Sliding member and rolling bearing

Abstract

This sliding member includes: a conductive sheet; and a metal ring that supports the sheet. The sheet includes: a first conductive member that is fixed in a state of being in contact with a metal first member on a first side in the radial direction of the metal ring; and a second conductive member that is slidably in contact with a metal second member on a second side in the radial direction and is connected to the first conductive member. The second conductive member has a higher conductivity than the first conductive member.

Description

Sliding member and rolling bearing

[0001] The present disclosure relates to a sliding member and a rolling bearing.

[0002] A rolling bearing with an anti-electrolytic corrosion function is disclosed in Patent Document 1. The rolling bearing described in Patent Document 1 is a bearing that supports a rotating shaft of an electric motor mounted on an electric vehicle or the like. This rolling bearing includes an outer ring, an inner ring, a plurality of balls arranged between the outer and inner rings, and an annular seal (sliding member) that closes an end opening of the bearing internal space between the outer and inner rings. The seal includes an elastic material such as conductive rubber. The inner and outer peripheral edges of this elastic material are in contact with the inner and outer rings, respectively. The contact of the elastic material with the inner and outer rings electrically connects the inner ring to the outer ring through the elastic material, thereby preventing current from flowing between the inner ring and the balls and between the outer ring and the balls, and suppressing electrolytic corrosion of the inner ring raceway, the outer ring raceway, and the balls.

[0003] JP 2015-102200 A

[0004] Because the elastic material of the seal in Patent Document 1 slides on the inner ring, its contact with the inner ring is prone to becoming unstable, which can increase electrical resistance between the inner ring and outer ring via the elastic material and make it difficult for current to flow.The present disclosure aims to improve electrical conductivity between members via a sliding member.

[0005] (1) A sliding member according to the present disclosure includes: a conductive sheet; and a metal ring supporting the sheet, wherein the sheet includes: a first conductive member fixed in contact with a first metal member on a first radial side of the metal ring; and a second conductive member slidably contacting a second metal member on a second radial side and connected to the first conductive member, wherein the second conductive member has higher conductivity than the first conductive member.

[0006] (2) The rolling bearing of the present disclosure comprises an inner ring having an inner ring raceway, an outer ring having an outer ring raceway arranged radially outward of the inner ring raceway, a plurality of rolling elements arranged to be able to roll between the inner ring raceway and the outer ring raceway, and the sliding member described in (1) arranged radially between an axial end of the inner ring and an axial end of the outer ring, wherein one of the inner ring and the outer ring is the first member, and the other of the inner ring and the outer ring is the second member.

[0007] In the sheet of the sliding member of the present disclosure, the second conductive member in slidable contact with the second member has higher conductivity than the first conductive member fixed to the first member, so that even if the contact state between the second member and the second conductive member deteriorates, an increase in electrical resistance of the conductive path between the first member and the second member via the sheet can be suppressed. Therefore, it is possible to make it easier for current to flow from one of the first member and the second member to the other via the sheet, and the conductivity between the first and second members can be improved.

[0008] FIG. 1 is a cross-sectional view showing a rolling bearing that employs a sliding member according to a first embodiment. FIG. 2 is an enlarged cross-sectional view of the sliding member. FIG. 3 is an enlarged cross-sectional view of a radially outer portion of the sliding member of FIG. 2. FIG. 4 is an enlarged cross-sectional view showing a state in which a radially inner portion of the sliding member of FIG. 2 is in contact with an inner ring. FIG. 5 is a cross-sectional view showing part of a molding die for the sliding member. FIG. 6 is a graph showing electrical resistance when an AC voltage is applied between the inner ring and the outer ring. FIG. 7 is a graph showing electrical resistance when an AC voltage is applied between the inner ring and the outer ring. FIG. 8 is a cross-sectional view showing a sealing device that employs a sliding member according to a second embodiment. FIG. 9 is an enlarged cross-sectional view showing a radially inner portion of the sliding member of FIG. 8.

[0009] <Outline of Embodiments of the Invention of the Present Disclosure> Below, outlines of embodiments of the invention of the present disclosure will be listed and described.

[0010] (1) A sliding member of the present disclosure comprises a conductive sheet and a metal ring supporting the sheet, wherein the sheet includes: a first conductive member fixed in contact with a first metal member on a first radial side of the metal ring; and a second conductive member slidably contacting a second metal member on a second radial side and connected to the first conductive member, and the second conductive member has higher conductivity than the first conductive member.

[0011] According to this configuration, the first member and the second member can be electrically connected by the sliding member sheet, allowing current to flow from one of the first member and the second member to the other through this sheet. Because the second conductive member, which slidably contacts the second member, has a higher conductivity than the first conductive member fixed to the first member, even if the contact state between the second member and the second conductive member deteriorates, an increase in electrical resistance of the conductive path between the first member and the second member through the sheet can be suppressed. Therefore, current can easily flow from one of the first member and the second member to the other through the sheet, improving the conductivity between the first and second members. Furthermore, because the first conductive member is made of a material with a lower conductivity than the second conductive member, the range of material options can be expanded in terms of processability, price, distribution volume, etc.

[0012] (2) Preferably, in the sliding member of (1), the first conductive member is made of a non-metallic material, and the second conductive member is made of a metallic material. With this configuration, the conductivity of the second conductive member can be easily made higher than the conductivity of the first conductive member.

