Insulated rolling bearing and method for manufacturing insulated rolling bearing

Abstract

To provide an insulated rolling bearing capable of simply and efficiently forming an insulating layer on a surface of a component, and to provide a method of manufacturing the insulated rolling bearing.SOLUTION: An insulating rolling bearing 1 includes an inner ring 2, an outer ring 3 coaxially provided on the radial outside of the inner ring 2, a plurality of rolling elements 4 arranged between the inner ring 2 and the outer ring 3, and an insulating layer 6 made of a heat-shrinkable resin provided so as to be in close contact with the outer diameter surface of the outer ring 3. A method for manufacturing an insulating rolling bearing 1 includes a step of inserting a rolling bearing having an inner ring 2, an outer ring 3 coaxially provided on a radially outer side of the inner ring 2, and a plurality of rolling elements 4 arranged between the inner ring 2 and the outer ring 3 into a tubular heat-shrinkable resin before heat shrinkage, and a step of heating the tubular heat-shrinkable resin to thermally shrink the heat-shrinkable resin and forming an insulating layer 6 made of the heat-shrinkable resin in close contact with an outer diameter surface of the outer ring 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an insulating rolling bearing and a method for manufacturing an insulating rolling bearing. [Background technology]

[0002] Rolling bearings such as ball bearings are commonly used to support the rotating shafts of motors, alternators, and other devices. In recent years, inverter control has become commonplace for efficient motor operation. In particular, motors for vehicles are being made smaller to facilitate installation in vehicles, and more precise control is being implemented to use these smaller motors more efficiently.

[0003] It is known that shaft currents and shaft voltages occur on the motor shaft. If these currents pass through the inside of the bearing, electrolytic corrosion may occur in the metal raceways and rolling elements. For this reason, rolling bearings with insulating layers formed thereon are sometimes used to prevent current from passing through the inside of the bearing. For example, in Patent Document 1 listed below, the inner and outer rings are placed in molds, and insulating coatings 6 and 7 are formed on their peripheral surfaces by insert injection molding (see paragraph 0017 and Figure 1 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3068311 Summary of the Invention [Problem to be solved by the invention]

[0005] When forming an insulating coating by insert injection molding as in Patent Document 1, it is necessary to perform pre-processing such as preheating, degreasing, and masking of the bearing (inner ring and outer ring), as well as post-processing such as deburring after resin molding, which requires a lot of time and effort.In addition, because a mold for insert injection molding is required, it is difficult to process many bearings at once, which creates the problem of increased processing costs.

[0006] Therefore, an object of the present invention is to provide an insulating rolling bearing that allows an insulating layer to be formed on the surface of a component part simply and efficiently, and a method for manufacturing the insulating rolling bearing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides: With inner circle, an outer ring provided coaxially on the radially outer side of the inner ring; a plurality of rolling elements disposed between the inner ring and the outer ring; an insulating layer made of heat-shrinkable resin provided so as to be in close contact with the outer diameter surface of the outer ring; An insulating rolling bearing having the above structure was constructed (first structure).

[0008] This eliminates the need for pre-processing such as preheating, degreasing, and masking of the bearing (outer ring), post-processing such as deburring after resin molding, and the need for molds, and it also makes it possible to process a large number of bearings at once, making it possible to easily and efficiently form an insulating layer on the surface of the rolling bearing components.

[0009] In the first configuration, the insulating layer can be configured (second configuration) to extend from the outer diameter surface of the outer ring to the end face in close contact with the outer ring, thereby preventing contact between the outer ring and the housing and ensuring high insulation.

[0010] The second configuration can be replaced with a third configuration in which a shield portion facing the opening between the inner and outer rings extends from the radially inner end of the insulating layer that is in close contact with the end face of the outer ring. This prevents contact between the outer ring and the housing, ensuring a high level of insulation, and also enables the shield portion to shield the opening between the inner and outer rings.

