GB2286021A - Friction clutch with wear adjustment - Google Patents

Abstract

A friction clutch (10) in which a driven plate (11) is clamped between a flywheel (12) and a pressure plate (13) by a diaphragm spring (17) and in which a disengageable release means (20) including pegs (21) is provided for moving the pressure plate (13) away from the driven plate (11) to release the clutch. The release means disengages during engagement of the clutch when adjustment of the clamped position of the pressure plate is necessary due to drive plate wear and subsequently re-engages at an adjusted position to ensure substantially constant clutch release load and travel throughout the life of the clutch. <IMAGE>

Description

CLUTCHES This invention relates to clutches and in particular to clutches for use in motor vehicles in which a driven plate is clamped between a flywheel or other reaction member and a pressure plate by spring means which reacts against a clutch cover which is connected with the flywheel. Such a clutch is hereinafter referred as a clutch of the type specified.

Clutches of the type specified suffer from problems associated with driven plate wear since this wear causes movement of the position of the pressure plate towards the flywheel when the clutch is in the clamped position which in turn causes changes in clutch clamp load and hence pedal release effort as the driven plate wears. Such clutches also suffer from the need to adjust the effective length of the clutch release linkage as the driven plate wears.

It is an object of the present invention to provide an improved form of clutch of the type specified which overcomes the above problems by automatically compensating for the wear of the driven plate.

Thus according to the present invention there is provided a clutch of the type specified in which a disengageable release means is provided for moving the pressure plate away from the driven plate to release the clutch, said release means disengaging during engagement of the clutch when adjustment of the clamped position of the pressure plate is necessary due to drive plate wear and subsequently re-engaging at an adjusted position to ensure substantially constant clutch release load and travel throughout the life of the clutch.

The spring means preferably comprises a belleville spring with a substantially flat load/deflection characteristic.

The disengageable release means preferably includes lever means movable in a clutch releasing direction and disengageably connected with the pressure plate.

One or more axially extending connecting members preferably extend between the lever means and the pressure plate.

The connecting members may be disengageably coupled with the pressure plate by ratchet means.

A surface on the or each connecting member may be arranged to contact an abutment on the flywheel or cover to deflect the connecting member to disengage the ratchet means during clutch engagement and the ratchet means is re-engaged when said surface disengages the abutment.

In an alternative construction the or each connecting means passes through an aperture in the pressure plate and movement of the lever means in the clutch disengaging direction causes the or each connecting means to tilt in its aperture and hence grip the pressure plate enabling disengagement of the clutch.

In such a construction the tilting of the or each connecting means may be caused by a cam means on the connecting means which is contacted by the lever means during movement of the diaphragm spring in the clutch disengaging direction.

In a still further construction the pressure plate is provided with projections which extend through apertures in the lever means and gripping means are provided which lock the projections to the lever means on movement of the lever means in the clutch disengaging direction.

In this construction the gripping means for each projection may comprise a bush mounted on the lever means which surrounds the projection and which ns provided with one or more formations which grip the projection as the lever means attitude, and hence the bush attitude, changes during movement of the lever means in the clutch disengaging direction.

Preferably the lever means comprises a diaphragm spring.

The present invention will now be described by way of example only, with reference to the accompanying drawings in which: Figures 1 and 2 are radial half sections through a vehicle clutch in accordance with the invention in its engaged and disengaged conditions respectively; Figure 3 shows certain details of the release means of figures 1 and 2 on a larger scale; Figures 4 and 5 respectively show the load/deflection characteristics of the belleville spring and diaphragm spring used in the clutch of figures 1 and 2; Figures 6 and 7 show radial half sections through a further form of clutch with an alternative form of release means; Figure 8 shows a radial half-section through a further form of clutch with a further form of release means; Figure 9 shows a radial half section through a further form of clutch with a further form of release means; Figures 10 to 12 show different stages in the operation of the release means of Figure 9, and Figure 13 shows a radial half section through a further form of clutch with a still further form of release means.

Referring to figures 1 and 2 these show a clutch 10 in which a driven plate 11 is clamped between a flywheel 12 and a pressure plate 13 by a belleville spring 14 which acts against an abutment 15 on the clutch cover 16. The clutch is released by disengageable release means 20 which includes a diaphragm spring 17 which acts as a lever means and which is connected with the pressure plate 13 by axially extending connecting means in the form of pegs 21 which extend through apertures 25 in radially extending lugs 13a on the outer periphery of the pressure plate and through apertures 14a in the belleville. The diaphragm spring 17 is mounted on cover 16 in the conventional manner by tags 19 which clamp the diaphragm between fulcrum rings 18.

One end of each peg has a grooved portion 22 which engages the outer periphery of the diaphragm spring and a mid portion with ratchet teeth 23 which engage a ratchet member 24 on the pressure plate (see fig. 3). The ratchet teeth 23 and ratchet member 24 are biased into engagement by a spring member 26 which acts in the associated aperture 25.

With ratchet teeth 23 in engagement with ratchet member 24 the pegs 21 are able to retract the pressure plate to disengage the clutch when the inner periphery of diaphragm spring 17 is pushed in direction X of figure 2 by a clutch release bearing (not shown) in the normal manner.

