GB2336411A - Clutch wear sensor and torque strap attached by same fastener to cover - Google Patents

Abstract

An automatically adjusting clutch 10 comprises fastening means, eg rivet 19, which connects torque straps 14 and driven plate wear sensing means, eg pawl mechanism 50, to a clutch cover 21. The torque straps 14 are attached via rivet 18 to pressure plate 13 so that it is rotational fast with but axially moveable relative to the cover 21. Pawl mechanism 50 pivots about an axis and engages with adjuster teeth 44 so that it may effect adjustment of the clutch 10 by moving over the teeth 44 to engage behind a tooth so that subsequently the pawl mechanism 50 moves a first part of the pressure plate 13 relative to a second part of the pressure plate 13. Spring means 57A may engage or be part of a bracket 51 and bias the pawls into engagement with the teeth 44.

Description

2336411 A2624GB AUTOMATICALLY ADJUSTING CLUTCH The present invention

relates to automatically adjusting clutches, and in particular to clutches for use on motor vehicles.

Known automatically adjusting clutches are complicated and expensive to produce.

It is an object of the present invention to produce a simple and cheap automatically adjusting clutch which is reliable in operation.

Thus according to a first aspect of the present invention there is provided an automatically adjusting clutch having a pressure plate which is held rotationally fast with a clutch cover via torque straps, the clutch also including at least one driven plate wear sensing means, the or each wear sensin means being attached to the clutch cover via fastening means which also g attaches one of the torque straps to the cover.

In accordance with a second aspect of the present invention, there is provided an automatically adjusting clutch having a pressure plate which is held rotationally fast with a clutch cover via torque straps, the clutch also including at least one means for effecting adjustment of the clutch to compensate fbr wear, the or each adjustment effecting means being attached to the clutch cover via fastening means which also attaches one of the torque straps to the cover.

Both aspects of the invention provide an automatically adjusting clutch having a simplified construction in which the number of fastening means required can be reduced compared'to a construction in which the wear sensing means and/or the adjustment effecting means are a 4 Figure 8 is an axially partially cutaway view of a second embodiment of an automatically adjusting clutch according to the present invention looking towards an associated engine'.

Figure 9 is an enlarged cutaway view of part of figure 8.

Figure 10 is a radial view of the clutch of figure 8 taken in the direction of the arrow J of figure 9; Figure 11 is a cross section view of the clutch of figure 8 taken along the line KK of figure 9, Figure 12 is an axial view of part of a third embodiment of an automatically adjusting clutch according to the present invention looking towards an associated engine; Figure 13 is a cross section view of the clutch of figure 12 taken along the line DD of figure 12, Figure 14 is a radial view of the clutch of figure 12 taken in the direction of arrow E of figure 12 with the adjuster wheel 190 and annular mass 130 shown dotted so as not to obscure the pawl 160, and Figure 15 is a schematic radial view of a fourth embodiment of an automatically adjusting clutch according to the present invention.

With reference to figures 1 to 6 there is illustrated an automatically adjusting clutch 10 which includes a flywheel 11, a clutch cover assembly 20 and a driven plate 15. The flywheel 11 is fixed to the end of a crankshaft (not shown) of an associated internal combustion engine 3 Figure 3)A is an enlarged view of a modified form of the first portion 310 of figure 3 taken in the direction of arrows BB of figure I A; Figure 4 is an isometric exploded view of a pawl mechanism and associated components of the clutch of figure 1, Figure 5 is a radial view of part of the clutch of figure 1 in the direction of arrow C of figure 1 A with bracket 5 1 A not shown for clarity; Figures 5A to 5E are a series of schematic radial views of the clutch of figure 1 in the direction of arrow C of figure I A showing the following.. - Fig 5A - an unworn engaged clutch, Fig 5B - an unworn disengaged clutch, Fig 5C - a partially worn engaged clutch prior to adjustment, Fig 5D - a partially worn disengaged clutch about to adjust, Fig 5E - a panially worn engaged clutch., Fig SF is a schematic view taken in the direction of arrow H of figure 5B showing the adjuster teeth, Fip-ure 6 is a schematic developed view sinfflar to the views of figures 5A to 5E showing the relationship of the pawl teeth to the adjuster teeth of the clutch of figure 1-, Figure 7 is a view similar to figure 5 of a modified form of the clutch of figure I; 6 On the axial side of the first part 30 remote from the flywheel 11 there is a circumferentially arranged annular array of nine undulations 32 (see figures 1 and 3), facing towards the diaphragm spring 12. In cross section each undulation consists of a relatively short flat section 32A, a relatively long ramp section 32B of a relatively shallow gradient and a relatively short fl ramp section 32C of relatively steep gradient which joins adjacent ramp sections 32B and at sections 32A of adjacent undulations 32.

