Torsion damper for a motor vehicle disc-type clutch

A torsion damper comprises two coaxial parts, one of which comprises a damper plate and a hub, coaxial with each other and having respective complementary sets of teeth. A resilient member in the form of a shock absorbing ring is provided in the same coaxial part of the damper and is coupled in rotation to the damper plate. The shock absorbing ring comprises at least one substantially rigid first member, on which the set of complementary teeth is formed, together with at least one resiliently deformable second member for coupling in rotation with the damper plate.

FIELD OF THE INVENTION 
The present invention relates to a torsion damping device, in particular 
for a friction clutch of the disc type for a motor vehicle, the torsion 
damping device being a torsion damper comprising two coaxial parts which 
are mounted for relative rotational movement with respect to each other 
through a limited angle and against the action of first resilient means, 
in which one of the two said coaxial parts comprises a damper plate and a 
hub, mounted coaxially with each other and for relative rotation with 
respect to each other, against the action of second resilient means and 
over a sector of angular displacement which is defined by complementary 
sets of teeth formed on the damper plate and on the hub, with the 
complementary sets of teeth defining a circumferential clearance between 
them. 
BACKGROUND OF THE INVENTION 
A torsion damper of the above kind is described in the specification of 
U.S. Pat. No. 4,613,029, which proposes to provide third resilient means 
interposed circumferentially between the damper plate and the hub. These 
third resilient means are so designed as to enable the teeth of the damper 
plate to come into positive circumferential abutment with the teeth of the 
hub, while at the same time producing a noise-suppressing or 
sound-deadening braking effect. In this way the damper plate teeth are 
enabled to come gently into engagement with the hub teeth, with noises due 
to impact between the two sets of teeth thus being avoided. In one 
embodiment, a ring of resilient material is engaged around one of the 
teeth of one of the sets of teeth, in a groove on that tooth, and is 
arranged to be compressed by the neighbouring teeth of the other set. 
Such an arrangement is effective when the equipment is new, but is liable 
to deteriorate over a period of time. In addition, the teeth which receive 
these damping rings (or the damping ring if there is only one) are 
weakened, and the torque which they can transmit is thus reduced. 
In order to overcome the above drawbacks, it has been proposed in the 
unpublished French patent application No. 90 07866, filed on 22 Jun. 1990 
in the name of the same Applicant as French patent application No. 90 
14872 on which the present application is based, to make the third 
resilient means in the form of a ring of resilient material which extends 
parallel to the damper plate and which is provided with a set of teeth 
complementary to those on the hub. These complementary teeth mesh with the 
hub teeth, defining between them a further circumferential clearance which 
is smaller than the circumferential clearance that is provided between the 
damper plate teeth and the hub teeth. The set of teeth on the hub is 
extended axially so that it can mesh with those of the damper plate and 
the said ring (the latter being referred to as a shock absorbing ring 
herein). 
The shock absorbing ring is arranged to rotate with the damper plate, and 
is of resiliently deformable material at its inner periphery. In certain 
applications, with a view to simplifying manufacture, and also with a view 
to obtaining satisfactory durability, it may be desirable that this shock 
absorbing ring is made rigid at its inner periphery. 
DISCUSSION OF THE INVENTION 
An object of the present invention is to satisfy the above criteria without 
weakening either the teeth on the damper plate or those on the hub, and to 
provide an arrangement which will remain effective over an extended period 
of time. 
In accordance with the invention, a torsion damper having a shock absorbing 
ring, of the general type described above is characterised in that the 
shock absorbing ring comprises at least one substantially rigid first 
member on which the said set of teeth, complementary to those of the hub, 
is formed, together with at least one resiliently deformable second member 
for rotational coupling with the damper plate. 
The invention enables the manufacture of the shock absorbing ring to be 
simplified, because the complementary set of teeth is formed in the rigid 
first member and the deformations of the deformable second member are 
properly controlled over a period of time. In addition, the teeth on the 
hub and the damper plate are neither modified nor weakened. 
