EP1003982A1

EP1003982A1 - Friction clutch with wear take-up device, in particular for motor vehicle

Info

Publication number: EP1003982A1
Application number: EP99928044A
Authority: EP
Inventors: Gilles Lebas; Pascal Maurel
Original assignee: Valeo SE
Current assignee: Valeo Embrayages SAS
Priority date: 1998-06-24
Filing date: 1999-06-23
Publication date: 2000-05-31
Also published as: FR2780464B1; DE19981375T1; FR2780464A1; WO1999067546A1

Abstract

The invention concerns a friction clutch, in particular for motor vehicles, comprising a clutching device including engaging means and declutching means and a control linkage for countering the engaging means via the declutching means. The engaging means are supported on a cover (15) integral with a rotational drive flywheel (11), for acting on a pressure plate (14) and clamping a friction disc (12) friction linings (13) between the pressure plate (14) and the flywheel (11), forming a reaction plate, and a wear take-up device (18) enables to compensate wear of the friction linings (13) at least, said wear take-up device being mounted inside the engaging device and means being provided for automatically adjusting the control linkage length (20, 21) based on wear.

Description

"Friction clutch with wear take-up device, in particular for a motor vehicle"

The present invention relates to a friction clutch, in particular for a motor vehicle, and relates more particularly to a clutch equipped with a device for compensating for wear, in particular friction linings, hereinafter said device for taking up wear; it relates more precisely to the control of such a clutch.

A conventional friction clutch generally comprises a reaction plate, possibly in two parts to form a damping flywheel or a flexible flywheel, fixed in rotation on a first shaft, usually a driving shaft such as the crankshaft of the combustion engine. internal, and supporting by its external periphery a cover to which is attached at least one pressure plate.

The pressure plate is integral in rotation with the cover and the reaction plate while being able to move axially under the stress of elastic engagement means with controlled axial action, generally a metal diaphragm bearing on the cover, while a friction disc , carrying friction linings at its outer periphery, integral in rotation with a shaft, usually a driven shaft such as the input shaft of the gearbox, is interposed between the pressure plate and the reaction plate of so as to be clamped together when the clutch is in the engagement position. The engagement means control the axial movement of the pressure plate when they are actuated in an antagonistic manner by a declutching stop.

During the service life of such a clutch, the friction linings as well as the counter materials, pressure plate and reaction plate, wear, which causes a variation in the position of the pressure plate and those clutch means and the clutch release bearing, from which it follows, on the one hand, a variation in the clamping force of the friction disc between the pressure and reaction plates due to changes in working conditions engagement means, and, on the other hand, that the force necessary to disengage is affected. By providing such a clutch with a wear take-up device, these drawbacks are avoided, the clutch means and the clutch release bearing, usually in constant contact with the clutch means, occupying the same position when the clutch is in position of engagement.

A friction clutch equipped with a wear take-up device is arranged so that one of the supports of the engagement means, either the support linked directly or indirectly to the cover, or the support linked directly or indirectly to the pressure plate, is axially offset, a means, called compensation, being provided to achieve this offset, in association with a means, called actuation, allowing the setting implements, in fact actuation, of said compensation means and a triggering means itself controlling the actuation means by authorizing or not the entry into function of the actuation means. Of course, a wear take-up device is controlled by a means, called a detection means, sensitive to the wear of the linings, directly or indirectly, that is to say for example sensitive to the position of at least 1 one of the components of the clutch influenced by said wear, said detection means acting on one of said compensation, actuation and triggering means.

Different types of wear take-up device are known.

For example, document FR-A-2 753 503 describes a clutch in which the wear take-up device comprises ramp means arranged circumferentially, constituting the compensation means, placed axially between the decalable support and the pressure plate and adapted to be driven in rotation by means of a toothing which they carry at their periphery and with which cooperates a worm screw arranged tangentially, means for driving the worm in rotation being provided, made operational by wear friction linings, as well as non-return means preventing the worm from rotating in the opposite direction to that in which it is driven in rotation by the rotation drive means when they are operational, the worm , the non-return means and the means for driving the worm in rotation being carried by a support integral with the cover, and the elastic means engaged axially acting yors being constituted by a diaphragm. The means for rotating the worm, are controlled by the diaphragm; the ramp means consist of a ring having the offset support of the diaphragm and inclined and circumferentially distributed ramps and the pressure plate has studs or ramps intended to cooperate with the ramps of the ramp means; the worm is slidably mounted along its axis while being subjected to the action of an elastic means called catch-up, constituting the actuating means, and, when it is moved along its axis, it drives in circumferential rotation said ramp means. The means for driving the worm in rotation are constituted by a ratchet wheel secured to the worm and the non-return means are constituted by a pawl which cooperates with the ratchet wheel. Here, the detection means is a tongue actuated by the diaphragm and adapted to cooperate with the ratchet wheel, its stroke increasing with wear until being able, when the clutch is engaged, to push a tooth of the ratchet wheel and rotate the screw by compressing the elastic take-up means; the release means is represented by a reduction in the load on the support cord, when disengaging, the elastic take-up means, when its load is sufficient to overcome the friction forces, allowing the displacement of the inclined ramps and therefore the axial offset of the plate support.

Thus, the detection means, here the tongue controlled by the diaphragm, acts, via the ratchet wheel, on the actuation means, here the elastic take-up means, causing an actuation force to appear; tripping takes place during a subsequent declutching operation.

In document GB-A-2 294 983, the engagement means consist of a diaphragm and the shiftable support is also the plate support; the compensation means is also constituted by ramps; the actuating means is a spring which acts permanently between ramps and counter-ramps in the direction of increasing the axial thickness; here again the triggering is carried out during the declutching operation by a reduction in the load on the support cord while the pressure plate moves, as a function of wear, with respect to a pin bearing on the reaction plate, said pin, frictionally passing through the pressure plate, constituting the detection means. This pin carries a stop in the form of a lever cooperating with the ramp means

; the detection means therefore acts on the compensation means.

