Sliding member and rolling bearing

Abstract

Provided is a sliding member including: a sheet that is a nonwoven fabric or a woven fabric formed from conductive fibers; a metal ring; and a rubber. The sheet integrally has: a fixed part that is fixed in a state of being in contact with a first member made of a steel material on a first side in the radial direction of the metal ring; a sliding part that slidably contacts a second member made of a steel material on a second side in the radial direction; and an intermediate part that is positioned between the fixed part and the sliding part. The rubber has a first portion that is adhered to the sliding part. The ratio of the thickness of the sliding part in the axial direction to the thickness in the axial direction of the sliding member including the sliding part and the first portion is 25-35%.

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] The elastic material of the seal (sliding member) in Patent Document 1 has a certain degree of conductivity due to the incorporation of carbon fiber into the rubber. However, in order to further suppress electrolytic corrosion of the raceway, it is desired to further increase the conductivity of the seal. Therefore, an object of the present disclosure is to increase the conductivity of the sliding member.

[0005] (1) A sliding member of the present disclosure comprises a sheet which is a nonwoven or woven fabric formed of conductive fibers, a metal ring, and rubber, wherein the sheet integrally comprises: a fixed portion which is fixed in contact with a first member made of steel on a first radial side of the metal ring; a sliding portion which is slidably in contact with a second member made of steel on a second radial side; and an intermediate portion which is located between the fixed portion and the sliding portion; the rubber has a first portion bonded to the sliding portion; and a ratio of the axial thickness of the sliding portion to the axial thickness of the sliding member including the sliding portion and the first portion is 25% or more and 35% or less.

[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) above 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] The sliding member of the present disclosure includes a sheet that is a nonwoven or woven fabric formed from conductive fibers, and this sheet can have lower electrical resistance and higher conductivity than an elastic material made of rubber with carbon fibers kneaded into it. Therefore, the sliding member electrically connects a first member and a second member via the sheet, and current can flow from one of the first member and the second member to the other via the sheet. Furthermore, by setting the ratio of the thickness of the sliding portion to the thickness of the sliding member including the sliding portion of the sheet and the first portion of the rubber to be 25% or more and 35% or less, the sliding portion can improve its ability to follow the second member, thereby enabling further improvement in conductivity.

[0008] Fig. 1 is a cross-sectional view showing an example of a rolling bearing according to the present disclosure. 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. Fig. 5 is a cross-sectional view showing a part of a molding die for the sliding member. Fig. 6 is an enlarged cross-sectional view showing a state in which the radially inner portion of the sliding member of Fig. 2 is in an unloaded state. Fig. 7 is a graph showing the relationship between the ratio of the sheet thickness to the lip thickness and the loss sine (tan δ).

[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 includes a sheet that is a nonwoven or woven fabric formed of conductive fibers, a metal ring, and rubber, wherein the sheet integrally includes: a fixed portion that is fixed in contact with a first member made of steel on a first radial side of the metal ring; a sliding portion that is slidably in contact with a second member made of steel on a second radial side; and an intermediate portion located between the fixed portion and the sliding portion, wherein the rubber has a first portion bonded to the sliding portion, and a ratio of the axial thickness of the sliding portion to the axial thickness of the sliding member including the sliding portion and the first portion is 25% or more and 35% or less.

[0011] According to this configuration, the sliding member includes a sheet that is a nonwoven or woven fabric formed from conductive fibers, and the sheet has lower electrical resistance and higher conductivity than an elastic material made of rubber with carbon fibers kneaded into it. Therefore, the sliding member electrically connects the first member and the second member through the sheet, and current can flow from one of the first member and the second member to the other via the sheet. Furthermore, by setting the ratio of the thickness of the sliding portion to the thickness of the sliding member including the sliding portion of the sheet and the first portion of the rubber to be 25% or more and 35% or less, the sliding portion can improve its ability to follow the second member, thereby enabling further improvement in conductivity.

[0012] (2) Preferably, in the sliding member of (1) above, the metal ring is disposed on a first axial side of the sheet at a distance, and the rubber has a second portion disposed on the first radial side of the first portion at the distance.

[0013] (3) Preferably, the sliding member of (2) above further comprises a third portion of the rubber arranged on the first radial side of the second portion, and the first portion, the second portion, and the third portion are adhered to the entire first axial side of the sheet.

[0014] With this configuration, the shape of the entire sheet can be maintained by the rubber.

[0015] (4) Preferably, the sliding member of (2) or (3) above has a fourth portion in which the rubber extends beyond the end of the metal ring on the second radial side and is positioned on the first axial side of the metal ring.

[0016] This configuration strengthens the bond between the rubber and the metal ring. In addition, since the fourth portion is located on the opposite side of the seat in the axial direction, the fourth portion will not damage the seat.

[0017] (5) 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 according to any one of (1) to (4) above 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.

