EP2791527A1

EP2791527A1 - Clutch with compensation for wear, notably for a motor vehicle

Info

Publication number: EP2791527A1
Application number: EP12815745.0A
Authority: EP
Inventors: Hervé MAUREL; Christophe Dhalleine
Original assignee: Valeo Embrayages SAS
Current assignee: Valeo Embrayages SAS
Priority date: 2011-12-16
Filing date: 2012-12-14
Publication date: 2014-10-22
Also published as: KR20140104432A; FR2984433A1; CN103998808A; WO2013088089A1; CN103998808B; FR2984433B1

Abstract

Clutch with compensation for wear, notably for a motor vehicle. The invention relates to a clutch with compensation for wear, notably for a motor vehicle, and comprising wear-compensation means (33) comprising a ratchet (60) that operates a ratchet wheel (56), the ratchet comprising control stops (66) intended to rest against a cover (8), the ratchet being designed in such a way that the control stops (66) are made to rest against the cover (8) by a diaphragm when the latter is moved outside of a normal operating zone defined between clutched and declutched positions.

Description

Clutch with catch-up of wear, in particular for vehicle

automotive

The present invention relates to a wear-catching clutch, in particular for a motor vehicle, and more particularly to a dual clutch with wear-compensating clutch.

A double clutch alternately couples the motor shaft of the vehicle with two coaxial input shafts of a gearbox, which can be robotic type.

Thus, a dual clutch allows to change gears while maintaining the transmission of a torque engine to the vehicle wheels. Indeed, the two clutches are respectively associated with even and odd gear ratios. During a gearshift, a first clutch is disengaged while the second clutch is engaged, so that the engine torque is progressively transferred from the first to the second clutch.

Each clutch comprises a mechanism comprising a diaphragm for cooperating with a pressure plate integral in rotation with the cover and the motor shaft. Each diaphragm is movable by means of a corresponding clutch abutment, between a rest position and an active position. Depending on the type of clutch, the active position of the diaphragm corresponds to a coupling or decoupling of the shafts of the engine and the gearbox and the rest position of the diaphragm corresponds to a decoupling or a coupling of these shafts. These are respectively a normally open clutch and a normally closed clutch.

The clutch stop is controlled by an actuator controlled by an electronic computer to exert a predetermined force on the diaphragm and move it over a given distance.

The pressure plate of each clutch, urged by the corresponding diaphragm, is intended to clamp a friction disc on a corresponding reaction plateau. A reaction plate may be provided for each clutch. Alternatively, a single reaction plate common to both clutches, mounted between the two friction discs, is used.

Each friction disk is rotatably connected to an input shaft of the gearbox and each reaction plate is rotatably connected to a flywheel connected to the drive shaft. Thus, the clamping of a friction disk between the corresponding pressure and reaction plates allows the transmission of a torque between the drive shaft and the shaft of the associated gearbox.

The use of the clutches causes wear of the friction linings of the friction discs as well as the counter-materials of the associated pressure and reaction plates. This results in a variation of the position of each pressure plate relative to the associated reaction plate, generating a variation of the friction disk clamping force and / or a modification of the position of the licking point and the Clutch thrust bearing. It is recalled that the licking point is the position from which a portion of the engine torque is transmitted to the gearbox shaft when closing the clutch.

The document FR 2 847 626, in the name of the Applicant, proposes a clutch equipped with wear compensating means interposed between a pressure plate and a diaphragm mounted on a cover fixed to a reaction plate. These wear-compensating means comprise a ring with circumferential ramps which cooperate with counter-ramps complementary to the pressure plate. The ramp ring also serves to support the diaphragm so that the rotation of the ring relative to the pressure plate causes the ramps to move relative to the counter-ramps and thus the axial displacement of the pressure plate. relative to the diaphragm, lid and reaction plate. The distance between the pressure plate and the associated reaction plate is thus varied in a way that offsets the wear. A toothed member is also fixed on the ramp ring and meshes with a worm mounted in a cassette attached to the cover, the toothed member being at right of the worm.

The worm is coupled in rotation with a ratchet wheel cooperating with a pawl fixed on the cover. The worm and / or the ratchet wheel are axially pressed by an elastic member against a wing of the cassette.

The pawl is in the form of an elastic blade having a control tab cooperating with the teeth of the ratchet wheel so as to allow the rotation of the ratchet wheel in a direction of rotation, in case of wear, and to prevent the rotation of the ratchet wheel in the opposite direction of rotation, the diaphragm bearing against a pawl of the return tongue, so as to move the control tab during its actuation. The pawl further comprising control stops intended to bear against a fixed cover relative to the reaction plate, during the actuation of the diaphragm

In this way, in case of wear and during successive actuations of the diaphragm, the pawl causes rotation of the ratchet wheel and the worm, the latter causing rotation of the ring carrying the ramps, by the intermediate of the toothed organ. This progressively increases the distance between the pressure plate and the cover and gradually decreases the distance between the pressure plate and the associated reaction plate, so as to compensate for wear.

