GB2198491A

GB2198491A - Friction clutches

Info

Publication number: GB2198491A
Application number: GB08706731A
Authority: GB
Inventors: Maurizio Buschi; Luigi Bambini
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-11-26
Filing date: 1987-03-20
Publication date: 1988-06-15
Anticipated expiration: 2007-03-20
Also published as: IT8622461A0; GB2198491B; IT1198168B; GB8706731D0

Abstract

A pressure plate assembly for a friction clutch has a cover member (10) with an inwardly directed lip (12) which provides an abutment for a fulcrum ring (21), fulcrum ring (21) engaging a diaphragm spring (18) about its outer periphery. Means in the form of a series of formations (23) are provided around the lip (12) of the cover member (10), to retain the fulcrum ring (21) in position with respect to the cover member (10). <IMAGE>

Description

FRICTION CLUTCHES The invention relates to friction clutches and in particular to friction clutches with a diaphragm spring clutch release mechanism.

A typical diaphragm spring clutch comprises a cover member, a. pressure plate mounted with respect to the cover member and a diaphragm spring interposed between the cover member and pressure plate. In use, the clutch is mounted on a flywheel and a driven plate is interposed between the flywheel and pressure plate. The diaphragm spring urges the pressure plate into frictional engagement with the flywheel. The diaphragm spring typically incorporates an outer annular plate spring or Belleville portion which engages the pressure plate and fingers projecting inwardly from the Belleville portion. The inner edges of the fingers are deflected, by means of pressure applied in the direction of the flywheel, to deform the Belleville portion and thus release the clutch.In order to achieve this, the diaphragm spring is pivotted between a pair of fulcrum rings, positioned one on either side of the spring adjacent the roots of the fingers, that is inside the ring of contact between the diaphragm spring and the pressure plate. The fulcrum rings are mounted in position relative to the cover member by means of rivets or tabs formed by the cover member, which pass through apertures between the fingers of the diaphragm spring. This places certain restrictions on the shape of the fingers and hence their resilience, which will effect the amount of travel required to release the clutch and the wfeelW of the clutch.

By pivotting the diaphragm spring outside the ring of contact between the spring and pressure plate and applying pressure to the fingers in a direction away from the flywheel in order to release the clutch, it is possible to simplify the pressure plate assembly, thereby removing the restraints on the shape of the fingers of the diaphragm spring. Furthermore, because of the loading of the diaphragm spring, the release pressure required to disengage the clutch will also be reduced.

According to one aspect of the present invention, a pressure plate assembly for a friction clutch comprises; a cover member of generally cylindrical configuration having at one end an outwardly directed flange adapted to be mounted on a flywheel and at the other end an inwardly directed lip, a pressure plate mounted coaxially with respect to the cover member, with circumferential drive means disposed therebetween, said drive means permitting axial movement of the pressure plate relative to the cover member; a diaphragm spring interposed between the lip of the cover member and the pressure plate, said diaphragm spring having an outer Belleville portion which engages the pressure plate and fingers projecting inwardly from the Belleville portion; and a fulcrum ring being positioned adjacent the outer periphery of the Belleville portion, between the diaphragm spring and the lip of the cover member, so that the diaphragm spring will urge the pressure plate axially away from the cover member and when pressure is applied to the fingers of the diaphragm spring in an axial direction away from the pressure plate, the pressure plate will tend to move axially towards the cover member, means being provided to retain the fulcrum ring in position on the lip of the cover member.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a plan view of a pressure plate assembly for a friction clutch, in accordance with the present invention; and Figure 2 shows a section along the line II-II in Figure 1.

As illustrated in Figures 1 and 2, a pressure plate assembly comprises; a cover member 10 of generally cylindrical configuration having an outwardly directed flange 11 at one end, by means of which the pressure plate assembly may be secured to a flywheel (not shown). The cover member 10 has an inwardly directed lip 12 at the end remote from the flange 11.

