GB2191832A

GB2191832A - Friction clutch cover assembly

Info

Publication number: GB2191832A
Application number: GB08713546A
Authority: GB
Inventors: Anthony John Curtis
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-06-18
Filing date: 1987-06-10
Publication date: 1987-12-23
Anticipated expiration: 2007-06-10
Also published as: GB8614814D0; GB8713546D0; GB2191832B

Abstract

A motor vehicle friction clutch cover assembly (2) comprises a clutch cover (4) with a sidewall (5) and a radially outwardly projecting flange (7) at its open end for mounting the cover to a flywheel, a pressure plate (22) mounted within the cover for axial movement, and a diaphragm spring (16) urging the pressure plate (22) towards the open end of the cover (4). The axial movement of the pressure plate is limited by a retention means (31) located at the periphery of the cover. The retention means (31) comprises at least one radial key (32) secured on the flange (7) on its axial side away from the flywheel and extending through the sidewall (5) to provide an abutment for the pressure plate (22). Each key (32) is held to the flange (7) by a cross strap (35). <IMAGE>

Description

SPECIFICATION Friction clutch cover assemblies This invention relates to friction clutch cover assemblies, for example to clutch cover assemblies for motor vehicles. In a typical motor vehicle friction clutch, a driven plate, rotationally fast with the input shaft of a gearbox, is sandwiched between a flywheel on the engine crankshaft and a pressure plate. The pressure plate is usually mounted in a clutch cover assembly, and the cover assembly is in turn mounted on the flywheel. The pressure plate is rotationally fast with a cover and the flywheel, and is biased away from the cover by urging spring means to trap the driven plate between itself and the flywheel. Drive straps hold the pressure plate rotationally fast with the cover and allow the pressure plate to move axially so as to enable the driven plate to be released or clamped between the flywheel and pressure plate as required.The drive straps are formed by leaf springs serving as release springs to pull the pressure plate towards the cover when the biasing load applied to the pressure plate by said urging spring means is relieved.

Prior to mounting such a clutch cover assembly on a vehicle flywheel, or alternatively during vehicle maintenance when the clutch cover assembly is removed from the vehicle flywheel, the pressure plate is moved by the urging spring means, typically a diaphragm spring, axially away from the cover. Also the heavy pressure plate may suddenly axially move further from the cover under the inertia of the pressure plate when a floor abruptly halts the falling cover, should the cover be accidentally dropped.

If axial movements of the pressure plate are extreme and limited by the drive straps the latter become overstressed causing them damage which impedes their ability to retract the pressure plate when the clutch is released in use, and thus clutch drag occurs.

Accordingly there is provided a clutch cover assembly for a friction clutch comprising an annular clutch cover having a sidewall with a radially outwardly projecting flange at the open end of the cover, a pressure plate, spring means acting between the pressure plate and the cover to bias the pressure plate towards the open end of the cover, and pressure plate retention means to limit movement of the pressure plate towards the open end thereof, said pressure plate retention means comprising at least one key which is secured to the outwardly projecting flange on the axial side thereof away from the open end and which extends radially inwardly through the sidewall of the cover so that its radially inner end portion is engageable with the pressure plate, wherein each key is held to the flange by a cross-strap passing over the key.

A further advantage of limiting the axial movement of the pressure plate is that it can prevent damage to the pressure plate caused by excess wear in the driven plate. The invention will be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a cross-section of a typical friction clutch cover assembly showing the assembly mounted in a vehicle friction clutch, Figure 2 is a fragmentary plan view of a modification of the clutch cover assembly in Figure 1, the modification forming an embodiment of a friction clutch cover assembly formed according to the invention, Figure 3 is a section on the line Ill-Ill of Figure 2, and Figure 4 is a view of the pressure plate retainer as seen in the direction of Arrow A in Figure 2.

In the drawings the same reference numerals refer to like or comparable parts.

Figure 1 illustrates a typical motor vehicle friction clutch cover assembly 2, comprising an annular cover 4, a pressure plate 22 located coaxially within the cover 4, and a coaxial diaphragm spring 16 located between the cover and the pressure plate to bias the pressure plate 22 towards the open end of the cover 4.

The cover 4 comprises a cylindrical sidewall 5 having a radially outwardly projecting flange 7 at its open end and a radially inwardly projecting flange 8 at the other axial end. The outwardly projecting flange 7 has a plurality of holes 6 (Fig 2) therein whereby the cover is attached by bolts B to flywheel F on the crankshaft of a vehicle engine. The inwardly projecting flange 8 has a plurality of tabs 26 on its radially inner periphery whereby the diaphragm spring 16 is attached to the cover.