In document GB-A-2 294 301, the engagement means are also constituted by a diaphragm, the compensation means by ramps and the actuation means by a spring acting permanently between the ramps and here the cover; here, the decalable support is the primary support carried by the cover; the clutch is of the pushed type and the release is obtained by subsidence of the secondary support, located opposite the primary support on the pressure plate side, elastically mounted, the maximum clutch release load increasing with wear , this constituting the detection means which, by collapsing, constitutes the triggering means. The detection means therefore acts on the triggering means, a clearance appearing between the primary and secondary supports when the secondary support subsides, said clearance being filled by a movement of the primary support under the action of the means. actuation.

In document US-A-5,564,541, according to the variant of FIG. 10, the detection means is a pin arranged with clearance between the cover and the reaction plate and passing through the pressure plate with friction, the effort required to move the pin relative to the pressure plate being greater than the restoring force of the pressure plate, here due to the tangential tabs; the actuating means is a spring which acts permanently between the pressure plate and the ramps which constitute the compensation means; it is the plate support which is movable, the clutch device being of the pulled type. Here the declutching stroke varies: the full declutching position is fixed in so that the trigger occurs at the end of this declutching operation, after detection of wear and appearance of a clearance, which is then filled under the action of the actuating means.

In document FR-A-2 599 446, according to the variant of FIG. 5, the elements are similar to those of the previous document except that the compensation means is an axial unidirectional freewheel and the actuation means a spring urging permanently the balls pressing against their ramps.

As a variant of FIG. 3 of document US-A-5,564,541, the detection means is a pin disposed with clearance between the cover and the pressure plate and passing through the cover with friction, the effort necessary to move the pin by relative to the cover being greater than the restoring force of the pressure plate here due to the tangential tabs; the actuating means is a spring which acts between the cover and a rotary ring provided with ramps intended to cooperate with counter-ramps; the cover support is therefore movable, the clutch being of the pulled type. Triggering occurs at the end of the declutching operation after detection of wear and the appearance of a clearance filled under the action of the actuating means; as in FIG. 10, the complete disengagement position is fixed, the clutch means comprising disengaging levers associated with helical springs bearing on the cover.

In all cases, the declutching operation is carried out by means of a linkage adapted to act in an antagonistic manner on the engagement means, said linkage being controlled by an actuator; the presence of a wear take-up device makes it possible to choose an actuator comprising maneuvering means with an electric motor, a mechanical transmission having an input element formed by the shaft of the electric motor, an output element for acting on the wheelhouse, elastic assistance means acting between a fixed part and an element of the transmission in an antagonistic manner with respect to the engagement means, the electric motor then providing only a small effort to disengage the clutch. Alternatively, the operating means can be of the hydraulic type. In general, the actuator comprises motor means provided with a mechanical transmission and elastic assistance means acting between a fixed part and an element of the transmission antagonistically with respect to the clutch means.

The elastic assistance means store the energy of the engagement means during the engagement operation of the clutch and restore it at the time of the disengagement operation; thus the electric motor provides only the difference between the effort of the engagement means and the effort of the elastic assistance means. Thanks to the wear take-up device, the stroke of the elastic assistance means is reduced, the holding is excellent and they can thus be installed conveniently in the actuator.

Advantageously, the wear take-up device being mounted within the clutch device, the elastic assistance means bear, on the one hand, on a fixed part and, on the other hand, on a part movable in translation and fixed in rotation, forming a nut which cooperates with the shaft of the electric motor forming a screw, said nut forming the output element of the mechanical transmission while being capable of acting on the wheelhouse. The elastic assistance means consist of a helical spring surrounding the nut or a series mounting of Belleville washers.

Of course, the nut can act either by pulling or by pushing on the linkage, which can conventionally comprise a declutching fork acting on the declutching stop; it can also include a hydraulic control having a hydraulic receiver whose piston acts on the clutch release bearing and a transmitter whose piston is controlled by the nut of the actuator.

Such arrangements are known and for example described in the French patent application filed on March 25, 1997 under the number 97 03 627.

Figures 1 and 2, described below, show such an arrangement. Such arrangements generally work well and are satisfactory.

However, certain malfunctions may appear, temporarily causing a loss of comfort; these malfunctions generally come from poor control of the position of the declutching member, such as the declutching stop; this poor control leads to docking at the different licking point, i.e. to a shift of the expected position of the licking point, more or less, relative to the actual licking point, in particular between the operations of wear compensation; in other words, the wheelhouse may be too long or too short; this results in jolts and / or shocks and / or noises. In addition, thermal constraints must be taken into account, resulting in increases in the thickness of the clutch components, the friction linings of which reach non-negligible temperatures.

To avoid these drawbacks, the invention proposes a friction clutch, in particular for motor vehicles, comprising, on the one hand, a clutch device comprising engaging means and declutching means, the engaging means bearing on a cover, integral a rotary drive wheel, for action on a pressure plate and tightening the friction linings a friction disc between the pressure plate and the flywheel, forming a reaction plate, and, on the other hand, a wheelhouse to act in an antagonistic manner on the engaging means by means of the declutching means, and a device for wear take-up, to compensate for the wear of at least the friction linings, the wear take-up device being mounted within the clutch device, characterized in that it comprises an actuator for controlling the wheelhouse , the actuator comprising motor means provided with a mechanical transmission and elastic assistance means acting between a fixed part and an element of the transmission in an antagonistic manner with respect to the engagement means and by the fact that means are provided for automatic length adjustment of the wheelhouse depending in particular on wear.

Advantageously, an actuator is provided to control the wheelhouse. Admittedly, it has already been proposed, for example in document FR-A-2 728 516, a hydraulic control provided with means for lengthening the wheelhouse; but, according to this document, this lengthening is not automatic, a certain number of operations being necessary.

