FR2783580A1 - Clutch mechanism for a motor vehicle with adjustment for wear of the friction pads - Google Patents

Abstract

The clutch mechanism contains an item for taking up wear of the clutch pads which comprises of a ring (330) with ramps (32) joined in rotation with axial mobility to an intermediate piece (310) containing teeth (31) on its periphery. A worm screw (36) engages with these teeth and is mounted in a housing, which is solid with the cover (2).

Description

The present invention relates to friction clutches, in particular for

  motor vehicles, and relates more particularly to the unitary assembly, which comprises such a clutch described for example in documents FR-A-2 242 892 and FR-A-2 420 690. Such a unitary assembly is called mechanism of clutch. Conventionally, a friction clutch comprises a reaction plate, possibly in two parts for

  formation in particular of a torsion damping flywheel.

  This reaction plate is integral in rotation with a first shaft, such as a driving shaft, namely the crankshaft of the internal combustion engine in the context of an application to

a motor vehicle.

  This reaction plate dorsally has a friction face and is integral in rotation with a pressure plate which can move axially relative to the plate.

  reaction also called flywheel.

  This pressure plate has a front face

friction.

  The friction linings of a friction disc are interposed between the pressure and reaction plates, plus

  precisely between the friction faces of these.

  These linings are integral with a support most often elastically deformable axially. This support, optionally split, is rigidly or elastically connected to a hub integral in rotation with a second shaft, such as a driven shaft, namely the input shaft of a movement transmission, for example, a box. speed, in the frame

  of an application to a motor vehicle.

  When the friction linings are clamped between the pressure and reaction plates (clutch engaged), the torque is transmitted from the drive shaft to the driven shaft via the friction disc. When the friction linings are not tightened between said plates (clutch disengaged), the driven shaft is not driven by the driving shaft. To do this, clutch means with axial action are provided and form a crew with declutching means provided to counteract at will the action of the clutch means bearing on a cover for action on the pressure plate, more precisely for action on support means carried by the pressure plate integral in rotation with the cover while being able to move axially relative to the latter, for example using a link with axially elastic tabs or using a connection of the tenon - mortise type of the radial lugs forming tenons - of the pressure plate being engaged in axial sliding in grooves - forming

mortises - from the cover.

  This cover has at its outer periphery, fixing means for fixing it to the reaction plate of

  detachable or non-detachable.

  The engagement means comprise at least one Belleville washer and the declutching means of the declutching levers for action on the engagement means. Most often these engagement and disengagement means belong to the same axially elastic part called a diaphragm. This diaphragm, of frustoconical shape in the free state, comprises a peripheral part in the shape of a Belleville washer, extended radially, towards the center by a central part fragmented in radial fingers by blind slots with widened bottoms for the formation of widened orifices the internal periphery of the Belleville washer constituting the engagement means with axial action, while the radial fingers form clutch release levers and therefore the

clutch release means.

  In documents FR-A-2 242 892 AND FR-A-2 420 690, the cover constitutes with the pressure plate, the elastic tongues and the diaphragm, a unitary assembly called the clutch mechanism, which is reported on the reaction plate. Of course, this clutch mechanism can constitute, with the friction disc and the reaction plate, a module which is attached in a unitary manner to the crankshaft of the vehicle engine or to a flange secured to the crankshaft, the reaction plate. then fixing on the flange

advantageously flexible.

  This mechanism is advantageously equipped with a device for taking up the wear of the friction linings and the friction faces of the pressure and reaction plates so that the diaphragm has a substantially constant position when the clutch is engaged, during the service life of

the friction clutch.

  This wear take-up device comprises ramps and counter-ramps acting between the pressure plate and the diaphragm support means or between the diaphragm and the cover. A trigger, sensitive to the state of wear of the friction linings, makes it possible to rotate the ramps in the event of wear so that the diaphragm always occupies the same position when the clutch is engaged under the action of the means

clutches (tight seals).

  The trigger comprises in one embodiment, a ratchet wheel and worm screw system, belonging to a

  cassette as described in document FR-A-2 753 503.

  More specifically, an elastic member with a control tongue cooperating with the teeth of the wheel is provided.

ratchet and a non-return ratchet.

  In the event of wear, the control tongue is operated by an actuator, in this case an appendage to the diaphragm, to rotate the ratchet wheel and compress a spring.

  catching up later allowed to relax. The anti ratchet

  return prevents the auger from turning in the opposite direction, especially when the spring relaxes. The worm comes into engagement with the teeth secured to a ring provided with ramps to cooperate with counter-ramps secured to the pressure plate. Thus, in the event of wear, the thickness of the pressure plate, composed of the pressure plate proper and the ring with ramps, is increased, the said ring carrying a boss

support for the engagement means.

  The ring therefore engages directly with the screw

unending.

