GB2264989A

GB2264989A - Friction clutch

Info

Publication number: GB2264989A
Application number: GB9304616A
Authority: GB
Inventors: Paul Maucher
Original assignee: LuK Lamellen und Kupplungsbau GmbH
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 1992-03-10
Filing date: 1993-03-05
Publication date: 1993-09-15
Anticipated expiration: 2013-03-05
Also published as: RU2238451C2; BR9301117A; JPH0642553A; GB2264989B; FR2688559B1; GB9304616D0; JP3437598B2; DE4345577B4; GB9611669D0; FR2688559A1

Abstract

A friction clutch, more particularly for motor vehicles, has a pressure plate 3 which is connected rotationally secured but axially displaceable to a limited extent to a housing 2, and between the housing and pressure plate there is at least one operating means 4b and an energy accumulator formed by a diaphragm spring 4 by which the pressure plate can be biased in the direction of a clutch disc 8. The disc can be clamped between the pressure plate and a counter pressure plate 6, such as a flywheel, and an adjustment device is provided which compensates at least for the wear on the friction linings 7 of the clutch disc 8. The adjustment device comprises a wear compensating unit 16 which is provided between the operating means 4b or energy accumulator 4 and pressure plate 3 and which carries out an axial adjustment between the operating means or energy accumulator and pressure plate corresponding to the wear of the linings. On reaching the adjustment corresponding to the actual state of wear of the friction linings 7, the wear compensation unit is restricted in its adjustment function by means 17 provided on the pressure plate 3. The unit 16 includes spring-loaded wedges (FIG 3) and the means 17 includes a pair of leaf springs 22 in a slit 21. <IMAGE>

Description

Friction clutch The invention relates to a friction clutch, more particularly for motor vehicles with a pressure plate which is connected rotationally secured but axially displaceable to a restricted amount to a housing, wherein between the housing and pressure plate there is at least one operating means and an energy accumulator by which the pressure plate can be biased in the direction of a clutch disc which can be clamped between this pressure plate and a counter pressure plate such as a flywheel, wherein an adjustment device is provided which compensates at least the wear on the friction linings of the clutch disc.

Self-adjusting clutches wherein an adjustment is carried out according to the wear on the linings are known, for example from DE PS 29 20 932 and DE-OS 35 18 781.

With these clutches the wear adjustment is carried out by an axially displaceable support pad between the pressure plate and plate spring, wherein the support pad is supported on the pressure plate by ramps and is adjusted by rotation in the circumferential direction relative to the pressure plate towards the plate spring or by corresponding displacement of wedges which engage between inclined faces on the pressure plate or support pad.

In order to detect the state of wear on the linings in both designs there are several sensor elements which act between the pressure plate and the flywheel or clutch cover and which when the clutch is closed are adjusted corresponding to the wear on the linings and when the clutch is disengaged restrict the lift of the pressure plate to a definite value.

From this it emerges that when the clutch is new during disengagement of the clutch the plate spring carries out exactly the same lift movement in the area of the support pad as the pressure plate. When wear starts to appear on the linings the pressure plate moves in the direction of the flywheel. With this state of wear the plate spring in the area of the support pad must make a greater path than the pressure plate increased by the wear so that the support pad can be adjusted axially in the direction of the plate spring corresponding to the play which then ensues.

An adjustment of this kind cannot operate reliably in practice since the lift movement of the plate spring itself spreads relatively severely with a constant disengagement path on the plate spring tongues and furthermore very severe mean variations in the disengagement path occur on the disengagement bearing. In addition faults can occur when setting the disengagement system, eg in the case of a mechanical disengagement system for example, by setting too little play or too much pretension between the disengagement lever and plate spring. Quite different operating points thereby arise for the clutch.

When using a self-adjusting disengagement system eg a hydraulic system with transmitter and receiver cylinder, the system cannot in general function since the same disengagement path always occurs on the clutch throughout the service life and is not in general adjusted if the lift movement of the plate spring in the area of the support pad is smaller or equal to the movement of the pressure plate.

If however the plate spring makes a larger lift movement than the pressure plate then during each disengagement operation adjustment is made independently of the wear on the linings and the clutch would be totally displaced after a shorter time.

A further problem of the known self-adjusting clutches lies in the fact that the pressure plate can be activated by inherent resonance vibrations and thereby lifts axially from the plate spring whereby the adjustment device can completely displace the clutch.

The object of the present invention is to provide a friction clutch of the kind described at the beginning with an adjustment device which is improved compared to the prior art. The adjustment device is to be simple in construction and require only a small installation space. Furthermore the friction clutch should be simple and economical to produce.

According to the invention this is achieved in that between the operating means provided for engaging and disengaging the friction clutch, and the pressure plate or between the energy accumulator and the pressure plate there is a wear compensation unit which causes a practically constant force biasing of the pressure plate through the energy accumulator by making an axial adjustment corresponding to the state of wear of the friction linings between the operating means or energy accumulator and pressure plate through an adjustment corresponding to the wear, wherein on reaching the setting corresponding to the actual state of wear of the friction linings, the wear compensation unit is restricted or blocked in its adjustment function by means provided on the pressure plate.Thus according to the invention means are provided on the pressure plate which restrict the adjustment of the compensation unit beyond the wear path which has actually arisen wherein the wear adjustment and the restriction of this adjustment are carried out during a clutch disengagement process.

It can be particularly advantageous for the functioning and construction of the friction clutch if an axially tensioned plate spring is provided between the housing and pressure plate which can swivel about a ring-like support supported by the housing and which has a ring-like foundation body forming the energy accumulator from which radially inwardly extending tongues emerge in order to form the operating means.

The restricting means of the compensation device can be simply formed by at least one wear sensor which has at least one sensor component which can be moved relative to the pressure plate and which by abutting an axially fixed component limits the disengagement path of the pressure plate. The axially fixed component can thereby be formed by the clutch housing or the counter pressure plate.

Advantageously the sensor component is designed and mounted on the pressure plate so that a practically constant disengagement path of the pressure plate opposite the housing is maintained throughout the service life of the friction clutch.

