GB2144496A

GB2144496A - A diaphragm spring friction clutch

Info

Publication number: GB2144496A
Application number: GB08320846A
Authority: GB
Inventors: Richard David Maitland Cooke
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1983-08-02
Filing date: 1983-08-02
Publication date: 1985-03-06
Also published as: GB2144496B; GB8320846D0

Abstract

In a diaphragm spring friction clutch cover assembly the outer periphery of the diaphragm spring (24) bears against an annular fulcrum ring (22) of a reaction member (21), and a series of short levers (28) bear at their inner ends against castellations (29) on the pressure plate and at their outer ends against the belville portion of spring (23). Between their ends, the levers (28) bear against a fulcrum ring (31) carried by the cover pressing (11). The diaphragm spring (23) urges the outer end of levers (28) away from the pressure plate so that the levers pivot about fulcrum (31) and urge the pressure plate towards the flywheel. To release the clutch, a release load is applied to the inner ends of fingers (25) so that the diaphragm spring no longer presses on the outer ends of levers (28) and the inner ends of the levers no longer press on the pressure plate. <IMAGE>

Description

SPECIFICATION Friction clutch cover assemblies The invention relates to friction clutch cover assemblies. One popular form of friction clutch cover assembly is the diaphragm spring type. A typical diaphragm spring clutch incorporates a cover arranged to be rotatable with an engine flywheel, an annular pressure plate movable axially with respect to the cover and constrained to rotate therewith and a diaphragm spring acting between the cover and the pressure plate to urge the pressure plate towards the flywheel and clamp a driven plate therebetween. The diaphragm spring incorporates an outer belville portion and integral inwardly directed fingers. Near the roots of the fingers the spring is pivotally mounted to the cover about an annular fulcrum line and at the outer periphery of the spring it bears against the cover.To release the clutch by removing the load of the diaphragm spring from the pressure plate, the inner ends of the fingers are pushed by a release mechanism towards the engine flywheel to pivot the spring about its fulcrum line.

One disadvantage of a conventional diaphragm spring clutch is that as the clutch is being disengaged the direction of the reaction at the fulcrum line changes from acting on the cover away from the flywheel while the clutch is in an engaged state to an opposite direction when it is in a disengaged state. There is a tendency for free play to be built into a clutch at the fulcrum line or to develop during use of the clutch. A clutch operating lever (normally a pedal) thus requires a long stroke to take up this free play. For larger clutches needed to transmit high torques the pedal travel becomes unacceptably long or if the lever ratio is adjusted to compensate for the long stroke the clutch release load at the pedal becomes unacceptably high.

It has already been proposed to modify a diaphragm spring clutch so that the pressure plate is supported adjacent its outer periphery by the cover and bears by a fulcrum line adjacent the roots of the fingers against the pressure plate. Then, to release the clutch, the diaphragm spring fingers have to be pulled in a direction away from the cover. This kind of clutch, known as a pull-type clutch overcomes the disadvantage of having free play at the fulcrum because no load reversal takes place but a pull-type release mechanism creates problems of its own.

An object of the present invention is to provide a diaphragm spring friction clutch cover assembly which is of the push-type but does not suffer from load reversals at a fulcrum during operation.

According to the present invention there is provided a friction clutch cover assembly comprising a cover arranged to be rotatable with an engine flywheel, an annular pressure plate movable axially with respect to the cover and constrained to rotate therewith, a diaphragm spring acting between the cover and the pressure plate to in use urge the pressure plate towards the flywheel to clamp a driven plate therebetween, wherein the diaphragm spring is supported adjacent its outer periphery against movement towards the pressure plate and wherein the load from the diaphragm spring is transmitted to the pressure plate by a series of levers each bearing against the diaphragm spring and the pressure plate and being supported by the cover between the bearing point with the diaphragm spring and the pressure plate.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an end view of a major part of a friction clutch cover assembly according to the invention; Figure 2 is a section on line ll-ll of Fig. 1; Figure 3 is a section on line Ill-Ill of Fig. 1; Figure 4 is a section on line IV-IV of Fig. 1; and Figure 5 is a section corresponding generally to the upper part of Fig. 2, showing a modification.

The clutch cover assembly shown in Figs. 1 to 4 incorporates an annular pressing 11 having an external flange 1 2 by means of which it can be mounted to an engine flywheel shown diagrammaticaly at 1 3 in Fig.

2. An annular pressure plate 14 is mounted generally within the cover 11 and is arranged to be rotated about the clutch axis 10 with the cover by means of three flexible drive straps 1 5 rivetted to the cover at 1 6 and to lugs 1 7 of the pressure plate at 18. A clutch driven plate 19, shown diagrammatically in Fig. 2, is interposed between the pressure 14 and flywheel 1 3.

An annular reaction member 21 forms part of the cover 11 by being rivetted to the main cover pressing at 20 as best seen in Fig. 3.