The spring 16 is a frustoconical plate spring coned away from the pressure plate 22 and having a radially outer continuous annular portion 17 with a plurality of spaced radially inwardly extending fingers 18 projecting from the radially inner periphery of the annular portion 17. The spring 16 is attached to the cover 4 by the tabs 26 on the cover, extending through respective apertures 19 (fig 2) at the base of the fingers 18 and being bent around the continuous portion 17 of the spring to clinch the spring to the cover. A pair of coaxial fulcrum rings 24 and 28 are located one on each side of the diaphragm spring and are located against the radially outer surface of the tabs 26 prior to the tabs being bent around the spring 16. The outer margin 17 of the spring 16 act against the pressure plate 22.

When the cover assembly is mounted on the flywheel F the pressure plate, 22 is biased by the spring 16 to clamp a driven plate D between itself and the flywheel F. The hub H of the driven plate D is fitted onto a gearbox input shaft I. To release the driven plate D, a release load L is applied to the radially inner ends of the spring fingers 18, via a clutch release bearing G, to move the inner ends of the fingers towards the flywheel F, causing the outer annular portion 17 of the spring to pivot about the fulcrum rings 24, 28 and move away from the flywheel F. When the clutch is re-engaged the reverse operation takes place.

The pressure plate 22 has an annular cast iron body with a friction surface 30 (Fig.3) on one axial side for engagement with the driven plate D and is made rotationally fast with the cover 4 by three circumferentially spaced drive straps 14 which extend between the cover and lugs 23 on the outer periphery of the plate 22. The drive straps 14 allow for axial movement of the pressure plate 22 relative to the cover 4 whilst holding the two rotationally fast.

An embodiment of a clutch cover assembly formed according to the invention will now be described with reference to Figures 2 to 4.

In order to limit the displacement of the pressure plate 22 towards the open end of the cover 4 there are provided pressure plate retention means 31 to engage the outer periphery of the pressure plate. There is at least one, but preferably three such retention means 31 located at substantially equiangularly spaced intervals around the cover 4.

Each retention means 31 comprises a key 32 which is secured to the outwardly projecting flange 7 on its axial side away from the open end. Each key 32 extends radially inwardly through an aperture 33 in the sidewall 5 of the cover so that its radially inner end portion is engageable with a lug 34 on the outer periphery of the pressure plate. Alternatively, the key 32 could abut against the friction surface 30 of the pressure plate at a position radially outwardly of the driven plate D with which it is engageable.

Each lug 34 is held on the flange 7 by a cross-strap 35 which passes over the key to hold it flat against the flange, so that the cross-strap prevents the key 32 from tipping when the pressure plate abuts its inner end.

Each cross-strap 35 is formed integrally with the flange 7 and is formed as a raised loop from a portion of the flange which is sheared along two substantially parallel lines and then pushed through the flange. The key 32 may be a tight push-fit between the cross-strap 35 and the flange 7 so that it will not come loose accidentally but can be removed radially outwardly if desired. To this end, each key 32 has a flange 36 at its outer end to facilitate fitting and removal from the respective strap 35. The flange 36 will also act as a stop to limit the radially inward insertion of the respective key so that it will not interfere with the driven plate.

Alternatively each key 32 can be held permanently in position by deforming the key 32 and/or the strap 35, and/or an adjacent portion of the cover to retain the respective key in position.

Claims

1. A clutch cover assembly for a friction clutch comprising an annular clutch cover having a sidewall with a radially outwardly projecting flange at the open end of the cover, a pressure plate, spring means acting between the pressure plate and the cover to bias the pressure plate towards the open end of the cover, and pressure plate retention means to limit movement of the pressure plate towards the open end thereof, said pressure plate retention means comprising at least one key which is secured to the outwardly projecting flange on the axial side thereof away from the open end and which extends radially inwardly through the sidewall of the cover so that its radially inner end portion is engageable with the pressure plate, wherein said key is held to the flange by a cross-strap passing over the key.

2. A cover assembly as claimed in Claim 1 wherein the cross-strap is formed integrally with the flange.

3. A cover assembly as claimed in Claim 2 wherein the cross-strap is a raised loop formed from a portion of the flange which is sheared along two lines laterally spaced one from the other and deformed to make a raised loop.

4. A cover assembly as claimed in any one of claims 1 to 3 wherein the or each key of the pressure plate retainer means can be withdrawn radially from the respective cross-strap to release the pressure plate.

5. A cover assembly as claimed in any one of Claims 1 to 3 wherein the or each key of the pressure plate retainer means is held permanently in position by deformation of the key and/or the cross-strap and/or the cover.

6. A cover assembly as claimed in any one of Claims 1 to 5 wherein the or each key has a flange at its outer end which limits the radial inward movement of the key on assembly.

7. A clutch cover assembly as claimed in any one of the preceding claims in which the pressure plate retention means comprises at least three said keys substantially equiangularly spaced apart around the circumference of the cover.

8. A clutch cover assembly for a vehicle friction clutch and which is substantially as described herein and with reference to Figures 2 to 4 of the accompanying drawings.

9. A clutch comprising a clutch cover assembly as claimed in any one preceding claim.