FR2781024A1 - Wear adjustment device for friction clutch uses an elastic clip on the regulating ring which acts permanently on the support zones of the clutch rear cover - Google Patents

Abstract

The friction clutch (10) of a type comprises a rear cover (14) and front pressure plate (30) causing cover rotation, with axial movement (X-X) between the clutch engaged and disengaged positions. The cover (14) is subject to the action of an elastic engaging-element (12). The element engages the support zone (28) formed on the regulating ring (36) attached to the ramp unit (44) which is positioned axially between the clutch mechanism and the pressure plate (30).

Description

The present invention relates to a friction clutch.

  The invention relates more particularly to a friction clutch, in particular for a motor vehicle, which is equipped with a device for compensating for wear due in particular to the wear of the friction linings, the wear take-up device intervening automatically at as the friction linings wear. A friction clutch of conventional design generally comprises a reaction plate, possibly in two parts, for the formation of a damping flywheel or of a flexible flywheel, which is locked in rotation on a first shaft, usually a driving shaft such as the crankshaft of the vehicle combustion engine, and supporting by its outer periphery a cover to which is attached, with mobility

  axial, 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 axially acting engagement means which are controlled.

by declutching means.

  The declutching means, according to known designs, can consist of helical springs, or two Belleville washers mounted in series, subjected to the action of declutching levers forming the

declutching means.

  According to the generally most widespread design, the engagement and disengagement means belong to the same part, for example to a metal diaphragm bearing on the cover, the diaphragm being able to be mounted in series or in parallel with a

  Belleville washer to provide assistance to the clutch release effort.

  At least one 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 so as to be clamped between these two plates when the clutch is in the engagement position to transmit the torque from the drive shaft to the driven shaft. Conventionally, the friction linings are mounted on an axially elastic support which is rigidly or resiliently coupled to a hub wedged in rotation on the driven shaft. Thanks to this arrangement, the friction disc assists the diaphragm during the clutch release operation. According to a most widespread design, the engagement means, the cover and the pressure plate belong to a unitary assembly called mechanism

friction clutch.

  The clutch means control the axial movement of the pressure plate when they are actuated by a declutching stop by means of the declutching means. The clutch release bearing can be controlled mechanically, hydraulically or electrically. The control can be of the manual, automatic or semi-automatic type. During the service life of such a clutch, the friction linings as well as the counter-materials, pressure and reaction plates wear out, which then causes a variation in the axial position of the pressure plate and that of the axial action clutch means and the clutch release bearing, these pressure variations resulting in a variation of the clamping force between the friction disc on the one hand and the pressure and reaction plates on the other hand, due to the modifications to the working conditions of the clutching means. The force required to disengage is affected. In order to remedy this drawback, it is known to provide such a clutch with a wear take-up device, the engagement means as well as the declutching stop, which is usually in constant abutment on the declutching means, while still occupying the same position when the clutch is in the engagement position and this regardless of the level of wear of the various components, and in particular the linings of

friction.

  Examples of such a friction clutch provided with wear compensation are for example described and represented in the applications for

  French patent Nos. 96 15865 and 98 01453 in the name of the plaintiff.

  These documents propose a friction clutch, in particular for a motor vehicle, of the type comprising a rear cover, a front pressure plate which is linked in rotation to the cover and which can move axially relative to the cover while being subjected to the action of elastic means recalling the pressure plate axially towards the cover, and elastic engagement means with axial action axially interposed and acting between on the one hand the cover and, on the other hand, the pressure plate via zones of support formed on an adjustment ring belonging to a wear take-up device for example with ramps which is interposed

  axially between the engagement means and the pressure plate.

  The adjustment ring belonging to the wear take-up device is mounted rotating about its axis relative to the friction plate, under the control of a ratchet-type mechanism for the purpose

  to compensate for the wear phenomena mentioned above.

  In this type of wear take-up device, in order to avoid that, under the effect of the axial vibrations transmitted by the crankshaft, the ramps of the ramp means of the wear take-up device do not move axially and that the two moving parts in rotation with respect to each other, that is to say the adjusting ring and the pressure plate, may turn inadvertently relative to each other, it is known to arrange elastically deformable means

  to keep the ramps in mutual contact.

  An example of such elastic means is described and shown in document FR-A-2,402,114 in which elastic blades are carried by the adjustment ring to press it axially against the pressure plate, these elastic blades being arranged radially inwards with respect to the radius along which the

support zones.

