Rolling bearing with conductive seal

Abstract

To provide a rolling bearing with a conductive seal that can secure stable conductivity between an outer ring and an inner ring via a seal member.SOLUTION: A rolling bearing with a conductive seal includes: a seal member 5 formed of a conductive rubber; and a seal slide contact surface 13 formed so that the seal member 5 comes into slide contact with an inner ring 2. The seal slide contact surface 13 satisfies both Rsk>0 and Rku<3 at the same time where Rsk represents skewness of roughness curve in a direction orthogonal to a circumferential direction and Rku represents kurtosis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rolling bearing with an electrically conductive seal. [Background technology]

[0002] Electric vehicles such as EVs (battery electric vehicles) and HEVs (hybrid electric vehicles) are known as vehicles that use electric motors as a driving force. In these electric vehicles, an inverter is used to convert the DC power of the battery into AC power in order to supply AC power to the electric motor, and the frequency of the AC power supplied to the electric motor is set high in order to increase the efficiency of the electric motor.

[0003] Here, when the frequency of the AC power supplied to an electric motor becomes high, the effect of sudden voltage fluctuations causes leakage flux from the windings of the stator that constitutes the electric motor, generating a potential difference at both ends of the shaft, which makes it easier for current to flow in the rolling bearings that support the main shaft of the electric motor.When current flows through the rolling bearings, sparks are generated between the raceway surface and the rolling elements of the rolling bearings, and these sparks can cause a phenomenon (electrical corrosion) in which damage to the raceway surface gradually progresses.

[0004] A known bearing for preventing this electrolytic corrosion is the conductive sealed rolling bearing described in Patent Document 1. The conductive sealed rolling bearing of Patent Document 1 has an outer ring, an inner ring arranged coaxially on the radial inside of the outer ring, a number of rolling elements incorporated in an annular bearing space formed between the outer ring and the inner ring, and an annular seal member that closes one axial end opening of the bearing space. The seal member is fixed to the inner circumference of the outer ring, and a seal sliding surface with which the seal lip of the seal member slides is formed on the outer circumference of the inner ring.

[0005] In the conductive sealed rolling bearing of Patent Document 1, in order to prevent electrolytic corrosion, the seal member is made of conductive rubber and current flows between the outer and inner rings through the seal member (i.e., the current is bypassed), preventing current from flowing through the rolling elements. Also, a conductive lubricant is used as the lubricant for lubricating the gap between the seal lip of the seal member and the seal sliding surface on the outer periphery of the inner ring. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-264401 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, even when a conductive lubricant is used as in Patent Document 1, conductivity between the seal lip of the seal member and the seal sliding surface on the outer circumference of the inner ring can be insufficient, making it difficult to ensure stable conductivity between the outer ring and inner ring via the seal member.

[0008] An object of the present invention is to provide a rolling bearing with an electrically conductive seal that can ensure stable electrical conductivity between the outer ring and the inner ring via a seal member. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a conductive sealed rolling bearing having the following configuration. [Configuration 1] The outer ring and an inner ring disposed radially inside the outer ring; a plurality of rolling elements installed in an annular bearing space formed between the outer ring and the inner ring; an annular seal member that closes one axial end opening of the bearing space, The sealing member is made of conductive rubber, In a conductive sealed rolling bearing, the seal member is fixed to one of the inner and outer raceways, and a seal sliding surface with which the seal member slides is formed on the other raceway, The conductive sealed rolling bearing is characterized in that the seal sliding surface is a surface in which the skewness Rsk and kurtosis Rku of a roughness curve in a direction perpendicular to the circumferential direction satisfy Rsk>0 and Rku<3.

[0010] When this configuration is adopted, the skewness of the roughness curve in the direction perpendicular to the circumferential direction of the seal sliding surface satisfies Rsk>0, so the seal sliding surface has surface properties closer to a smooth surface with many peaks, rather than a smooth surface with many valleys, and the peaks of these peaks and the seal member are in a state close to direct contact without the use of lubricant. This ensures stable conductivity between the outer ring and the inner ring via the seal member. In addition, the kurtosis of the roughness curve in the direction perpendicular to the circumferential direction of the seal sliding surface satisfies Rku<3, so the sharp peaks of the many peaks on the seal sliding surface are rounded. This makes it possible to suppress wear of the seal member.

[0011] [Configuration 2] 2. The rolling bearing with a conductive seal according to claim 1, wherein the seal sliding surface is a surface on which a plurality of circumferentially extending protrusions are arranged in parallel at a constant pitch of 0.2 mm or more.