Reaction member 21 provides an outer annular reaction ring 22. A diaphragm spring 23 incorporates an outer belville portion 24 and inwardly directed diaphragm spring fingers 25. The fingers are separated along their lengths by slots 26 which at the roots of the fingers open into apertures 27. The diaphragm spring 24 is supported adjacent its outer periphery against movement towards the pressure plate by the reaction ring 22.

The diaphragm spring acts between cover 11 and pressure plate 14 through the intermediary of a series of levers 28. Fig. 1 shows that there are thirteen of these levers, one associated with each aperture 27. As shown in Fig. 2, each lever is generally C-shaped.

The inner end of each lever bears against a castellation 29 projecting from the pressure plate through a diaphragm spring aperture 23. The outer end of each lever bears against the belville portion 24 of the diaphragm spring at a position well spaced from the reaction ring 22. The central region of each lever also bears against a fulcrum ring 31 carried on the cover 11. For location of the diaphragm spring, three of the castellations, two of which are shown in Fig. 1 as 29A, are enlarged laterally so that they engage against the edges of apertures 27A. Levers 28 are located by grooves in the ends of the castellations 29 in the pressure plate. Fulcrum 31 is located by in-turned tabs 32 on the inner edge of the cover.

In its free state, the diaphragm spring is dished but with the clutch engaged it is held substantially flat by bearing against the reaction ring 22 and the outer end of each lever 28. The diaphragm spring thus applies a load in a direction away from the flywheel to the outer end of each lever and due to the generally central position of the fulcrum ring 31 on the levers, this load is transmitted through the levers to the pressure plate as a load to urge the pressure plate towards the flywheel. In order to release the clutch, a release load is applied in the direction of arrow 33 to the inner ends of the fingers 25. As the spring is deflected under this load, the load applied to the levers 28 by the spring is reduced and eventually a no-load condition is reached.As the load of the diaphragm spring on the levers reduces and is eliminated, the corresponding load applied to the pressure plate also diminishes and is eliminated. Straps 1 5 act as leaf springs to retract the pressure plate so the clutch becomes disengaged.

An advantage of this arrangement is that there are no load reversals at any point in the mechanism during clutch engagement and disengagement. This both facilitates the design of some of the pivots and tends to eliminate the lost-motion which would require high pedal loads or a long pedal travel. This is achieved with a push-type clutch as indicated by arrows 33 illustrating the direction of a release load. If desired, the characteristic of the clutch can be adjusted at the design stage by altering the lever ratio associated with levers 28. This makes it possible to provide a series of fundamentally similar clutches with differing characteristics whilst maintaining a large number of common components from one clutch to the next.

Fig. 5 is a view corresponding generally to the upper part of Fig. 2 but showing two significant modifications. Firstly, instead of locating the diaphragm spring by enlarged castellations 29A, the reaction member 34 is provided with elongated bent out tabs 35 which engage and locate on the outer periphery of the diaphragm spring 23. Also, the generally C-shaped levers 28, which although they are simple pressings require carefully rounded ends, are replaced by pressings with outwardly bent ends to provide suitable pivotbearing surfaces in a simple pressing without any subsequent machining.

In Fig. 5, the levers may be located by forming all thirteen levers integrally in a single pressing with the levers joined to each other by narrow webs. The webs should be sufficiently thin to allow the required pivotal movement of the levers. This arrangement also simplifies clutch assembly.

Claims

1. A friction clutch cover assembly comprising a cover arranged to be rotatable with an engine flywheel, an annular pressure plate movable axially with respect to the cover and constrained to rotate therewith, a diaphragm spring acting between the cover and the pressure plate to in use urge the pressure plate towards the flywheel to clamp a driven plate therebetween wherein the diaphragm spring is supported adjacent its outer periphery against movement towards the pressure plate and wherein the load from the diaphragm spring is transmitted to the pressure plate by a series of levers, each bearing against the diaphragm spring and the pressure plate and being supported by the cover between the bearing points with the diaphragm spring and the pressure plate.

2. A friction clutch cover assembly as claimed in claim 1 wherein the pressure plate has projections which extend through apertures at the roots of fingers of the diaphragm spring for engagement with the levers.

3. A friction clutch cover assembly as claimed in claim 2 wherein the diaphragm spring is located with respect to the pressure plate by some of the projections.

4. A friction clutch cover assembly as claimed in claim 1 or claim 2 wherein the support for the diaphragm spring adjacent its outer periphery is provided by a reaction member located with respect to the mounting of the cover and extending inside the cover.

5. A friction clutch cover assembly as claimed in claim 4 wherein the diaphragm spring is located by tabs projecting from the reaction member and engaging the outer edge of the diaphragm spring.

6. A friction clutch cover assembly as claimed in any one of the preceding claims wherein the cover carries a wire fulcrum ring which provides the bearing points for the levers on the cover.

7. A friction clutch cover assembly substantially as described with reference to and as illustrated by Figs. 1 to 4 of Figs. 1 to 4 as modified by Fig. 5 of the accompanying drawings.