Title of Invention

FRICTION CLUTCH EQUIPPED WITH WEAR TAKE-UP DEVICE

Abstract

Friction clutch equipped with wear take-up device having a reaction plate, a friction disc, carrying friction linings at its external periphery, the said clutch comprising a thrust plate, a cover intended to be fixed to the reaction plate, axially acting engagement means controlled by disengagement means, acting between on the one hand the cover and on the other hand the thrust plate by means of abutment means, the thrust plate being fixed with respect to rotation to the cover whilst being able to move axially with respect to it and being subjected to the action of elastic return means returning the thrust plate axially towards the cover, the said wear take-up device comprising ramp means having circumferentially disposed ramps placed axially between the abutment means and the thrust plate, the said ramps being adapted to cooperate with counter-ramp means, the engagement means having a diaphragm which bears on the cover at points situated radially towards the outside with respect to the abutment means, the clutch being of the pulled type characterized by the fact that there are provided stop means carried by the cover and adapted to limit the travel of the engagement means in the storage position of the clutch, close to their working position.

Full Text

The present invention relates to friction clutch equipped with wear take-up device. The present invention concerns a clutch mechanism for a friction clutch, in" particular "for a "motor vehicle, and relates more particularly to a clutch mechanism equipped with a device for compensating for wear due notably to wear on the friction linings, the said device, referred to hereinafter as a device for taking up wear, operating as the said friction linings wear. A conventional friction clutch generally has a reaction plate, optionally in two parts for forming a damping flywheel, fixed with respect to rotation to a first shaft, usually a driving shaft such as the crankshaft of the internal combustion engine, and supporting, through its external periphery, a cover to which at least one thrust plate is attached. The thrust plate is fixed with respect to rotation to the cover and reaction plate whilst being able to move axially under the force of the axially acting clutch engagement means and controlled by declutching means, generally having a metallic diaphragm bearing on the cover, whilst a friction disc, carrying friction linings at its external periphery, fixed with respect to rotation to a shaft, usually a driven shaft such as the input shaft of the gearbox, is interposed between the thrust plate and reaction plate so as to be clamped between them when the clutch is in the engagement position. The diaphragm controls the axial movement of the thrust plate when it is actuated by a clutch release bearing. During the service life of such a clutch, the friction linings as well as the counter-materials, thrust plate and reaction p}ate, wear, which causes a variation in the positions of the thrust plate and in the positions of the axially acting elastic means and clutch release bearing, resulting in a variation in the clamping force between the friction disc on the one hand and the thrust and reaction plates' on the other hand, because of the changes in the working conditions of the diaphragm, and the force needed to declutch is affected thereby. By providing such a clutch with a device for taking up wear, these drawbacks are avoided, the diaphragm, as well as the clutch release bearing, usually in constant abutment on the diaphragm, occupying the same position when the clutch is in the engagement position. A clutch mechanism for a friction clutch, in part.icular for a motor vehicle, has been proposed, notably in the French patent application PR-A-2 753 503.filed on 17 September 1996 under the number 96 11297, of the type having a reaction plate intended to be fixed with respect to rotation on a driving shaft, a friction disc, carrying friction linings; at its external periphery, intended to be fixed with respect to rotation to a driven shaft, the said mechanism comprising a thrust plate, a cover intended to be fixed to the reaction plate, clutch engagement means, acting axially and controlled by declutching means, acting between on the one hand the cover and on the other hand the thrust plate by means of abutment means, the thrust plate being fixed with respect to rotation to the cover whilst being able to move axially w:.th respect to it and being subjected to the action of elastic return means returning the thrust plate axially towards the cover, the said mechanism also including a device for taking up wear comprising ramp means having circumferentially disposed ramps, placed axially between the abutment means and the thrust plate, the said ramps being adapted to cooperate with counter-ramp means. Naturally, the clutch being equipped with a device for taking up wear, it is necessary, after it has fulfilled its function, to put it in its