[0013] (3) Preferably, in the sliding member of (1) or (2), the volume of the second conductive member is smaller than the volume of the first conductive member. With this configuration, the material of the second conductive member with high conductivity can be made less than the material of the first conductive member with low conductivity, thereby efficiently improving the conductivity between the first and second members.

[0014] (4) Preferably, in the sliding member of any one of (1) to (3), the second conductive member is flexible. With this configuration, even if the relative position of the second conductive member and the second member changes, the second conductive member can maintain contact with the second member by deformation of the second conductive member.

[0015] (5) Preferably, the sliding members of (1) to (4) further include rubber disposed between the metal ring and the sheet. If the metal ring and the sheet are in direct contact with each other, the sheet is likely to be damaged by the hard metal ring. However, by providing rubber between the sheet and the metal ring, the sheet can be separated from the metal ring and protected.

[0016] (6) A rolling bearing according to the present disclosure comprises: an inner ring having an inner ring raceway; an outer ring having an outer ring raceway arranged radially outward of the inner ring raceway; a plurality of rolling elements arranged to be able to roll between the inner ring raceway and the outer ring raceway; and a sliding member selected from any one of (1) to (5) arranged radially between an axial end of the inner ring and an axial end of the outer ring, wherein one of the inner ring and the outer ring is the first member, and the other of the inner ring and the outer ring is the second member.

[0017] According to this configuration, the outer ring and inner ring of the rolling bearing can be electrically connected by the sheet of the sliding member, and current can be passed from one of the outer ring and the inner ring to the other via this sheet, thereby suppressing electrolytic corrosion of the outer ring raceway, the inner ring raceway, and the balls. Furthermore, even if the contact state between the inner ring or the outer ring constituting the second member and the second conductive member deteriorates, an increase in electrical resistance between the inner ring and the outer ring via the sheet can be suppressed. Therefore, current can be easily passed from one of the inner ring and the outer ring to the other via the sheet, thereby improving conductivity between the first and second members.

[0018] <Details of the embodiments of the invention of the present disclosure> Hereinafter, embodiments of the invention of the present disclosure will be described. [First embodiment] Fig. 1 is a cross-sectional view showing a rolling bearing employing a sliding member according to a first embodiment. The rolling bearing 10 shown in Fig. 1 supports a rotating shaft S of a motor mounted on, for example, an electric vehicle or a hybrid vehicle. In Fig. 1, the rotating shaft S is indicated by a virtual line (two-dot chain line).

[0019] (Overall configuration of rolling bearing) The rolling bearing 10 comprises an outer ring 11, an inner ring 12, a plurality of rolling elements 13, a cage 14, and a sliding member 15. In this embodiment, the rolling elements 13 are balls. The rolling bearing 10 is a deep groove ball bearing. The outer ring 11 is attached to a housing H of a motor. The inner ring 12 is fitted onto and fixed to the outer peripheral surface of a rotating shaft S. In FIG. 1 , the housing H is indicated by an imaginary line (two-dot chain line). In this embodiment, the outer ring 11 is a fixed ring, and the inner ring 12 is a rotating ring. The outer ring 11 and the inner ring 12 are made of metal. The outer ring 11 and the inner ring 12 are formed from a steel material such as bearing steel. As the bearing steel, high carbon chromium bearing steel (for example, SUJ2 or SUJ3 as specified in the JIS standard) can be used. However, the outer ring 11 and the inner ring 12 may be made of other metals, for example, other steel materials such as carburized bearing steel, carbon steel, chromium steel, and stainless steel.

[0020] The outer ring 11 and the inner ring 12 are arranged concentrically. In this embodiment, the central axes of the outer ring 11 and the inner ring 12 coincide with the central axis C of the rolling bearing 10. Furthermore, in this embodiment, the direction along the central axis C and the direction parallel to the central axis C are defined as the "axial direction." Similarly, the direction perpendicular to the central axis C is defined as the "radial direction." Similarly, the direction along a circle centered on the central axis C is defined as the "circumferential direction." Furthermore, in this embodiment, the left side of FIG. 1 is defined as the axial first side, the right side of FIG. 1 is defined as the axial second side, the upper side of FIG. 1 is defined as the radial first side, and the lower side of FIG. 1 is defined as the radial second side. Furthermore, in this embodiment, the radial first side is the radial outer side, and the radial second side is the radial inner side. Therefore, in the following description, the radial first side may be referred to as the radial inner side, and the radial second side may be referred to as the radial outer side.

[0021] The outer ring 11 includes an outer ring raceway 21, two shoulders 22, and two annular grooves 23. The outer ring raceway 21 is provided on the inner peripheral surface of the outer ring 11. The balls 13 roll on this outer ring raceway 21. Two shoulders 22 are provided on both axial sides of the outer ring raceway 21. Two annular grooves 23 are provided between the shoulders 22 and the axial side surfaces of the outer ring 11, respectively. The annular grooves 23 have a circumferentially continuous annular groove shape. The sliding members 15 are attached to the annular grooves 23 located on both axial sides of the outer ring 11. However, the sliding members 15 may be attached to only the annular grooves 23 located on one of the first and second axial sides of the outer ring 11. In this case, the annular grooves 23 to which the sliding members 15 are not attached may be omitted.

[0022] The inner ring 12 has an inner ring raceway 31, two shoulders 32, and two contact surfaces 33. The inner ring raceway 31 is provided on the outer peripheral surface of the inner ring 12. The balls 13 roll on this inner ring raceway 31. Two shoulders 32 are provided on both axial sides of the inner ring raceway 31. Two contact surfaces 33 are provided between the shoulders 32 and the side surfaces of the inner ring 12. The contact surfaces 33 are provided annularly around the entire circumference of the inner ring 12. The contact surfaces 33 are groove-shaped in a cross section including the central axis C of the inner ring 12. The radially inner end of the sliding member 15 contacts the contact surfaces 33.