A portion of the outer periphery of the first part remote from the flywheel is formed as an annular spigot -3)3 (see Figure 2).

Pivot ring 40 is annular in shape and may be made as a pressing. The radially outer section 41 (see Figure 2) is formed parallel and concentric to the axis of the clutch 10. The radially inner surface 42 of the outer section 41 is formed as an annular recess which engages with the spigot 3-) -31 to keep the pivot ring 40 concentric with the first part 3 0. The outer surface 43 of the outer section 41 has a continuous circumferentially orientated array of pivot ring adjuster teeth 44 each tooth being of part helical form. In this case there are 241 teeth in total. Each tooth has a flank portion 44A of relatively low gradient and an edge portion 44B of relatively steep gradient (see figure 5F).

The radially outer section 41 is connected to a pivot section 45 of the pivot ring 40. This pivot section 45 is contacted by the radially outer portion 12B of the diaphragm spring 12 and as the clutch 10 is engaged and disengaged the spring rotates about the pivot section 45.

The pivot section 45 is connected to a radially inner section 46 which has a circumferentially arranged annular array of 9 undulations 47 (see figure 3), which face and contact the undulations 32.

The clutch cover assembly 20 comprises a clutch cover 21, a diaphragm spring 12, a pressure plate 13, torque straps 14 and pawl mechanisms 50A, 50B, SOC which form part of an adjuster means. The clutch cover 21 is fixed rotationally and axially fast to the flywheel 11 by bolts (not shown) and supports the diaphragm spring 12 via two support rings 22 situated one on each axial side of the diaphragm spring 12 in a manner well known in the art. The diaphragm spring biases the pressure plate 13 towards the flywheel 11.

The clutch driven plate 15 is situated between the pressure plate 13 and flywheel 11 and is connected to the input shaft of a gear box (not shown). When the clutch is engaged Le. the diaphragm spring 12 biases the pressure plate 13 towards the flywheel, power can be transmitted between the associated engine and gearbox.

By applying an axial force to the fingers 12A of the diaphragm spring 12 towards the flywheel 11 the clutch can be disengaged in a manner well known in the art.

The pressure plate 13 comprises a first part 30 coaxial with a second part in the form of a pivot ring 40. First part 30 is generally annular in shape and has significant thermal mass and is thus capable of absorbing heat generated by frictional contact with the adjacent friction facing 16 of the driven plate 15 during engagement and disengagement of the clutch 10. On the radially outer periphery of the first part 30 there are three circumferentially equi-spaced lugs 3) 1. Each lug is fixed to one end 14A of Litangentially orientated torque strap 14 by a rivet 18. The other end 14B of the strap 14 is fixed to the clutch cover 21 by a rivet 19. The straps 14 ensure the first part 30 remains concentric with and rotationally fast with the clutch cover 21 but allow axial movement of the first pwt 30 relative to the clutch cover 2 1. When the clutch is engaged the straps 14 are stressed and bus the first part 30 away from the flywheel. This biasing assists in separating the first part 30 from the driven plate 15 when the clutch is disengaged.

8 In operation the relative rotation of the second part of the pressure plate (pivot ring 40) about axis 40' relative to the first part (3 W) is effected by three identical pawl mechanisms 50A, 50B and 50C which cause the pressure plate to increase in thickness incrementally by an amount substantially similar to the decrease in thickness of the ffiction facings 16 as wear takes place.

Pawl mechanism 50A is built as a sub-assembly and consists of a bracket 51 a pawl means 60A a pawl bias means 57A and a pawl rivet 70 (see figure 4).

The bracket 51 is formed from sheet metal with three flat portions 5 1 A, 5 1 B, and 5 1 C. Flat portions 5 1A and 5 IC are bent at 90 degrees to and adjoin flat portion 5 1B.

Flat portion 5 1 B has a hole 52 through which passes the rivet 19. The rivet 19 serves to fix the bracket 5 1 and end 14B of a strap 14 to the clutch cover 2 1. The flat portion 5 1 A lies in close proximity to the locally straight edge 21 A of the clutch cover and ensures that the bracket 5 1 can not rotate about the axis of the rivet 19. Flat portion 5 1 C faces substantially radially inwards and has a hole 53.

