FR2699623A1 - Diaphragm friction clutch for motor vehicles - Google Patents

Abstract

The unit consists of a cover (20) and a pressure plate (18) between which is inserted a elastic diaphragm (28) which has on its exterior periphery (26) an annular form (26) and which its interior extends radially in the form of a series of fingers. The tips of these elastic fingers cooperate with the clutch control mechanism which extends parallel to the axis of the clutch.The diaphragm (28) has two opposite faces (24,30) of which the face (24) cooperates face to face with a portion (34) of the housing (20). Between these two faces of the diaphragm (28) and cover (20) is inserted an annular cord (32) in a cross- linkable material which is deposited on the surface at this point (34).

Description

 The present invention relates to a diaphragm friction clutch, in particular for a motor vehicle.

 The invention relates more particularly to a clutch of the type comprising a cover and at least one pressure plate between which is arranged an elastic diaphragm, of frustoconical shape in the free state, comprising an external peripheral part in the form of an annular Belleville washer, of which the inner edge extends radially inward by a series of elastic fingers, the free ends of which cooperate with a clutch control member, which moves parallel to the axis of the clutch and of the type in which the two opposite faces of the annular part of the diaphragm cooperate respectively with a surface portion formed opposite on the pressure plate and with a surface portion formed opposite on the internal face of the cover. These surface portions form annular supports for the diaphragm.

 Using such a type of clutch, the driver, by pressing the clutch pedal, usually actuates a fork, which presses the clutch release bearing (clutch control member) on the ends of the fingers of the diaphragm for maneuvering the same. Thus the diaphragm no longer exerts any force on the pressure plate, the latter conventionally peeled off by return tabs releases the clutch disc, which is no longer linked in rotation to the flywheel and the gearbox is then disconnected from the engine.

 According to a known design, the outer peripheral part of the diaphragm is a part made of a sheet of substantially constant thickness, which cooperates, on the one hand, with an annular boss formed on the face opposite the pressure plate and, on the other hand, with another annular boss formed vis-à-vis on the internal face of the cover constituting a primary support.

 This annular boss of the cover is for example a projecting annular rib produced integrally by stamping the cover. The contact of the diaphragm with this rib can be noisy, especially during the tilting of the diaphragm.

 This solution complicates the manufacture of the cover and in addition, the forces contributing to the elastic tightening, which applies the diaphragm axially with a determined clamping load against its primary support, partly depend on the dimensions of the annular boss of the cover, and therefore on its wear. possible.

 Controlling the tightening is very important, in particular as regards the lifting of the pressure plate and the declutching stroke, for good release of the friction linings from the friction disc.

 The object of the present invention is to remedy the drawbacks which have just been mentioned while modifying the design and manufacture of the clutch as little as possible.

 To this end, the invention provides a friction clutch of the type mentioned above in which one of the two opposite faces of the annular peripheral part of the diaphragm, called the first face, cooperates with a portion facing the cover, characterized in that an annular bead of crosslinkable elastic material, produced by deposition on a portion of deposition surface associated with the cover or the diaphragm and to which the bead adheres after its deposition, is interposed between the first face of the annular peripheral part diaphragm and the cover portion.

 Thanks to the invention the noises are reduced and the clutch is simplified. Wear is also caught up. In addition, the sticky bead can ensure a rotational connection of the diaphragm with the cover for the benefit of a reduction in wear phenomena and better dynamic balancing. In addition, this bead, the deposition of which is easy to produce, can be crushed so that the geometric irregularities of the cover are caught and the manufacturing tolerances less precise. I1 results from this that the free ends of the diaphragm fingers are in the same plane for the benefit of better lifting of the pressure plate, provision of the clutch release bearing and reduction of wear on the fingertips. diaphragm. The longevity of the clutch is thus increased.

