GB2191829A

GB2191829A - Clutch cover assembly with pressure plate retainer

Info

Publication number: GB2191829A
Application number: GB08614815A
Authority: GB
Inventors: Gianfranco Piazzon
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1986-06-18
Filing date: 1986-06-18
Publication date: 1987-12-23
Also published as: GB8614815D0

Abstract

A clutch cover assembly comprises a cover (4), pressure plate (22) and diaphragm spring in which the pressure plate (22) is held rotationally fast with the cover (4) by drive straps which allow axial movement of the pressure plate (22) relative to the cover (4). Securing means (31) each hold respective drive straps (14) to the cover (4) and also secure in place a pressure plate retainer which by means of a catch (33) limits axial movement of the pressure plate (22). <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, rotation ally 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 accidently 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.

The present invention provides a means of limiting the axial movement of the pressure plate relative to the cover. Accordingly there is provided a clutch cover assembly comprising a clutch cover, a pressure plate and spring means acting between the pressure plate and the cover to bias the pressure plate away from the cover, the pressure plate being held rotationally fast with the cover by circumferentially spaced drive straps which allow the pressure plate to move axially of the cover, securing means each holding a respective drive strap to the cover, said securing means also each holding a pressure plate retainer in place on the cover and which limits the movement of the pressure plate away from the cover.

The pressure plate retainers can be formed as extensions of the portions of the drive straps adjacent the securing means, or alternatively can be formed on axially extending clips, which are preferably engageable with the outer peripheral margin of the pressure plate.

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 plan view of friction clutch cover assembly according to this invention, Figure 2 is a section through the cover assembly of Figure 1 on the line Il-Il, Figure 3 is an enlarged view of the cover assembly in the area of the drive straps as seen in the direction of arrow A in Figure 2, Figure 4 is a diagrammatic view partly in section of the pressure plate retainer as seen in the direction of B of Figure 3 with the cover absent, and Figure 5 is a radial cross-section through a portion of the cover assembly showing a pressure plate retainer.

With reference to Figures 1 and 2 there is illustrated a 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 away from the cover 4.

The cover 4 comprises a cylindrical sidewall 5 having a radially outwardly projecting flange 7 at one axial end thereof and a radially inwardly projecting flange 8 at the other axial end. The outwardly projecting flange 7 has a plurality of holes 6 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 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 acts 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 29 (Figs 3 and 5) 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 and serve as release straps to pull the pressure plate towards the cover when the clutch is released by load L. Each drive strap can be in the form of a plurality of superposed thin leaf springs which are bundled together to form the drive strap. The drive straps 14 are secured to the cover 4 and the lug 23 by suitable means 31, for example, rivets, bolts, etc.

With reference to Figs 3 to 5, the rivets 31 utilised for securing the drive straps 14 to the cover 4 are also utilised for' securing a pressure plate retainer 32 in position, one retainer 32 being associated with each of the drive straps 14. The three retainers 32 limit axial movement of the pressure plate towards the open end of the cover 4. The retainers 32 may be formed as an extension of the portions of at least one of the straps 14 adjacent the securing means 31 to the cover 4, which are bent to be engageable with the outer periphery of the pressure plate. Alternatively the retainers 32 can be formed on separate clips which are each secured to the cover 4 by the rivet 31 which passes through the clip and the set of straps 14. Each clip 32 extends axially relative to the cover and has a catch 33 at its axial end away from the cover which is engageable with the outer peripheral margin 34 of the friction surface 29. The catch 33 is designed so that there is a small radial clearance between the catch 33 and the outer periphery 35 of the driven plate D.

Each clip 32 also has a lug 36 at its end adjacent the cover 4 which engages with the cover to prevent rotation of the clip, and thereby prevents possible tipping of the pressure plate caused by the pressure plate coming into uneven engagement with the clips spaced around its periphery.

Whilst the invention has been described with reference to a clutch cover assembly of the diaphragm spring type, it should not be taken as being limited to this type of clutch cover assembly.

Claims

1. A clutch cover assembly comprising a clutch cover, a pressure plate and spring means acting between the pressure plate and the cover to bias the pressure plate away from the cover, the pressure plate being held rotationally fast with the cover by circumferentially spaced drive straps which allow the pressure plate to move axially of the cover, securing means each holding a respective drive strap to the cover, said securing means also each holding a pressure plate retainer in place on the cover and which limits the movement of the pressure plate away from the cover.

2. A clutch cover assembly as claimed in Claim 1 wherein the pressure plate retainers are formed as extensions of the portions of the drive straps adjacent the securing means.

3. A clutch cover assembly as claimed in Claim 1, wherein the pressure plate retainers are each formed as an axially extending clip having a catch at its end away from the cover and which forms an abutment for the pressure plate.

4. A clutch cover assembly as claimed in Claim 1, wherein the retainers are arranged to engage the outer peripheral margin of the pressure plate.

5. A clutch cover assembly as claimed in Claim 3 wherein the catches engage the friction surface of the pressure plate, radially outwardly of the outer periphery of a driven plate engageable therewith.

6. A clutch cover assembly as claimed in any one of Claims 3 to 5, wherein each clip has a lug thereon for engagement with the cover to prevent rotation of the clip relative to the cover.

7. A clutch cover assembly as claimed in any one of Claims 1 to 6 wherein the circumferentially spaced drive straps are formed as circumferentially spaced sets of thin straps having at least three straps per set, and each securing means retaining each respective set of straps to the cover is a rivet which passes through each strap in a respective set, and also through the respective pressure plate retainer.

8. A clutch cover assembly substantially as described herein and as illustrated in the accompanying drawings.