[0011] In the second or third configuration, a configuration (fourth configuration) can be adopted in which the thickness of the insulating layer extending toward the end face of the outer ring is greater than the thickness of the insulating layer covering the outer diameter surface of the outer ring. In this configuration, the outer ring is firmly sandwiched from both sides in the axial direction by the insulating layer on the end face side, which has a greater thickness, thereby improving the adhesion of the insulating layer to the outer ring.

[0012] In the first to fourth configurations, the insulating layer may have a withstand voltage of 200 V or more, or an insulation resistance value of 1 MΩ or more (fifth configuration). In this way, the insulating properties of the insulating layer can prevent electrolytic corrosion of the rolling bearing.

[0013] In order to solve the above problems, the present invention provides: a step of inserting a rolling bearing having an inner ring, an outer ring provided coaxially on the radially outer side of the inner ring, and a plurality of rolling elements disposed between the inner ring and the outer ring into a tubular heat-shrinkable resin before heat shrinking; a step of heating the tubular heat-shrinkable resin to thermally shrink the heat-shrinkable resin and forming an insulating layer made of the heat-shrinkable resin in close contact with the outer diameter surface of the outer ring; A method for manufacturing an insulating rolling bearing having the above features has been configured (sixth configuration).

[0014] This eliminates the need for pre-processing such as preheating, degreasing, and masking of the bearing (outer ring), post-processing such as deburring after resin molding, and the need for molds, and it also makes it possible to process a large number of bearings at once, making it possible to easily and efficiently form an insulating layer on the surface of the rolling bearing components.

[0015] The sixth configuration can be configured (seventh configuration) in which the tubular heat-shrinkable resin has a radial heat shrinkage rate of 40% or more and an axial heat shrinkage rate of 20% or less when heated. In this way, when the heat-shrinkable resin is heat-shrunk, it deforms smoothly to conform to the surface of the outer ring (the outer diameter surface and end faces of the outer ring), ensuring that the insulating layer is in close contact with the surface of the outer ring. [Effects of the Invention]

[0016] The insulating rolling bearing and method for manufacturing an insulating rolling bearing according to the present invention are configured so that a tubular heat-shrinkable resin is applied to the rolling bearing and this heat-shrinkable resin is brought into close contact with the surface of the rolling bearing (outer ring) to form an insulating layer. This eliminates the need for pre-processing such as preheating, degreasing, and masking of the bearing (outer ring), or post-processing such as deburring after resin molding, or for molds, and it is possible to process a large number of bearings at one time, making it possible to simply and efficiently form insulating layers on the surfaces of rolling bearing components. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an embodiment of an insulating rolling bearing according to the present invention; [Figure 2] Cross-sectional view showing the rolling bearing inserted inside the tubular heat-shrinkable resin before heat shrinking [Figure 3] FIG. 2 is a cross-sectional view showing a first modified example of the insulating rolling bearing shown in FIG. 1. [Figure 4] FIG. 2 is a cross-sectional view showing a second modified example of the insulating rolling bearing shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] An insulated rolling bearing 1 according to the present invention will be described with reference to the drawings. As shown in Fig. 1, this insulated rolling bearing 1 comprises an inner ring 2, an outer ring 3 provided coaxially and radially outward of the inner ring 2, a plurality of rolling elements 4 arranged between the inner ring 2 and the outer ring 3, and a cage 5 that holds the plurality of rolling elements 4 at predetermined intervals in the circumferential direction, on the surface of which an insulating layer 6 is formed.

[0019] This insulated rolling bearing 1 is a ball bearing that uses balls (hereinafter designated by the same reference numerals as the rolling elements 4) as the rolling elements 4, and these balls 4 roll in inner ring raceway grooves 7 formed on the outer diameter surface of the inner ring 2 and outer ring raceway grooves 8 formed on the inner diameter surface of the outer ring 3. A motor shaft (not shown) is inserted into the axis of the inner ring 2, and the outer ring 3 is configured to fit into a housing (not shown). Note that the configuration of this invention can also be applied to an insulated rolling bearing 1 that uses rollers as the rolling elements 4. Below, the direction along the rotation axis of the insulated rolling bearing 1 will be referred to as the axial direction, the direction perpendicular to the rotation axis will be referred to as the radial direction, and the direction along the circumference that goes around the rotation axis will be referred to as the circumferential direction.

