GB2191828A - Friction clutch cover assembly - Google Patents

Abstract

A friction clutch cover assembly (2), Fig. 2, having a cover (4), a pressure plate (22), a diaphragm spring (16), and an annular fulcrum ring (50), Fig. 5, located between the spring (16) and the pressure plate (22) and/or/the cover (4). The fulcrum ring (50) is supported on circumferentially spaced lands (34) so that portions of the ring (50) spanning respective spaces (35) between adjacent lands (34) are resiliently axially deformable into the spaces (35) when loaded by the spring (16). Said portions spanning the spaces (35) have projections (52) thereon which provide an abutment for the outer annulus (17) of the spring (16), the projections (52) being integrally formed with the ring material. <IMAGE>

Description

SPECIFICATION Friction clutch cover assemblies This invention relates to friction clutch cover assemblies, and in particular, though not exclusively, 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 is in turn mounted on the flywheel. The pressure plate is rotationally fast with the cover and the flywheel and is biased away from the cover by spring(s) to trap the driven plate between itself and the flywheel. Drive straps holding the pressure plate rotationally fast with the cover 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.

During the clamping of a driven plate between the flywheel and pressure plate, i.e. when the vehicle clutch is engaged, it is desirable for there to be some axial resilience in the friction clutch during the engagement of the friction surfaces of the driven plate with like surfaces on the pressure plate and flywheel.

In prior art clutches the axial resilience is achieved by having cushioning elements within the driven plate, or alternatively by having cushioning elements within the pressure plate, or even by using a resilient fulcrum ring between the diaphragm spring and the clutch cover. In pending British Application 8602243 there is described a friction clutch having a resilient fulcrum means between the diaphragm spring and either the cover, or the pressure plate. The present invention seeks to provide an improved fulcrum means of the type described in the above application.

Accordingly there is provided a friction clutch cover assembly comprising a pressure plate, a coaxial cover, and a coaxial diaphragm spring located between the cover and the pressure plate and for loading the pressure plate, and a coaxial annular fulcrum means acting between the diaphragm spring and at least one of the cover and the pressure plate, said fulcrum means including a resilient fulcrum ring supported on circumferentially spaced supports, portions of the resilient ring each spanning a respective space between adjacent supports so that said portions are resiliently axially deformable into their respective spaces when loaded by the diaphragm spring and wherein said portions of the resilient ring spanning said spaces have projections thereon extending towards the diaphragm spring to provide an abutment therewith, the projections being formed integrally with the material of the resilient ring.

Preferably the projections are spherical bulges or circular flats on the ring, which are formed on the ring by deformation of the ring material out its regular radially circular crosssection.

Conveniently the resilient fulcrum ring acts between the pressure plate and the diaphragm spring, and is located in an annular groove on a raised annular rib on the pressure plate.

The invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a plan view of a clutch cover assembly according to this invention, Figure 2 is a section on the line ll-ll of Figure 1 and also showing the clutch cover assembly as fitted to a vehicle friction clutch, Figure 3 is a plan view of a pressure plate as used in the cover assembly of Figure 1 showing a resilient fulcrum ring in-situ, Figure 4 is a section on the line IV-IV of Figure 3 showing only the pressure plate, Figure 5 is a section on the line V-V in Figure 3 plus the diaphragm spring, Figure 6 is a detailed radial section through a cover assembly according to this invention, Figure 7 is a view of a resilient fulcrum ring as used in the cover assembly of Figure 1, Figure 8 is an enlarged view of a spherical projection taken in the direction of arrow X of Figure 7, Figure 9 is a view of a second resilient fulcrum ring as used in the cover assembly of Figure 1, Figures 10, 11 and 12 are views of the ring taken in the directions of arrows X', Y and Z of Figures 9 and 10, and Figures 13A,B,C and D illustrate the deformation of the resilient fulcrum ring during engagement of a clutch.

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 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 a 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 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 is made rotationally fast with the cover 4 by three sets of 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.

The pressure plate 22 is shown in more detail in Figures 3 and 4, and comprises an annular cast-iron body 30 having on one axial side a friction surface 31 for engagement with the driven plate, and on its other axial side a raised annular rib 33 extending axially away from the friction surface 31. The annular rib 33 comprises a number of circumferentially spaced lands 34 separated by spaces 35. The lands 34 provide supports for a resilient fulcrum ring 50 which locates in an annular array of arcuate grooves 36 in the top of the lands 34. The resilient fulcrum ring 50 provides for the axial cushioning in the clutch during the reengagement of the clutch.

It is preferable for the lands 34A to have the same circumferential length LA, except in the case where the resilient fulcrum ring 50 is a split ring. In this case, as shown in Figure 3, the ends 51 of the split ring are flattened and are engaged in a space 35B located between two lands 34B. The two lands 34B are spaced apart to accommodate the ends 51 of the ring 50 and any movement of the ends caused during deformation of the ring 50.

It is preferable for the spaces 35 between adjacent lands 34 to all have the same circumferential length LC, that is excepting the space 35B.

The resilient fulcrum ring 50 is shown in detail in Figure 7 and Figure 8. The spring steel ring 50 has a pair of flat ends 51 (see Figure 11) which locate in the space 35B between the land 34B. There are a plurality of circumferentially spaced projections 52 on the ring, in the form of spherical bulges made out of the ring material itself. These bulges 52 are positioned so that when the ring 50 is located in the groove 36 each bulge 52 is located at the mid-point of the circumferential length LC of the respective space 35 in which it is located. Each spherical bulge, preferably, has the same diameter D.