The pawl rivet 70 is formed in 4 sections, rivet heads 70A and 70D and shank portions 70B and 70C. Rivet head 70D and shank portions 70B and 70C serve to retain the rivet 70 fast in hole 53. Mounted on shank portion 70B adjacent the bracket 51 is the pawl bias means 57A, in the form of a cod spring. The pawl means 60A is also mounted on shank portion 70B and is between the pawl bias means 57A and the rivet head 70A. The pawl means can rotate to a limited extent on rivet 70 about rivet axis 70'. One end 58 of pawl bias means 57A engages an edge 54A of flat portion 5 1 C. The other end 5 9 of pawl bias means 5 7A is bent to engage an edge 61 of the pawl means 60A. The pawl bias means 57A is stressed (or pre- tensioned) so as to bias the pawl means 60A in the direction as indicated by arrow G of figure 4. Rotatioh of 7 When the clutch is assembled with new, unworn components flat section 47A, ramp section 47B and ramp section 47C of each undulation 47 face corresponding flat section 32A, ramp section 32B and ramp section 32C of undulations 32.

It will be apparent that relative rotation of the pivot ring 40 about its axis 40' (see figure 1) in the direction of arrow F of figure 3 relative to the first part 30 will cause ramp sections 47B td slide across ramp sections 3 2B and the effective axial thickness T of the pressure plate 131 will increase. The design is such that when the driven plate friction facings 16 are worn to their design limit there is still sufficient overlapping contact of ramp sections 32B, 47B.

When ramp sections 32B are in contact with ramp sections 47B and the clutch is engaged, the clamp load path of the diaphragm spring passes from ramp section 32B to ramp section 47B. This clamp load tends to rotate the pivot ring 40 relative to the first portion 30 to reduce the effective axial thickness of the pressure plate 13. This potential reduction in pressure plate thickness is resisted by ffiction between ramp sections 32B and 47B and between the pivot 45 and diaphragm spring 12. It can be advantageous to manufacture each ramp section 3)2B and 47B with serrations, 29 (see figure 3A) preferably radial serrations so as to prevent back rotation of the pivot rin-g- once the clutch is engaged. Similarly serrations could be formed on the pivot ring pivot 45 and the contacting surface of the belleville spring.

It is preferable that the circumferential angle between adjacent serrations as measured at the centre of the clutch is equal or less than the angle through which the pivot ring rotates as a result of one adjustment though this need not be the case.

In a further modification an independent ratchet mechanism could be used to prevent back rotation of the pivot ring.

However the spacing between pawl tooth 65A and 66B is 80 1/3) plus 2 2/3 (i.e. 241/3) plus 8J13 = 249/3) i.e. 83 times the pivot ring adjuster teeth pitch and they are thus in phase with each other having regard to the adjuster teeth 44. Similarly pawl teeth 65B and 66C are in phase as are pawl teeth 65C and 66A.

Operation of the auto-adjust clutch is as follows:

Considering pawl mechanism 50A with the clutch in an unworn condition-and engaged, pawl teeth 65A and 66A lie on flanks 44A of adjuster teeth 44 as shown in figure 5A. AS the clutch is disengaged the pressure plate 13) moves axially away from the flywheel 11 until the pivot ring 40 contacts a stop means 23 carried by the clutch cover 20 (see figure 5B). During disengagement the pawl teeth 65A and 66A slide across corresponding flanks 44A of adjuster teeth 44. Because of the helix angle of the adjuster teeth 44 the pawl teeth are effiectively sliding away from the edge 44B of the adjuster tooth corresponding to the flank on which they are engaged. During the whole of the disengagement movement of the pivot ring (in this case 1.5 mm) the teeth 65A,66A remain on their appropriate flank 44A. Note that the relative direction of movement between the pawl means and the array of adjuster teeth during this non adjusting disengagement operation is in the direction of =ow X (see figure 6) When the clutch is engaged the pressure plate 13 moves towards the flywheel and the pawl teeth slide relative to and across the corresponding flank 44A on adjuster teeth 44 in the direction Xuntil the fully engaged position is achieved.

When wear of the friction facings 16 has taken place and the clutch is engaged the pivot ring will be slightly closer to the flywheel by an amount equal to the amount of wear of the friction facings and during the subsequent disengagement of the clutch, the disengagement movement of the pivot ringyq11 be greater by the amount of wear that has taken place.

9 the pawl means 60A is limited in this direction by a stop in the form of bent tab 62 on the pawl means 60A contacting an edge 54B of the flat portion 5 1 C.

The pawl means 60A has two arms 63 and 64 with respective pawl teeth 65A, 66A at one end of the arms 63, 64. The pawl means 60A is made from a resilient material such as spring steel and as such the arms 63 and 64 can move a)dafly, having regard to the pawl rivet 70 axis, independently to a limited extent. Each arm 63, 64 is arranged to bias its corresponding pawl tooth 65A, 6A in a direction parallel to the axis 70' about which the pawl rotates into engagement with the array of adjuster teeth 44 of the pivot ring 40 of the pressure plate 13. Note however that the spacing S 1 between teeth 65A and 66A is out of phase with the pitch P of the adjuster teeth 44, teeth 65A and 66A being spaced 2 2/3 (i.e. 8/3) times the pitch of teeth adjuster 44 (see figure 5A).

