GB2156472A

GB2156472A - Clutch release bearing

Info

Publication number: GB2156472A
Application number: GB08408126A
Authority: GB
Inventors: Hubert Walter Thomas Neal; Gordon Beton
Original assignee: Svenska Kullagerfabriken AB
Current assignee: SKF AB
Priority date: 1984-03-29
Filing date: 1984-03-29
Publication date: 1985-10-09
Also published as: GB8408126D0

Abstract

A self-centering thrust bearing assembly for use as a clutch release device between the engine and gear box of a motor vehicle, comprises a deep groove ball bearing and a cylindrical support 10 extending with clearance through the bore of the bearing, one of the bearing rings of the bearing being held by magnetic force against an annular flange 16 on the support. The support 10 may be made of magnetic material and the inner bearing ring 21 permanently magnetized to provide North and South magnetic poles in an end face of the inner bearing ring around the periphery thereof, the end face of the inner bearing ring abutting against the flange 16 on the support. A ring of high friction material may be interposed between the end face of the inner bearing ring 21 and the radial flange 16. Alternatively one of the bearing rings may be fitted into a casing of magnetic material and the support fitted with a ring magnet, the casing on the bearing being held against the ring magnet by magnetic adhesion. <IMAGE>

Description

SPECIFICATION Self-centering thrust bearing assemblies This invention relates to self-centering thrust bearing assemblies, and is concerned more particularly but not exclusively to thrust bearing assemblies suitable for use as a clutch release device.

The object of the invention is to provide an improved self-centering thrust bearing assembly which is simple in construction.

According to the present invention there is provided a self-centering thrust bearing assembly comprising a support and a bearing mounted on the support, the bearing comprising an outer annular bearing member, and inner annular bearing member, and a plurality of rolling elements disposed between the two bearing members and in rolling engagement with grooved tracks on the two bearing members so that the rolling elements can transmit radial and axial thrust between the two bearing members, wherein the support has a radial abutment adjacent an end face of one of the bearing members, and the assembly includes magnetic means which urge said one bearing member in a direction to engage the said end face on the one bearing member against the radial abutment, and an axial abutment which is spaced radially from a periphery of the bearing and permits a small amount of freedom of radial movement of the bearing relative to the support when the bearing is subjected to a radial force in excess of the frictional sliding resistance between the said end face on the one bearing member and the radial abutment.

The self-centering thrust bearing assembly of the invention is particularly suitable for use as a release device for a clutch between the engine and gearbox of a motor vehicle. When in use for this purpose, the support is preferably slidably and non-rotatably mounted on a component of the gearbox. The above mentioned one bearing member is held against the radial abutment on the support by magnetic adhesion and axial thrust applied to the support moves the bearing axially relative to the gearbox component so as to displace the release elements of the clutch by the other bearing member. The radial freedom of movement of the bearing relative to the support permits self-alignment of the bearing with respect to the clutch to compensate for any misalignment between the engine and the gearbox.

In the thrust bearing assembly of the invention, at least part of the above mentioned one bearing member and at least part of the support can conveniently be formed of magnetic material, at least one of these parts being magnetised so as to urge the bearing member towards the radial abutment. The end face of the one bearing member is preferably magnetised to form alternate North and South magnetic poles at the end face around the periphery thereof. This arrangement of magnetic poles reduces the risk of stray magnetic fields in the bearing assembly which might attract metallic dirt.

The end face of the one bearing member and/or the adjacent face of the radial abutment may have high friction characteristics so as to increase the radial force necessary to overcome the adhesive magnetic force between the bearing member and the support.

Conveniently, the support can comprise a cylindrical member fitted with an annular disc, the cylindrical member forming the axial abutment and the annular disc forming the radial abutment, the disc having high surface friction characteristics. The annular disc may comprise a pernanent magnet and can then conveniently be secured to either the support or the bearing member.