In one embodiment of the invention, advantage is taken in a cost-effective 
and simple manner of the bearing which is interposed radially between one 
of the guide rings of the torsion damper and the hub, by forming the said 
complementary teeth in the hub itself. Preferably, a ring of resiliently 
deformable material is then engaged on each of the spigots which are 
normally provided on the said bearing for coupling it in rotation with the 
damper plate, with each of these rings penetrating into an opening which 
is provided for this purpose in the damper plate. 
In another embodiment of the invention, in which the said bearing forms a 
spacer between the guide ring and the damper plate, advantage is taken of 
this arrangement by using the space which is thereby made available to 
interpose a ring, in that space, between the bearing and the damper plate. 
This ring carries the said complementary set of teeth at its inner 
periphery, while at its outer periphery it carries rings of resilient 
material, each of which is engaged on a corresponding one of the spigots 
formed on the bearing. 
The outer periphery of this ring can of course be of resilient material and 
be coupled in rotation to the spigots through a coupling of the tenon and 
mortice type. 
Further features and advantages of the invention will appear more clearly 
from a detailed reading of the description which follows, of various 
preferred embodiments of the invention, given by way of example only and 
with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
FIGS. 1 and 2 show one application of a torsion damping device for a 
disc-type friction clutch for a motor vehicle, identical to that which is 
disclosed in the specification of U.S. Pat. No. 4,613,029, to which 
reference is invited for the details of the design and construction of 
this torsion damper. It will however be mentioned here that this torsion 
damping device comprises two coaxial parts, namely a first part 10, 11, 
15, 16 and a second part 12, 18. These coaxial parts are mounted for 
limited relative rotational movement against the action of first resilient 
means 19 in the form of coil springs. 
The second coaxial part 12, 18 itself comprises a damper plate 18, lying 
generally in a radial plane, and a hub 12 which is coaxial with the damper 
plate 18. These two components 12 and 18 are mounted for rotational 
movement with relation to each other against the action of second 
resilient means 24, again in the form of coil springs. The springs 24 act 
during the relative displacement of the damper plate 18 and hub 12 through 
an angular sector which is defined by complementary sets of teeth 25 and 
26, formed respectively on the damper plate 18 and hub 12 (in a projected 
flange of the latter) and having the appropriate circumferential clearance 
J which defines the above mentioned angular sector of relative 
displacement. 
The first coaxial part comprises friction pads 10, which are mounted on an 
annular clutch plate 11 on either side of the latter. The friction pads 10 
carried by the clutch plate 11 are adapted to be gripped between the 
pressure plate and reaction plate of the clutch (not shown), which are 
secured to an engine crankshaft for rotation with the latter. The hub 12, 
surrounded by the damper plate 18, is adapted to be engaged, by means of 
splines 13, on a driven shaft, not shown, which in this example is the 
input shaft of the gearbox of the motor vehicle, so that the hub 12 is 
rotatable with the gearbox input shaft. 
The clutch plate 11 is secured by means of rivets 14 to a guide ring 15, 
the latter being connected to another guide ring 16 by means of spacers, 
which in this example are in the form of pins or short bars 17. For this 
purpose the spacers 17 pass through the damper plate 18 via openings 21 
which are formed in the latter. The guide rings 15 and 16 are mounted for 
rotation around the hub 12, without any set of teeth or similar elements 
being interposed. The damper plate 18 which is thus arranged axially 
between the two guide rings 15 and 16. It will be appreciated that the 
sets of teeth 25 and 26 limit in the circumferential direction the extent 
of possible rotation of the damper plate 18 with respect to the hub 12. 
The first resilient means 19 consist of a plurality of circumferentially 
acting helical springs mounted in windows 22 formed in the damper plate 
18, and also in further windows 23 which are formed, facing the windows 
22, in the guide rings 15 and 16. The stiffness in compression of the 
resilient means 24 is smaller than that of the springs 19. The springs 24 
are again circumferentially acting resilient springs, and are interposed 
between the damper plate 18 and the hub 12 through end thrust inserts 27. 