In order to ensure a satisfactory compensation of the lining wear it can be particularly advantageous if the sensor component is held axially displaceable relative to the pressure plate. To this end the sensor component can be connected either directly or indirectly to the pressure plate by an automatic or independent adjustment unit and can be displaced opposite the pressure plate according to the wear on the lining by contacting at least one axially fixed component. This displacement preferably takes place during an engagement process. The contact area for the sensor component can be provided on the clutch housing and/or on the counter pressure plate.The compensation unit can be relaxed during a disengagement process by the wear sensor contacting the corresponding axially fixed component whereby in the event of wear on the linings the compensation unit can be adjusted until this adjustment is restricted by the interaction of an adjustment element of the compensation unit with the sensor component.

Advantageously several wear sensors are provided spread out over the circumference of the pressure plate and in the disengaged state of the friction clutch guarantee an impactfree positioning of the pressure plate relative to the axis of rotation of the friction clutch.

Advantageously the sensor component parts can have a contact area which interacts with a counter contact area of a compensation component or an adjustment element of the compensation device during disengagement of the friction clutch. The sensor components which ensure a constant lift of the pressure plate can advantageously be connected to the pressure plate by an automatic or independent adjustment device. An adjustment device of this kind can be produced for example by means of a friction-locking connection between the sensor component and the pressure plate wherein on exceeding a specific force during an engagement process the friction lock is overcome whereby the sensor component is adjusted relative to the pressure plate corresponding to the actual wear which has occurred.The adjustment device can however also be carried out by a freewheel-like device which allows during an engagement process an adjustment of the sensor component relative to the pressure plate whilst during disengagement of the friction clutch the sensor component is blocked opposite the pressure plate by the adjustment device.

A particularly simple and functionally reliable construction of an adjustment device for compensating the wear on the linings inside the friction clutch can be ensured in that the compensation unit has a bearing support component for the energy accumulator, such as in particular a plate spring and between this bearing support component and the pressure plate there is a compensating device which during disengagement of the friction clutch causes an automatic wear adjustment of the bearing support component and is self-locking during engagement of the clutch. This means that when the bearing support component is relaxed the compensating device is released and during loading of the bearing support component the compensating device retains its setting, thus is or becomes blocked.To this end it can be advantageous if the bearing support component is axially displaceable away from the pressure plate but can be locked axially towards the pressure plate. The compensation unit can thereby act like a freewheel during disengagement of the friction clutch but can be self-locking during engagement of the clutch.

A particularly simple construction of the compensation unit can be ensured by using a ring-like component to form a compensation component. The ring-like component can thereby be supported by ramps relative to the pressure plate. These ramps can interact with counter ramps wherein these can advantageously be tensioned relative to each other by at least one spring element. The ramps and counter ramps can thereby be formed by individual components such as eg wedgelike components which can be mounted between the pressure plate and the ring-like component. At least one of these ramp groups can however be mounted directly on the ring-like component or pressure plate.A simple construction of the friction clutch can thereby achieved in that the ring-like component is designed as a shaped hollow sheet metal part with a U-cross-section wherein wedge-like components spread out round the circumference and forming the ramps are housed in the free space of the component. These wedge-like components can thereby advantageously be rotationally secured with the ring-like component. An advantageous design of the compensation unit can be achieved in that the wedge-like components are guided axially displaceable relative to the ring-like component. The counter ramps can likewise be formed by wedge-like components which engage axially at least partially in the free space enclosed by the ring-like compensation component and can be rotatable relative to the pressure plate and compensation component.

It can thereby be advantageous if the compensation component is held rotationally secured relative to the pressure plate.

In order to ensure an automatic adjustment of the compensation unit the counter ramps can be spring-tensioned in the direction of the ramps. This spring tensioning can be carried out by means of springs, such as coil springs tensioned between the components forming the ramps and counter ramps wherein these springs are likewise housed in the ring-like free space of the compensation component and can advantageously be designed as compression springs. The components forming the counter ramps can be housed at least partially axially between the components forming the ramps and the ring-like compensation component. In order to ensure a satisfactory hold and guide for the springs tensioning the ramps and counter ramps it can be advantageous if at least the end areas of these springs are guided by the components forming the ramps and counter ramps.To this end the corresponding components can have attachments or projections which extend at least into the end areas of the pretensioned springs. These springs can thereby each be provided between a wedge-like component coupled rotationally secured but axially displaceable to the ring-like bearing support component and a circumferentially adjoining wedge-like component which can be rotated relative to the bearing support component.

The components forming the ramps and/or counter ramps can be simply made from plastics, eg through an injection moulding process. Suitable plastics are thermally insulating or temperature-resistant plastics such as eg thermoplastics or duroplastics. It can thereby be advantageous if the material forming the ramp components and/or counter ramp components has a higher friction value which lies in the order of the friction value of a friction lining material.

Through a corresponding choice of run-up angle of the ramps and/or counter ramps as well as the friction coefficient between the ramps and counter ramps it is possible to design the compensation unit so that self-locking occurs in the event of axial tension. To this end the ramps and/or counter ramps can be designed so that they have in the axial direction a pitch angle which lies between 5" and 20 , preferably in the order 8" to 12". It can thus be ensured through a suitable design of the compensation unit that the latter is self-locking during the engagement phase of the friction clutch so that no additional means are required in order to avoid undesired resetting of the compensation unit.

The energy accumulators tensioning the ramps and counter ramps can be pretensioned so that an adjustment always takes place with the onset of or presence of wear on the linings, thus the wear adjustment can also be carried out with a rotating clutch. The spring biasing of the ramps and counter ramps can thereby be carried out advantageously so that the function of the remaining springs, such as in particular the operating plate spring and the leaf springs connecting the pressure plate with the housing or cover are not or practically not affected.