[0023] The balls 13 are disposed between the outer ring 11 and the inner ring 12. The balls 13 are in rolling contact with the outer ring raceway 21 and the inner ring raceway 31. The plurality of balls 13 are held at intervals in the circumferential direction by an annular cage 14.

[0024] The cage 14 has an annular body 16 and a plurality of horns (pillars) 17. The annular body 16 is provided on a second axial side of the balls 13. The plurality of horns (pillars) 17 are provided extending from the annular body 16 to a first axial side. A pocket 18 is a space between two circumferentially adjacent horns 17 on the first axial side of the annular body 16. The balls 13 are accommodated in the pocket 18. The pocket 18 is open on the first axial side.

[0025] (Configuration of Sliding Member) The sliding member 15 is formed in an annular shape. The sliding member 15 is fixed to the outer ring (first member) 11 and is in sliding contact with the inner ring (second member) 12. Specifically, the sliding member 15 is fixed to the outer ring 11 by having its radially outer end (end on the first radial side) fitted into an annular groove 23 of the outer ring 11. The radially inner end (end on the second radial side) of the sliding member 15 contacts the contact surface 33 of the inner ring 12. The sliding members 15 are provided on both axial sides of the rolling bearing 10. Therefore, the bearing internal space K1, which is an annular space between the outer ring 11 and the inner ring 12 and in which the balls 13 are present, is closed on both axial sides by the sliding members 15. The sliding members 15 separate the bearing internal space K1 in which the balls 13 are present from a bearing external space K2, which is a space on the first and second axial sides of the rolling bearing 10.

[0026] The sliding member 15 includes a conductive sheet 43. The sheet 43 is disposed between the radially outer end and the radially inner end of the sliding member 15. At the radially outer end of the sliding member 15, the sheet 43 is exposed on the surface and is in contact with the annular groove 23 of the outer ring 11. At the radially inner end of the sliding member 15, the sheet 43 is exposed on the surface and is in contact with the contact surface 33 of the inner ring 12. Therefore, the sliding member 15 forms a current path for preventing current generated by a motor or the like from flowing between the outer ring 11 and the inner ring 12 via the rolling elements 13.

[0027] An oil film made of lubricating oil or grease is formed between the balls 13 and the inner ring raceway 31, and between the balls 13 and the outer ring raceway 21. The oil film has insulating properties. The insulating properties of the oil film result in the balls 13 being insulated from the inner ring raceway 31 and from the outer ring raceway 21. When an oil film is formed between the balls 13 and the inner ring raceway 31 and a potential difference of a predetermined value or less occurs between the balls 13 and the inner ring raceway 31, no current flows between the inner ring raceway 31 and the balls 13. When an oil film is formed between the balls 13 and the outer ring raceway 21 and a potential difference of a predetermined value or less occurs between the balls 13 and the outer ring raceway 21, no current flows between the balls 13 and the outer ring raceway 21. However, when the oil film between the balls 13 and the inner ring raceway 31 is partially broken down, or when a potential difference exceeding a predetermined value occurs between the balls 13 and the inner ring raceway 31, a current flows between the balls 13 and the inner ring raceway 31, and the current may cause electrolytic corrosion in the balls 13 and / or the inner ring raceway 31. When the oil film between the balls 13 and the outer ring raceway 21 is partially broken down, or when a potential difference exceeding a predetermined value occurs between the balls 13 and the outer ring raceway 21, a current may flow between the balls 13 and the outer ring raceway 21, and the current may cause electrolytic corrosion in the balls 13 and / or the outer ring raceway 21.

[0028] The rolling bearing 10 of this embodiment is provided with a sliding member 15 that forms a current path between the outer ring 11 and the inner ring 12, so that current can be passed between the outer ring 11 and the inner ring 12 via the sliding member 15 before the potential difference between the balls 13 and the inner ring raceway 31 and the potential difference between the balls 13 and the outer ring raceway 21 become large. This makes it possible to prevent current from flowing between the outer ring 11 and the inner ring 12 via the balls 13, and to prevent electrolytic corrosion of the balls 13, the inner ring raceway 31, and the outer ring raceway 21.

[0029] FIG. 2 is an enlarged cross-sectional view of a sliding member. FIG. 3 is an enlarged cross-sectional view of a radially outer portion of the sliding member of FIG. 2. FIG. 4 is an enlarged cross-sectional view showing a state in which a radially inner portion of the sliding member of FIG. 2 is in contact with an inner ring. In the following description, a specific structure of the sliding member 15 arranged on the first axial side (left side in FIG. 1) of the rolling bearing 10 will be described. Therefore, in the description of this sliding member 15, the first axial side can be rephrased as the bearing external space K2 side, and the second axial side can be rephrased as the bearing internal space K1 side. The sliding member 15 arranged on the second axial side (right side in FIG. 1) of the rolling bearing 10 is the same part as the sliding member 15 arranged on the first side, but is arranged axially inverted.

[0030] 2 to 4, the sliding member 15 has a metal ring 41, a rubber 42, and a sheet 43. The metal ring 41, the rubber 42, and the sheet 43 are all annular. The metal ring 41 and the rubber 42, and the rubber 42 and the sheet 43 are bonded to each other, and are integrated as a whole.