[0020] The inner ring 2, outer ring 3, and balls 4 are made of steel. The cage 5 is made of steel or resin (such as polyamide resin, polyether ether ketone resin, or polyphenylene sulfide resin). R-shaped portions 9 with a predetermined radius of curvature are formed on both axial ends of the outer diameter surface of the outer ring 3, and these R-shaped portions 9 smoothly connect the outer diameter surface and end face of the outer ring 3.

[0021] The insulating layer 6 is formed by heating a tubular heat-shrinkable resin to shrink it and then adhering it to the surface of the outer ring 3, covering it from the outer diameter surface to the end face. The term "heat-shrinkable resin" refers to a resin that, unlike ordinary resins, has the property of thermally shrinking when heated. This thermal shrinkage is manifested, for example, by a change in crystallinity that accompanies heating. The insulating layer 6 made of heat-shrinkable resin has an inherent compressive residual stress field, which distinguishes it from resin insulating layers formed by other methods, such as injection molding. Examples of heat-shrinkable resin materials that can be used include polyolefins, vinyl chlorides, fluororesins, and silicone resins.

[0022] In this embodiment, the material and thickness of insulating layer 6 are determined so that insulating layer 6 has a withstand voltage of 200 V or more and an insulation resistance of 1 MΩ or more. In this embodiment, a silicone resin is used as the material of the heat-shrinkable resin that forms insulating layer 6, and the thickness of insulating layer 6 after heat shrinkage is set within the range of 0.1 mm to 1.0 mm, thereby achieving the above withstand voltage and insulation resistance values. The withstand voltage can be measured, for example, by the method described in JIS C2110-1, and the insulation resistance can be measured, for example, by the method described in JIS C8711.

[0023] The radially inner end of insulating layer 6 that is in close contact with the end face of the outer ring 3 extends radially inward so as to face the opening between the inner ring 2 and the outer ring 3, and this extended portion functions as a shield part 10 that prevents foreign matter from entering the interior of the bearing. This insulated rolling bearing 1 is lubricated by an external supply of lubricating oil, and the radial extension length of shield part 10 is determined as appropriate, taking into consideration factors such as the foreign matter shielding performance and the amount of lubricating oil supplied to the interior of the bearing.

[0024] A method for manufacturing an insulated rolling bearing 1 according to the present invention will now be described. In this manufacturing method, first, a rolling bearing is assembled, including an inner ring 2, an outer ring 3 disposed coaxially on the radial outside of the inner ring 2, a plurality of balls 4 arranged between the inner ring 2 and the outer ring 3, and a cage 5 that holds the plurality of balls 4 at predetermined intervals in the circumferential direction, and then, as shown in Fig. 2, this rolling bearing is inserted into a tubular heat-shrinkable resin (insulating layer 6) before heat shrinking (insertion step). It is preferable to leave a certain amount of axial length for this tubular heat-shrinkable resin, in order to form the insulating layer 6 and shield portion 10 extending from the outer diameter surface of the outer ring 3 to its end face in the heat-shrinking step described below.

[0025] Next, the tubular heat-shrinkable resin is heated to heat-shrink it, forming an insulating layer 6 made of heat-shrinkable resin in close contact with the outer diameter surface and both end faces of the outer ring 3, and a shield portion 10 at the radially inner end of the insulating layer 6 (heat-shrinking step). During this process, the heat-shrinkable resin first adheres to the entire outer diameter surface of the outer ring 3 as it heat-shrinks. As the heat-shrinkage progresses, it gradually adheres to the end face of the outer ring 3 from its outer diameter side to its inner diameter side, wrapping around the R-machined portion 9. As the heat-shrinkable resin completely adheres to the end face of the outer ring 3, shield portions 10 are formed on the radially inner side of both end faces of the outer ring 3. Finally, the radial length of the shield portion 10 is trimmed to a specified length, completing the insulated rolling bearing 1 shown in Figure 1.

