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 ensure sufficient creepage distance. [Solution] In an insulated rolling bearing in which the insulating coating 5 is formed of a heat-shrinkable tube 13 that shrinks when heated, 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 end face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1, and a pair of inner circumferential coating portions 5d that cover a pair of inner circumferential surfaces 1d of the outer ring 1.

Description

Technical Field

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

Background Art

[0002] In a rolling bearing that supports a 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, a rolling bearing having insulation with an insulating coating provided on the outer ring is known (for example, Patent Document 1).

[0003] The rolling bearing having insulation of Patent Document 1 includes 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 a mold, so there is a problem that the manufacturing cost of the rolling bearing having insulation increases.

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

[0006] The rolling bearing having insulation of Patent Document has a heat-shrinkable tube disposed radially outside the outer ring, and by heating and shrinking the heat-shrinkable tube, a resin insulating coating that covers the outer peripheral surface and a pair of axial end faces of the outer ring is formed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-15667 [Patent Document 2] Japanese Patent Publication No. 2001-107974 [Overview of the project] [Problems that the invention aims to solve]

[0008] The inventors of this invention fabricated an insulated rolling bearing in which the insulating coating of the outer ring was formed with heat-shrinkable tubing, as shown in Patent Document 2, and evaluated its insulating performance. As a result, it was found that simply shrinking the heat-shrinkable tubing to form the insulating coating may not be sufficient to secure the creepage distance L between the housing and the outer ring.

[0009] In other words, as shown in Figure 9, a rolling bearing is used in which a plurality of rolling elements 33 are incorporated between an outer ring 31 and an inner ring 32. By heating and shrinking a heat-shrinkable tube placed on the outer diameter side of the outer ring 31 of the rolling bearing, an insulating coating 34 is obtained that covers the cylindrical outer diameter surface and a pair of axial end faces of the outer ring 31.

[0010] Furthermore, if this insulated rolling bearing is assembled into a housing 37 having a cylindrical inner circumferential surface 35 and an inner end surface 36 extending radially inward from the inner circumferential surface 35, as shown in Figure 9, and the outer ring 31 is positioned axially by pressing the axial end surface of the outer ring 31 against the inner end surface 36 of the housing 37, the creepage distance L (the shortest distance along the surface of the insulator between the two conductors) between the outer ring 31 and the housing 37 becomes equal to the thickness of the insulating coating 34, and there is a risk that a sufficient creepage distance L cannot be secured.

[0011] Therefore, the inventor investigated how to ensure sufficient creepage distance in an insulated rolling bearing with an insulating coating formed from heat-shrinkable tubing. As a result of this investigation, the inventor focused on the property of heat-shrinkable tubing that, when heated to a high temperature, it simply shrinks without external force, but when an external force is applied while it is heated to a high temperature, it can be deformed in accordance with that external force, and furthermore, when cooled to a lower temperature while in that deformed state, it can maintain that deformed shape. The inventor then conceived the idea that by placing the heat-shrinkable tubing radially on the outer side of the outer ring, and when heating and shrinking the tubing, using a jig to push a part of the heat-shrinkable tubing radially inward from the inner surface of the outer ring to deform it, and then cooling it in that state to lower the temperature, it would be possible to cover the inner circumference of the outer ring with a part of the heat-shrinkable tubing.

[0012] The problem this invention aims to solve is to provide an insulated rolling bearing that has low manufacturing costs and can ensure sufficient creepage distance. [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 bearing 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 a pair of inner circumferential surfaces extending axially inward from the radially inner ends of the pair of axial end faces, The insulating rolling bearing is characterized in that the insulating coating comprises a cylindrical outer coating portion that covers the outer 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 a pair of inner-circumferential coating portions that extend axially inward from the radially inner ends of the pair of end-face coating portions and cover the pair of inner circumferential surfaces of the outer ring.