[0012] By adopting this configuration, it is possible to easily form a seal sliding surface that satisfies Rsk>0 and Rku<3. That is, when a surface that is the basis of the seal sliding surface is first formed by turning, the surface becomes a surface on which a plurality of circumferentially extending protrusions (turning marks) are formed in parallel at a constant pitch, and the presence of the protrusions (turning marks) results in a surface with a skewness that satisfies Rsk>0. At this time, since the tops of the protrusions (turning marks) are still sharp, the kurtosis of the roughness curve is Rku>3. Next, the surface is polished (e.g., lapping polished) to an extent that the circumferentially extending protrusions (turning marks) are not removed, and the tops of the protrusions (turning marks) are rounded, so that the kurtosis can be made Rku<3 while maintaining the skewness Rsk>0. In this way, a seal sliding surface that satisfies Rsk>0 and Rku<3 can be easily formed by processing the surface that is the basis of the seal sliding surface by turning, and then polishing the surface to an extent that the turning marks are not removed. The seal sliding surface thus formed is a surface on which a plurality of circumferentially extending protrusions are arranged in parallel at a constant pitch of 0.2 mm or more.

[0013] In addition, the seal sliding surface of a general sealed rolling bearing is machined by turning the surface that becomes the seal sliding surface, and then the surface is ground to finish it, so there are no circumferentially extending protrusions (turning marks) and it is a completely smooth surface.As a result, the skewness of the roughness curve in the direction perpendicular to the circumferential direction is Rsk ≒ 0, and the kurtosis of the roughness curve in the direction perpendicular to the circumferential direction is Rku ≒ 3.

[0014] [Configuration 3] The outer ring and the inner ring are formed of steel, 3. The rolling bearing with an electrically conductive seal according to claim 1 or 2, wherein the sliding surface of the seal is a surface coated with an electrically conductive film having a hardness lower than that of the bearing steel.

[0015] By adopting this configuration, it becomes possible to suppress wear of the seal member particularly effectively. Effect of the Invention

[0016] In the conductive sealed rolling bearing of the present invention, the skewness of the roughness curve in a direction perpendicular to the circumferential direction of the seal sliding surface satisfies Rsk>0, so that the seal sliding surface has a surface texture similar to that of a smooth surface with many peaks, rather than a smooth surface with many valleys, and the peaks of these peaks and the seal member are in a state close to direct contact without the use of lubricant. This ensures stable conductivity between the outer ring and the inner ring via the seal member. In addition, the kurtosis of the roughness curve in a direction perpendicular to the circumferential direction of the seal sliding surface satisfies Rku<3, so that the sharp peaks of the many peaks on the seal sliding surface are rounded. This makes it possible to suppress wear of the seal member. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a conductive sealed rolling bearing according to an embodiment of the present invention. [Diagram 2] Enlarged view of the seal member and its surroundings in Figure 1 [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the vicinity of the seal sliding surface, showing an example in which the seal sliding surface in FIG. 2 is coated with a conductive film. [Figure 4] FIG. 2 is a cross-sectional view showing a modification in which the seal sliding surface of FIG. 1 is formed on the outer ring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 shows a conductively sealed rolling bearing according to an embodiment of the present invention. This conductively sealed rolling bearing comprises an outer ring 1, an inner ring 2 arranged coaxially on the radial inside of the outer ring 1, a plurality of rolling elements 4 assembled at intervals in the circumferential direction in an annular bearing space 3 formed between the outer ring 1 and the inner ring 2, an annular seal member 5 that closes one axial end opening of the bearing space 3, an annular seal member 6 that closes the other axial end opening of the bearing space 3, and a cage 7 that maintains the circumferential spacing of the plurality of rolling elements 4. A lubricant is sealed in the bearing space 3.

[0019] The inner circumference of the outer ring 1 is formed with an outer ring raceway 8 with which the rolling elements 4 roll, a pair of outer ring shoulders 9 located axially outward of the outer ring raceway surface 8, and a pair of seal fixing grooves 10 located axially outward of the outer ring shoulders 9. The pair of outer ring shoulders 9 are bank-shaped portions extending circumferentially on both sides of the outer ring raceway surface 8 in the axial direction. The seal fixing grooves 10 are grooves extending circumferentially formed adjacent to the axially outward sides of the outer ring shoulders 9. Seal members 5, 6 are fitted and fixed in the pair of seal fixing grooves 10, respectively.