  Such a provision is satisfactory, however, the Applicant has wondered whether it is not possible to delete

  the non-return pawl to simplify the elastic member.

  According to the invention, a clutch mechanism of the type indicated above is characterized in that the toothing belongs to an intermediate part linked in rotation to the ring with ramps by means of rotation connection means allowing an axial displacement of the ring with ramps relative to the intermediate piece.

  Thanks to the invention, the anti-ratchet can be eliminated

  return of the fact that the toothing is linked in rotation to the ramp ring by the intermediate piece and that the worm can rotate the toothing but not the reverse. The intermediate piece is generally axially fixed and consists of

example in a washer.

  In one embodiment, the elastic tongues for rotationally connecting the pressure plate with the cover are used to pinch a washer.

  intermediate between two tabs of the same set of tabs.

  To do this, the tongues have protrusions for pinching the intermediate washer. In one embodiment, the protuberances are produced at the end for fixing the tabs to the cover. The intermediate washer is thus axially fixed and is provided for example with notches in which penetrate the tabs of the ramp ring thus linked in rotation to the intermediate washer by cooperation of

shapes.

  Of course, the structures can be reversed, the washer having radial lugs penetrating into

  axial notches of the ramp ring.

  As a variant, the intermediate part with teeth is linked in rotation to the ring with ramps by elastically deformable tongues of the type of those intervening between the pressure plate and the cover. This eliminates the friction between the ramp ring and the intermediate piece, the tangentially oriented tongues, being coupled at one of their ends to the ramp ring and at their other end to

  the intermediate piece carrying the toothing.

  Other advantages will appear in the light of the

  description with reference to the appended drawings in which:

  - Figure 1 is a front view of a clutch mechanism according to the invention with local cutouts to show the diaphragm, the tangential tongues, the ramp means and the cassette of the wear take-up device; - Figure 2 is an enlarged view of the center of Figure 1; - Figure 3 is a sectional view along line A-A of Figure 1; - Figure 4 is a sectional view along line B-B of Figure 1; - Figures 5, 6 are views along the arrows respectively C and D of Figure 1; - Figure 7 is a sectional view along line E-E of Figure 1; - Figure 8 is a view along arrow F of line 1; - Figure 9 is an enlarged view of the lower part of Figure 3 to show a set of tabs; These figures represent a clutch mechanism forming a unitary assembly which has just been attached to a reaction plate, possibly divided to form a damping flywheel, with the insertion of a friction disc between the reaction plate and the plate. pressure that the

clutch mechanism.

  In the case of an application for a motor vehicle, the reaction plate is integral in rotation with the crankshaft of the internal combustion engine, forming a driving shaft, while the friction disc has at its outer periphery integral friction linings, for example by riveting or by a link devoid of fixing rivets, a support, optionally split, elastically deformable axially and rigidly or resiliently coupled to a hub integral in rotation, here with the input shaft of the gearbox ,

forming led tree.

  These are the mounting fittings which are therefore intended to be disengageably clamped between the pressure and reaction plates for transmission of the torque from the vehicle engine to the input shaft of the gearbox. To do this, axially acting engagement means are provided for clamping the friction linings between a friction face 11, which has the pressure plate 1 frontally, and a friction face, which the back has

  reaction plate, which can be carried by a flexible disc secured to the crankshaft.

  The engaging means form a crew with the declutching means provided to counteract at will the action of the engaging means which bear, on the one hand, on a cover 2 and, on the other hand, on bearing means 3, carried by the pressure plate 1, more precisely by the face

backbone of it.

  The declutching means comprise declutching levers on the internal ends of which acts a declutching stop controlled manually, mechanically or hydraulically, or semi-automatically or automatically. The stop can therefore be operated by an actuator with an electric motor controlled according to predetermined programs by a computer receiving information in particular on the speeds of rotation of the driving and driven shafts and on the intention of the driver to change gears. The actuator can be hydraulically or mechanically connected to the clutch release bearing. Thus, the clutch release bearing can belong to a hydraulic receiver of the concentric type crossed by the input shaft of the gearbox and connected to a hydraulic transmitter operated by

the actuator or manually.

  In the figures, the engagement and disengagement means

  belong to the same part called diaphragm 4.

  This diaphragm is frustoconical in the free state and has a characteristic curve (force exerted as a function of its deflection) of sinusoidal shape. Thus, starting from the origin, the characteristic curve increases to a

  maximum then decreases to a minimum to grow again.

  In the clutch engaged position, the diaphragm occupies a position in the decreasing part of its characteristic curve, at

neighborhood of its maximum.

  The same characteristic curve is obtained with a

Belleville washer.

  For the record, it will be noted that the diaphragm 4 comprises an external peripheral part in the form of a Belleville washer 41 constituting the engagement means. This peripheral part is extended radially towards the center by a central part

  fragmented into radial fingers 42, by blind slots 43.