According to other features of the invention
- the annular bead is continuous;
- the cross section of the annular bead by a plane containing the axis of rotation of the clutch is generally oblong with its largest dimension oriented radially
- The bead has two parallel planar radial faces, one of which adheres to the deposition surface portion associated with the cover or the diaphragm and the other of which cooperates, and advantageously adheres, with an annular surface portion formed vis-à- screws on the diaphragm or on the cover respectively
- the contour of the cross section of the cord has two parallel rectilinear sides, the ends of which are connected two by two by two portions in an arc
- the cross section of the annular bead is constant over its entire length
the portion of deposition surface associated with the cover or the diaphragm is a portion of planar annular surface
- the portion of the deposition surface associated with the cover or the diaphragm is an annular housing which constitutes a mold for the bead during its deposition
- the deposit surface portion is formed on a part of revolution interposed between the cover and the diaphragm
- The part of revolution is a crown comprising a planar annular portion on which the deposition surface portion is formed and comprising a convex opposite annular portion which cooperates with a planar portion facing the internal face of the cover
- The deposit surface portion is associated with the cover;
- the other of the two opposite faces of the annular peripheral part of the diaphragm cooperates, by means of an annular boss, with a surface portion formed opposite on the pressure plate, the mean diameter of the bead annular being less than the average diameter of said annular boss and the control member moving in the direction of the cover to cause disengagement
- The average diameter of the annular bead is greater than the average diameter of the annular boss and the control member moves in the direction of the pressure plate to cause disengagement.

 It will be appreciated that the oblong shape of the cord prevents it from coming loose from its deposit surface (s) during the tilting of the diaphragm. It is the same during the life of the clutch.

 When the clutch is new (friction linings of the new friction disc), the diaphragm extends transversely when the clutch is engaged.

 Following the wear of said friction linings, the diaphragm tilts so that the oblong shape of the cord limits the risks of detachment of the cord.

 It will be appreciated that the mold shape of the deposition surface further limits the risks of detachment, in particular by peeling effect, of which any sticky material is subject.

 Finally, it becomes possible, thanks to the elastic cord, to use a plastic cover reinforced for example with fibers, said cord catching up with geometric imperfections by crushing.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the accompanying drawings in which
- Figure 1 is an axial sectional view of a friction clutch with diaphragm mechanism according to the prior art, of the pushed type, and on which the clutch is illustrated in the engaged position;
- Figure 2 is a view similar to that of Figure 1 in which the clutch is illustrated in the disengaged position
- Figure 3 is a perspective view of the clutch clutch mechanism illustrated in Figures 1 and 2
- Figure 4 is a view in axial section on a larger scale of a part of a clutch illustrating a first embodiment of the invention applied to a clutch illustrated in the engaged position and whose friction linings are new;
- Figure 5 is a view similar to that of Figure 4 illustrating a second embodiment ;;
- Figure 6 is a view similar to that of Figures 4 and 5 illustrating a third embodiment of the invention
- Figure 7 is a view similar to that of Figures 4 to 6 illustrating a fourth embodiment of the invention
- Figure 8 is a partial view in axial section of a pulled clutch equipped with the cord according to the invention.

 The clutch 10, illustrated in FIGS. 1 and 2, comprises a clutch disc 12, the friction linings 14 of which are received between the parallel and opposite planar faces of a reaction plate 16 and a pressure plate 18.

The clutch 10 also includes a cover 20, here metallic, provided with an annular boss 132, which projects axially inwards and which cooperates with a first lateral face 24 of the outer annular peripheral part 26, forming a washer.
Belleville, with an elastic diaphragm 28.

 This diaphragm 28 also includes radial fingers 50, separated in pairs by slots, which extend from the internal periphery of the Belleville washer 26 to open into a central opening.

 The second lateral face 30 of the annular peripheral part 26 of the diaphragm 28, which is axially opposite to the face 24, cooperates on the one hand with an annular boss 22, here fragmented into annular sectors, which projects axially from a flat lateral face 144 of the pressure plate 18 and, on the other hand with an annular boss 36 formed on a crown ring 80 carried by the cover.

 The bosses 22 and 36 respectively constitute the primary and secondary supports for the articulation of the diaphragm in its tilting movements.

 The clutch 10 is controlled by means of a pedal connected to a clutch fork 42, which acts on a clutch release bearing 44, forming a control member, the support 46 of which is provided to cooperate with the radial ends. free interior 48 of the elastic fingers 50 of the diaphragm 28.

 The reaction plate 16 is suitable for being fixed, in particular by screws, to the crankshaft of the internal combustion engine, and usually carries a starter ring, while the clutch disc, or friction disc 12, has a hub 52 wedged in rotation, here by grooves, with the input shaft 54 of the gearbox.

 A single friction disc and a single pressure plate are shown here, but alternatively several plates and discs can be provided.

 The friction linings 14 are conventionally secured to a support and are capable of being clamped, in the engaged position, as illustrated in FIG. 1, between the plates 16 and 18.

