GB2384034A

GB2384034A - Clutch friction element with stops to limit cushioning

Info

Publication number: GB2384034A
Application number: GB0127603A
Authority: GB
Inventors: Richard David Maitland Cooke
Original assignee: AP TMF Ltd
Current assignee: AP TMF Ltd
Priority date: 2001-11-17
Filing date: 2001-11-17
Publication date: 2003-07-16
Also published as: GB0127603D0

Abstract

A clutch annular friction element assembly having a friction material member (26) resiliently mounted (27) on a support plate (24) to allow movement of the friction member in a direction generally parallel to the axis of rotation of the assembly provide an axially cushioned engagement of the associated clutch when the assembly is clamped between a pressure plate (12) and a reaction member (11). Stop means (28) are provided to limit the axial cushioning movement of the friction material member (26) when the assembly is clamped between the pressure plate and the reaction member.

Description

CLUTCH FRICTION ELEMENT ASSEMBLIES This invention relates to clutch friction element assemblies and in particular to such assemblies which form part of a clutch driven plate.

Clutch friction element assemblies (hereinafter described as being of the type described) are well known in which the assembly is designed for rotation about a transmission shaft axis and to be clamped between a pressure plate and a reaction member (such as a flywheel) to engage an associated clutch and transmit drive between the reaction member and the transmission shaft, such assemblies include a friction material member resiliently mounted to allow movement of the friction member in a direction generally parallel to said axis of rotation to provide an axially cushioned engagement of the clutch when the assembly is clamped between the pressure plate and the reaction member.

Whilst friction element assemblies of the type described are reasonably successful in cushioning engagement of the associated clutch they present problems due to the unpredictable effect on the clutch clamp load of the resilient mounting and also provide problems in ensuring the correct orientation of the friction material member when the associated clutch is engaged which can lead to damage to the friction material member and erratic operation of the clutch.

It is an object of the present invention to provide an improved friction element assembly of the type described which at least mitigates the above difficulties.

Thus according to the present invention there is provided a friction element assembly of the type described characterised in that stop means are provided to limit the cushioning movement of the friction material when the assembly is clamped between the pressure plate and the reaction member.

With such an arrangement, after the initial cushioning movement of the friction material member as the assembly is clamped between the pressure plate and the reaction member, the

stop means engages so that the assembly becomes solid in an axial sense thus the full clamping pressure applied to the pressure plate can be realised and the assembly is correctly orientated in a generally parallel relationship between the pressure plate and the reaction member.

In one form of the invention the friction element assembly may comprise a support member and resilient mounting means for mounting the friction material member on the support member.

In such an arrangement the stop means may be on the friction material member or the support member or even on both members.

Typically the face of the friction material member which faces the support member will be provided with a plurality of axially extending projections which contact the support member after a predetermined amount of movement of the friction material member towards the support member as the clutch is engaged.

The support member and friction material member may be annular in form or one or both of these members may be of arcuate form with a number of such arcuate members positioned circumferentially adjacent to each other to form a complete annular friction element assembly.

The resilient mounting means may take any suitable form. For example, in a preferred construction the resilient mounting means comprises an elastomeric adhesive which sticks the friction material member to the support member and which allows the friction material member to move towards the support member by the resilient deformation of the adhesive.

Example of such elastomeric adhesive arrangements are disclosed in, for example, published patents EP 0252583, EP 0323036, EP 0390797, EP 0442539, EP 0455694, EP 0510014, EP 0638149, GB 2247725, GB 2243419.

In an alternative form of the invention the friction material may be resiliently mounted on spring steel supports which allow the friction material to move towards the support member and hence cushion the engagement of the clutch, the stops being built into the friction material and/or the spring supports.

The friction element assembly will normally comprise two friction material members in a back to back arrangement, one friction member for engagement with the pressure plate and the other with the reaction member with the resilient mounting means in between the friction material members.

In one construction both back to back friction material members are resiliently mounted on opposite sides of a support member.

In an alternative construction on of the back to back friction material members is nonresiliently mounted on one side of the support member and the other friction material member is resiliently mounted on the other side of the support member.

Several embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which :- Figure 1 shows an axial section through a clutch installation which includes a friction element assembly in accordance with the present invention; Figure 2 shows details of the friction element assembly used in figure 1 on a larger scale, and Figures 3 to 5 show details of other forms of friction element assembly in accordance with the present invention.

Referring to figure 1 this shows a clutch installation in which a clutch friction element assembly in the form of a driven plate 10 is clamped between a flywheel 11 and a pressure plate 12 by a diaphragm spring 13. The diaphragm spring is supported at its outer periphery in

the normal manner from a clutch cover 14 which is bolted at 15 to the flywheel 11. Drive pins 12a prevent the relative rotation of diaphragm spring 13 and pressure plate 12. The clutch is released from the clamped condition shown by moving the release bearing 16 in the direction X using any suitable form of clutch release mechanism.

The driven plate 10 comprises an outer annular portion 17 which is rivetted at 18 to an inner central disc portion 19 which includes a central hub 20 which is splined onto a gearbox input shaft 21 which passes down the centre of the release bearing 16. As is conventional the central disc portion 19 of the driven plate includes torsional damping springs 22 and a friction damping pack 23.