  The fingers 42 form release levers, while the slots 43 open at their inner periphery into the central opening of the diaphragm 4 and at their outer periphery in enlarged orifices 44 forming the blind bottoms

  slots 43. These orifices 44 here have a rectangular shape.

  In these figures, the clutch mechanism therefore comprises unitarily a set of annular parts, namely, a pressure plate 1, a cover 2 and a diaphragm 4, bearing, on the one hand, on the cover 2, and, on the other hand, on the support means 3 for clamping the friction linings between the friction faces of the plates

pressure 1 and reaction.

  The pressure plate 1, made of moldable material, here in cast iron, like the reaction plate, is linked in rotation to the cover 2 while being able to move axially relative to the latter, here using tongues 10, elastically axially deformable. The tongues 10 are here of tangential orientation and are fixed, here, by riveting, at one of their ends to the cover and at the other of their ends to the pressure plate 1, more precisely, each to a tab 12

  of the plate 1 projecting radially outwards.

  As a variant, the lugs 12, forming tenons, are engaged, in axial grooves, forming mortises of the

cover 2.

  The tongues 10 constitute means for returning the pressure plate. More specifically, the cover 2 has, on the one hand, a bottom 21 with a central hole and transverse orientation and, on the other hand, fixing means 22 of the

  cover 2 to the reaction plate.

  In the figures shown, the cover has the shape of a hollow plate and has a radial end flange 22 directed radially in the direction opposite to the axis of axial symmetry X-X presented by the clutch mechanism. This rim 22 is connected by an annular skirt 23 of axial orientation, at the bottom 21. The skirt 23 is stepped in diameter and open at the level of the tongues 10, which resemble elastically the plate of

  pressure towards the bottom of the cover 2.

  The rim 22 constitutes the fixing means and is divided into areas 28, 27 axially offset for fixing

  tabs 10 and for fixing to the reaction plate.

  The fixing areas 27 to the reaction plate are perforated for the passage of fixing members to the reaction plate, here, screws. The diaphragm 4 is supported at the external periphery of its Belleville washer 41 on the support means 3, while the internal periphery of its Belleville washer 41 is pivotally mounted between two opposite supports, respectively a secondary support 25 carried by legs

  fixing 26 and a primary support 24, carried by the bottom 21.

  The fixing lugs 26 are produced by cutting and folding the internal periphery of the bottom 21 of the cover 2, here

stamped sheet metal.

  The legs 26 are distributed circumferentially from

  regularly and are axially oriented.

  The legs 26 pass axially through the enlarged orifices 44 of the diaphragm 4 and have, beyond the diaphragm 4, a free end folded radially outwards, that is to say radially in the direction opposite to the axis of the assembly for forming a wedging bend for a ring crown 125, of frustoconical shape, having at its external periphery a rounded edge 25 constituting the secondary support. The primary support 24 has the form of an annular ring formed here by stamping the

  bottom 21 of cover 2. This ring 24 is here fragmented.

  As a variant, this rod 24 is attached to the cover 2. The internal periphery of the Belleville washer 41 of the diaphragm is interposed axially between these supports 24, 25 facing each other. In the engaged clutch position, the diaphragm 4 is supported on the primary support 24 and on the

  support means 3 of the pressure plate.

  By acting by pushing on the internal ends of the fingers 42 of the diaphragm 4 using a declutching stop (not shown), the diaphragm 4 is tilted, which then takes support on the secondary support 25, to cancel the load it exerts on the pressure plate 1 via the support means 3; the tabs 10 recalling the pressure plate towards the bottom 21 of the cover 2 to release the linings from

  friction and disengage the clutch.

  Of course, the secondary support can be discontinuous by being formed by the free ends of the fixing lugs

  26 conformed accordingly in the aforementioned document FR-A-2 242 892.

  The fixing lugs 26 alternate circumferentially here with stop lugs 5, of transverse orientation. These stop tabs come from a single piece of the bottom 21 of the cover by cutting and extend to the internal periphery of the bottom 21 of the cover 2, which has internally thus

a jagged shape.

  For more details, reference will be made to document FR-A-2 242 892 showing the fixing lugs 26 before their folding and the stop lugs 5, which are wider.

  circumferentially than the fixing lugs 26.

  The stop tabs 5 here cover a slot 43

  separating two consecutive fingers 42.

  Of course, this all depends on the size of the cover. The stop tabs 5 therefore form a stop for at least two fingers 42, forming release levers. These stop tabs 5 have here a trapezoidal shape. The internal diameter of the stop tabs 5 is less than the internal diameter of the fixing tabs 26 after folding. The legs 5, 26 extend radially below the primary support 24 of annular shape. A notch 6 separates two consecutive stop tabs 5. A fixing tab 26 is located in the middle of the notch 6 to penetrate axially into an orifice

enlarged 44 of diaphragm 4.

