Torsion damping assembly for an automotive clutch plate

This torsional damper is of the type incorporating two coaxial parts mounted to rotate relative to one another within a defined range of relative angular movement, and circumferentially acting means resisting such angular movement, determined by pins disposed around the periphery of the hub disk of the coaxial part, each of said pins being engaged with clearance between two axial shoulders formed for this purpose on the ring presented by the coaxial part around said hub disk. According to the invention the axial shoulders thus associated with said pin are formed by the edges of indentations formed circumferentially in the ring by local deformation thereof. Application suitable for friction clutches for industrial vehicles.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention concerns a torsional damper comprising at least two 
coaxial parts mounted to rotate relative to one another within a defined 
range of relative angular movement and circumferentially acting elastic 
means between said parts resisting such relative angular movement. 
This type of torsional damper is normally incorporated in the design of a 
friction clutch, particularly for automotive vehicles, in which case one 
coaxial part comprises a friction disk designed to rotate with a first 
shaft, in practice a driving shaft and the motor output shaft in the case 
of an automotive vehicle, whereas the other of said coaxial parts is 
carried on a hub designed to rotate with a second shaft, in practice a 
driven shaft, for example the gearbox input shaft in the case of an 
automotive vehicle. 
This type of torsional damper is used to permit regulated transmission of 
rotational torque applied to one of its coaxial parts where the other or 
others are themselves subject to a rotational torque. It is thereby able 
to filter vibrations which may arise at any point in the kinematic system 
in which it is incorporated, extending from the motor to the driven road 
wheels in the case of an automotive vehicle. 
The present invention more particularly concerns the case in which one of 
the coaxial parts incorporates a hub disk whilst a second of said coaxial 
parts incorporates two annular guides, axially disposed one on each side 
of said hub disk, the annular guides being axially linked to one another 
by a ring which extends in the radial direction beyond the periphery of 
the hub disk. 
French patent No. 72 16111 filed May 5, 1972 and published under No. 2 183 
390 and French patent application filed Oct. 14, 1981 under No. 81 19298 
disclosed such an arrangement. French patent application No. 81 19298 has 
been published under No. 2,514,446 on Apr. 15, 1983. Further, commonly 
assigned U.S. application Ser. No. 428,602, filed Sept. 30, 1982, claims 
priority from French patent application No. 81 19298. 
The circumferentially acting elastic means between two coaxial parts of a 
torsional damper normally comprise helical springs disposed substantially 
tangentially relative to a circumference of the damper assembly. The 
ultimate possible range of relative angular movement between these two 
coaxial parts is therefore determined by the turns of at least certain of 
these springs approaching continuity. 
This inevitably results in a certain limitation of the maximum torque which 
can be transmitted from one coaxial part to the other. 
This torque passes through the springs with their turns approaching 
contiguity, and in this case these springs in which crushing stresses are 
combined with the elastic torsional stresses, are generally at the maximum 
of their mechanical capability. 
To avoid such a limitation, and notably, since it is desirable for friction 
clutches to equip heavy industrial vehicles, to enable additional torque 
to pass from one coaxial part constituting such a friction clutch to the 
other after absorption of the maximum possible relative angular movement, 
it has been proposed to equip the hub disk at its periphery with radially 
projecting pins each individually engaged, with clearance, between two 
axial shoulders formed for this purpose in the ring axially linking 
together the two associated annular guides. 
Such an arrangement, whereby the ultimate possible relative angular 
movement between the two coaxial parts is determined by the provision of a 
positive circumferential abutment engagement of the pins against the 
corresponding axially disposed shoulders of the associated ring, is 
disclosed in the abovementioned French patent No. 72 16111 and French 
patent application No. 81 19298. 
In practice, the axial shoulders thus presented by the ring are formed by 
the edge of an indentation formed for this purpose in the ring. 
This results in a weakening of this ring, as well as a certain complication 
in assembling the torsional damper, since this assembly procedure may 
involve an initially non-parallel presentation of the hub disk with 
respect to the ring, before said hub disk is straightened. 
