GB2153489A

GB2153489A - Torsion absorber device for a clutch

Info

Publication number: GB2153489A
Application number: GB08432808A
Authority: GB
Inventors: Carlo Beccaris; Ernesto Lanzarini
Original assignee: Valeo SE
Current assignee: Valeo SE
Priority date: 1983-12-30
Filing date: 1984-12-31
Publication date: 1985-08-21
Also published as: FR2557656B1; FR2557656A1; GB8432808D0; IT8412668A0; JPS60234127A; DE3447653A1; IT1181329B; GB2153489B

Abstract

A clutch centre plate comprises two coaxial parts 10,11 mounted to rotate relative to each other counter to a suitable elastic member 27 for ensuring their return to a mean rest position. According to the invention, the elastic member 27 is a simple block of elastic material whose circumferential ends, devoid of any coating, are capable of coming directly to bear against the corresponding shoulders 32,33 of the coaxial parts 10,11 between which it is inserted circumferentially. The shoulders 33 of the part 11 are oblique to the shoulders 32 of the part 10, and at least the shoulders 32 of the part 10 are oblique relative to each other to form a dovetail slot. <IMAGE>

Description

SPECIFICATION Torsion absorber device for a clutch The present invention relates in a general manner to the torsion absorber devices of the kind incorporating at least two coaxial parts mounted so as to rotate relative to each other, within the limits of a specified angular clearance, and counter to elastic means inserted circumferentially between them and called, for convenience, elastic means with circumferential action.

As is known, such a torsion absorber device usually forms part of the composition of a clutch friction, particularly for a motor vehicle, in which case one of its rotating parts carries a friction disc intended to be unified in rotation with a first shaft, in practice a driving shaft, the engine output shaft in the case of a motor vehicle,'whilst another of the said coaxial parts incorporates a hub by which it is intended to be unified in rotation with a second shaft, in practice a driven shaft, the input shaft of a gearbox in the case applying to a motor vehicle, or consists of such a hub.

In fact, such a device makes it possible to ensure a controlled transmission of the rotation torque applied to one of these rotary parts, while the other is itself the object of a rotation torque, that is to say to filter the vibrations which can be generated throughout the kinematic chain extending from the engine to the controlled wheel shafts in a motor vehicle in which it is fitted.

The present invention is more particularly aimed at the case where, in order to define the angular clearance between two coaxial parts of such a torsion absorber device, means are provided between these parts for meshing, with play, in cooperation with suitable centering means for loading the said coaxial parts circumferentially in the direction of a rest position intermediate between the limits of their said angular clearance.

This is the case, for example, in the torsion absorber device which is the subject of the French Patent filed on 29 August 1973 under No.73/31,172 and published under No. 2,242,606, and in the device which is the subject of the first,Certificate of Addition which, filed on 12 April 1974 under No. 74/12,915 and published under No. 2,270,491, is appended to this French Patent.

In both cases, the torsion absorber device in question in practice incorporates three coaxial parts which are successively rotary in pairs, and those between which meshing means with play are provided are those intended to come into action at low torque values.

Also, in practice, the centering means provided between these coaxial parts to load them in the direction of a rest position incorporate at least one elastic m em ber which, forming part of the elastic means with circumferential action which are inserted between the said coaxial parts, is placed in the region of the means for meshing these parts with play and is capable, in the rest position of these coaxial parts, of coming to bear, with each of its circumferential ends, on a shoulder of each of the said coaxial parts.

More precisely, in the abovementioned French Patent No.73/31,172, and in the first Certificate of Addition No. 74/12,915 attached thereto, a spring, of the coil spring type, is involved.

For better bearing of this spring at its circumferential ends, and thus for its better retention, provision is made, in the French Patent in question and in its first Certificate of Addition, for associating with each of the said circumferential ends of this spring a bearing plate suitable for being inserted between the latter and the corresponding shoulders of the two coaxial parts involved, with, in the case of the said first Certificate of Addition, interlocking means according to which the said shoulders are oblique relative to each other, the shoulders which are thus incorporated in at least one of the coaxial parts being themselves oblique relative to each other after the fashion of the sides of a dovetail slot.

