GB2268553A - A diaphragm clutch mechanism for a motor vehicle - Google Patents

Abstract

A diaphragm spring clutch for a motor vehicle includes a cover plate (14), a diaphragm spring (20), assembly means which mount the diaphragm spring for pivoting movement on the cover plate, and at least one pressure plate (18) on which the diaphragm spring bears. The assembly means comprise firstly a support ring (26) which is joined to the cover plate by a series of between the support ring and the cover plate (14), and rivets (28), which define a constant axial distance secondly, resiliently deformable means, in the form of a crown ring (44), which define a pivot fulcrum (48) for the diaphragm spring (20). The crown ring (44) is interposed axially between the diaphragm spring (20) and the support ring (26). The spring (20) may be outside the cover and during assembly portions (33) of rivets (28) are upset to determine the force applied to the spring by the ring (44). <IMAGE>

Description

2268553 A DIAPHRAGM CLUTCH MECHANISM FOR A MOTOR VEHICLE This invention

relates to a diaphragm clutch mechanism, especially for motor vehicles. More particularly, the invention relates to a clutch mechanism of the type comprising: a first component of generally annular shape referred to as a cover plate; a second component of generally annular shape which is referred to as a diaphragm and which has a peripheral portion defining a Belleville ring and a central portion which is divided into radial fingers by slots for cooperation with a clutch release bearing; and assembly means which apply the diaphragm to the cover plate in a pivoting relationship; and at least one plate referred to as a pressure plate, which is secured to the cover plate for rotation with the latter while being movable axially with respect to it, with the peripheral portion of the diaphragm bearing on the pressure plate.

French patent specification FR2398220A describes and shows a clutch mechanism of this type, in which the assembly means comprise: firstly, a ring which is arranged on the opposite side of the diaphragm from the cover plate, to which it is connected by means of a series of rivets which pass axially through the diaphragm and which define a constant axial distance between the ring and the cover plate; and secondly, resiliently (or elastically) deformable means which are arranged between the ring of the diaphragm and which define a pivot fulcrum for the diaphragm, in such a way that the latter is mounted pivotally between a primary fulcrum carried by the cover plate and a secondary fulcrum.,which is the pivot fulcrum mentioned above.

The above mentioned French patent specification proposes that the resiliently deformable means should be made 2 integrally with the said ring. This solution is quite satisfactory from the point of view of operation of the clutch mechanism, to the extent that it enables the gripping action of the diaphragm between its primary and secondary fulcrums to be satisfactorily controlled.

However, the single resilient member which enables the various functions to be carried out has a somewhat tortuous form. It cannot be made very thick, and this detracts from its elasticity.

In order the overcome this disadvantage in a simple and inexpensive manner.' while at the same time preserving the rivets, the invention provides a clutch mechanism, including a cover plate and a diaphragm, the diaphragm having a peripheral portion defining a Belleville ring and a central portion divided into radial fingers, with assembly means applying the diaphragm pivotally to the cover plate and to at least one pressure plate, the pressure plate being secured to the cover plate for rotation with the latter while being movable axially with respect to it, with the peripheral portion of the diaphragm bearing on the pressure plate, the said assembly means comprising: firstly, a support ring which is arranged on the opposite side of the diaphragm from the cover plate, to which it is connected by a series of rivets passing axially through the diaphragm and defining a constant axial distance between the support ring and the cover plate; and secondly, elastically deformable means which are arranged between the support ring and the diaphragm and which define a pivot fulcrum for the diaphragm, whereby the latter is mounted pivotally between, on the one hand, a primary fulcrum carried by the cover plate.4on the other hand, the said pivot fulcrum defined by the elastically deformable means and being a secondary fulcrum, the eldstically deformable means comprising a resilient crown ring interposed axially between the diaphragm and the support ring.

3 In a clutch mechanism according to the invention,the support ring can be made robust and with an increased thickness, which leads to good geometry of the support ring after riveting. This large thickness also facilitates the riveting operation itself, and renders it no longer necessary to provide a flange at the inner periphery of the support ring. The latter no longer needs to be heat treated, and it may be made as a sheet metal pressing, since it does not cooperate with the diaphragm. In addition, due to the riveting, the space between the diaphragm and the support ring.1s well controlled. This enables a crown ring of adequate size to be chosen, such that it has the advantage that it does not interfere with the rivets. This leads, especially, to a good tilting action for the diaphragm. The crown, again, does not need to be heat treated.