In a clutch of normally closed type, the diaphragm is movable between an engaged position and a disengaged position, the pawl control stops abutting the fixed cover at a point between the engaged and disengaged positions.

In a clutch of the normally open type, there may be an operating zone located beyond the disengaged position. Thus, in some cases of operation, the diaphragm can be moved beyond the disengaged position, so as to come into contact with a fixed stop which may be the bottom of the gearbox, a support of the fork actuating the clutch or the actuator of the clutch abutment corresponding. These cases of operation are, for example, a stopping of the engine or an operation of the engine at idle.

Such an offset beyond the disengaged position ensures that the disengagement point is always reached, regardless of the dimensional tolerances of the various components and the conditions of use of the clutch. These tolerances and / or conditions may require an additional safety stroke between the disengagement point and the rest position of the vehicle, for example.

In general, in a clutch of normally open type, the control stops come into contact with the cover in an area between the disengaged and engaged position of the diaphragm, close to the disengaged position.

Thus, in the aforementioned cases of operation, the diaphragm pushes the control stops bearing against the cover so that the pawl is held in abutment against the cover, the return tongue continuing to be deformed until it that the diaphragm stops by abutment on the bottom of the gearbox for example.

The return tongue thus undergoes deformation and significant stresses, which can lead to a degradation of the wear-compensating function.

This immobilization on the bottom of the gearbox, for example, also makes it possible to avoid inadvertent catch-ups due to very severe and repeated uses of the clutch.

This problem is not limited to the case of double clutches.

The invention aims in particular to provide a simple, effective and economical solution to this problem. For this purpose, it proposes a wear-catching clutch, in particular for a motor vehicle, comprising at least one reaction plate intended to be coupled in rotation to a driving shaft, at least one friction disk carrying friction linings and intended to to be coupled to a driven shaft, at least one pressure plate operable by an annular diaphragm for clamping or releasing the friction disc on the reaction plate, and wear compensating means disposed between the diaphragm and the pressure plate and having ramp means cooperating with counter ramp means so that the rotation of the ramp means relative to the counter ramp means changes the distance between the diaphragm and the pressure plate, the ramp means bearing teeth meshing with an endless screw coupled to a ratchet wheel cooperating with a pawl adapted to be displaced when actuating the diaphragm, the ratchet formed of an elastic blade having a control tab cooperating with the teeth of the ratchet wheel so as to allow the rotation of the ratchet wheel in a direction of rotation in case of wear, and to prevent rotation of the ratchet wheel; ratchet wheel in the opposite direction of rotation, the pawl further comprising a return tongue, the diaphragm being adapted to push the control tongue towards the ratchet wheel, in a first case of operation, and to push the tongue in order to move the control tongue away from the ratchet wheel, in a second operating case, the pawl further comprising at least one control stop intended to bear on a fixed part with respect to the reaction plate, during the actuation of the diaphragm, characterized in that the pawl is designed so that the control stop is brought to bear on said fixed part by the diaphragm when the latter is moved out of a normal operating zone defined between clutch and disengagement positions.

The invention thus proposes to shift the support of the control stops in a particular operating zone, located beyond the zone of normal operation defined between the clutch and clutch positions. In this way, the deformation of the return tongue is limited in amplitude and frequency of use, which prevents its degradation. The life of the pawl is therefore considerably increased. This advantage also makes it possible to use a less resistant material for producing said return tongue.

This also has the consequence that the wear-catching means are actuated only if the diaphragm is moved beyond the normal operating zone.

Preferably, the diaphragm comprises an elastic zone and is intended to be actuated by a clutch abutment, the clutch being of normally open type so that, when a zero or limited force is applied by the clutch abutment on the diaphragm , it is moved to the disengaged position by the action of the elastic zone.

According to one characteristic of the invention, in normal operation, the diaphragm is movable between a disengaged position in which the friction disc is released and in which the control stop does not bear against said fixed part, and a position engaged in wherein the friction disk is clamped by the pressure plate against the reaction plate, the diaphragm being movable beyond the disengaged position, to a first extreme position in which the pawl control abutment bears on said fixed part.

Advantageously, the diaphragm is movable beyond the engaged position, to a second extreme position in which the ratchet control tongue is pushed by the diaphragm towards the ratchet wheel.

Thus, the actuation of the pawl is done only if the diaphragm is moved alternately between the first and second extreme positions. The diaphragm may comprise an actuating finger extending between the control tongue and the return tongue, intended to come into contact with one or the other of said tongues depending on the position of the diaphragm, the spacing between the control tongue and the return tongue being greater than the thickness of the actuating finger.

A game is formed between the actuating finger and said tongues. The dimensioning of this game makes it possible to adjust the positions from which the actuating finger bears against the control tongue or against the return tongue, so as to actuate the pawl only when it is necessary.

