Insulated rolling bearing and method for manufacturing an insulated rolling bearing

Abstract

To provide an insulated rolling bearing that has low manufacturing costs and can suppress creep. [Solution] The insulating coating 5 has a cylindrical outer coating portion 5a that covers the outer circumferential surface 1a of the outer ring 1, a pair of chamfered coating portions 5b with a circular arc cross-section that cover a pair of chamfered portions 1b of the outer ring 1, and a pair of end-face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1, and thickened portions 8 that extend in an annular shape in the circumferential direction have a thickness greater than the thickness at the axial center of the outer coating portion 5a.

Description

Technical Field

[0001] This invention relates to an insulated rolling bearing and a method for manufacturing the insulated rolling bearing.

Background Art

[0002] In a rolling bearing that supports the rotating shaft of a device that uses 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 includes an outer ring, an inner ring disposed radially inward of 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 inside 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 disposing a resin heat-shrinkable tube on the radially outer side of the outer ring and heating and shrinking the heat-shrinkable tube to form a resin insulating coating that covers the outer peripheral surface and a pair of axial end surfaces of the outer ring. [Prior art documents] [Patent 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] By the way, when the rotating shaft of an electric motor or alternator is supported by a rolling bearing, a phenomenon called creep can occur where the outer ring of the rolling bearing gradually rotates relative to the housing.

[0009] In other words, rolling bearings that support the rotating shafts of electric motors, alternators, etc., have the inner ring on the rotating side and the outer ring on the non-rotating side. Therefore, they are used in a state where the inner ring is fitted to the outer circumference of the rotating shaft in an interference fit, and the outer ring is fitted to the inner circumference of the housing in a clearance fit. In this case, when the bearing rotates, minute circumferential slip accumulates between the housing and the outer ring, which are fitted in a clearance fit, and a creep phenomenon may occur in which the outer ring gradually rotates relative to the housing.

[0010] The inventors of the present invention considered suppressing the above-mentioned creep phenomenon with heat-shrinkable tubing. Specifically, they investigated whether the above-mentioned creep phenomenon could be suppressed by using heat-shrinkable tubing when a rotating shaft such as an electric motor or alternator is supported by an insulated rolling bearing with an insulating coating formed using heat-shrinkable tubing, as described in Patent Document 2.

[0011] As a result of the investigation, we came up with the idea that instead of using the most common type of heat shrink tubing, which has unidirectional heat shrinkage (i.e., shrinks only in the radial direction when heated and hardly shrinks in the axial direction), which allows for easy dimensional control during heat shrinkage, if we use one with bidirectional heat shrinkage (i.e., shrinks simultaneously in both the radial and axial directions when heated), it will be possible to form thickened sections that extend in annular shape in the circumferential direction at both axial ends of the portion covering the outer surface of the outer ring of the insulating coating, with a thickness greater than the axial center of the portion covering the outer surface of the insulating coating. The portions between these thickened sections will function as relief grooves to suppress creep, thereby suppressing creep in the outer ring.

[0012] The problem this invention aims to solve is to provide an insulated rolling bearing that has low manufacturing costs and can suppress creep. [Means for solving the problem]

[0013] 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 tube 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, and a pair of axial end faces extending radially inward from the pair of chamfered portions. The insulating coating comprises a cylindrical outer covering portion that covers the outer surface of the outer ring, a pair of chamfered covering portions with a circular arc cross-section that cover the pair of chamfered portions of the outer ring, and a pair of end covering portions that cover the pair of axial end faces of the outer ring. An insulated rolling bearing characterized in that thickened portions extending in annular shape in the circumferential direction are formed at both axial ends of the outer peripheral covering portion, with a thickness greater than the thickness at the axial center of the outer peripheral covering portion.

[0014] This configuration allows for the formation of an insulating coating by placing a heat-shrinkable tube radially outward on the outer ring and heating and deforming the tube. This eliminates the need for large-scale equipment, such as insert molding, when insulating the outer ring. As a result, the manufacturing cost of the insulated rolling bearing can be reduced. Furthermore, since thickened sections extending in annular shape in the circumferential direction are formed at both axial ends of the outer circumferential coating, with a thickness greater than the thickness at the axial center of the outer circumferential coating, the portion between these thickened sections (the axial center portion of the outer circumferential coating) functions as a relief groove to suppress creep caused by contact between the elastically deformed portion of the outer ring due to the force received from the rolling elements and the housing, thereby suppressing creep of the outer ring.