[0014] This configuration allows for the formation of an insulating coating by placing a heat-shrinkable tube radially outside the outer ring and heating and deforming the tube, thus eliminating the need for large-scale equipment like insert molding to provide an insulating coating to the outer ring. This reduces the manufacturing cost of the insulated rolling bearing. Furthermore, since the pair of axial end faces of the outer ring and the pair of inner circumferential surfaces extending axially inward from the radially inward ends of these axial end faces are covered by the end face covering portion and the inner circumferential covering portion of the insulating coating, respectively, when the insulated rolling bearing is assembled into a housing having a cylindrical inner circumferential surface and an inner end face extending radially inward from that inner circumferential surface, and the outer ring is positioned axially by pressing the axial end face of the outer ring against the inner end face of the housing, it is possible to ensure sufficient creepage distance between the outer ring and the housing.

[0015] [Configuration 2] The insulating rolling bearing according to configuration 1, wherein the insulating coating is made by heating and deforming a heat-shrinkable tube having an inner diameter of 103% or less of the outer diameter of the outer ring.

[0016] By adopting this configuration, a heat-shrinkable tube with an inner diameter of 103% or less of the outer diameter of the outer ring (i.e., a heat-shrinkable tube with an inner diameter the same as or close to the outer diameter of the outer ring) is used as the insulating coating, which is deformed by heating. This prevents the load-side portion of the insulating coating from being compressed in the thickness direction and stretched in the circumferential direction when the insulated rolling bearing is used under high temperature conditions, and prevents the formation of wrinkles on the non-load-side portion of the insulating coating.

[0017] [Configuration 3] The insulating rolling bearing according to Configuration 1 or 2, wherein the arc radius of the chamfered portion of the outer ring is set to be at least twice the thickness of the chamfered covering portion.

[0018] [Configuration 4] The insulating rolling bearing according to any one of Configurations 1 to 3, wherein the insulating coating has a withstand voltage of 200 V or more and an insulation resistance value of 1 MΩ or more.

[0019] When this configuration is adopted, when used as an insulating rolling bearing that supports the rotating shaft of an electric motor for driving an electric vehicle or a speed reducer of the electric motor, it is possible to effectively prevent electric corrosion from occurring on the outer ring, inner ring, and rolling elements.

[0020] In the present invention, as a method for manufacturing the above-described insulating rolling bearing, the following configurations are also provided. [Configuration 5] A bearing preparation step of preparing 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 having 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 outer side in the axial direction, a pair of axial end faces extending radially inward from the pair of chamfered portions, and a pair of inner peripheral surfaces extending axially inward from the radially inner ends of the pair of axial end faces; [[ID=二十]]A heat shrink tube arrangement step of arranging a resin heat shrink tube that shrinks by heating on the radially outer side of the rolling bearing; After the heat shrink tube arrangement step, a heat shrink tube heating step of heating and deforming the heat shrink tube to form an insulating coating having a cylindrical outer peripheral covering portion covering the outer peripheral surface of the outer ring, a pair of chamfered covering portions having a cross-sectional arc shape covering the pair of chamfered portions of the outer ring, a pair of end face covering portions covering the pair of axial end faces of the outer ring, and a pair of inner peripheral covering portions extending axially inward from the radially inner ends of the pair of end face covering portions and covering the pair of inner peripheral surfaces of the outer ring. In the heat-shrinkable tube heating step, a pair of jigs having an annular wall axially opposed to the axial end face of the outer ring and an annular projection protruding axially from the radially inner end of the annular wall are used. The portion of the heat-shrinkable tube corresponding to the inner circumferential covering portion is pushed radially inward of the inner circumferential surface of the outer ring by the annular projections of the pair of jigs, and the inner circumferential covering portion is formed by cooling in that state. A method for manufacturing an insulated rolling bearing.

[0021] [Configuration 6] In the heat-shrinkable tube heating step, the portion of the heat-shrinkable tube corresponding to the end face covering portion is pressed against the axial end face of the outer ring by the annular walls of the pair of jigs, and the end face covering portion is formed by cooling in that state. The method for manufacturing an insulated rolling bearing according to Configuration 5.

[0022] When this configuration is adopted, it becomes possible to make the end face covering portion of the insulating coating adhere closely to the axial end face of the outer ring.

