GB2096262A - An adjustable length clutch release bearing assembly - Google Patents

Abstract

An adjustable length release bearing assembly for a pull type clutch and which comprises two telescopic sleeves (12) and (14), one sleeve (14) is attached to a release bearing (15) and the other sleeve (12) is engageable with the fingers (18) of a diaphragm spring. The length of the release bearing assembly is determined by the overlap between the two sleeves (12) and (14). A lock means (26), (27), (28) generally prevents telescoping movement between the sleeves (12) and (14) and is releasable to allow adjustment to take place when the load in the diaphragm spring (18) pulls the lock means against an abutment (29) on the clutch cover (17). A substantially constant clearance can thus be maintained between the release bearing and brake disc (20) despite wear of the clutch. <IMAGE>

Description

SPECIFICATION An adjustable length clutch release bearing assembly This invention relates to release bearing assemblies for pull type friction clutches in which a driven plate is clamped between a flywheel and a clutch cover assembly and in which in order to release the driven plate a release bearing is moved axially away from the cover assembly and operates through a cover assembly member to remove the clamp load on the driven plate. Such a release bearing assembly will hereinafter be referred to as a release bearing assembly of the kind referred.

A problem with pull type friction clutches is that as the friction clutch driven plate wears the radially inner ends of the clutch release lever in the case of a coil spring clutch or the inner ends of the diaphragm spring fingers in the case of a diaphragm spring clutch, move axially towards the driven plate. If the release bearing assembly is of the type which has a friction surface on the stationary race thereof for engagement with a brake disc on the input shaft of a gearbox in order to slow down the rotation of parts in the gearbox when the transmission drive is disconnected, then as the clutch disc wears the distance between the release bearing and the brake disc on the gearbox input shaft alters.

The object of the present invention is to provide an adjustable length release bearing assembly which can maintain a substantially constant clearance between the release bearing and a brake disc.

Accordingly there is provided a release bearing assembly of the kind referred which has an adjustable length, wherein the release bearing assembly includes two co-axial telescopic sleeves, one sleeve being attached to the release bearing and the other sleeve being engageable with said cover assembly member so that the overall effective length of the bearing assembly is determined by the axial overlap of the sleeves, and a lock means that prevents telescopic movement between the sleeves and which is releasable when the clamp load pulls the lock means against the cover assembly allowing the two sleeves to move telescopically to alter the overall effective length of the bearing assembly and relieve the clamp load on the lock means.

Preferably the outer sleeve is attached to the release bearing, and the locking means comprises two belleville spring washer working in opposition to each other and only one of said belleville springs is simultaneously engageable with both sleeves to lock the two sleeves in their mutual positions.

The invention will be described by way of example and with reference to the accompanying drawing in which: Fig. 1 is a longitudinal section through one form of release bearing assembly according to this invention; and Fig. 2 is a section through a second type of release bearing according to this invention.

With reference to Fig. 1 of the accompanying drawings, a shaft 11 is a gearbox input shaft which has a brake disc 20 secured rotationally fast therewith. The disc 20 can react back onto a gearbox housing (not shown). A friction clutch cover assembly includes an annular cover 1 7 which is fast with a motor vehicle internal combustion engine flywheel (not shown) and cover assembly member(s) 1 8 which is/are operable to release the clamp load on a clutch driven plate (not shown). In the case of a coil spring clutch, the member(s) 1 8 would be release levers, and in the case of a diaphragm spring clutch the member(s) 1 8 would be the diaphragm spring fingers.

The radially inner ends of the clutch assembly member(s) are attached to a sleeve 1 2 which is co-axial with the input shaft 11 and extends through the centre of the cover 1 7 towards the gearbox. The sleeve 12 is part of a release bearing assembly and has bearing bushes 13 on its inner surface for contact with the shaft 11. A second coaxial outer sleeve 14 is telescopically mounted around the inner sleeve 11 and is located outside the cover 1 7.

The outer sleeve 14 is secured iotationally fast to the rotary race of a clutch release ball bearing 15, the stationary race of which is held in a housing 16. The housing 1 6 is connected to and held stationary by a clutch release fork (not shown) and carries a friction surface 1 9 thereon for engagement with the brake disc 20 on the input shaft 11.

.The end portion of the outer sleeve 14 adjacent the cover 17, carries thereon an annular co-axial spring housing 23 and retainer ring 22. A pair of opposed belleville spring washers 26 and 27 surround the inner sleeve 12 and are arranged with their smaller diameter tops facing each other and separated by a fulcrum ring 28. The outer peripheral portions of the spring washers 26 and 27 are retained in tiie housing 23 and the inner peripheries of the washers 26 and 27 lie adjacent the inner sleeve 12.

The two sleeves, 12 and 14, the bearing 1 5 and its housing 16 and the spring housing 23 and springs 26 and 27, all form a clutch release bearing assembly. The cover 1 7 has a co-axial annular projection 29 which surrounds the inner sleeve 12 and against which the belleville spring washer 26 can abut. The internal diameter of the washer 26 is such that it can engage the sleeve 12 whereas the internal diameter of the other washer 27 is such it can never engage with the surface of the sleeve 12. When the washer 26 engages the inner sleeve 12 the two sleeves 12 and 14 are locked axially together and when the washer 26 disengages from the inner sleeve the two sleeves 12 and 14 can move telescopically.