[0015] [Configuration 2] The insulating rolling bearing according to configuration 1, wherein the outer peripheral covering portion has bidirectional thermal shrinkage properties, shrinking simultaneously in both the axial and radial directions when removed from the outer peripheral surface of the outer ring and heated.

[0016] The above configuration is obtained by placing a heat-shrinkable resin tube, which has bidirectional heat shrinkage properties that cause it to shrink simultaneously in both the radial and axial directions when heated, on the radially outer side of the outer ring, and then heating and deforming the heat-shrinkable tube to form an insulating coating.

[0017] Furthermore, this invention also provides the following configuration as a method for manufacturing the insulated rolling bearing described above. [Configuration 3] Prepare a rolling bearing having an outer ring, an inner ring disposed radially inward of the outer ring, and a plurality of rolling elements incorporated between the outer ring and the inner ring, wherein the outer ring has a cylindrical outer peripheral surface with a constant outer diameter along the axial direction, a pair of chamfered portions having a cross-sectional arc shape whose outer diameter gradually decreases from the outer peripheral surface toward the outside in the axial direction, and a pair of axial end surfaces extending radially inward from the pair of chamfered portions; A heat shrink tube arrangement step of disposing, outside the rolling bearing in the radial direction, a heat shrink tube having two-way heat shrinkability that shrinks simultaneously in both the axial and radial directions by heating; After the heat shrink tube arrangement step, heat and deform the heat shrink tube to form a resin insulation coating having a cylindrical outer peripheral coating portion covering the outer peripheral surface of the outer ring, a pair of chamfered coating portions having a cross-sectional arc shape covering the pair of chamfered portions of the outer ring, and a pair of end surface coating portions covering the pair of axial end surfaces of the outer ring. The method includes a heat shrink tube heating step; In the heat shrink tube heating step, after the axial shrinkage of the portion corresponding to the outer peripheral coating portion of the heat shrink tube is restricted by the inner circumference of the heat shrink tube contacting the outer peripheral surface of the outer ring, heat and shrink the portions corresponding to the chamfered coating portion and the end surface coating portion of the heat shrink tube in the axial and radial directions, so as to form, at both axial ends of the outer peripheral coating portion, a thick portion extending annularly in the circumferential direction with a thickness greater than the thickness at the central position in the axial direction of the outer peripheral coating portion. A method for manufacturing an insulated rolling bearing;

[0018] [Configuration 4] The method for manufacturing an insulated rolling bearing according to Configuration 3, wherein in the heat shrink tube heating step, an end surface heater disposed axially opposite to the pair of axial end surfaces of the outer ring is used to heat the portion corresponding to the end surface coating portion of the heat shrink tube with the end surface heater.

[0019] When this configuration is adopted, since an end face heater arranged axially opposite to a pair of axially end faces of the outer ring is used, the portions corresponding to the chamfered covering portion and the end face covering portion of the heat shrinkable tube are heated and shrunk intensively, and the thicknesses of the chamfered covering portion and the end face covering portion can be increased. As a result, it becomes possible to effectively increase the thicknesses of the thick portions at both axially ends of the outer peripheral covering portion.

[0020] [Configuration 5] In the heat shrinkable tube arranging step, the method for manufacturing an insulated rolling bearing according to Configuration 3 or 4, wherein a heat shrinkable tube having an inner diameter of 103% or less of the outer diameter of the outer ring is used as the heat shrinkable tube.

[0021] When this configuration is adopted, in the heat shrinkable tube arranging step, since a heat shrinkable tube having an inner diameter of 103% or less of the outer diameter of the outer ring (that is, a heat shrinkable tube having an inner diameter equal to or close to the outer diameter of the outer ring) is used as the heat shrinkable tube, the amount of axial shrinkage generated in the heat shrinkable tube can be significantly suppressed from the start of heating of the heat shrinkable tube until the inner circumference of the heat shrinkable tube contacts the outer peripheral surface of the outer ring. Therefore, the amount of axial shrinkage generated in the portions corresponding to the chamfered covering portion and the end face covering portion of the heat shrinkable tube after the inner circumference of the heat shrinkable tube contacts the outer peripheral surface of the outer ring can be ensured, and the thicknesses of the chamfered covering portion and the end face covering portion can be increased. As a result, it becomes possible to effectively increase the thicknesses of the thick portions at both axially ends of the outer peripheral covering portion.