so-called zero position corresponding to linings in the new state, after changing the friction disc whose linings have been worn: means have already been provided so that this operation is easy to implement, as is for example described in the French patent application filed on 3 0 May 1997 under the number 97 06655. It is advantageous that this operation can also be carried out on the clutch mechanism alone, consisting of the cover, the clutch engagement means, the device for taking up wear and the thrust plate, constituting a subassembly, before mounting on the reaction plate or flywheel. Such an operation is difficult when the clutch engagement means, releasing when the mechanism is in this storage position, in some way axially jam the ramp means against the thrust plate, itself held, with respect to the cover, by the return means or other axial stops. The clutch mechanism being equipped with a device for taking up wear, the clutch engagement means occupy, as explained above, always almost the same operating position with respect to the cover. This is taken advantage of by the present invention in order to limit the travel of the clutch engagement means with respect to the cover. According to the invention, a clutch mechanism, for a friction clutch of the above type, is characterised by the fact that there are provided stop means carried by the cover and adapted to limit the travel of the clutch engagement means, in the storage position of the mechanism, close to their operating position. Thus, because of the presence of the device for taking up wear, it is certain that the clutch engagement and/or declutching means of the mechanism mounted on the reaction plate will not come into contact with the said stop means nor with any element forming part of the device for taking up wear other than the abutment means. This arrangement is particularly advantageous where the clutch is of the pulled type, the clutch engagement means including a. diaphragm. In the case of a clutch of the pulled type, in which the diaphragm bears on the cover at points situated radially towards the outside with respect to the abutment means, in the position of storage of the mechanism the diaphragm has a tendency to move away from the cover: up until now, in order to limit this distancing travel, it has been proposed, in a clutch mechanism not equipped with a device for taking up wear, to provide the thrust plate with stop mean.'!, placed at its external periphery, adapted to cooperate with the external face of a radial flange on the cover in the position of storage of the clutch mechanism: such an arrangenent has the drawback that the distancing travel must be sufficiently great to enable the thrust plate to move away from the cover in operation as the linings of the friction disc wear; this distancing travel, still too long in storage, does not facilitate the operation of mounting the mechanism on the reaction plate: in order to avoid having to use long screws for this fixing, storage shims are placed in line with the stop means, which requires fitting and removal operations. It has also been proposed to limit the distancing travel of the diaphragm by causing the latter to cooperate, in storage, with stop means carried by the cover: this is the case notably with certain variants described in the document FR-A-2 135 "637; here also the same drawbacks as above are found, the storage shims also being more difficult to fit. The present invention avoids the above drawbacks. Thus, preferably, the clutch engagement means consist of a diaphragm which bears on the cover at points situated radially towards the outside with respect to the abutment means, the clutch being of the pulled type. _5_ Advantageously, the stop means consist of lugs formed from the base of the cover and comprising an axial part which passes through holes in the diaphragm and whose free end is bent in a plane roughly perpendicular to the axis of the clutch in order to constitute a radial flange. According to a variant, the stop means consist o:: columns having a body which passes through holes in the diaphragm, a tail crimped on the base of the cover and a head on which a stop line is defined which faces the base of the cover and with which the diaphragm is adapted to cooperate in the storage position. According to another variant, the stop means consist of a ring placed between the thrust plate and the diaphragm and fixed to the base of the cover by rivets passing through holes in the diaphragm. Preferably, the diaphragm cooperates, in the storage position of the mechanism, directly with the stop means. Advantageously, the diaphragm cooperates, in the storage position of the mechanism, with the stop means by means of an elastic assistance washer. According to another variant, the stop means conssist of an elastic assistance washer placed axially between the thrust plate and the diaphragm and fixed to the base of the cover by rivets passing through holes in the diaphragm. When there is an elastic assistance washer, advantageously