from the radial inner end of the end face covering portion and faces axially with a gap between it and the inner surface of the annular recess.

[0025] With this configuration, annular recesses are formed at both axial ends of the inner circumference of the outer ring, and the inner diameter extension of the insulating coating is positioned facing the inner surface of the annular recess with a gap between them in the axial direction. This allows for a large axial creepage distance between the outer ring and the stepped portion of the inner circumference of the housing that abuts against the axial end face of the outer ring for positioning, thereby effectively preventing surface discharge between the outer ring and the housing.

[0026] [Structure 8] Annular recesses are formed at both axial ends of the inner circumference of the outer ring, extending in the circumferential direction and opening to the axial end faces of the outer ring. The insulating rolling bearing according to any one of configurations 1 to 6, wherein the insulating coating further has an inner diameter extension formed by bending the radial inner end of the end face covering portion axially inward so as to cover the inner surface of the annular recess.

[0027] With this configuration, annular recesses are formed at both axial ends of the inner circumference of the outer ring, and an inner diameter extension covering the inner surface of the annular recess is provided in the insulating coating. This allows for a large axial creepage distance between the outer ring and the stepped portion on the inner circumference of the housing that abuts against the axial end face of the outer ring for positioning, thereby effectively preventing surface discharge between the outer ring and the housing.

[0028] [Composition 9] The annular recess is formed in an L-shape in cross-section, having an inner circumferential surface of the recess extending axially inward from the radially inward end of the axial end face of the outer ring, and a recessed side surface extending radially inward from the axially inward end of the inner circumferential surface of the recess. The insulating rolling bearing according to configuration 8, wherein the inner diameter extension portion is also formed in an L-shaped cross-section along the inner circumferential surface of the recess and the side surface of the recess.

[0029] By adopting this configuration, it is possible to ensure a large creepage distance between the outer ring and the stepped portion on the inner circumference of the housing that abuts against the axial end face of the outer ring for positioning.

[0030] [Configuration 10] The insulating rolling bearing according to configuration 9, wherein the inner circumferential surface of the recess is formed to be inclined radially outward with respect to the axially inward direction.

[0031] With this configuration, the inner circumferential surface of the recess is inclined radially outward in the axial direction, which reliably prevents the insulating coating from interfering with and being damaged by the inner circumferential surface of the recess when the jig is pressed against the insulating coating to form an L-shaped cross-section, and provides excellent formability for the inner diameter extension of the insulating coating.

[0032] [Composition 11] An insulated rolling bearing according to any one of configurations 1 to 10, wherein the groove width of the outer circumferential groove is set to be 25% or more of the width dimension between the pair of axial end faces of the outer ring.

[0033] With this configuration, the groove width of the outer ring's outer circumference groove is set to be at least 25% of the outer ring's width. This prevents the deformation of the outer ring caused by the load applied to it by the rolling elements during bearing rotation from being transmitted as a traveling wave to the housing that houses the outer ring. As a result, it is possible to prevent the phenomenon of the outer ring gradually rotating relative to the housing (creep phenomenon) and the wear and damage to the coating associated with this creep phenomenon. [Effects of the Invention]

[0034] The insulated rolling bearing of this invention has an outer groove that extends circumferentially through the axial center of the cylindrical outer surface of the outer ring. Therefore, when a heat-shrinkable resin is placed on the radially outer side of the outer ring and heated to shrink it, the air present between the heat-shrinkable resin and the outer surface of the outer ring can be released into the outer groove of the outer ring. As a result, as the heat-shrinkable resin shrinks, less air remains between the heat-shrinkable resin and the outer surface of the outer ring, and blistering of the insulating coating is less likely to occur. Consequently, when inserting the insulated rolling bearing into the housing, damage to the insulating coating due to the insulating coating of the outer ring catching on the housing can be prevented. [Brief explanation of the drawing]

