GB2195719A

GB2195719A - Friction clutch cover assembly

Info

Publication number: GB2195719A
Application number: GB08623663A
Authority: GB
Inventors: Graham John Shirley
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-10-02
Filing date: 1986-10-02
Publication date: 1988-04-13
Also published as: GB8623663D0

Abstract

In a friction clutch cover assembly 2, the cover 4 is formed with radially extending tabs 28A, 28B which hold a fulcrum ring 30 adjacent to a diaphragm spring 20. Certain ones of the tabs, namely the tabs 28B, are radially outwardly longer than the tabs 28A and have outer ends forming stops 34 which engage a lip arrangement 34 on the pressure plate in direction A out of the cover. The tabs 28B can be substantially equi-angularly spaced apart, and preferably there are at least three of them. <IMAGE>

Description

SPECIFICATION Friction clutch cover assembly This invention concerns a friction clutch cover assembly of the type (hereinafter called the type referred to) intended, in use, to be rotated about an axis with a rotably driven driving plate and to releasably clamp a driven plate against the driving plate, said clutch cover assembly comprising a cover, a pressure plate moveable relatively to the cover along said axis in first and second opposite directions, a diaphragm spring acting between the pressure plate and the cover to apply a load to the pressure plate to urge the latter in said first direction for clamping a said driven plate against a said driving plate, said diaphragm spring having a plurality of radially inwardly directed fingers separated by radial slots, and said cover being provided with tabs extending through at least some of said slots.

British Patent No. 1514297 discloses a clutch cover assembly of the type refered to in which the tabs are used to retain the diaphragm spring and to retain a pair of fulcrum rings one on each side of the diaphragm. That patent also describes a plurility of tangentially extending resilient straps or leaf springs each secured at one end to the cover and at the other end to the pressure plate, such straps known per se serve the function of transmitting rotary drive motion from the cover to the pressure plate and vice-versa and also act as release springs to pull back the pressure plate in the second direction when a force applied to the fingers of the diaphragm spring causes the urging load it applies to the pressure plate to be relieved.If such driveftelease straps become overstressed by excessive movement of the pressure plate in the first direction (for example if the clutch cover assembly is dropped with the pressure plate preceding the diaphragm spring) the overstressed straps cannot pull back the pressure plate sufficiently in the second direction during attemped clutch releases, and the clutch remains at least partially engaged. Consequently excessive wear of friction facings on the driven plate can occur, and the chance of heat spotting of the driving and pressure plate is increased as well as the likelyhood of increased wear thereof.

But even more importantly, when the clutch assembly is used in a clutch between an engine and a change-speed gearbox in a motor vehicle drive line, the inability to disengage the clutch makes gear changing impossible.

An object of the invention is to provide a clutch cover assembly of the type referred to which can be constructed to avoid excessive movement of the pressure plate in the first direction.

According to the invention a clutch cover assembly of the type referred to further comprises at least one of said tabs being arranged as a stop, and the pressure plate being provided with abutment means mounted thereon to engage said stop to prevent travel of the pressure plate beyond a desired pre-determined position in said first direction.

The or each tab arranged as a said stop may extend, with respect to said axis, radially outwardly beyond other said tabs.

The abutment means may be provided by a wall of a recess in the pressure plate.

The tabs may be used to retain at least one annular fulcrum arrangement for the diaphragm spring.

The invention will now be further described, by way of example, with reference to the accompanying drawing in which: Fig. 1 is a diagrammatic and fragmentary section of a clutch cover assembly formed according to the invention, the section being taken on a diameter of the assembly to one side of a diametral plane at right angles to said diameter; Fig.2 is a plan view of a fragment of the pressure plate in Fig.1, and Fig.3 is a plan view, similar to Fig.2, of a modification of the pressure plate.

With reference to the drawing, the clutch cover assembly 2 has a dish shaped cover 4, which may be pressed steel, of a generally cylindrical shape with a rim flange 6 at one end, and at the opposite end an end wall 8 with a central substantially circular hole 10 substantially centred on an axis X of the cover assembly. The assembly 2 further comprises an annular pressure plate 12 provided with an annular rib arrangement 14 forming a fulcrum 16 engaged by a circumferential Belleville portion 18 of a diaphragm spring 20.