In many cases it can however also be advantageous if the adjustment device is dependent on speed. Thus for example the centrifugal force acting on the individual elements of the adjustment device can be used for operating and/or locking the adjustment device at certain operating states of the internal combustion engine. More particularly the adjustment device can be blocked by means dependent on centrifugal force at a certain speed or on exceeding a certain speed range. In many cases it can be also be advantageous if the adjustment device is designed so that it only becomes operative at at least approximately idling speed or at speeds below the idling speed so that the wear adjustment can only take place at low speeds of the internal combustion engine.The means causing a locking or unlocking of the wear adjustment can advantageously be part of the compensation device and can be formed eg by the component parts forming the ramps and/or counter ramps.

For the adjustment function of the compensation device it can be particularly advantageous if during disengagement of the clutch the plate spring path in the diameter range of the pressure plate biasing through the plate spring is greater than the lift of the pressure plate fixed by the restricting means or wear sensors. It can thereby be ensured that after the restricting means contact an axially fixed component the compensation unit is relaxed and thus released for adjustment.

According to a further inventive feature the compensation unit can have two adjoining ramp assemblies wherein one of the ramp assemblies is rotationally secured relative to the pressure plate and the other ramp assembly is rotationally secured relative to a compensation component biased by the energy accumulator wherein the compensation component is rotatable relative to the pressure plate.

The invention further relates to a friction clutch, more particularly for motor vehicles with a pressure plate which is connected rotationally secured but axially displaceable to a restricted amount with a housing wherein a contact pressure plate spring is axially tensioned between the housing and pressure plate and this plate spring on the one side can swivel about a ring-like swivel bearing supported by the housing and on the other side biases the pressure plate in the direction of a clutch disc which can be clamped between this and a counter pressure plate, such as a flywheel wherein an adjustment device is provided which compensates the wear on the friction linings of the clutch disc and which causes a practically constant force biasing of the pressure plate through the contact pressure plate spring wherein between the contact pressure plate spring and the pressure plate there is a wear compensation unit which has at least one axially displaceable compensation component which is biased by the contact pressure plate spring, furthermore the axial disengagement path of the pressure plate is limited by restricting means acting between the pressure plate and at least one axially fixed component such as eg the housing and/or the counter pressure plate, and is held at least approximately constant and furthermore the restricting means restrict the axial displacement of the compensation component relative to the pressure plate at least during disengagement of the friction clutch.

For the functioning of the friction clutch, more particularly to minimize the disengagement force curve or the maximum disengagement force necessary it can be particularly advantageous if the clutch disc which can be clamped between the pressure plate and counter pressure plate has friction linings between which is mounted a socalled lining suspension such as is known for example from De-OS 36 31 863. The operation, more particularly the disengagement process of the friction clutch is assisted by using a clutch disc of this kind. This is due to the fact that in the engaged state of the friction clutch the tensioned lining suspension exerts on the pressure plate a reaction force which is directed against the force exerted on this pressure plate by the contact pressure plate spring or operating plate spring.During the disengagement process, during the axial displacement of the pressure plate this is first forced back through the resiliently tensioned lining suspension whereby at the same time as a result of the comparatively sharply falling characteristic line section in the disengagement area of the contact pressure plate spring, the force exerted by this plate spring on the pressure plate decreases. With the decrease in the force exerted by the contact pressure plate spring on the pressure plate the resetting force exerted by the lining suspension and pressure plate can also decrease.The force effectively required to disengage the friction clutch is produced from the difference between the resetting force of the lining suspension and the contact pressure force of the contact pressure plate spring wherein the axial force of the leaf springs tensioned where applicable between the pressure plate and housing is still to be taken into account. After relaxing the lining suspension, thus during the lift of the pressure plate from the friction linings or release of the clutch disc through the pressure plate, the disengagement force required is mainly determined by the contact pressure plate spring.The force-path characteristic of the lining suspension and the force-path characteristic of the contact pressure plate spring as well as the force-path characteristic of the leaf springs can be matched with each other so that during release of the clutch disc through the pressure plate the force required to operate the contact pressure plate spring is set at a low level. Thus by bringing the lining spring characteristic close to or equal to the force path resulting from or formed by the contact pressure plate spring and any leaf springs which may be present up to the release of the clutch disc through the pressure plate it is possible that only a very slight operating force, and in extreme cases none at all, is required for the contact pressure plate spring.

When matching the individual spring forces it is thus necessary to take into account the axial force applied by the leaf springs which act between the pressure plate and housing. Furthermore when designing the clutch it should be observed that the displacement or adjustment force of the wear scanner or wear sensors has to be applied by the at least one contact pressure energy accumulator such as in particular a plate spring, and thus this energy accumulator should be designed correspondingly stronger. Furthermore it is advantageous if the displacement force of the wear sensors is measured so that it is reliably greater than the resulting axial force which is produced by the tensioning of the wedges forming the ramps and counter ramps and which can be taken up by the wear sensors.

The invention will be explained in detail with reference to Figures 1 to 7 in which: Figure 1 is a view of a friction clutch according to the invention; Figure 2 is a section according to the line II-II of Figure 1; Figure 3 is a section along the line III-III of Figure 1; Figure 4 is a partial sectional view according to the line IV-IV of Figure 1; Figure 5 is a view of an adjustment ring used in the friction clutch according to Figures 1 and 2; Figures 6 and 7 show two further embodiments of friction clutches in accordance with the invention.

The friction clutch shown in Figures 1 and 2 has a housing 2 and a pressure disc 3 which is connected to same rotationally secured but displaceable axially to a restricted amount. A contact pressure plate spring 4 tensioned axially between the pressure disc 3 and the cover 2 can swivel about a ring-like swivel bearing 5 supported by the housing 2 and biases the pressure disc 3 in the direction of a counter pressure plate 6, such as for example a flywheel, fixedly connected to the housing 2 whereby the friction linings 7 of the clutch disc are clamped between the friction faces of the pressure disc 3 and the counter pressure plate 6.

The pressure disc 3 is connected rotationally secured to the housing by circumferentially or tangentially aligned articulated connecting means in the form of leaf springs 9.

In the illustrated embodiment the clutch disc 8 has socalled lining spring segments 10 which ensure a progressive torque build-up during engagement of the friction clutch by allowing a progressive rise in the axial forces acting on the friction linings 7 through a restricted axial displacement of the two friction linings 7 towards each other. However a clutch disc could also be used wherein the friction linings 7 are fitted practically rigid axially on at least one support disc.

