Insulated bearing

Abstract

In this insulating bearing, a mill scale surface is formed on at least a part of a contact surface of a bearing ring on which a resin layer is formed, the contact surface being in contact with the resin layer. Alternatively, instead of the mill scale surface, the surface roughness in the circumferential direction is roughened to Ra 3.2 μm or more or Sa 3.2 μm or more. As a result, the relative sliding between an outer ring and inner ring and an insulating film in the insulating bearing coated with the insulating film and the damage between the two surfaces due to the relative sliding can be prevented, and the deterioration of bearing accuracy and the occurrence of electrolytic corrosion can be suppressed for a longer period of time.

Description

[Technical Field]

[0001] The present invention relates to an insulated bearing that is mounted, for example, on a rotating shaft of a motor, a generator, or the like, and is particularly suitable for mounting on a site where current may flow. [Background Art]

[0002] Conventionally, in equipment provided with a rotating body, a metal bearing is mounted on the rotating shaft in order to reduce frictional resistance generated by the rotation. For example, also in a motor that rotates a rotating body (a so-called rotor) by electromagnetic force, and a generator that generates power by rotating a rotating body (a so-called turbine) with hydraulic power or the like, a bearing is mounted on the rotating shaft of the rotating body.

[0003] In these motors, generators, and the like, there is a problem that current leaks to the bearing, and corrosion caused by the flow of current (hereinafter referred to as "electric corrosion") easily progresses. Accordingly, various techniques for preventing electric corrosion of bearings have been studied.

[0004] For example, Patent Document 1 discloses an electric corrosion-resistant rolling bearing having an insulating coating containing axially oriented fibers on the surface of an outer ring or an inner ring. Further, Patent Document 2 discloses a rolling bearing including a conductive shield and an insulating coating. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021-220613 [Patent Document 2] U.S. Patent No. 9581203 Specification [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] However, in insulated bearings, such as those described in Patent Documents 1 and 2, in which the outer and inner rings are covered with an insulating coating, no mechanical restraining force is generated on the insulating coating in the circumferential direction of the outer and inner rings. The insulating coating is held to the outer and inner rings only by frictional force. Therefore, when rotating under high loads, especially high radial loads, relative slippage may occur between the outer and inner rings and the insulating coating. If significant relative slippage occurs, sliding occurs at specific points between the outer and inner rings and the insulating coating, leading to uneven wear and deterioration of bearing accuracy. Furthermore, there are concerns that this may worsen gear tooth contact, acoustics, and vibration performance in components to which the insulated bearing is applied.

[0007] The present invention has been made in view of the above problems, and aims to provide an insulated bearing that can prevent relative sliding between the outer ring and inner ring and the insulating coating in an insulated bearing coated with an insulating coating, and damage between the two surfaces caused thereby, thereby suppressing deterioration of bearing accuracy and the occurrence of electrolytic corrosion for a longer period of time. [Means for solving the problem]

[0008] The inventors of this invention conducted extensive research to solve the above problems and, as a result, discovered that relative slippage between the outer ring, inner ring, and the resin layer can be prevented by roughening the surface of the parts that come into contact with the resin layer, which is the insulating coating of the outer ring and inner ring, or by specifying the roundness and coaxiality of the outer ring and inner ring. This led to the completion of the present invention.

[0009] In other words, the insulating bearing according to the present invention has the configuration shown in [1] below.

[0010] [1] An insulating bearing comprising a pair of raceway rings having a pair of raceway surfaces, a plurality of rolling elements held to roll freely between the pair of raceway surfaces, and a retainer that holds the rolling elements to roll freely, wherein the contact surfaces of the raceway rings with the mating member are coated with a resin layer, An insulating bearing in which a black scale surface is formed on at least a portion of the contact surface of the raceway ring that is covered with the resin layer and is in contact with the resin layer.

[0011] Furthermore, preferred embodiments of the present invention relating to insulating bearings are described in the following [2]-[3]. [2] The insulating bearing according to [1], wherein at least a portion of the circumferential portion of the contact surface of the raceway ring on which the resin layer is formed, which is in contact with the resin layer, has a roundness of 30 μm or more. [3] The insulating bearing according to [1] or [2], wherein at least two or more circumferential portions of the contact surface of the raceway ring on which the resin layer is formed have a coaxiality of 20 μm or more.