In accordance with the present invention the outer annular portion 17 of the driven plate 10 comprises an annular metal support member 24 and two back to back annular friction material members 25 & 26 respectively. The friction material member 25 is non-resiliently glued to the support member 24 as indicated at 27 in figure 2. The other friction material member 26 is resiliently glued to the other side of support member 24 by generally circumferentially extending beads of resilient adhesive 27 such as that available under the trade name Rhodorsit CAF 99 AXAD Black (PEX) from the French company Rhône-Poulenc which is an RTV (Room Temperature Vulcanisation) silicone based elastomeric adhesive.

Friction material member 26 is provided on its side facing the support member 24 with axially extending projections 28 which in the uncompressed condition of the driven plate are spaced from the support member 24 by a distance Y shown in figure 2.

When the clutch is engaged and the driven plate is clamped by the diaphragm spring 13 between the flywheel 11 and the pressure plate 12, the friction material member 26 is moved towards the support member 24 thus cushioning the engagement of the clutch until the axial projections 28 contact the support member 24 whereupon the driven plate becomes solid in an axial sense and no further cushioning of the clutch engagement occurs. This ensures a predictable clutch clamping load when the clutch is fully engaged.

As will also be appreciated when the axial projections 28 contact the support member 24 the orientation of the friction member 26 relative to the support plate 24 is accurately controlled to be in the required parallel relationship.

As will be appreciated by reference to the previously referred to Applicant's earlier published patents, the constructional details of the support member 24 and the patterns with which the adhesive beads 27 are applied to the support member 24 may have many variants the details of which do not form part of the present invention.

Referring to figure 3, this shows an alternative form of the present invention in which the support member 24 again has rigidly adhered to it a first friction material member 30 and has resiliently adhered to it a second friction member 31 via resilient adhesive beads 32. In this construction the stops which control the axial displacement of the resiliently mounted friction material member 31 are provided by rivets 33 which again provide the control clearance Y between the side 31 la of the friction material member 31 facing the support member 24 and the support member itself. Again when the clutch is engaged this clearance Y is taken up and once the side 31 la of the friction member 31 contacts the rivets 33 no further axial compression of the driven plate is possible and the position of the friction member 31 is also again accurately controlled.

Figure 4 shows a yet further form of the present invention in which the support member 24 has rigidly adhered to it a first friction material member 40 and has resiliently adhered to it a second friction member 41 using resilient beads 42. In this construction, the stops which control the axial displacement of the friction material member 41 are provided by axially extending projections 40 which are pressed out of the support member 24. These axial projections 40 may be generally circular in form or could take the form of circumferentially extending ridges pressed out of the support member.

Although in the examples described above only one of the friction material members has been resiliently mounted on the support member it is within the scope of the present invention that both friction members should be so mounted. Also, though in the examples

described above only resilient adhesive has been used to provide the resilient mounting of the friction material member on the support member this resilient mounting could be achieved using the conventional spring metal resilient mounting conventionally used in current cushioned driven plates.

Also, it is not necessary for the friction material members to be continuous annuli they could, for example, be in the form shown in figure 5 where discreet pads of friction material 50 are secured on both sides of a support member 24 at widely spaced circumferential positions.

Claims

CLAIMS 1. A friction element assembly of the type described characterised in that stop means are provided to limit the cushioning movement of the friction material when the assembly is clamped between the pressure plate and the reaction member.
2. A assembly according to claim 1 comprising a support member and resilient mounting means for mounting the friction material member on the support member with the stop means on the friction material member, or the support member, or on both members.
3. An assembly according to claim 2 in which the face of the friction material member which faces the support member is provided with stop means in the form of a plurality of axially extending projections which contact the support member after a predetermined amount of movement of the friction material member towards the support member as the clutch is engaged.
4. An assembly according to claim 1 in which the stop means comprise axial projection formed in or carried by the support member which engage the face of the friction material member which faces the support member after a predetermined amount of movement of the friction material member towards the support member as the clutch is engaged.
5. An assembly according to claim 4 in which the stop means comprise rivets carried by the support member which are contacted by the friction material member after the predetermined amount of movement of the friction material member towards the support member.

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6. An assembly according to claim 4 in which the stops means comprise axially projections pressed out of the support member which are contacted by the friction material member after the predetermined amount of movement of the friction material member towards the support member.
7. An assembly according to any one of claims 1 to 6 in which two friction material members are mounted in a back to back arrangement on opposite sides of the support member.
8. An assembly according to claim 7 in which both friction material members are resiliently mounted on opposite sides of the support member.
9. An assembly according to claim 7 in which one friction material member is non- resiliently mounted on one side of the support member and the other friction member is resiliently mounted on the other side of the support member.
10. An assembly according to any one of claims 1 to 9 in which both the friction material member (s) and support member are of annular form.
11. An assembly according to any one of claims 1 to 9 in which one or both of the friction material member (s) and the support member are of arcuate form with a number of such arcuate member positioned circumferentially adjacent each other to form a complete annular assembly.
12. An assembly according to any one of claims 1 to 11 in which the resilient mounting means comprise an elastomeric adhesive which sticks the friction material member to the support member and which allows the friction material member to move towards the support member by the resilient deformation of the adhesive.
13. An assembly according to any one of claims 1 to 11 in which the resilient mounting means comprises spring steel supports which allow the friction material to move

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towards the support member and hence cushion the engagement of the clutch, the stop means being built into the friction material and/or the spring supports.
14. A friction element assembly constructed and arranged substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or 3 or 4 or 5 of the accompanying drawings.