A pressure plate 13 is mounted coaxially within the cover member 10 by meons of three drive straps 15 which are attached at one end to lugs 14 on the pressure plate 13 by rivets 16 and at the other end to flange 11 of the pressure plate 1Q by rivets 17. The straps 15 are flexible so that they permit a limited amount of axial movement of the pressure plate 13 relative to the cover member 10, while locating the pressure plate 13 coaxially with respect to the cover member 10 and providing a circumferential drive connection.

A diaphragm spring 18 having an outer Belleville portion 19 and inwardly directed fingers 20, is located between the lip 12 of the cover member 10 and of annular projection 24 on the pressure plate 13. The outer periphery of the Belleville portion 19 engages a fulcrum ring 21 which is located against the opposed face of lip 12. Three radially extending tabs 22 are provided at circumferentially spaced locations about the lip 12 and these have projections 23 directed towards the pressure plate 13, so that the fulcrum ring 21 may be mounted outside these projections 23 for accurate centering. The projection 23 may be provided by stamping or any other suitable means.

The diaphragm spring 18 is thereby arranged to act between the fulcrum ring 21 and annular projection 24 on the pressure plate 13, to urge the pressure plate 13 axially away from the cover member 10. Thus, when the cover member 10 is mounted upon a flywheel (not shown) with a driven plate (not shown) interposed between the flywheel and the pressure plate 13, the driven plate will be clamped between the flywheel and pressure plate 13, under the load applied to the pressure plate 13 by the diaphragm spring 18, so that the clutch will be in the engaged condition.

Release of the clutch may be achieved by applying pressure to the inner ends of the fingers 20 of the diaphragm spring 18, in the direction indicated by Arrows A. This will cause the Belleville portion 19 of the spring 18 to tend to move away from the pressure plate 13, thereby reducing the clamping pressure on the driven plate. Pressure may be applied to the fingers 12 by means of a suitable release mechanism (not shown).

Various modifications may be made without departing from the invention. For example, any number of projections that will give adequate location of the fulcrum ring 21 may be used. Furthermore, formations other than projections 23 may be used to locate the fulcrum ring 21. For example circumferentially spaced tabs on the lip 12 may be folded over to provide such locating formations.

Claims

1. A pressure plate assembly for a friction clutch comprising; a cover member of generally cylindrical configuration having at one end an outwardly directed flange adapted to be mounted on a flywheel and at the other end an inwardly directed lip, a pressure plate mounted coaxially with respect to the cover member, with circumferential drive means disposed therebetween, said drive means permitting axial movement of the pressure plate relative to the cover member; a diaphragm spring interposed between the lip of the cover member and the pressure plate, said diaphragm spring having an outer Belleville portion which engages the pressure plate and fingers projecting inwardly from the Belleville portion; and a fulcrum ring being positioned adjacent the outer periphery of the Belleville portion, between the diaphragm spring and the lip of the cover member, so that the diaphragm spring will urge the pressure plate axially away from the cover member and when pressure is applied to the fingers of the diaphragm spring in an axial direction away from the pressure plate, the pressure plate will tend to move axially towards the cover member, means being provided to retain the fulcrum ring in position on the lip of the cover member.

2. A pressure plate assembly according to claim 1 in which said means for locating the fulcrum ring comprises one or more formations on the lip of the cover member.

3. A pressure plate assembly according to claim 2 in which said means for locating the fulcrum ring comprises a plurality of circumferentially spaced formations on the lip of the cover member.

4. A pressure plate asssembly according to claim 3 in which said means for locating the fulcrum ring comprises a plurality of circumferentially spaced tabs with projections extending therefrom towards the pressure plate.

5. A friction clutch including a pressure plate assembly as claimed in any one of claims 1 to 4.

Claims 2 to 5 above have been superceded by the following blaims:- 2. A pressure plate assembly according to claim 1 in which said means for locating the fulcrum ring comprises one or more formations on the lip of the cover member.

5. A pressure plate assembly substantially as described herein with reference to, and as shown in, figures 1 and 2 of the accompanying drawings.

6. A friction clutch including a pressure plate assembly as claimed in any one of claims 1 to 5.