With the clutch in the engaged state the clamping load exerted by the clutch springs (coil or diaphragm depending upon type of clutch) on the driven plate causes the clutch assembly members to draw the sleeve 12 to the left, causing the inner periphery of spring 26 to abut the projection 29. This lifts the inner periphery of the washer 26 away from the sleeve 12 so that the two sleeves 1 2 and 14 are telescopic. This is the position shown in Fig. 1.

When the clutch is disengaged the release bearing 1 5 and its housing 1 6 are moved to the right by the release fork, pulling the sleeve 14, spring housing 23, and the springs 26 and 27 with them. The sleeve 14 slides over the sleeve 12 until the spring washer 26 is moved away from the projection 29. At this point the other spring washer 27, acting through the fulcrum ring 28 applies a load to the spring washer 26 causing its inner periphery to engage the sleeve 12 and lock the sleeves 12 and 14 mutually in position. Extra movement rightwards of the bearing housing 1 6 causes the locking action of the washer 26 to increase, moves the inner sleeve 12 further nghtwards and disengages the clutch driven plate.

This movement continues until the friction surface 19 engages the brake disc on the input shaft 11, thereby braking the rotation of the input shaft.

This is necessary with some heavy commercial vehicle gearboxes. The clearance S between the disc 20 and the friction surface 1 9 when the clutch is engaged should be kept substantially constant for a difficult braking of the input shaft.

When the clutch is re-engaged the whole release bearing assembly moves back leftwards under the bias of the clutch spring(s), until the spring washer 26 comes into abutment with the projection 29. If wear has taken place on the clutch driven plate then the clamp load in the clutch spring(s) will still act through the cover assembly member(s) 1 8 on the inner sleeve 1 2.

This clamp load overcomes the load in the spring washer 27 and causes the spring washer 26 to deform against the projection 29 and release the inner sleeve 12, allowing the clamp load to draw the sleeve 12 towards the driven plate and out of the sleeve 14 and increase overall effective length of the release bearing assembly.

Thus although wear has taken place on the driven plate, causing the radially inner ends of the cover assembly members 1 8 to move away from the cover 17, the clearance S is maintained substantially constant.

Fig. 2 shows a clutch release bearing assembly, very similar to that shown in Fig. 1 and those parts substantially identical with the parts in Fig. 1 have been given the same number. The outer sleeve 114 has been modified to accommodate two opposed belleville spring washers 126 and 127 which are arranged base-to-base with a fulcrum ring 28 located between the two outer peripheral portions. The spring housing 1 23 is formed from a cylindrical pressing which is a push fit on the outer sleeve 114 and has radial tabs 122 turned over to retain the spring washers 126 and 127 in position in the housing 123.

The cover 1 7 has inner radial projections that interdigitate with the tabs 122 to act against spring 126. The housing 123 also has axial lugs 131 thereon that pass through apertures in the cover 1 7 so that the outer sleeve 114 is always locked rotationally fast with the cover.

The adjuster mechanism in Fig. 2 is similar to that used in Fig. 1. On release of the clutch driven plate the spring washer 126 is moved away from the cover 1 7 and the other spring washer 127 causes the spring washer 126 to engage with the sleeve 12.

On re-engagement of the clutch the abutment of the washer 126 against the cover 1 7 causes the washer 1 26 to release the sleeve 1 2.

Claims (6)

1. An adjustable length release bearing assembly for a pull type friction clutch in which a driven plate is clamped between a flywheel and a clutch cover assembly and in which in order to release the driven plate a release bearing is moved axially away from the cover assembly and operates through a cover assembly member to remove the clamp load on the driven plate, said release bearing assembly including two co-axial telescopic sleeves, one sleeve being attached to the release bearing and the other being engageable with said cover assembly member so that the overall effective length of the release bearing assembly is determined by the axial overlap of the sleeves, and a lock means that prevents telescopic movement between the sleeves and which is releasable when the clamp load pulls the lock means against the cover assembly allowing the two sleeves to move telescopically to change the overall effective length of the bearing assembly and relieve the clamp load on the lock means.

2. An assembly as claimed in Claim 1, wherein the lock means comprises two belleville spring washers acting in opposition to each other, and only one of said washers is simultaneously engageable with both sleeves to axially lock the two sleeves together.

3. An assembly as claimed in Claim 2, wherein a fulcrum ring is located between the two belleville spring washers.

4. An assembly as claimed in Claim 2 or Claim 3, wherein said one of the belleville washers is retained on the outer sleeve and effects engagement with the inner sleeve to lock the two sleeves together.

5. An assembly as claimed in any preceding claim, wherein at least one axial projection on the cover or outer sleeve extends into an aperture in the other of the cover or sleeve so as to rotationally secure the outer sleeve to the cover assembly.

6. An adjustable length release bearing assembly for a pull type clutch and which is substantially as described herein and with reference to Fig. 1 and Fig. 2 of the accompanying drawings.