In the illustrated embodiment the plate spring 4 has a ringlike foundation body 4a applying the contact pressure force and from which emerge radially inwardly aligned operating tongues 4b. The plate spring 4 is thereby installed so that it biases the pressure disc 3 with the radially further outer areas and can tilt with the radially further inner areas about the swivel bearing 5. The swivel bearing 5 comprises two swivel support pads 11, 12 which here are formed by wire rings and between which the plate spring is held axially and tensioned. In order to secure the operating plate spring 4 rotationally and to centre and hold the wire rings 11,12 relative to the housing 2, retaining means in the form of rivet elements 15 are fixed on the cover and each extend with an axially extending shaft 15a through a cut-out section provided between adjoining plate spring tongues 4b.

The clutch 1 has an adjustment device which compensates the axial wear on the friction faces of the pressure disc 3 and the counter pressure plate 6 as well as the friction linings 7, and which consists of a wear compensation unit 16 provided between the contact pressure plate spring 4 and pressure disc 3, and of restricting means 17 designed as path sensors and limiting the disengagement path of the pressure disc 3.

The restricting means 17 operating as wear sensors each have a socket 19 set rotationally secured in a bore 20 of the pressure disc 3. The socket 18 forms a slit 21 through which extend axially two leaf spring elements 22. The leaf spring elements 22 are supported against each other wherein at least one leaf spring element is curved, and preferably both leaf spring elements are curved in opposite directions.

The leaf spring elements 22 are housed in the socket with a definite pretension and are thus displaceable in the axial direction of the clutch 1 relative to the socket 18 against a predetermined friction resistance. The axial length of the leaf spring elements 22 is thereby selected so that when the friction clutch 1 is engaged these leaf spring elements have a definite play 24 relative to an axially fixed clutch component - in the illustrated embodiment relative to the outer edge area 23 of the housing - and this play corresponds to the predetermined disengagement path of the pressure disc 3.When the friction clutch is engaged the leaf spring elements 22 come to rest against the counter pressure plate 6 with their ends 22a remote from the housing 2 whereby it is guaranteed that with wear on the friction linings 7 the pressure disc 3 is displaced axially relative to the leaf spring elements 22 corresponding to this wear on the linings, namely against the action of the friction engagement between the leaf spring elements 22 and the socket 18 which preferably consists of plastics or a friction material.

In the illustrated embodiment the bore 20 in which the socket 18 is pressed in and fixed both axially and circumferentially, is provided in a pressure plate cam 25 which extends radially outwards and on which a leaf spring element 9 is attached by a rivet connection 9a. The socket 18 can be prevented from moving in the direction of the counter pressure plate 6 if the socket 18 has at its end facing the housing 2 a collar 18a through which it can be supported on the pressure disc 3. The socket 18 is prevented from moving out of the bore 20 in the direction of the housing or clutch cover 2 by leaf springs 9 which as shown in chain-dotted lines in Figure 1 engage partially radially round the socket 18 and where applicable additionally are axially fixed in the bore 20.The socket 20 can furthermore be prevented from turning in that it has a profiled section more particularly a recess which holds the areas 19 of the leaf springs 9 engaging over the socket.

The wear compensation unit 16 has a compensation component which is biased by the plate spring 4 and has the shape of a U-section sheet metal ring 26 which is shown in plan view in Figure 5. The compensation component 26 has on the side of the base 27 facing the plate spring 4 at least one ringshaped axial projection 28 or several projections 28 which are preferably evenly spread out over the circumference and are formed by grooves indented in the sheet metal material.

Segment-like projections 28 ensure that in the area between circumferentially adjoining projections 28 radial ports are formed between the plate spring foundation body 4a and the compensation ring 26 to allow air to pass for cooling. As can be seen in particular from Figure 2 the compensation ring 26 is centred relative to the pressure disc 3. To this end the pressure disc 3 has at least one step 29 which positions the radially inner axially extending wall 30 of the compensation ring 26 centrally relative to the pressure disc 3. The step 29 can be formed by a closed surface extending over the circumference or even by segment-like surfaces provided spaced out from each other over the circumference. The compensation ring 26 furthermore has a radially outer axially extending wall 31 which forms together with the inner wall 30 and the base 27 a ring-like free space 26a.Radially outside, the compensation ring 26 has radial extension arms or cams 32 which form stops which interact with counter stops 33 of the axially displaceable components in the form of leaf spring elements 22 of the wear sensor 17. The counter stops 33 are formed by noses moulded onto the leaf spring elements 22 and pointing radially inwards to engage over the extension arms 32. The axial displacement of the compensation ring 26 in the direction away from the pressure disc 3, thus in the direction of the housing is restricted by the counter stops 33.

Between the compensation ring 26 and the pressure disc 3 there is a compensating unit 35 which during disengagement of the friction clutch 1 and in the presence of wear on the linings allows an automatic adjustment of the compensation ring 26 and during engagement of the clutch causes an automatic locking, thus blocking action whereby it is guaranteed that during the engagement phase of the friction clutch 1 the compensation ring 26 retains a definite axial position relative to the pressure disc 3. This definite position can only change during a disengagement process and corresponding to the wear which occurs on the linings.

The adjustment device 34 comprises several pairs of wedges 35,36 preferably spread evenly over the circumference and housed in the annular free space 26a of the sheet metal ring 26. The wedges 36 supported on a ring-like face 37 of the pressure disc 3 are connected rotationally secured but axially displaceable to the sheet metal ring 26. To this end the sheet metal ring 26 has in the area of its axially extending walls 30,31 moulded areas in the form of grooves 38,39 which in the area of the free space 26a form projections which engage in corresponding indentations or grooves 40,41 of the wedges 36. The grooves 40,41 or moulded areas 38,39 run in the axial direction of the clutch 1. The wedges 35 are housed substantially axially between the base 27 of the sheet metal ring 26 and the wedges 36.

The wedges 35 and 36 form circumferentially extending and axially rising run-up ramps 42,43 by which the wedges 35,36 associated with one pair are supported against each other.