[0018] With this configuration, the outer ring and inner ring of the rolling bearing can be electrically connected by a sheet of sliding material, and electric current can be passed from one of the outer ring and inner ring to the other via this sheet, thereby suppressing electrolytic corrosion of the outer ring raceway, inner ring raceway, and balls.

[0019] (6) Preferably, in the rolling bearing of (5) above, the sheet of the sliding member is disposed closer to the rolling element than the metal ring and the rubber in the axial direction.

[0020] Such a configuration makes it easier for the sliding portion of the sliding member to come into contact with the inner ring or the outer ring.

[0021] <Details of the embodiment of the invention of the present disclosure> An embodiment of the invention of the present disclosure will be described below. Fig. 1 is a cross-sectional view showing an example of a rolling bearing of the present disclosure. 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).

[0022] The rolling bearing 10 includes 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 a virtual 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 formed of a steel material such as bearing steel. High-carbon chromium bearing steel (e.g., SUJ2 or SUJ3 as specified in the JIS standard) can be used as the bearing steel. However, the outer ring 11 and the inner ring 12 may also be formed of other steel materials such as carburized bearing steel, carbon steel, chromium steel, or stainless steel.

[0023] 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.

[0024] 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.

[0025] The inner ring 12 has an inner ring raceway 31, two shoulders 32, and two sliding member 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 sliding member contact surfaces 33 are provided between the shoulders 32 and the side surfaces of the inner ring 12. The sliding member contact surface 33 is provided annularly around the entire circumference of the inner ring 12. The sliding member contact surface 33 is 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 sliding member contact surface 33.

[0026] 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.

[0027] 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.

[0028] 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 a sliding member 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 partition 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.

[0029] The sliding member 15 includes a conductive sheet 43 disposed between a radially outer end and a radially inner end. The sheet 43 is exposed on the surface of the sliding member 15 at the radially outer end and is in contact with the annular groove 23 of the outer ring 11. The sheet 43 is exposed on the surface of the sliding member 15 at the radially inner end and is in contact with the sliding member 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.

[0030] 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.

[0031] The rolling bearing 10 of this embodiment is provided with a sliding member 15 that forms a current path, so that before the potential difference between the balls 13 and the inner ring raceway 31 or the potential difference between the balls 13 and the outer ring raceway 21 increases, the potential difference between the outer ring 11 and the inner ring 12 is reduced by passing a current between the outer ring 11 and the inner ring 12 via the sliding member 15. By reducing the potential difference between the outer ring 11 and the inner ring 12, the occurrence of electrolytic corrosion in the balls 13, the inner ring raceway 31, and the outer ring raceway 21 is suppressed.

[0032] [Specific Structure of Slide Member 15] Figure 2 is an enlarged cross-sectional view of the slide member. Figure 3 is an enlarged cross-sectional view of the radially outer portion of the slide member of Figure 2. Figure 4 is an enlarged cross-sectional view showing a state in which the radially inner portion of the slide member of Figure 2 is in contact with the inner ring. In the following explanation, a specific structure of the slide member 15 arranged on the first axial side (left side in Figure 1) of the rolling bearing 10 will be described. Therefore, in the explanation of this slide 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 slide member 15 arranged on the second axial side (right side in Figure 1) of the rolling bearing 10 is the same part as the slide member 15 arranged on the first side, but is arranged axially inverted.

[0033] 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.

[0034] The metal ring 41 is formed from a metal such as a galvanized steel plate 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 shape and a cylindrical portion 41b formed in a cylindrical shape. The annular portion 41a is arranged perpendicular to the axial direction. The cylindrical portion 41b is arranged parallel to the axial direction. The cylindrical portion 41b is arranged 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 the plate material into a substantially L-shaped cross section.

[0035] 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.

[0036] The sheet 43 is made of a nonwoven fabric or a woven fabric made of conductive fibers. In this embodiment, the sheet 43 uses carbon fibers as the conductive fibers. However, the conductive fibers may be fibers made of other materials, such as conductive metals such as copper and nickel. The electrical resistance of the sheet 43 is lower than the electrical resistance of the rubber 42. Therefore, the sheet 43 has higher electrical conductivity than the rubber 42.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The second portion 44b is bent from the radially outer end of the first portion 44a toward the second axial side and extends axially. Therefore, 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 with a distance t2 therebetween.

[0041] 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.

[0042] 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.

[0043] 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 a ring shape perpendicular to the axial direction. The radially inner end 46a of the sliding portion 46 directly contacts the sliding member contact surface 33 of the inner ring 12. The radially inner end 46a of the sliding portion 46 is bent toward the first axial side by contacting the sliding member contact surface 33.

[0044] 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.

[0045] The second portions 42a of the rubber 42 are portions that are disposed 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.

[0046] 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 (radial outer end) 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, ensuring reliable contact with the annular groove 23.