  The object of the invention is to take advantage of the adjustment ring.

  In order to avoid the phenomena of untimely separation of the ramps of the wear take-up device, the invention proposes a friction clutch of the type mentioned above, characterized in that at least one elastic clamp is provided carried by the ring adjustment device which permanently engages the clutch means in contact

against the support zones.

  Thanks to the invention, it takes advantage of a simple and economical way

  the presence of the adjusting ring.

  According to other characteristics of the invention - the engagement means consist of an elastic diaphragm having a peripheral portion, radially external, in the form of a Belleville washer, the external radial periphery of which cooperates with the bearing zones and the elastic clamp present, in axial section, a general shape of C and comprises two front and rear end branches, forming jaws, of generally transverse orientation and a central connecting branch, of generally axial orientation, which extends opposite the peripheral edge exterior of Belleville washer; - The adjusting ring comprises a radially inner part and of generally transverse orientation, the front transverse face of which cooperates with the pressure plate and the rear transverse face of which includes the bearing zones; - The free end of the rear end branch of the spring clip has a rounded profile, the convexity of which is oriented axially towards the front to cooperate with the portion opposite the rear transverse face of the Belleville washer. ; - The bearing zones are arranged substantially on the same circumference, and in that the point of contact between said rounded profile and the Belleville washer is arranged radially substantially in line with said circumference; - The front end branch of the elastic clamp cooperates with a portion opposite the front transverse face of the inner part of the adjustment ring; The adjusting ring comprises a radially outer part and of generally axial orientation which extends axially from rear to front from the periphery of the inner part of the adjusting ring and which comprises at least one hole for the passage of the front end branch of the spring clip; - The front end branch of the elastic clamp is bent at 90 and has a section of axial orientation which extends axially from front to back from the central branch and inside said hole and has a section free end of transverse orientation which cooperates with said portion opposite the front transverse face of the inner part of the adjustment ring; - The diaphragm is supported by the internal radial periphery of its Belleville washer against an annular boss formed in the internal face of the cover which is arranged radially inwards relative to the radius of action of the elastic clamp; - The Belleville washer is extended radially inwards by a central part fragmented into radial fingers by slots for the formation of declutching means; - the clutch comprises a series of elastic clips distributed

  angularly on a regular basis.

  Other characteristics and advantages of the invention will appear

  on reading the following detailed description for understanding

  which will be referred to the accompanying drawings in which: - Figure 1 is an axial sectional view which illustrates the main components of a clutch mechanism produced in accordance with the teachings of the invention and in which the friction clutch is illustrated in a engaged position; and - Figure 2 is a view similar to that of Figure 1 on

  which the clutch is illustrated in the disengaged position.

  The clutch mechanism 10 illustrated in the figures is of the type described and represented in French patent application No. 96 15865, the content of which may be referred to in detail for the general structure of the clutch and more particularly that of its

  known means for automatically adjusting wear with ramps.

  The part of the clutch mechanism according to the invention illustrated in FIGS. 1 and 2 corresponds in particular to the lower part of FIG. 21 of French patent application No. 96 15865 or to FIG.

21 of document FR-A-2 753 503.

  The friction clutch 10 is of the diaphragm type 1, of frustoconical shape in the free state, and it comprises a rear cover 14 which is a metallic piece of pressed sheet metal of general shape of revolution around the central axis XX of the clutch. The diaphragm 12 therefore has a peripheral part 24 in the form of a Belleville washer, extended inwards by a central part fragmented into fingers.

radial 20 by blind slots.

  The cover 14 includes a bottom 16 in the form of a generally transverse orientation wall, that is to say perpendicular to the axis X-X of the clutch mechanism, and means (not shown)

  fixing the cover 14 to a reaction plate (not shown).

  Here the fixing means consist of a radial flange provided with holes

for the passage of fixing screws.

  The clutch illustrated in the figures is of the pushed type, that is to say

  say that it is necessary, using a clutch release bearing (not shown), to act by pushing axially from back to front (that is to say from right to left considering the figures) on the internal radial ends 18 of the fingers 20 of the diaphragm 12 to disengage (disengage)

clutch 10.

  To do this, the bottom 16 of the cover 14 carries a primary support 22 which, in the embodiment illustrated in the figures, is an annular stamp produced in the bottom 16 of the cover 14 which projects axially towards the rear and, from on the other hand, opposite the primary support 22, a secondary support which is for example produced in the form of profiled heads of balusters (not shown in the figures) or

  any other means such as a rolled crown worn by balusters.