When the pressure plate 22, and ring 50, are assembled into the clutch cover assembly 2, as shown in Figures 5 and 6 the ring 50 is supported in the annular array of grooves 36 on the lands 34. The bulges 52 provide a series of circumferentially spaced abutments against the annular outer portion 17 of the diaphragm spring 16. The circumferential end portions 38 of the groove 36 in each land 34 may be radiused as shown at 38 in Figure 13 so as to reduce fretting of the ring 50 on the supports 34.

With reference to Figures 13A,B, C and D, there is schematically illustrated the sequence of events during clutch re-engagement. Figure 13A shows the annular supports 34 of the pressure plate, with the groove 36 in the top of the supports and the spaces 35 between the supports. Figure 13B shows the resilient ring 50 in place in the grooves 36 with the spherical bulges 52 located at the mid-length position of each respective space 35. The outer annular portion 17 of the spring 16 is just in contact with the bulges 52 as the pressure plate 22 contacts the driven plate, during re-engagement of the clutch.As shown in Figure 13C, when the load applied by the spring 16 to the pressure plate increases the resilient ring 50 is deformed so that the portions of the ring spanning the spaces 35 between the supporting lands 34 are pushed axially inte the spaces 35, and at the same time the portions of the ring 50 located over the supports 34 bow away from the surface of the support. During the final phase of re-engagement the bowed portions of the ring are flattened into the grooves 36 as the spring 16 finally abuts the supports 34.

The axial deformation of the ring 50 provides the cushioning effect on re-engagement of the clutch. The reistance of the resilient ring 50 to deformation in the first stage of reengagement (13C) is different, to the resistance of the ring to deformation in the later stages of re-engagement (13D) and therefore a two stage axial cushioning effect is achieved.

In Figures 9-12 there is illustrated an alternative resilient fulcrum ring 150. The ring 150 is a split ring having flattened ends 151 (Figure 11). The projections 152 are formed by pinched circular flats on sides of the ring, shown from the radial direction in Figure 10 and from a plan view in Figure 11. Preferably the pinched circular flats 152 all have the same diameter D.

Whilst the present invention has been described with reference to the accommpanying drawings, it is possible to make minor alterations without departing from the spirit and scope of the invention. For example, the reilient fulcrum ring 50, 150 could be a continuous ring instead of a split ring. Furthermore, multi-stage resilient cushioning could be achieved by having spherical bulges of differing diameters instead of all being the same diameter, also the spaces 35 between adjacent supports 34 could be of differing circumferential lengths.

If desired the fulcrum ring 24 (Figure 2) could be replaced by a said fulcrum ring 50 or 150 as described suitably supported by spaced supporting means on the cover; or a said fulcrum ring 50 or 150 could be interposed between an outer peripheral margin of the diaphragm spring and spaced supporting means on the cover in a clutch cover assembly for a pull-type clutch.

Claims (16)

1. A friction clutch cover assembly comprising a pressure plate, a coaxial cover, and a coaxial diaphragm spring located between the cover and the pressure plate and for loading the pressure plate, and a coaxial annular fulcrum means acting between the diaphragm spring and at least one of the cover and the pressure plate, said fulcrum means including a resilient fulcrum ring supported on circumferentially spaced supports. portions of the resilient ring each spanning a respective space between adjacent supports so that said portions are resiliently axially deformable into their respective spaces when loaded by the diaphragm spring and wherein said portions of the resilient ring spanning said spaces have projections thereon extending towards the diaphragm spring to provide an abutment therewith, the projections being formed integrally with the material of the resilient ring.

2. A clutch cover assembly as claimed in Claim 1 wherein the projections on the ring are formed by deformation of the ring.

3. A clutch cover assembly as claimed in Claim 3 wherein the projections are formed as spherical bulges of the ring material.

4. A clutch cover assembly as claimed in Claim 3 wherein the projections are formed as circular flats on the ring.

5. A cover assembly as claimed in Claim 3 or Claim 4 wherein all the spherical bulges or circular flats have the same diameter. j

6. A cover assembly as claimed in any one of Claims 1-5 wherein the fulcrum ring is a split ring.

7. A cover assembly as claimed in any one of Claims 1 to 6 wherein each space into which the ring is deformable has the same circumferential length.

8. A cover assembly as claimed in Claim 7 wherein the projections on the resilient ring are located at the mid-length position of each respective space in which, they are located.

9. A cover assembly as claimed in any one of Claims 1 to 8 wherein the fulcrum means having the axial cushioning are fulcrum means acting between the diaphragm spring and the pressure plate, and the supports are formed on an interrupted raised annular rib on the pressure plate.

10. A cover assembly as claimed in any one of the proceeding claims wherein other portions of said resiliently deformable ring are deformable to bow away from the support on which they rest, and are thereafter compressable against the supports by action of the diaphragm spring.

11. A cover assembly as claimed in any one of the preceeding claims wherein the supports are constituted by lands extending between the spaces into which the resilient ring projects.

12. A clutch cover assembly as claimed in Claim 11 wherein each land has a groove in which the ring is engaged.

13. A clutch cover assembly as claimed in Calims 10, 11 or 12 wherein each circumferential end portion of each support is radiused.

14. A spring diaphragm clutch cover assembly substantially as hereinbefore described with reference to Figures 1 to 6 with Figures 7 and 8 or Figures 9 to 12 of the accompanying drawings.

15. A clutch comprising a diaphragm spring clutch cover assembly as claimed in any one preceding claim.

16. A motor vehicle having a clutch as claimed in Claim 15.