[0035] [Figure 1] Cross-sectional view showing an insulated rolling bearing according to the first embodiment of this invention. [Figure 2] Enlarged view of the vicinity of the axial end of the outer groove in Figure 1. [Figure 3] Figure 1 shows an example of the usage state of an insulated rolling bearing. [Figure 4] Cross-sectional view showing an insulated rolling bearing according to a second embodiment of this invention. [Figure 5] Enlarged view of the vicinity of the axial end of the outer groove in Figure 4. [Figure 6] Cross-sectional view showing an insulated rolling bearing according to a third embodiment of this invention. [Figure 7] Enlarged view of the vicinity of the outer groove in Figure 6. [Figure 8] Cross-sectional view along line VIII-VIII in Figure 7 [Figure 9] Cross-sectional view showing an insulated rolling bearing according to the fourth embodiment of this invention. [Figure 10] This figure shows the state before and after forming the inner diameter extension portion of the insulating coating of an insulated rolling bearing according to the fifth embodiment of this invention into an L-shaped cross-section. [Modes for carrying out the invention]

[0036] Figure 1 shows an insulated rolling bearing according to a first embodiment of the present invention. This insulated rolling bearing comprises an outer ring 1, an inner ring 2 coaxially arranged radially inward of the outer ring 1, a plurality of rolling elements 3 mounted between the outer ring 1 and the inner ring 2 at circumferential intervals, an annular cage 4 that maintains the circumferential intervals of the plurality of rolling elements 3, and a resin insulating coating 5 provided on the outer ring 1.

[0037] The axial direction is parallel to the central axis of the outer ring 1 (the central axis of the bearing), the radial direction is perpendicular to the central axis of the outer ring 1, and the circumferential direction is along the circumference that revolves around the central axis of the outer ring 1. The outer ring 1 and inner ring 2 are formed symmetrically with respect to the axial center. Furthermore, the axial inner side is the side that approaches the center position of the rolling element 3 along the axial direction, and the axial outer side is the side that moves away from the center position of the rolling element 3 along the axial direction.

[0038] The rolling element 3 is radially sandwiched between the outer ring raceway groove 6 formed on the inner circumference of the outer ring 1 and the inner ring raceway groove 7 formed on the outer circumference of the inner ring 2. The rolling element 3 is a ball in this case. The outer ring raceway groove 6 and the inner ring raceway groove 7 are grooves with an arc-shaped cross-section perpendicular to the circumferential direction. The outer ring 1, inner ring 2, and rolling element 3 are each made of steel.

[0039] The outer ring 1 has a cylindrical outer surface 1a, a pair of chamfered portions 1b with a circular arc cross-section whose outer diameter gradually decreases axially outward from the outer surface 1a, a pair of axial end faces 1c extending radially inward from the pair of chamfered portions 1b, and an outer groove 1d extending circumferentially through the axial center of the outer surface 1a.

[0040] The outer circumferential surface 1a is a cylindrical surface with a constant outer diameter that does not change along the axial direction. The outer circumferential groove 1d is continuously provided around the entire circumference of the outer ring 1, passing through the axial center of the outer circumferential surface 1a, and the outer circumferential surface 1a is divided in the axial direction by this outer circumferential groove 1d. As a result, a pair of outer circumferential surfaces 1a are provided adjacent to each other on both sides of the outer circumferential groove 1d in the axial direction.

[0041] The outer circumferential groove 1d has a cylindrical groove bottom 8 with a constant groove bottom diameter along the axial direction, and groove side surfaces 9 adjacent to both sides of the groove bottom 8 in the axial direction. The groove side surfaces 9 are inclined surfaces that gradually increase in diameter toward the axially outward direction. The inclination angle of the groove side surfaces 9 with respect to the axial direction is set to 45° or less (preferably 30° or less), and by providing this inclination angle on the groove side surfaces 9, stress concentration that occurs at the boundary between the outer circumferential groove 1d and the outer circumferential surface 1a when the bearing is in use is mitigated. The chamfered portion 1b of the outer ring 1 is an arc-shaped surface whose cross-section perpendicular to the circumferential direction smoothly connects to the outer circumferential surface 1a of the outer ring 1, and the axial end surface 1c is a plane perpendicular to the axial direction.

[0042] The outer diameter of the outer circumferential surface 1a of the outer ring 1 is set to be between 45 mm and 110 mm. The width dimension between the pair of axial end faces 1c of the outer ring 1 is set to be between 9 mm and 30 mm. The groove width of the outer circumferential groove 1d (i.e., the distance between the boundary of the outer circumferential groove 1d and the outer circumferential surfaces 1a on both sides) is set to be between 25% (preferably 35% or more) and 50% of the width dimension between the pair of axial end faces 1c of the outer ring 1. The groove depth of the outer circumferential groove 1d from the outer circumferential surface 1a is set to be between 0.2 mm and 1.0 mm. The outer circumferential surface 1a is formed by centerless grinding, and the outer circumferential groove 1d is formed by turning. The arc radius of the cross section perpendicular to the circumferential direction of the chamfered portion 1b of the outer ring 1 is set to be between 0.3 mm and (preferably 0.5 mm or more).