To overcome this problem, it has already been proposed in French patent 
application filed Oct. 14, 1981 under No. 81 19298, to offset radially the 
free edge of the ring, at the expense of increasing the complexity of the 
ring. 
The object of the present invention is to provide an arrangement to obtain 
the required axially disposed shoulders on such a ring in a simple manner, 
the invention also offering further advantages. 
More precisely, the object of the present invention is a torsional damper 
suitable for use in a friction clutch, particularly for automotive 
vehicles, comprising at least two coaxial parts, mounted to rotate 
relative to one another within a defined range of relative angular 
movement, and elastic means comprising one coaxial part incorporating a 
hub disk and a second coaxial part incorporating two annular guides, 
axially disposed one on each side of the hub disk, the annular guides 
being axially linked to one another by a ring which extends in the radial 
direction beyond the periphery of the hub disk, the hub disk being 
equipped at its periphery with radially projecting pins each individually 
engaged, with clearance, between two axial shoulders of the ring, at least 
one of the axial shoulders thus presented by the ring for each of the pins 
of the hub disk being formed by the edge of an indentation formed in the 
circumference of the ring by simple local deformation of the ring. 
Through such an arrangement, the mechanical weakening to which the ring is 
subjected through the formation of the required axial shoulders is 
rendered minimal, since none of the material of the ring is lost. 
In addition, since the axial shoulders thus formed by indentations in the 
ring are themselves radially offset with respect to the continuous part of 
the ring, it is no longer necessary for the free edge of the ring to be 
offset in the radial direction, to obtain an axial engagement of the hub 
disk in the ring. In addition, for the same total radial dimension, the 
hub disk may if required present a higher diameter between the axial 
shoulders of the ring, without altering the ease with which it engages 
axially in the ring. 
Since according to the invention the formation of indentations in the ring 
inevitably involves work hardening of the material constituting the ring, 
this ring advantageously presents increased mechanical strength through 
each of the axial shoulders which it presents to provide a circumferential 
abutment for the pins of the associated hub disk. 
If for attachment to the ring, one of the annular guides has at intervals 
around its periphery radially projecting lugs which can be engaged in 
openings made for this purpose on the corresponding edge of the ring to 
secure the assembly, the axial shoulders of the ring may advantageously be 
circumferentially disposed on each side of these openings. 
U.S. Pat. No. 2,210,074 discloses a torsional damper in which the axial 
shoulders presented by the ring for cooperation with the hub disk are 
formed by means of indentations therein. 
However, unlike the arrangement disclosed by the present invention, the hub 
disk in U.S. Pat. No. 2,210,074 does not incorporate projecting pins for 
engagement between two indentations in the ring, but hollow openings in 
each of which it is engaged on a single such indentation. 
This results in both a weakening of the mechanical strength of the hub 
disk, which is not circularly continuous at its periphery, since it 
incorporates openings, as well as a weakening of the mechanical strength 
of the ring since the deformation of the parts of the ring involved must 
be sufficient to be able to penetrate into the openings in the hub disk. 
In practice, according to U.S. Pat. No. 2,210,074, the deformations in the 
ring corresponding to these indentations, in order to be radially 
sufficiently deep, affect the entire width of the ring. 
In other words, the material of the ring is not axially continuous through 
these deformations, by virtue of the complete absence of material here. 
This is not the case in the torsional damper according to the invention in 
which the local deformations in the ring forming the indentations in the 
ring advantageously affect only part of the width of the ring. 
In U.S. Pat. No. 2,210,074 and as mentioned above, the deformations in the 
ring cooperate with the openings in the hub disk, these openings 
corresponding to the housing of springs disposed between the two coaxial 
parts constituting the torsional damper, which means that the position of 
these deformations on the rings is necessarily related to that of the 
openings on the hub disk. 
This is not the case in the torsional damper according to the invention, in 
which the hub disk is advantageously protected, the ring being able to act 
thereupon if required at a point circumferentially separated from the 
spring housings, and therefor at a point of the hub disk where it is not 
radially weakened by said housings. 