[0022] [Configuration 6] In the heat shrinkable tube arranging step, the method for manufacturing an insulated rolling bearing according to any one of Configurations 3 to 5, wherein a heat shrinkable tube (10) having an axial length of 1.6 times or more the axial width dimension of the outer ring (1) is used.

[0023] When this configuration is adopted, since the axial length of the heat shrinkable tube is long, when the heat shrinkable tube is axially shrunk by heating, it becomes possible to surely cover the axial end faces of the outer ring with the heat shrinkable tube. [Advantages of the Invention]

[0024] The insulated rolling bearing of this invention can form an insulating coating by placing a heat-shrinkable tube radially outside the outer ring and heating and deforming the heat-shrinkable tube, thus eliminating the need for large-scale equipment such as insert molding to provide an insulating coating to the outer ring. Therefore, it is possible to reduce the manufacturing cost of the insulated rolling bearing. Furthermore, since thickened sections are formed at both axial ends of the outer circumferential coating, extending in an annular shape in the circumferential direction with a thickness greater than the thickness at the axial center of the outer circumferential coating, the portion between these thickened sections (the axial center portion of the outer circumferential coating) functions as a relief groove to suppress creep caused by the elastic deformation of the outer ring due to the force received from the rolling elements contacting the housing, thereby suppressing creep of the outer ring. [Brief explanation of the drawing]

[0025] [Figure 1] Cross-sectional view showing an insulated rolling bearing according to an embodiment of this invention. [Figure 2] Cross-sectional view along line II-II in Figure 1 [Figure 3] Figure 2 shows a magnified view of the area near the chamfered portion of the outer ring. [Figure 4] Flowchart showing the manufacturing method of the insulated rolling bearing shown in Figure 1. [Figure 5] Figure 2 illustrates the manufacturing method of an insulated rolling bearing, showing the state in which the heat-shrinkable tubing is placed radially outward on the outer circumference of the outer ring before shrinking. [Figure 6] Figure 5 shows the state where the inner circumference of the heat-shrinkable tube is in contact with the outer surface of the outer ring after it has been heated and shrunk. [Figure 7] Figure 6 shows the state after further heating and shrinking the heat-shrinkable tubing shown in Figure 6, covering the chamfered portion and axial end face of the outer ring with the heat-shrinkable tubing. [Figure 8] Figure 7 shows a pair of end-face heaters positioned axially opposite each other with the outer ring shown in Figure 7 in between, and the end-face heaters heating the portion of the heat shrink tube along the axial end face of the outer ring shown in Figure 7. [Figure 9] Figure 8 shows another example of the end face heater. [Figure 10] Figure 2 shows an example of an insulated rolling bearing being incorporated into an electrical device. [Modes for carrying out the invention]

[0026] Figure 1 shows an insulated rolling bearing according to an 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 assembled 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.

[0027] 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 of the outer ring 1 and inner ring 2 that approaches the axial center along the axial direction, and the axial outer side is the side of the outer ring 1 and inner ring 2 that moves away from the axial center along the axial direction.

[0028] As shown in Figure 2, 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.

[0029] The outer ring 1 has a cylindrical outer surface 1a with a constant outer diameter that does not change along the axial direction, a pair of chamfered portions 1b with a cross-sectional arc shape whose outer diameter gradually decreases axially outward from the outer surface 1a, and a pair of axial end faces 1c extending radially inward from the pair of chamfered portions 1b. The axial end faces 1c are planes perpendicular to the axial direction.

[0030] The outer diameter of the outer circumferential surface 1a of the outer ring 1 is set to be between 45 mm and 110 mm, and the width dimension of the pair of axial end faces 1c of the outer ring 1 is set to be between 9 mm and 30 mm. Furthermore, the surface roughness of the outer circumferential surface 1a of the outer ring 1 along the axial direction is set to be between Ra 0.05 μm and 1.6 μm (preferably between Ra 0.25 μm and 1.0 μm). 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 its arc radius is set to be 0.3 mm or more (preferably 0.5 mm or more).