[0023] [Configuration 7] As the pair of jigs, those having a surface in contact with the heat-shrinkable tube formed of an elastomer or a rubber material are used. The method for manufacturing an insulated rolling bearing according to Configuration 5 or 6.

[0024] When this configuration is adopted, since the surface of the jig in contact with the heat-shrinkable tube is formed of an elastomer or a rubber material, it is possible to prevent the heat-shrinkable tube from being damaged due to contact with the jig and ensure the insulating performance of the insulating coating formed by the heat-shrinkable tube.

[0025] [Configuration 8] In the heat-shrinkable tube arranging step, as the heat-shrinkable tube, one having an inner diameter of 103% or less of the outer diameter of the outer ring is used. The method for manufacturing an insulated rolling bearing according to any one of Configurations 5 to 7.

Advantages of the Invention

[0026] 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 the pair of axial end faces of the outer ring and the pair of inner circumferential surfaces extending axially inward from the radially inward ends of the pair of axial end faces are covered by the end face covering portion and the inner circumferential covering portion of the insulating coating, respectively, when the insulated rolling bearing is assembled into a housing having a cylindrical inner circumferential surface and an inner end face extending radially inward from that inner circumferential surface, and the outer ring is positioned axially by pressing the axial end face of the outer ring against the inner end face of the housing, it is possible to ensure a creepage distance between the outer ring and the housing. [Brief explanation of the drawing]

[0027] [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] Flowchart showing the manufacturing method of the insulated rolling bearing shown in Figure 1. [Figure 4] Figure 2 illustrates the manufacturing method of an insulated rolling bearing, showing a state in which a heat-shrinkable tube, placed radially outward on the outer circumference of the outer ring, has been heated and shrunk. [Figure 5] Figure 4 shows a heat-shrinkable tube deformed by applying external force with a pair of jigs. [Figure 6] Figure 5 shows another example of the jig. [Figure 7] This diagram shows the state in which the heat shrink tubing is placed radially outward on the outer circumference of the outer ring before heating. [Figure 8] Figure 2 illustrates the creepage distance when an insulated rolling bearing is assembled into a housing. [Figure 9] This diagram illustrates the creepage distance when an insulated rolling bearing is assembled into a housing, as shown in the reference example. [Modes for carrying out the invention]

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The outer ring 1 has a cylindrical outer surface 1a whose outer diameter does not change along the axial direction and remains constant, 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 a pair of inner circumferential surfaces 1d extending axially inward from the radially inner ends of the pair of axial end faces 1c.

[0032] The axial end face 1c of the outer ring 1 is a plane perpendicular to the axial direction. The inner circumferential surface 1d of the outer ring 1 is a cylindrical surface with a constant inner diameter along the axial direction, and is formed continuously from the radial inner end of the axial end face 1c to the outer ring raceway groove 6. The intersection of the axial end face 1c and the inner circumferential surface 1d of the outer ring 1 is chamfered (a minute chamfer of less than 1 mm).

[0033] The retainer 4 employs a steel plate retainer in which a pair of opposing corrugated annular bodies 11, each having alternating arc-shaped pocket wall portions 8 for holding the rolling elements 3 and flat plate portions 10 with axially penetrating rivet holes 9 formed therein, are joined together by rivets 12 inserted into the rivet holes 9. By employing this steel plate retainer, the axial length of the portion of the inner circumferential surface 1d of the outer ring 1 that does not radially face the outer circumference of the retainer 4 can be made longer. This prevents the jig 15 (see Figure 5) from interfering with the retainer 4 when forming the inner circumferential covering portion 5d described later, and makes it easier to secure the axial length of the portion of the inner circumferential surface 1d of the outer ring 1 that will be covered by the inner circumferential covering portion 5d.

[0034] The outer diameter φD (see Figure 7) of the outer circumferential surface 1a of the outer ring 1 is set to 45 mm or more and 110 mm or less, and the axial width dimension of the outer ring 1 is set to 9 mm or more and 30 mm or less. Furthermore, the surface roughness of the outer circumferential surface 1a of the outer ring 1 along the axial direction is set to Ra 0.05 μm or more and 1.6 μm or less (preferably Ra 0.25 μm or more and 1.0 μm or less). The arc radius of the chamfered portions at both axial ends of the outer circumferential surface 1a of the outer ring 1 is set to 0.3 mm or more (preferably 0.5 mm or more) and 4.0 mm or less. The size of this arc radius is at least twice the thickness of the chamfered coating portion 5b of the insulating coating 5, which will be described later.