[0043] The insulating coating 5 includes a pair of cylindrical outer peripheral coating portions 5a that cover a pair of outer peripheral surfaces 1a of the outer ring 1, a pair of chamfered coating portions 5b with an arc cross-section that cover a pair of chamfered portions 1b of the outer ring 1, a pair of end face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1, and an outer groove coating portion 5d that covers an outer peripheral groove 1d.

[0044] The pair of outer peripheral covering portions 5a are formed in a cylindrical shape that closely adheres to the pair of outer peripheral surfaces 1a on both sides of the outer peripheral groove 1d. The outer peripheral groove covering portion 5d is formed between the pair of outer peripheral covering portions 5a and covers the outer peripheral groove 1d in a state that is recessed radially inward relative to the outer peripheral covering portions 5a. The positions of the axial ends of the outer peripheral groove covering portion 5d correspond to the positions of the axial ends of the outer peripheral groove 1d.

[0045] As shown in Figure 2, the outer groove covering portion 5d is in contact with the groove bottom 8 of the outer groove 1d. In addition, an air reservoir 10 is formed between the groove side surface 9 of the outer groove 1d and the outer groove covering portion 5d.

[0046] As shown in Figure 1, the pair of chamfered covering portions 5b are formed in conjunction with the axial outer end of the outer peripheral covering portion 5a, and the pair of end face covering portions 5c are formed in conjunction with the radial inner ends of the pair of chamfered covering portions 5b. The end face covering portions 5c are preferably provided in close contact with the axial end face 1c of the outer ring 1, but they may also be provided in a state where they are lifted away from the axial end face 1c of the outer ring 1 (a state where there is a gap between the axial end face 1c of the outer ring 1 and the end face covering portion 5c).

[0047] The insulating coating 5 is set to have a thickness such that it has a withstand voltage of 200V or more and an insulation resistance of 1MΩ or more, at least at the position of the outer peripheral coating portion 5a. This insulating coating 5 is formed of a tubular heat-shrinkable resin that shrinks when heated, as will be described later.

[0048] This insulated rolling bearing can be manufactured as follows:

[0049] First, a rolling bearing is prepared, which incorporates multiple rolling elements 3 between the outer ring 1 and the inner ring 2 as shown in Figure 1. At this stage, the insulating coating 5 shown in Figure 1 has not yet been provided. Next, a tubular heat-shrinkable resin having an inner diameter larger than the outer diameter of the outer circumferential surface 1a of the outer ring 1 is placed radially outside the outer ring 1. As the tubular heat-shrinkable resin (heat-shrinkable tube), for example, a resin material such as polyolefin resin, polyvinyl chloride resin, fluororesin, or elastomer can be molded into a tube, irradiated with radiation to crosslink the resin material, then heated to a predetermined high temperature, stretched radially (or radially and axially), and cooled. Then, the insulating coating 5 shown in Figure 1 is formed by heating and shrinking the tubular heat-shrinkable resin placed radially outside the outer ring 1. The heat-shrinkable resin referred to here is a resin that, unlike general resins, has the characteristic of shrinking (thermal shrinkage) when heated, and this thermal shrinkage occurs, for example, due to a change in the degree of crystallinity accompanying heating. The insulating coating 5, formed from heat-shrinkable resin, inherently contains a residual stress field due to compression, and in this respect, it differs from resin insulating layers formed by other methods such as injection molding.

[0050] Incidentally, when the tubular heat-shrinkable resin positioned radially on the outer side of the outer ring 1 is heated and shrunk, if we consider the case where the outer ring 1 does not have an outer circumferential groove 1d (i.e., when a standard outer ring 1 is used), the shrinkage rate of the heat-shrinkable resin is not perfectly uniform depending on the axial position. As the heat-shrinkable resin shrinks, air becomes trapped between the heat-shrinkable resin and the outer circumferential surface 1a of the outer ring 1, forming bubbles. These trapped bubbles cause blistering in the insulating coating 5 (heat-shrinkable resin after shrinkage). When this blistering occurs, when inserting the insulated rolling bearing into the housing 12 (see Figure 3), the blistered portion of the insulating coating 5 may catch on the housing 12, damaging a part of the insulating coating 5, which may result in a significant decrease in the insulating performance of the insulating coating 5.