The subject of the invention is also a wear-compensating clutch, in particular for a motor vehicle, comprising at least one reaction plate intended to be coupled in rotation to a driving shaft, at least one friction disc carrying friction linings and intended to be coupled to a driven shaft, at least one pressure plate operable by an annular diaphragm, this diaphragm being displaceable by means of a corresponding clutch abutment, for tightening or releasing the friction disk on the reaction plate, and wear compensating means disposed between the diaphragm and the pressure plate and having ramp means cooperating with counter ramp means so that the rotation of the ramp means relative to the counter means ramps changes the distance between the diaphragm and the pressure plate, the ramp means having teeth meshing with a worm coupled to a cooperated ratchet wheel ratchet being formed by an elastic blade having a control tab cooperating with the teeth of the ratchet wheel so as to allow the rotation of the ratchet wheel in a direction of rotation in case of wear, and to prevent the rotation of the ratchet wheel in the opposite direction of rotation, the pawl further comprising a return tongue, the diaphragm, which comprises an external peripheral actuating finger ratchet interposed between the tongue of control and the return tongue, the diaphragm being intended to push the control tongue towards the ratchet wheel, in a first case of operation, and to push the return tongue so as to move the wheel control tab away from the wheel ratchet, in a second case of operation, the pawl further comprising at least one control stop intended to bear on a fixed part relative to the reaction plate, during the actuation of the diaphragm, characterized in that the ratchet is designed so that the control stop is brought to bear on said fixed part by the diaphragm when it is displaced by the clutch abutment beyond its disengaged position, so that the finger of Actuation may be moved upstream of this position to its end position outside a normal operating zone defined between engaged and disengaged positions.

The invention further relates to a dual clutch, particularly for a motor vehicle, characterized in that it comprises at least one clutch of the aforementioned type.

The invention finally relates to a method of operating a wear-compensating clutch, coupled to an output shaft of an engine, characterized in that, when said output shaft has a rotational speed comprised in a first range. of values corresponding to a so-called normal operation of the engine, the diaphragm is moved in the normal operating zone, between the engaged and disengaged positions in which it clamps, respectively releases, the friction disk on the reaction plate, and in this respect that when the output shaft of the engine has a rotational speed within a second range of values corresponding to idle operation and / or engine stop, the diaphragm is moved out of the normal operating zone, in order to bring the control abutment bearing on the fixed part relative to the reaction plate. For example, the first range of values is greater than 300 rpm, the second range of values being less than 800 rpm.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example with reference to the accompanying drawings in which:

FIG. 1 is a half-view in axial section of a double clutch according to the invention,

FIG. 2 is a perspective view of part of the double clutch; FIGS. 3 to 5 are detailed and perspective views, illustrating the means of compensating for the wear of the double clutch according to the invention;

FIG. 6 is a perspective view in axial section of a part of the double clutch,

FIGS. 7 and 8 are detailed views, in perspective and from the side, of two variants illustrating in particular the retention in position of the toothed member,

FIG. 9 is a cutaway and perspective view of part of the double clutch,

FIG. 10 is a detail view, in perspective, illustrating the opening formed in the bearing washer of the second clutch,

- Figures 1 1 and 1 2 are detail views, in perspective, illustrating the positioning of the centering rivets of the first diaphragm on the lid,

FIG. 13 is a perspective view of part of the double clutch according to the invention,

FIGS. 14 and 15 are perspective views illustrating a part of the wear compensating means,

- Figure 16 is a diagram illustrating the different phases of operation of the diaphragm.

FIGS. 1 and 2 illustrate a double clutch according to the invention, intended to couple a motor with a first and a second input shaft 1, 2 of a gearbox. The double clutch comprises first and second clutches 3, 4 of different ratios of parities.

The first clutch comprises a first pressure plate 5 and a reaction plate 6 between which a first friction disc 7 extends. The first pressure plate 5 is coupled in rotation to the reaction plate 6 and is movable in translation relative to to it, between an engaged position and a disengaged position, in which it squeezes the first friction disc 7 on the reaction plate 6, or respectively releases the first friction disc 7.

The reaction plate 6 is fixed on a cover 8 coupled to the motor shaft. The first friction disc 7 is coupled to the first input shaft 1 of the gearbox. Thus, in the engaged position of the first clutch 3, the motor shaft is coupled to the first input shaft 1 of the gearbox.

The first pressure plate 5 is fixed on a cover 9 movable in translation relative to the reaction plate 6 and the cover 8, and extending towards the front.

A first diaphragm 10 is pivotally mounted on the cover 8, by means of rivets January 1 ensuring the centering of said diaphragm 10 while allowing it to tilt. The first diaphragm 1 0 is in the form of an elastic annular plate bearing on the cover 8 at a bearing zone 12, the first diaphragm pivoting around this bearing zone 12. support 1 2 is formed by a projecting portion of the cover 8.

The control of the first clutch 10 is conventionally performed by means of a first clutch abutment 13 cooperating with the radially inner periphery of the first diaphragm 10. The first diaphragm 10 forms a lever transmitting the force applied by the first clutch abutment 13 at the first pressure plate 5, via the movable cover 9. In order to allow effective clamping of the first friction disc 7, the first diaphragm 10 is pre-loaded at rest. Without this pre-charge, the diaphragm 10 would, at rest, in a state of elasticity requiring a start of travel of the clutch abutment 13 relatively large to apply an effective clamping force on the corresponding friction disc 7. When the first clutch abutment 1 3 is actuated, it balances the pre-charge of the first diaphragm 10 before starting the clamping of the first friction disc 7. The pre-charge of the first diaphragm 10 makes it possible to reduce the approach stroke of the clutch stop to tighten the friction disc, and always have a minimum precharge force, for example on the ball bearing of the clutch abutment and on the ball bearing that supports the clutch. This increases the life of said bearings and limits the vibration of the clutch.