[0035] 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, a pair of end face coating portions 5c that cover a pair of axial end faces 1c of the outer ring 1, and a pair of inner circumferential coating portions 5d that cover a pair of inner circumferential surfaces 1d 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, 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, and the pair of inner circumferential coating portions 5d are formed extending axially inward from the radially inner ends of the pair of end face coating portions 5c. The inner circumferential coating portions 5d are preferably provided in close contact with the inner circumferential surface 1d of the outer ring 1, but may also be provided in a state where they are lifted away from the inner circumferential surface 1d of the outer ring 1 (a state where a radial gap exists between the inner circumferential surface 1d of the outer ring 1 and the inner circumferential coating portion 5d).

[0036] The insulating coating 5 is configured to have a thickness such that the outer periphery coating portion 5a (i.e., the thinnest part among the outer periphery coating portion 5a, chamfered coating portion 5b, end face coating portion 5c, and inner periphery coating portion 5d) has a withstand voltage of 200V or more and an insulation resistance value of 1MΩ or more. This insulating coating 5 is formed from a heat-shrinkable resin tube 13 that shrinks when heated, as will be described later.

[0037] An example of the manufacturing method for this insulated rolling bearing will be explained following the flowchart shown in Figure 3.

[0038] [Bearing preparation process] Prepare the rolling bearing 14 shown in Figure 7. This rolling bearing 14 incorporates multiple rolling elements 3 between the outer ring 1 and the inner ring 2, and does not have the insulating coating 5 shown in Figure 2.

[0039] [Heat shrink tubing placement process] After the bearing preparation process described above, a heat-shrinkable resin tube 13 is placed radially outward of the rolling bearing 14, as shown in Figure 7.

[0040] As the heat-shrinkable tube 13, for example, a resin material such as a polyolefin resin, a polyvinyl chloride resin, or a fluororesin is formed into a tube shape, irradiated with radiation to crosslink the resin material, and then stretched in the radial direction (or the radial direction and the axial direction) in a state of being heated to a predetermined high temperature and cooled. In this case, the dimensions of the tube after stretching correspond to the dimensions of the heat-shrinkable tube 13 before shrinking due to heating.

[0041] The heat-shrinkable tube 13 used has an inner diameter φD0 that is 100% or more and 103% or less of the outer diameter φD of the outer peripheral surface 1a of the outer ring 1. Here, in order to facilitate the operation of arranging the heat-shrinkable tube 13 outside the outer ring 1, a heat-shrinkable tube 13 having an inner diameter φD0 that is 100% or more of the outer diameter φD of the outer peripheral surface 1a of the outer ring 1 is used. However, a heat-shrinkable tube 13 having an inner diameter φD0 that is less than 100% of the outer diameter φD of the outer peripheral surface 1a of the outer ring 1 may be used, and the heat-shrinkable tube 13 may be fitted to the outer peripheral surface 1a of the outer ring 1 with an interference fit.

[0042] Also, it is preferable to use the heat-shrinkable tube 13 having a radial shrinkage rate X that satisfies at least (φD0 - φD1) / φD0 < X so that the axial end surface 1c and the inner peripheral surface 1d of the outer ring 1 can be covered with the heat-shrinkable tube 13 in the heat-shrinkable tube heating step described later. Here, the radial shrinkage rate X is the ratio of the decrease amount of the inner diameter of the heat-shrinkable tube 13 when the heat-shrinkable tube 13 is completely shrunk to the inner diameter φD0 of the heat-shrinkable tube 13 before heating and shrinking, and φD1 is the inner diameter of the outer ring 1.