This arrangement with a spring and bearing plates, which has been satisfactory and may remain satisfactory, has the disadvantage of requiring the use of several individual components.

The subject of the present invention, is, in a general manner, a device enabling this disadvantage to be avoided, and additionally resulting in other advantages.

It is based on the a priori surprising observation that there is no need, finally, to use bearing plates when the elastic centering member in question is a simple block of an elastic material, despite the risk of shearing or tearing which might have been expected, on the contrary, for this elastic member in contact with the shoulders in question of the two coaxial parts involved, and this even when each of these shoulders in practice consists of the section, with a necessarily reduced axial extent, of a metal flange.

More precisely, the subject of the present invention is a torsion absorber device, particularly for a motor vehicle clutch, of the type incorporating at least two coaxial parts mounted so as to rotate relative to each other counter to elastic means inserted circumferentially between them called, for convenience, elastic means with circumferential action, and within the limits of an angular clearance determined by means for meshing with play which are provided for this purpose between the said coaxial parts, in cooperation with suitable centering means for loading the said coaxial parts circumferentially in the direction of a rest position intermediate between the limits of their said angular clearance, the said centering means incorporating at least one elastic member which, belonging to the said elastic means with circumferential action, is placed in the region of the means for meshing the said coaxial parts with play and is capable, in the rest position of the latter, of coming to bear with each of its circumferential ends on shoulders of the said coaxial parts which are oblique relative to each other, the shoulders which are thus incorporated in at least one of the coaxial parts being themselves oblique relative to each other after the fashion of the sides of a dovetail slot, characterised in that the said elastic member is a simple block of an elastic material which is elongated circumferentially, substantially tangentially relative to a circumference of the assembly, the circumferential ends of which, which are devoid of any coating, are capable of coming directly to bear on the corresponding shoulders of the coaxial parts between which it is inserted circumferentially.

Thus, a single component is sufficient to form the centering means to be used.

The fitting of the assembly is advantageously simplified thereby.

In addition, since the elastic member which in practice forms these elastic centering means is made of an elastic material, it is particularly suitable for absorbing neutral-position noises, of the type of those which are usually produced at the low torque value at which, in actual fact, it comes into action.

In fact, since the stiffness of such an elastic material usually varies with the temperature, being higher when it is cold than when hot, it follows, itself, the change in the resistance offered to the driven shaft which, being due particularly to the viscosity of the oil in which the gearbox pinions are immersed, is itself usually higher when it is cold than when it is hot.

To be sure, in Swiss Patent No. 199,262 blocks or bodies made of an elastic material are employed, but these are generally rounded in shape, forming, for example, spheres or ellipsoids and, in order that they may be protected "from any cut", the edges of the cavities in which they are housed are themselves rounded; no shoulders are therefore involved and, what is even more, no shoulders which are oblique relative to each other.

This is also substantially so in French Patent No.

2,176,335, in which, in the case of at least one of the coaxial parts, the housing of each of the blocks of elastic material employed takes place in a simple, very widely rounded recess without individualisation of any shoulders at its ends.

There is nothing in either of these patents that would enable one to expect the good behaviour of the block of elastic material employed according to the invention, under the conditions under which it is used.

This good behaviour is furthermore all the more surprising in that, on the one hand, in the case of at least one of the coaxial parts involved, the two shoulders with which each of the two circumferential ends of this block of elastic material are to cooperate respectively, are oblique relative to each other, after the fashion of the sides of a dovetail slot, and in that this results in the presence, in this coaxial part, of relatively sharp noses each directed respectively towards the median zone of the said circumferential ends, and in that, on the other hand, such a block of elastic material is called upon in use to work substantially in shear, and is thus especially stressed by the shoulders between which it is then engaged.