[0031] The metal ring 41 supports the rubber 42 and the sheet 43. The metal ring 41 is made of metal such as galvanized steel or stainless steel. The metal ring 41 is formed by processing a plate material. The metal ring 41 includes an annular portion 41a formed in an annular ring shape and a cylindrical portion 41b formed in a cylindrical shape. The annular portion 41a is disposed perpendicular to the axial direction. The cylindrical portion 41b is disposed parallel to the axial direction. The cylindrical portion 41b is disposed at the radial outer end of the annular portion 41a. The cylindrical portion 41b extends from the radial outer end of the annular portion 41a to the second axial side (the side of the bearing internal space K1). The annular portion 41a and the cylindrical portion 41b of the metal ring 41 are formed by plastic processing a plate material into a substantially L-shaped cross section.

[0032] The rubber 42 is electrically conductive. Specifically, the rubber 42 is manufactured by blending, for example, synthetic rubber with an electrically conductive material. The electrically conductive material is carbon black, metal powder, or the like. The specific structure of the rubber 42 will be described later together with the structure of the sheet 43.

[0033] The sheet 43 is made of a nonwoven fabric or a woven fabric made of conductive fibers. The sheet 43 is flexible. In this embodiment, the sheet 43 further contains a synthetic resin as a binder. The binder is fixed to the surface of a portion of the conductive fibers contained in the sheet 43. The sheet 43 in this embodiment is a nonwoven fabric or a woven fabric made of conductive fibers with the binder fixed thereto.

[0034] The seat 43 integrally includes an intermediate portion 44, a fixed portion 45, and a sliding portion 46. The fixed portion 45 is a portion located radially outward (on a first radial side) from the metal ring 41. The sliding portion 46 is a portion located radially inward (on a second radial side) from the metal ring 41. The intermediate portion 44 is a portion located radially between the fixed portion 45 and the sliding portion 46.

[0035] The intermediate portion 44 of the seat 43 has a first portion 44a, a second portion 44b, and a third portion 44c. The first portion 44a extends in the radial direction. As shown in Figures 3 and 4, the first portion 44a is disposed on the second axial side (the bearing internal space K1 side) of the annular portion 41a of the metal ring 41 at a distance t1.

[0036] The second portion 44b is bent from the radially outer end of the first portion 44a toward the second axial side and extends axially. The second portion 44b is formed in a cylindrical shape. As shown in FIG. 3, the second portion 44b is disposed radially inside the cylindrical portion 41b of the metal ring 41 at a distance t2.

[0037] The third portion 44c is bent radially outward from the end of the second portion 44b on the second axial side and extends radially. As shown in Fig. 3, the third portion 44c is disposed on the second axial side of the cylindrical portion 41b of the metal ring 41 at a distance t3. Therefore, the intermediate portion 44 of the sheet 43 and the metal ring 41 are disposed at distances t1, t2, and t3 across the entire radial direction.

[0038] The fixing portion 45 of the seat 43 is formed continuously with the third portion 44c of the intermediate portion 44. As shown in FIG. 3 , the fixing portion 45 has a fourth portion 45a and a fifth portion 45b. The fourth portion 45a extends radially continuously from the radially outer end of the third portion 44c of the intermediate portion 44. The fifth portion 45b extends from the radially outer end of the fourth portion 45a while slanting toward the first axial side and radially outward. The tip of the fifth portion 45b constitutes the radially outer end of the seat 43. The tip of the fifth portion 45b is in direct contact with the annular groove 23 of the outer ring 11. In this embodiment, the fourth portion 45a of the fixing portion 45 is also in direct contact with the annular groove 23. A portion of the third portion 44c of the intermediate portion 44 is also in direct contact with the annular groove 23.

[0039] As shown in FIGS. 2 and 4 , the sliding portion 46 of the seat 43 is formed continuously with the first portion 44a, which is the intermediate portion 44. In this embodiment, the portion of the seat 43 that is positioned radially inward from the radially inner end of the metal ring 41 serves as the sliding portion 46. The sliding portion 46 extends linearly radially inward from the first portion 44a of the intermediate portion 44. Therefore, the first portion 44a of the intermediate portion 44 and the sliding portion 46 as a whole form an annular shape perpendicular to the axial direction. The radially inner end portion 46a of the sliding portion 46 directly contacts the contact surface 33 of the inner ring 12. The radially inner end portion 46a of the sliding portion 46 is bent toward the first axial side by contacting the contact surface 33.

[0040] 2, the rubber 42 is bonded to the sheet 43 and the metal ring 41. The rubber 42 is provided over the entire first axial side (the bearing external space K2 side) of the sheet 43. The rubber 42 has a first portion 42c, a second portion 42a, a third portion 42b, and a fourth portion 42d.

[0041] The second portions 42a of the rubber 42 are portions that are located in the spaces t1, t2, and t3 that are formed between the metal ring 41 and the sheet 43. The second portions 42a of the rubber 42 maintain the spaces t1, t2, and t3 between the metal ring 41 and the sheet 43 so that the metal ring 41 and the sheet 43 are not directly bonded to each other. Therefore, the second portions 42a suppress damage to the sheet 43 that would otherwise occur if the sheet 43 were to come into direct contact with the metal ring 41.

