This invention relates to vehicle driveline clutches and in particular to details of the driven plates of such clutches which are designed to be connected with a transmission input shaft and clamped between a pressure plate and an engine flywheel to transmit drive from the engine to the transmission.

It is well known to include in such clutch driven plates a torsion damping means, for example in the form of torsionally acting springs and/or friction devices, to damp torsional vibrations which occur in the vehicle driveline.

It is also known that it is desirable for the torsional friction damping of such driven plates to be different when the clutch is operating in its "drive" mode form when the clutch is operating in the so-called "overdrive" mode in which the engine is effective operating as a brake. Also, in the past, the torsional friction damping arrangements proposed tend to use tab and slot connections of the various friction members which introduce circumferential play in the connections of the friction members which in turn introduces delay in the operation of the frictional forces.

It is an object of the present invention to provide an improved form of clutch driven plate which addresses one or more of the above problems.

Thus according to the present invention there is provided a clutch driven plate comprising axially spaced first and second side plates, friction elements carried by one of the side plates, a hub flange located intermediate the side plates and rotatable with a hub for driving connection with an associated transmission shaft, circumferentially orientated springs acting between windows in the side plates and hub flange to resist circumferential rotation between the side plates and flange, the driven plate being characterised in that an inner friction plate is rigidly fixed to one of the side plates for rotation therewith, an intermediate plate is rotatable with the hub flange in one direction of rotation only and is located between the inner friction plate and said one of the side plates, and an axially acting spring is located between the side plates tending to bias the inner friction plate towards the intermediate plate in order to generate frictional resistance to the relative rotation of the side plates and flange.

In such an arrangement since the inner friction plate is rigidly fixed to one of the side plates it must rotate at all times with that side plate without any delay so that the frictional resistance to the relative rotation between the side plates and the flange is generated immediately any such relative rotation occurs. Also, since the intermediate plate is driven with the hub flange in one direction of rotation only, the frictional resistance in the drive condition can be higher than the in the overdrive condition.

Conveniently, the inner friction plate may be formed as an integral part of an annular disc which carries the friction elements at its outer periphery. This is a particularly economical arrangement in which the annular disc is simply extended inwardly at its normal inner periphery to provide this friction plate.

The inner friction plate may be secured directly to the internal surface of one of the side plates by axially extending stop pins which secure the two side plates together.

The axially extending stop pins may extend through slots in the hub flange to limit the maximum relative rotation between the side plates and flange.

The intermediate plate may be provided with abutments which co-operate with abutments on the flange to drive the intermediate plate with the flange in said one direction of rotation only.

Conveniently, the axially acting spring may be located on the other side of the hub flange from the inner friction plate and the intermediate plate and acts towards the flange to bias a second friction plate which rotates with the other side plate into frictional contact with a friction member which rotates with the hub flange. This provides a further friction damping capability which acts in both the drive and overdrive modes.

One embodiment 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 driven plate in accordance with the present invention;

Figures 2, 3 & 4 show partially cutaway, the upper part of figure 1 viewed in the direction of arrow X in the static, drive and overdrive conditions respectively, and

Figure 5 shows the annular segmented disc used to support the friction elements and provide the inner friction plate of the invention.

Referring to the drawings, the clutch driven plate 10 has a pair of first and second side plates 11 and 12 which are interconnected by stop pins 13 which extend through holes 13a and which carry friction elements 14 rivetted at 14a on opposite sides of a segmented annular disc 15 (shown in detail in figure 5). Side plates 11 and 12 are in turn mounted on a drive hub 16 via an annular plastics centring washer 17.

Although, in the example illustrated, a segmented disc 15 is used with radial slots 15e which define individual axially corrugated arcuate segments 15f on which the friction elements are supported to provide an axially cushioned friction element arrangement, any form of disc may be used to support the friction elements 14 which may or may not be axially cushioned and which may be of continuous annular form or in the form of individual circumferential spaced friction elements.

Hub 16 supports a drive flange 18 which has an internal periphery with cut-outs 18a which mesh with teeth 16a on hub 16 to allow limited circumferential rotation of drive flange 18 relative to hub 16. This limited circumferential rotation is controlled by first circumferentially acting low rate compression springs 19. This construction provides the conventional so-called "idle rattle" damping centre.