Thanks to the invention, the increases in thickness of the components of the clutch, due to thermal stresses, are taken into account and the friction clutch works smoothly and / or shock and / or noise. According to a first embodiment, the wheelhouse comprises a hydraulic control which comprises a receiver having a piston and a transmitter having a piston; preferably, the piston, called control, of the transmitter is slidably mounted in a cylindrical chamber, called control, connected to a reservoir via an orifice and the end of the control chamber, opposite to the one in which the control piston is at rest is connected to the reservoir by means of a one-way valve which authorizes the liquid from the reservoir to go to the control chamber but which prevents the liquid contained in said chamber from returning to the reservoir .

Advantageously, said orifice passes through the cylindrical wall of the control chamber, is open when the control piston is at rest and closed by it during the declutching operation, the unidirectional valve being implanted in a conduit connecting the tank control.

Alternatively, the one-way valve is located inside the control chamber; advantageously, the orifice for communication of the control chamber with the reservoir is disposed in the partition which limits the control chamber and faces the control piston; preferably, the check valve of the one-way valve is coupled to the control piston so that, when the latter is in the rest position, the unidirectional valve is open while it is closed as soon as the latter has left its rest position.

Preferably, the orifice is bordered by the seat of the valve of the unidirectional valve and comprises a tail which extends axially until it passes through a hole made in a front partition of the control piston defined by an axial well which it presents. , a stop provided at the end of said tail being adapted to cooperate with the internal face of the partition of the control piston.

According to another embodiment, the wheelhouse comprises a jack comprising, on the one hand, a body in which is slidably sliding a piston which defines there an upstream chamber and a downstream chamber and, on the other hand, a slide valve adapted to communicate or isolate said chambers, said slide being, on one side, subjected to the action of a spring urging it into the isolation position and, on the other side, adapted to cooperate with a fixed part, the cylinder body being connected to the actuator and the piston being connected to the declutching member.

According to yet another embodiment, the wheelhouse is of the mechanical type and comprises a device comprising a nut displaceable axially in a housing under the action of the actuator, a connecting piece to the declutching member extending partially to the interior of the housing where it is surrounded by a radially elastic jaw, said jaw having a head having externally a semi-frustoconical bearing adapted to cooperate with a corresponding frustoconical inner bearing which has a cavity formed in the nut, said jaw being biased by a spring inside the cavity in the direction which makes the bearings cooperate; preferably, an assistance spring, bearing on the housing biases the nut axially in the direction of disengagement.

Whatever the embodiment, the wheelhouse may include a clutch release fork.

Preferably, one of the supports of the engagement means is axially offset and a compensation means, implemented by an actuating means, is provided to achieve this offset, said actuating means being controlled by a triggering means itself. - even controlled by a detection means, sensitive to the wear of the linings.

Advantageously, the offset support is the support linked to the pressure plate. Alternatively, the offset support is the support linked to the cover. To better understand the object of the invention, we will now describe, by way of example, purely illustrative and not limiting, embodiments shown in the accompanying drawings. In these drawings: - Figure 1 is a schematic sectional view of a clutch of the prior art;

- Figure 2 is a schematic view of the actuator associated with the clutch of Figure 1;

- Figure 3 is a view similar to Figure 1 of a clutch according to the invention;

- Figures 4 to 6 are sectional views of a variant of the transmitter according to the invention, the transmitter being shown at rest in Figure 4, at the start of declutching in Figure 5 and during re-engagement at Figure 6;

- Figure 7 is a schematic sectional view of an actuator forming part of the wheelhouse according to the invention;

- Figure 8 is a partial view of Figure 7 showing the cylinder of the cylinder in another position;

- Figure 9 is a view similar to Figure 7 and corresponding to a variant;

- Figure 10 is a view similar to Figure 3 showing a variant of the wheelhouse according to the invention;

- Figures 11 to 14 are partial views on a larger scale of the wheelhouse of Figure 10 shown in different positions: clutch engaged, Figure 11; clutch disengaged, Figure 12; start of a re-clutch operation, figure 13, and end of this operation, figure 14, the linings being partly worn.

The clutch device 10 in FIG. 1 is of the type described in document FR-A-2 753 503 to which reference will be made for more details, knowing that here in FIG. 1 everything is shown diagrammatically; in this figure, the clutch device 10 comprises a flywheel 11 for driving in rotation, a friction disc 12 carrying at its outer periphery friction linings 13, a pressure plate 14, a cover 15 fixed to the flywheel 11 , a diaphragm 16 acting between, on the one hand, the cover 15 and, on the other hand, the pressure plate 14, here by means of support means 17, and a wear take-up device 18 comprising ramp means 19 carried by the pressure plate 14. The disc 11 here comprises an elastic support carrying the linings 13 for forming a progressive disc as described in document GB-A-2 294 301.

The flywheel 11 possibly divided, as visible in FIGS. 35 to 37 of the document GB-A-2 294 301, here forms a reaction plate offering dorsally a face friction to a friction lining 13; the steering wheel 11 is integral in rotation with a first shaft, such as a driving shaft.

The pressure plate 14 has frontally a friction face for the other friction lining 13; dorsally, it has studs 24 intended to cooperate with ramps 25 belonging to the ramp means 19 here consisting of a ring having the ramps 25 inclined and distributed circumferentially; the ring 19 is here metallic and has support zones constituting the support means 17 for the diaphragm 16, here for the outer periphery of the Belleville washer thereof; it also has at its outer periphery a toothing 26. The pressure plate 14 is integral in rotation with the cover 15 here of hollow shape with a centrally perforated bottom, and this with axial mobility by means of elastic tongues, not shown, exerting a return function of the pressure plate 14 towards the bottom of the cover 15 carrying columns, not visible in the figure, with a profiled head for pivoting mounting of the diaphragm 16, more precisely from the internal periphery of the Belleville washer of the diaphragm 16, on the cover 15, the bottom of which has, opposite the profiled heads of the said columns forming a secondary support, another support, called the primary support, formed for example by stamping its bottom.