[0042] The third portion 42b of the rubber 42 is formed continuously radially outward from the second portion 42a. The third portion 42b is disposed in an area surrounded by the fixed portion 45 of the seat 43 and the cylindrical portion 41b of the metal ring 41. The third portion 42b of the rubber 42 elastically supports the fifth portion 45b of the seat 43 from the radially inner side. The cylindrical portion 41b of the metal ring 41 supports the third portion 42b of the rubber 42 from the radially inner side. Therefore, the fixed portion (radially outer end portion) 45 of the seat 43 is pressed against the annular groove 23 of the outer ring 11 by the elasticity of the third portion 42b of the rubber 42 supported by the cylindrical portion 41b of the metal ring 41, and is in reliable contact with the annular groove 23.

[0043] As shown in FIG. 4 , the first portion 42c of the rubber 42 extends radially inward from the radially inner end of the second portion 42a of the rubber 42. The first portion 42c extends radially inward with a substantially constant thickness along the side surface of the sliding portion 46 of the seat 43 on the first axial side, and the radially inner end is tapered. The first portion 42c is formed in an annular shape perpendicular to the axial direction. When the radially inner end 46a of the sliding portion 46 of the seat 43 contacts the contact surface 33 and bends, the first portion 42c of the rubber 42 elastically deforms and bends toward the first axial side together with the sliding portion 46. In FIG. 4 , the sliding portion 46 and the first portion 42c in an unloaded state before elastic deformation are indicated by two-dot chain lines, and the sliding portion 46 and the first portion 42c after elastic deformation are indicated by solid lines. In this embodiment, the portion including the sliding portion 46 of the sheet 43 and the first portion 42 c of the rubber 42 adhered to this sliding portion 46 is also referred to as the “lip portion 48 ” of the sliding member 15 .

[0044] The fourth portion 42d of the rubber 42 extends from the radially outer end of the first portion 42c past the radially inner end of the metal ring 41 and is disposed on the side surface of the metal ring 41 on the first axial side. Therefore, the fourth portion 42d has a generally L-shaped cross section, covers the radially inner end surface of the annular portion 41a and the side surface on the second axial side, and is bonded to these surfaces. The fourth portion 42d of the rubber 42 serves to firmly bond the rubber 42 and the metal ring 41 and prevents the rubber 42 from peeling off from the metal ring 41.

[0045] Since the rubber 42 has higher rigidity than the sheet 43, the shape of the sheet 43 is maintained by the rubber 42. The shape of the middle portion 44 of the sheet 43 is also maintained by the metal ring 41.

[0046] The sheet 43 is formed of a nonwoven or woven fabric made of conductive fibers. The sheet 43 contains voids inside in its material state before the sliding member 15 is manufactured. After the sliding member 15 is manufactured, the rubber 42 also exists in the voids of the sheet 43. As will be described later, the sliding member 15 is manufactured by inserting the metal ring 41 and the sheet 43 into a mold, vulcanizing the rubber material constituting the rubber 42 to form a predetermined shape, and bonding the rubber material to the metal ring 41 and the sheet 43. Hereinafter, this manufacturing process will also be referred to as "vulcanization bonding." During this vulcanization bonding, the rubber 42 enters the voids in the sheet 43. During vulcanization bonding, the rubber 42 is easily bonded to the binder.

[0047] The fixed portion 45 of the sheet 43 is exposed on the surface of the sliding member 15 and contacts the annular groove 23 of the outer ring 11. The sliding portion 46 of the sheet 43 is exposed on the surface of the sliding member 15 and contacts the contact surface 33 of the inner ring 12. The multiple conductive fibers comprising the sheet 43 are in contact with one another, and the sheet 43 is conductive due to contact between the conductive fibers from the fixed portion 45 to the sliding portion 46. Because the sheet 43 is in contact with the outer ring 11 and the inner ring 12, the outer ring 11 and the inner ring 12 are electrically connected via the sheet 43. The conductive metal ring 41 and rubber 42 are in contact with the sheet 43. The outer ring 11 and the inner ring 12 are electrically connected not only via the sheet 43 but also via the conductive metal ring 41 and rubber 42. However, the electrical resistance of the sheet 43 is lower than the electrical resistance of the rubber 42.

[0048] Therefore, the sliding member 15 of this embodiment can allow electric charge to escape from one of the fixed portion 45 and the sliding portion 46 to the other. Furthermore, the sliding member 15 of this embodiment can allow electric charge to escape from one of the member (first member) that fixes the fixed portion 45 and the member (second member) on which the sliding portion 46 slides to the other. The rolling bearing 10 of this embodiment can allow electric charge to escape from one of the outer ring 11 and the inner ring 12 to the other via the sliding member 15, making it possible to suppress electrolytic corrosion of the balls 13 and the outer ring raceway 21 and inner ring raceway 31 on which the balls 13 roll.

[0049] As shown in Fig. 2, the seat 43 is disposed closest to the second axial side (the bearing internal space K1 side) of the sliding member 15. Meanwhile, the contact surface 33 formed on the inner ring 12 faces the first axial side (the bearing external space K2 side). This makes it easier for the sliding portion 46 of the seat 43 to come into contact with the contact surface 33. When the contact surface 33 faces the second axial side, the sliding member 15 may be formed so that the seat 43 is located closest to the first axial side of the sliding member 15.

[0050] 2 and 4, the sheet 43 has a first conductive member 43A and a second conductive member 43B. The first conductive member 43A is formed in an annular shape. The first conductive member 43A constitutes the entire intermediate portion 44, fixed portion 45, and sliding portion 46 of the sheet 43. The first conductive member 43A contacts the annular groove 23 of the outer ring 11 at the fixed portion 45. The first conductive member 43A does not contact the contact surface 33 of the inner ring 12 at the sliding portion 46.