  The internal periphery of the stop tabs 5 extends radially below the enlarged orifices 44. The fixing tabs 26 constitute fixing means for tilting or pivoting mounting of the diaphragm 4 on the cover. As a variant, the fixing lugs can be omitted and the cover may only include stop lugs as described in document FR-A-2 420 690. In this case, the fixing lugs are perforated for mounting a part annular in the form of a comb, balusters with profiled head forming a secondary support, etc. All embodiments, such as staples, columns carrying two support rods etc., described in this document FR-A-2 420 690, to which reference will be made for more details, are conceivable. The stop tabs 5, in the form of a tongue, can therefore be fixing tabs. As a variant, the ends of the legs are cut

  fixing 26 to keep only the axial part thereof

  this. The tabs 26 then form centering tabs and the

  stop tabs 5, fixing tabs as mentioned above.

  Alternatively, the cover does not have stop tabs, some of which form fixing tabs. As a variant, the fixing lugs 26 can carry a false diaphragm, that is to say a part whose central part is fragmented into fingers like that of a diaphragm, while the annular peripheral part is devoid of elasticity or has low elasticity. For example, this annular peripheral part, in the form of a washer, is provided with blind radial slots opening radially at the external periphery of the false diaphragm and of the annular part.

in the shape of a washer.

  The washer of the false diaphragm is therefore globally

  flat in the free state as well as the false diaphragm.

  A Belleville washer then takes support at its external periphery on the cover and at its internal periphery on the peripheral washer of the false diaphragm. Such an exemplary embodiment is described in the document

  DE-A-4 326 501 to which reference is made for further details.

  Of course, in the light of this document, it can be seen that the false diaphragm can be replaced by a plurality of individual release levers pivotally or pivotally mounted on the cover by means of the fixing means carried by the cover, with intervention of two Belleville washers mounted in series to form clutching means. In all cases, the cover 2 carries clutch release levers 42 pivotally or tiltably mounted on the cover 2 and the engagement means can comprise two Belleville washers mounted in series as in document DE-A-4 326 501 or a diaphragm mounted in series with an assistance washer as described in document FR-A-9 711 058 of September 5, 1997, which also discloses a ratchet wear take-up device - worm and toothing, of the type from that of the embodiment of the figure

1 of the present invention.

  Many clutches with a cover with stop lugs, possibly forming fixing lugs, are currently produced. Here, we take advantage of this type of cover to insert a shim between the stop lugs and the release levers in order to be able to deliver to the car manufacturer or garage owner, a new or reconditioned clutch mechanism in a delivery position in which the pressure plate is closer to the bottom 21 of the cover 2, than it is in the storage position when the release levers are in

support against the stop lugs.

  More specifically, a support piece 8 carries at its outer periphery wedging tabs 7 projecting radially outward. The support piece 8 is in contact with at least a plurality of the release levers 42, while the timing lugs 7 are in contact with the face of the stop lugs 5 facing the release levers 42 so that the release lugs wedging 7 and the support piece 8 are inserted axially between the release levers 42 and the lugs

  stops 5 by a bayonet type mounting.

  In the figures, the support piece 8 has an annular shape and has means 9 for engaging with a

  tool for rotating the support piece.

  These means 9 here consist of holes. The ring 8 forming the support piece, extends radially below the stop tabs 5 and radially above the internal periphery of the fingers 42 of the diaphragm, in the vicinity of said

internal periphery.

  The ring is here closed by being in contact with all the fingers of the diaphragm 4. The ring 8 has a great height so that it constitutes a circular plate open centrally. Thus, the tabs 8 are each initially introduced into a notch 6 separating two consecutive stop tabs 5. By pressing the ring 8 centrally, the fingers of the diaphragm 4 are moved. Then, using a tool penetrating the holes 9, the ring 8 is rotated to bring the wedging tabs 7 under the tabs stop 5, afterwards, the load exerted on the ring 8 is released. The wedging tabs 7 are here circumferentially narrower than the

  stop lugs 5 of trapezoidal shape.

  More specifically, the wedging tabs 7 here have a generally rectangular shape with rounded edges. The circumferential length of the lug 7, which is longer circumferentially than it is high, is generally equal to the circumferential length of the internal periphery of the abutment lug 5. The lugs 7 extend radially below the fixing lugs 26. As a variant, legs 7 may have

  another shape, for example trapezoidal, triangular, semi-

circular or square.

  The tool for rotating the ring 8 has

  pawns engaged in holes 9.

  Of course, the ring 8 can be opened and thus not come into contact with all the fingers 42 of the diaphragm. I1

  is, in this case, in the form of a circular hanger.

  The number of timing lugs 7 depends on the applications. Here, a setting tab 7 is provided by stop tab. Of course, the number of timing lugs 7 can be

  less than the number of stop lugs 5.