[0026] During this heat shrinking process, the thickness of the heat shrinkable resin (insulating layer 6) increases as the heat shrinkage progresses. That is, the thickness of insulating layer 6 in close contact with the outer diameter surface of outer ring 3 before the heat shrinking process tends to be relatively thin, while the thickness of insulating layer 6 in close contact with the end surface of outer ring 3 after the heat shrinking process tends to be relatively thick. Furthermore, the thickness of shield portion 10, which heat shrinks in a free state without being in close contact with outer ring 3, tends to be even thicker than the thickness of insulating layer 6 in close contact with the end surface of outer ring 3.

[0027] The tubular heat-shrinkable resin can be selected from a variety of materials with various properties. In this embodiment, a silicone-based heat-shrinkable resin is used, which has a heat-shrinkage property in which the radial heat shrinkage rate upon heating is 40% or more and the axial heat shrinkage rate is 20% or less. A heat shrinkage rate of 40%, for example, means that if the dimension before heating is 100, it will heat shrink to a dimension after heating of 60. When a heat-shrinkable resin with this heat shrinkage rate is used, the wall thickness increases by a maximum of approximately 20 to 30% compared to the wall thickness before heating due to heat shrinkage. By using a tubular heat-shrinkable resin with an axial heat shrinkage rate that is as small as possible (preferably 0%), the heat-shrinkable resin is prevented from spreading axially at the end face of the outer ring 3, allowing the heat-shrinkable resin to more smoothly adhere to the end face.

[0028] The above-mentioned insulated rolling bearing 1 and the method for manufacturing the insulated rolling bearing 1 are configured so that a tubular heat-shrinkable resin is applied to the rolling bearing and this heat-shrinkable resin is brought into close contact with the surface of the rolling bearing (outer ring 3) to form the insulating layer 6. This eliminates the need for pre-processing such as preheating and degreasing of the bearing (outer ring 3) or molds, and allows a large number of bearings to be processed at one time, making it possible to form the insulating layer 6 simply and efficiently on the surface of the rolling bearing (outer ring 3).

[0029] Furthermore, in the above-described insulated rolling bearing 1 and method for manufacturing the insulated rolling bearing 1, the insulating layer 6 is configured to extend from the outer diameter surface of the outer ring 3 to the end face so as to be in close contact with the outer ring 3, thereby preventing contact between the outer ring 3 and the housing and ensuring a high level of insulation.

[0030] Furthermore, in the above-described insulated rolling bearing 1 and method for manufacturing the insulated rolling bearing 1, by configuring the radially inner end of the insulating layer 6 that is in close contact with the end face of the outer ring 3 to form a shield part 10 that extends so as to face the opening between the inner ring 2 and the outer ring 3, it is possible to prevent contact between the outer ring 3 and the housing, ensuring a high level of insulation, and to shield the opening between the inner and outer rings 2, 3 with the shield part 10. Furthermore, by shielding the opening with the shield part 10, there is no need to provide a sealing plate as a separate member to close this opening, thereby reducing manufacturing costs.

[0031] Furthermore, in the above-described insulated rolling bearing 1 and method for manufacturing the insulated rolling bearing 1, R-machined portions 9 with a predetermined radius of curvature are formed at both axial ends of the outer diameter surface of the outer ring 3 to smoothly connect the outer diameter surface and the end face, thereby preventing the insulating layer 6 from lifting up at the boundary between the outer diameter surface and the end face and ensuring high adhesion.

[0032] Furthermore, in the above-described insulated rolling bearing 1, the thickness of the insulating layer 6 extending toward the end face of the outer ring 2 is greater than the thickness of the insulating layer 6 covering the outer diameter surface of the outer ring 3, and therefore the outer ring 3 is firmly sandwiched from both sides in the axial direction by the insulating layer 6 on the end face side where it is thicker, thereby improving the adhesion of the insulating layer 6 to the outer ring 3.