The wedges 35 are supported on the other side on the base 27 of the ring 26 and are displaceable circumferentially relative to this ring 26. The run-up ramps 42,43 are tensioned against each other. To this end energy accumulators in the form of coil springs 44 are housed in the ring chamber 26a and are supported by one end on a wedge 36 rotationally secured to the ring 26 and by the other end on a wedge 35 which is circumferentially displaceable. In order to hold the energy accumulators 44 the wedges 35,36 have at their ends facing the corresponding energy accumulators projections 45,46 which engage in the spring windings and thus secure the spring ends. The springs 44 are furthermore guided through the wall areas 30,31 and the base 27 of the ring 26.

In the illustrated embodiment the compensating ring 26 is secured against rotation relative to the pressure disc 3.

To this end, as is apparent from Figure 4, the pressure disc 3 has axial projections in the form of pins 47 which extend axially through recesses 48 which are provided in the area of the extension arm 32. Through this securement against rotation it is ensured that during the operation of the friction clutch the stop areas of the tabs 32 always remain positioned beneath the restricting noses 33 of the leaf spring elements 22.

In the illustrated embodiment, the wedges 35, 36 are made from a heat-resistant plastics, such as for example duroplastics or thermoplastics which can be additionally reinforced with fibres. The wedges 35, 36 acting as adjustment elements can be simply made as injection moulded parts. However it is also possible for at least one of the wedges 35,36 of one pair to be made from friction material such as for example lining material. The wedges or adjustment elements 35,36 can however also be made as moulded sheet metal parts or as sintered parts. The slope angle and extension of the run-up ramps 42,43 are designed so that an adjustment of the wear occurring on the friction faces of the pressure disc 3 and the counter pressure plate 6 as well as on the friction linings 7 is guaranteed throughout the entire service life of the friction clutch 1.

The wedge angle 49 or slope angle 49 of the run-up ramps 42,43 compared to a plane at right angles to the axis of rotation of the friction clutch is selected so that the friction which occurs when the run-up ramps 42,43 press against each other prevents slipping between these ramps.

The angle 49 can be in the range from 5 to 20 degrees, preferably in the order of 10 degrees depending on the material matching in the area of the run-up ramps 42,43.

The circumferentially displaceable wedges 35 are arranged so that they point with their wedge tips in the direction of rotation 50.

The tensioning by the energy accumulators 44 of the run-up ramps 42,43 as well as the slope angle 49 are designed so that the resulting axial force acting on the adjustment ring 26 is less than the required displacement force of the wear sensor 22 of the restricting means 17.

Furthermore when designing the plate spring 4 it must be taken into account that the contact pressure force to be applied by same for the pressure disc 3 must be increased by the required displacement force for the wear sensor 22 and by the tensioning force of the leaf springs 9 tensioned between the cover 2 and pressure disc 3. Furthermore the individual components must be designed so that the supporting wear between the plate spring 4 and bearing ring 26 as well as the contact wear between the wear sensors 22 and the counter pressure plate 6, and between the wear sensors and the housing 2 remain slight in comparison with the wear on the linings 7.

In order to prevent the curved or wavy leaf springs 22 from losing their tensioning force owing to the very high temperatures which occur on the pressure disc 3 during the clutch engagement process, the sockets 18 are preferably made from a material with a low heat conductivity and high friction value. The wedges 35,36 can be made from the same material.

In order to allow improved cooling of the clutch, particularly the pressure disc 3, radially aligned grooves can be provided spread out over the circumference in the pressure disc 3, one of these grooves being shown in dotted lines in Figure 2 and marked 51. These radial grooves 51 are, seen circumferentially, provided between each two adjoining pairs of wedges and extend between the ring 26 and pressure disc 3. However the ring 26 could have in the area of the springs 44 axial cut-out sections extending out from the base 27 whereby radial ports would be formed between the plate spring 4 and the ring 26.

In order to increase the wear resistance at the various bearing points the corresponding areas can be provided with a wear-resistant layer such as for example hard chromium plate, molybdenum coating, or special wear-resistant components can be provided in the area of the contact points. Thus for example plastics shoes can be provided on the wear sensors 22 in the area adjoining the counter pressure plate 6 and housing 2.

The leaf springs 9 transferring the torque to the pressure disc 3 are pretensioned between the pressure disc 3 and the housing 2 so that during disengagement of the friction clutch 1 they move the pressure disc 3 in the direction of the housing 2. It is thereby ensured that the ring 26 remains adjoining the plate spring 4 practically throughout the entire disengagement phase and until the restricting means 17 come into operation.

The disengagement path of the clutch in the area of the tongue tips 4c is preferably selected so that when the clutch is disengaged, the outer edge of the plate spring 4 is lifted by a slight amount from the ring 26. This means that during disengagement of the friction clutch 1 the plate spring path in the diameter range of the pressure disc biasing through the plate spring 4 is greater than the removal path 24 of the pressure disc 3 fixed by the path restricting means 22.

The relative position shown in Figure 2 of the individual components corresponds to the new state of the friction clutch. In the event of axial wear, more particularly of the friction linings 7, the position of the pressure disc 3 is moved in the direction of the counter pressure plate 6 whereby at first there is a change in the conicity and thus also in the contact pressure force applied by the plate spring in the engaged state of the friction clutch 1, namely preferably in the sense of an increase. This change causes the pressure disc 3 to alter its axial position relative to the wear sensors 22 axially supported on the counter pressure plate 6.Owing to the plate spring force acting on the ring 26, this ring 26 follows the axial displacement of the counter pressure plate 3 caused by wear on the linings whereby the stop areas 32 of the ring 26 lift axially from the areas serving as a counter stop in the form of noses 33 of the wear sensor 22, namely by an amount corresponding substantially to the wear on the linings. The compensating ring 26 retains its axial position during an engagement process relative to the pressure disc 3 because the ring is biased by the plate spring 4 in the direction of the pressure disc 3 and the wear compensating unit 34 is selflocking during the engagement process, thus acts as an axial lock.During disengagement of the friction clutch 1, the pressure disc is biased by the leaf springs 9 in the direction of the housing 2 and moves until the wear sensors 22 come to adjoin the housing 2 or housing stop areas 23.