The friction disc 12 has, at its internal periphery, in known manner, a hub 27 internally grooved for its connection in rotation to a second shaft, such as a driven shaft.

In the case of an application to a motor vehicle, the first shaft here is the crankshaft of the engine on which the flywheel 11 is fixed carrying the pressure plate 14, the cover 15 and by pinching the friction disc 12 including the central hub 27 is here linked in rotation to the input shaft of the gearbox constituting the second shaft and this disengageably, the friction linings 13 being normally clamped between the pressure plate 14 and the flywheel 11. The torque is thus transmitted from the crankshaft to the input shaft of the gearbox. The clutch is therefore normally engaged. The declutching operation is carried out by means of a wheelhouse adapted to act in an antagonistic manner on the diaphragm 16.

Here, the wheelhouse has hydraulic control; this comprises, on the one hand, a receiver 20, the piston 21 of which acts, directly or by means of a declutching fork, on the declutching stop, the piston 21 which can, as shown here, constitute itself even the clutch release bearing, and, on the other hand, a transmitter 30 whose piston 31 is controlled by an actuator 40. The piston 31, said control, of the transmitter 30 is slidably mounted in a cylindrical chamber 32, said control, connected to a reservoir 41 via an orifice 42 which passes through its cylindrical wall; the piston 30 of the transmitter 31 is biased by a return spring 33 towards a rest position in which said orifice 42 is free, then putting the control chamber 32 into communication with the reservoir 41.

The piston 21 of the receiver 20 is slidably mounted in a cylindrical chamber 22, called the receiving chamber, connected to the control chamber 32 by a pipe 43; the piston 21 of the receiver 20 is biased by a spring 23 said application applying the piston 21 of the receiver 20 in application against the clutch release bearing or the clutch release fork, here against the fingers of the diaphragm.

The clutch is therefore normally engaged. To disengage the clutch, it is necessary, using the piston 21 of the receiver 20, to act on the internal end of the fingers of the diaphragm 16 to rotate the latter around the balusters in order to gradually cancel the load which it exerts. on the pressure plate 14, more precisely on the support means 17. The elastic tabs, usually of tangential orientation, then recall the pressure plate 14 in the direction of the bottom of the cover 15 to release the friction linings 13. L clutch is then disengaged. By releasing the action exerted by the piston 21 of the receiver 20 on the diaphragm 16, the clutch then passes from its disengaged position to its engaged position, in which the diaphragm 16 is in contact with the primary support carried by the bottom. cover 15.

The piston 21 of the receiver 20 therefore acts antagonistically on the diaphragm 16 while being controlled by the actuator 40.

During the lifetime of the clutch, the friction linings 13 wear out as well as, to a lesser extent, the friction faces of the pressure plate 14 and of the flywheel 11.

The pressure plate 14 therefore approaches the flywheel 11. As is known, the diaphragm 16 in the free state has a frustoconical shape; once mounted in the clutch device, its taper varies.

In general, the characteristic curve of the diaphragm is a function of its dimensions, its thickness and the height of the truncated cone of its washer part.

Beautiful city. Its characteristic curve (load exerted - deflection) conventionally has an increasing pace until a maximum, then a decreasing pace until a minimum to then increase. In the engaged clutch position, new friction linings 13, the diaphragm 16 occupies a position corresponding to a point on the decreasing part of its characteristic curve. Depending on the wear of the friction linings, the operation approaches the maximum of the characteristic curve, then exceeds this maximum,. the load exerted by the diaphragm then decreasing until it can no longer transmit the engine torque. Depending on the wear above, its inclination varies. The role of the wear take-up device 18 is to keep the diaphragm 16 always in the same position when the clutch is engaged and therefore to at least compensate for the wear of the friction linings 13.

Generally, a declutching stop is capable of acting on the internal end of the fingers of the diaphragm 16. This stop is slidably mounted along a guide tube secured to the gearbox. The guide tube is internally traversed by the input shaft of the gearbox.

The stop can be subjected to the action of a clutch release pivotally mounted on a fixed part of the vehicle, such as the gearbox housing. The free end of the fork is subjected to the action of the piston 21 of the receiver 20.

Depending on the location of the receiver 20 relative to the free end of the fork, the latter acts by pushing or pulling on the latter, depending on the type of clutch. In fact, in general, the clutch instead of being of the pushed type like that of FIG. 1 - the clutch release bearing acting by pushing on the diaphragm 16 to disengage the clutch - said clutch can be of the type pulled - the clutch release bearing then acting by pulling on the inner end of the fingers of the diaphragm 16 to disengage the clutch. In this case, the external peripheral part of the Belleville washer of the diaphragm 16 is supported on the cover 15, while the internal periphery of said Belleville washer is then supported on the support means 17 carried by the pressure plate 14.

Conventionally, the release bearing comprises a ball bearing with, on the one hand, a rotating ring in direct contact with the diaphragm 16 in the case of a clutch of the pushed type or in indirect contact with the diaphragm 16 by l 'through a docking piece located behind the diaphragm 16 in the case of a clutch of the pulled type and, on the other hand, a non-rotating ring coupled, for example by a self-centering spring or a cover, to an operating sleeve subjected to the action of a control member, such as the clutch release fork, acting by pushing or pulling, as the case may be, on said sleeve. A preload spring usually acts to keep the clutch release bearing on the diaphragm in constant contact, in the manner of the application spring 23 of the receiver 20 of the diagram in FIG. 1.

The wear take-up device 18 includes means for detecting the wear of the friction linings 13 (and to a lesser extent the wear of the plate. pressure 14 and flywheel 11) associated with drive means for rotating the support means 17, usually when the clutch is in the disengaged position.