Each end thrust insert 27 has a rear face of dihedral profile, and on its 
opposite side it has a spigot 28 for centring engagement with the 
associated spring 24. The purpose of the springs 24 is essentially to 
filter out noise, for example gearbox noise or dead centre noise, when the 
torque which is transmitted through the torsion damping device is either 
zero or very small. The springs 24 are mounted in slots which are formed 
partly in the inner periphery of the damper plate 18 and partly in the 
outer periphery of the hub 12, in zones in which these slots take the 
place of the teeth 25 and 26. The springs 19, in combination with friction 
means 20, are interposed between the two coaxial parts of the torsion 
damper, and their function is essentially to damp out those vibrations 
which arise between the engine shaft and the driven shaft while the 
vehicle is in motion. 
A further set of resilient means, here referred to as third resilient 
means, are also provided, for the purpose of suppressing or reducing the 
undesirable consequences of violent and noisy impact between the teeth of 
the set 25 and those of the set 26. In FIG. 2, these third resilient means 
act circumferentially, and comprise two blocks 29 in the form of rings of 
a resilient material. Each block 29 is engaged around one tooth 30 of the 
set of teeth 25 of the damper plate, being fitted in a groove 31 formed on 
this tooth. The blocks 29 are adapted so as to be compressed by the two 
adjacent, corresponding teeth 32 of the set of teeth 26 on the hub 12. In 
the part of the description that follows, various forms of these 
circumferentially acting resilient means and embodying the principles of 
the present invention, together with elements that are common or similar 
to the present invntion and to the prior art, will be designated by the 
same reference numerals. 
Referring now to FIG. 3, in this embodiment the third resilient means are 
indicated by the reference numeral 40. They consist of an assembly that 
constitutes a shock absorbing ring 40 which comprises at least one 
substantially rigid first member 42 and at least one second member 58 
which is resiliently deformable. In the present example, the first member 
42 has the general shape of a ring. More precisely, the member 42 
comprises a central annular portion 44 which extends in a radial and axial 
plane between the damper plate 18 and the guide ring 16. The radially 
inner peripheral edge 46 of the central portion 44 is formed with a set of 
teeth 48 of a rigid material, having a profile which is complementary to 
the set of teeth 26 on the hub 12, and such that in the rest position 
there is a circumferential clearance J1, which is smaller than the 
circumferential clearance J that exists in the rest position between the 
set of teeth 25 of the damper plate 18 and the set of teeth 26 of the hub 
12. 
The set of teeth 26 on the hub 12 (FIG. 3) is extended axially to the 
right, so that it can mesh simultaneously with the set of teeth 25 on the 
damper plate 18 and with a third set of teeth 48 which are formed on the 
first ring member 42 of the shock absorbing ring 40. The teeth of the set 
48 are trapezoidal in shape (as are those in the other two sets of teeth 
25 and 26). The teeth 48 are received with a clearance in complementary 
recesses defined between the hub teeth 26. 
The annular portion 44 of the first member 42 is also extended radially 
inwardly, in a portion which constitutes a conical bearing 50 that is in 
contact with a corresponding conical surface 52 formed on the hub 12. The 
conical bearing 50 serves for centring the guide ring 16 on the hub 12, 
and has an axially oriented flange for cooperation with the guide ring 16, 
which itself has an axial flange. 
In the vicinity of its radially outer edge, the portion 44 has a series of 
spigots 54, which extend axially towards the damper plate 18 and away from 
the axial flange of the bearing 50. The spigots 54 are spaced apart 
circumferentially, and the number of these spigots will depend on the 
particular application to which the assembly is to be put. Each spigot 54 
is received in a corresponding hole or opening 56 which is formed in the 
damper plate 18, and is formed integrally with the first member or ring 
42. The spigots 54 couple the shock absorbing ring 40 to the damper plate 
18 by means of a resilient rotary coupling interposed between them. This 
coupling consists of a series of resiliently deformable second members 58 
which are mounted in the holes 56. Each of these second members 58 is in 
the form of a ring of a resiliently deformable material such as rubber, 
and has an outer profile complementary to that of the hole 56 and an inner 
profile complementary to the outer profile of the spigot 54. 