The pressure plate 13 is clamped against the driven plate 11 solely by the belleville spring 14.

The load deflection characteristic of the belleville spring 14 is shown in figure 4. It can be seen from figure 4 that the clamping force of this spring remains substantially constant for a significant deflection range. Thus as the driven plate 11 wears it is clamped against the flywheel under a substantially constant load.

The diaphragm spring 17 is used solely for releasing the clutch. The load/deflection characteristic of the diaphragm spring 17 is shown in figure 5, The diaphragm spring is designed so that as it is deflected through its flat condition it will effectively supply a negative clamp load i.e. it will assist the release of the clutch by helping to oppose the force of the belleville spring 14. When the clutch is engaged (see Fig 1) the diaphragm spring will be at point 1 in figure 5. In this position a small force will be pulling the pegs 21 away from the flywheel 12 but this will not be large enough to significantly effect the clamp load supplied by the belleville spring (14).

When the clutch is disengaged the diaphragm spring will be over flat and at point 2 in figure 5. At this point the force applied by the diaphragm spring 17 will be large enough to significantly reduce the pedal effort but will be less than the force applied by the belleville spring 14, so the clutch will re-engage when the clutch pedal is released.

Whenever the clutch is engaged each ratchet member 24 is arranged to engage its associated ratchet teeth 23. Thus the clutch can be instantly disengaged by pushing diaphragm spring 17 in direction X at any time.

As the driven plate 11 wears the pressure plate 13 and hence the pegs 21 will move closer to the flywheel. Eventually when sufficient wear of the driven plate has taken place cam surfaces 27 on the pegs 21 will contact inclined abutments 28 on cover 16. This tilts the pegs 21 radially inwardly as indicated by arrow Y in fig 1 to disengage ratchet teeth 23 from ratchet member 24. This allows the pegs to be pulled away from the flywheel 12 by the diaphragm spring 17 while the pressure plate 13 is held stationery between the driven plate 11 and the belleville spring 14. The pegs 21 will thus move away from the flywheel 12 until they are no longer in contact with the abutment 28 at which point the springs 26 will re-engage the ratchet teeth 23 with the ratchet members 24. The above described ratchet mechanism is so designed that it adjusts one ratchet tooth at a time. Thus, the movement of the pegs towards the flywheel before wear adjustment take place is no more than the distance between two consecutive ratchet teeth.

Figures 6 and 7 show another form of clutch in accordance with the present invention in which an alternative form of disengageable release means 30 is employed. The release means comprises a plurality of pegs 31 each of which has a hooked portion 32 which engages the outer periphery of the diaphragm spring 17. A ratchet means in the form of ratchet teeth 33 on the peg and a ratchet member 34 on the pressure plate is provided. Each peg 31 extends through an aperture 36 in the pressure plate and a spring clip 35 loads the peg sideways in its aperture to engage the teeth 33 with the ratchet member 34.

The ratchet teeth 33 and the ratchet member 34 are disengaged during engagement of the clutch by the abutment of angled surface 37 on the peg with angled abutment 38 formed on the flywheel 12.

Thus, as in the previously described construction, following contact between surface 37 and abutment 38 each peg swings in direction Y1 so that ratchet teeth 33 disengage the ratchet member 34 to allow the ratchet member to engage behind the next tooth 33.

Figure 8 shows a still further construction in which a further form of disengage able release means 40 is provided which comprises a plurality of pegs 41 which pass with good clearance through apertures 42 in the pressure plate 13. The inner edges of apertures 42 are angled as shown at 43. The end of each peg is provided with a hooked portion 44 which engages the outer periphery of the diaphragm spring 17 and which includes a cam portion 45 which causes each peg to tilt outwardly as indicated by arrow Y2 in figure 8 when the diaphragm spring is pushed in direction X thus wedging each peg against the angled portion 43 of its respective aperture so that the pins claw around the pressure plate and enable the diaphragm spring to retract the pressure plate out of contact with the driven plate 11 so the clutch can be disengaged.

In the arrangement shown in figure 8, movement of the pressure plate 13 towards the flywheel 12 during engagement of the clutch is not restricted by the release means 40 since during engagement of the clutch the diaphragm spring 17 no longer engages the cam portion 45 of each peg.

Figures 9 to 12 show an alternative form of release means 50 in which the pressure plate 13 is provided with a plurality of axially extending projections 51 which extend through apertures 52 in the diaphragm spring. Each diaphragm aperture 52 supports a bush 53 (shown on a larger scale in figures 10-12). The bush is designed to surround the associated projection 51 and has two axially projecting tabs 54 which are designed to grip the projection 51 as the attitude of the diaphragm spring changes during the release of the clutch.

Figure 10 shows the position occupied by the bush 53 when the pressure plate 13 is clamping the driven plate 11 against the flywheel 12 to engage the clutch. In this position the bush 53 does not grip the associated projection 51 to allow free movement of the pressure plate relative to the diaphragm spring 17 to ensure full application for the clutch.