It will be appreciated that all of the components are simple and inexpensive, and do not require any modification of the cover plate or of the pressure plate of the clutch.

It is also possible to take the best advantage of the available space, and to increase the radial height of the support ring. This enables the size of the crown ring to be increased, which enables its flexibility or elasticity to be improved. These increases in size of the support ring and crown ring enable manufacturing tolerances to be absorbed more effectively, while also removing the need to heat treat any of the components.

In general terms, the resilient gripping action of the diaphragm between its primary and secondary pivoting fulcrums is controlled to the best advantage.

The increase in-the thickness of the support ring enables this ring to be put to further advantage. This is because, if lugs are formed on the outer periphery of the ring, it is possible to provide means which, in cooperation with a 4 reaction element or counter-abutment f ormed on the reaction plate, will limit the displacement of the pressure plate before the mechanism is mounted on the flywheel of the clutch. The support ring may also be formed with a radial i:-,dge such as to constitute an abutment which limits the inclination of the diaphragm before the clutch mechanism is mounted on the flywheel of the clutch. Because of these two last mentioned arrangements, the tangential tongues which couple the pressure plate to the cover plate for rotation together are protected, while at the same time the pressure plate is able to move axially.

According to a preferred feature of the invention, the crown ring is frustoconical in shape, and includes a rounded edge defining the said secondary fulcrum for the diaphragm.

Preferably, the rounded edge of the secondary fulcrum of the crown ring consists of an internal edge.

- Preferably, the crown ring bears through an outer edge against the lateral face of the support ring, in facing 20 relationship therewith. The support ring preferably includes centring means for centring the crown ring. According to another preferred feature of the invention, the centring means comprise an outer radial edge of the 25 support ring which is bent over axially towards the.crown ring. This outer edge may be discontinuous. According to yet another preferred feature of the invention, each of the rivets has a central body which is delimited axially by two opposed radial shoulders which 30 bears respectively against the lateral faces of the support ring and the cover plate, these lateral faces being in f acing relationship to each other, with the thickness of the support ring being greater than or equal to one half of the thickness of the diaphragm.

It will be appreciated that all these arrangements lead, especially, to a reduction in wear, and also to reduced fretting or work hardening at the contact interfaces of the diaphragm and the crown ring, the latter being due in particular to the rounded edge mentioned above.

The fact that the rounded edge constituting the second fulcrum is an internal edge enables the crown ring to be made large, such that it does not interfere with the rivets. The arrangements in accordance with the invention enable advantage to be taken of the support ring so that it can be arranged to act as a centring means. This ring can extend radially for this purpose as far as the vicinity of the bosses which are a conventional part of the pressure plate. - Further features and advantages of the invention will appear more clearly on a reading of the detailed description which follows, of a preferred embodiment of the invention. This description is given by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a view in axial cross section showing one, example of a clutch mechanism made in accordance with.

the present invention; and Figure 2 is a diagrammatic view on a larger scale, showing a detail of the mechanism shown in Figure 1.

The clutch mechanism 10 shown in Figure 1 forms a unitary assembly, and comprises a cover plate or casing 14 of generally annular shape; which is secured by means of 6 screws 16 to the.- f lywheel 12 (or reaction plate) of the clutch. The mechanism 10 also includes a pressure plate 18, which is f ixed to the cover 14 by means of elastic tongues 3; and a diaphragm 20. In the present example, each tongue is fixed by riveting, in the conventional way, at one of its ends to a lug of the pressure plate 18 (see Figure 1). At its other end each tongue is secured to the radial edge of the cover plate 4. As shown, the cover plate 14 is in the form of a dished plate.

In a known manner, the diaphragm 20 causes the friction liners of the friction disc 2 of the clutch to be gripped between the pressure plate 18 and the reaction plate 12.

The diaphragm 20 comprises a peripheral portion 22 (Figure 2) constituting a resilient ring of the Belleville ring type. The diaphragm bears on a boss 7 through the outer periphery of its Belleville ring portion. The boss 7 is conventionally divided up into a plurality of separate bosses or pads, and is formed in the pressure plate 18.