The detection means may comprise a pin carried by friction, for example by the pressure plate 14, to cooperate with the flywheel 11 or the cover 15. This pin is associated with elastic means, for example coil springs, making it possible to 'Rotate the support means 17 in the event of wear, and this when the clutch is disengaged. Various configurations are possible.

Here, the detection means comprise a blade carried by the cover 15 cooperating with the inclined teeth of a ratchet wheel secured to an axis which also slidingly carries a worm 28. The thread and the pitch of the worm end 28 are adapted to the toothing 26 carried by the ring 19 and form an irreversible system, the worm 28 being able to move the toothing 26, but not the reverse. Said axis is carried by a support which also carries a helical catching spring, forming elastic catching means, surrounding the axis; a non-return pawl is adapted to cooperate with the teeth of the ratchet wheel.

For more details concerning the wear take-up device 18, it suffices to refer to the document FR-A-2 753 503 already cited.

In the event of wear, the diaphragm tilts and acts on the blade so that the ratchet wheel approaches the blade adapted to rotate the ratchet wheel and to arm the catch-up spring following some wear, the blade then jumping a tooth.

The take-up spring is charged when the clutch is engaged following wear detection. In the disengaged clutch position, the armed take-up spring is then, when its load is sufficient to overcome friction, caused to rotate the worm 28 then causing the ring 19 to rotate, which, by cooperation of the ramps 25 with the studs 24 - which can be replaced as a variant by ramps complementary to the ramps 25 - of the pressure plate 14, moves axially so that the bearing zones approach the bottom of the cover 15 to maintain the diaphragm 16 in a substantially constant position when the clutch is engaged.

The thickness is therefore increased between the support means 17 and the friction face of the pressure plate 14 in contact with the friction linings 13 of the friction disc 12.

Thus, the wear take-up device 18 comprises an endless screw 28 mounted to slide along its axis while being subjected to the action of an elastic take-up means. It is when the endless screw 28 is moved along its axis, by the action of the compressed take-up spring during the detection of wear, that it drives in rotation circumferential the ramp means 19, the load of the elastic catch-up spring increasing with the wear of the friction linings 13, the axial displacement being obtained by action of the spring when its load is sufficiently high to rotate the ring 19 and overcome the friction due to the return force due to the elastic tongues for rotationally connecting the pressure plate 14 with the cover 15 acting on the ring

19 to urge the latter in contact with the diaphragm, the clutch being disengaged. The ratchet wheel and the blade constitute rotational drive means made operational by the wear of the friction linings 13 when the clutch is engaged. The non-return pawl prevents the endless screw 28 from turning in the opposite direction to that in which it is rotated by the rotational drive means when they are made operational.

The implantation of the wear take-up device 10 within the clutch device makes it possible to simplify the actuator 40 consisting, FIG. 2, of an electric motor 150, a mechanical transmission 60 and elastic assistance means 70.

The electric motor 150 thus drives the mechanical transmission 60 according to a stroke independent of the wear of the friction linings 7 and / or of the plate 1 and of the flywheel 2.

This race is always the same. The elastic assistance means 70 allow the electric motor 150, in a manner known from document FR-A-2 564

920, to develop only a weak effort. These elastic means 70, in the manner of an elevator, store the energy of the diaphragm 16 during the passage of the latter from its disengaged clutch position to its clutch engaged position (that is to say during the engagement of clutch) and restores it when disengaging (change from clutch engaged position to disengaged clutch position).

The elastic assistance means 70 therefore act antagonistically with respect to the diaphragm 16.

In the engaged clutch position, the elastic assistance means 70 do not exert force or a weak force on the wheelhouse and therefore on the diaphragm 16. This is possible throughout the life of the clutch because the diaphragm 16, thanks to the wear take-up device 18, always occupies the same position. As is known, the power supply terminals of the electric motor 150 are connected to an electronic module located outside the actuator 40 or alternatively partly in the actuator.

This module comprises for example a microcomputer, such as a microprocessor, information processing circuits and, for example, power transistors mounted in series to control the motor in both directions of rotation. The electronic module belongs to an electronic circuit comprising a certain number of sensors sending information to the electronic module.

These sensors capture in particular the speed of the driving (crankshaft) and driven (input shaft of the gearbox) shafts, the actuator stroke, the condition of the gearbox (gear engaged), l state of the gear shift lever (force sensor) and others.

From this various information, a strategy for clutch and declutching operations is developed. The rotary motor 50 is therefore only energized for very short moments (declutching operation) and therefore consumes very little energy supplied here by the vehicle battery. Its power is very low thanks to the elastic assistance means 70. All of this makes it possible to have a light electromechanical actuator 40.

The elastic assistance means 70 bear on a fixed part and on a mobile part forming a nut as described below.

Here the actuator comprises a flange 91 on which the electric motor 150 is fixed, for example using screws (we see in Figure 2 the axis of the screws).

This flange 91 carries at its internal periphery a fixed support 79, here rounded, of annular shape and a ball bearing 52 carrying the output shaft 51 of the electric motor. This flange 91 is therefore perforated centrally for passage of the shaft 51 and is shaped to form a bearing support.

The output shaft 51 of the electric motor 150 is thus, in known manner, fixed in translation and mobile in rotation when the motor is electrically powered.

The flange 91 is integral with a housing 90 having at its rear end a sleeve 64 provided with a guide groove 65. More precisely, the flange 91 constitutes a cover for the housing 90 of hollow form and is fixed on the front end open of the housing 90, the bottom 66 of which is perforated centrally and carries the sleeve 64.

The housing 90 - flange 91 assembly forms a fixed casing and is fixed to a fixed part of the vehicle, for example the casing of the gearbox. The housing 90 or the flange 91 has for this purpose non-visible ears.