The first clutch is of the normally open type. The rest position of the diaphragm therefore corresponds to a disengaged state of the clutch device. The diaphragm preferably has a portion of the Belleville washer type for returning the diaphragm to its rest position.

In the rest position of the first diaphragm 10, that is to say when the first abutment 1 3 exerts little or no effort on the first diaphragm 10, the first diaphragm 10 therefore does not exert (or little) on the first pressure plate 5. The first pressure plate 5 is moved away from the reaction plate 6 by means of appropriate return means, such as resilient tongues, so as to release the first friction disc 7 .

In a first embodiment shown in Figures 1 and 1 1, the rivets January 1 are cylindrical and have a head 14 of larger diameter intended to abut against radial fingers 1 5 of the first diaphragm 10, extending to the radially inner periphery of the latter. In a second embodiment shown in Figure 12, the rivets January 1 may have a head 14 generally T-shaped, having two radial portions extending opposite the fingers 15 of the first diaphragm 10 so as to serve as a stop. This embodiment makes it possible to limit the radial size of the rivets 1 1.

The second clutch comprises a second pressure plate 16, and a second friction disc 17 extending radially between the reaction plate 6 and the second pressure plate 16. The same reaction plate 6 is thus used for the two clutches 3 , 4, each friction disc 7, 17 being disposed on the side of one of the two radial bearing surfaces of the reaction plate 6. The second pressure plate 17 is rotatably coupled to the reaction plate 6 and is movable in translation thereof, between an engaged position and a disengaged position, in which it clamps the second friction disc 17 on the reaction plate 6, or respectively releases the second friction disc 17.

The second friction disc 17 is coupled to the second input shaft 2 of the gearbox. Thus, in the engaged position of the second clutch 4, the motor shaft is coupled to the second input shaft 2 of the gearbox.

A second diaphragm 18 is pivotally mounted on the cover 8, by means of rivets January 1 '(Figure 1) ensuring the centering of said diaphragm 18 while allowing its tilting. The second diaphragm 18 is, as before, in the form of an elastic annular plate bearing on the cover 8 at a bearing zone 19, the second diaphragm 18 thus pivoting around this bearing zone 19 .

The control of the second clutch 4 is conventionally done by means of a second clutch abutment 20 cooperating with the radially inner periphery of the second diaphragm 18, via a force transmission member, not shown. The second diaphragm 18 forms a lever transmitting the force applied by the second clutch abutment 20 to the second pressure plate 1 6, in order to allow the effective clamping of the second friction disc 17. The bearing zone of the second diaphragm 18 on the second pressure plate 16 is referenced 21 in FIG. 1, this zone 21 being situated radially between the bearing zone 19 of the diaphragm 18 on the cover 8 and the bearing area of the second clutch abutment 20 on the second diaphragm 18.

A support washer 22, fixed on the cover 8 by means of rivets 23 (FIGS. 9 and 10), comes to press and hold in position the radially outer periphery of the second diaphragm 18 against the bearing zone 1 9.

The second clutch 4 is also of the normally open type.

In the rest position of the second diaphragm 18, that is to say when the second clutch abutment 20 exerts little or no effort on the second diaphragm 18, the second diaphragm 18 does not exert (or little ) the second pressure plate 16 is moved away from the reaction plate 6 by means of appropriate return means, such as resilient tongues, so as to release the second friction disk 17. The second diaphragm 18, the second pressure plate 16 and the second friction disc 17 are housed in the cover 8. The first friction disk 7 and the first pressure plate 5 are housed in a cover 24, fixed relative to the lid 8 and to the reaction plate 6.

The cover 8 comprises, from the rear towards the front, radial flanges 25 for fixing on the reaction plate 6, connected to an annular portion 26 (FIG. 1) surrounding the aforementioned elements of the second clutch 4, even extended by an annular portion 27 extending radially inwardly.

As can be seen in FIG. 1, the movable cover 9 has a radially outer portion 28 extending forwardly from the first pressure plate 5 and surrounding the cover 8, extended at the front by a portion 29 ' extending radially inward, itself prolonged by a cylindrical flange 30 extending rearwardly towards the second diaphragm 18.

As represented in FIGS. 1 and 11, the free edge 31 of the cylindrical rim 30 defines substantially radial faces able to serve to support the first diaphragm 10 so as to limit its movement when the first clutch 3 is in the storage position, c that is to say before mounting the double clutch on the gearbox. Alternatively, the diaphragm can also bear on the heads 14 of the rivets January 1.