[0051] The first conductive member 43A is flexible. In this embodiment, the first conductive member 43A is made of a nonwoven fabric or a woven fabric made of conductive fibers. The first conductive member 43A uses non-metallic fibers, such as carbon fibers, as the conductive fibers. However, the conductive fibers may be made of other materials, such as conductive metal fibers of copper, silver, gold, nickel, aluminum, stainless steel, etc.

[0052] The second conductive member 43B is formed in an annular shape. The second conductive member 43B constitutes a part of the sliding portion 46 of the sheet 43. Specifically, the second conductive member 43B constitutes the radially inner end portion 46a of the sliding portion 46. The second conductive member 43B is superimposed on the first conductive member 43A and adhered to the first conductive member 43A.

[0053] The second conductive member 43B has an inner diameter approximately equal to the inner diameter of the first conductive member 43A and an outer diameter smaller than the outer diameter of the first conductive member 43A. Therefore, the volume of the second conductive member 43B is smaller than the volume of the first conductive member 43A. The second conductive member 43B is disposed on the second axial side of the first conductive member 43A. In other words, the second conductive member 43B is disposed closer to the bearing internal space K1 or closer to the contact surface 33 of the inner ring 12 than the first conductive member 43A. The second conductive member 43B is in contact with the contact surface 33. The surface of the second axial side of the second conductive member 43B is flush with the surface of the second axial side of the first conductive member 43A, which is located radially outward of the second conductive member 43B.

[0054] The second conductive member 43B is flexible. In this embodiment, the second conductive member 43B is made of a nonwoven or woven fabric made of conductive fibers. In this embodiment, the second conductive member 43B uses metal fibers as the conductive fibers. For example, the second conductive member 43B uses stainless steel fibers as the conductive fibers. The electrical resistivity of the second conductive member 43B is lower than that of the first conductive member 43A. Therefore, the second conductive member 43B has higher conductivity (electrical conductivity) than the first conductive member 43A. The second conductive member 43B has more free electrons than the first conductive member 43A, and the movement of these free electrons can transport electric charge between the second conductive member 43B and the inner ring 12.

[0055] The second conductive member 43B may be made of conductive fibers made of a material other than stainless steel, provided that the second conductive member 43B has higher conductivity than the first conductive member 43A. The second conductive member 43B may be made of fibers made of other conductive metals such as copper, silver, gold, nickel, and aluminum. The second conductive member 43B may also be in a form other than fiber.

[0056] The seat 43 directly contacts the contact surface 33 of the inner ring 12 at the sliding portion 46. When the inner ring 12 is rotating, the state of contact between the sliding portion 46 and the contact surface 33 is constantly changing. For example, if the outer ring 11 and the inner ring 12 move relatively in the axial or radial direction, the inner ring 12 and the sliding member 15 move relatively apart, which may weaken the contact between the sliding portion 46 and the contact surface 33, or otherwise deteriorate the state of contact. Furthermore, if an insulating material such as lubricating oil or grease seeps between the sliding portion 46 and the contact surface 33, the state of contact between the sliding portion 46 and the contact surface 33 may also deteriorate.

[0057] If the sliding portion 46 of the sheet 43 were composed only of the first conductive member 43A, which has low conductivity, and the first conductive member 43A were in contact with the contact surface 33, the contact condition between the sliding portion 46 and the contact surface 33 would deteriorate, making the conductive path more likely to be interrupted and potentially making it difficult for current to flow between the inner ring 12 and the outer ring 11 via the sheet 43. In this regard, in the present embodiment, the sheet 43 is provided with a second conductive member 43B, which has higher conductivity than the first conductive member 43A, and this second conductive member 43B is in contact with the contact surface 33 of the inner ring 12. Therefore, even if the contact condition between the sliding portion 46 and the inner ring 12 deteriorates, current can easily flow between the inner ring 12 and the outer ring 11 via the sheet 43.

[0058] The above-described effects can also be achieved by constructing the sheet 43 using only the highly conductive second conductive member 43B. However, some highly conductive materials have poor processability, are expensive, or are in limited supply on the market, which may limit the range of material choices. In this embodiment, the first conductive member 43A, which accounts for the majority of the sheet 43, is made of a low-conductivity material (e.g., carbon fiber), and the portion 46a of the sheet 43 that contacts the inner ring 12 is made of a highly conductive material (e.g., metal fiber), thereby eliminating or reducing the above-described disadvantages.

[0059] The inventors of the present application conducted a test to measure the electrical resistance (impedance) of the conductive path generated when an AC voltage was applied between the inner ring and outer ring of the rolling bearing described in the above embodiment. The results are shown in Figures 6 and 7. Figure 6 shows the case where the inner ring was stopped from rotating, and Figure 7 shows the case where the inner ring 12 was rotating. In both cases, the test was conducted at room temperature in a dry state without oil. In addition, in Figures 6 and 7, the working example is an example in which the sliding member sheet is composed of first and second conductive members, and the second conductive member is in contact with the inner ring, as shown in the above embodiment. The comparative example is an example in which the sliding member sheet is composed of only the first conductive member, and the first conductive member is in contact with the inner ring.

[0060] As shown in Figure 6, when the rotation of the inner ring is stopped, the impedance is lower in the Example than in the Comparative Example. Also, as shown in Figure 7, when the inner ring is rotated, the impedance is lower in the Example than in the Comparative Example.