Up to this disengagement path which corresponds to the lift path of the pressure disc 3, the axial position of the ring 26 relative to the pressure disc 3'is maintained. During a continuation of the disengagement process the pressure disc 3 remains axially still whilst the ring 26 axially follows the disengagement movement of the plate spring in the area of the biasing diameter, namely until the stop areas 32 of the ring 26 come to adjoin the counter stop areas 33 of the wear sensors 22. The axial displacement of the compensating ring 26 is caused by the wedges 35 which are biased by the springs 44. These wedges 35 are moved circumferentially relative to the wedges 36 until the ring 26 is tensioned against the counter stops 33 of the wear sensors 22.The lifting of the pressure disc 3 is ensured in the illustrated embodiment by the leaf springs 9 which are installed between the housing 2 and pressure disc 3 so that they have an axial pretensioning which forces the pressure disc 3 in the direction of the housing 2. If the plate spring 4 is swivelled in the disengagement direction then this is lifted by its radially outer area away from the adjustment ring 26 since the latter, as already described, is held back axially by the wear sensor 22 relative to the pressure disc 3. An at least slight lifting of the plate spring 4 from the adjustment ring 26 of this kind during a disengagement process is particularly advantageous for the functioning of the adjustment system 17 + 34.

The adjustment unit 17 + 34 according to the invention ensures that the adjustment on the supporting ring 26 is always carried out by the adjustment wedges 35,36 corresponding to the amount of wear on the linings. This is due to the fact that the adjustment ring 26 is axially tensioned between the adjustment means in the form of wedges 35, 36 and the wear sensors 22, which prevents the compensation component in the form of the ring 26 from being adjusted by an amount larger than the corresponding lining wear.Furthermore through the design of the adjustment device according to the invention it is guaranteed that even in the event of over movement in the area of the disengagement means, such as the plate spring tongues 4b, or in the case of axial vibrations of the pressure plate, no adjustment of the adjustment device 17 + 34 can take place since the wear sensors 22 are axially supported by the selflocking wear compensation device 34, namely by the counter stops 32, relative to the pressure disc 3 even in the case of a hard impact on the housing 2. Thus in the disengaged state of the friction clutch axial forces can act on the wear sensors 22 in the direction of the counter pressure plate 6 which are greater than the force-locking connection between the wear sensors 22 and the pressure disc 3 without the wear sensors being displaced axially relative to this pressure disc 3.

With the adjustment device according to the invention it is ensured that the plate spring works practically over the same characteristic line range throughout the entire service life of the clutch and in the engaged state of the friction clutch 1 has a practically constant tension position and thus also applies a practically constant contact pressure force to the pressure disc 3.It is thereby possible to use a plate spring with a degressive force characteristic line over the disengagement path, namely preferably in combination with a clutch disc whose linings 7 are supported resiliently against each other through spring segments 10 whereby the disengagement force effectively to be applied can be brought to a comparatively low level and can be kept practically constant throughout the service life of the clutch provided the lining spring characteristic line does not change significantly during the service life of the clutch.During disengagement of a clutch of this kind the plate spring 4 is swivelled about its cover bearing 5 whereby the spring segments 10 relax over a predetermined partial area of the axial disengagement path of the pressure disc 3 and thus the axial force applied by the spring segments 10 assists in the disengagement process of the friction clutch 1. This means that a smaller maximum contact pressure force need be applied than that which theoretically results in the engaged position of the clutch 1 from the installation position of the plate spring 4 and leaf springs 9.As soon as the spring or relaxation area of the segments 10 is exceeded then the friction linings 7 are released whereby as a result of the degressive characteristic line range in which the plate spring 4 operates, the disengagement force which is still to be applied is already reduced considerably relative to that which would correspond to the installation point or installation position according to Figure 2. On continuing with the disengagement process the disengagement force further decreases, namely until the minimum or trough point of the preferably sinusoidal characteristic line of the plate spring 4 is reached.

The adjustment device 17 + 34 shown in Figures 1 and 2 can advantageously be designed so that when the friction clutch 1 rotates the individual spring windings of the adjustment springs 44 are supported on the outer wall 31 of the adjustment ring 26 and the displacement forces applied by the springs 44 in the circumferential direction are reduced or evenly completely lifted as a result of the friction resistances produced between the spring windings and the adjustment ring 26. The springs 44 can thereby remain practically rigid during rotation of the friction clutch 1 as a result of the friction forces which suppress the spring action. Furthermore the adjustment wedges 35 can likewise be radially supported on the wall 31 of the adjustment ring 26 owing to the centrifugal forces acting on same and can be secured against rotation by the friction forces produced between the wedges 35 and the adjustment ring 26. It can thereby be achieved that at least with speed ranges above the idling speed of the internal combustion engine the wear compensation device 34 cannot be rotated by the springs 44.

The friction clutch 1 can thus be designed so that a compensation of the friction lining wear only takes place when operating the friction clutch 1 at idling speed or at least approximately at idling speed. The blocking of the adjustment ring 26 can however also be provided through a corresponding design of the wear compensation device 34 so that an adjustment of the lining wear can only take place when the internal combustion engine is stationary, thus when the friction clutch 1 is not turning or however even at very low speeds.

The material matching between the components 35,36 forming the adjustment ramps and the material of the components interacting with these components is preferably selected so that during the operating period of the friction clutch no adhesion can occur between the ramps and the components interacting therewith which would prevent adjustment. In order to avoid such adhesion at least one of these components can be provided with a coating at least in the area of the ramps or support faces.

In order to prevent adhesive connection between the run-up ramps and counter run-up ramps it is possible to provide at least one device which during disengagement of the friction clutch and during wear adjustment exerts an axial force on the or each adjustment element which causes the ramps to separate or tear loose.