The shaft 51 has a threaded end and constitutes the input element of the mechanical transmission 60. The shaft 51 is engaged with a nut 61 of tubular shape. This nut 61 includes an annular movable support 78, here rounded, carried by a radially projecting collar 68 capable of coming into abutment against the bottom 66 of transverse orientation of the housing 90; an annular skirt 67 of axial orientation extends the bottom 66. The nut 61 is fixed in rotation and axially movable.

Here four Belleville washers 71 to 74 mounted in series are provided. Force transmission means 75 to 77 intervene between the external and internal peripheries of the adjacent Belleville washers. The washers 71 to 74 are capable of being crossed by the output shaft 61.

More precisely, in axial succession, the Belleville washer 71 at the rear end bears on its internal periphery on the movable support 78 and on its external periphery on a rod 75 in intimate contact with the internal periphery of the skirt 67. The second washer Belleville 72 is supported at its outer periphery on the rod 75 and at its internal periphery on a rod 77 carried by a sleeve 177 sliding along the smooth and cylindrical external periphery, here stepped, of the nut 61 internally threaded. The third Belleville washer 73 bears on its internal periphery on the rod 77 and on its external periphery on a rod 76 in intimate contact with the internal periphery of the skirt 67; the Belleville washer at the front end 74 bears on its outer periphery on the rod 76 and on its internal periphery on the fixed support 79.

In the engaged clutch position (upper part of the figure), the Belleville washers 71 to 74 have a generally planar configuration and are bandaged.

During the clutch release operation, these Belleville washers relax to counterbalance the action exerted by the diaphragm on the clutch release bearing. The electric motor driving the shaft 51, fixed in translation, the nut 61, fixed in rotation and driven by the shaft 51 forming a screw, moves in translation axially in the direction of the bottom 66 of the housing 90 until the collar 68 comes into abutment on said bottom, by moving in its movement the piston 31 of the transmitter 30.

In this position, the clutch is disengaged and the Belleville washers 71 to 74 have an inclined position thus generally forming a W.

During the clutch operation, under the action of the diaphragm 16, the Belleville washers return to their initial plane position.

Rotary connection means 63, 65 exist between the housing 90 and the nut 61 forming the output element of the mechanical transmission 60. The nut 61 thus performs a translational movement while being linked in rotation to the housing 90.

The rotational connection means here consist of a key 63 carried by the nut 61 engaging in the groove 65 of the sleeve 64 for guiding the nut 61. As a variant, as described in FIGS. 9 and 10 of the document FR -97 03627 cited above, the assistance spring consists of a coil spring surrounding the nut bearing on the fixed support and a collar secured to the nut. These arrangements, if they work well, can lead to certain malfunctions, as already mentioned above. To compensate for this, with reference to FIG. 3, it can be seen that, according to the invention, the end of the control chamber 32, opposite to that where the control piston 31 is at rest, is connected to the reservoir 41 by a conduit 29 on which is placed a one-way valve 50 which authorizes the liquid from the reservoir 41 to go towards the control chamber 32 but which prohibits the liquid contained in the control chamber 32 from returning to the reservoir 41.

Here, the unidirectional valve 50 includes a valve 51 cooperating with a seat 52 towards which it is biased by a spring 53. Thanks to this arrangement, during re-engagement, after the wear take-up device has operated, while it returns to its rest position, the control piston 31 creates a depression in the control chamber 32, the valve 51 takes off from its seat 52, against its spring 53, weak, and a portion of liquid from the reservoir 41 s flows to the control chamber 32 via the conduit 29. Of course, during the declutching operation, the pressure of the liquid in the control chamber 32 presses the valve 51 on its seat 52, the unidirectional valve 50 then being closed .

An automatic lengthening of the wheelhouse was thus carried out. Figures 4 to 6 show an alternative layout of the one-way valve.

Here, the unidirectional valve is located inside the control chamber 32.

More specifically, the orifice 42 for communication of the control chamber 32 with the reservoir 41 is disposed in the partition 37 which limits the control chamber 32 and which faces the control piston 31, in the axis thereof. ; the orifice 42 is bordered by the seat 52 of the valve 51 of the unidirectional valve 50.

The valve 51 has a tail 54 which extends axially until it passes through a hole 36 formed in a front partition 35 of the control piston 31, said partition 35 being defined by an axial well 34 which the control piston 31 presents; at the end of the tail 54 of the valve 51 is provided a stop 55 adapted to cooperate with the inner face of the partition 35 of the control piston 31; the length of the tail 54 of the valve 51 is such that, when, under the action of its return spring 33, the control piston 31 is in its rest position, it lifts the valve 51 from its seat 52 by cooperation of its partition 35 with the stop 55: thus, in this position, which is shown in Figure 4, the control chamber 32 is in communication with the reservoir 41, the orifice 42 being open.

During the declutching operation, FIG. 5, the pressurization of the control chamber 32 closes the one-way valve 50. During the re-clutching, after the wear take-up device has operated, while it returns to in its rest position, the control piston 31 creates a depression in the control chamber 32 and the valve 51 takes off from its seat 52, FIG. 6.

FIG. 7 schematically shows in section a jack 100 forming part of a variant of the declutching linkage according to the invention; this cylinder 100 comprises a cylindrical body 101 in which is made to slide in leaktight manner a piston 102 which defines there two chambers, a so-called upstream chamber 103 and a so-called downstream chamber 104. The jack 100 also includes a valve 105 called a slide transfer valve to which the chambers 103 and 104 are connected by channels 106 and 107, respectively; the drawer 108 is adapted to occupy at least two positions, a position, FIG. 7, in which the channels 106 and 107, therefore the chambers 103 and 104, communicate, and a position, FIG. 8, in which this communication is interrupted; the drawer 108 is on one side subjected to the action of a spring 109 which tends to place it in the position it occupies in FIG. 8; on the other side, the drawer 108 has a tail 110 which passes through the body of the valve 105 from which it emerges, being adapted to cooperate in abutment with a fixed part 111.