[0031] 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 a circular arc cross-section that cover a pair of chamfered portions 1b of the outer ring 1, and a pair of end-face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1. The pair of chamfered coating portions 5b are formed in conjunction with both axial ends of the outer circumferential coating portion 5a, and the pair of end-face coating portions 5c are formed in conjunction with the radially inner ends of the pair of chamfered coating portions 5b. It is preferable that the end-face coating portions 5c are provided in close contact with the axial end faces 1c of the outer ring 1, but they may also be provided in a state where they are lifted away from the axial end faces 1c of the outer ring 1 (a state where there is a gap between the axial end faces 1c of the outer ring 1 and the end-face coating portions 5c).

[0032] At both axial ends of the outer peripheral coating 5a, thickened portions 8 are formed that extend in annular shape in the circumferential direction and have a thickness greater than the thickness at the axial center of the outer peripheral coating 5a. Note that in the figure, the thickness of the insulating coating 5 is greatly exaggerated for clarity.

[0033] As shown in Figure 3, the thickened portion 8 is adjacent to the chamfered coating portion 5b of the outer peripheral coating portion 5a, and has a shape in which the thickness gradually decreases toward the axially inward direction (left side in the figure). Preferably, the thickness of the thickened portion 8 is 10 μm or more greater than the thickness of the outer peripheral coating portion 5a at the axial center position. The thickness of the insulating coating 5 is set so that it has a withstand voltage of 200 V or more and an insulation resistance of 1 MΩ or more at the axial center position of the outer peripheral coating portion 5a (i.e., the thinnest position). This insulating coating 5 is formed of a heat-shrinkable resin tube that shrinks when heated, as will be described later.

[0034] An example of the manufacturing method for this insulated rolling bearing will be explained following the flow chart shown in Figure 4.

[0035] [Bearing preparation process] Prepare the rolling bearing 9 shown in Figure 5. This rolling bearing 9 has multiple rolling elements 3 incorporated between the outer ring 1 and the inner ring 2 (see Figure 2), and does not have the insulating coating 5 shown in Figure 2.

[0036] [Heat shrink tubing placement process] After the bearing preparation process described above, a resin heat-shrinkable tube 10 is placed on the radially outer side of the rolling bearing 9, as shown in Figure 5. Heat-shrinkable tubes 10 generally come in two types: those with unidirectional heat shrinkage (which shrink only in the radial direction when heated, and hardly shrink in the axial direction; specifically, those with an axial shrinkage rate of 10% or less, as described later) and those with bidirectional heat shrinkage (which shrink simultaneously in both the radial and axial directions when heated). The former type of heat-shrinkable tube is the most common and allows for easy dimensional control during heat shrinkage, but in this embodiment, the latter type of heat-shrinkable tube 10 is used.

[0037] The heat shrink tubing 10 used has an axial shrinkage rate (the ratio of the decrease in the axial length of the heat shrink tubing 10 when it is completely shrunk to the axial length of the heat shrink tubing 10 before shrinking) of 15% or more (preferably 20% or more, more preferably 25% or more). Furthermore, the radial shrinkage rate (the ratio of the decrease in the inner diameter of the heat shrink tubing 10 when it is completely shrunk to the inner diameter of the heat shrink tubing 10 before shrinking) of 40% or more is used. The axial length of the heat shrink tubing 10 before shrinking is set to 1.6 times or more (preferably 1.8 times or more) the axial width dimension of the outer ring 1 (the distance between a pair of axial end faces 1c) of the outer ring 1, so that when the heat shrink tubing 10 is shrunk axially by heating in the heat shrink tubing heating process described later, the heat shrink tubing 10 can reliably cover the axial end faces 1c of the outer ring 1.

[0038] As the heat-shrinkable tube 10, for example, a tube made from a resin material such as polyolefin resin, polyvinyl chloride resin, or fluororesin can be formed, irradiated with an electron beam to crosslink the resin material, and then heated to a predetermined high temperature, stretched in both the axial and radial directions, and cooled. In this case, the dimensions of the stretched tube correspond to the dimensions of the heat-shrinkable tube 10 before shrinking, and the dimensions of the tube before stretching correspond to the dimensions of the heat-shrinkable tube 10 when it has been completely shrunk by heating.