Drive flange 18 is connected with side plates 11 and 12 via second higher rate main drive springs 20 which extend in windows 21 in side plates 11 and 12 and corresponding windows 22 and 23 in flange 18 and disc 15 respectively.

In conventional manner the amount of relative rotation allowed between side plates 11 and 12 and flange 18 is controlled by the stop pins 13 which extend through slots 24 in flange 18. The springs 20 thus damp torsional vibrations when in the "drive" mode.

In accordance with the present invention, the segmented annular disc 15 has formed at its inner periphery an inner friction plate 25 which is in the form of four arcuate components 25a, 25b, 25c and 25d. These components can be provided with, for example, sintered friction material or specific surface treatments on one or both axially facing sides to provide the required friction.

As indicated above, the segmented disc 15 is riveted to side plate 11 by stop pins 13 so that the friction plate 25, made up from components 25a to 25d, is rigidly fixed to the side plate and rotates at all times therewith.

Between the friction plate 25 and the side plate 11 is located an intermediate friction plate 26 which is supported on centring washer 17 and provided with axially projecting lugs 27 which extend into the windows 22 of drive flange 18 adjacent the ends 22a of these windows. On the other side of flange 18 a second plastics friction washer 28 is provided which rotates with the flange 18 via projections 17a on washer 17 which extend through opening 18b in flange 18 to engage openings 28a in washer 28. A second friction plate 29 is keyed for rotation with the other side plate 12 by axially projecting tabs 30 which extend through cut-outs 31 in the side plate. An annular axially acting wavy washer spring 32 acts between the second friction 03348

plate 29 and side plate 12 to bias the plate 29 and washer 28 towards flange 18 and, hence through stop pins 13, pulls the other side plate 11 towards flange 18. Thus spring 32 provides the axial force to generate friction between all these contact components on relative rotation.

Figure 2 shows the driven plate in its static position in which the stop pins 13 are located at an intermediate position in slots 24. As can be seen most clearly from figure 3, the slots 24 have a greater extent X in the "drive" direction than their extent Y in the "overdrive" direction thus more relative rotation is allowed between the side plates 11 and 12 and the flange 18 in the "drive" mode than in the "overdrive" mode as will be explained briefly below.

With the drive plate in the "static" mode shown in figure 2, the main drive springs 20 are not compressed. When the driven plate is in the "drive" mode shown in figure 3, the friction elements 14 and connected disc 15 and side plates 11 and 12 tend to rotate relative to the drive flange 18 and the output hub 16 so that the main drive springs 20 are compressed as the stop pins 13 move along slots 24 to the figure 3 position in which they limit any further relative rotation between the side plates 11 and 12 and the drive flange 18 by contact with the ends 24a of the slots. During this relative rotation between the side plates and the output hub 16 the lugs 27 on the intermediate friction plate 26 are trapped against the end 22a of window 22 so that the intermediate friction plate is rotated with the drive flange 18. Thus the relative rotation between the side plates and output flange when in the "drive" mode results in friction being generated between the side plate 11 and the intermediate friction plate 26, between the intermediate friction plate 26 and the centring washer 17 and between the second friction washer 28 and the second friction plate 29 all under the action of spring 32. This friction acts to further damp oscillations in the associated driveline.

When the driven plate is in the "overdrive" mode shown in figure 4 the friction elements 14, side plates 11 and 12 and segmented disc 15 all move in the opposite direction relative to the drive flange 18 This movement is limited by the contact between the stop pins 13 and the other ends 24b of the slots 24. In the "overdrive" condition the end 22a of the window 22 moves away from the lugs 27 so that the intermediate friction plate is not drawn around with the drive flange 18. Thus in the "overdrive" mode friction is only generated by spring 32 between the disc 15 and the centring washer 17 and between the second friction washer 28 and the second friction plate 29.

Thus more friction damping of driveline oscillations is generated in the "drive" mode than in the "overdrive" mode.

Also, since the segmented friction disc is at all times rigidly connected with the side plates 11 and 12, friction is always generated immediately there is any relative movement in the drive direction between the segmented disc 15 and the contacting components 26 and 17.