Referring now to FIG. 5, each spigot 54 has an oblong profile, with 
circumferential edges which are rounded in the form of semi-circles 
connected together through two straight parallel sides. Thus each spigot 
54 is of generally pad-like shape. In a modification (not shown), each of 
these oblong spigots may have an oval or elliptical profile; but in all 
cases its oblong shape ameliorates the torque transmission. 
As will have been understood from the foregoing, the subassembly 40 that 
comprises the substantially rigid first member 42 and the resiliently 
deformable member 58 constitutes a shock absorbing ring which is 
operatively connected between the damper plate 18 and the hub 12. The 
member 42 is, in this example, preferably of a plastics material having a 
low coefficient of friction, for example a polyamide. It acts as a spacing 
bearing which is coupled in rotation to the damper plate 18 with the rings 
58 interposed. It will be realised that advantage can be taken of this 
bearing to form the set of teeth 48 integrally with it. This bearing 
accordingly has an additional function, and it is stiffened by the set of 
teeth 48. It will also be noticed that the central axial portion 44 of the 
first member 42 acts as a spacer between the damper plate 18 and the guide 
ring 16, and that advantage is taken of the space which is available at 
the level of the inner periphery of the damper plate 18, in order to 
accommodate the teeth 48. 
FIG. 4 shows the clearance J1 which exists between the teeth 26 and the 
teeth 48 and which, as already mentioned, is smaller than the clearance J 
between the teeth 25 and the teeth 26. None of the teeth 25 or 26 is 
notched, and they are able to come into abutment against each other due to 
the fact that the shock absorbing ring 40 extends in a direction parallel 
to the damper plate 18. 
The torsion damper includes, in addition to the foregoing, an axially 
acting resilient ring 60 and a friction ring 62, which are interposed 
successively between the guide ring 15 and the damper plate 18 (as can be 
seen in FIG. 3). The friction ring 62, which is preferably made of a 
material having a low coefficient of friction such as a polyamide, is 
coupled to the guide ring 15 for rotation with the latter, by means of a 
plurality of spigots 64 which are received in complementary holes 66 
formed in the guide ring 15. The resilient ring 60 consists in this 
example of a Belleville ring. It bears on the rings 15 and 62 so as to 
bias the ring 62 axially against the damper plate 18, and so as also to 
cause the central axial portion 44 of the shock absorbing ring 40 to be 
gripped between the damper plate 18 and the other guide ring 16. 
A further ring 68 is arranged radially inwardly of the Belleville ring 60, 
between the radial face 70 of the projecting flange of the hub 12 and the 
guide ring 15. This ring 68 is generally similar to the friction ring 62, 
and is provided with spigots 74 which are received axially in 
complementary openings 76 formed in the guide ring 15. The rings 15 and 68 
are thus coupled together in rotation by mating cooperation. 
A further axially acting resilient ring 78, again in the form of a 
Belleville ring, is however also provided between the guide ring 15 and 
the ring 68. The Belleville ring 78 is less stiff than the Belleville ring 
60. This resilient ring 78 is coupled to the ring 68 by mating engagement, 
for which purpose it has appropriate slots which cooperate with the 
spigots 74 of the ring 68. During operation, because the springs 19 are 
stiffer than the springs 24, the damper plate 18 is first caused to be 
displaced in a rotational sense with respect to the hub 12, against the 
resistive force exerted by the springs 24 and by the friction means 68, 
78, 40, until the teeth in the set 26 come into contact with those of the 
set 48 of the first member 42. This provides a sound-deadening braking 
effect which is brought about by the rings 58. The effect is continued 
until the teeth 25 are in full engagement with the teeth 26. During this 
operation, the damper plate 18 and the guide rings 15 and 16 together 
form, effectively, a single component. 