[0033] Furthermore, the insulating layer 6 of the insulated rolling bearing 1 is configured to have a withstand voltage of 200 V or more and an insulation resistance of 1 MΩ or more, so the insulating properties of this insulating layer 6 can reliably prevent electrolytic corrosion of the rolling bearing.

[0034] Furthermore, the above-described method for manufacturing insulating rolling bearing 1 employs a tubular heat-shrinkable resin that, when heated, has a radial thermal shrinkage rate of 40% or more and an axial thermal shrinkage rate of 20% or less; therefore, when this heat-shrinkable resin is heat-shrunk, it deforms smoothly to fit along the surface (outer diameter surface and end face) of outer ring 3, enabling insulating layer 6 to be in close contact with the surface of outer ring 3.

[0035] Fig. 3 shows a first modified example of the insulated rolling bearing 1 shown in Fig. 1. The insulated rolling bearing 1 according to the first modified example has the same configuration as that shown in Fig. 1 in that the insulating layer 6 covers the outer diameter surface and end faces of the outer ring 3, but differs in that the shield part 10 does not extend radially inward of the insulating layer 6. In this way, although the shield part 10 does not have the effect of preventing foreign matter from entering the inside of the bearing, it is possible to prevent contact between the outer ring 3 and the housing and ensure a high level of insulation, just as with the configuration shown in Fig. 1.

[0036] Fig. 4 shows a second modified example of the insulated rolling bearing 1 shown in Fig. 1. The insulated rolling bearing 1 according to the second modified example differs from the first modified example shown in Fig. 3 in that the insulating layer 6 covers only the outer diameter surface of the outer ring 3. In the case of a configuration in which a housing fits only onto the outer diameter surface of the outer ring 3 of the insulated rolling bearing 1 and does not come into contact with the end face of the outer ring 3, if the insulating layer 6 is formed only on the outer diameter surface of the outer ring 3, contact between the outer ring 3 and the housing can be prevented and a high level of insulation can be ensured, just as in the configurations shown in Figs. 1 and 3.

[0037] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0038] 2. Inner circle 3 outer ring 4 Rolling elements (balls) 5 Cage 6 insulating layer 10 Shield section

Claims

1. Inner circle (2) and an outer ring (3) provided coaxially on the radially outer side of the inner ring (2); a plurality of rolling elements (4) disposed between the inner ring (2) and the outer ring (3); an insulating layer (6) made of a heat-shrinkable resin provided so as to be in close contact with the outer diameter surface of the outer ring (3); An insulating rolling bearing having

2. 2. An insulating rolling bearing according to claim 1, wherein the insulating layer (6) extends from the outer diameter surface of the outer ring (3) to an end face thereof so as to be in close contact with the outer diameter surface.

3. 3. An insulating rolling bearing according to claim 2, wherein a shield portion (10) facing an opening between the inner ring (2) and the outer ring (3) is extended from a radially inner end portion of the insulating layer (6) that is in close contact with the end face of the outer ring (3).

4. 4. An insulating rolling bearing according to claim 2, wherein the thickness of the insulating layer (6) extending toward the end face of the outer ring (3) is greater than the thickness of the insulating layer (6) covering the outer diameter surface of the outer ring (3).

5. 4. The insulating rolling bearing according to claim 1, wherein the insulating layer (6) has a withstand voltage of 200 V or more, or an insulation resistance value of 1 MΩ or more.

6. a step of inserting a rolling bearing having an inner ring (2), an outer ring (3) provided coaxially on the radially outer side of the inner ring (2), and a plurality of rolling elements (4) arranged between the inner ring (2) and the outer ring (3) into a tubular heat-shrinkable resin before heat shrinking; a step of heating the tubular heat-shrinkable resin to thermally shrink the heat-shrinkable resin and forming an insulating layer (6) made of the heat-shrinkable resin in close contact with the outer diameter surface of the outer ring (3); A method for manufacturing an insulating rolling bearing having the above-mentioned structure.

7. 7. The method for producing an insulating rolling bearing according to claim 6, wherein the tubular heat-shrinkable resin has a thermal shrinkage rate of 40% or more in the radial direction and 20% or less in the axial direction when heated.

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