the elastic assistance washer has at its internal periphery extensions delimited by radial slots and intended to cooperate with the fingers of the diaphragm. Preferably, the elastic characteristics of the assistance washer are chosen so that, when the clutch is encaged, the clutch friction surface being new, the action exerted by the assistance washer is very small, or even nil. Advantageously, the elastic characteristics of the assistance washer are chosen so that, during the declutching operation, the action exerted by the assistance washer increases and then decreases as far as a given value, which may be very small or even nil, the clutch being disengaged. Another object of the invention is subassembly consisting of a cover and a diaphragm, in which the diaphragm is in abutment on the cover through its external periphery, a subassembly whose cover and diaphragm have the characteristics of the cover and diaphragm of the above mechanism. According to the present invention, there is provided friction clutch equipped with wear take-up device having a reaction plate, a friction disc, carrying friction linings at its external periphery, the said clutch comprising a thrust plate, a cover intended to be fixed to the reaction plate, axially acting engagement means controlled by disengagement means, acting between on the one hand the cover and on the other hand the thrust plate by means of abutment means, the thrust plate being fixed with respect to rotation to the cover whilst being able to move axially with respect to it and being subjected to the action of elastic return means returning the thrust plate axially towards the cover, the said wear take-up device comprising ramp means having circumferentially disposed ramps placed axially between the abutment means and the thrust plate, the said ramps being adapted to cooperate with counter-ramp means, the engagement means having a diaphragm which bears on the cover at points situated radially towards the outside with respect to the abutment means, the clutch being of the pulled type characterized by the fact that there are provided stop means carried by the cover and adapted to limit the travel of the engagement means in the storage position of the clutch, dose to "their working position. To give a better understanding of the object of the invention, a description will now be given, by way of purely illustrative and non-limitative example, of embodiments depicted in the accompanying drawings in which: Figure 1 is a partial view in section of a clutch mechanism according to the invention, equipped for a device for taking up wear in its position which corresponds to the engaged state of the clutch, with new linings; Figure 2 is a view in section of the clutch mechanism according to Figure 1 in its storage position; Figure 3 is a view similar to Figure 1 and corresponds to a variant; Figure 4 is a view in section along IV-IV in Figure 3 showing the stop means alone; Figure 5 is a view showing the mechanism of Figure 3 equipped with an assistance washer; - Figure 6 is a partial view in the direction of the arrow VI in Figure 5; - Figure 7 is a view in section of the clutch mechanism according to Figures 5 and 6 in its storage position; - Figure 8 is a view similar to Figure l and corresponds to another variant; - Figure 9 is a view showing the mechanism of Figure 8 equipped with an assistance washer; - Figure 10 is a view similar to Figure 1 and corresponds to yet another variant, the mechanism being equipped with an assistance washer,- - Figure 11 is a partial view in the direction of the arrow XI in Figure 10 Referring to Figures 1 to 4, a friction clutch mechanism can be seen, notably for a motor vehicle, which comprises a thrust plate 1 intended to cooperate with a friction disc 7, carrying at its external periphery friction linings 8, which itself cooperates with a reaction plate. The reaction plate, depicted schematically at 100 in Figure 1, is intended to be fixed with respect to rotation to a driving shaft, such as the crankshaft of the internal combustion engine. The friction disc 7 is fixed with respect to rotation to a driven shaft such as the input shaft of the gearbox. The thrust plate 1 is fixed with respect to rotation to a cover 2, here hollow in shape, by means of tangertial tongues 9 which, being elastic, constitute at the same time means of returning the thrust plate 1 towards the cover 2, here metallic, made from pressed sheet metal. This cover 2 has a base 12 and means for fixing it to the reaction plate, optionally divided in order to form a damping flywheel; the cover 2 is roughly in the form of a hollow dish and has at its external periphery a radial flange forming means of fixing the cover 2 to the reaction plates, the said flange being provided with holes for the passage of devices, such as screws, for fixing the cover to the reaction plate. The thrust plate 1, whilst being fixed with respect to rotation to the cover 2, is therefore movable axially with respect to the cover 2 under the action of