[0020] The inner ring 2 has an inner ring raceway 11 with which the rolling elements 4 roll and contact, a pair of inner ring shoulders 12 located axially outward of the inner ring raceway 11, and a pair of seal sliding surfaces 13 located axially outward of the inner ring shoulders 12. The pair of inner ring shoulders 12 are bank-shaped portions extending circumferentially on both sides of the inner ring raceway 11 in the axial direction. The seal sliding surfaces 13 are inner surfaces of recesses extending circumferentially and formed adjacent to the axially outward sides of the inner ring shoulders 12. The pair of seal sliding surfaces 13 are in sliding contact with seal lips 14 formed on the inner circumferences of the seal members 5 and 6. In the drawing, the seal sliding surfaces 13 are cylindrical surfaces with a constant outer diameter along the axial direction.

[0021] The outer ring 1, the inner ring 2, and the rolling elements 4 are each formed of steel. In this example, the rolling elements 4 are balls. The rolling elements 4 are sandwiched radially between an outer ring raceway surface 8 and an inner ring raceway surface 11. The outer ring raceway surface 8 and the inner ring raceway surface 11 are the inner surfaces of grooves whose cross sections perpendicular to the circumferential direction are arc-shaped.

[0022] The seal member 5 is formed by vulcanizing and bonding conductive rubber to a core metal (not shown). The conductive rubber is a rubber composition in which a conductive filler is dispersed in a rubber material. The rubber material may be acrylic rubber, nitrile rubber, fluororubber, or the like. The conductive filler may be a carbon-based conductive filler. The seal member 6 has the same configuration as the seal member 5.

[0023] The seal sliding surface 13 is a surface on which a plurality of circumferentially extending protrusions 15 are formed in parallel at a constant pitch of 0.2 mm to 1.0 mm. The protrusions 15 have a height of 5 μm to 30 μm (preferably 20 μm or less). The seal sliding surface 13 is a surface in which the skewness of the roughness curve in a direction perpendicular to the circumferential direction satisfies Rsk>0 (preferably Rsk>0.5, more preferably Rsk>1.0) and the kurtosis of the roughness curve in a direction perpendicular to the circumferential direction satisfies Rku<3 (preferably Rku<2.8, more preferably Rku<2.6).

[0024] This seal sliding surface 13 is a surface formed as follows. That is, first, a surface that will become the original surface of the seal sliding surface 13 is formed by turning a ring-shaped material that will become the blank for the inner ring 2. The surface formed by this turning is a surface on which multiple circumferentially extending ridges 15 (turning marks) are arranged in parallel at a constant pitch (= the feed amount per turning rotation), and the presence of these ridges 15 (turning marks) results in a surface with skewness that satisfies Rsk>0. At this time, because the tops of the ridges 15 (turning marks) are still sharp, the kurtosis of the roughness curve is Rku>3.

[0025] Next, the surface is polished (for example, by barrel polishing or lapping) to the extent that the circumferentially extending protrusions 15 (turning marks) are not removed, and the peaks of the protrusions 15 (turning marks) are rounded. This makes it possible to maintain the skewness at Rsk>0 while maintaining the kurtosis at Rku<3.

[0026] In this manner, by machining the surface that is to become the seal sliding surface 13 by turning, and then polishing the surface to the extent that the turning marks are not removed, it is possible to form the seal sliding surface 13 in which the skewness of the roughness curve in the direction perpendicular to the circumferential direction satisfies Rsk>0 (preferably Rsk>0.5, and more preferably Rsk>1.0) and the kurtosis of the roughness curve in the direction perpendicular to the circumferential direction satisfies Rku<3 (preferably Rku<2.8, and more preferably Rku<2.6).

[0027] Incidentally, the seal sliding surface 13 of a typical sealed rolling bearing is formed by machining the surface that will become the seal sliding surface 13 by turning the ring-shaped material that serves as the blank for the inner ring 2, and then finishing the surface by grinding, so there are no circumferentially extending protrusions 15 (turning marks) and the surface is completely smooth.As a result, the skewness of the roughness curve in the direction perpendicular to the circumferential direction is Rsk ≒ 0, and the kurtosis of the roughness curve in the direction perpendicular to the circumferential direction is Rku ≒ 3.

[0028] The measurement of the skewness Rsk and kurtosis Rku of the roughness curve of the seal sliding surface 13 is performed in accordance with the Japanese Industrial Standard JIS B0601:2013 "Product Geometric Characteristics Specifications (GPS) - Surface Quality: Profile Curve Method - Terms, Definitions and Surface Quality Parameters" (ISO4287:1997, Amd.1:2009) and the Japanese Industrial Standard JIS B0651:2001 "Product Geometric Characteristics Specifications (GPS) - Surface Quality: Profile Curve Method - Characteristics of Stylus Type Surface Roughness Measuring Instruments" (ISO3274:1996). In addition, since the variation in the skewness Rsk and kurtosis Rku depending on the position of the seal sliding surface 13 is small, it is not necessary to measure the skewness Rsk and kurtosis Rku at multiple points on the seal sliding surface 13, but it is sufficient to measure them at one point on the seal sliding surface 13.