In known manner that diaphragm spring has a plurality of fingers 22 each extending radially inwardly from the Belleville portion 18 and separated by radial slots 24 each enlarged to form a notch 26 adjacent to the Belleville portion.

At its inner periphery the cover end wall 8 is formed with a plurality of tabs 28 comprised by tabs 28A and 28B. Each tab 28 is bent axially from wall 8 to extend through a respective said notch 26 in the diaphragm spring and then the free end portions of the tabs are bent to extend generally radially outwardly with respect to axis X. The tabs 28 serve to retain annular fulcrum arrangements 30 and 32, for example steel wire rings, at opposite sides of the diaphragm spring 20.

The radially shorter tabs 28A may be of any known type. Whereas the tabs 288 are novel in comparison, by at least being extended radially outwardly to form stops 34 for the pressure plate which has lip means 36 forming abutments on the radially inwardly facing side of the rib arrangement 14. The lip means 36 overlie the tips of the stops 34. Therefore the extent to which the pressure plate 12 can move in direction A is limited by the abut ments 36 coming into contact with the stops 34. There could be only one extended tab 288 and therefore only one stop 34, but preferably there are a plurality of extended tabs 28B. Preferably the plurality of tabs 28B are substantially equi-angularly spaced apart one from another, and at least three such tabs is an appropriate array.The cover assembly is provided with resilient, drive/release straps known per se (not shown) extending generally tangentially to the pressure plate 12 and secured thereto and to the cover. Thus when a clutch release bearing known per se (not shown) urges the fingers 22 in the direction A,the drive/release straps pull the pressure plate back in direction B.

In Fig.2 the tabs 28 are represented by dotted lines. As can be seen the abutments 36 can, circumferentially, be relatively short so that before the drive/release straps are finally secured in place, the pressure plate can be rotated to bring the abutments 36 to overlie the stops 34. In Fig.3 the abutments 36A are relatively long circumferentially, essentially forming a side wall of a groove in the rib 14 with interuptions 38 in that side wall so that the stops 34 can be fitted bayonet fashion behind the abutments 36A before the final securing of the drive/release straps.

In use the rim flange can be secured in known manner to a rotatably driven driving plate 40, for example a fly-wheel of a motor vehicle engine. A driven plate of any suitable known type is represented at 42 and may be conected for example, by a known axially splined connection with a shaft, for example an input shaft to a gearbox.

The axial position of the stop tips 34 can be varied along directions A or B to take up manufacturing tolerances and/or vary, as desired, how far in direction A the clutch pressure plate can move.

Axial face 44 on the pressure plate 12 may be used as an abutment for controlling how far in direction B the pressure plate can be retracted into the cover 4 before the pressure plate may contact the tab(s) 28B.

Claims

1. A clutch cover assembly of the type referred to further comprising at least one of said tabs being arranged as a stop, and the pressure plate being provided with abutment means thereon to engage said stop to prevent travel of the pressure plate beyond a desired pre-determined position in said first direction.

2. A clutch cover assembly as claimed in Claim 1, in which the or each tab being arranged as a said stop extends, with respect to said axis, radially outwardly beyond other said tabs.

3. A clutch cover assembly as claimed in Claim 1 or Claim 2, in which said abutment means is provided by substantially radially inwardly facing- lip means on the pressure plate.

4. A clutch cover assembly as claimed in Claim 1 or Claim 2, in which the abutment means is provided by a wall of a recess in the pressure plate.

5. A clutch cover assembly as claimed in any one preceding claim, in which said tabs are used to retain at least one annular fulcrum arrangment for the diaphragm spring.

6. A clutch cover assembly substantially as herein before described with reference to Figs. 1 and 2 or Figs. 1 and 3 of the accompanying drawings.

7. A clutch comprising a clutch cover assembly as claimed in Claim 6.

8. A motor vehicle provided with a clutch as claimed in Claim 7.