[0043] Also, the axial length W of the heat-shrinkable tube 13 is 1.8 times or more of the axial width dimension (the distance between a pair of axial end surfaces 1c) of the outer ring 1 so that the axial end surface 1c and the inner peripheral surface 1d of the outer ring 1 can be surely covered with the heat-shrinkable tube 13 in the heat-shrinkable tube heating step described later. The thickness t of the heat-shrinkable tube 13 is set to be 1 / 2 or less of the arc radius of the chamfered portion 1b of the outer ring 1.

[0044] [Heat-Shrinkable Tube Heating Step] After the heat shrink tubing placement process described above, the heat shrink tubing 13 is heated to shrink it. As a result, as shown in Figure 4, the portions of the heat shrink tubing 13 corresponding to the outer peripheral covering portion 5a (see Figure 2) and the chamfered covering portion 5b (see Figure 2) come into contact with the outer peripheral surface 1a and the chamfered portion 1b of the outer ring 1, respectively. At the same time, the portions of the heat shrink tubing 13 corresponding to the end covering portion 5c (see Figure 2) and the inner peripheral covering portion 5d (see Figure 2) shrink to a diameter smaller than the outer peripheral surface 1a of the outer ring 1, and face the axial end surface 1c of the outer ring 1 with a gap in between. At this time, both axial ends of the heat shrink tubing 13 are located radially inward from the inner peripheral surface 1d of the outer ring 1. In other words, the axial length W of the heat shrink tubing 13 shown in Figure 7 is set so that both axial ends of the heat shrink tubing 13 in the state shown in Figure 4 are radially inward from the inner peripheral surface 1d of the outer ring 1. The method for heating the heat shrink tubing 13 can include blowing hot air onto the outer circumference of the heat shrink tubing 13 using a heating gun or the like, or passing the rolling bearing 14 and the heat shrink tubing 13, which is positioned radially outside of it, through a heating furnace while supported by a support. The heating temperature of the heat shrink tubing 13 can be set within the range of 80°C to 170°C.

[0045] Next, as shown in Figure 5, while the heat shrink tube 13 is still at a high temperature, an external force is applied to the heat shrink tube 13 using a pair of jigs 15 positioned axially opposite each other with the outer ring 1 in between, thereby deforming the heat shrink tube 13. Here, each jig 15 has an annular wall 16 that faces the axial end face 1c of the outer ring 1 in the axial direction, and an annular projection 17 that protrudes axially from the radially inner end of the annular wall 16. Furthermore, each jig 15 is provided so as to be movable in the axial direction. Then, the annular wall 16 of each jig 15 presses the portion of the heat shrink tube 13 corresponding to the end face covering portion 5c (see Figure 2) against the axial end face 1c of the outer ring 1, and the annular projection 17 of each jig 15 pushes the portion of the heat shrink tube 13 corresponding to the inner circumference covering portion 5d (see Figure 2) radially inward of the inner circumference surface 1d of the outer ring 1. By cooling the heat shrink tube 13 in this state to lower its temperature, the end face covering portion 5c and the inner circumference covering portion 5d shown in Figure 2 are formed.

[0046] Here, the annular wall 16 of each jig 15 has an annular plane perpendicular to the axial direction for pressing the heat shrink tube 13. The annular projection 17 has a cylindrical outer circumference with an outer diameter smaller than the inner circumferential surface 1d of the outer ring 1, and by expanding the diameter of the portions at both axial ends of the heat shrink tube 13 shown in Figure 4 so as to follow the outer circumference of the annular projection 17 shown in Figure 5, it is possible to form the inner circumferential covering portion 5d shown in Figure 2. The inner circumference of the annular projection 17 shown in Figure 5 is a tapered surface that gradually increases in diameter towards the tip of the annular projection 17, thereby preventing interference between the annular projection 17 and the retainer 4.

[0047] Each jig 15 has a surface that contacts the heat shrink tubing 13 made of elastomer or rubber material. This prevents damage to the heat shrink tubing 13 due to contact with the jig 15 and ensures the insulating performance of the insulating coating 5 formed by the heat shrink tubing 13. Preferably, the elastomer or rubber material has a heat resistance of 100°C or higher. As shown in Figure 5, it is possible to form the entire jig 15 out of elastomer or rubber material, but as shown in Figure 6, it is also possible to form only the part of each jig 15 that contacts the heat shrink tubing 13 out of elastomer or rubber material, and the rest out of metal. This is preferable because it allows for a balance between the overall rigidity of the jig 15 and the flexibility of the part of the jig 15 that contacts the heat shrink tubing 13.