Pawl mechanism 50B consists of bracket 51, pawl means 60B, pawl bias means 57B and pawl rivet 70, and pawl mechanism 50C consists of bracket 51 pawl means 60C, pawl bias means 57C and pawl rivet 70. Pawl means 60B carries pawl teeth 65B and 66B and pawl means 60C carries pawl teeth 65C and 66C.

Pawl mechanisms SOA, 50B and 50C are all identical and are spaced at 120 degrees around the circumference of the clutch, thus pawl teeth 65A, 65B, and 65C are similarly spaced at 120 degrees as are pawl teeth 66A, 66B. 66C. Because there are 241 pivot ring adjuster teeth 44 the spacing between pawl teeth 65A and 65B is out of phase with the pitch of the adjuster teeth 44, the spacing S2 between pawl teeth 65A and 65B being 80 1/3 (i.e. 24113) times the pitch of adjuster teeth 44 (see figure 6). Similarly the spacing between pawl teeth 65B and 65C, and between 65C and 65A is also 80 113 (i.e. 241/3) times the pivot ring adjuster teeth pitch. Also it is apparent that the spacing en pawl teeth 66A and 66B, 66B and 66, 66C and 66A is 80 1 /3 (i.e. 241/3) times the pivot ring adjuster teeth pitch.

12 phase pawl teeth (e. g. 66A and 65 C) of any two pawl means which are about to cause c adjustment of the pivot ring.

When the clutch is ful.ly disengaged the pivot ring 40 is no longer clamped between the first part 30 and the diaphragm spring 12 and is able to rotate in the direction F about the axis 40' relative to the first portion under the influence of the pawl bias means 60A until the corresponding tab 62 re-engages with corresponding edge 54B.

The clutch is designed such that the amount by which the pivot ring 40 is caused to rotate relative to the first part 30 produces an increase in effective thickness of the pressure plate 13 substantially equal to the amount of wear of the ffiction facings 16. Thus when the clutch is reengaged the pivot ring 40 is axially in its "unwom engaged" position (see figure 5D). It is 1 apparent that the pawl mechanism provides automatic adjustment of the clutch 10.

As previously described pawl tooth 66A is in phase with pawl tooth 65C, and once the predetermined amount of wear has taken place pawl tooth 65C engages with a corresponding adjuster tooth edge 44B and consequently when the clutch is fully disengaged pawl bias means 57C assists in the rotation of the pivot ring 40 relative to the first part 30.

Followmig a further pre-determined amount of wear, a further adjustment of the effective thickness of the pressure plate 1 3 takes place under the influence of pawl teeth 65B, and 66C.

The next adjustment takes place under the influence of pawl teeth 65A and 66B. The adjustment sequence then starts again with pawl teeth 66A and 65C.

Note that after two adjustments by pawl means 60A pawl tooth 65A is abutting an adjuster tooth flank 44A which pawl tooth 66A has previously abutted and potentially worn. However 11 Once a predetermined amount of wear of the friction facings 16 has taken place (in this case 0. 1 mm) the engaged position of the pivot ring 40 is sufficiently close to the flywheel for the pawl tooth 66A to slide past the flank 44A and engage with the edge 44B of the corresponding adjuster tooth (see figure SC), in other words the pawl tooth 66A engages behind the corresponding adjuster tooth. This efFectively senses that a predetermined amount of wear has taken place.

Similarly the in phase tooth 65C of pawl mechanism 50C also engages behind a corresponding adjuster tooth. The following description of the operation of pawl tooth 66A is applicable to the operation of pawl tooth 65C in relation to its corresponding adjuster components.

During the next disengagement of the clutch (see figure 5D), the pawl tooth 66A is unable to slide past its freshly engaged adjuster tooth edge 44B and therefore the disengaging movement of the pivot ring 40 causes the pawl means 60A to rotate about the axis 70' of its pawl rivet 70 against the pretensioned pawl bias means 57A to provide a potential adjustment force and thus the corresponding tab 62 disengages the corresponding edge 54B. During this stage the stress in pawl bias means 57A is being reacted at the adjuster tooth edge 44B against which the pawl tooth 66A is contacting and sliding along.

Since the tooth edge 44B is helical there is a component of reaction force which tends to rotate the pivot ring in the direction F relative to the clutch.