[0061] In both the example and the comparative example, the impedance is greater when the inner ring is rotated ( FIG. 7 ) than when the rotation of the inner ring is stopped ( FIG. 6 ). This means that rotating the inner ring worsens the contact state between the seat and the inner ring. Furthermore, the difference in impedance between the example and the comparative example is greater when the inner ring is rotated ( FIG. 7 ) than when the rotation of the inner ring is stopped ( FIG. 6 ). This shows that adopting the example is more effective when rotating the inner ring worsens the contact state between the seat and the inner ring.

[0062] [Method of manufacturing slide member] Fig. 5 is a cross-sectional view showing a part of a mold for molding a slide member. The slide member 15 is manufactured by compression molding (pressure molding) using a mold. The mold 50 for molding the slide member 15 has an upper mold 51 and a lower mold 52. The upper mold 51 has a cavity 51a. The lower mold 52 has cavities 52a and 52b. The cavity 52b is formed by further digging down from the bottom surface of the cavity 52a.

[0063] An adhesive is applied to the surface of the metal ring 41. For example, the metal ring 41 is immersed in the adhesive to apply the adhesive to the surface. The metal ring 41, the first conductive member 43A and the second conductive member 43B constituting the sheet 43, and the unvulcanized rubber material G are arranged between the upper mold 51 and the lower mold 52 when the mold 50 is opened after the upper mold 51 and the lower mold 52 are separated. The second conductive member 43B is arranged above the first conductive member 43A.

[0064] 2, the third portion 42b and a part of the second portion 42a (around the cylindrical portion 41b of the metal ring 41) of the rubber 42. The first conductive member 43A, which constitutes the second portion 44b and the fixed portion 45 in the intermediate portion 44 of the sheet 43, fits into this cavity 51a, and is molded into a shape that fits the inner surface of the cavity 51a.

[0065] The cavity 52a of the lower mold 52 molds a part of the second portion 42a (excluding the area around the cylindrical portion 41b of the metal ring 41) and the first portion 42c of the rubber 42 shown in Fig. 2. The first conductive member 43A constituting the sliding portion 46 and a part of the first portion 44a in the intermediate portion 44 of the sheet 43, and the second conductive member 43B constituting the sliding portion 46 enter the cavity 52a and are molded into a flat shape (see Fig. 5) that fits along the lower surface 51b of the upper mold 51. The cavity 52b of the lower mold 52 molds the fourth portion 42d of the rubber 42 shown in Fig. 2.

[0066] The sliding member 15 is manufactured by placing the metal ring 41, the sheet 43, and the unvulcanized rubber material G between the upper mold 51 and the lower mold 52, closing the upper mold 51 and the lower mold 52, and applying pressure and heat. The pressurized unvulcanized rubber material G flows within the mold. The unvulcanized rubber material G fills the cavities 51a, 52a, and 52b of the upper mold 51 and the lower mold 52. The unvulcanized rubber material G also fills the gaps between the first conductive member 43A and the second conductive member 43B of the sheet 43. When heated in this state, the adhesive hardens, and the unvulcanized rubber material G becomes rubber 42. As the adhesive hardens and the unvulcanized rubber material G becomes vulcanized rubber 42, the metal ring 41, the sheet 43, and the rubber 42 become integrated. Unnecessary portions of the integrated part are removed to form the sliding member 15.

[0067] By impregnating the sheet 43 with unvulcanized rubber material G and vulcanizing it in this manner, the rigidity of the sheet 43 is increased, and the sheet 43 and the rubber 42 become one body. The first conductive member 43A and the second conductive member 43B that constitute the sheet 43 also become one body.

[0068] [Second embodiment] Fig. 8 is a cross-sectional view showing a sealing device employing a sliding member according to a second embodiment. Fig. 9 is an enlarged cross-sectional view showing a radially inner portion of the sliding member of Fig. 8. The sliding member 15 of this embodiment is incorporated into a sealing device 63 provided between a metallic rotating shaft S and a metallic housing H surrounding the rotating shaft S. The sealing device 63 prevents leakage of lubricating oil inside the equipment between the rotating shaft S and the housing H.

[0069] The sealing device 63 has a seal portion 64, a second metal ring 65 made of metal, and a sliding member 15. The seal portion 64 is made of rubber and has elasticity. The seal portion 64 is vulcanization bonded to the second metal ring 65 and becomes one with the second metal ring 65. The seal portion 64 has a first lip 69 that contacts the outer circumferential surface Sa of the rotating shaft S. The seal portion 64 further has a second lip 70 and a third lip 71. The seal portion 64 may be made of conductive rubber that is electrically conductive.

[0070] The first lip 69 is pressed against the rotating shaft S by a garter spring 72. The second lip 70 is located on the second axial side of the first lip 69 and contacts the outer peripheral surface Sa of the rotating shaft S. The third lip 71 is located on the second axial side of the second lip 70 and has a shape that extends toward the second axial side. The third lip 71 contacts a member (not shown) located on the second axial side. These lips 69, 70, and 71 elastically deform when they come into contact with a mating member such as the rotating shaft S, but for purposes of explanation, the drawings show them in an undeformed state.

[0071] The second metal ring 65 is made of stainless steel or carbon steel (cold-rolled steel). The second metal ring 65 supports the seal portion 64. The second metal ring 65 has a second cylindrical portion 65a as a cylindrical portion and a second annular portion 65b as an annular portion. The second cylindrical portion 65a is attached to the inner periphery of the housing H in metallic contact with the housing H. The second annular portion 65b extends from a part of the second cylindrical portion 65a in a direction toward the rotation axis S.