A second stage of the operation is that in which the damper plate 18 is now 
rotatable fully with the hub 12, and in this stage the springs 19 become 
compressed and the friction means 60, 62, 44 are in operation. The 
movement continues until the turns of the springs 19 come together, or 
until the spacers 17 (FIG. 1) come into engagement with the openings 21. 
Reference is now made to FIGS. 6 and 7. This embodiment differs from that 
shown in FIGS. 3 to 5 in that a variable-hysteresis supplementary ring 80 
is disposed axially between the damper plate 18 and the central axial 
portion 44 of the first member 42 of the shock absorbing ring 40. The 
variable-hysteresis ring 80 includes a set of internal radial teeth 82, 
and is abutted resiliently against the damper plate 18 by means of an 
axially acting resilient ring 84 (which is here again of the Belleville 
ring type), bearing on the central axial portion 44 of the member 42. The 
Belleville ring 84 exerts a smaller force than the ring 60, and the 
spigots 54 are brought into cooperation with the friction ring 62 in such 
a way that the Belleville ring 84 is not compressed excessively. 
As can be seen in FIG. 7, the set of teeth 82 is complementary to the sets 
of teeth 25 and 26, being arranged to define a circumferential clearance 
which is smaller than that existing between the teeth 25 and the teeth 26. 
The teeth 82 are so dimensioned as not to foul the teeth 48 of the shock 
absorbing ring 40. The variable-hysteresis ring 80 thus acts like a 
drawer, and also exerts a braking effect on the mutual engaging action of 
the teeth 25 with the teeth 26. 
A further ring 86 is disposed between the resilient ring 84 and the 
variable-hysteresis ring 80, so as to spread the application of the axial 
load of the ring 84 on the ring 80. All the other components of the 
torsion damping device shown in FIGS. 6 and 7 are identical with those of 
the device seen in FIGS. 3 to 5, and are indicated by the same reference 
numerals. In operation, the variable-hysteresis ring 80 is caused to rub 
against the damper plate 18, with the clearance between the teeth 82 and 
25 being taken up. 
Reference is now made to FIGS. 8 to 10, showing a third embodiment. In 
these Figures, those elements that are identical or equivalent to those of 
the device shown in FIGS. 3 to 5 are designated by the same reference 
numerals but with 100 added. As shown in FIG. 8, the spigots 154 of the 
rigid first member 142 are received directly in the holes 156 formed in 
the damper plate 118. 
The inner radial edge of the central portion 144 of the substantially rigid 
first member 142 of the shock absorbing ring 140 does not have teeth 
complementary to the teeth 126 of the hub 112 and the teeth 125 of the 
damper plate 118. A complementary set of teeth 148 is however formed in a 
rigid third member 90, which is again in the form of a ring and which 
extends in a radial plane, being disposed axially between the damper plate 
118 and the central portion 114 of the first member 142. 
In the vicinity of its radially outer periphery, the rigid third member 90 
has a series of axial holes 92, through which the spigots 154 pass. A ring 
158, of a resiliently deformable material such as rubber, is arranged 
around each spigot 154 and within the corresponding hole 92. The various 
elements 90, 142 and 158 together perform the same damping or shock 
absorbing function as the assembly constituted by the members 42 and 58 in 
FIGS. 1 to 3, with the rigid member 90 being resiliently coupled in 
rotation to the damper plate 118 through the spigots 154. To this end, and 
as is best seen in FIG. 9, the circumferential clearance J that exists 
between the teeth 148 and the teeth 126 is smaller than the 
circumferential clearance J that exists between the teeth 125 and the 
teeth 126. This embodiment operates, in all essentials, in just the same 
way as that already described with reference to FIGS. 1 to 3. All of the 
other components seen in FIGS. 8 to 10, whether or not they are indicated 
by reference numerals, are the same as those in FIGS. 3 to 5. It will be 
appreciated that the ring 140 and the damper plate 118 are substantially 
unchanged. 