The body 101 of the jack 100 is connected by a link 112 to the actuator, for example to the nut 61 of the actuator 40 of FIG. 2; the piston 102 is connected by a link 113 to the declutching member, the declutching fork for example; thus, the cylinder 100 is placed in series on the constituent elements of the wheelhouse and moves with it. The cylinder 100 is filled with a liquid, such as oil or the like; we understand that when the drawer 108 is in the position of Figure 8, the wheelhouse is of the rigid type; the piston 102 is subjected to the action of a spring 114 acting in the direction of increasing the volume of the upstream chamber 103, that is to say in the direction of increasing the length of the wheelhouse. As the cylinder 100 is shown, here to act in the direction of disengaging the clutch, the wheelhouse, therefore the cylinder 100 as a whole, must be moved in the direction of the arrow F, FIG. 7, that is ie from right to left in relation to this figure.

The operation is as follows. In FIG. 7, the wheelhouse is at rest, clutch engaged; in this position, the tail 110 of the drawer 108 cooperates in abutment with the fixed part 111 so that the chambers 103 and 104 communicate; thanks to the spring 114, the piston 102 abuts on the fingers of the diaphragm 16 via the connection 113 to the declutching member. When disengaging, the cylinder 100 is moved along arrow F by the actuator, via the link 112; in this movement, the tail 110 of the drawer 108 leaves the support on the fixed part 111 and the spring 109 moves the drawer into the position, FIG. 8, where the channels 106 and 107 no longer communicate: the wheelhouse then being rigid, the the clutch release operation takes place normally. Upon re-engagement, the tail 110 of the drawer 108 regains its support on the fixed part

111 and rooms 103 and 104 communicate again; if there has been wear, the diaphragm 16 pushes the piston 102 inside the body 101 of the jack 100, in the opposite direction to that of the arrow F.

As can be seen, the length of the wheelhouse is automatically adjusted according to wear.

If the clutch is of the opposite type from that which has just been described, for example of the type pulled instead of pushed, a cylinder 100 of the kind of the previous one, certain structures of which have been reversed can be used, as shown in FIG. 9 on which the same references have been assigned to the constituents playing the same role as above. Figures 10 to 14 show a variant of the invention.

In Figure 10, the clutch device 10 is similar to that of Figure 1; here, a clutch release bearing 220 is adapted to cooperate with the end of the fingers of the diaphragm 16 by being actuated by a clutch release lever 222 articulated at 221 on a fixed part; the end 223 of the fork 222, opposite to that by which the fork 222 cooperates with the stop 220, is connected by the connecting piece 213 to a device 200 for automatic lengthening of the wheelhouse; disengagement is obtained by moving the end 223 of the fork 222 in the direction of arrow F, FIG. 10; the device 200, forming part of the declutching linkage, better visible in FIGS. 11 to 14, comprises a cylindrical body 201 in which is moved a nut 261 of tubular shape, fixed in rotation and axially movable, engaged with the tree

51, fixed in translation and mobile in rotation, of the electric motor 150. The nut 261 has for example in radial projection at least one tenon sliding axially in a groove of the body 201 forming a mortise.

The connecting piece 213 partially extends inside the body 201 where it is surrounded by a jaw 214. The jaw 214 is a globally cylindrical elastic piece radially thanks to a longitudinal slot 216 which it has; the jaw 214 has a head having externally a semi-frustoconical bearing surface 215 cooperating with a corresponding frustoconical inner bearing surface 265 which has a cavity 262 formed inside the nut 261; this cavity 262 communicates with the interior of the body 201 through an opening 263 traversed by the tail of the jaw 214; the latter is permanently stressed with respect to the nut 261 in the direction which makes the bearing surfaces, on the one hand, 215 of the head of the jaw 214 and, on the other hand, 265 of the nut 261, cooperate, thanks to a spring 266 placed inside the cavity 262 between the jaw 214 and the transverse bottom of the cavity 262. A sort of mandrel has thus been formed capable of tightening the connecting piece 213; to reinforce the grip of the jaw 216, it is possible to provide indentations on the internal cylindrical surfaces of the jaw 216 and the external of the connecting piece 213.

On the side opposite to the opening 263, the cavity 262 also communicates with the interior of the body 201 by a bore 267 internally threaded by which the nut 261 is mounted on the shaft 51, externally threaded, of the motor 50; advantageously, the diameter of the spring 266 is greater than that of the bore 267.

As in the variant of FIG. 2, a spring 270 for assisting with declutching is provided: here, the spring is a helical spring placed between the nut 261 and the bottom of the housing 201 opposite the electric motor 150. The operation is the next.

Figure 11 corresponds to the engaged state of the clutch device 10, new linings 13 for example; the ring 220 is in contact with the fingers of the diaphragm 16; the nut 261 is in a position such that the tail of the jaw 214 is in abutment on the transverse wall of the body 201, the frustoconical bearing surfaces 215 and 265 at a distance from each other, the springs 266 and 270 compressed; consequently, the jaw 214 is slightly open radially and the connecting piece 213 is axially free relative to the device 200, its position being indexed on the position of the fingers of the diaphragm 16.

To disengage, the electric motor 150 is energized and rotates in the direction which moves the nut 261 in the direction of the arrow F, to the right with respect to the figures; after taking up the clearance between the frustoconical bearing surfaces 215 and 265, thanks to the action of these and of the spring 266, the jaw 214 tightens the connecting piece 213 which is then driven by the nut 261, causing in its movement l end 223 of the fork 222 in the direction of the arrow F in FIG. 10; it is this disengaged position which is shown in Figure 12; it will be noted that here also the spring 270 assists the electric motor 150 to move the nut 261 in the direction of disengagement. During the next re-clutch operation, the nut 261 is moved in the opposite direction to that of arrow F; at first, figure 13, the tail of the jaw 261 abuts on the body 201, then, at a second time, figure 14, the nut 261 continuing its race, the frustoconical bearing 265 moves away from the frustoconical bearing 215 of the jaw 214 and the connecting piece 213 is released; if there is wear of the linings 13, the diaphragm 16 tilts further and pushes the ring 220 to the right of FIG. 10; the end 223 of the fork 222 is then moved to the left, driving the connecting piece 213 which is also moved to the left: such displacement of the connecting piece 213 has been identified at 217 in FIG. 14. Thus, thanks to device 200, the length of the wheelhouse is automatically adjusted according to wear.