  To do this, the columns cross the widened bottoms of the slots separating the fingers two by two. All forms of secondary support described in document FR-A-2 456 877 are conceivable. The diaphragm 12, by the internal periphery of its Belleville washer 24, is thus pivotally mounted between the primary 22 and secondary supports. By the external periphery 26 of its Belleville washer 24, the diaphragm 12 is in contact with support zones 28

which will be described later.

  The invention is not limited to the case of a friction clutch of the pushed type, but it also finds application in the case of a clutch of the pulled type, as described for example in the document FR-A-2. 606 477 in which it is necessary to act in axial traction, that is to say from front to back, on the internal radial ends 18 of the fingers 20

  diaphragm 12 to disengage (disengage) the clutch.

  The friction clutch 10 also comprises a pressure plate which is a massive annular part of revolution, here in cast iron, and which is delimited axially towards the front by a transverse friction face 32 which is intended to cooperate with a disc of friction (not shown), carrying friction linings at its outer periphery,

  which cooperates itself with the reaction plate (not shown).

  According to a known arrangement, the reaction plate is intended to be locked in rotation on a driving shaft, such as the crankshaft of the internal combustion engine, while the friction disc is intended to be locked in rotation on a driven shaft (not shown) as

  the input shaft of the vehicle transmission gearbox.

  The pressure plate 30 is integral in rotation with the cover 14 by means of elastic tongues of generally tangential orientation (not shown) which at the same time constitute elastic means for returning the pressure plate 30 in the direction of the cover 14, c that is to say that the pressure plate is permanently stressed axially from front to back (from left to right considering the figures) towards the internal face 17 of the bottom 16 of the

cover 14.

  To maintain, when the clutch is engaged, the elastic axial engagement clutch means, constituted by the Belleville washer part 24 of the diaphragm 12, in a position independent of the wear of the friction disc linings, and to a lesser extent the wear of the pressure and reaction plates 30, the so-called friction surfaces of which also wear out in contact with the linings of the friction disc, a design wear take-up device is provided

  general known type of ramps or freewheel.

  The wear take-up device 34 here comprises ramp means, arranged circumferentially. More specifically, these ramp means comprise a ramp adjustment ring 36 which is a part

in cut and stamped sheet metal.

  In axial section and as illustrated in the figures, the adjustment ring 36 generally comprises a radially inner part 38, of generally transverse orientation, which extends inward and which is interposed axially between the pressure plate and the Belleville washer 24 of the diaphragm 12, and a radially outer part 40 of axial orientation allowing centering of the ring 36 relative to the plate 30. The internal periphery of the part 40 is allowed to come into intimate contact with the periphery external of

tray 30.

  From its internal peripheral radial edge 42, the radially inner part 38 of the ring 36 has ramps 44 arranged circumferentially and oriented axially forward towards the pressure plate 30, then the support zones 28 oriented axially towards the rear in the direction of the Belleville washer 24 and the cover 14, these bearing zones 28 being for example constituted by the rounded rear edge of stamped arcs of circle which are centered on the axis XX of the clutch and which are arranged radially on the outside

relative to the ramps 44.

  Thanks to the wear take-up device, the distance D between the friction face 32 of the pressure plate 30 and the bearing zones 28 of the ring 36 increases as the friction linings wear. To this end, in a known manner, the pressure plate 30 has, on its rear transverse face 31, facing the internal face 17 of the bottom 16 of the cover 14, studs 46, which are here produced integrally by molding with the annular body of the pressure plate 30, which are distributed circumferentially at a distance from one another which corresponds to that which circumferentially separates two ramps 44 from the ring 36, each of the studs 46 being intended to cooperate

individually with a ramp 44.

  The ramp means 36, 44, 46 are arranged axially between the pressure plate 30 and the Belleville washer 24 of the diaphragm 12 so that the studs 46 cooperate with the ramps 44 while the diaphragm 12, 24 cooperates with the zones of support 28 which thus constitute the support means through which the diaphragm 12

acts on the pressure plate 30.

  This arrangement is economical and simple, the ramp means being metallic and obtained by stamping, the studs 46 being molded and machined, advantageously being chamfered to cooperate.

with ramps 44.