The diaphragm is arranged to be pivotally mounted, through the inner periphery of its Belleville ring portion, between two fulcrums, referred to as a primary fulcrum and secondary fulcrum respectively, which are carried in generally facing relationship by the cover plate 14 in a manner to be described below.

The diaphragm 20 also has a central portion which consists of a set of radial fingers 24, which are separated from each other by slots which extend from passages or holes 40 (Figure 2), formed at the inner periphery of the peripheral portion 22 of the diaphragm 20. The diaphragm is engaged pivotally with the cover plate 14 by assembly means, comprising a support ring or crown 26, which is fixed to the dish-shaped cover plate 14 by means of a series of rivets 28 which are secured on the base portion of the cover plate 14. This base portion is open in the centre' to define a central axis 4 of the clutch mechanism.

7 The rivets 28 are, spaced apart at regular intervals on a common pitch circle on the general axis 4 of the mechanism.

Each rivet comprises a central rivet body 13 which is delimited axially by two opposed radial shoulders 32, 34.

The radial shoulder 34 bears against the lateral, opposed, face 36 of the support ring 26, while the radial shoulder 34 bears axially against the internal, opposed, face 38 of the cover plate 14. The rivets 28 thus secure the support ring 26 on the cover plate 14, while maintaining a constant predetermined axial distance between the two faces 36, 38.

The rivets 28 extend axially through the holes 40, which are provided in the diaphragm 20 for this purpose.

The inner face 38 of the cover plate 14 carries a pointed annular boss 42, which is divided into separate sections for mounting the rivets 28, and which constitutes the primary fulcrum for the pivoting action of the Belleville ring portion 22 of the diaphragm 20. In a modification, the primary fulcrum may be def ined by a ring which is a component separate from the cover plate itself, or alternatively it may be f ormed, by a pressing operation, in the base portion of the cover plate.

The assembly means mentioned above also include a resilient crown ring 44, which is frustoconical in shape in this example, and which is disposed axially between the inner face 36 of the support ring 26 and the lateral face 46 of the diaphragm 20 which is in facing relationship with the.

inner face 36. The crown ring 44 has a radially inner edge.

48 of rounded convex form, which cooperates with the lateral face 46 of the diaphragm 20 so as to define the secondary fulcrum for pivoting of the diaphragm 20. Both the primary fulcrum 42 and the secondary fulcrum 48 give point contact, and lie on pitch circles in a common cylindrical plane coaxial with the main axis 4.

The crown ring 44 also has a sharp-angled radially outer 8 edge 50 which bears against the inner face 36 of the support ring 26.

The rivets 28 pass centrally (with a clearance) through the crown 44, which is centred by means of the rounded radially outer edge portion 52 of the support ring 26. This edge portion 52 is bent over partially in the axial direction towards the crown ring 44, so as to define a bend 54 for centring the crown ring 44. It will be seen that the resilient, frustoconical crown 44 bears at its outer periphery on this support ring 26, while at its inner periphery it bears on the diaphragm 20, its inclination being such as to enable the diaphragm 20 to move pivotally as the friction liners of the friction disc 20 of the clutch become worn.

It will be appreciated that the support ring 26 and the crown ring 24 are robust components, and that they are relatively thick. They can be made in pressed sheet metal, and need not be heat treated. In the present example, these components have a thickness which is at least equal to (and is in practice greater than) one half of the thickness of the diaphragm 20, while the support ring 26 is of large radial height. It extends as far as the radial level of the inner periphery of the bosses 7, in the vicinity of the latter. Its outer edge 52 thus extends to the vicinity of the bosses 7, and also stiffens the support ring 26) As a result, the crown ring 44 can be made with a large radial height, which is generally advantageous.

The characteristic curve of this crown ring is in practice determined in particular by the height of the frustum of its cone and by its thickness, in such a way that by increasing its thickness it is possible to have a characteristic curve (i.e. the curve of variation in force with the extent of deformation of the diaphragm) which does not have a pronounced peak. This enables a substantially 9 constant load to be obtained at the summit of the characteristic curve.

In the present example, and in practice, the crown ring 44 has a thickness which is greater than that of the support ring 26, so as to exert, after assembly, a substantially constant load on the diaphragm, especially when the latter pivots between its primary and secondary fulcrums. An elastic gripping effect is thus given by the diaphragm.