  There are at least two wedging tabs in position

diametrically opposite.

  Of course, the holes 9 can be replaced by notches or tabs formed on the internal periphery of

the ring 8.

  In all the figures, the central part of the bottom 21 of the cover has the same shape and we see an arrow symbolizing

  the direction of rotation of the ring 8 during its disassembly.

  The ring 8 is here in one piece with the legs 7

and is in pressed sheet metal.

  This ring can be provided with a coating with a low coefficient of friction at the level of its portion intended to come into contact with the fingers 42 and at the level of the face.

  outer of the legs 7 turned in the opposite direction of the diaphragm.

  This arrangement facilitates the rotation of the workpiece.

support 8.

  Of course, the ring 8 can be made of another material, for example a composite material reinforced with fibers or

  aluminum base. It can therefore be made of moldable material.

  Thanks to the shim, the screws for fixing the cover 2 to the reaction plate can be shorter and the tongues are protected before fixing the clutch mechanism to the reaction plate. The support piece 8 with its tabs 7 constitutes a tool for mounting the clutch mechanism on the reaction plate, which is removed after fixing the cover on said reaction plate. The reverse is possible so that this can constitute a disassembly tool allowing the friction linings to be lifted off from the pressure plate 1. Here, the wedge makes it possible to provide the parts of a wear take-up device in the delivery position. so

than the tabs 10.

  More specifically, in Figures 1 to 8, the ring 8 with its one-piece lugs allows the mounting of a cassette 30 belonging to a wear take-up device making it possible, in service, to compensate for the wear due mainly to the linings of friction of the friction disc. The cassette 30 is mounted on the cover 2 before fixing the pressure plate 1 to the cover. More precisely, the diaphragm 4 is first fixed on the cover 1 using the fixing lugs 26 in the aforementioned manner, the diaphragm 4 being mounted tilting between the two supports 24, 25. Then, the aforementioned mounting is carried out. ring 8 with its tabs 7 between the stop tabs 5 and the internal periphery of the fingers 42 of the diaphragm 4. The diaphragm then occupies a flat position corresponding to that which it occupies once the clutch mechanism is mounted on the cover 2. In this position, the clutch is engaged. In FIG. 7, the reaction plate is shown schematically at 100 and at 101 the friction disc, more

  precisely the friction linings of it.

  The wear take-up device maintains the diaphragm in this position, which corresponds to the clutch engaged new position. Then we fix the cassette 30 and we

  performs a pre-balancing operation.

  Then we approach the pressure plate 1 carrying here ramp means 32 and therefore of variable thickness so

described below.

  Then, the pressure plate 1 is mounted on the cover 2. More precisely, the plate 1 being equipped with the tongues 10, the other ends of the tongues 10 are fixed

on cover 2.

  Finally, we proceed with a balancing operation. Here, the cassette 30 is mounted in a housing 20 formed in excess thickness, here by stamping, in the cover 2, at its fixing flange 22. The housing 20 affects the flange 22 as well as the skirt 23 of the raised plate

thus at the level of the housings 20.

  The axial bottom of the housing 20 is formed by a transverse region 123 of the skirt 23 at the bottom 21 of the cover. A window 121 is formed in this zone 123 parallel to the bottom 21 while being offset axially in the direction of the rim 22 by

relative to the merits 21.

  The number of tabs 10 depends on the applications.

  Here, three sets of tabs 10, superimposed, are provided as well as three housings 20. The housings 20 and the tongues 10 are distributed circumferentially in a regular manner and this

alternately.

  Only one of the housings 20 has a window 121, namely the one used to house the cassette 30. Each set of

  tab 10 has at least two overlapping tabs 10.

  Here, three tongues 10, elastically deformable axially,

  are provided by set of tabs 10.

  The cassette 30, described below, creates an imbalance. For this reason, a pre-balancing is carried out before mounting the pressure plate 1, using pre-balancing rivets 201 mounted on the axial bottoms 123 without holes in the housings 20. Three rivets 201 are provided per housing 20, not allocated to the housing of the cassette. Another pre-balancing rivet 201 'is provided diametrically opposite the cassette 30. This rivet 201' is used for fixing a set of tabs 10 to the cover 10, as visible in FIG. 5. The pressure plate 1 is locally notched at the rivet

  201 '. All this is because the pressure plate is notched at the level of the cassette 30 to create a clearance.

  Finally, we place balancing rivets 202 at

  desired locations to balance the clutch mechanism.

  The rim 22 has for this purpose, in advance, balancing holes 47 for mounting the balancing rivet or rivets 202. To do this, many holes 47 must

  be provided to place the rivets 202.

  The flange 22 also has, on the one hand, fixing holes 29, for passage of the fixing members - such as screws or rivets - from the flange 22 to the reaction plate and, on the other hand, centering holes 48 for the passage of pawns

  centering device 148 (FIG. 7) carried by the cover.