[0039] Furthermore, the heat shrink tubing 10 used has an inner diameter that is between 100% and 103% of the outer diameter of the outer surface 1a of the outer ring 1. Here, in order to facilitate the process of placing the heat shrink tubing 10 on the outside of the outer ring 1, a heat shrink tubing 10 with an inner diameter of 100% or more of the outer diameter of the outer surface 1a of the outer ring 1 is used. However, a heat shrink tubing 10 with an inner diameter of less than 100% of the outer diameter of the outer surface 1a of the outer ring 1 may also be used, and the heat shrink tubing 10 may be fitted onto the outer surface 1a of the outer ring 1 with an overlap.

[0040] [Heat shrink tube heating process] After the heat shrink tubing placement step described above, as shown in Figures 6 and 7, the heat shrink tubing 10 is heated and deformed to form an insulating coating 5, as shown in Figure 2, which has a cylindrical outer peripheral coating portion 5a that covers the outer peripheral surface 1a of the outer ring 1, a pair of chamfered coating portions 5b with a circular arc cross-section that cover a pair of chamfered portions 1b of the outer ring 1, and a pair of end-face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1. As a method for heating the heat shrink tubing 10, a method of blowing hot air onto the outer circumference of the heat shrink tubing 10 with a heating gun or the like can be used, or a method of passing the rolling bearing 9 and the heat shrink tubing 10, which is positioned radially outside of it, through a heating furnace while being supported by a support. The heating temperature of the heat shrink tubing 10 can be set in the range of 70°C to 180°C (preferably 150°C or less).

[0041] When the heat shrink tube 10 is heated and shrunk, first, as shown in Figure 6, the inner circumference of the portion of the heat shrink tube 10 facing the radially outer side of the outer ring 1 comes into contact with the outer surface 1a of the outer ring 1. The frictional force acting on the contact portion between the heat shrink tube 10 and the outer ring 1 restricts the axial shrinkage of the portion of the heat shrink tube 10 corresponding to the outer covering portion 5a.

[0042] Subsequently, if the heating of the heat shrink tube 10 is continued, as shown in Figures 6 and 7, the portion of the heat shrink tube 10 that protrudes axially from the contact portion with the outer ring 1 (the portion corresponding to the chamfered covering portion 5b and the end face covering portion 5c shown in Figure 2) shrinks further in the axial and radial directions due to the heat, covering the chamfered portion 1b and the axial end face 1c of the outer ring 1. At this time, as the portion corresponding to the chamfered covering portion 5b shown in Figure 2 shrinks axially, the thickness of the chamfered covering portion 5b increases, and the thickness of the portions at both axial ends of the outer peripheral covering portion 5a connected to the chamfered covering portion 5b also increases. As a result, thickened portions 8 are formed at both axial ends of the outer peripheral covering portion 5a, extending in an annular shape in the circumferential direction with a thickness greater than the thickness at the axial center of the outer peripheral covering portion 5a.

[0043] Here, as shown in Figure 8, end face heaters 11 are positioned axially opposite to a pair of axial end faces 1c (see Figure 2) of the outer ring 1. When the portion of the heat shrink tube 10 corresponding to the end face covering portion 5c is heated by the end face heaters 11, the portions of the heat shrink tube 10 corresponding to the chamfered covering portion 5b and the end face covering portion 5c are heated intensively and shrunk, thereby increasing the thickness of the chamfered covering portion 5b and the end face covering portion 5c. As a result, it is possible to effectively increase the thickness of the walled portions 8 at both axial ends of the outer peripheral covering portion 5a shown in Figure 2. As the end face heater 11 shown in Figure 8, a hot air type that blows hot air axially or a far-infrared type that radiates far-infrared rays axially can be used. Alternatively, as shown in Figure 9, a contact type (such as a high-temperature jig that is movable in the axial direction) that directly contacts and heats the portion of the heat shrink tube 10 corresponding to the end face covering portion 5c may be used as the end face heater 11.