[0048] As described above, in the heat shrink tube heating process, the heat shrink tube 13 shown in Figure 7 is heated to shrink it as shown in Figure 4. Then, while the heat shrink tube 13 is still heated and at a high temperature, an external force is applied to the heat shrink tube 13 using a pair of jigs 15 as shown in Figure 5 to deform it, and then it is cooled in that deformed state to lower the temperature, thereby forming 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 an arc cross-section that covers 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 a pair of inner peripheral coating portions 5d that cover a pair of inner peripheral surfaces 1d of the outer ring 1.

[0049] As shown in Figure 8, the insulated rolling bearing of this embodiment can be used as a rolling bearing to support the rotating shaft 18 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 8, the insulated rolling bearing is incorporated between the housing 19 and the rotating shaft 18. The housing 19 has a cylindrical inner circumferential surface 20 into which the outer circumference of the outer ring 1 fits, and an inner end surface 21 extending radially inward from the inner circumferential surface 20. The radial inner end of the inner end surface 21 is located at the same radial position as or radially inward from the inner circumferential surface 1d of the outer ring 1. The outer ring 1 is positioned axially such that its axial end surface 1c is pressed against the inner end surface 21 of the housing 19.

[0050] As shown in Figure 2, in this insulated rolling bearing, the pair of axial end faces 1c of the outer ring 1 and the pair of inner circumferential surfaces 1d extending axially inward from the radially inner ends of the pair of axial end faces 1c are covered by the end face covering portion 5c and the inner circumferential covering portion 5d of the insulating coating 5, respectively. Therefore, as shown in Figure 8, when the outer ring 1 is assembled into the housing 19 and positioned axially by pressing the axial end faces 1c of the outer ring 1 against the inner end face 21 of the housing 19, it is possible to secure a creepage distance L between the outer ring 1 and the housing 19.

[0051] Furthermore, as shown in Figure 7, this insulated rolling bearing can be manufactured by placing a heat-shrinkable tube 13 radially outside the outer ring 1 and forming an insulating coating 5 by heating and deforming the heat-shrinkable tube 13, as shown in Figures 4 and 5. This eliminates the need for large-scale equipment, such as when an insulating coating is applied to the outer ring 1 by insert molding. Therefore, it is possible to reduce the manufacturing cost of the insulated rolling bearing.

[0052] Furthermore, this insulated rolling bearing uses a heat-shrinkable tube 13 as the insulating coating 5 shown in Figure 2, which has an inner diameter φD0 that is 103% or less of the outer diameter φD of the outer ring 1 (i.e., a heat-shrinkable tube 13 with an inner diameter φD0 that is the same as or close to the outer diameter φD of the outer ring 1), and is deformed by heating, so that when the insulated rolling bearing is used under high temperature conditions such as 80°C, the load-side portion of the insulating coating 5 is not compressed in the thickness direction and stretched in the circumferential direction, and wrinkles do not occur on the non-load-side portion of the insulating coating 5.

[0053] Furthermore, since the insulating coating 5 shown in Figure 2 has a withstand voltage of 200V or more and an insulating resistance of 1MΩ or more, this insulated rolling bearing can effectively prevent electrolytic corrosion from occurring on the outer ring 1, inner ring 2, and rolling elements 3 when used as an insulated rolling bearing to support the rotating shaft 18 of the electric motor or the reduction gear of the electric motor for driving an electric vehicle.

[0054] Furthermore, as shown in Figure 5, this insulated rolling bearing uses the annular walls 16 of a pair of jigs 15 to press the portion of the heat-shrinkable tube 13 corresponding to the end face covering portion 5c (see Figure 2) against the axial end face 1c of the outer ring 1, and cools in that state to form the end face covering portion 5c of the insulating coating 5 shown in Figure 2. This makes it possible to have the end face covering portion 5c in close contact with the axial end face 1c of the outer ring 1.