The bearing is preferably provided with seals for preventing entry of foreign matter into the annular space between the bearing members.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross section of a clutch release device incorporating a self-centering thrust bearing assembly according to the invention, Figure 2 is a developed view of part of the inner bearing ring of the bearing assembly of Figure 1, and part of a device for magnetising the inner bearing ring, Figure 3 is a cross section of a modification of the clutch release device of Figure 1, and Figure 4 is a cross section of another construction of clutch release device incorporating a self-centering thrust bearing assembly according to the invention.

The clutch release device shown in Figure 1 comprises an annular support member 10, and a radial deep groove ball bearing 11 fitted with an outer casing 1 2.

The annular support member 10 has a cylindrical portion 1 5 at one end thereof, a central annular flange 1 6 adjoining the inboard end of the cylindrical portion 15, and a further annular flange 1 7 at the other end of the support member 10, the two flanges 1 6 1 7 co-operating to define an annular channel 1 8 for reception of an actuating fork (not shown). The bearing 11 comprises an outer bearing ring 20 rotatably mounted on an inner bearing ring 21 by a plurality of balls 22 in rolling engagement with grooved tracks on the two bearing rings, so that the balls can transmit axial and radial thrust between the two bearing rings.Two seals 23 are mounted one on each side of the outer bearing ring, the inner peripheries of the seals being in sliding sealing engagement with the inner bearing ring. The bore of the inner bearing ring 21 has a diameter which is significantly larger than the external diameter of the cylindrical portion 1 5 of the support member, and the bearing is arranged so that it surrounds the cylindrical portion 1 5. There is thus a radial clearance 24 between the inner bearing ring 21 and the cylindrical portion 1 5 when the inner bearing ring is co-axial with the support member.The end face 25 of the inner bearing ring which is adjacent the flange 1 6 lies in a radial plane relative to the axis of the bearing, and the end face 26 of the annular flange 1 6 which is adjacent the inner bearing ring lies in a radial plane relative to the axis of the support member, so that the two end faces 25, 26 can engage flat against each other when the axes of the bearing and the support member are parallel to one another. The outer casing 12 comprises a cylindrical portion 27, an inwardly projecting annular radial portion 28 integral with one end of the cylindrical portion 27, and an annular radial flange 29 integral with the radial portion 28 but offset axially outwards.

The outer casing may be formed into shape by pressing or forging. The cylindrical portion 27 of the outer casing is an interference fit on the outer bearing ring, with the radial portion 28 abutting the outer end face of the outer bearing ring.

In accordance with the invention, the support member 10 and the inner bearing ring 21 are formed of magnetic material, and alternate North and South magnetic poles are induced permanently in the end face 25 of the inner bearing ring 21 around the periphery thereof, so that the inner bearing ring is urged by magnetic force towards the annular flange 1 6 on the support member and is held there-against by magnetic adhesion. The annular flange 1 6 then acts as a radial abutment for transmitting axial thrust between the support member and the inner bearing ring.The radial clearance 24 between the bore 23 of the inner bearing ring and the cylindrical portion 1 5 of the support member permits radial movement of the bearing relative to the support member with the end face 25 of the inner bearing ring sliding over the end face 26 of the flange 16, and allows the bearing to centre itself relative to any member to which it is transmitting axial thrust within the limits of the radial clearance 24. Radial movement between the bearing and the support member will of course only take place if the radially acting centering force is greater than the frictional force acting between the two faces 25, 26 as a result of the magnetic adhesion between the bearing ring and the support member.The cylindrical portion 1 5 of the support member acts as an axial abutment which limits the degree of freedom of radial movement of the bearing relative to the support member.

The clutch release device of Figure 1 is designed for use in a motor vehicle having a clutch between the engine and gearbox. In use, the annular support member 10 is mounted on a component of the gearbox for axial movement thereon but is restrained against rotational movement, and the flange 29 on the outer casing of the bearing is positioned against or adjacent the disengaging elements of the clutch. An actuating fork is engaged in the annular channel 18. The clutch is disengaged by actuating the fork so as to impart axial thrust to the flange 1 6 on the support member and thereby move the support member 10, the bearing 11 and the outer casing 1 2 in a direction to displace the clutch disengaging elements.The axial thrust imparted by the fork is transmitted through the flange 16, the inner bearing ring 21, the balls 22 engaged in their grooved tracks, the outer bearing ring 20, and the outer casing 1 2. In the event that the bearing is out of alignment with the axis of rotation of the clutch, the frictional sliding forces between the clutch disengaging elements and the flange 29 on the outer casing of the bearing will exert on the bearing a radial force which will cause the inner bearing ring 21 to slide across the flange 1 6 into a position in which the bearing is centered relative to the axis of rotation of the clutch.