Thanks to the invention an automatic lengthening of the mounting on the vehicle is carried out.

The means of automatic length adjustment of the wheelhouse can be placed in the actuator, in the stop, in the fork 222, anywhere in the wheelhouse.

These means are also sensitive to occasional increases in thicknesses due essentially to thermal stresses occurring in the clutch, in particular at the level of the flywheel, the pressure plate and the friction disc. The actuator can act on the clutch pedal as described in the document

JP-A-20526 from 1979

A clutch pedal can therefore be provided.

Claims

1. Friction clutch, in particular for motor vehicles, comprising, on the one hand, a clutch device comprising engaging means and declutching means, the engaging means bearing on a cover (15), integral with a flywheel ( 11) rotational drive, for action on a pressure plate (14) and tightening of the friction linings (13) of a friction disc (12) between the pressure plate (14) and the flywheel (11) , forming a reaction plate, and, on the other hand, a wheelhouse to act in an antagonistic manner on the engagement means via the declutching means (3), and a wear take-up device (18), to compensate for the wear of at least one friction lining (13), the wear take-up device being mounted within the clutch device, characterized in that it comprises an actuator (40) for controlling the wheelhouse, actuator comprising motor means provided with a mechanical transmission and elastic assistance means acting between a fixed part and an element of the transmission in an antagonistic manner with respect to the engagement means and by the fact that means are provided for automatic lengthening of the wheelhouse as a function in particular of wear.

2. Friction clutch according to claim 1, characterized in that the wheelhouse comprises a hydraulic control which comprises a receiver (20) having a piston (21) and a transmitter (30) having a piston (31).

3. Friction clutch according to claim 2, characterized in that the piston (31), said control, of the transmitter (30) is slidably mounted in a cylindrical chamber (32), said control, connected to a reservoir (41) by means of an orifice (42) and the end of the control chamber (32), opposite to that where the control piston (31) is at rest, is connected to the reservoir (41 ) by means of a one-way valve (50) which allows the liquid from the reservoir (41) to go towards the control chamber (32) but which prevents the liquid contained in said chamber (32) from returning to the reservoir (41 ).

4. Friction clutch according to claim 3, characterized in that said orifice (42) passes through the cylindrical wall of the control chamber (32), is opened when the control piston (31) is at rest and closed by that -ci (31) during the declutching operation, the unidirectional valve (50) being located in a conduit (29) connecting the control chamber (32) to the reservoir (41).

5. Friction clutch according to claim 3, characterized in that the unidirectional valve (50) is located inside the control chamber (32).

6. Friction clutch according to claim 5, characterized in that the orifice (42) for communication of the control chamber (32) with the reservoir (41) is arranged in the partition (37) which limits the control (32) and faces the control piston (31).

7. Friction clutch according to one of claims 5 or 6, characterized in that the valve (51) of the one-way valve (50) is coupled to the control piston (31) so that, when the latter ( 31) is in the rest position, the one-way valve (50) is open while it is closed as soon as the latter (31) has left its rest position.

8. Friction clutch according to claim 7, characterized in that the orifice

(42) is bordered by the seat (52) of the valve (51) of the one-way valve (50) and comprises a tail (54) which extends axially until it passes through a hole (36) made in a partition (35 ) front of the control piston (31) defined by an axial well (34) which it has, a stop (55) provided at the end of said tail (54) being adapted to cooperate with the internal face of the partition ( 35) of the control piston (31).

9. Friction clutch according to claim 1, characterized in that the linkage comprises a jack (100) comprising, on the one hand, a body (101) in which is made to slide in sealed manner a piston (102) which there defines an upstream chamber (103) and a downstream chamber (104) and, on the other hand, a valve (105) with drawer (108) adapted to communicate or to isolate said chambers (103, 104), said drawer ( 108) being, on one side, subjected to the action of a spring (109) urging it into the isolation position and, on the other side, adapted to cooperate with a fixed part (111), the body (101) of the jack (100) being connected (112) to the actuator and the piston (102) being connected (113) to the declutching member.

10. Friction clutch according to claim 1, characterized in that the linkage is of the mechanical type and comprises a device (200) comprising a nut

(261) axially movable in a housing (201) under the action of the actuator, a connecting piece (213) to the declutching member extending partially inside the housing (201) where it is surrounded by a radially elastic jaw (214), said jaw (214) having a head having externally a semi-frustoconical bearing surface (215) adapted to cooperate with a corresponding frustoconical internal bearing surface (265) which has a cavity (262) formed in the nut (261), said jaw (214) being biased by a spring (266) inside the cavity (262) in the direction which makes the bearing surfaces (215,265) cooperate.

11. Friction clutch according to claim 10, characterized in that a spring (270) assistance, bearing on the housing (201) biases the nut (261) axially in the direction of disengagement.

12. Friction clutch according to one of claims 1 to 11, characterized in that the wheelhouse includes a clutch release fork.

13. Friction clutch according to one of claims 1 to 12, characterized in that one of the supports of the engagement means is axially offset and a compensation means is provided to achieve this offset in association with an actuator means allowing the implementation of the compensation means, and a triggering means itself controlling the actuation means, a detection means, sensitive to the wear of the linings, acting on one of the compensation means, actuation and release.

14. Friction clutch according to claim 13, characterized in that the offset support is the support linked to the pressure plate.

15. Friction clutch according to claim 13, characterized in that the offset support is the support linked to the cover.