Once the double clutch mounted on the vehicle, the first diaphragm 10 bears against the first clutch abutment 13 and the first diaphragm 10 no longer bears against the free edge 31 or on the heads 14 of the rivets 11, in disengaged position.

In addition, as can be seen in FIG. 13, the radially outer portion 28 has radially rearwardly facing radial surfaces 32 intended to bear against radial faces 33 facing the front of the reaction plate 6. makes it possible to limit the displacement of the mobile cover 9 in transport phases of the double clutch, before mounting on a gearbox of a vehicle.

In order to compensate for the wear of the first friction disc 7, the first pressure plate 5 and / or the reaction plate 6, the first clutch 3 is equipped with wear-catching means 33.

The structure and operation of these wear compensating means 33 are similar to those of the means described in document FR 2 847 626, in the name of the Applicant, their positioning being however different.

The wear compensating means 33 comprise a ring 34 mounted around the cylindrical rim 30 of the movable cover 9 and having, radially from the inside to the outside, a radial portion 35, extended by a frustoconical portion 36 flared towards the back, itself extended by a substantially cylindrical rim 37 extending forwardly and whose free edge forms ramps 38 extending circumferentially and inclined from the rear to the front. These ramps 38 are particularly visible in Figures 2, 3, 5, 7, 8 and 9.

The ring 34 is movably mounted in translation and in rotation around the cylindrical rim 30.

Four lugs 39, 40 extend radially outwardly from the rim 37 of the ring 34 (FIG. 2). Two tabs 39 serve to fix a member 41 in the form of a circular arc, whose outer edge has a toothing 42 extending over only a portion of said outer edge. Two other tabs 40 serve to fix a balancing member 43, also in the form of a circular arc, located diametrically opposite to the toothed member. The circumferential ends of the toothed member 41 and of the balancing member 43 are fixed to the corresponding tabs 39, 40 by means of rivets 44.

The ramps 38 are supported on counter-ramps 45 formed on the rear surface 46 of the radial portion 29 of the movable cover 9 (Figure 9).

The rotation of the ring 34 carrying the ramps 38 relative to the movable cover 9 thus causes the displacement of the ring 34 along the cylindrical rim 30 of the movable cover 9.

The movable lid 9 being coupled in rotation with the lid 8 and the reaction plate 6, it is sought to rotate the ring 34 carrying the ramps 38. For this, the toothing 42 of the toothed member 41 meshes with a screw without end 47 mounted in a cassette 48 fixed on the cover 8.

More particularly, the worm 47 is pivotally mounted around a shaft 49 and inside a cassette attached to the outer wall (or front wall) of the radial portion 27 of the cover 8. External wall design , the wall of the lid 8 which is opposed to the internal space housing the second friction disc 17, the second pressure plate 16 and the second diaphragm 18. As can be seen in particular in Figures 3, 4 and 13, the cassette 48 has a generally U-shaped, the two branches or wings 50, 51 of the U carrying the ends of the shaft 49, the base 52 of the U extending from one wing 50 to the other 51 partially surrounding the worm 47.

A recess on the top of the cassette 48 (Figure 3) allows better holding centrifugation.

The free ends of said wings 50, 51 carry lateral flanges 53 for fixing on the cover 8. These flanges 50, 51 are fixed to the cover 8 by rivets whose heads 54 extend facing the rear wall of the body toothed 41. As can be seen more clearly in FIGS. 7 and 8, the cassette 48 further comprises a flange 55 extending radially inwards, facing the front face of the toothed element 41. In operation, the toothed member 41 is preloaded on the flange 55.

In the variant of FIG. 7, the flanges 50, 51 of the cassette 48 comprise surfaces 55 'turned facing the rear face of the toothed element 41.

Said surfaces 55 'and the flange 55 of the cassette 48 form stops limiting the axial displacement or the bending of the toothed element 41 so that the toothing of the latter remains situated at right angles to the axis of the worm 47.

In the variant of FIG. 7, it is the heads 54 of the aforementioned rivets and the rim 55 of the cassette which form the abutments limiting the axial displacement or the bending of the toothed element 41.

The shaft 49 further carries a ratchet wheel 56 coupled in rotation with the worm screw 47, for example formed integrally therewith. An elastic member 57 is mounted between the wing 51 and the ratchet wheel 56 so as to press the ratchet wheel 56 and the endless screw 47 against the opposite wing 50. This wing 50 has an inner surface 58 (Figure 3), intended to come into contact with the worm 47, which is hardened to increase the hardness and limit its wear by friction. This hardening can be performed by stamping, knurling, roller burnishing, mechanical polishing or by electrochemical operations, such as electropolishing or electrolytic polishing.

As can be seen in FIGS. 1 and 6, an opening 59 is formed in the movable cover 9 in order to allow the cassette 48 to be mounted outside the cover 8, the cassette 48 extending partially through this opening 59 .

The ratchet wheel 56 cooperates with a pawl 60 in the form of a metal elastic plate attached to the front face of the radial portion 27 of the cover 8.

The pawl 60 has a radially inner portion extending substantially radially and fixed on the front face of the cover 8, and a radially outer portion forming an angle with the radially inner portion, extending rearward through an opening 61 of the cover 8.