[0029] In this conductive sealed rolling bearing, the skewness of the roughness curve of the seal sliding surface 13 in a direction perpendicular to the circumferential direction satisfies Rsk>0 (preferably Rsk>0.5, more preferably Rsk>1.0), so that the seal sliding surface 13 has surface properties closer to a smooth surface with many peaks rather than a smooth surface with many valleys, and the peaks of these peaks and the seal member 5 are in a state close to direct contact without any lubricant between them. This makes it possible to ensure stable conductivity between the outer ring 1 and the inner ring 2 via the seal member 5, and to extend the life of the bearing. Furthermore, lubricant accumulates between adjacent protrusions 15, so that the lubricant can be used to lubricate the seal lip 14 of the seal member 5.

[0030] In addition, since the kurtosis of the roughness curve in the direction perpendicular to the circumferential direction of the seal sliding contact surface 13 satisfies Rku<3 (preferably Rku<2.8, more preferably Rku<2.6), the sharp peaks of many peaks on the surface of the seal sliding contact surface 13 are rounded off, which makes it possible to suppress wear of the seal member 5.

[0031] As shown in Fig. 3, the seal sliding surface 13 can be a surface coated with a conductive coating 16 that has a lower hardness than the steel material constituting the inner ring 2. Such conductive coating 16 can be a metal plating coating of silver, copper, gold, nickel, tin, chromium, or the like, or a conductive resin coating in which a conductive filler (carbon black, etc.) is dispersed in a resin material such as polyurethane. A chrome plating coating is preferable as it is resistant to wear and corrosion.

[0032] In the above embodiment, as shown in FIG. 2, an example has been described in which the seal lip 14 of the seal member 5 slides against a cylindrical seal sliding surface 13 having a constant outer diameter along the axial direction (radial contact seal). However, the present invention can be similarly applied to a seal member 5 in which the seal lip 14 slides against a seal sliding surface 13 perpendicular to the axial direction, or a seal member 5 in which the seal lip 14 slides against a tapered seal sliding surface 13 having an inclination angle with respect to the axial direction.

[0033] In addition, in the above embodiment, a conductively sealed rolling bearing has been described as an example in which, of both the outer ring 1 and the inner ring 2, the sealing member 5 is fixed to the outer ring 1 and the inner ring 2 is formed with a sealing sliding surface 13 with which the sealing member 5 slides. However, the present invention can be similarly applied to a conductively sealed rolling bearing in which the sealing member 5 is fixed to the inner ring 2 and the outer ring 1 is formed with a sealing sliding surface 13 with which the sealing member 5 slides, as shown in Figure 4.

[0034] In the above embodiment, a conductive sealed rolling bearing in which the seal members 5, 6 are provided on both sides of the bearing space 3 has been described as an example. However, the seal member 5 may be provided on only one side of the bearing space 3.

[0035] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0036] 1 Outer ring 2. Inner Circle 3 Bearing space 4 Rolling elements 5. Sealing material 13 Seal sliding surface 15 protrusion 16 Conductive coating

Claims

1. An outer ring (1), an inner ring (2) disposed radially inside the outer ring (1); a plurality of rolling elements (4) installed in an annular bearing space (3) formed between the outer ring (1) and the inner ring (2); and an annular seal member (5) that closes one axial end opening of the bearing space (3), The sealing member (5) is made of conductive rubber, The conductive sealed rolling bearing has the seal member (5) fixed to one of the raceways of the inner ring (2) and the outer ring (1), and the other raceway has a seal sliding surface (13) with which the seal member (5) slides, The conductive sealed rolling bearing is characterized in that the seal sliding surface (13) is a surface in which the skewness Rsk and kurtosis Rku of a roughness curve in a direction perpendicular to the circumferential direction satisfy Rsk > 0 and Rku < 3.

2. 2. The rolling bearing with a conductive seal according to claim 1, wherein the seal sliding surface (13) is a surface on which a plurality of circumferentially extending protrusions (15) are arranged in parallel at a constant pitch of 0.2 mm or more.

3. The outer ring (1) and the inner ring (2) are made of steel, 3. The rolling bearing with an electrically conductive seal according to claim 1, wherein the seal sliding surface (13) is a surface coated with an electrically conductive film (16) having a hardness lower than that of the steel material.

Images