The features and advantages of the invention will emerge, furthermore, from the description which follows, by way of example, with reference to the attached diagrammatic drawings, in which: Figure lisa partial elevation of a torsion absorber device according to the invention along the arrow I of Figure 2, and with a local cut-away; Figure 2 is a view in axial section along the broken line Il-Il of Figure 1; Figure 3 is a partial view of it in cross-section along the line Ill-Ill of Figure 2, on a larger scale, for the rest position of the two coaxial parts involved; Figure 4 is an end view along the arrow IV of Figure 3, of the elastic centering member used according to the invention; Figure 5is a view similarto that of Figure 3, for another position of the coaxial parts involved;; Figure 6 is a view similar to that of Figure 4 and refers to an alternative embodiment; Figure 7 is a view similar to that of Figure 3, for an alternaive embodiment of the elastic centering member used according to the invention; Figure 8, which repeats a part of Figure 7, is a view in lengthwise section of this elastic centering member, shown in isolation; Figure 9 is a view in cross-section, along the line IX-IX of Figure 8; Figure 10 repeats, on a larger scale, the detail of Figure 8 which is marked as an inset X on the latter; Figures 11,12,13, and 15 are views in lengthwise section, which are all similar to that of Figure 8 and each of which refers respectively to an alternative embodiment of the elastic centering member employed in the torsion absorber device according to the invention;; Figure 16 is a partial view in cross-section of the elastic centering member shown in Figure 15, along the line XVI-XVl of the latter; Figure 17 is a view in cross-section, which is similar to that of Figure 16 and relates to an alternative embodiment.

These figures illustrate, by way of example, the application of the invention to a torsion absorber device which, being intended to form a clutch friction for a motor vehicle clutch, incorporates, mounted successively so as to rotate in pairs relative to each other, three coaxial parts, namely, a part A, consisting substantially of a hub 10, a part B, consisting substantially of an annular flange 11, or hub web, surrounding the hub 10, in the median part of the latter, and a part C, consisting substantially of two annular flanges 12, or guiding discs which, each being arranged respectively on either side of the hub web 11, and, like it, surrounding the hub 10, are connected together, in places, by small axial columns 14 passing with a clearance through the cavities 15 provided for this purpose in the said hub web 11.

Since, in practice, a clutch friction is involved, the coaxial part C carries a friction disc 16, whose web 17, which may be circularly sectioned into blades if appropriate, is attached by rivets 18 to one of the guiding discs 12, and whose friction linings 20, each arranged respectively on either side of the said web 17, are intended to be clamped between two plates connected in rotation to a first shaft, in practice a driving shaft, the engine output shaft in the case where such a motor vehicle is concerned.

Conjointly, the hub 10 comprised in the coaxial partA has, internally, channels 21, by means of which it is made capable of being locked in rotation with a second shaft, in practice a driven shaft, the input shaft of the associated gearbox, in the case of such a motor vehicle.

The two coaxial parts A, B are mounted so as to rotate relative to each other, counter to elastic means inserted circumferentially between them and called, for convenience, elastic means with circumferential action, and within the limits of an angular clearance determined by the means for meshing with play 22 provided for this purpose between the said coaxial parts A and B.

In practice, to form these means for meshing with play 22, the hub 10 has, projecting radially on its outer surface, in the median zone of the latter, a peripheral section 23 on which radial teeth 24 are distributed in a circle.

Conjointly, the hub web 11 has, on its inner periphery, opposite the peripheral section 23 ofthe hub 10, recesses 25, by means of which it is engaged, with play, their angular opening being greater, in the teeth 24 of the hub 10.

As can be readily understood, the angular clearance which is possible between the coaxial parts A, B is limited in either direction by the corresponding coming into abutment of the teeth 24 of the hub 10 with the corresponding sides of the recesses 25 of the hub web 11.

Associated with the means for meshing with play 22 which ensure this restriction are suitable centering means for loading circumferentially the coaxial parts A, B in the direction of a rest position intermediate between the limits of their annular clearance.

In practice, these centering means incorporate at least one elastic member 27 which, belonging to the elastic means with circumferential action and being located between the coaxial parts A, B, is placed in the zone of the means for meshing with play 22 of the latter.