[0051] To address this problem, the insulated rolling bearing of the above embodiment, as shown in Figure 1, is provided with an outer circumferential groove 1d that extends circumferentially through the axial center of the cylindrical outer surface 1a of the outer ring 1. Therefore, when a tubular heat-shrinkable resin is placed radially outside the outer ring 1 and heated to shrink it, the air present between the heat-shrinkable resin and the outer surface 1a of the outer ring 1 can be released into the outer circumferential groove 1d of the outer ring 1. As a result, as the shrinkage of the tubular heat-shrinkable resin progresses, less air remains between the heat-shrinkable resin and the outer surface 1a of the outer ring 1, and blistering of the insulating coating 5 is less likely to occur. Consequently, as shown in Figure 3, when inserting and assembling the insulated rolling bearing into the housing 12, damage to the insulating coating 5 due to the insulating coating 5 catching on the housing 12 can be prevented.

[0052] Furthermore, as shown in Figure 2, in this insulated rolling bearing, the outer groove covering portion 5d of the insulating coating 5 is in contact with the groove bottom 8 of the outer groove 1d of the outer ring 1, resulting in a large contact area between the insulating coating 5 and the outer ring 1. Therefore, the fixing strength of the insulating coating 5 to the outer ring 1 is high, making it possible to prevent relative movement between the insulating coating 5 and the outer ring 1 in the circumferential and axial directions during bearing rotation.

[0053] Furthermore, in this insulated rolling bearing, the groove width of the outer circumference groove 1d shown in Figure 1 is set to be 25% or more (preferably 35% or more) of the width dimension between the pair of axial end faces 1c of the outer ring 1. This prevents the deformation of the outer ring 1 caused by the load applied to the outer ring 1 from the rolling elements 3 during bearing rotation from being transmitted as a traveling wave to the housing 12 shown in Figure 3. Therefore, it is possible to prevent the phenomenon of the outer ring 1 gradually rotating relative to the housing 12 (creep phenomenon). In Figure 1, the outer ring 1 is mounted on the inner circumference of the non-rotating housing 12 with a clearance fit, and the inner ring 2 is mounted on the outer circumference of the rotating shaft 13 of an electrical device (electric motor, alternator, etc.) with an interference fit. The outer ring 1 is also positioned axially by pressing its axial end face 1c against the stepped portion 14 on the inner circumference of the housing 12.

[0054] Figures 4 and 5 show an insulated rolling bearing according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in the configuration of the outer circumference groove 1d of the outer ring 1, but the other configurations are basically the same. Therefore, the same reference numerals are used for parts corresponding to the first embodiment, and their description is omitted.

[0055] As shown in Figure 4, the groove bottom 8 of the outer circumferential groove 1d has a cylindrical groove bottom surface 15 with a constant groove bottom diameter along the axial direction, and a pair of recessed portions 16 with a smaller diameter than the groove bottom surface 15 that extend circumferentially adjacent to both sides of the groove bottom surface 15 in the axial direction. The depth of the groove bottom surface 15 from the outer circumferential surface 1a is set to be between 0.2 mm and 1.0 mm. The depth of the recessed portions 16 from the groove bottom surface 15 is set to be between 0.2 mm and 0.5 mm.

[0056] As shown in Figure 5, the outer groove covering portion 5d is in contact with the groove bottom surface 15 of the outer groove 1d, and an air pocket 17 is formed between the inner surface of the recessed portion 16 and the outer groove covering portion 5d.

[0057] As shown in Figure 4, the insulated rolling bearing of this embodiment has a pair of recessed portions 16 formed on both axial sides of the groove bottom surface 15 of the outer peripheral groove 1d of the outer ring 1. When the tubular heat-shrinkable resin is heated and shrunk, the air present between the heat-shrinkable resin and the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1 can escape into the recessed portions 16 formed at the corners of the groove bottom 8, as shown in Figure 5. As a result, the insulating coating 5 of the outer ring 1 can be reliably brought into contact with the groove bottom surface 15 of the outer peripheral groove 1d of the outer ring 1. Other effects are the same as in the first embodiment.