[0044] Furthermore, if a heat shrink tube 10 with an inner diameter of 103% or less of the outer diameter of the outer ring 1 (i.e., a heat shrink tube 10 with an inner diameter the same as or close to the outer diameter of the outer ring 1) is used as the heat shrink tube 10 before heating as shown in Figure 5, the amount of axial shrinkage that occurs in the heat shrink tube 10 from the start of heating until the inner circumference of the heat shrink tube 10 contacts the outer surface 1a of the outer ring 1, as shown in Figure 6, can be kept small. As a result, as shown in Figures 6 and 7, the amount of axial shrinkage that occurs in the parts of the heat shrink tube 10 corresponding to the chamfered covering portion 5b and the end covering portion 5c after the inner circumference of the heat shrink tube 10 contacts the outer surface 1a of the outer ring 1 can be secured, and the thickness of the chamfered covering portion 5b and the end covering portion 5c can be increased. As a result, it becomes possible to effectively increase the thickness of the walled portions 8 at both axial ends of the outer covering portion 5a.

[0045] As shown in Figure 10, the insulated rolling bearing of this embodiment can be used as a rolling bearing to support the rotating shaft 12 of an electrical device (such as the rotating shaft of an electric motor, the rotating shaft of a speed reducer that reduces the rotation of an electric motor, or the rotating shaft of an alternator). In Figure 10, the insulated rolling bearing is installed between the cylindrical inner circumference of a housing hole 14 formed in a non-rotating housing 13 and the outer circumference of the rotating shaft 12 located at the center of the housing hole 14. Here, the inner ring 2 is the rotating side and the outer ring 1 is the non-rotating side, so the insulated rolling bearing is installed in a state where the inner ring 2 is fitted to the outer circumference of the rotating shaft 12 in an interference fit, and the outer ring 1 is fitted to the inner circumference of the housing hole 14 in a clearance fit. In this case, there is a problem that when the bearing rotates, minute circumferential slip accumulates between the housing 13 and the outer ring 1, which are fitted in a clearance fit state, and a creep phenomenon may occur in which the outer ring 1 gradually rotates relative to the housing 13.

[0046] To address this problem, the insulated rolling bearing of this embodiment has thickened portions 8 extending annularly in the circumferential direction at both axial ends of the outer peripheral covering portion 5a, with a thickness greater than the thickness at the axial center of the outer peripheral covering portion 5a. The portion between these thickened portions 8 (the axial center portion of the outer peripheral covering portion 5a) functions as a relief groove to suppress creep caused by the elastic deformation of the outer ring 1 due to the force received from the rolling elements 3 contacting the housing 13. Therefore, it is possible to suppress creep of the outer ring 1. Here, in order to secure the relief groove, it is preferable to apply lubricating oil to the outer circumference of the outer peripheral covering portion 5a before assembling the insulated rolling bearing into the housing 13. In this way, the lubricating oil present between the thickened portions 8 of the outer peripheral covering portion 5a forms an oil film between the housing 13 and the outer ring 1, and the squeeze effect of this oil film makes it possible to effectively suppress the creep phenomenon of the outer ring 1.

[0047] Furthermore, as shown in Figures 5 to 7, this insulated rolling bearing can be manufactured by placing a heat-shrinkable tube 10 radially outside the outer ring 1 and heating and deforming the heat-shrinkable tube 10 to form the insulating coating 5. This eliminates the need for large-scale equipment, such as when the insulating coating 5 is applied to the outer ring 1 by insert molding. Therefore, it is possible to reduce the manufacturing cost of the insulated rolling bearing.

[0048] Here, as shown in Figures 5 to 7, a heat-shrinkable resin tube 10 having bidirectional heat shrinkage properties, which shrink simultaneously in both the radial and axial directions when heated, is placed on the radially outer side of the outer ring 1. When the heat-shrinkable tube 10 is heated and deformed, an insulating coating 5 is formed. The outer peripheral coating portion 5a of the insulating coating 5 then has bidirectional heat shrinkage properties, shrinking simultaneously in both the axial and radial directions when removed from the outer peripheral surface 1a of the outer ring 1 and heated.

[0049] In the above embodiment, as shown in Figure 2, the axial width dimension of the outer ring 1 and the axial width dimension of the inner ring 2 are the same (that is, the axial end face 1c of the outer ring 1 and the axial end face 2c of the inner ring 2 are at the same axial position). However, it is also possible to set the axial width dimension of the outer ring 1 to be smaller than the axial width dimension of the inner ring 2 so that the surface of the end face covering portion 5c of the insulating coating 5 is at the same axial position as the axial end face 2c of the inner ring 2.