In practice, in the embodiment shown, only one such elastic member 27 is provided and it forms on its own the elastic means with circumferential action which are inserted between the coaxial parts A, B.

In other words, this elastic member 27 forms both the elastic means with circumferential action and the associated centering means.

In a manner known per se, this elastic member 27 is arranged radially between the hub 10 and the hub web 11, in a housing 29 formed by two recesses 30, 31, the first of which is arranged between two teeth 24 of the hub 10, and the second between two recesses 25 of the hub web 11 Each of these two recesses 30,31 is bounded circumferentially, and at each of their ends, by a shoulder, 32,33 respectively, and in practice they are the result of grooves, with being arranged radially, have led locally to the elimination of one or more teeth and recesses 24, 25.

In the case of the recess 30, that arranged between two teeth 24 of the hub 10, each of the shoulders 32 is overall oblique relative to a radial direction of the assembly passing through their median zone, and they are thus generally oblique relative to each other, approaching each other, in a direction away from the axis of the assembly, after the fashion of the sides of a dovetail slot.

As will be noted, each of these shoulders 32 also defines, with the peripheral section 23 of the hub 10 on which the teeth 24 of the latter are projecting, noses 34 generally directed circumferentially towards each other, and relatively sharp.

In the case of the recess 31, that formed between two recesses 25 of the hub web 11, each of the shoulders 33 extends generally along a radial direction of the assembly.

However, on account of the obliqueness of the shoulders 32 of the associated recess 30, the shoulders 32,33 which thus generally form the circumferential ends of the housing 29 of the elastic member 27 are generally relative to each other at each of the circumferential ends of this housing 29, and therefore they form a dihedron.

In the rest position of the coaxial parts A, B, shown in Figure 3, the elastic member 27 bears with each of its circumferential ends on the corresponding shoulder 32, 33 of each of the coaxial parts A, B.

In such a rest position, there may then remain, as shown, the same play J on either side of each of the teeth 24 of the hub 10, between the sides of this tooth and the corresponding sides of the recess 25 which is engaged on it.

However, alternatively, it is also possible to provide different plays on either side of each of the teeth 24 of the hub 10 in this rest position.

According to the invention, the elastic member 27 is a simple block of elastic material the circumferential ends of which, devoid of any coating, are capable of coming directly to bear on the corresponding shoulders 32, 33 of the coaxial parts A, B between which it is inserted circumferentially.

Each of these circumferential ends forms, as a hollow, to match these shoulders 32,33, at least one dihedron the edge a of which extends substantially in the median zone of such a circumferential end.

In the embodiment which is shown more particularly in Figures 1 to 5 only one such dihedron is thus provided at each of the circumferential ends of the block of elastic material forming the elastic member 27.

In practice, the latter is elongated circumferentially in the shape of a cylinder and it extends substantially tangentially relative to a circumference of the assembly; in the embodiment shown, its cross-section is circular.

As a result of the dihedral configuration of these circumferential ends, the radial retention of this block of elastic material is always ensured in a suitable manner.

This is so especially in the case of the rest configuration of the assembly, Figures 1 and 3, in which, with its circumferential ends, it is engaged with one or other of the shoulders, or sides, of the dovetail slot 30 of the hub 10.

Conjointly, the coaxial parts B, C are themselves mounted to rotate relative to each other counter to elastic means inserted circumferentially between them and consisting, in the embodiment shown, of springs 35A, 35B, 35C, of the coil spring type, extending substantially tangentially to the same circumference of the assembly and arranged partly in the windows 36A, 36B, 36C provided for this purpose in the hub web 11 in continuity with the passages 15 incorporated in the latter for the axial struts 14, and, partly, in the windows 37A, 37B, 37C which are also provided for this purpose in the guiding discs 12.

In ;.rye case of the springs 35A, the windows 36A, 37A have the same circumferential development.

On the other hand, in the case of the springs 35B, 35C, the circumferential development of the windows 36B, 36C is greater than that of the windows 37B, 37C, the corresponding play being greater for the springs 35C than for the springs 35B.