Preferably, and in the usual way, the gripping action is chosen to be such that the diaphragm 20 remains permanently in contact with its primary fulcrum during actuation of the clutch as described below, so that there are no losses from lifting of the pressure plate.

The arrangement described above and shown in the drawings provides good control of the elastic load exerted by the crown ring 44 on the diaphragm 20, and this leads to a reduction in hysteresis effects.

The thickness of the crown ring 44 does of course depend on the particular application, and it may be either equal to, or less than, the thickness of the support ring 26. In this way good tilting action of the diaphragm is obtained.

It will be recalled that the clutch mechanism 10 is adapted to be carried by means of its cover plate 14 on the reaction plate 12 (or flywheel) of the clutch. The flywheel is in this instance fixed on the crankshaft of the engine of a motor vehicle, and is rotatable with it. The friction disc (or clutch friction wheel) 2 is inserted between the reaction plate 12 and the pressure plate 18, and is secured to the input shaft 5 of the gearbox of the vehicle, f or rotation with this shaft 5. Around the gearbox input shaft there is arranged a component known as a clutch release bearing, which is arranged to act on the ends of the f ingers 24 of the diaphragm 20 (in the direction of the arrows F shown in.Figure 1) so as to actuate the clutch in a disengaging mode. The clutch is normally engaged, with the pressure plate 18 gripping the clutch friction wheel 4 against the reaction plate 12 under the biasing action of the diaphragm.

Due to the force exerted on the ends of the fingers 24 of the diaphragm, the latter is caused to pivot between the crown ring 44 and the boss 42 on the cover plate 14.

During this pivoting movement, the tangential resilient tongues 3, which connect the presbure plate 18 to the cover plate 14 for rotation together but with axial mobility, bias the pressure plate 18 towards the base portion of the cover plate 14, which enables the pressure plate 18 to be released and so disengage the clutch friction wheel 2.

is The assembly of the clutch mechanism described above is carried out in the following way.

The sub-assembly consisting of the support ring 26 and the set of rivets 28 is f irst made by securing the rivets 28 to the ring 26 by upsetting their heads 31. To this end, the rivet heads 31, are preferably provided with blind central holes to facilitate this upsetting operation. The crown ring 44, the diaphragm 22, and finally the cover plate 14 are then threaded axially on to this sub-assembly in that order. As the cover plate is fitted, its internal face 38 is brought into engagement against the radial shoulders 34 of the rivets 28. After that, it is merely necessary to upset the foot portions 33 of the rivets 28 (again having central blind holes), to complete the assembly and to enable the axial gripping f orce which is applied to the diaphragm 20 by the crown ring 44 to be guaranteed with precision.

In this connection, it has been proposed, f or example in United 'States patent specification No 4039059, to use a cone-shaped assembly component, with the f ree ends of the projecting teeth of this component being bent over. Such bending does not enable the gripping of the diaphragm to be controlled satisfactorily, and it makes it necessary to increase the gripping force if there is a requirement that the diaphragm should not become separated from its primary fulcrum while being actuated by the clutch release bearing.

The arrangement according to the invention described above reduces the gripping force and thus reduces the frictional effects and hysteresis effects during actuation of the diaphragm. The assembly means whereby the diaphragm 20 is mounted pivotally on the cover plate 14 thus consists of a series of components having particularly simple shapes and designs, which are inexpensive to manufacture and which can in addition be assembled in a reliable and inexpensive manner.

The present invention is of course not limited to the embodiment described above. In particular, the diaphragm may be mounted outside the cover plate, and outside the support ring 26 and crown ring 44, with the bosses 7 of the pressure plate 18 then passing through the base portion of the cover plate, via apertures provided for this purpose in the latter.

In all cases, the rivets 28 are carried by the base portion of the cover plate 14, which has the general shape of a hollow dish with a central hole in its base portion.

The crown ring may have a U-shaped cross section as disclosed in the above mentioned US patent specification

No. 4039059.

The invention also enables a further advantage to be obtained having regard to the fact that the thickness of the support ring 26 may be as large as may be desired. In 12 this connection, and as indicated in broken lines at 152 in Figure 2, the outer edge 25 of the ring 26 may be extended so that the resulting extension serves as an abutment for the diaphragm when (in its storage position) the clutch mechanism 10 is not yet fitted on the flywheel 12. This helps to preserve the tongues 3.