 The disc 12 here comprises a torsion damping device. More specifically, the linings 14 extend axially on either side of the support linked by posts to guide washers, the posts connecting together the guide washers.

 These washers extend axially on either side of a hub web, with interposition of springs 56 partly housed in windows made opposite in the guide washers and in the web. The web is integral in rotation, possibly with play, with the hub 52.

 Of course, the support can be directly fixed to the hub 52, and the disc 12 can be rigid.

 The clutch being of the pushed type, the peripheral part 26 of the diaphragm 28 is mounted internally in a tilting manner on the cover using assembly means 58 tilting the diaphragm to the cover while being carried by the latter, and radially further out on the annular boss 22 carried by the pressure plate and formed here in favor of a projecting fractional projection of the plate.

 To disengage, and as can be seen in FIG. 2, it is necessary to act in thrust on the fingers 50 using the clutch release bearing 44, to tilt the diaphragm, disengage the clutch and loosen the linings 14. The cover, the pressure plate and the diaphragm form a clutch mechanism, here unitary, the pressure plate being linked in rotation to the cover by being mounted on the latter with a possibility of axial mobility, by means of tongues tangential 60 fixed, in a manner known per se, by rivets at one of their ends to the cover 20 and at their other end to lugs 62 of the pressure plate. Alternatively, the connection between the plate and the cover, with a possibility of relative axial displacement, can be of the tenon and mortise type.

 As for example described in documents FR-A-2,585,424 and FR-A-2,456,877, the assembly means 58 comprise retaining members coupled to the cover and passing axially through the diaphragm through orifices practiced therein, as well as two primary and tertiary annular supports respectively arranged opposite one another. The primary support is carried by the cover while the tertiary support is carried by the retaining members, being formed in FIGS. 1 and 2 by means of the crown ring 80.

 In the engaged position of the clutch, the diaphragm bears on the primary support, while in the disengaged position of the clutch, the diaphragm requests the tertiary support. In these documents, the assembly means 58 apply the diaphragm axially with an elastic clamping load against the primary support in the engaged position of the clutch.

 In the case of an embodiment of a clutch of the pulled type, the primary support 132 formed on the cover is located radially more outside with respect to the annular boss 22 of the pressure plate and the disengagement of the clutch is obtained by axial displacement of the clutch stop in the opposite direction of the cover, the tertiary support being removed.

 The first embodiment of the invention will now be described in detail as illustrated in FIG. 4.

 In accordance with the teachings of the invention, the annular boss 32 associated with the cover 38 consists of an annular bead, here continuous, of constant section over its entire length.

 The cord 32 is a cord made of a crosslinkable and adherent elastic material which is deposited, using a nozzle not shown, on the planar annular radial portion 34 of the internal face 21 of the cover 20 turned opposite. the face 24 of the peripheral part 26 of the diaphragm 28.

 Note that the deposit using a nozzle guarantees the thickness of the bead.

 This portion 34 will be referred to hereinafter as the support face or support portion. Here this portion 34 constitutes the internal part of the bottom of the cover 20 with a central hole. This portion 34 is offset axially relative to the other portion of said bottom and this in the direction of the plate 18 to allow tilting of the diaphragm.

 The constituent material of the cord 32 is for example a temperature-resistant silicone paste sold by the company RHONE-POULENC under the brand "RHODORSEAL".

 The cord 32 has in section through a plane containing the axis of rotation of the clutch, that is to say in the plane of the figure, considering FIG. 4, an oblong section, the largest dimension of which extends along a Ray.

 The bead comprises a first annular flat face 64 which adheres by bonding to the bearing face 34 of the cover, forming a deposition surface, at the end of the bead deposition process on this face, and a second annular planar face 66, parallel to the first face, which cooperates with the face 24 of the annular peripheral portion 26 of the diaphragm 28.

 In cross section, the cord 32 is therefore delimited by two parallel rectilinear portions corresponding to the faces 64 and 66, the outer radial ends of which are connected together by a semicircular portion 68 and the inner radial ends of which are connected together by a semicircular portion 70.

 The constant thickness of the cord 32 separating the faces 64 and 66 is obtained by the deposition process using a nozzle.

 It will be noted that the face 66 also adheres by bonding, after depositing the cord 32 on the face 34, to the face 24 of the diaphragm 28, which is placed on the cord 32 when the diaphragm 28 is mounted in the cover 20 of hollow shape. The face 24 also forms a deposition surface.