The angular clearance between the coaxial parts B, C is restricted either by the turns of any one of the springs 36A, 36B, 36C coming into contact, or by the contact of at least one of the axial struts 14 with the corresponding circumferential edge of the passage 15 in the hub web 11 through which it passes.

These arrangements are well known in themselves and, as they do not form part of the present invention, they will not be described here in greater detail.

Similarly, according to arrangements which are well known in themselves, friction means, which will not be detailed here, are provided between the coaxial parts A, B, C, being controlled by elastic means with axial action.

In practice, the stiffness of the elastic member 27 which is formed by the block of elastic material according to the invention is very much lower than that of the springs 36A, 36B, 36C.

Consequently, in use, when a torque is applied to the coaxial part C, for example in the direction shown by the arrow F in Figures 1,3 and 5, only this elastic member 27 yields elastically at first, until the teeth 24 of the hub 10 come into abutment against the corresponding side of the recesses 25 of the hub web 11, FigureS.

As will be noted, in the course of such action, the elastic member 27, which operates substantially in shear, is subjected to a slight tilting motion, along the arrow F' of Figure 5, around the nose 34 of the hub 10 on which it is then bearing.

As the torque to be transmitted increases, the springs 35Acome into action in their turn and then, in succession, as a function of the play between their corresponding windows 36B-37B and 36C-37C, first the springs 35B and finally the springs 35C.

Conjointly, the elastic member 27 remains compressed.

When the torque is changing in the reverse direction, it applies, between the coaxial parts A, B, a return load until these coaxial parts A, B return to their initial mean rest position in which their respective shoulders 32, 33 are opposite each other.

According to the embodiment shown in Figure 6, each of the circumferential ends of the block of elastic material forming the elastic member 27 forms, as a hollow, two dihedra with ridges a, a' which are crossed in directions which are substantially at right angles.

This makes it easier to install this block of elastic material in its housing 29.

Preferably, and as shown, at each of the circumferential ends of the elastic member 27, the ridges formed by the lateral sides 39 of the latter with the dihedron forming such a circumferential end are each relieved by a more or less pronounced chamfer 41, despite the resulting reduction of land.

The chamfers 41 which are thus used are intended to promote, during operation, the production of a suitable bearing of the elastic member 27 on the circumferential end, involved at this time, of the recess 31 of its housing 29, these ends being rounded, and the chamfers thus advantageously enable the elastic member to avoid being then driven outwards radially.

Preferably, and as shown, such chamfers are provided both at the ends of that one of the Lateral sides of the elastic member 27 which, being tangential to a circumference of the assembly, is radially the nearest to the axis of the assembly, and at the ends of that which, being also tangential to a circumference of the assembly, is radially the furthest from the said axis.

The elastic member 27 may thus advantageously be installed in either direction, regardiess.

In the embodiments shown in Figures 7 to 17, the cross-section of the cylinder formed by the block of elastic material forming the elastic member 27 is generally quadrangular.

Lengthwise, this elastic member 27 thus has, in parallel with each other, two lateral sides 39, which are generally planar and each of which extends substantially tangentially relative to a circumference of the assembly and, perpendicularly to these, two lateral sides 40 which are also planar and each of which extends substantially transversely relative to the said axis of the assembly, Figures 8 and 9.

Furthermore, in these embodiments, this elastic member 27 has, as a hollow, an undercut 38 in the median zone of each of its circumferential ends.

In practice, this undercut 38 cuts away the ridge a of the corresponding dihedron.

In the embodiment shown, this undercut 38 is an generally semi-cylindrical undercut, with generating lines parallel to the axis of the assembly, and, in cross-section, it has a circular contour with a centre angle 0 greater than 180 , Figure 10.

By virtue of such an undercut 38, the elastic member 27 is spared, in use, from any punching action due to the corresponding nose 34 of the coaxial part A, to the advantage of its durability.

In fact, during its tilting motion, everything happens as if, with this undercut 38, it came round the end of such a nose 34 while continuing to bear on it, while the other end of this nose 34 enters the said undercut 38.