The structure of the pawl 60 is similar to that of the pawl described in the document FR 2 847 626.

In particular, the radially outer part of the pawl 60 comprises a control tongue 62 (FIGS. 1, 6 and 1 3) cooperating with the teeth of the ratchet wheel 56 so as to allow rotation of the ratchet wheel 56 in a direction rotation, in case of wear, and to prevent the rotation of the ratchet wheel 56 in the opposite direction of rotation. The radially outer portion of the pawl 60 also includes a return tab 63 (Figures 1, 6, 14 and 15).

The first diaphragm 1 0 comprises an external peripheral pin 64 for actuating the pawl 60, intended to bear against the return tongue 63 of the pawl 60 in the disengagement phase, and intended to bear against the control tongue 62 in clutch phase.

More particularly, the actuating finger 64 is interposed between the control tongue 62 and the return tongue 63, and is intended to come into contact with one or the other of said tongues 62, 63, depending on the position of the first diaphragm 1 0. The gap between the control tongue 62 and the return tongue 63 is greater than the thickness of the actuating finger 64, so that a clearance j is formed between the finger 64 and said tongues 62, 64 (Figure 1 5).

In order not to hinder the movement of the actuating finger 64 and the return tongue 63, the bearing washer 28 has an opening 65 (FIG. 1 and 10) permitting the passage of said actuating finger 64 and said return tongue 63, when the first diaphragm 10 is actuated in the disengaging phase.

The radially outer portion of the pawl 60 further comprises two lateral tabs 66 (FIGS. 3, 4, 6, 14 and 15) forming control stops intended to bear against the lateral edges of the opening 61 of the cover 8 during the actuation of the first diaphragm 10 in the disengaging phase.

The operation of the wear compensating means 33 will now be described. As indicated above, this operation is similar to that of the wear compensating means of the document FR 2 847 626.

It will be assumed first of all that the linings 67 of the first friction disc 7, the first pressure plate 5 and the reaction plate 6 are not worn. In this case, in the clutching phase, the first diaphragm 10 is displaced by the first clutch abutment 13, so that the outer periphery of the first diaphragm 10 and its actuating finger 64 are displaced forwards. by pushing the control tongue 62. The free end of the control tongue 62 is then pushed into the bottom of a tooth of the ratchet wheel 56.

During disengagement, the outer periphery of the first diaphragm 10 is moved backwards towards its rest position. The actuating finger 64 of the first diaphragm 10 then presses on the return tongue 63 of the pawl 60. Consequently, the return tongue 63 and the control tongue 62 of the pawl 60 are moved backwards, until that the lateral tabs 66 of the pawl 60 abut against the side edges of the opening 61 of the cover 8. If no wear has occurred, the removal of the control tongue 62 vis-à-vis the corresponding tooth of the ratchet wheel 56 is not sufficient to to jump the tooth. The ratchet wheel 56 can not therefore be rotated during the next clutching phase and the wear compensating means 33 do not modify the position of the first pressure plate 5 with respect to the reaction plate 6.

If, on the contrary, the first friction disk 7, the first pressure plate 5 and / or the reaction plate 6 are worn, in the clutch phase, the outer periphery of the first diaphragm 1 0 and the control tongue 62 can be moved forward sufficiently large enough to slightly rotate the ratchet wheel 56 around the shaft 49. During this clutching phase, the ring 34 is immobilized in rotation, by wedging between the first diaphragm 10 and the movable cover 9. Thus, the toothed member 41 is also immobilized in position. The rotation of the ratchet wheel 56 and the worm 47 meshing with the toothing 42 of the toothed member 41 then causes the ratchet wheel assembly 56 - worm 47 to slide along the shaft 49. and towards the wing 51, compressing the elastic member 57. Of course, the width of the teeth of the ratchet wheel 56 and the width of the control tongue 62 are such that their cooperation is maintained during this sliding.

In the next disengaging phase, the ring 34 carrying the toothed member 41 is released, the control tongue 62 and the spring prevent the ratchet wheel 56 and the worm 47 from rotating and the ratchet wheel assembly 56 - worm 47 slides along the shaft 49 and towards the wing 50, under the action of the elastic return member 57. This causes the rotation of the ring 34 relative to the movable cover 9. The ramps 38 are thus displaced relative to the counter-ramps 44, so as to move away the ring 34 and the movable cover 9. The distance between the bearing zone 68 of the first diaphragm 1 0 on the ring 34 and the part radial 29 of the movable cover 9 is increased, which ultimately has the effect of reducing the distance between the first pressure plate 5 and the reaction plate 6 to compensate for wear.

Several phases of clutch and disengagement may be necessary to make up the entire game generated by wear.

The invention thus proposes a double clutch, one of the clutch mechanisms 3, 4 is equipped with wear compensating means 33, having a reduced axial and radial dimensions. Although the structure and operation of these wear compensating means 33 are similar to those of document FR 2 847 626, their arrangement at the front of the double clutch makes it possible to increase the compactness of the double clutch while allowing the catching up of the clutch mechanism 3 located at the rear of the double clutch.