[0058] Figures 6 to 8 show an insulated rolling bearing according to a third embodiment of the present invention. The third embodiment differs from the first embodiment in the configuration of the outer circumference groove 1d of the outer ring 1, but the other configurations are basically the same. Therefore, the same reference numerals are used for parts corresponding to the first embodiment, and their description is omitted.

[0059] As shown in Figure 8, knurling is formed on the groove bottom 8 of the outer circumferential groove 1d, with alternating peaks 18 and valleys 19. The outer circumferential groove covering 5d contacts the peaks 18, and an air pocket 20 is formed between the inner surface of the valleys 19 and the outer circumferential groove covering 5d. Furthermore, as shown in Figure 7, non-knurled sections 21 with a diameter smaller than the diameter passing through the peaks 18 of the knurling are formed at both axial ends of the groove bottom 8, and an air pocket 22 is also formed between these non-knurled sections 21 and the outer circumferential groove covering 5d.

[0060] In the diagram, a flat knurling pattern is used, in which straight peaks 18 and straight valleys 19 extending in the axial direction are alternately arranged in the circumferential direction. However, it is also possible to use a diagonal knurling pattern in which pyramidal peaks and V-groove-shaped valleys formed to surround the pyramidal peaks from all sides are alternately arranged. The groove bottom diameter of the outer circumferential groove 1d (the diameter connecting the vertices of the peaks 18) is smaller than the outer diameter of the outer circumferential surface 1a. The groove depth of the outer circumferential groove 1d from the outer circumferential surface 1a (the depth from the outer circumferential surface 1a to the vertices of the peaks 18) is set to be between 0.2 mm and 1.0 mm.

[0061] In this embodiment, the insulated rolling bearing has knurling formed on the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1. When the tubular heat-shrinkable resin is heated and shrunk, the air present between the heat-shrinkable resin and the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1 can escape into the valleys 19 of the knurling, as shown in Figure 8. As a result, the insulating coating 5 of the outer ring 1 can be reliably brought into contact with the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1 (the peaks 18 of the knurling).

[0062] Furthermore, as shown in Figure 7, since knurled non-formed portions 21 with a smaller diameter than the diameter passing through the peaks 18 of the knurled pattern are formed at both axial ends of the groove bottom 8, when the tubular heat-shrinkable resin is heated and shrunk, the air present between the heat-shrinkable resin and the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1 can be released into the knurled non-formed portions 21. As a result, the insulating coating 5 of the outer ring 1 can be reliably brought into contact with the groove bottom 8 of the outer peripheral groove 1d of the outer ring 1 (the peaks 18 of the knurled pattern).

[0063] Furthermore, since the insulating coating 5 is fixed to the outer ring 1 by contact between the insulating coating 5 and the knurled peaks 18, the fixing strength of the insulating coating 5 to the outer ring 1 is high, and it is possible to reliably prevent the insulating coating 5 and the outer ring 1 from moving relative to each other in the circumferential and axial directions during bearing rotation. Other effects are the same as in the first embodiment.

[0064] Figure 9 shows an insulated rolling bearing according to a fourth embodiment of the present invention. The fourth embodiment differs from the first embodiment in that annular recesses 23 are formed at both axial ends of the inner circumference of the outer ring 1, but the other configurations are basically the same. Therefore, the same reference numerals are used for parts corresponding to the first embodiment and their descriptions are omitted.

[0065] The inner circumference of the outer ring 1 has an outer ring raceway groove 6, a pair of outer ring shoulder surfaces 24 adjacent to the outer ring raceway groove 6 on the axially outer side, and a pair of annular recesses 23 adjacent to the outer ring shoulder surfaces 24 on the axially outer side. The outer ring shoulder surfaces 24 are cylindrical inner surfaces with a constant inner diameter along the axial direction. The annular recesses 23 are recesses that are recessed radially outward from the outer ring shoulder surfaces 24, and are formed in an annular shape that opens to the axial end face 1c of the outer ring 1 and extends in the circumferential direction. These annular recesses 23 are formed in an L-shape in cross-section, having an inner recess surface 25 extending axially inward from the radially inner end of the axial end face 1c of the outer ring 1, and a recess side surface 26 extending radially inward from the axially inner end of the inner recess surface 25.