[0050] Furthermore, although the above embodiment described an example in which balls are used as the rolling elements 3, other shapes of rolling elements 3, such as cylindrical rollers, may also be used.

[0051] 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]

[0052] 1 Outer ring 1a Outer surface 1b Chamfered section 1c Axial end face 2 Inner ring 2c Axial end face 3 Rolling element 5. Insulating coating 5a Outer sheathing part 5b Chamfered coating 5c End covering part 8 Thick part 9 Rolling bearings 10 Heat shrink tubing 11 End face heater

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 formed of a heat-shrinkable tube (10) 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), and a pair of axial end faces (1c) extending radially inward from the pair of chamfered portions (1b). The insulating coating (5) has a cylindrical outer peripheral coating portion (5a) that covers the outer peripheral surface (1a) of the outer ring (1), a pair of chamfered coating portions (5b) with a circular arc cross-section that cover the pair of chamfered portions (1b) of the outer ring (1), and a pair of end face coating portions (5c) that cover the pair of axial end faces (1c) of the outer ring (1). An insulated rolling bearing characterized in that thickened portions (8) extending in an annular shape in the circumferential direction are formed at both axial ends of the outer peripheral covering portion (5a), with a thickness greater than the thickness at the axial center of the outer peripheral covering portion (5a).

2. The insulating rolling bearing according to claim 1, wherein the outer peripheral covering portion (5a) has bidirectional thermal shrinkage properties, shrinking simultaneously in both the axial and radial directions when removed from the outer peripheral surface (1a) of the outer ring (1) and heated.

3. A bearing preparation step to prepare a rolling bearing (9) having an outer ring (1), an inner ring (2) arranged radially inward of the outer ring (1), and a plurality of rolling elements (3) incorporated between the outer ring (1) and the inner ring (2), wherein 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 cross-sectional arc shape whose outer diameter gradually decreases axially outward from the outer surface (1a), and a pair of axial end faces (1c) extending radially inward from the pair of chamfered portions (1b), A heat shrink tube placement step is to place a heat shrink tube (10) made of resin having bidirectional heat shrinkability, which shrinks simultaneously in both the axial and radial directions when heated, on the radially outer side of the rolling bearing (9), The process includes a heat shrink tube heating step, in which the heat shrink tube (10) is heated and deformed to form an insulating coating (5) having a cylindrical outer peripheral covering portion (5a) that covers the outer peripheral surface (1a) of the outer ring (1), a pair of chamfered covering portions (5b) with a circular arc cross-section that cover the pair of chamfered portions (1b) of the outer ring (1), and a pair of end-face covering portions (5c) that cover the pair of axial end faces (1c) of the outer ring (1). A method for manufacturing an insulated rolling bearing, wherein in the heat shrink tube heating step, the inner circumference of the heat shrink tube (10) comes into contact with the outer surface (1a) of the outer ring (1), thereby limiting the axial shrinkage of the portion of the heat shrink tube (10) corresponding to the outer peripheral covering portion (5a). Subsequently, the portions of the heat shrink tube (10) corresponding to the chamfered covering portion (5b) and the end face covering portion (5c) are heated to shrink them in the axial and radial directions, thereby forming thickened portions (8) that extend in an annular shape in the circumferential direction with a thickness greater than the thickness at the axial center of the outer peripheral covering portion (5a).

4. The method for manufacturing an insulated rolling bearing according to claim 3, wherein in the heat shrink tube heating step, end face heaters (11) are arranged axially opposite to a pair of axial end faces (1c) of the outer ring (1), and the portion of the heat shrink tube (10) corresponding to the end face covering portion (5c) is heated with the end face heaters (11).

5. The method for manufacturing an insulated rolling bearing according to claim 3 or 4, wherein in the heat shrink tube placement step, the heat shrink tube (10) has an inner diameter that is 103% or less of the outer diameter of the outer ring (1).

6. The method for manufacturing an insulated rolling bearing according to claim 3 or 4, wherein in the heat shrink tube placement step, the heat shrink tube (10) has an axial length of 1.6 times or more the axial width dimension of the outer ring (1).

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