In the following, the different operating phases of the pawl 60 and the first diaphragm 10 will be examined with reference to FIG.

FIG. 16 shows the total travel of the actuating finger 64 of the first diaphragm 10, this stroke being delimited by a first extreme position A and by a second extreme position F. The position A is associated with the beginning of the stroke ( 0%) of the diaphragm and the F position at the end (100%) of the stroke.

Throughout its stroke, the actuating finger 64 passes through successive intermediate positions, referenced B, C, D, and E.

Position B represents the maximum disengaged position reached by the actuating finger 64, in the normal operating phase.

The position E represents the maximum engaged position reached by the actuating finger 64, in the normal operating phase.

The normal operating zone Z1 is defined by the clutching and disengaging phase described above, making it possible to clamp or release the first friction disk 7 against the reaction plate 6. When the engine is idling or stopped, the diaphragm can be moved beyond its disengaged position, so that the actuating finger 64 can be moved upstream of the position B to its first extreme position A.

In addition, for reasons which will be detailed later, the actuating finger 64 can be moved downstream of the point E, to its second extreme position F.

In order to avoid significant deformation of the return tongue 63, the pawl 60, its actuating finger 64 and the cover 8 are designed in such a way that the control abutments 66 bear against the cover 8 (more particularly against the edges of the opening 61 of the cover 8) only when the actuating finger 64 is moved in a zone Z2 located between the positions A and B, that is to say outside the normal operating zone Z1 . Preferably, the control stops 66 bear against the cover 8 only when the actuating finger 64 is in its first extreme position A or close to this position A.

The actuating finger 64 is in contact with the return tongue 63 in the zone Z4 defined between the positions A and C, the position C being the position from which the actuating finger 64 comes to rest on the tongue 63. The position C can be located in the normal operating zone Z1 and is close to the disengaged position B.

In this way, it is avoided that the return tongue 63 is deformed too much when the actuating finger is moved beyond the normal operating zone Z1, in the zone Z4.

This also implies that, in order to actuate the wear-catching means 33, the actuating finger 64 must be moved until reaching its first extreme position A.

This is achieved by controlling the corresponding clutch abutment 13, using appropriate means. In addition, although not required, the ratchet wheel 56, the control tongue 62 and the pawl 60 may be designed to operate the ratchet wheel 56 only if the actuating finger 64 exceeds normal operating zone Z1 and reaches the second extreme position F. The zone located between the positions E and F is referenced Z3 in FIG.

In this way, the wear compensating means 33 are actuated only if the actuating finger 64 is moved alternately between its two extreme positions A and F.

The actuating finger 64 is in contact with the control tongue 62 in the zone Z5 defined between the positions D and F, the position D being the position from which the actuating finger 64 comes to rest on the tongue The position D can be located in the normal operating zone Z1.

It will be noted that, because of the clearance j (FIG. 15), the actuating finger 64 bears against none of the tongues 62, 63 when it is in the zone situated between the positions C and D.

If the positions A and F are defined as respectively 0% and 100% of the total stroke of the actuating finger 64, then the position B is situated in an area comprised between 2 and 30% of the stroke. position C is situated in an area between 2% and 35% of the total stroke, position D is situated in an area between 35% and 100% of the total stroke, and position E is situated in an area comprised between between 60 and 100% of the total race.

Claims

1. Wear-compensating clutch, in particular for a motor vehicle, comprising at least one reaction plate (6) intended to be coupled in rotation to a driving shaft, at least one friction disc (7, 17) bearing friction linings ( 67) and for coupling to a driven shaft (1, 2), at least one pressure plate (5, 1 6) operable by an annular diaphragm (1 0, 1 8) for clamping or releasing the friction disk ( 7, 17) on the reaction plate (6), and wear compensating means (33) disposed between the diaphragm (10) and the pressure plate (5) and having ramp means (34, 38). cooperating with counter-ramp means (9,44) so that rotation of the ramp means (34,38) relative to the counter-ramp means (9,44) changes the distance between the diaphragm ( 10) and the pressure plate (5), the ramp means (34, 38) carrying a toothing (41, 42) meshing with a worm (47) coupled to a wheel ratchet (56) cooperating with a pawl (60) adapted to be displaced during the actuation of the diaphragm (1 0), the pawl (60) being formed by an elastic blade having a control tongue (62) cooperating with the teeth of the ratchet wheel (56) so as to allow rotation of the ratchet wheel (56) in a direction of rotation in case of wear, and to prevent the rotation of the ratchet wheel (56) in the direction counterclockwise rotation, the pawl (60) further comprising a return tongue (63), the diaphragm (10) being adapted to urge the control tongue (62) towards the ratchet wheel (56), in a first operating case, and to push the return tongue (63) so as to move the control tongue (62) away from the ratchet wheel (56), in a second case of operation, the pawl further comprising at least one stop control device (66) intended to rest on a fixed part (8) with respect to the reaction plate (6), s of the actuation of the diaphragm (1 0), characterized in that the pawl (60) is designed so that the control stop (66) is brought into abutment on said fixed part (8) by the diaphragm (10) when it is moved outside a normal operating zone (Z1) defined between engaged and disengaged positions (B, E).