  Openings 129 are made in the skirt 23, at the level of the fixing holes 29 for the passage here of the heads

  screws for fixing the cover 2 to the reaction plate.

  The openings 129 have a non-symmetrical shape. More specifically, we see in dotted lines, in FIG. 1, the size of a head of a fixing screw and of a balancing rivet 202. The fixing holes 29 and balancing 47 are adjacent to the one of the other. A pair of holes 29, 47 is provided by opening 129, thereby increasing the bearing surface

  rim 22 at this level for the heads of the fixing screws.

  The opening 129 is therefore elongated circumferentially and is deeper at the level of the hole 29; each of the holes 29, 47 being located at the circumferential end of an opening 129. Each balancing rivet 202 is fixed, like the fixing screws, at the level of an enlarged area 122 of the flange 22,

  formed by opening 129.

  The rivet 202 does not project beyond the zone 122, while the fixing screw heads project beyond the zones 122. Additional openings 203 are provided in the

  flange 22 above the housings 20.

  The flange 22 thus comprises three fixing areas 27 for contact with the reaction plate 100, here slightly of hollow form as visible in FIG. 7. These areas 27 (figure) alternate circumferentially with the areas 28, offset axially with respect to the areas 27 towards the bottom 21 of the cover 2 for fixing, here by riveting, of the tongues 10, to the cover. The skirt 23 is therefore open at this level, which allows the passage of fixing lugs 12, which has the pressure plate 1, projecting radially at its outer periphery. The pads 27 used for fixing the cover 2 are longer than the pads 28 for fixing the tabs connected continuously to the pads 27, to form a

awning (Figure 5).

  The beaches 27 are affected centrally by housings 20 while being narrower at this location. Each end of a range 27 is assigned an enlarged area 122 and

of an opening 129.

  The holes 29, 47 are therefore arranged, as well as the zones 122, on either side of a housing 20 at the ends

of a zone 122.

  This helps to balance the clutch mechanism. This is all the more so as, in FIG. 3, the pressure plate is notched to create a clearance for the cassette 30. This cassette 30 comprises a support 34 in the shape of a U with a core extending in contact with the deformation of the skirt 23 forming the top of the housing 20 and two wings are perforated by the passage of an axis 35, integral with an endless screw 36, integral with a ratchet wheel 37, interposed between the two wings of the support 34. The screw 36 is adjacent to one of the wings, while a helical catching spring

  38 is interposed between the ratchet wheel and the other wing.

  The axis 35 is attached to the inside of the screw 36 and

  the wheel 37, for example by force fitting.

  An elastic member 39 is mounted in contact with the internal face of the core of the support and the screw 36 and between the other wing

  of the support and the spring 38 (figure 8).

  The elastic member 39, thinner than the support 34 and metallic, has an oblique rim extended by a return carrying a control tongue 390 cooperating with the teeth of the ratchet wheel 37, and with an actuator 410 formed by an appendage external of the Belleville washer 41 of the diaphragm. The return carrying the control tab to a non-shaped

  symmetrical because the axis 35 is inclined.

  The support 34 comprises three fixing lugs 34 ', for its fixing by riveting respectively to the flange 22 and to

zone 123 and therefore to the cover.

  The worm 36 is disposed tangentially with respect to a toothing 31 extending radially outward in the opposite direction from the axis X-X of axial symmetry of the clutch mechanism and the clutch. The teeth 31 according to the invention belong to an intermediate piece 310, here

in the shape of a washer.

  The intermediate piece here is generally axially fixed. More precisely, each set of tongues 10 comprises at least two tongues each provided with a protuberance 10a directed generally radially inwards. The protrusions 10a have a generally annular end. The washer 310 is pinched axially between two protrusions 10a as best seen in FIG. 9, so that it is globally axially fixed because the loa protuberances slightly deform axially taking into account their low

radial height.

  The protrusions 10a are located at the end of

  fixing the axially elastic tabs 10 to the cover.

  Here, the tabs 10 are not identical in terms of their attachment to the cover. The intermediate tongue of each set of tongues 10 is devoid of protuberance and consists of a conventional tongue. The two other end tongues each have a protuberance 10a locally deformed to come to bear on the relevant side face of the intermediate washer 310, thus interposed clamping between the two protrusions 10a, one of which is deep-drawn.

  deeply than the other. The washer 310 is metallic.

  The washer 310 is linked in rotation according to the invention to a ring 330, here metallic. The ring 330 is a stamped sheet and has an annular rim of axial orientation 33, which here is linked in rotation by a link 340, 350

  in cooperation of shapes with the intermediate washer 310.

  This link 340, 350 authorizes an axial displacement of the ring 330 relative to the washer 310 coming into engagement by

  its teeth 31 with the worm screw 36.