There is also a component of the reaction fbrce which biases the pivot ring towards the flywheel. To ensure that the pressure plate disengages the driven plate correctly, the force created by the torque straps forcing the pressure plate away from the flywheel must be greater than the component of force on the pressure plate towards the flywheel created by the in' 14 Thus whilst the combined torque strap and pawl bias means axial load of both clutches 10 and 10'is the same with unwom friction facings, the combined axial load with worn friction facings is less on clutch 10' than on clutch 10. This can be advantageous in some circumstances.

The second embodiment of an automatically adjusting clutch 210 shown in figures 8 to 11 is similar to the automatically adjusting clutch 10 of Figures 1 to 6 with equivalent components labeled 200 greater.

The main difference being: - a) clutch 210 has only one pawl mechanism 250 with only one pawl means 260, b) the pawl means 260 has three pawl teeth 265, 266, 267, and c) the pawl bias means is in the form of bracket 251 of spring steel.

The details of the mechanism 250 can be seen in figures 8 to 11.

The single pawl mechanism 250 comprises pawl means 260 riveted via pawl rivet 269 to bracket 25 1.

The pawl means 260 is made from a resilient material typically spring steel and consists of three pawl teeth 265, 266, 267 mounted on respective arms 263, 264, 264A. The arms are all cantilevered from a common fixing portion 268 and can move independently to a linfited extent relative to each other in the direction of the axis of pawl rivet 269.

13 since the pawl teeth 65A and 66A are axially separated (having regard to the axis of the clutch) pawl tooth 65A only contacts an unworn portion of said previously abutted flank 44A.

It will be noted that during an adjustment the direction of movement of the array of adjuster teeth (direction F) is substantially at 90 degrees to the direction of movement of the array of adjuster teeth during a non adjusting clutch engagement or disengagement operation (direction 2) and also at 90 degrees to the relative direction of movement between the array of adjuster teeth and pawl means during a non-adjusting clutch engagement (direction X) or disengagement (direction X) in this case the arrow Z, is parallel to the arrows X and X. Furthermore the edges 44B of the adjuster teeth 44 are inclined by the acute angle Y to the relative direction of movement between the array of adjuster teeth and the pawl teeth during a non adjusting disengagement operation (direction X) and during a non adjusting engagement operation (direction X). Also the axis Mabout which the pawl means rotate (see figure 1) is not parallel (but inclined in this case at 90 degrees) to the axis 40 about which the array of adjuster teeth rotate during adjustment (axis 40' being concentric with the axis about which the clutch rotates). The above design features allow the axial movement of the pressure plate and pivot ring 40 to be directly utilized in creating a rotational movement of the pivot ring 40.

Figure 7 shows a modified form of automatically adjusting clutch 10' in which one end 5 8' of each pawl bias means 5 7 (only one shown) reacts against the pivot ring 40 to bias the pivot ring 40 away from the flywheel to assist the torque straps 14' in biasing the pressure plate 13 away from the flywheel. This allows the bias load of the torque straps 14'to be less than the corresponding load of torque straps 14. As the associated facings wear the torque strap load produced by torque strap 14' increases, but by a smaller amount than the increase in torque strap load of torque strap 14.

16 Each pawl tooth 265, 266 and 267 is permanently engaged with a corresponding adjuster tooth 244 of the pivot ring 240 of the pressure plate 213. The pawl means is arranged such that the pawl teeth 265, 266, 267 are biased (in a direction parallel to the typical axis 25 1' about which the pawl rotates) into engagement with the array of adjuster teeth 244. Note however that the spacing S2 (see Figure 10) between teeth 265 and 266 and between teeth 266 and 267 is only 1/3) of the pitch P2 of the adjuster teeth 244. Operation of clutch 210 is similar to the operation of clutch 10.

Thus considering pawl mechanism 250 with the clutch in an unworn condition and engaged, pawl teeth 265, 266 and 267 he on appropriate flanks 244A.

During clutch disengagement the pawl teeth 265, 266 and 267 slide across corresponding flanks 244A of adjuster teeth 244. During the whole of the disengagement movement of the pivot ring the teeth 265,266 and 267 remain on their appropriate flank 244A.

When the clutch is engaged the pressure plate 13 moves towards the flywheel and the pawl 1 teeth slide relative to the corresponding flanks 244A on adjuster teeth 44 until the fully engaged position is achieved.

Once a predetermined amount of wear of the friction facings 216 has taken place the engaged position of the pivot ring 240 is sufficiently close to the flywheel for the pawl tooth 267, to slide past the corresponding flank 244A and engage with the adjacent edge 244B of the adjuster tooth, in other words the pawl tooth 267 engages behind the corresponding adjuster tooth. This effectively senses that a predetermined amount of wear has taken place.