[0012] Furthermore, the insulating bearing according to the present invention has the configuration shown in [4] below.

[0013] [4] An insulating bearing comprising a pair of raceway rings having a pair of raceway surfaces, a plurality of rolling elements held rotatably between the pair of raceway surfaces, and a retainer that holds the rolling elements rotatably, wherein the contact surfaces of the raceway rings with mating members are coated with a resin layer, An insulated bearing in which at least a portion of the contact surface of the raceway ring on which the resin layer is formed, which is in contact with the resin layer, has a circumferential surface roughness of Ra 3.2 μm or more, or Sa 3.2 μm or more. [Effects of the Invention]

[0014] The insulating bearing of the present invention prevents relative sliding between the outer ring and inner ring and the resin layer, and the resulting damage between the two surfaces, by roughening the contact surfaces of the outer ring and inner ring with the resin layer, and by specifying the roundness and coaxiality of the outer ring and inner ring. This suppresses deterioration of bearing accuracy and the occurrence of electrolytic corrosion over a longer period of time. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is an axial cross-sectional view showing an example of the insulating bearing of the present invention. [Figure 2] Figure 2 is a partially cutaway perspective view of an insulated bearing with a black scale surface formed on the outer ring. [Figure 3] Figures 3(a) and 3(b) show Embodiment 1, where Figure 3(a) is an axial cross-sectional view and Figure 3(b) is a cross-sectional view taken along the line III-III in Figure 3(a). [Figure 4]Figures 4(a) and 4(b) are diagrams showing Embodiment 2, wherein Figure 4(a) is an axial sectional view thereof, and Figure 4(b) is a sectional view taken along line IV-IV in Figure 4(a). [Figure 5] Figures 5(a) and 5(b) are diagrams showing Embodiment 3, wherein Figure 5(a) is an axial sectional view thereof, and Figure 5(b) is a sectional view taken along line V-V in Figure 5(a). [Figure 6] Figures 6(a) and 6(b) are diagrams showing Embodiment 4, wherein Figure 6(a) is an axial sectional view thereof, and Figure 6(b) is a sectional view taken along line VI-VI in Figure 6(a). [Figure 7] Figure 7 is a partially cutaway perspective view showing Embodiment 5. [Figure 8] Figure 8 is a sectional view of a boundary between an outer circumferential surface of an outer ring and a main chamfer in Embodiment 5. [Figure 9] Figure 9 is a partially cutaway perspective view showing Embodiment 6. [Figure 10] Figure 10 is a sectional view of a boundary between an outer circumferential surface of an outer ring and a groove in Embodiment 6. [Figure 11] Figure 11 is a partially cutaway perspective view showing an example of an insulating bearing in which a portion in contact with a resin layer is roughened. [Figure 12] Figures 12(a) to 12(c) are sectional views showing formation modes of a resin layer. [Figure 13] Figures 13(a) and 13(b) are sectional views showing another example of a formation mode of a resin layer. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be specifically described. It should be noted that the present invention is not limited to the embodiments described below.

[0017] • Embodiment 1 Figure 1 is an axial cross-sectional view showing an example of an insulating bearing of the present invention. As shown in the figure, the insulating bearing 10 has an outer ring 1, which is one raceway ring, and an inner ring 2, which is the other raceway ring, arranged concentrically, a plurality of rolling elements, which are balls 3, that are held to roll freely between the raceway grooves (raceway surfaces) 1x of the outer ring 1 and the raceway grooves (raceway surfaces) 2x of the inner ring 2, and a cage 4 that holds the balls 3 to roll freely. The balls 3 are held at equal intervals in the circumferential direction by the cage 4.

[0018] A resin layer 5 is continuously formed to cover the outer circumferential surface 1a of the outer ring 1, the axial sides 1b that are continuous with the outer circumferential surface 1a, and the inner circumferential surface 1c that extends inward from the inner diameter ends of the axial sides 1b. In addition, an annular groove 1c1 is formed along the circumference of the inner circumferential surface 1c of the outer ring 1, and the end of the resin layer 5 is fitted into the annular groove 1c1.

[0019] Furthermore, a resin layer 5 is formed on the inner circumferential surface 2a of the inner ring 2, on both axial side surfaces 2b that are continuous with the inner circumferential surface 2a, and on the outer circumferential surface 2c that extends inward from the outer diameter side ends of both axial side surfaces 2b, and the ends of the resin layer 5 are fitted into the annular groove 2c1 formed on the outer circumferential surface 2c.