  The connection by cooperation of forms is of the mortise tenon type. The washer 310 has here at its internal periphery three mortises in the form of notches 340 open radially inwards. The teeth 31 are formed at the periphery

  of the washer 310 thanks to a recess in the latter

ci (figure 2).

  The ring 330 has a rim 33 in the form of a comb with three legs of axial orientation 350 passing through the notches 340 and this with a circumferential mounting clearance. The intermediate washer 310 therefore meshes with the ring 330. Other type of meshing means can be provided. For example, the washer may have at its internal periphery a toothing meshing with a toothing formed at the external periphery of the rim 33. Each toothing may consist

for example in grooves.

  The ring 330 generally in section has the shape of a U, the outer wing of which is constituted by the flange 33 with legs 350 and the inner wing is intended to be centered by the internal periphery of studs 13 projecting axially and coming from pressure plate molding. The wings of the ring 330 are of axial orientation, the transverse bottom of the ring bearing

the support means 3 and ramps.

  More specifically, the ring is in intimate contact via its internal periphery with the external periphery of an increased thickness fragmented in studs 13, which the pressure plate has dorsally projecting axially. The rim 33 is connected to a fragmented annular boss. This boss constitutes the support means 3 for the external periphery of the Belleville washer.

41 of the diaphragm.

  Radially, below the boss 3, ramps 32 are provided to cooperate with the transverse end face,

  advantageously chamfered, studs 13 forming counter-ramps.

  Thus, in the event of wear, the diaphragm acts by its external actuator 410 on the control tongue 390 to rotate the ratchet wheel during the re-engagement operation in order to arm the spring 38, the connection 340, 350 preventing an opposite rotation of the wheel 37 and therefore of the screw 36, which can cause the toothing 31 but not the reverse. When the spring 38 is sufficiently armed, the screw 36 can rotate the toothing 31 to rotate the ramps 32 in contact with the studs 13, in order to increase the thickness of the pressure plate to compensate for the wear of the disc linings. friction so that

  the diaphragm occupies the same position.

  For more details, reference is made to application FR-A-9 611 397 of September 17, 1995, the content of which is considered to be annexed to the present invention. However, it will be noted that during the clutch and disengage operations, the ring 330 can move axially, with the pressure plate, relative to the washer 310 movable in rotation under the action of the screw 36. No friction does not occur between the screw 36 and the toothing 31 during these movements of the ring 330 since the washer 310 is generally axially fixed, here relative to the cover thanks to the protuberances. Thus, this does not disturb the wear take-up operation. The presence of a

  non-return ratchet is no longer necessary.

  The wedge 7, 8 therefore prevents deterioration of the cassette 30, more precisely of its elastic member 39 and of

its control tab.

  It will be noted that the fingers 42 have an internal end 45, offset axially relative to the zone

  rooting 46 of the fingers 42 to the Belleville washer 41.

  This zone 46 is in the plane of the washer 41 and has the orifices 44. It is connected by an oblique section 146 to the internal end 45 offset axially in the opposite direction

from the bottom 21 of the cover.

  The ring 8 has at its internal periphery a bead 85 directed axially in the direction opposite to the bottom 21

  cover 2 for local contact with the internal end 45.

  The legs 7 are in the plane of the ring 8.

* Thus, the tabs 7 bear against the internal face, directed towards the fingers 42, the stop tabs 5 and the bead 85 is in contact with the external face of the end

internal 45 of the diaphragm.

  The wedge 7, 8 therefore does not protrude axially with respect to the bottom 21 of the cover and the pressure plate is retracted, so that the clutch mechanism is can

bulky axially.

  After fixing the cover 2 by screwing to the reaction plate 10, the internal periphery of the ring 8 is pressed, as if to disengage, and the ring is turned according to the arrow of the

  Figure 1 to dismantle the wedge 7, 8.

  The pressure plate 1 therefore carries the hollow ring 31, 32, 33, 3 - forming ramp means - and is of variable thickness between its friction faces 11 and the support means 3

  to compensate for wear of friction linings.

  In all cases, the wedging tabs 7 are axially offset with respect to the internal periphery of the workpiece.

  support 8, formed by the rim 81 or the bead 85.

  Of course, the ring 8 can be equipped with gripping means for its rotation using a tool in order to bring

  the lugs under the stop lugs.

  The ring 8 can, like a control button, be provided with a protruding bar in the direction opposite to the

  diaphragm. The means 9 can therefore consist of projections.

  Generally, the circumferential length of a wedging tab 7 is less than the circumferential length between two consecutive stop tabs 5 so that the tabs 7 can be introduced into the notches 6 so

to assemble the bayonet.

  Openings can be made between two consecutive fingers 42 forming release levers for passage of one or more tools allowing access to screws fixing the reaction plate to the crankshaft of the vehicle engine. In this case, the holes 9 in FIGS. 1 to 8 are opposite said openings for dismantling the reaction plate fixed directly or indirectly, for example via

  a flange or a mass, to the crankshaft.