2. Clutch according to claim 1, characterized in that the clutch is of the normally open type so that the diaphragm (1 0) is returned to the rest position when a zero or limited force is applied by the abutment. clutch (13) on the diaphragm (1 0).

3. Clutch according to claim 1, characterized in that the clutch is of the normally open type so that the diaphragm (10) is returned to the disengaged position when a limited force is applied by the clutch abutment (1 3 ) on the diaphragm (10).

4. Clutch according to claim 2 or 3, characterized in that in normal operation, the diaphragm (10) is movable between a disengaged position (B) in which the friction disk (7) is released and in which the stop of control (66) does not rest on said fixed part (8), and an engaged position (E) in which the friction disc (7) is clamped by the pressure plate (5) against the reaction plate (6). ), the diaphragm (10) being displaceable beyond the disengaged position (B), into a first extreme position (A) in which the control stop (66) of the pawl (60) bears on said part fixed (8).

5. Clutch according to one of claims 1 to 4, characterized in that the diaphragm is arranged to be movable beyond the disengaged position so as to come into contact against a fixed stop.

6. Clutch according to claim 5, characterized in that the fixed stop is the bottom of the gearbox, a support of the fork actuating the clutch or the actuator of the corresponding clutch abutment.

Clutch according to Claim 4 and possibly one of Claims 5 and 6, characterized in that the diaphragm (10) is displaceable beyond the engaged position (E), within one second extreme position (F) in which the control tongue (63) of the pawl (60) is pushed by the diaphragm (1 0) in the direction of the ratchet wheel (56).

8. Clutch according to one of claims 1 to 7, characterized in that the diaphragm comprises an actuating finger (64) extending between the control tongue (62) and the return tongue (63) for contacting one or the other of said tongues (62, 63) as a function of the position of the diaphragm (10), the distance between the control tongue (62) and the return tongue (63) being greater than to the thickness of the actuating finger (64).

9. A wear-compensating clutch, in particular for a motor vehicle, comprising at least one reaction plate (6) designed to be coupled in rotation to a drive shaft, at least one friction disc (7, 17) carrying brake lining friction device (67) and intended to be coupled to a driven shaft (1, 2), at least one pressure plate (5, 1 6) operable by an annular diaphragm (10, 18), this diaphragm being displaceable by means of a corresponding clutch abutment, for clamping or releasing the friction disk (7, 17) on the reaction plate (6), and wear compensating means (33) disposed between the diaphragm (10) and the plate pressure device (5) and comprising ramp means (34, 38) cooperating with counter-ramp means (9, 44) so that the rotation of the ramp means (34, 38) relative to the means counter-ramps (9, 44) changes the distance between the diaphragm (10) and the pressure plate (5), the ramp means (34, 38) nt teeth (41, 42) meshing with a worm (47) coupled to a ratchet wheel (56) cooperating with a pawl (60) adapted to be moved upon actuation of the diaphragm (10), the ratchet (60) being formed of an elastic blade having a control tongue (62) cooperating with the teeth of the ratchet wheel (56) so as to allow the rotation of the ratchet wheel (56) in a direction of rotation by wear, and to prevent the rotation of the ratchet wheel (56) in the opposite direction of rotation, the pawl (60) further comprising a return tongue (63), the diaphragm (10), which comprises an external peripheral pawl (60) for actuating the pawl (60) interposed between the control tongue (62) and the return tongue (63), the diaphragm (1 0) being intended to push the control tongue (62) towards the ratchet wheel (56), in a first case of operation, and to push the return tongue (63) so as to move the tongue away from control (62) of the ratchet wheel (56), in a second case of operation, the pawl further comprising at least one control stop (66) intended to bear on a fixed part (8) with respect to the plate reaction device (6), when actuating the diaphragm (10), characterized in that the pawl (60) is designed so that the control stop (66) is brought into abutment on said fixed part (8). ) by the diaphragm (1 0) when it is moved by the clutch stop beyond its disengaged position (B), that the actuating finger (64) can be moved upstream of this position (B) to its end position (A) outside a normal operating zone (Z1) defined between the engaged and disengaged positions ( B, E).

10. Double clutch, especially for a motor vehicle, characterized in that it comprises at least one clutch (3) according to one of claims 1 to 9.

1 1. A method of operating a wear-compensating clutch according to one of claims 1 to 10, coupled to an output shaft of an engine, characterized in that, when said output shaft has a rotational speed comprised in a first range of values corresponding to a so-called normal operation of the motor, the diaphragm (1 0) is moved in the normal operating zone (Z1) between the engaged and disengaged positions in which it clamps, respectively releases, the disc of friction (7) on the reaction plate (6), and in that, when the output shaft of the motor has a speed of rotation within a second range of values corresponding to a slow operation and / or a stop of the motor, the diaphragm is moved outside the area normal operation (Z1), so as to bring the control stop (66) bearing on the fixed part (8) relative to the reaction plate (6).