[0066] The insulating coating 5 has an inner diameter extension 27 that extends radially inward from the radially inner end of the end face coating portion 5c. The inner diameter extension 27 faces the recess side surface 26 of the annular recess 23 in the axial direction with a gap between them. The axial distance between the axial outer surface of the end face coating portion 5c and the recess side surface 26 is greater than the thickness of the insulating coating 5.

[0067] In this embodiment, the insulated rolling bearing has annular recesses 23 formed at both axial ends of the inner circumference of the outer ring 1, and the inner diameter extension portion 27 of the insulating coating 5 is positioned facing the outer ring 1 axially with a gap between it and the recessed side surface 26 of the annular recess 23. This allows for a large axial creepage distance between the outer ring 1 and the stepped portion 14 on the inner circumference of the housing 12 (see Figure 3), which is positioned by abutting the axial end face 1c of the outer ring 1, thereby effectively preventing surface discharge between the outer ring 1 and the housing 12.

[0068] Figure 10 shows an insulated rolling bearing according to a fifth embodiment of the present invention. The fifth embodiment differs from the fourth embodiment only in the configuration of the inner diameter extension portion 27; the other configurations are basically the same. Therefore, the same reference numerals are used for parts corresponding to the fourth embodiment, and their description is omitted.

[0069] As shown on the left side of Figure 10, the annular recess 23 is formed in an L-shape in cross-section, having an inner circumferential surface 25 of the recess extending axially inward from the radially inner end of the axial end face 1c of the outer ring 1, and a recess side surface 26 extending radially inward from the axially inner end of the inner circumferential surface 25. Here, the inner circumferential surface 25 of the recess is formed inclined radially outward with respect to the axially inward direction.

[0070] As shown on the right side of Figure 10, the inner diameter extension portion 27 of the insulating coating 5 is bent axially inward from the radial inner end of the end face coating portion 5c so as to cover the inner surface of the annular recess 23 (the inner circumferential surface 25 of the recess and the side surface 26 of the recess), and is formed in an L-shape in cross-section along the inner circumferential surface 25 of the recess and the side surface 26 of the recess. This L-shaped inner diameter extension portion 27 can be formed in an L-shape in cross-section by pressing the inner diameter extension portion 27 into the annular recess 23 with a heated annular jig 28, and then cooling the inner diameter extension portion 27 and the jig 28 in that state to lower the temperature.

[0071] In this embodiment, the insulated rolling bearing has annular recesses 23 formed at both axial ends of the inner circumference of the outer ring 1, and an inner diameter extension 27 covering the inner surface of the annular recesses 23 is provided on the insulating coating 5. This allows for a large axial creepage distance between the outer ring 1 and the stepped portion 14 on the inner circumference of the housing 12 (see Figure 3), which is positioned by abutting the axial end face 1c of the outer ring 1. This effectively prevents surface discharge between the outer ring 1 and the housing 12. In particular, since the inner diameter extension 27 is formed in an L-shape in cross-section along the inner circumferential surface 25 of the recess and the side surface 26 of the recess, it is possible to secure a large creepage distance.

[0072] Furthermore, as shown on the left side of Figure 10, the inner circumferential surface 25 of the recess is inclined radially outward toward the axially inward direction. Therefore, as shown on the right side of Figure 10, when the jig 28 is pressed against the insulating coating 5 to form an L-shaped cross-section, it is possible to reliably prevent the insulating coating 5 from interfering with and being damaged by the inner circumferential surface 25 of the recess, resulting in excellent formability of the inner diameter extension portion 27 of the insulating coating 5.

[0073] In the embodiments described above, balls were used as the rolling elements 3, but other shapes of rolling elements 3, such as cylindrical rollers, may also be used.

[0074] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0075] 1 Outer ring 1a Outer surface 1b Chamfered section 1c Axial end face 1d outer groove 2 Inner ring 3 Rolling element 5. Insulating coating 5a Outer sheathing part 5b Chamfered coating 5c End covering part 5d Outer perimeter groove covering 8 groove bottom 9 groove side 10 Air pockets 15 Groove bottom surface 16 The Thief 17 Air pockets 18 Yamabe 19 Tanibe 20 Air pockets 23 Annular recess 25 Inner surface of recess 26 Recessed side 27 Inner diameter extension