The clutch release device of Figure 1 is of simple construction with a short axial length, and when it is mounted in position on a component of a gearbox in a motor vehicle, the bearing together with the outer casing 12 can be replaced when worn or damaged by a new bearing fitted with an outer casing without removing the support member 10 from the gearbox component.

A device 30 for magnetising alternate North and South magnetic poles in the end face 25 of the inner bearing ring is illustrated diagrammatically in developed form in Figure 2.

The device comprises a ring 31 formed around a side face thereof with a succession of cores 32 of magnetic material arranged with their axes parallel to the axis of the ring 31 and spaced around a pitch circle having a diameter approximately equal to the median diameter of the inner bearing ring Each core has an electrical winding 33, the windings of alternate cores around the periphery of the device being of opposite hand. The magnetic poles are permanently induced in the end face 25 of the inner bearing ring by holding the device against the bearing ring with the cores abutting the face 25 and then energising the windings of the cores. The bearing ring can conveniently be magnetised after the balls have been fitted between the two rings to form the bearing and immediately before the bearing is mounted on the support member.

The arrangement of alternate North and South magnetic poles around the periphery of the bearing ring in the completed bearing as sembly reduces the risk of stray magnetic fields which would tend to attract metallic dirt.

The clutch release device shown in cross section in Figure 3 is similar to that of Figure 1 and like parts are denoted by like reference numerals. The device of Figure 3 however includes a thin annular intermediate member 35 disposed between the end face 25 of the inner bearing ring and the adjacent end face 26 of the annular flange 22, the intermediate member 35 having high surface friction characteristics. The device of Figure 3 has the advantage that a substantially larger radial centering force is necessary to overcome the adhesive magnetic force between the bearing ring and the support member, than is the case with the assembly of Figure 1.

The clutch release device showm in Figure 4 comprises a sleeve 40 one end of which is turned radially outwards to form an annular radial flange 41, an annular support member 42 firmly secured on the sleeve 40 with one end thereof abutting the flange 41, the support member having an annular radial flange 43 intermediate its ends, a ring shaped magnet 44 which is mounted on the other end of the support member and is secured to the radial flange 43, and a radial deep groove ball bearing 45 fitted with an annular outer casing 46 and an annular inner casing 47.

The annular support member 42 may be formed of steel and the magnet 44 bonded to the radial flange 43. Alternatively, the support member 42 may be moulded in plastics material and the magnet embedded in the support member during the moulding operation.

The ball bearing 45 is similar to the ball bearing 11 of the device of Figure 1 and comprises an outer bearing ring 50, an inner bearing ring 51, a plurality of balls 52 disposed between the two rings and in rolling engagement with grooved tracks on the two bearing rings, and two seals 54 mounted one on each side of the outer bearing ring, the inner peripheries of the seals being in sliding sealing engagement with the inner bearing ring.

The outer casing 46 is made of magnetic material and comprises a cylindrical portion 56, an inwardly projecting annular radial portion 57 integral with one end of the cylindrical portion 56, and an annular radial flange 58 integral with the radial portion 57 but offset axially outwards therefrom. The outer casing may be formed into shape by pressing or forging. The cylindrical portion 56 of the outer casing is an interference fit on the outer bearing ring 50 and the radial portion 57 abuts against the adjacent end face of the outer bearing ring.