[0047] 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 sliding member 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 .

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 sliding member 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 also contact the sheet 43. The outer ring 11 and the inner ring 12 are electrically connected via the conductive metal ring 41 and rubber 42 in addition to the sheet 43.

[0052] 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 that fixes the fixed portion 45 and the 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.

[0053] 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 sliding member 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 sliding member contact surface 33. However, when the sliding member 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.

[0054] [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.

[0055] 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 sheet 43, and the unvulcanized rubber material G are placed 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.

[0056] The cavity 51a of the upper mold 51 forms 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 shown in Fig. 2. The second portion 44b and the fixing portion 45 of the intermediate portion 44 of the sheet 43 enter the cavity 51a, and the sheet 43 is formed into a shape that fits the inner surface of the cavity 51a.

[0057] 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. A part of the first portion 44a in the intermediate portion 44 of the sheet 43 and 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 a fourth portion 42d of the rubber 42 shown in Fig. 2.

[0058] 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 inside the mold. The unvulcanized rubber material G fills the cavities 51 a, 52 a, and 52 b of the upper mold 51 and the lower mold 52. The unvulcanized rubber material G also enters the voids in 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. By impregnating the sheet 43 with the 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 are integrated together.

[0059] As described with reference to FIG. 4 , the lip portion 48 of the sliding member 15 includes the sliding portion 46 of the sheet 43 and the first portion 42c of the rubber 42, and is elastically deformed by contact with the sliding member contact surface 33 of the inner ring 12. When the outer ring 11 and the inner ring 12 move relative to each other in the axial or radial direction, the relative position of the inner ring 12 and the sliding member 15 changes, and the degree of elastic deformation of the lip portion 48 also changes. If the lip portion 48 does not elastically deform appropriately in response to the change in the relative position of the inner ring 12 and the sliding member 15, the contact between the lip portion 48 and the inner ring 12 will weaken or they will momentarily separate, resulting in a decrease in conductivity of the sheet 43. In this embodiment, the conductivity of the sliding member 15 is improved by increasing the ability of the lip portion 48 to follow the inner ring 12.

[0060] 6 is an enlarged cross-sectional view showing the radially inner portion of the sliding member shown in FIG. 2 in an unloaded state. In this embodiment, as shown in FIG. 6, the ratio of the axial thickness t4 of the lip portion 48 of the sliding member 15 to the axial thickness t5 of the sheet 43 (sliding portion 46) is optimized to improve the conformability of the lip portion 48. Specifically, the ratio of the thickness t5 of the sheet 43 to the thickness t4 of the lip portion 48 is set to 25% or more and 35% or less for the following reason. The thickness t4 of the lip portion 48 corresponds to the depth t6 of the cavity 52a for molding the lip portion 48 in the lower mold 52 shown in FIG. 5.

[0061] Generally, an index called loss sine (tan δ) is used to indicate the dynamic viscoelasticity of elastic bodies such as rubber. This index is expressed by the following formula (1): tan δ = E" / E' (1) where E" is the loss modulus (viscous element) and E' is the storage modulus (elastic element).

[0062] The larger the value of the loss sine of an elastic body, the more viscous the body tends to be, and conversely, the less elastic the body tends to be. The smaller the value of the loss sine of an elastic body, the more elastic the body tends to be, and conversely, the less viscous the body tends to be. Therefore, in order to make the lip portion 48, which is an elastic body, follow the inner ring 12, it is desirable to make the value of the loss sine small.

[0063] 7 is a graph showing the relationship between the ratio of the thickness of the sheet 43 (sliding portion) to the thickness of the lip portion 48 and the loss sine (tan δ). The graph shown in FIG. 7 shows the results when a test piece corresponding to the lip portion 48 of the sliding member 15 was tested using a dynamic viscoelasticity tester. This tester measures the loss modulus and storage modulus by applying vibration to the test piece at a predetermined temperature. In this test, a vibration of 33 Hz was applied at a temperature of 100°C.

[0064] 7, it can be seen that in the region shown by (1), the value of the loss sine gradually decreases, in the region shown by (2), the value of the loss sine is maintained at its lowest, and in the region shown by (3), the value of the loss sine gradually increases. In this embodiment, in order to improve the followability of the lip portion 48 to the inner ring 12, the region shown by (2) where the value of the loss sine is smallest, i.e., the region where the ratio of the thickness of the seat 43 to the thickness of the lip portion 48 is 25% to 35%, is adopted.

[0065] The sheet 43 of the sliding member 15 contains a synthetic resin binder for binding the conductive fibers. The rubber 42 acts as a factor (elastic element) that increases the elasticity of the lip portion 48, while the binder of the sheet 43 acts as a factor (viscous element) that increases the viscosity of the lip portion 48. On the other hand, the rubber 42 itself also has a viscous element, and since the rubber 42 penetrates into the conductive fibers of the sheet 43, the sheet 43 itself also has an elastic element. Therefore, when the ratio of the thickness of the sheet 43 to the thickness of the lip portion 48 changes, the balance between the elastic element and the viscous element of the lip portion 48 changes in various ways.