[0072] The second cylindrical portion 65a is fitted with an interference fit to the inner circumferential surface of the housing H. As a result, the second metal ring 65 is attached in a state of metallic contact with the housing H. The first lip 69 is provided to extend from a part of the radially inner side of the second annular portion 65b toward the rotation axis S.

[0073] Similar to the first embodiment, the sliding member 15 includes a metal ring 41, a rubber 42, and a sheet 43. The metal ring 41, the rubber 42, and the sheet 43 are all annular. The metal ring 41 and the rubber 42, and the rubber 42 and the sheet 43 are bonded to each other and are integrated as a whole. The sheet 43 includes a first conductive member 43A and a second conductive member 43B. The materials of the metal ring 41, the rubber 42, and the sheet 43 (the first conductive member 43A and the second conductive member 43B) are similar to those of the first embodiment.

[0074] The radially outer end (fixed portion) of the first conductive member 43A constituting the seat 43 contacts the inner circumferential surface of the second cylindrical portion 65a of the second metal ring 65 fixed to the housing H. Therefore, in this embodiment, the second metal ring 65 and the housing H constitute the "second member." The second conductive member 43B constituting the radially inner end of the seat 43 slidably contacts the outer circumferential surface Sa of the rotating shaft S. Therefore, in this embodiment, the rotating shaft S constitutes the "first member." The seat 43 of the sliding member 15 can pass current between the first member 65, H and the second member S.

[0075] [Other Embodiments] In the first and second embodiments, the second conductive member 43B of the sheet 43 in the sliding member 15 is formed from conductive fibers, but this is not limiting. For example, the second conductive member 43B may be formed from a thin, stretched metal foil. Furthermore, although the second conductive member 43B is joined to the first conductive member 43A by vulcanization adhesion with the rubber 42, it may also be joined to the first conductive member 43A by mechanical means such as an adhesive or a fastener.

[0076] In the sliding member 15 of the first and second embodiments, the second conductive member 43B of the sheet 43 is formed in an annular shape and is continuous in the circumferential direction, but may be formed intermittently in the circumferential direction. In other words, the sheet 43 may include a plurality of second conductive members 43B spaced apart in the circumferential direction.

[0077] In the sliding member 15 of the first and second embodiments, the sliding portion 46 of the sheet 43 is arranged on the second axial side of the lip portion 48, and the first portion 42c of the rubber 42 is arranged on the first axial side of the sliding portion 46, but the sliding portion 46 of the sheet 43 may be arranged on the first axial side of the lip portion 48, and the first portion 42c of the rubber 42 may be arranged on the second axial side of the sliding portion 46.

[0078] In the sliding member 15 of the first and second embodiments, the metal ring 41 is disposed on the first axial side of the rubber 42, but it may be disposed on the second axial side of the sheet 43.

[0079] In the rolling bearing 10 of the first embodiment, the outer ring 11 is a fixed ring and the inner ring 12 is a rotating ring, but the outer ring 11 may be a rotating ring and the inner ring 12 a fixed ring. In this case, the sliding member 15 is fixed to the inner ring 12, which is a first member, and is in slidable contact with the outer ring 11, which is a second member.

[0080] In the sliding member 15 of the first and second embodiments, a synthetic resin is fixed as a binder to the conductive fibers that make up the sheet 43. On the other hand, in the sheet of the present invention, the conductive fibers that make up the sheet do not need to have a synthetic resin as a binder. The sliding member 15 of the first embodiment is used in the rolling bearing 10. However, the sliding member 15 of the present invention may be used in a device that is fixed to one of two members that move relatively and is in slidable contact with the other member.

[0081] In the first embodiment, the rolling bearing 10 is a deep groove ball bearing. However, in the present invention, the rolling bearing 10 may be an angular contact ball bearing, a roller bearing in which the rolling elements are rollers, or the like.

[0082] The above-described embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0083] 10: Rolling bearing 11: Outer ring (first member) 12: Inner ring (second member) 13: Rolling element 15: Sliding member 21: Outer ring raceway 31: Inner ring raceway 41: Metal ring 42: Rubber 43: Sheet 43A: First conductive member 43B: Second conductive member 65: Second metal ring (first member) H: Housing (first member) S: Rotating shaft (second member)

Claims

1. A sliding member comprising: a conductive sheet; and a metal ring supporting the sheet, wherein the sheet includes: a first conductive member fixed in contact with a first metallic member on a first radial side of the metal ring; and a second conductive member slidably contacting a second metallic member on a second radial side and connected to the first conductive member, wherein the second conductive member has a higher conductivity than the first conductive member.

2. The sliding member according to claim 1, wherein said first conductive member is made of a non-metallic material and said second conductive member is made of a metal material.

3. The sliding member according to claim 1 or 2, wherein the volume of the second conductive member is smaller than the volume of the first conductive member.

4. The sliding member according to claim 1 or 2, wherein the second conductive member is flexible.

5. The sliding member according to claim 1 or 2, further comprising a rubber disposed between the metal ring and the sheet.

6. A rolling bearing comprising: an inner ring having an inner ring raceway; an outer ring having an outer ring raceway arranged radially outward of the inner ring raceway; a plurality of rolling elements arranged to be able to roll between the inner ring raceway and the outer ring raceway; and a sliding member according to claim 1 or 2 arranged radially between an axial end of the inner ring and an axial end of the outer ring, wherein one of the inner ring and the outer ring is the first member, and the other of the inner ring and the outer ring is the second member.

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