[0020] There are no restrictions on the resin that constitutes the resin layer 5, but it is preferable to use a resin that has both insulating properties and heat resistance and durability (mechanical strength). For example, polyphenylene sulfide, polyphthalamide, polyphenylene ether, polyether ether ketone, fluororesin, polyamide, etc. can be suitably used.

[0021] The thickness of the resin layer 5 is preferably 50 μm or more, and more preferably 100 μm or more, in order to ensure insulation. On the other hand, the upper limit of the thickness of the resin layer 5 is preferably 2 mm or less, and more preferably 1 mm or less. Increasing the thickness of the resin layer 5 beyond 2 mm will not further improve insulation and will only lead to increased costs.

[0022] Furthermore, to form the resin layer 5, injection molding using the outer ring 1 or inner ring 2 on which the resin layer 5 is formed as an insert part is simple and preferable. Other methods such as spraying (including thermal spraying), electrostatic coating (powder / liquid), and fluid immersion can also be applied.

[0023] (Formation of black scale surface) In this invention, in order to prevent relative slippage between the outer ring 1 and the inner ring 2 and the resin layer 5, a black scale surface 8 is formed on the parts of the outer ring 1 and the inner ring 2 that are in contact with the resin layer 5. Specifically, for the outer ring 1, a black scale surface 8 is formed on the entire or partial surface of the outer circumferential surface 1a, both axial sides 1b, and the inner circumferential surface 1c including the annular groove 1c1. For the inner ring 2, a black scale surface 8 is formed on the entire or partial surface of the inner circumferential surface 2a, both axial sides 2b, and the outer circumferential surface 2c including the annular groove 2c1. Figure 2 is a partially cutaway perspective view showing an example in which a black scale surface is formed on the outer ring 1. The black scale surface 8 is formed on the outer circumferential surface 1a and the annular groove 1c1 of the outer ring 1, and the resin layer 5 is formed on the surface of the black scale surface 8 by injection molding.

[0024] The black scale surface 8 is an oxide film formed on the steel material by heat treatment, giving it the appearance of being covered with a black layer of metal. In other words, the black scale surface 8 is an unprocessed surface that has not been cut or ground after heat treatment. This black scale has pinholes and irregularities on its surface, making it rough. Therefore, the formation of the black scale surface in the parts that come into contact with the resin layer 5 of the outer ring 1 and inner ring 2 prevents relative slippage between the two.

[0025] (Specifications for roundness or coaxiality) The black surface 8 is formed by heat-treating the outer ring 1 and inner ring 2, which increases the geometric tolerances of the outer ring 1 and inner ring 2, namely the roundness and coaxiality. This allows a circumferential restraining force to act on the resin layer 5, preventing relative slippage. Specifically, the roundness is preferably 30 μm or more, and the coaxiality is preferably 20 μm or more. However, since larger roundness and coaxiality affect the rotation of the bearing, it is preferable that the roundness be 500 μm or less and the coaxiality be 200 μm or less.

[0026] The following describes embodiments of insulating bearings in which the roundness or coaxiality of the outer ring 1 and inner ring 2 is defined by changing the shape of the outer ring 1 and inner ring 2, with reference to Figures 3(a) to 10. In all figures, the magnitude of the roundness or coaxiality of the outer ring 1, inner ring 2, and resin layer 5 is exaggerated for visual clarity. Figures 3(a) to 6(b) show embodiments for roundness, and Figures 7 to 10 show embodiments for coaxiality.

[0027] • Embodiment 2 Figure 3 shows an embodiment in which a resin layer 5 is formed on the outer circumferential surface 1a of an outer ring 1 with high roundness. Figure 3(a) is an axial cross-sectional view, and Figure 3(b) is a cross-sectional view taken along the line III-III in Figure 3(a). As shown in Figure 3(b), the outer circumferential surface 1a of the outer ring 1 (contact surface with the resin layer 5) has a center C1 that is common with the center C of the bearing, and the outer diameter in the left-right direction is larger than the outer diameter in the vertical direction. This diameter difference is the roundness, and if it is 30 μm or more, relative slippage can be effectively prevented. Accordingly, the thickness of the resin layer 5 is thinner in the left-right direction than in the vertical direction so that the outer diameter is round.