In the preceding, the block of elastic material forming the elastic member 27 is solid and massive and its lateral sides 39,40 are flat and smooth.

Such a block, the hardness of which should be relatively high for it to be able to cooperate directly, without risk of damage, with the shoulders 32,33 of the coaxial parts A, B, has, unless required otherwise, a stiffness reflecting this hardness.

In an alternative form, and depending on the improvements which are subjects of the present invention, arrangements are made to reduce this stiffness.

For example Figure 11 between its circumferential ends, the elastic member 27 has, on at least one of its lateral sides 39, 40, an inside recess 42, with the result that, in its median zone, it has transversely a length of reduced cross-section 43.

In practice, the elastic member 27 thus has an inside recess 42 on each of those, 39, of its lateral sides, each of which extends substantially tangentially relative to a circumference of the assembly.

In the embodiment shown, such an inside recess 42, which is of reduced depth P, generally smaller than one half of the thickness E of the elastic member 27 in its running part, extends over a considerable portion, for example of the order of one half, of the length of this elastic member 27.

Alternatively Figure 12 the elastic member 27 has, counting from those, 39, of its lateral sides, each of which extends substantially tangentially relative to a circumference of the assembly, recesses 45, and these recesses 45 are circumferentially alternating relative to each other from one of the said lateral sides 39 to the other.

In practice, there is an even number of recesses 45 on one of the lateral sides 39, for example two, and an odd number, for example one, on the other of these.

In other words, there is a number of recesses 45 on one of these lateral sides 39 which is greater by one unit than the number of recesses 45 on the other.

Despite the alternation of these recesses 45, a symmetry can thus be preserved in the case of the elastic member 27, with one recess in its median transversal plane for one of its lateral sides 39, which, as before, advantageously enables itto be installed in either direction regardless.

Preferably, however, that of its lateral sides 39 which incorporates a larger number of recesses 45 is its side which is radially the furthest from the axis of the assembly.

In the embodiment shown, each of the recesses 45, each of which is of reduced width, has a depth P' which is at least equal to one half of the thickness E of the elastic member 27 in its running part, being, for example, slightly greater than the said one half of it.

Alternatively Figures 13 to 17 the elastic member 27 incorporates, from one to the other of those, 40, of its lateral sides which extend substantially transversely relative to the axis of the assembly, at least one cavity which passes through it in parts, substantially in parallel to the said axis, and the said cavity extends substantially in equal fashion on either side of its median plane M.

In practice, with several such cavities provided, each of them extends substantially in equal fashion on either side of the median plane M of the elastic member 27, being substantially aligned along the said plane M.

This median plane M is shown diagrammatically as broken lines in its path in Figures 13, 14.

In the embodiment shown in greater detail in Figure 13, two cavities 47 are thus provided in the elastic member 27, and these are cavities which have a generally polygonal contour in transverse section, being separated from each other by a straight median partition 48.

In practice, the sides of such a cavity 47 which are close to the lateral sides 39 of the elastic member 27 are substantially parallel to the latter sides, and their sides which are close to the corresponding circumferential end of this elastic member 27 form a dihedron, reflecting that formed by such a circumferential end.

In addition, corresponding to the inside recess 38 present as a hollow at each of the circumferential ends of the elastic member 27 there is, projecting inwards, in the cavity 47 close to such a circumferential end, a boss 49 the contour of which is substantially complementary to that of the said inside recess 38.

In other words, setting aside that of its sides which is defined by the straight median partition 48, the sides or flanks of each of the cavities 47 of the elastic member 27 are each derived respectively by a simple translation of the corresponding sides or flanks of this elastic member 27.

The result of this is that, for each of the circumferential ends, the elastic member 27 is equally thick at all points and that, similarly, setting aside its straight median partition 48, it has the same thickness along its lateral sides 39, at all points of the latter.

In other words, the elastic member 27 is uniformly thick, both at its circumferential ends and along its lateral sides 39 Its casting conditions are made more favourable thereby.