 The production of the annular boss of the pressure plate 18 is therefore particularly simple, as is the production of the cover 20 itself which requires, in this embodiment, only a portion of the annular planar internal face 34 axially offset by being devoid of '' stamped, retaining lugs and primary support.

 Due to its own elasticity, the cord 32 deforms slightly during engagement and disengagement actions of the clutch but practically does not wear out more particularly when it adheres to the cover and to the diaphragm, thus giving the mechanism of clutch very high consistency and reliability during prolonged use. In addition the cord 32, adhered to the diaphragm 20, ensures immobilization in rotation of the diaphragm. The clutch thus has a structure of a clutch of the pulled type without tertiary support.

 The slight elasticity of the cord 32 also makes it possible to ensure a play-up function and geometric imperfections of the cover.

 As this is a clutch of the pushed type, the mean diameter of the cord 32 is of course less than the mean diameter of the annular boss 22 formed on the pressure plate 18.

 Of course, the cord 32 can first be deposited on the face 24 of the diaphragm, which will then adhere to the face 34. The cover 20 or the diaphragm therefore has a deposition surface respectively 34.24.

 In the second embodiment illustrated in FIG. 5, the support portion 134 is a portion of conical surface formed on the internal face 21 of the cover 20. Thus the cord 32 works better and does not risk coming off during movements diaphragm tilting 20. The risk of peeling is therefore reduced.

 During the declutching operation, the diaphragm tilts so that the two faces become parallel.

 In the third embodiment of the invention illustrated in FIG. 6, the first planar annular face 66 of the cord 32 is deposited on a corresponding annular support portion 234 formed in the face 21 of the cover 20, which constitutes the bottom d a shaped housing 72 produced in a stamped portion in the direction opposite to the diaphragm of the face 21.

 The housing 72 is an annular groove formed in the face 21, which constitutes a partial mold of the cord 32 during deposition in order to ensure a precise geometrical position of the latter on the face 21 of the cover 20.

When the diaphragm tilts, the cord will not come off. Peeling phenomena are limited.

 In the fourth embodiment illustrated in FIG. 7, the cord 32 is not deposited directly on the face 21 of the cover, or on a portion provided for this purpose of the latter as in the case of the embodiments illustrated in Figures 4 to 6, but on an intermediate support ring 76.

 The crown 76 is a part of revolution which essentially consists of an annular central portion which extends in a radial plane parallel to the face 21 of the cover and to the face 24 of the annular peripheral portion 26 of the diaphragm 28.

 The crown 76 has a groove with a planar annular radial face 334 for depositing the bead 32 and an opposite convex face 80 which establishes rocking contact with a planar annular portion of the internal face 21 of the cover 20.

 The face 334 forms the bottom of the groove of the crown 76, said groove forming a mold for the cord 32. The face 334 is associated with the cover by being carried by the latter. In this case, the cord 32 does not need to be adhered to the diaphragm taking into account the presence of the legs 58 carrying the crown ring 80 with its support 36, said legs 58 belonging to the assembly means defined above .

 Advantageously, this crown is extended inward and includes tabs 81 interposed between the screw heads 82 screwed into the cover. As a variant, the screws 82 may consist of rivets.

 As will be understood, the crown 76 is thus prevented from rotating relative to the cover. It can tilt during the operation of the clutch, so that the cord 32 works in excellent conditions.

 Of course, the cord can be adhered to the diaphragm and the structures can be inverted, the cord 32 being interposed between the internal face of the cover and a support ring, the convex face of which is capable of cooperating with the diaphragm. In this case, the cord is adhered to the internal face of the cover and to said crown.

 The legs 58, here in one piece with the cover, extend axially and pass through the diaphragm by means of the orifices forming the blind end of the slots separating the fingers of the diaphragm in pairs. At their free end, the tabs 58 are folded radially in the direction opposite to the axis of the assembly to form a wedging bend and support for the crown ring 80 carrying the tertiary support 36.

 In all the embodiments which have just been described, the surface serving as a support for the cord 32 and to which it adheres at the end of the deposition operation, is associated directly, or indirectly by means of a support ring 76, with cover 20.

 Without departing from the scope of the invention, it is of course possible to deposit the cord 32 on the radial face 24 of the annular portion 26 of the diaphragm 28, this surface being able to be arranged, for example to include a housing forming a mold for filing the cord 32.