the clutch engagement means, acting axially and controlled by declutching means, here a diaphragm 3 bearing on the cover 2, through the external periphery of its part 16 in the form of a Belleville washer, on a rod 6 placed at the internal periphery of the base 12 of the cover 2, the clutch being of the pulled type; the declutching operation is performed by acting on the end of the fingers 18 of the diaphragm 3 in the direction of the arrow F in Figure 1; the Belleville washer 16 of the diaphragm 3 is in contact with an abutment 14 described below. In order, when the clutch is engaged, to keep the axially acting elastic means 3 in a position independent of the wear on the linings 8 of the friction disc 7, and to a lesser extent the wear on the thrust 1 and reaction plates whose faces, referred to as friction faces, wear in contact with the linings 8 of the disc 7, a device for taking up wear 10 is provided. The device for taking up wear 10 comprises ramp means 11 disposed circumferentially; more precisely, these ramp means 11 consist of an annulus having circumferentially disposed ramps 15; the said annulus also has abutment zones 14 consisting of a rounded top edge centred on the axis of the clutch placed axially towards the outside with respect to the ramps 15. The thrust plate 1 has, here cast in one piece, on its face turned towards the base 12 of the cover 2, studs 4 distributed circumferentially at a distance from each other which corresponds to that which circumferentially separates two successive ramps 15, the studs 4 being intended each to cooperate with a ramp 15. The ramp means 11 are placed axially between the diaphragm 3 and the thrust plate 1 so that the studs 4 receive the ramps 15 and the diaphragm 3 cooperates with the abutment zones 14 which thus constitute the abutment means by meams of which the diaphragm 3 acts on the thrust plate l. The ramp means 11 have, at their external periphery, a cylindrical wall 17 parallel to the axis of the clutch cooperating with a cylindrical hollow 5 with the same axis which the thrust plate l has on its face opposite the base of the cover 2 so that the ramp means 11 are centred with respect to the thrust plate 1. The device for taking up wear 10 can be of any type; it will simply be indicated here that it can also comprise a ratchet wheel carried by a spindle which also carries a worm, the said spindle being carried by a support adapted to receive an elastic member in the general shape of a C, one end of which, in the shape of a T, carries at its end a control tongue adapted to cooperate with the teeth on the ratchet wheel. The thread and pitch of the worm are adapted to a set of teeth carried by a sheet-metal part bent in the general shape of a flattened Z and fixed by its ends to protrusions on the thrust plate 1. For more information, reference should be made for example to the aforementioned document FR-A-2 753 503, the content of which is deemed to be annexed to the present invention. According to the invention, the clutch mechanism includes stop means 20 for limiting, in storage, the travel of the diaphragm 3 with respect to the cover 2 close to its operating position; moreover, these stop means 20 make it possible to prevent any interference between the diaphragm 3 and here the ratchet wheel of the device for taking up wear 10 located radially below the ramp means 11. Here, these stop means 20 consist of cut-out bent: lugs formed from the base 12 of the cover 2. As,is known, the diaphragm 3 comprises a peripheral part 16 in the form of a Belleville washer, which cooperates with the abutments 6 and 14 and which is extended inwards by fingers 18 separated by radial slots which open out in holes 19 evenly distributed at the internal periphery of the peripheral part 16 of the diaphragm 3. The holes 19 are wider than the radial slots and form the ends thereof. The lugs 20 constituting the stop means are evenly distributed peripherally and can be three, four or more in number. The lugs comprise an axial part 21 which passes through holes 19 in the diaphragm 3, the free end of which is bent: in a plane roughly perpendicular to the axis of the clutch :.n order to constitute a radial return 22 directed here towards the axis of the clutch; it is with the face of the flange 22 which is turned towards the base 12 of the cover 2 'that the diaphragm 3 cooperates in the storage position of the mechan:.sm as shown in Figure 2; by limiting the travel of the diaphragm 3 in storage, the travel of the thrust plate 1 is lim;.ted; advantageously, the thrust plate 1 has, opposite the base 12 of the cover 2, radial recesses 31 in which the radial returns 22 of the lugs 20 can lie. It will also be appreciated that, by virtue of the invention, a subassembly comprising the cover 2 and diaphragm 3 has been produced, in the context of a mechanism of the pulled type, which facilitates handling as well as the operations of manufacturing the mechanism. In addition, by virtue of the stop means 20, the diaphragm 3 is centred with respect