  As mentioned above, the declutching means can comprise one or more Belleville washers mounted in series, the declutching means can be distinct from the declutching means.

  The tongues 10 can be of radial orientation.

  In all cases, the tongues constitute means for rotating the pressure plate to the cover while allowing axial movement of the pressure plate by

report to the cover.

  The stop tabs, directed radially inward, that is to say towards the axis X-X can also be fixing tabs; The timing lugs 7 then passing under the fixing means carried by the stop lugs

during bayonet mounting.

  The axial offset of the timing lugs relative to the internal periphery of the support piece facilitates bayonet mounting and creates a clearance between the timing lugs and the release levers. In addition, this avoids deformation of the crown ring 125, or in general of the support

secondary 25.

  The declutching levers 42 are, in all cases, in contact with the clutching means in direct support with the support means 3 or in indirect support on the support means 3 via the declutching levers. The declutching means act at will on the clutching means for

thwart the action of these.

  Alternatively, the engagement means may consist of a plurality of coil springs bearing on a false

diaphragm and on the cover.

  Of course, the wedging tabs 7 can be attached to the fixing on the support piece, for example by riveting, welding, etc. As a variant, the connection in rotation between the intermediate piece and the ring 330 is produced by tangential tongues coupled at one of their ends to the ring

  330 and at their other end, to the intermediate piece.

  The tongues allow an axial displacement of the ring relative to the intermediate piece advantageously in the form of a washer. The friction between the ring 330 and the

  intermediate piece are thus eliminated.

  Of course, the intermediate piece can be made axially fixed by protrusions distinct from the tongues 10.This piece is axially fixed relative to the cover in

  being arranged therein.

  This part is centered by the pressure plate.

  In all cases, a strong pinching of the drive part is avoided so that it can rotate. Note that the pressure plate centers the intermediate piece. The notches in the intermediate piece can be closed. The teeth 31 can be formed directly at the outer periphery of the intermediate piece, knowing that in

  the figures the teeth are formed in the bottom of a trapezoidal notch formed on the outer periphery of the intermediate piece.

Claims (10)

  1. Clutch mechanism, in particular for a motor vehicle, comprising a cover (2) provided with a bottom (21) of transverse orientation, perforated centrally, a pressure plate (1) having a friction face (11) frontally for cooperation with a friction disc (101) provided with friction linings and dorsally supporting means (3), means (10) for rotationally connecting the pressure plate (1) to the cover (2) while allowing axial movement of the pressure plate (1) relative to the cover (2), clutch means (41) bearing on the cover (2) for action on the support means (3), clutch release levers ( 42) pivotally mounted on the cover (2) for action on the engagement means, and a device for taking up wear on the linings of the friction disc (101), in which the wear taking-up device comprises an actuator ( 410) secured to the engagement means (41), an actuating tongue (390) intended to be operated by the actuator (410) and to drive a worm (36) carried by the cover (2), said fine screw (36) cooperating with a toothing (31) associated with a ring (330) to ramps (32) cooperating with counter-ramps (13) carried by the pressure plate (1), characterized in that the teeth (31) belong to an intermediate piece (310) linked in rotation to the ring (330) with ramps (32) via a link (340, 350) allowing axial movement of the ring (330) with ramp (32)   relative to the intermediate piece (340).   2. Mechanism according to claim 1, characterized in that the intermediate piece (310) is arranged in the   cover (2) generally axially fixed.   3. Mechanism according to claim 2, characterized in that the intermediate piece (310) is pinched axially between   two protrusions (10a) integral with the cover (2).   4. Mechanism according to claim 3, characterized in that the protrusions (10a) belong to axially elastic tongues (10) connecting in rotation the plate of   pressure (1) at the cover (2) with axial mobility.   5. Mechanism according to claim 4, characterized in that the tongues (10) are of tangential orientation by being fixed at their first end to the cover (2) and in that the protrusions (10a) extend the first ends of the tongues ( 10).   6. Mechanism according to any one of claims   1 to 5, characterized in that the ring (330) with ramps (32) is linked in rotation by cooperation of shapes with the part intermediate (310).   7. Mechanism according to claim 6, characterized in that the ring (330) has tabs (350) passing through   notches (340) in the intermediate piece.   8. Mechanism according to any one of claims   i to 5, characterized in that the ring (330) with ramps (32) is linked in rotation to the intermediate piece (310) by axially elastic tongues allowing axial movement of the ring (330).   9. Mechanism according to any one of claims   1 to 8, characterized in that the intermediate piece consists of   a washer (310) centered by the pressure plate.   10. Mechanism according to any one of the claims   1 to 9, characterized in that the toothing (31) is formed in the bottom of a recess made at the external periphery of the part intermediate (310).