Referring now to FIGS. 10 to 12 showing a fourth embodiment of the torsion 
damper, in these Figures all those components that are identical or 
similar to those in the arrangement seen in FIGS. 3 and 4 are here 
indicated by the same reference numerals, but with 200 added. In FIGS. 10 
to 12, the design of the rigid member 242 of the assembly that constitutes 
the shock absorbing ring 40 is identical to the first member 142 described 
and shown in FIGS. 8 to 10. 
However, in this case the substantially rigid first member of the shock 
absorbing ring 40 consists of two parts, viz. a rigid third member 242 and 
a fourth member 96. The fourth member 96 is itself made in two parts, 
namely a rigid inner part having the third set of teeth, 248, formed 
around its radially inner profile, and a resiliently deformable outer 
part. The teeth 248 are complementary to the teeth 226 of the hub 212 and 
to the teeth 225 of the damper plate 218, and operate in the same way as 
the teeth 48 or 148 described in relation to the previous embodiments. The 
fourth member 96 is in the form of a ring, and extends radially and 
axially between the damper plate 218 and the central annular portion 244 
of the rigid third member 242. It is joined resiliently in rotation to the 
damper plate 218 through the cooperation of slots 98, which are formed in 
its outer radial edge in a resiliently deformable material, with 
complementary profiles 100 on each of the spigots 254, with these latter 
being received directly in holes 256 of the damper plate 218. The profiles 
100 and slots 98 thus constitute the resilient second member of the shock 
absorbing ring 40. 
It will be appreciated that these complementary profiles 100 define a 
shoulder for contact with the damper plate 218, in such a way that the 
ring 96 runs no risk of being excessively stressed. Such a shoulder may of 
course also be provided in the other embodiments. The embodiment shown in 
FIGS. 11 and 12 again includes a variable-hysteresis ring, 180, having a 
set of teeth 182, which operates in exactly the same way as the 
variable-hysteresis ring 80 in FIGS. 6 and 7. 
As will be evident from the foregoing and from the drawings, the first 
member comprising the elements 44, 90 and 96, which carries the teeth 
complementary to those formed on the hub 12, is provided with slots in the 
vicinity of the springs 24 so as to avoid any interference with the 
latter. This is for example visible in FIGS. 4 and 9. The same is so in 
respect of the variable histeresis rings, as can be seen in FIGS. 12 and 
7. 
The present invention is of course not limited to the various embodiments 
described above. In particular, the assembly of elements constituting the 
resilient shock absorbing ring may form part of a pre-damper which is 
arranged between the damper plate 18 and one of the guide rings in the 
manner described and shown in the specification of U.S. Pat. No. 
4,883,156. In that arrangement, the set of teeth formed on the hub flange 
is extended in such a way as to mesh with the internal radial teeth of the 
shock absorbing ring. Preferably, the latter is then coupled in rotation 
with the axial spacers of the pre-damper, by mating cooperation of slots, 
formed in the shock absorbing ring, with the spacers which then nest in 
these slots. 
In another modification, the circumferentially acting resilient means 
consist of blocks of resilient material. The circumferential clearances J 
and J1 may be symmetrical in the rest position of the assembly, by 
contrast with the situation in the embodiments described above in which 
they are asymmetric. 
The spigots 54, 154 or 254, spaced apart circumferentially at regular 
intervals, may be bifurcated. In that case, and as seen in FIG. 13, the 
resilient rings 58 of FIG. 5 are replaced with H-shaped blocks 258 of a 
resilient material. Each spigot element 354 then penetrates into one 
branch of the H. The shock absorbing effect is obtained by means of the 
vertical portion of the blocks 258, with the horizontal portion of the 
H-shaped cross section of the block merely separating the spigot elements 
254 from the block 258. 
Finally, the bearing 142 or 242 may, instead of being conical, be of any 
other suitable shape, and a radial clearance may be provided between it 
and the hub.