In the new state of the friction clutch 1, thus in the state which the clutch has before it is fixed on the counter pressure plate 6 with the interposition of the clutch disc 6, the wedges 35 are located in a position drawn back further relative to the wedges 36 compared to the position shown in Figure 3 so that the adjustment ring 26 occupies its most drawn-back position in the direction of the pressure disc 3 and thus the pressure disc 3/ adjustment ring 26 unit requires the smallest possible axial structural space. In order to keep the wedges 35 in their restricted position prior to fitting the friction clutch 1, the wedges 35 have engagement areas in the form of recesses 52 for turning and retaining means.Such retaining means can be provided during manufacture or assembly of the friction clutch 1 and can be removed after fitting the friction clutch 1 on the flywheel 6 whereby the adjustment device 34 becomes activated. In the illustrated embodiment, circumferentially aligned oblong slits 53 are provided in the adjustment ring 26 through which the engagement areas of the retaining means or turning tool can be guided for engaging in the indentations 52. The circumferentially placed oblong recesses 53 must thereby have at least one extension which allows a rotation corresponding to the largest possible wear adjustment angle of the wedges 35 in the circumferential direction.The wedges 35 which are held in their retracted position in the circumferential direction when the friction clutch is in the new state can be held in this position by the wear sensors 22 which secure the adjustment ring 26 in its retracted position. The selfadjusting connections between the wear sensors 22 and the pressure disc 3 must be designed so that the displacement force required to move the wear sensors 22 relative to the pressure disc 3 is greater than the resulting force acting on the ring 26 and which is produced by the springs 44 biasing the wedges 35.

In the embodiment according to Figures 1 and 2 the ramps 43 can also be formed directly by the ring 26, for example by imprinting inclined faces 43 wherein the ring 26 must then be rotatable relative to the pressure disc 3 by the springs 44. With such a design the wedges 36 are rotationally secured with the pressure disc 3 or are moulded directly on same. Furthermore with this type of embodiment the stops which are formed as extension arms 32 must be extended in the circumferential direction corresponding to the required adjustment turning angle of the ring 26 in order to ensure that an axial restriction remains between the wear sensors 22 and the ring 26 throughout the service life of the friction clutch.With the last mentioned embodiment the adjustment ring 26 can be turned easily from radially outside even when the friction clutch 1 is fitted, namely in particular through the circumferentially extending stop tabs 32 which are accessible through radial ports provided on the outer sleeve of the clutch housing 2. These radial ports can in particular also house the torque transfer cams 25 of the pressure disc 3 as well as the leaf springs 9. The adjustment device according to the invention furthermore has the advantage that its principle can also be used with socalled pull-type friction clutches wherein the plate spring is supported for swivel movement on a cover by a radially outer edge area and biases the pressure disc with radially further inner edge areas. Such a clutch is shown in Figure 6.Between the plate spring 104 and the pressure disc 103 there is a wear compensation device 134 which can be designed like the one described in connection with Figures 1 and 2. The adjustment ring 126 again interacts by sensor elements 117 with wear sensors 122. The adjustment of the wear sensors 122 relative to the pressure disc 103 takes place by the stop areas 122a bearing on the housing or cover 102. The wear sensors 122 again support stops 133 which restrict the axial path of the pressure disc 103 during a disengagement process. In order to allow a satisfactory functioning of the adjustment device according to Figure 6, the ring 126 again has at least a possibility of a slight axial movement relative to the wear sensors 122.This can be achieved in that a corresponding stop connection 133a is provided with play between the wear sensors 122 and the ring 126 or however in that the ring 126 has radial areas 126a which are resiliently deformable in the axial direction, thus have an elastic pliability.

In accordance with a variant which is not illustrated, the wear sensor 122 can cooperate, instead of with the cover 102, with the plate spring 104 at least in one axial direction at least when the clutch is disengaged.

It can be advantageous if the abutment between the wear sensor 122 and the plate spring 104 reaches approximately to the radial level of the plate spring abutment/support diameter on the housing 102. For pull-type clutches it can be advantageous if the support diameter of the wear sensor on the plate spring is larger than the support diameter of the plate spring on the pressure plate.

With the embodiment illustrated in Figure 7 the wear sensor elements 217 are housed directly in the foundation body of the pressure disc 203. The wear sensors 222 have stop areas 222a which interact with cover areas 223 which form counter stops. The cover areas 223 are in one piece with fastening means 202a by which the plate spring 204 is mounted for swivel movement on the cover 202. In the illustrated embodiment the fastening or retaining means 202a are formed by tabs made in one piece with the cover material and extending axially through the plate springs 204. The wear compensation device 234 is provided radially outside of the wear sensors 217 provided in the radial area of the plate spring foundation body 204a.

In the embodiment according to Figure 7 the wear sensor 222 can, instead of cooperating axially with the housing 202 and/or with the cover regions 223, be supported on the plate spring 204 at least in one axial direction, preferably at least on clutch engagement. To this end, the plate spring 204 can have an axial recess through which the wear sensor 222 extends so that the abutment region 222a in the engaged condition of the clutch is supported axially against the plate spring 204 instead of against the counter abutment region 223. On disengagement of the friction clutch the abutment regions 222a can lift away from the plate spring 204 because the abutment regions 222a are provided at a smaller diameter than the support diameter of the plate spring 204 on the pressure plate 203. This is due to the fact that the abutment region 222a is located nearer to the pivot diameter of the plate spring 204 than the support diameter between pressure plate 203 and plate spring 204.

The invention is not restricted to the embodiments described and illustrated but also embraces variations which can be formed by a combination of individual features and elements described in connection with the various embodiments.

Furthermore individual features or methods of functioning described in connection with the drawings and taken alone can represent an independent invention.

Claims

PATENT CLAIMS

1. Friction clutch, more particularly for motor vehicles, with a pressure plate which is connected rotationally secured but axially displaceable to a limited extent to a housing wherein between the housing and pressure plate there is at least one operating means and an energy accumulator by which the pressure plate can be biased in the direction of a clutch disc which can be clamped between this pressure plate and a counter pressure plate, such as a flywheel wherein an adjustment device is provided which compensates at least the wear on the friction linings of the clutch disc and which comprises a wear compensating unit which is provided between the operating means or energy accumulator and pressure plate and which carries out an axial adjustment between the operating means or energy accumulator and pressure plate corresponding to the state of wear of the friction linings, wherein on reaching the adjustment corresponding to the actual state of wear of the friction linings the wear compensation unit is restricted in its adjustment function by means provided on the pressure plate.