Claims

1. Outer ring (1) and, An inner ring (2) is positioned radially inward of the outer ring (1), A plurality of rolling elements (3) are incorporated between the outer ring (1) and the inner ring (2), The outer ring (1) has a resin insulating coating (5) provided on it. In an insulated rolling bearing in which the insulating coating (5) is made of a heat-shrinkable resin that shrinks when heated, The outer ring (1) has a cylindrical outer surface (1a) with a constant outer diameter along the axial direction, a pair of chamfered portions (1b) with a circular arc cross-section whose outer diameter gradually decreases axially outward from the outer surface (1a), a pair of axial end faces (1c) extending radially inward from the pair of chamfered portions (1b), and an outer groove (1d) extending circumferentially through the axial center of the outer surface (1a). The insulating rolling bearing is characterized in that the insulating coating (5) has a cylindrical outer circumferential coating portion (5a) that covers the outer circumferential surface (1a) of the outer ring (1), a pair of chamfered coating portions (5b) with an arc cross-section that cover the pair of chamfered portions (1b) of the outer ring (1), a pair of end face coating portions (5c) that cover the pair of axial end faces (1c) of the outer ring (1), and an outer groove coating portion (5d) that covers the outer groove (1d) in a recessed state relative to the outer circumferential coating portion (5a).

2. The insulating rolling bearing according to claim 1, wherein the outer circumferential groove covering portion (5d) is in contact with the groove bottom (8) of the outer circumferential groove (1d).

3. The insulating rolling bearing according to claim 2, wherein an air reservoir (10) is formed between the groove side surface (9) of the outer circumferential groove (1d) and the outer circumferential groove covering portion (5d).

4. The groove bottom (8) has a cylindrical groove bottom surface (15) having a constant groove bottom diameter along the axial direction, and a pair of recessed portions (16) that extend circumferentially adjacent to both sides of the groove bottom surface (15) and have a smaller diameter than the groove bottom surface (15). The insulating rolling bearing according to claim 2, wherein the outer circumferential groove covering portion (5d) is in contact with the groove bottom surface (15), and an air reservoir (17) is formed between the inner surface of the recessed portion (16) and the outer circumferential groove covering portion (5d).

5. A knurled pattern is formed on the groove bottom (8), in which peaks (18) and valleys (19) are arranged alternately. The insulating rolling bearing according to claim 2, wherein the outer circumferential groove covering portion (5d) contacts the apex of the peak portion (18), and an air reservoir (20) is formed between the inner surface of the valley portion (19) and the outer circumferential groove covering portion (5d).

6. An insulated rolling bearing according to any one of claims 2 to 5, wherein the groove depth of the outer peripheral groove (1d) from the outer peripheral surface (1a) is set to 0.2 mm or more and 1.0 mm or less.

7. Annular recesses (23) are formed at both axial ends of the inner circumference of the outer ring (1), opening to the axial end faces (1c) of the outer ring (1) and extending in the circumferential direction. The insulating rolling bearing according to any one of claims 1 to 5, wherein the insulating coating (5) further has an inner diameter extension (27) that extends radially inward from the radial inner end of the end face coating portion (5c) and faces the inner surface of the annular recess (23) in the axial direction with a gap between them.

8. Annular recesses (23) are formed at both axial ends of the inner circumference of the outer ring (1), opening to the axial end faces (1c) of the outer ring (1) and extending in the circumferential direction. The insulating rolling bearing according to any one of claims 1 to 5, wherein the insulating coating (5) further has an inner diameter extension (27) formed by bending the radial inner end of the end face coating (5c) in an axial direction so as to cover the inner surface of the annular recess (23).

9. The annular recess (23) is formed in an L-shape in cross-section, having an inner circumferential surface (25) of the recess extending axially inward from the radially inner end of the axial end face (1c) of the outer ring (1), and a recessed side surface (26) extending radially inward from the axially inner end of the inner circumferential surface (25). The insulating rolling bearing according to claim 8, wherein the inner diameter extension portion (27) is also formed in an L-shaped cross-section along the inner circumferential surface (25) of the recess and the side surface (26) of the recess.

10. The insulating rolling bearing according to claim 9, wherein the inner circumferential surface (25) of the recess is formed to be inclined radially outward with respect to the axially inward direction.

11. The insulating rolling bearing according to any one of claims 1 to 5, wherein the groove width of the outer peripheral groove (1d) is set to be 25% or more of the width dimension between the pair of axial end faces (1c) of the outer ring (1).

Images