[0066] Region (1) in Figure 7 is a region where the ratio of the sheet 43 gradually increases from a state where there is no sheet 43 at all in the lip portion 48. Therefore, the ratio of the rubber 42 gradually decreases, and the viscosity of the rubber 42 also decreases (the elastic modulus increases relatively), which is thought to gradually decrease the loss sine. In contrast, in region (2) in Figure 7, as the ratio of the sheet 43 increases, the viscosity due to the binder increases, but the elastic modulus due to the rubber 42 (including the rubber 42 contained in the sheet 43) increases more than that, so it is thought that a balance between the two is maintained and a low loss reduction is maintained. In region (3) in Figure 7, as the ratio of the sheet 43 increases further, the viscosity due to the binder increases more than the increase in the elastic modulus due to the rubber 42, and the influence of the binder increases, which is thought to increase the value of the loss sine.

[0067] As described above, by setting the ratio of the thickness of the sheet 43 to the thickness of the lip portion 48 to be 25% or more and 35% or less, the ability of the lip portion 48 of the sliding member 15 to follow the sliding member contact surface 33 of the inner ring 12 is improved, and the conductivity of the sheet 43 can be increased.

[0068] [Other Embodiments] In the sliding member 15 of the above embodiment, the sliding portion 46 of the sheet 43 is disposed on the second axial side of the lip portion 48, and the first portion 42 c of the rubber 42 is disposed on the first axial side of the sliding portion 46. However, the sliding portion 46 of the sheet 43 may be disposed on the first axial side of the lip portion 48, and the first portion 42 c of the rubber 42 may be disposed on the second axial side of the sliding portion 46.

[0069] In the sliding member 15 of the above embodiment, 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.

[0070] In the rolling bearing 10 of the above embodiment, the outer ring 11 is a fixed ring and the inner ring 12 is a rotating ring. However, the present invention may also be applicable to a case where the outer ring 11 is a rotating ring and the inner ring 12 is a fixed ring.

[0071] The sliding member 15 in the above embodiment is fixed to the outer ring 11, which is the first member, and is in slidable contact with the inner ring 12, which is the second member. However, in the present invention, the sliding member 15 may be fixed to the inner ring 12, which is the first member, and be in slidable contact with the outer ring 11, which is the second member.

[0072] In the sliding member 15 of the above embodiment, 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 above 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.

[0073] In the above 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.

[0074] 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.

[0075] 10: Rolling bearing 11: Outer ring 12: Inner ring 13: Rolling element 15: Sliding member 21: Outer ring raceway 31: Inner ring raceway 41: Metal ring 42: Rubber 42c: First portion 42a: Second portion 42b: Third portion 42d: Fourth portion 43: Seat 44: Intermediate portion 45: Fixed portion 46: Sliding portion 48: Lip portion

Claims

1. A sliding member comprising: a sheet which is a nonwoven or woven fabric formed from conductive fibers; a metal ring; and rubber, wherein the sheet integrally comprises: a fixed portion which is fixed in contact with a first member made of steel on a first radial side of the metal ring; a sliding portion which is in slidable contact with a second member made of steel on a second radial side; and an intermediate portion located between the fixed portion and the sliding portion; the rubber has a first portion bonded to the sliding portion; and the ratio of the axial thickness of the sliding portion to the axial thickness of the sliding member including the sliding portion and the first portion is 25% or more and 35% or less.

2. A sliding member according to claim 1, wherein the metal ring is disposed on a first axial side of the sheet at a distance, and the rubber has a second portion disposed on the first radial side of the first portion at the distance.

3. A sliding member according to claim 2, wherein the rubber further comprises a third portion disposed on the first radial side of the second portion, and the first, second, and third portions are bonded to the entire first axial side of the sheet.

4. A sliding member according to claim 2 or 3, wherein the rubber has a fourth portion that extends beyond the end of the metal ring on the second radial side and is positioned on the first axial side of the metal ring.

5. A rolling bearing comprising: an inner ring having an inner ring raceway; an outer ring having an outer ring raceway arranged radially outward of said inner ring raceway; a plurality of rolling elements arranged to be able to roll between said inner ring raceway and said outer ring raceway; and a sliding member according to any one of claims 1 to 3 arranged radially between an axial end of said inner ring and an axial end of said outer ring, wherein one of said inner ring and said outer ring is said first member, and the other of said inner ring and said outer ring is said second member.

6. A rolling bearing according to claim 5, wherein the sheet of the sliding member is arranged closer to the rolling elements than the metal ring and the rubber in the axial direction.

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