[0028] • Embodiment 3 Figure 4 shows an embodiment in which the roundness of the annular groove 1c1 of the outer ring 1 is increased. Figure 4(a) is an axial cross-sectional view thereof, and Figure 4(b) is a cross-sectional view at the position of line IV-IV in Figure 4(a). As shown in Figure 4(b), the annular groove (contact surface with the resin layer 5) 1c1 of the outer ring 1 has a center C1 that is the same as the center C of the bearing, and the groove depth of the annular groove 1c1 is deeper in the left-right direction than in the up-down direction. Accordingly, the thickness of the resin layer 5 inside the annular groove 1c1 is thicker in the left-right direction than in the up-down direction so that the inner diameter is perfectly round.

[0029] • Embodiment 4 Figure 5 shows an embodiment in which a resin layer 5 is formed on the inner circumferential surface 2a of an inner ring 2 with high roundness. Figure 5(a) is an axial cross-sectional view thereof, and Figure 5(b) is a cross-sectional view at the position of line VV in Figure 5(a). As shown in Figure 5(b), the inner circumferential surface 2a of the inner ring 2 (contact surface with the resin layer 5) has a center C2 that is common with the center C of the bearing, and the inner diameter in the vertical direction is smaller than the inner diameter in the horizontal direction. Accordingly, the thickness of the resin layer 5 is thicker in the horizontal direction than in the vertical direction so that the inner diameter is circular.

[0030] • Embodiment 5 Figure 6 shows an embodiment in which the roundness of the annular groove 2c1 of the inner ring 2 is increased. Figure 6(a) is an axial cross-sectional view thereof, and Figure 6(b) is a cross-sectional view at the position of line VI-VI in Figure 6(a). As shown in Figure 6(b), the annular groove (contact surface with the resin layer 5) 2c1 of the inner ring 2 has a center C2 that is the same as the center C of the bearing, and the groove depth of the annular groove 2c1 is deeper in the vertical direction than in the horizontal direction. Accordingly, the thickness of the resin layer 5 is thinner in the horizontal direction than in the vertical direction so that the outer diameter is perfectly round.

[0031] · Embodiment 6 Figures 7 and 8 both show embodiments in which the outer circumferential surface 1a and the main chamfer 1d of the outer ring 1, which have different degrees of coaxiality, become contact surfaces with the resin layer 5. Figure 7 is a partially cutaway perspective view, and Figure 8 is a cross-sectional view at the boundary between the outer circumferential surface 1a and the main chamfer 1d of the outer ring 1. The main chamfer 1d is formed from the outer circumferential surface 1a of the outer ring 1 to the axial side surface 1b. As shown in Figure 8, the thickness of the outer circumferential surface 1a of the outer ring 1 gradually increases from left to right, and the center C1 of the outer circumferential surface 1a of the outer ring 1 is offset to the right with respect to the center C of the bearing. Accordingly, the thickness of the resin layer 5 decreases from left to right so that the outer diameter is a perfect circle.

[0032] As shown in Figure 8, if the distance between the center C1 of the outer circumferential surface 1a of the outer ring 1 and the center C of the bearing is coaxial and 20 μm or more, relative slippage can be effectively prevented.

[0033] • Embodiment 7 Figures 9 and 10 both show embodiments in which the outer circumferential surface 1a and the annular groove 1c1 of the outer ring 1, which have different degrees of coaxiality, become contact surfaces with the resin layer 5. Figure 9 is a partially cutaway perspective view, and Figure 10 is a cross-sectional view at the boundary between the outer circumferential surface 1a and the annular groove 1c1 of the outer ring 1. As shown in Figure 10, the depth of the annular groove 1c1 of the outer ring 1 increases from left to right, and the center C1 of the annular groove 1c of the outer ring 1 is offset to the right with respect to the center C of the bearing. Accordingly, the thickness of the resin layer 5 increases from left to right so that the inner diameter is a perfect circle.

[0034] In embodiments 6 and 7, two or more circumferential portions with different degrees of coaxiality may be formed among the outer circumferential surface 1a, inner circumferential surface 1c, and main chamfer 1d. By making their offset directions different, relative slippage can be prevented more effectively. In other words, in embodiments 2 to 7, the resin layers formed on raceway rings (outer or inner rings) with different degrees of roundness and coaxiality are adjusted in thickness over the circumferential direction so that the circumferential surface (outer or inner surface) of the resin layer in contact with the raceway ring and the circumferential surface (inner or outer surface) on the radially opposite side are perfectly round.