  In order to carry out the adjustment as a function of wear, and according to a general design known from the French patent applications mentioned above, the ring 36 is rotated relative to the pressure plate 30 by means of a crown toothed device 48 which extends radially outwards the front axial end 50 of the radially outer part of axial orientation 40 of the ring 36. To do this, your toothed crown 48 is allowed to be driven by a screw as described in the

  aforementioned documents FR 96 15865 and FR-A-2 753 503.

  As the friction linings wear, the adjusting ring 36 will rotate relative to the pressure plate 30, increasing the axial distance separating the bearing zones 28 from the face

rear friction 32.

  This radially outer part 40 of the ring 36 extends axially from rear to front between the external peripheral zone 26 of the Belleville washer 24 of the diaphragm 12 and the pressure plate 30 and it comprises, in a known manner, a series of holes 52 for its lightening and to facilitate the circulation of air inside the mechanism

for cooling.

  In accordance with the teachings of the invention, and in order to avoid inadvertent axial separation of the ramp means 36, 44, 30, 46, the pressure plate 30 is permanently axially biased rearward towards the cover 14 by the elastic tongues (not shown) which link these two elements in rotation, and the support zones 28 of the adjustment ring 36 are kept permanently in contact with the portion facing the front transverse face 54 of the Belleville washer 24 by means of a series of elastic clamps 56 which are distributed angularly in a regular manner around the axis XX and one of which is illustrated in axial section at

Figures 1 and 2.

  Each elastic clamp 56 has, in axial section, substantially the shape of a lying C and it thus comprises a central connecting branch 58 which connects two end branches between them

front 60 and rear 62.

  The central connecting branch 58 is generally of axial orientation and it extends from rear to front, first facing the outer radial peripheral edge 64 of the Belleville washer 24, then facing the radially outer part 40 d axial orientation of

  the ring 36, and this in line with a ventilation hole 52.

  The end branch 62, which is generally of transverse orientation, extends radially inwards from the corresponding axial end of the central connecting branch 58 to form a first jaw of the elastic clamp 56 which cooperates with the portion opposite the rear transverse face 66 of the periphery

  external radial of the Belleville washer 24.

  To this end, the free end 68 of the rear end branch 62 is curved with its convexity oriented axially towards the front to define a point or a circumferential line of support for the branch 62 against the rear transverse face 66 of the Belleville washer 24 which is situated radially on substantially the same radius as that which defines the circumference along which the circumferentially extend the

support zones 28.

  The front end branch 60 is a branch bent at 90, substantially in the shape of a lying L, which has a section 72, generally of axial orientation, which extends axially from back to front, from the end corresponding axial of the central connecting branch 58, inside the hole 52 and slightly radially inward and which is extended by the other branch of the L which constitutes a free end section 74 of generally transverse orientation which is in contact with a facing portion 76 of the rear transverse face of the radially inner part 38 of the ring

  adjustment 36 to constitute the second jaw of the elastic clamp 56.

  The free end 74 extends radially above the ramps 44. Thus, the rear 62 and front end 62 branches constitute the two jaws of the elastic clamp 56 which permanently tighten the bearing zones 28 of the adjusting ring 36 in contact with the Belleville washer 24 of the diaphragm 12 so as to avoid any untimely axial separation of these two parts, while the studs 46 are stressed axially with the pressure plate 30 permanently

  contact with the wheels 44 towards the bottom 16 of the cover 14.

  Each elastic clamp 56 acts generally in axial clamping according to a radius corresponding to that of the support zones 28 and of the curved free ends 68 of the rear end branches 62, this radius being arranged radially outward relative to the support.

primary 22.

  The design of each elastic clamp 56 is such that it is put in place by elastic interlocking while being retained radially outwards by the elbow 78 for connection between the sections 72 and 74 which extends opposite the concave bend in screws -to-screw which connects the radially inner 38 and radially outer 40 parts of

the ring 36.

  Thus, on the one hand, the clamp 56 is designed to resist the phenomena of centrifugation by cooperation of the elbow 78 with the internal periphery of the axially oriented external part 40 of the ring 36, and, on the other hand, the mounting and fixing each elastic clamp 56 does not require any additional element such as by

  example of the rivets, nor any welding operation.

  Of course, as a variant, the attachment of each clamp may use rivets, welding operations, etc. Advantageously, the positioning and mounting of each elastic clamp 56 are carried out through a hole 52 in the ring 36 which

  already exists for ventilation and ventilation of the clutch.