During the next disengagement of the clutch the pivot ring is moved away from the flywheel under the influence of the torque straps but the pawl tooth 267 is unable to slide past the edge Spring steel bracket 251 comprises rivet portion 25 1 A joined to and substantially parallel with flat portion 25 1 B via a curved portion 25 1 C (which acts as a pawl bias means). Additiondy flat portion 25 IB has a pawl means support portion 25 ID bent at 90 degrees to it and a further tab portion 25 lE is bent at 90 degrees to the support portion 25 1D.

Rivet 219 passes through a hole 252 in rivet portion 25 1 A to secure the spring bracket 251 and end 214B of strap 214 to tM chitch cover 22 1. Curved portion 25 1 C allows flat portion 251B, support portion 251 D and tab. portion 251E to pivot as a unit to a limited degree relative to rivet portion 251 A (typically the line 251' where the curved portion 251 C meets the rivet portion 25 1A). Such pivotal movement is limited in the direction of arrow G2 of figure 10 by tab portion 25 1 E contacting end 214B of strap 214. Indeed when the bracket 251 is manufactured and assembled onto the clutch cover 221 tab portion 25 1 E is arranged to be pre-loaded into contact with end 214B of strap 214 by virtue of stresses in curved portion 25 1 C. Note that the typical pivot 25 1' of the bracket 251 is inclined (in this case at 90 degrees) to the axis 140' about which pivot ring 140 rotates.

Pawl means 260 is riveted via rivet 269 to spring bracket 251 to form the pawl mechanism 250.

Pawl means 260 carries out the function of rotating pivot ring 240 when adjustment of the clutch is required.

It can be advantageous to mount all the pawl teeth of the automatically adjusting clutch on one pawl mechanism since the tolerance loop (or tolerance stack up) between aU the pawl teeth in relation to the adjuster teeth 244 is greatly reduced.

18 of Figure 1 labeled 100 greater. In this third embodiment three adjuster means are provided spaced at 120 degree intervals from each other around the clutch cover.

All three adjuster means are identical and therefore only one will be described in detail.

The pawl mechanism 150 of each adjuster has an edge 180 which contacts a corresponding tab 181 of bracket 15 1 to limit'relative rotation of the pawl about axis 70' of pawl rivet 170.

Each pawl means 160 has only one arm 163 and only one pawl tooth 165.

The first part 13 0 of the pressure plate 11 3) is annular in shape.

On the axial side of first part 130 remote from the flywheel there are three axial screw threaded bores 134 which are equi-spaced circumferentially around the first part 130.

A second part of the pressure plate in the form of a pivot ring 140 is also annular Mi shape and has a pivot section 145 situated radially between an outer 185 and inner 186 plate portion. Three equi-spaced slots 187 are formed in the pivot ring 140 opposite the bores 134. Each slot extends in the circumferential direction and has an array of slot teeth 188 on the radial inner edge of the slot (see Figure 12).

Between each slot 187 and its corresponding bore 13)4 is an adjuster wheel 190 supported on the first part of the pressure plate 130. A threaded portion 191 of wheel 190 engages the adjacent threaded bore 134 of the first part 130. The adjuster wheel also includes a first toothed wheel 192 and a second toothed wheel 193. Each first toothed wheel 192 has a circumferential array of helical adjuster teeth 144 which are engaged by a corresponding'pawl tooth 165.

17 244B of its engaging adjuster tooth and therefore the pawl means 250 is rotated against the preload stresses of curved portion 25 1 C of bracket 25 1. Also at the same time the corresponding tab portion 25 lE disengages the corresponding end 214B of strap 214. Thus the pawl meansrotation provides a potential adjustment force.

When the clutch is fully disengaged the pivot ring 240 is no longer clamped between the annular mass 230 and the diaphragm spring 212 and is able to rotate about the' chitch axis relative to the first portion under the influence of the stressed curved portion 2 5 1 C (or pawl bias means) until the corresponding tab portion 25 lE re-engages with corresponding end 214B of strap 214.

The clutch is designed such that the amount by which the pivot ring 240 is caused to rotate by the pawl means 250 relative to the annular mass 230 produces an increase in effective thickness (T2 - see Figure 11) of the pressure plate 213 substantially equal to the amount of wear of the friction facings 216. Thus when the clutch is re-engaged following an adjustment, the pivot ring 240 and pivot section 245 is axially in its "unwom engaged" position.

Following a further pre-determined amount of wear, a further adjustment of the effective thickness of the pressure plate 213 takes place under the influence of pawl tooth 266.

The next adjustment takes place under the influence of pawl tooth 265. The adjustment sequence then starts again with pawl tooth 267.

Thus the pawl mechanism again provides automatic adjustment of clutch 2 10.