As the diaphragm spring 17 is pushed in direction X of figure 9 to disengage the clutch the attitude of the diaphragm spring assumes the position shown in figure 11 in which the tabs 54 begin to grip the associated projection 51. Further movement of the diaphragm spring in the clutch disengaging direction changes the diaphragm spring attitude to that shown in figure 12 when the tabs 54 come into full gripping contact with their associated projections 51. By this means the bushes 53 carried by the diaphragm spring are able to grip the projections 51 to disengage the pressure plate 13 from the driven plate 11 during clutch release.

Figure 13 shows a still further form of release means 60 in which three axially projecting formations 61 are pivoted at 61a on the outer periphery of the pressure plate 13 and are connected with the diaphragm spring 17 via washer-like gripping members 64 which slide on each formation when the gripping members are at right angles to the formations. Three radially extending triggers 66 extend from the inner periphery of the diaphragm spring and each have an outer forked portion 67 which engages a respective gripping member 64. Each trigger pivots at a mid point 68 on the clutch cover 16.

In the construction shown in Figure 13 the belleville spring 14 acts adjacent its inner periphery on the clutch cover 16 via tags 19 and pushes on the pressure plate 13 via raised fulcrum 13b.

Figure 13 shows the clutch in the engaged condition in which the formations 61 slide through the gripping members 64 to allow unrestricted engagement of the clutch.

To disengage the clutch the diaphragm spring is moved in the direction X which also pivots triggers 66 so that gripping members 64 are tilted (See dotted detail 64a) relative to formations 61 and grip the formations. Hence movement of the diaphragm spring is transmitted through gripping members 64, formations 61 and hence to the pressure plate 13 to disengage the clutch. As will be appreciated it is the objective to maintain the attitude of the diaphragm spring 14 substantially the same as that shown in Figure 13 as the driven plate 11 wears. This is achieved by the belleville spring 15 adopting a progressively more coned construction as the driven plate wears and the formation 61 sliding through the gripping member 64 when the triggers 66 are not activated.

It will also be appreciated that although the various release means have been described above as co-operating with the diaphragm spring adjacent its outer periphery the release means could alternatively co-operated with the diaphragm spring adjacent its inner periphery.

Claims (15)

1. A clutch of the type specified in which a disengageable release means is provided for moving the pressure plate away from the driven plate to release the clutch, said release means disengaging during engagement of the clutch when adjustment of the clamped position of the pressure plate is necessary due to drive plate wear and subsequently re-engaging at an adjusted position to ensure substantially constant clutch release load and travel throughout the life of the clutch.

2. A clutch according to claim 1 in which the spring means comprises a belleville spring with a substantially flat load/deflection characteristic.

3. A clutch according to claim 1 or claim 2 in which the disengageable release means includes lever means moveable in a clutch releasing direction and disengageably connected with the pressure plate.

4. A clutch according to claim 3 in which one or more axially extending connecting members extend between the levers means and the pressure plate.

5. A clutch according to claim 4 in which the connecting members are disengageably coupled with the pressure plate or lever means.

6. A clutch according to claim 5 in which the connecting members are disengageably coupled with the pressure plate by ratchet means.

7. A clutch according to claim 6 in which a surface on the or each connecting member contacts an abutment on the flywheel or cover to deflect the connecting member to disengage the ratchet means during clutch engagement and the ratchet means is re-engaged when said surface disengages the abutment.

8. A clutch according to claim 7 in which the ratchet means is re-engaged by a bias means.

9. A clutch according to claim 4 in which the or each connecting means passes through an aperture in the pressure plate and movement of the lever means in the clutch disengaging direction causes the or each connecting means to tilt in its aperture and hence grip the pressure plate enabling disengagement of the clutch.

10. A clutch according to claim 9 in which the tilting of the or each connecting means is caused by a cam means on the connecting means which is contacted by the lever means during movement of the diaphragm spring in the clutch disengaging direction.

11. A clutch according to any one of claims 1 to 3 in which the pressure plate is provided with projections which extend through apertures in the lever means and gripping means are provided which lock the projections to the lever means on movement of the lever means in the clutch disengaging direction.

12. A clutch according to claim 11 in which the gripping means for each projection comprises a bush mounted on the lever means which surrounds the projection and which is provided with one or more formations which grip the projection as the lever means attitude, and hence the bush attitude, changes during movement of the lever means in the clutch disengaging direction.

13. A clutch according to any one of claims 1 to 3 in which the pressure plate is provided with axially extending projections upon each of which a gripping member slides, said gripping members abutting the diaphragm spring, and trigger means for tilting said gripping means relative to the projection to lock the gripping means against sliding on the projections to connect the diaphragm spring and pressure plate for clutch release on movement of the diaphragm spring in the clutch disengaging direction.

14. A clutch according to any one of claims 3 to 13 in which the lever means comprises a diaphragm spring.

15. A clutch of the type specified constructed and arranged substantially as hereinbefore described with reference to and as shown in figures 1 to 3 or 6 and 7 or 8 or 9 to 12 or 13 of the accompanying drawings.