to the cover, which avoids having to provide special centring means for the diaphragm 3, such as for example axial pins located in the thrust plate l, as has been done up until now. According to the variant in Figure 3, the stop moans 20 consist of columns having a cylindrical body 23 passing through holes 19 in the diaphragm 3, a cylindrical tail 24, with a smaller diameter than the body 23, crimped to the base 12 of the cover 2, and a head 25, semi-cylindrical in shape and with a diameter greater than the body 23; on this head 25, on the side which faces the base 12 of the cover 2, there is defined a semi-circular stop line 26 for the diaphragm 3, slightly curved in shape. Figures 5 and 6 show the clutch mechanism of Figures 3 and 4 incorporating an elastic assistance washer 40 acting in parallel with the diaphragm 3, in order to assist, the declutching operation. The elastic assistance washer 40 bears on the one hand on an element which is fixed with respect to the cover 2 and on the other hand on the fingers 18 of the diaphragm 3 so that it is adapted to act in the direction of disengagement of the clutch. More precisely, the assistance washer 40 is dispcsed axially between the diaphragm 3 and thrust plate 1, being placed radially in line with the fingers 18 of the diaphragm 3, roughly radially inside the area delimited by the holes 19 in the diaphragm 3,here the assistance washer 40 comprises an external Belleville washer part 41 extended radially towards the axis along extensions 42 separated by radial slots; these extensions 42 extend approximately towards the free end of the fingers 18 of the diaphragm 3. Here, the external periphery of the Belleville washer part 41 of the assistance washer 40 is an abutment on the stop line 2 6 which faces the base 12 of the cover 2 and which is presented by the head 25 of the columns 20. The assistance washer 40 has elastic characteristics such that/ when the clutch is engaged and the linings 18 of the friction disc 7 are new, it does not generate any axial force on the fingers 18 of the diaphragm 3; the clamping force of the linings gripped between the reaction plate and the thrust plate 1 is that which is given by the peripheral part 16 of the diaphragm 3; when the fingers 18 of the diaphragm 3 0 are acted on in the direction of the arrow F, for disengaging the clutch, the assistance washer 40 acts on the fingers 18 of the diaphragm 3, in the direction of the arrow F, bearing on the cover 2 by means of the columns 20, thus relieving the force necessary for declutching. By virtue of the presence of the device for taking up wear 10, the positions of the diaphragm 3 and assistance washer 40, on clutch engagement and disengagement, are fixed, independent of the wear on the linings: the assistance for declutching supplied by the assistance washer 40 is therefore independent of this wear, just like the clamping force. Here, in the position of the storage of the mechanism, shown in Figure 7, it is by means of the assistance washer 40 that the stop means 20 limit the travel of the diaphragm 3. As can be seen, by virtue of the invention, an assistance washer 40 has been associated with a diaphragm and with a device for taking up wear without it being necessary to modify the cover 2; moreover, the said washer has been placed in a free space between the thrust plate l and the diaphragm 3 and its presence has not affected the axial dimension of the clutch mechanism. A3^ According to the variant in Figure 8, the stop nutans 20 comprise a circular ring 50, centred on the axis of the clutch mechanism and provided with a circular stop line 56 also centred on the said axis; extending in a transverse plane between the thrust plate 1 and diaphragm 3, the ring 50 is fixed to the base 12 of the cover 2 by doubly shouldered rivets 60, one shoulder being provided at each end of their body which passes through holes 19 in the diaphragm 3. Each of these ends is crimped, one on the base 12 of the cover 2, the other on the ring 50. Figure 9 shows a variant of the mechanism of Figure 8 equipped with an assistance washer 40, similar to that described with regard to Figures 5 to 7. According to the variant in Figures 10 and 11, the stop means 20 comprise an assistance washer 70; this assistsmce washer 70 has a peripheral part 71 extended towards the inside by radial extensions 72 which cooperate with the fingers ii\ of the diaphragm 3; advantageously, there are as many extensions 72 as there are fingers 18 on the diaphragm, this also being valid for the assistance washer 40 in Figures 5 t.o 7 and 9; at its external periphery, the assistance washer 70 has attachment areas 73 for fixing it to the base 12 of the cover 3 by means of rivets 60 similar to those of Figures 8 and 9. Thus, according to this variant, it is the assistance washer 70 itself which limits, in storage, the travel of the diaphragm. Naturally, the structures can be reversed; for example, the return 2 2 in Figure 1 can be directed radially outwards; the rod 6 can be formed directly