 Of course, in FIG. 7, the diaphragm can be mounted outside the cover, the bosses 22 of the pressure plate passing through the bottom of the cover 20. In this case, it is the external face, turned opposite of the face 21 and of the plate 18, which serves as a support and deposit surface either directly or indirectly to the cord 32.

 It will be noted that the elastic cord, made of silicone paste, hardened after being deposited, so that said support has only slight variations in thickness when the clutch passes from its engaged position to its disengaged position. As a result, the declutching stroke is not increased excessively and the lifting of the pressure plate is satisfactory.

 It will be appreciated that the oblong shape of the cord makes it possible to guarantee a certain elasticity in the cord.

 Of course, as mentioned above, the clutch can be of the pulled type (Figure 8). In this case, the cord 32 is located at the rounded zone connecting the bottom of the cover to the annular skirt of axial orientation thereof.

Claims (13)

 1. Friction clutch, in particular for a motor vehicle, of the type comprising a cover (20) and a pressure plate (18) between which is arranged an elastic diaphgrame (28) comprising an outer peripheral part (26) in the form of a washer Belleville, the inner edge of which extends radially inward by a series of elastic fingers (50), the free ends (48) of which cooperate with a clutch control member (44) which moves parallel to the axis of the clutch, and of the type in which one (24) of the two opposite faces (24, 30) of the annular peripheral part of the diaphragm cooperates with a portion facing (34) of the face (21), said first face, of the cover (20), characterized in that an annular bead (32) of crosslinkable elastic material, produced by deposition on a portion of deposition surface (34, 72) associated with the cover (18) or with the diaphragm (26) and to which the bead adheres after being deposited, is interposed between said face (24) of the annular peripheral part (26) of the diaphragm and said portion (34) of the cover (20).  2. Clutch according to claim 1, characterized in that the annular bead (32) is continuous.  3. Clutch according to one of claims 1 or 2, characterized in that the cross section of the cord (32) annular by a plane containing the axis of rotation of the clutch is generally oblong in shape with its largest dimension oriented radially.  4. Clutch according to claim 3, characterized in that the cord (32) has two parallel flat faces, one of which (64) adheres to said portion of deposition surface associated with the cover (20) or with the diaphragm (26) and the other (66) of which cooperates with an annular surface portion formed opposite the diaphragm (26) or the cover (20) respectively.  5. Clutch according to one of claims 3 or 4, characterized in that the contour of the cross section of the cord (32) has two parallel rectilinear sides (64, 66) whose ends are connected in pairs by two portions in arc of a circle (68, 70).  6. Clutch according to any one of claims 3 to 5, characterized in that the cross section of the annular bead (32) is constant.  7. Clutch according to any one of the preceding claims, characterized in that said deposition surface portion (34) associated with the cover (20) or with the diaphragm (26) is a portion of planar annular surface.  8. Clutch according to any one of claims 1 to 6, characterized in that said portion of deposition surface associated with the cover (20) or with the diaphragm (26) is an annular housing (72) which constitutes a mold for the cord (32) upon filing.  9. Clutch according to any one of the preceding claims, characterized in that said portion of deposition surface associated with the cover (20) or with the diaphragm (26) is formed on a part of revolution (76) interposed between the cover (20 ) and the diaphragm (26).  10. Clutch according to claim 9, characterized in that said part of revolution (76) is a crown comprising a planar annular portion (78) on which is formed said deposit surface portion and comprising a spaced annular convex portion which cooperates with a flat portion facing the internal face (21) of the cover.  11. Clutch according to any one of the preceding claims, characterized in that said deposit surface portion is associated with the cover.  12. Clutch according to any one of the preceding claims of the type in which the other (30) of the two opposite faces of the annular peripheral part (26) of the diaphragm (28) cooperates, by means of an annular boss ( 22), with a surface portion formed vis-à-vis the pressure plate (18), characterized in that the average diameter of the annular bead (32) is less than the average diameter of said annular boss, and in that the control member (44) moves in the direction of the cover (20) to cause disengagement.  13. Clutch according to any one of claims 1 to 11 of the type in which the other (24) of the two opposite faces of the annular peripheral part (26) of the diaphragm (28) cooperates, by means of a boss annular (22), with a surface portion formed vis-a-vis on the pressure plate (18), characterized in that the average diameter of the annular bead (32) is greater than the average diameter of said annular boss (22) , and in that the control member (44) moves in the direction of the pressure plate (18) to cause disengagement.