[0035] • Embodiment 8 The above shows the case where a black scale surface 8 is formed, but instead of a black scale surface 8, the portion in contact with the resin layer 5 can also be roughened. Figure 11 is a partially cutaway perspective view showing an example of this, in which the outer circumferential surface 1a of the outer ring 1, the inner circumferential surface 1c including the annular groove 1c1, and the main chamfer 1d are roughened. The resin layer 5 is then formed on these roughened surfaces (1a, 1c, 1d). Due to the anchoring effect of the roughened surface, a restraining force acts in the circumferential direction of the outer ring 1.

[0036] Regarding the degree of surface roughness, if the surface roughness in the circumferential direction of any surface (1a, 1c, 1d) is Ra 3.2 μm or higher, or Sa 3.2 μm or higher, relative slip can be effectively prevented. The means of surface roughening are not limited, and general methods such as machining, shot blasting, and chemical treatment can be used. Therefore, if both Ra and Sa values ​​are too high, the load required for surface roughening will increase, so Ra and Sa are preferably 25.0 μm or lower.

[0037] Furthermore, the present invention is not limited to the embodiments described above, and can be modified, improved, etc., as appropriate. In addition, each embodiment and each modification described herein can be combined and applied to the extent that it is feasible.

[0038] For example, there are no restrictions on the shape of the contact surface between the outer ring 1 and the resin layer 5, or the contact surface between the inner ring 2 and the resin layer 5. For instance, the outer ring 1 can have the cross-sectional shape shown in Figures 12(a) to 13(b).

[0039] As shown in Figures 12(a) to 12(c), the resin layer 5 is bent in a roughly L-shape in cross-section from the portion covering the axial side surface 1b so as to cover the inner circumferential surface 1c of the outer ring 1, and the end of the resin layer 5 is fitted into the annular groove 1c1 in Figures 12(a) and 12(c). The cross-sectional shape of the annular groove 1c1 is a droplet shape with an arc in Figure 12(a) and a hook shape in Figure 12(c). Also, as shown in Figure 12(b), the annular groove 1c1 is optional.

[0040] Furthermore, the main chamfer 1d may be linear, as shown in Figure 12(a), or it may be arc-shaped, as shown in Figures 12(b) and 12(c).

[0041] Alternatively, as shown in Figure 13(a), the annular groove 1c1 of the outer ring 1 may be absent, and the resin layer 5 may be formed up to the inner diameter end of the axial side surface 1b. Furthermore, as shown in Figure 13(b), the resin layer 5 may be formed up to the inner diameter end of the axial side surface 1b without the end of the resin layer 5 reaching the annular groove 1c1. In this case, a sealing member can be attached to the annular groove 1c1.

[0042] This application is based on Japanese Patent Application No. 2023-103604 filed on June 23, 2023, and its contents are incorporated herein by reference. [Explanation of Symbols]

[0043] 1 Outer ring 1a Outer surface of the outer ring 1b Axial side of the outer ring 1c1 Annular groove of the outer ring 1d main chamfer 1x raceway groove (raceway surface) 2 Inner Ring 2a Inner surface of the inner ring 2b Axial side view of the inner ring 2c1 Annular groove of the inner ring 2x raceway groove (raceway surface) 3 Balls (rolling elements) 4 Cage 5. Resin layer 8 Black surface 10 Insulated bearings

Claims

1. In an insulated bearing comprising a pair of raceway rings having a pair of raceway surfaces, a plurality of rolling elements held rotatably between the pair of raceway surfaces, and a retainer that holds the rolling elements rotatably, wherein the contact surfaces of the raceway rings with the mating member are coated with a resin layer, An insulating bearing in which a black scale surface is formed on at least a portion of the contact surface of the raceway ring on which the resin layer is formed, the contact surface with the resin layer.

2. The insulating bearing according to claim 1, wherein at least a portion of the circumferential portion of the contact surface of the raceway ring on which the resin layer is formed, which is in contact with the resin layer, has a roundness of 30 μm or more.

3. The insulating bearing according to claim 1 or 2, wherein at least two or more circumferential portions of the contact surfaces of the raceway ring on which the resin layer is formed, which are in contact with the resin layer, have a coaxiality of 20 μm or more.

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