[0055] 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 (i.e., the axial end face 1c of the outer ring 1 and the axial end face 2b 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 2b of the inner ring 2.

[0056] 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.

[0057] 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]

[0058] 1 Outer ring 1a Outer surface 1b Chamfered section 1c Axial end face 1d Inner surface 2 Inner ring 3 Rolling element 5. Insulating coating 5a Outer sheathing part 5b Chamfered coating 5c End covering part 5d Inner circumferential coating 13 Heat shrink tubing 14 Rolling bearings 15 Jig 16 Ring Wall 17 Annular projection φD Outer diameter φD0 inner diameter

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 (13) that shrinks when heated, the bearing 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 outward from the outer surface (1a) in the axial direction, a pair of axial end faces (1c) extending radially inward from the pair of chamfered portions (1b), and a pair of inner circumferential surfaces (1d) extending axially inward from the radially inner ends of the pair of axial end faces (1c), 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 a circular 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 a pair of inner circumferential coating portions (5d) that extend axially inward from the radially inner ends of the pair of end face coating portions (5c) and cover the pair of inner circumferential surfaces (1d) of the outer ring (1).

2. The insulating coating (5) has an inner diameter (φD) that is 103% or less of the outer diameter (φD) of the outer ring (1). ０ An insulating rolling bearing according to claim 1, which is made by heating and deforming a heat-shrinkable tube (13) having ).

3. The insulating rolling bearing according to claim 1 or 2, wherein the arc radius of the chamfered portion (1b) of the outer ring (1) is at least twice the thickness of the chamfered covering portion (5b).

4. The insulating rolling bearing according to claim 1 or 2, wherein the insulating coating (5) has a withstand voltage of 200V or more and an insulating resistance of 1MΩ or more.

5. A bearing preparation step to prepare a rolling bearing (14) 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 circular arc cross-section whose outer diameter gradually decreases toward the axially outward direction from the outer surface (1a), a pair of axial end faces (1c) extending radially inward from the pair of chamfered portions (1b), and a pair of inner surface (1d) extending axially inward from the radially inward end of the pair of axial end faces (1c), A heat shrink tube placement step is to place a heat shrink tube (13) made of resin that shrinks when heated on the radially outer side of the rolling bearing (14), The process includes a heat shrink tube heating step, in which the heat shrink tube (13) is heated and deformed to form an insulating coating (5) having 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), a pair of end face coating portions (5c) that cover the pair of axial end faces (1c) of the outer ring (1), and a pair of inner peripheral coating portions (5d) that extend axially inward from the radially inner ends of the pair of end face coating portions (5c) and cover the pair of inner peripheral surfaces (1d) of the outer ring (1). A method for manufacturing an insulated rolling bearing, wherein in the heat shrink tube heating step, a pair of jigs (15) are used, each having an annular wall (16) facing the axial end face (1c) of the outer ring (1) in the axial direction, and an annular projection (17) projecting in the axial direction from the radially inner end of the annular wall (16). The annular projection (17) of the pair of jigs (15) is used to push the portion of the heat shrink tube (13) corresponding to the inner circumferential covering portion (5d) radially inward from the inner circumferential surface (1d) of the outer ring (1), and the inner circumferential covering portion (5d) is formed by cooling in that state.

6. The method for manufacturing an insulated rolling bearing according to claim 5, wherein in the heat shrink tube heating step, the annular wall (16) of the pair of jigs (15) presses the portion of the heat shrink tube (13) corresponding to the end face covering portion (5c) against the axial end face (1c) of the outer ring (1), and the end face covering portion (5c) is formed by cooling in that state.

7. The method for manufacturing an insulated rolling bearing according to claim 5 or 6, wherein the pair of jigs (15) have surfaces that come into contact with the heat shrinkable tube (13) formed of elastomer or rubber material.

8. In the heat shrink tube placement step, the heat shrink tube (13) has an inner diameter (φD) that is 103% or less of the outer diameter (φD) of the outer ring (1). ０ A method for manufacturing an insulated rolling bearing according to claim 5 or 6, using a bearing having ).

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