Be that as it may, and as shown diagrammatically by broken lines in Figure 13, the cavities 47 which it incorporates also promote a parallelogram distortion of the assembly, which advantageously combines with its work under shear in use.

In fact, as a result of the fact that the cavities 47 are aligned along the median plane M, only the stiffness along this median plane M is reduced, while, along the lateral sides 39, its magnitude is fully preserved.

In the embodiments shown in Figures 14 to 17, two cavities 47' are also provided, but these are cavities which, over at least a part of their length, have a circular contour, with their axis in the median plane M of the assembly.

In the embodiment shown in Figure 14, the cavities 47' thus have the same cross-section throughout their length.

Alternatively Figures 15 to 17 they widen outwards at at least one of their ends, and in practice at each of the latter, either Figures 15, 16 in that core holes of circular contour of a larger diameter 50 are provided at each of the said ends, or Figure 17 in that frustoconical core holes 50' are involved.

By virtue of cavities staged in this way, some progressivity of the stiffness may be obtained.

In all the cases, inside recess or cavity, it is advantageously possible, according to the invention, to reconcile favourably two apparently contradictory impositions, one relating to the very hardness of the block of elastic material employed, in the case of which it is desirable, naturally, that it should be relatively high to resist as best as possible the stresses to which this block is subjected by the shoulders with which it cooperates, and the other relating to the stiffness of such a block, in the case of which it may, on the contrary, be advantageous that it should be relatively minimal for good filtration of the neutral-point noises or low-speed noises.

Naturally, the present invention is not restricted to the embodiments described and shown, but encompasses any embodiment and/or combination of their various components.

In particular, instead of being cylindrical, the block of elastic material employed according to the invention may also, for example, be in the shape of an hour-glass, thus to have, if required, a stiffness which varies with its circumferential compression.

In addition, and as shown by a full line in Figures 12 and 14, the chamfers 41 which it preferably incorporates may be relatively pronounced, or, as shown by a full line in Figures 1 to 7,11,13 and 15, and as shown diagrammatically in broken lines in Figure 14, they may be relatively unobstrusive.

Furthermore, it is obvious that "elastic material" refers here to a visco-elastic material, in practice rubber or an elastomer.

Claims

1. Torsion absorber device, particularly for a motor vehicle clutch, of the kind incorporating at least two coaxial parts mounted to rotate relative to each other, counter to elastic means inserted circumferentially between them, called for convenience elastic means with circumferential action, and within the limits of an angular clearance determined by the means for meshing with play provided for this purpose between the said coaxial parts, in cooperation with suitable centering means for loading circumferentially the said coaxial parts in the direction of a rest position intermediate between the limits of their said angular clearance, the said centering means incorporating at least one elastic member which, belong to the said elastic means with circumferential action, is placed in the zone of the means for meshing with play of the said coaxial parts and is capable, in the case of the rest position of the latter, of coming to bearwith each of its circumferential ends on shoulders of the said coaxial parts which are oblique relative to each,other, the shoulders which are thus incorporated by at least one of the coaxial parts being themselves oblique relative to each other after the fashion of the sides of a dovetail slot, characterised in that the said elastic member is a simple block of elastic material which is elongated circumferentially, substantially tangentially relative to a circumference of the assembly, and whose circumferential ends, devoid of any coating, are capable of coming directly to bear on the corresponding shoulders of the coaxial parts between which it is inserted circumferentially.

2. Torsion absorber device according to Claim 1, characterised in that each of the circumferential ends of the said elastic member forms, as a hollow, at least one dihedron the ridge of which extends substantially in the median zone of the said end.

3. Torsion absorber device according to Claim 2, characterised in that each of the circumferential ends of the said elastic memberforms, as a hollow, two dihedra with ridges crossed along directions which are substantially at right angles.

4. Torsion absorber device according to Claim 1, characterised in that the said elastic member is elongated circumferentially in the form of a cylinder.

5. Torsion absorber device according to Claim 4, characterised in that the said elastic member has a circular cross-section.