Radial lugs 53 may be formed on the outer periphery of the support ring 26, these lugs projecting radially and penetrating (with a clearance) into an aperture 55 which is formed the level of the bosses 7 in the pressure plate 18.

The purpose of this is to limit the movement of the pressure plate 18, and again to preserve the tongues 3, during storage when the mechanism 10 is not mounted on the flywheel 12, by cooperation with the radial face 57 of the aperture 55. In that case, the outer edge portion, or flange 52, of the support ring 26 is of interrupted form so as to define the lugs 53.

It will be noted that the radial f ace 57 of the aperture 55 (in facing relationship to the cover plate 14) constitutes a reaction surface which is adapted to cooperate with the lugs 53, the latter constituting an abutment which prevents deterioration of the tongues 3. The tongues are thereby protected.

The aperture 55 is preferably in the form of a groove made by turning, the lugs 53 cooperating with the aperture to f orm a bayonet type f itting. These lugs 53 have, quite simply, a width which is at least equal to the circumferential distance which separates two of the bosses 7 from each other. The lugs are thus introduced between two bosses 7, and the pressure plate 18 is then rotated with respect to the cover plate 14. Finally the tongues 3 are secured to the cover plate 14, having for example been riveted in advance to lugs of the pressure plate 18. - 13

Claims (11)

1. A clutch mechanism, including a cover plate and a diaphragm, the diaphragm having a peripheral portion defining a Belleville ring and a central portion divided into radial fingers, with assembly means applying the diaphragm pivotally to the cover plate and to at least qne pressure plate, the pressure plate being secured to the cover plate for rotation with the latter while being movable axially with respect to it, with the peripheral portion of the diaphragm bearing on the pressure plate, the said assembly means comprising: firstly, a support ring which is arranged on the opposite side of the diaphragm from the cover plate, to which it is connected by a series of rivets passing axially through the diaphragm and defining a constant axial distance between the support ring and the cover plate; and secondly, elastically deformable means which are arranged between the support ring and the diaphragm and which define a pivot fulcrum for the diaphragm, whereby the latter is mounted pivotally between, on the one hand., a primary fulcrum carried by the cover plate and, on the other hand, the said pivot fulcrum defined by the elastically deformable means and being a secondary fulcrum, wherein the elastically deformable means comprise a resilient crown ring interposed axially between the diaphragm and the support ring.

2. A clutch mechanism according to Claim 1, wherein the crown ring bears at its outer periphery on the support ring and at its inner periphery on the diaphragm.

3. A clutch mechanism according to Claim 1 or claim 2, wherein the crown ring is frustoconical in shape and includes a rounded edge defining the said secondary fulcrum.

14

4. A clutch mechanism according to Claim 3, wherein the rounded edge is an inner edge.

5. A clutch mechanism according to Claim 4, wherein the crown ring bears through an outer edge against the lateral face of the support ring, in facing relationship therewith.

6. A clutch mechanism according to any one of the preceding Claims, wherein the support ring includes centring means for centring the crown ring.

7. A clutch mechanism according to Claim 6 in combination with Claim 5, wherein the centring means comprise an outer radial edge of the support ring, which is bent over axially towards the crown ring.

8. A clutch mechanism according to any one of the preceding claims, wherein each of the rivets has a central is body which is delimited axially by two opposed radial shoulders, which bear against the respective lateral faces, in facing relationship therewith, of the support ring and cover plate respectively, the thickness of the support ring being greater than or equal to one half of the thickness of the diaphragm.

9. A clutch mechanism according to any one of the preceding Claims, wherein the pressure plate has a boss for engagement with the diaphragm, the support ring extending radially to the vicinity of the inner periphery of the boss.

10. A clutch mechanism according to Claim 9, wherein the support ring has at its inner periphery a plurality of lugs projecting radially therefrom, and penetrating, with a clearance, into an aperture formed at the level of the engagement bosses formed on the pressure plate for engagement with the diaphragm, the said lugs being adapted is to cooperate with a f ace of the said aperture so as to limit displacement of the pressure plate.

4

11. A clutch mechanism substantially described in the 1 foregoing description with reference to the accompanying 5drawings.