  As can be seen by comparing FIGS. 1 and 2, the coupling between the ring 36 and the Belleville washer 24 of the diaphragm 12 produced by the elastic clamps 56 allows these elements to move axially generally relative to the cover 14, with the piston 30, without relative axial displacement between the three main components which are the pressure plate 30, the adjusting ring 36 and the Belleville washer 24 which form a generally globally movable assembly axially relative to the cover 14 considering the periphery

external radial of these components.

  Note that during the clutch release operation in Figure 2, the

  cover 14 prevents centrifugation of the clamp 56.

Claims (12)

  1. Friction clutch (10), in particular for a motor vehicle, of the type comprising a rear cover (14), a front pressure plate (30) which is linked in rotation to the cover (14) and which can move axially (XX ) relative to the cover (14) being subjected to the action of elastic means recalling the pressure plate (30) axially towards the cover (14), and elastic engagement means (12) with axial action axially interposed and acting between on the one hand the cover (14) and, on the other hand, the pressure plate (30) by means of support zones (28) formed on an adjustment ring (36) belonging to a take-up device of wear with ramps (44) which is axially interposed between the engagement means (12, 24) and the pressure plate (30), characterized in that at least one elastic clamp (56) carried by the adjustment ring (36) which permanently urges the clutch means (12, 24) in contact with the s support zones (28).   2. Clutch according to claim 1, characterized in that the engagement means consist of an elastic diaphragm (12) having a peripheral portion (24), radially external, in the form of a Belleville washer, the external radial periphery of which (26) cooperates with the bearing zones (28), and in that the elastic clamp (56) has, in axial section, a general shape of C and comprises two front (60) and rear (62) end branches, forming jaws, of generally transverse orientation, and a central connecting branch (58), of generally axial orientation, which extends opposite the edge   external device (64) of the Belleville washer (24).   3. Clutch according to any one of the claims   previous, characterized in that the adjustment ring (36) comprises a radially inner part (38) and of generally transverse orientation, the front transverse face (44) of which cooperates with the pressure plate (30, 46) and the rear transverse face includes the support zones (28).   4. Clutch according to the preceding claim taken in combination with claim 2, characterized in that the free end (68) of the rear end branch (62) of the elastic clamp (56) has a rounded profile whose convexity is oriented axially towards the front to cooperate with the portion facing the face   rear transverse (66) of the Belleville washer (24).   5. Clutch according to the preceding claim, characterized in that the bearing zones (28) are arranged substantially on the same circumference, and in that the point of contact between said rounded profile (68) and the Belleville washer (24, 66) is arranged radially substantially in line with said circumference. 6. Clutch according to claim 3 taken in combination with claim 2, characterized in that the front end branch (60) of the elastic clamp (56) cooperates with a portion opposite (76) of the front transverse face of the inner part (38) of The adjusting ring (36).   7. Clutch according to any one of claims 3 to 6,   characterized in that the adjusting ring (36) has a radially outer portion (40) of generally axial orientation which extends axially from rear to front from the periphery of the inner portion (38) of the ring adjustment (36) and which comprises at least one hole (52) for the passage of the front end branch (60) of the clamp elastic (56).   8. Clutch according to the preceding claim taken in combination with claim 6, characterized in that the front end branch (60) of the elastic clamp is bent at 90 and comprises a first section (72) of axial orientation which s extends axially from front to back from the central branch (58) and inside said hole (52), and comprises a second free end section (74) of transverse orientation which cooperates with said portion in vis-à-vis the front transverse face (76) of the inner part (38) of the adjusting ring (36).   9. Clutch according to claim 8, characterized in that the clamp (56) is retained radially outwards by the connection elbow (78) of the second section (74) to the first section (72) cooperating with the internal periphery of the radially outer part   and axial orientation (40 of the adjustment ring (36).   10. Clutch according to any one of claims 2 to 9,   characterized in that the diaphragm (12) is supported by the internal radial periphery of its Belleville washer (24) against an annular boss (22) formed in the internal face (17) of the cover (14, 16) which is arranged radially inward relative to the radius of action of the elastic clamp (56).   11. Clutch according to any one of claims 2 to   , characterized in that the Belleville washer (24) is extended radially inwards by a central part fragmented into fingers   radial (20) by slots for forming declutching means. 12. Clutch according to any one of the preceding claims, characterized in that it comprises a series of pliers   elastic bands (56) distributed angularly in a regular manner.