6. Torsion absorber device according to Claim 4, characterised in that the said elastic member has a quadrangular cross-section.

7. Torsion absorber device according to Claim 1, characterised in that at least one of the shoulders which are oblique relative to each other after the fashion of the sides of a dovetail slot is generally oblique relative to a radial direction passing through its median zone.

8. Torsion absorber device according to Claim 1, characterised in that, in the median elastic member has, as a hollow, an undercut.

9. Torsion absorber device according to Claim 8, characterised in that with each of the circumferential ends of the elastic member forming, as a hollow, a dihedron, the corresponding undercut cuts away the ridge of the said dihedron.

10. Torsion absorber device according to either of Claims 8 and 9, characterised in that the undercut is a generally semicylindrical inside recess with generating lines parallel to the axis of the assembly.

11. Torsion absorber device according to Claim 10, characterised in that the undercut has, in crosssection, a circular contour with a centre angle greater than 180 .

12. Torsion absorber device according to Claim 1, characterised in that, between its circumferential ends, the said elastic member has, on at least one of its lateral sides, an inner recess, such that, in its median zone, it has a length with a reduced crosssection.

13. Torsion absorber device according to Claim 12, characterised in that the said inner recess, of reduced depth, which is considerably smaller than one half of the thickness of the elastic member, extends over an appreciable portion of the length of the said elastic member.

14. Torsion absorber device according to either of Claims 12 and 13, characterised in that the elastic member has an inner recess on each of those of its lateral sides, each of which extends substantially tangentially relative to a circumference of the assembly.

15. Torsion absorber device according to Claim 1, characterised in that, with the elastic member having recesses counting from those of its lateral sides each of which extends substantially tangentially relative to a circumference of the assembly, the said recesses are circumferentially alternating relative to each other from one of the said lateral sides to the other.

16. Torsion absorber device according to Claim 15, characterised in that each of the said recesses, each of which is of reduced width, has a depth which is at least equal to one half of the thickness of the elastic member.

17. Torsion absorber device according to either of Claims 15 and 16, characterised in that there is an even number of recesses on one of the lateral sides in question of the elastic member and an odd number on the other of these.

18. Torsion absorber device according to Claim 1, characterised in that, with the said elastic member incorporating, from one to the other of those of its lateral sides which extend substantially transversely relative to the axis of the assembly, at least one cavity which crosses it in parts substantially in parallel to the said axis, the said cavity extends substantially in equal fashion on either side of the median plane of the said elastic member.

19. Torsion absorber device according to Claim 18, characterised in that, with several cavities being provided, each of them extends substantially in equal fashion on either side of the median plane of the elastic member, while being substantially aligned along the said plane.

20. Torsion absorber device according to either of Claims 18 and 19, characterised in that a cavity has, in cross-section, a generally polygonal contour whose sides close to the sides of the elastic member are substantially parallel to these.

21. Torsion absorber device according to Claim 20, characterised in that, with each of the circumferential ends of the elastic member forming, as a hollow, a dihedron, the sides of a cavity which are close to such a circumferential end also form a dihedron together, reflecting the former.

22. Torsion absorber device according to Claims 8 and 18 taken together, characterised in that, corresponding to the undercut present as a hollow in each of the circumferential ends of the elastic member, there is, projecting inwards in the cavity close to such an end, a boss with a contour substantially complementary to that of the said undercut.

23. Torsion absorber device according to any one of Claims 18 to 22, characterised in that, with only two cavities being provided, they are separated from each other by a straight median partition.

24. Torsion absorber device according to either of Claims 18 and 19, characterised in that, with a cavity having a circular contour over at least a part of its length, the cavity widens outwards at at least one of its ends.

25. Torsion absorber device according to Claim 1, characterised in that, at the ends of at least one of the lateral sides of the said elastic member, each of the ridges of the said elastic member is relieved by a chamfer.

26. A torsion absorber device for a clutch, substantially as hereinbefore described with reference to Figures 1 to 17 of the accompanying drawings.