The inner casing 47 comprises a cylindrical portion 60, an outwardly projecting annular radial portion 61 integral with one end of the cylindrical portion 60, and an annular radial flange 62 integral with the radial portion 61 but offset axially outwards. The inner casing may be formed into shape by pressing or forging. The cylindrical portion 60 of the inner casing is a press fit in the bore of the inner bearing ring with the radial portion 61 and the flange 62 on the opposite side of the bearing from the flange 58 of the outer casing and with the radial portion 61 abutting the adjacent end face of the inner bearing ring.

The bearing 45, together with the outer and inner casings 46, 47, surrounds the end portion of the sleeve 40 remote from the flange 41, with the flange 58 on the outer casing engaged flat against the magnet 44, and the bearing is held in position by the magnetic adhesion between the outer casing 46 and the magnet. The inner periphery of the annular flange 58 has a larger diameter than that of the external surface of the adjacent end of the support member 42, and the inner surface of the inner casing 47 has a larger diameter than that of the external surface of the sleeve 40 so that the bearing 45, together with the outer and inner casings 46, 47, is free to move radially relative to the sleeve within the limits of the radial clearance between the bearing and the sleeve.

The clutch release device of Figure 4, when in use in a motor vehicle having a clutch between the engine and gearbox, has the sleeve 40 mounted on a component of the gearbox for axial movement thereon but restrained against rotational movement, and the flange 62 on the inner casing of the bearing positioned against or adjacent the disengaging elements of the clutch. An actuation fork is engaged in the annular channel 65 formed between the radial flange 41 on the sleeve and the radial flange 43 on the support member.

The clutch is disengaged by actuating the fork so as to impart axial thrust to the flange 43 on the support member and thereby move the sleeve 40 and the flange 62 in a direction to displace the clutch disengaging elements.

The axial thrust imparted by the fork is transmitted through the magnet 44, the outer casing 46, the outer bearing ring 50, the balls 52 engaged in their grooved tracks, the inner bearing ring 51 and the inner casing 47. In the event that the bearing is out of alignment with the axis of rotation of the clutch, the frictional sliding forces between the clutch disengaging elements and the flange 62 on the inner casing of the bearing will exert on the bearing a radial force which will cause the flange 58 to slide across the magnet 44 into a position in which the bearing is centered relative to the axis of rotation of the clutch.

In the clutch release device of Figure 4, the magnet 44 may if desired be secured to the flange 58 on the outer casing of the bearing instead of to the flange 43 on the support member.

The embodiments described above are given by way of example and may be modified without departing from the invention as defined in the following claims. For example, the abutment which limits radial movement of the bearing, that is the cylindrical portion 1 5 in the device of Figures 1 and 3 and the end portion of the sleeve 40 remote from flange 41 in the device of Figure 4, may be provided by a part of the gearbox.

Claims

1. A self-centering thrust bearing assembly comprising a support and a bearing mounted on the support, the bearing comprising an outer annular bearing member, an inner annular bearing member, and a plurality of rolling elements disposed between the two bearing members and in rolling engagement with grooved tracks on the two bearing members so that the rolling elements can transmit radial and axial thrust between the two bearing members, wherein the support has a radial abutment adjacent an end face of one of the bearing members, and the assembly includes magnetic means which urge said one bearing member in a direction to engage the said end face of the one bearing member against the radial abutment, and an axial abutment which is spaced radially from a periphery of the bearing and permits a small amount of freedom of radial movement of the bearing relative to the support when the bearing is subjected to a radial force in excess of the frictional sliding resistance between the said end face on the one bearing member and the radial abutment.

2. A self-centering thrust bearing assembly as claimed in claim 1, wherein at least part of said one bearing member and at least part of the support are formed of magnetic material, and at least one of the said parts is magnetised so as to urge the bearing member towards the radial abutment.

3. A self-centering thrust bearing assembly as claimed in claim 2, wherein the said end face of the one bearing member is magnetised to form alternate North and South magnetic poles at the end face around the periphery thereof.

4. A self-centering thrust bearing assembly as claimed in any of claims 1-3, wherein said end face of the one bearing member and/or the adjacent face of the radial abutment have high friction characteristics.

5. A self-centering thrust bearing assembly as claimed in any of claims 1-4, wherein the support comprises a cylindrical member fitted with an annular disc, the cylindrical member forming the axial abutment and the annular disc forming the radial abutment, said disc having high surface friction characteristics.