by stamping in the cover. The cover is not necessarily hollow in shape. For example, the reaction plate can have, at its external periphery, an axially oriented annular skirt to which the cover is fixed. Likewise, a mechanism has been described in which the engagement and disengagement means are produced in a single piece, the diaphragm 3. It is possible to form the engagement means and the disengagement means independently: for example, the engagement means can consist of a Belleville Washer or helical springs, and the disengagement means of severs or a false diaphragm, that is to say a diaphragm whoso peripheral part in the form of a Belleville washer has no elasticity, because for example of the presence in this part of slots opening out to the outside. WE CLAIM 1. Friction clutch equipped with wear take-up device having a reaction plate (100), a friction disc (7), carrying friction linings (8) at its external periphery, the said clutch comprising a thrust plate (1), a cover (2) intended to be fixed to the reaction plate, axially acting engagement means (3) controlled by disengagement means, acting between on the one hand the cover (2) and on the other hand the thrust plate (1) by means of abutment means (14), the thrust plate (1) being fixed with respect to rotation to the cover (2) whilst being able to move axially with respect to it and being subjected to the action of elastic return means (9) returning the thrust plate (1) axially towards the cover (2), the said wear take-up device comprising ramp means (11) having circumferentially disposed ramps (15) placed axially between the abutment means (14) and the thrust plate (1), the said ramps (15) being adapted to cooperate with counter-ramp means (4), the engagement means having a diaphragm (3) which bears on the cover (2) at points (6) situated radially towards the outside with respect to the abutment means (14), the clutch being of the pulled type characterized by the fact that there are provided stop means (20) carried by the cover (2) and adapted to limit the travel of the engagement means (3) in the storage position of the clutch, close to their working position. 2. Friction clutch as claimed in claim 1, wherein the stop means consist of lugs formed from the base of the cover and comprising an axial part which passes through holes in the diaphragm and whose free end is in a plane roughly perpendicular to the axis of the clutch in order to constitute a radial flange. 3. Friction clutch as claimed in claim 1, wherein the stop means consist of columns having a body which passes through holes in the diaphragm, a tail crimped to the base of the cover and a head on which a stop line is defined which faces the base of the cover and with which the diaphragm is adapted to cooperate in the storage position. 4. Friction clutch as claimed in claim 1, wherein the stop means consist of a ring placed between the thrust plate and the diaphragm and fixed to the base of the cover by rivets passing through holes in the diaphragm. 5. Friction clutch as claimed in claim 1, wherein the diaphragm cooperates, in the storage position of the clutch, directly with the stop means. 6. Friction clutch as claimed in claim 1, wherein the diaphragm cooperates, in the storage position of the clutch, with the stop means by means of an elastic assistance washer. 7. Friction clutch as claimed in claim 6, wherein the stop means consist of an elastic assistance washer placed axially between the thrust plate and the diaphragm and fixed to the base of the cover by rivets passing through holes in the diaphragm. 8. Friction clutch as claimed in claim 7, wherein the elastic assistance washer has at its internal periphery extensions delimited by radial slots and intended to cooperate with the fingers of the diaphragm. 9. Friction clutch as claimed in claim 7 or 8, wherein the elastic characteristics of the assistance washer are chosen so that, when the clutch is engaged, the clutch friction surface being new, the action exerted by the assistance washer is very small, or even nil. 10. Friction clutch as claimed in claim 7 or 8, wherein the elastic characteristics of the assistance washer are chosen so that, during the declutching operation, action exerted by the assistance washer increases and then decreases to a given value, which is very small or even nil, the clutch being disengaged. 11. Friction clutch equipped with wear take-up device substantially as herein described with reference to the accompanying drawings.

Documents:

1479-del-1998-abstract.pdf

1479-del-1998-claims.pdf

1479-del-1998-complete specification (granted) as files.pdf

1479-del-1998-complete specification (granted).pdf

1479-del-1998-correspondence-others.pdf

1479-del-1998-correspondence-po.pdf

1479-del-1998-description (complete).pdf

1479-del-1998-drawings.pdf

1479-del-1998-form-1.pdf

1479-del-1998-form-13.pdf

1479-del-1998-form-19.pdf

1479-del-1998-form-2.pdf

1479-del-1998-form-3.pdf

1479-del-1998-form-6.pdf

1479-del-1998-gpa.pdf

1479-del-1998-petition-138.pdf