Figures 12 to 14 show a third embodiment of an automatically adjusting clutch 110 with features which perform substantially the same function as corresponding features M clutch 10 adjusting clutch engagement (direction M') or disencagement (direction Xl) and axis 170'is W = 11 not parallel but inclined to the axis 190' about which the wheel 190 rotates.

Figure 15 shows a fourth embodiment of an automaticafly adjusting clutch 3 10 in the engaged and unwom position. The clutch 3 10 includes a flywheel 3 11, a pawl means 3) 50 pivotafly mounted about axis 370' on a component axially fixed relative to the flywheel (in this case the clutch cover 3 2 1). The pawl means is biased in an anti clockwise direction when viewing figure 13. A driven plate 3 15 is situated between the flywheel and a two pail pressure plate 3) 13. Pressure plate 313 consists of annular mass 330 supporting a pivot ring 340 and the effective thickness of the pressure plate can be adjusted to compensate for wear in a manner similar to the automatically adjusting clutch 10.

Note however that the adjuster teeth 344 are parallel to the axis 340' of the pivot ring -3)40.

The pawl mechanism has a pawl tooth 365 that engages the array of adjuster teeth 344 and also has a foot 390 which engages the face 391 of the annular mass 330. Adjustment is effected in a manner similar to clutch 10 in that following a predetermined amount of wear of the driven plate facings the annular mass rotates the pawl means sufficiently far clockwise when viewing figure 15 so that the pawl tooth engages behind an edge of the adjuster tooth During subsequent disengagement of the clutch the pawl bias means (not shown) acts in an anti-clock-,vise direction on the pawl means and ultimately rotates the pawl tooth anticlockwise to move the wTay of adjuster teeth in the direction F3.

Figure 15 also shows the relative position of the pawl tooth and array of adjuster teeth with the unworn clutch engaged (E3) also shown is the relative positions of the pawl tooth and adjuster teeth with the clutch subsequently disengaged(D3). It should be noted that the relative direction of movement between the pawl means and the array of adjuster teeth during 19 Each second toothed wheel 193 has a circumferential array of teeth 193)A which engage corresponding slot teeth 188. Thus it is apparent that rotation of one adjuster wheel 190 about its own axis 190'will cause circumferential movement of the pivot ring 140 about the clutch axis which in turn will cause rotation of the other two adjuster wheels 190 about their respective axes. This ensures that the first part 130 of the pressure plate always remains parallel to the pivot ring 140.

Rotation of an adjuster wheel 190 about its axis 190'in the direction FLas a result of wear of the friction facings is effected by the associated pawl 160 engaging the adjuster teeth 144 in a manner similar to that in which rotation of pivot ring 40 of Figure 1 is effected by pawl 60 and adjuster teeth 44.

Note that the pawl teeth 165 of each adjuster can be in phase with each other in which case each pawl means will rotate its corresponding wheel simultaneously or the pawl teeth 165 of each adjuster could be out of phase in which case one pawl means will rotate its corresponding adjuster wheel which in turn wffi rotate the pivot ring which in turn will rotate the remaining two adjuster wheels.

Note also that it is possible to ensure permanent engagement of each pawl tooth 165 with a corresponding first toothed wheel 192 by making the pawl means 160 out of a non-resilient material and ensuring each pawl bias means 157 is axially resilient having regard to the axis of rotation of the pawl means, to allow each pawl means 160 to tilt on its corresponding pawl rivet 170.

Note also that the direction of movement (F1) of the adjuster teeth is substantially at 90 degrees to the direction of relative movement between the array and pawl means during a non 22 d) if a clutch contains a plurality of pawl teeth each pawl tooth can be in phase or out of phase with any other pawl tooth of the clutch., e) the adjuster teeth of an array can be straight cut i.e. the adjuster teeth are parallel with the axis about which the array rotates during adjustment or the adjuster teeth could be inclined to the said axis of the array for example helical teeth, f) adjustment of the pivot ring can take place in the direction of engine rotation relative to the first portion or contrary to the direction of engine rotation., g) some designs may be such that over the service life of the clutch not all the adjuster teeth are engaged by a pawl tooth. Thus such non- engaging teeth need not actually be formed for example not all 241 adjuster teeth of the embodiment of the invention shown in figure 1 need be formed onto the pivot ring 40, only those teeth engaged by and therefore local to the pawl means 60A, 60B and 60C are required, and h) it may still be advantacreous to form redundant adjuster teeth to aid assembly, for example if all 241 teeth of figure 1 are formed, the pivot ring 40 can be assembled against the first portion 30 in any of nine different ways corresponding to the nine corresponding undulations 32 and 47.