2. Friction clutch according to claim 1 characterised in that between the housing and pressure plate there is an axially tensioned plate spring which can swivel about a ring-like support supported by the housing and which has a ring-like foundation body to form the energy accumulator from which emerge radially inwardly extending tongues.

3. Friction clutch according to claim 1 or 2 characterised in that the restricting means for the compensation unit are formed by at least one wear sensor which has a sensor component which can be displaced relative to the pressure plate and which by abutting an axially fixed component limits the disengagement path of the pressure plate.

4. Friction clutch according to claim 3 characterised in that the sensor component is axially displaceable and is connected to an axially displaceable component eg the pressure plate, by an automatic adjustment device and can be adjusted by abutting at least one axially fixed component such as the housing and/or the counter pressure plate.

5. Friction clutch according to claim 3 or 4 characterised in that the displaceable sensor component has a contact bearing area which interacts with a counter contact bearing area of a compensation component of the compensation unit during disengagement of the friction clutch.

6. Friction clutch according to one of claims 3 to 5 characterised in that the displaceable sensor component is supported on the pressure plate by an adjustment device.

7. Friction clutch according to one of claims 1 to 6 characterised in that the compensation unit comprises a bearing support component for the energy accumulator and between this bearing support component and the pressure plate there is a compensating device which during disengagement of the friction clutch causes an automatic wear adjustment of the bearing support component and is self-locking during engagement of the clutch.

8. Friction clutch according to claim 7 characterised in that the bearing support component is displaceable axially away from the pressure plate but can be locked axially towards the pressure plate.

9. Friction clutch according to one of claims 1 to 8 characterised in that the compensation unit acts like a freewheel during disengagement of the friction clutch but is self-locking during engagement of the friction clutch.

10. Friction clutch according to one of claims 1 to 7 characterised in that the compensation unit has a compensation component formed by a ring-like component.

11. Friction clutch according to claim 10 characterised in that the ring-like component is supported opposite the pressure plate by ramps.

12. Friction clutch according to claim 11 characterised in that the ramps interact with counter ramps.

13. Friction clutch according to claim 12 characterised in that the ramps and counter ramps are tensioned relative to each other by springs.

14. Friction clutch according to one of claims 10 to 13 characterised in that the ring-like component is designed as a hollow shaped sheet metal part with a U-shaped crosssection wherein in the free space of the component there are wedge-like components spread out round the circumference and forming the ramps.

15. Friction clutch according to claim 14 characterised in that the wedge-like components are secured against rotation relative to the ring-like component.

16. Friction clutch according to claim 14 or 15 characterised in that the wedge-like components are axially displaceable relative to the ring-like component.

17. Friction clutch according to claim 12 to 16 characterised in that the counter ramps are formed by wedgelike components which engage at least partially in the free space enclosed by the ring-like compensation component and are rotatable relative to the pressure plate and compensation component.

18. Friction clutch according to claim 5 to 17 characterised in that the compensation component is secured against rotation relative to the pressure plate.

19. Friction clutch according to one of claims 11 to 18 characterised in that the counter ramps are spring-biased in the direction of the ramps.

20. Friction clutch according to claim 19 characterised in that the spring biasing is carried out by means of springs, such as eg coil springs, tensioned between the components which form the ramps and counter ramps.

21. Friction clutch according to one of claims 11 to 20 characterised in that the components forming the counter ramps are housed at least partially axially between the components forming the ramps and the compensation component.

22. Friction clutch according to one of claims 11 to 21 characterised in that at least the end areas of the springs tensioning the ramps and counter ramps are guided by the components forming the ramps and counter ramps.

23. Friction clutch according to one of claims 11 to 22 characterised in that the components forming the ramps and/or counter ramps are formed from a thermally insulating and temperature-resistant material.

24. Friction clutch according to one of claims 11 to 23 characterised in that the components forming the ramps and/or counter ramps are made from a temperature-resistant material such as for example thermoplastics, duroplastics.

25. Friction clutch according to one of claims 11 to 24 characterised in that the material forming the ramp components and/or counter ramp components has a higher friction value.

26. Friction clutch particularly according to one of claims 1 to 24 characterised in that during disengagement of the clutch the plate spring path in the diameter range of the pressure plate biasing through the plate spring is greater than the lift of the pressure plate fixed by the restricting means.

27. Friction clutch according to claim 26 characterised in that with each disengagement process the compensation unit is relaxed.

28. Friction clutch according to at least one of claims 1 to 27 characterised in that the compensation unit has two adjoining ramp assemblies wherein one of the ramp assemblies is rotationally secured relative to the pressure plate and the other ramp assembly is rotationally secured relative to a compensation component which can be biased by the energy accumulator wherein the compensation component is rotatable relative to the pressure plate.

29. Friction clutch, more particularly for motor vehicles with a pressure plate which is connected rotationally secured but axially displaceable to a restricted amount to the housing, wherein between the housing and pressure plate there is an axially clamped contact pressure plate spring which on one side can swivel about a ring-like swivel bearing supported by the housing and on the other side biases the pressure plate in the direction of a clutch disc which can be clamped between this pressure plate and a counter pressure plate, such as a flywheel, wherein an adjustment device is provided which compensates the wear on the friction linings of the clutch disc, characterised in that between the contact pressure plate spring and pressure plate there is a wear compensation unit which has at least one axially displaceable compensation component which is biased by the contact pressure plate spring, furthermore the axial disengagement path of the pressure plate is limited by restricting means acting between the pressure plate and at least one axially fixed component, and is held at least approximately constant, and the restricting means, at least during disengagement of the friction clutch, restrict the axial displacement of the compensation component opposite the pressure plate.

30. A friction clutch, substantially as herein described with reference to any one embodiment shown in the accompanying drawings.