6. A self-centering thrust bearing assembly as claimed in any of claims 1-4, wherein the support comprises a cylindrical member fitted with an annular pernanent magnet, the cylindrical member forming the axial abutment and the magnet forming the radial abutment.

7. A self-centering thrust bearing assembly substantially as hereinbefore described with reference to Figure 1 or 3 of the accompanying drawings.

7. A self-centering thrust bearing assembly as claimed in any of the preceding claims, wherein the outer bearing member comprises an outer bearing ring formed with one of said grooved tracks, and an outer casing secured on the outer bearing ring and formed with an inwardly projecting annular flange, and the inner bearing member comprises an inner bearing ring formed with one of said grooved tracks, and an inner casing secured on the inner bearing ring and formed with an outwardly projecting annular flange, the two annular flanges being on opposite sides of the bearing, and the annular flange adjacent the radial abutment being made of magnetic material and forming part of said magnetic means.

8. A self-centering thrust bearing assembly as claimed in any of the preceding claims, wherein the bearing is provided with seals for preventing entry of foreign matter into the annular space between the bearing members.

9. A self-centering thrust bearing assembly as claimed in any of the preceding claims and forming a clutch release device for a clutch between the engine and gearbox of a motor vehicle, wherein the support comprises a sleeve slidably and non-rotatably mounted on a component of the gearbox.

10. A self-centering thrust bearing assembly as claimed in any of claims 1-4 and forming a clutch release device for a clutch between the engine and gearbox of a motor vehicle, wherein the support comprises a sleeve slidably and non-rotatably mounted on a component of the gearbox, and a part of the gearbox forms said axial abutment.

11. A self-centering thrust bearing assembly substantially as hereinbefore described with reference to any of Figures 1, 3, 4 of the accompanying drawings.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1 to 11 above have been deleted.

New or textually amended claims have been filed as follows:

1. A self-centering thrust bearing assembly comprising a support and a bearing mounted on the support, the bearing comprising an outer annular bearing member, an inner annular bearing member, and a plurality of rolling elements disposed between the two bearing members and in rolling engagement with grooved tracks on the two bearing members so that the rolling elements can transmit radial and axial thrust between the two bearing members, wherein the support has a radial abutment adjacent an end face of one of the bearing members, at least part of the radial abutment and said one bearing member being formed of magnetic material, and the radial abutment and/or said one bearing member being magnetized so that the bearing member is urged by magnetic attraction in a direction to engage said end face thereof against the radial abutment, and an axial abutment is spaced radially from a periphery of the bearing and permits a small amount of freedom of radial movement of the bearing relative to the support when the bearing is subjected to a radial force in excess of the frictional sliding resistance between the said end face on the one bearing member and the radial abutment.

2. A self-centering thrust bearing assembly as claimed in claim 1 wherein said one bearing member is magnetized to form alternate North and South magnetic poles at said end face around the periphery thereof.

3. A self-centering thrust bearing assembly as claimed in claim 1 or 2, wherein the support has a cylindrical portion formed with an annular flange, the cylindrical portion extending through the bore of the inner bearing member and forming said axial abutment, and the annular flange extending radially outwards past an end face of the inner bearing member and forming said radial abutment, the inner bearing member being magnetized.

4. A self-centering thrust bearing assembly as claimed in claim 3, wherein an annular disc is mounted on said cylindrical portion between the inner bearing member and said radial flange so that the disc is clamped between the inner bearing member and the radial flange by the magnetic attraction therebetween, said disc having high surface friction characteristics.

5. A self-centering thrust bearing assembly as claimed in any of the preceding claims, wherein the bearing is provided with seals for preventing entry of foreign matter into the annular space between the bearing members.

6. A self-centering thrust bearing assembly as claimed in any of the preceding claims and forming a clutch release device for a clutch between the engine and gearbox of a motor vehicle, wherein the support comprises a sleeve slidably and non-rotatably mounted on a component of the gearbox.