From the above description it is apparent that embodiments of the present invention are simple and cheap to produce. They can also be designed to utilize existing components from sirnilar sized non-adjusting clutches. In particular existing diaphragm springs and clutch covers designed for use in non-adjusting clutches can be used in embodiments of the present invention with no or minimal modifications. This has the significant advantage of being ble to use the existing (and very expensive) blanking tools and heat treatment dies when making the

21 engagement of the clutch during a non-adjusting operation is in the direction of arrow X3 and the equivalent relative direction of movement during a non adjusting disengagement of the clutch is in the direction of arrow XY.

This is because the pawl mechanism 350 rotates with every clutch engagement or disengagement (note that the pawl mechanism 50 only rotates during a disengagement when an adjustment is taking place, during all non adjusting clutcir actuation the pawl mechanism 50 does. not rotate).

Note that the direction F3 is substantially at 90 degrees to the direction Z3 (the direction of movement of the array of adjuster teeth during a non adjusting clutch engagement or disengagement operation). Also the direction F3 is inclined to the direction X3 and XY at an angle which is not 90 degrees (contrast this with the angle between direction F and directions X l and X V of the first embodiment described (see figure 6).

Furthermore the edges 344B of the adjuster teeth 344 are inclined at the acute angle Y31 to the directions X3 and XY.

It is apparent that for all automatically adjusting clutches described above and further automatically adjusting clutches in accordance with the present invention that: - a) there can be any number of adjuster means per clutch., b) if a clutch contains a plurality of adjuster means, the adjuster means can be interconnected to adjust Simultaneously, c) each pawl means can have any number of pawl teeth, 24

Claims (1)

1. CLAIEMS A2624GB

   1 An automatically adjusting clutch having a pressure plate which is held rotationally fast with a clutch cover via torque straps, the clutch also including at least one driven plate wear sensing means, the or each wear sensing means being attached to the clutch cover via fastening means which also attaches one of the torque straps to the cover.

   An automatically adjusting clutch according to claim 1 in which the at least one driven plate wear sensing means also effects adjustment of the clutch to compensate for wear.

   An automatically adjusting clutch according to claim 1 or claim 2 in which the wear sensing means comprises a pawl mechanism.

   4.

   5.

   An automatically adjusting clutch according to claim 3) in which the pawl mechanism comprises a pawl means mounted to the cover for limited pivotal movement about an axis.

   An automatically adjusting clutch according to claim 4 in which the pawl means engages an array of adjuster teeth which are disposed circumferentially around a component which is rotatable about an axis parafiel to the axis of rotation of the clutch.

   An automatically adjusting clutch according to claim 5 in which the pawl means moves relative to the array as the pressure plate moves axially relative to the 23 diaphragm springs and of being able to use the existing (and very expensive) press tools when making the clutch cover.

   26 13.

   An automatically adjusting clutch according to claim 9 in which the pawl means comprises an integral part of the bracket.

   14.

   An automatically adjusting clutch according to claim 14 when dependent on claim 8 in which the bias means comprises a resilient portion of the bracket.

   15.

   An automatically adjusting clutch according to any one of claims 4 to 14 in which the pawl means comprises at least one pawl arm.

   An automatically adjusting clutch according to claim 15 in which the or each pawl arm has at least one pawl tooth.

   17.

   An automatically adjusting clutch having a pressure plate which is held rotationally fast with a clutch cover via torque straps, the clutch also including at least one means for effecting adjustment of the clutch to compensate for wear, the or each adjustment effecting means being attached to the clutch cover via fastening means which also attaches one of the torque straps to the cover.

   is An automatically adjusting clutch according to any previous claim in which the fastening means is a rivet.

   flywheel, the pawl means and array being arranged so that if movement of the pressure plate towards the flywheel during clutch engagement exceeds a predetermined distance, indicating a predetermined amount of wear of the driven plate, the pawl means moves sufficiently over the array to engage behind a tooth of the array.

   7.

   An automatically adjustitig tlutch according to any one of claims 4 to 6 in which the pawl means pivots about an a)ds which is substantial] at 90 degrees to the axis y of rotation of the clutch.

   An automatically adjusting clutch according to any one of claims 4 to 7 in which the pawl mechanism further comprises a bias means for biasing the pawl means in a first direction of movement about the axis.

   An automatically adjusting clutch according to any of claims 3 to 7 in which the pawl mechanism comprises a bracket attached to the cover via the fastening means.

   10.

   An automatically adjusting clutch according to claim 9 in which the pawl means is pivotally mounted to the bracket.

   An automatically adjusting clutch according to claim 10 in which the pawl means is pivotally mounted to the bracket via a rivet.

   12.

   An automatically adjusting clutch according to claim 11 when dependent on claim 8 in which the bias means comprises a coil spring which surrounds part of the rivet, one end of the spring engaging the bracket, the other end of the spring engaging the pawl means.