Other objects and advantages will appear from the following description of 
an example of the invention, when considered in connection with the 
accompanying drawings, and the novel features will be particularly pointed 
out in the appended claims.

These figures illustrate an example of an application of the invention to a 
friction clutch for automotive vehicles. 
In the embodiment shown, this friction clutch incorporates two coaxial 
parts A,B, mounted to rotate relative to one another, within a defined 
range of relative angular movement and elastic means resisting such 
relative angular movement. 
In the embodiment shown, coaxial part A incorporates a hub 10 and a 
transverse annular hub disk 11, forming an integral part of said hub 10. 
For example, and as shown, hub disk 11 may be continuous with disk 10, in 
the median zone thereof. 
Also in the embodiment shown, coaxial part B incorporates two transverse 
annular guides 12, 12', axially disposed one on each side of hub disk 11, 
separated therefrom. 
These annular guides, 12, 12' are axially linked to one another by a ring 
14 which extends in the radial direction beyond the periphery of hub disk 
11. 
In the embodiment shown, this ring 14 is continuous with annular guide 12, 
the whole being cut and stamped for example from the same blank, and 
annular guide 12' presents radially disposed lugs 15 at intervals along 
its periphery, through which it is engaged and crimped in openings 16 
provided for this purpose on ring 14, along free edge 17 thereof, 
according for example to arrangements of the type described in French 
patent application filed on Dec. 13, 1977 under No. 77 37511 and published 
under No. 2 411 999. 
For example, and as shown, nine lugs 15, regularly spaced in a circle, may 
thus be provided on the periphery of annular guide 12' of ring 14 
incorporating an equal number of openings 16. 
In the case of a friction clutch for automated vehicles, coaxial part B 
thus constituted incorporates a friction disk 18. 
This friction disk is formed from a disk 20, which in practice is 
circumferentially divided into vanes, and which on its internal periphery, 
is attached by rivets 21 to annular guide 12, on its surface opposite that 
of annular guide 12', while, on its external periphery, it is equipped 
laterally on each side with friction pads 22. 
The elastic means resisting the relative angular movement between coaxial 
parts A,B thus constituted are mounted circumferentially between coaxial 
parts A,B and are formed in the embodiment shown of helical springs 24, 
24', disposed substantially tangentially relative to a circumference of 
the damper assembly. 
In the embodiment shown, there are six such springs 24 which alternate in 
pairs with springs 24', of which there are three, the assembly being 
disposed at regular intervals in a circle. 
Some of springs 24 are disposed in apertures 25 of hub disk 11, the others 
being disposed in housings 26 made for this purpose in annular guides 12, 
12', said housing 26 in the embodiment shown being stamped alternately in 
opposite axial directions in said annular guides 12, 12', and 
corresponding thereto. 
In practice, in the embodiment shown, springs 24 are engaged without 
circumferential clearance in apertures 25 of hub disk 11 and housings 26 
of annular guides 12, 12'. 
According to an arrangement similar to the foregoing, some of springs 24' 
are disposed in slots 25' of hub disk 11 the rest being disposed in 
housings 26' of annular guides 12, 12'. 
However, although the springs 24' are engaged without circumferential 
clearance in housings 26' of annular guides 12, 12', a circumferential 
clearance is provided, for the idle configuration of the damper assembly, 
between their circumferential ends and the corresponding circumferential 
ends of apertures 25' of hub disk 11. 
For the circumferential direction corresponding to the direction of 
increasing torque, which is also the normal direction of rotation of said 
assembly, as shown by the arrow F in FIG. 1, this circumferential 
clearance has the value JT. 
For the opposite circumferential direction, corresponding to the direction 
of decreasing torque, it has the value JR. In the embodiment shown, 
circumferential clearances JT and JR have the same value, but this is not 
necessarily the case in other embodiments. 
In addition, in the embodiment shown, springs 24, 24' are duplicated, each 
of these springs being in practice formed from two coaxial springs of the 
same length but of different diameters, respectively 24.sub.1, 24.sub.2, 
and 24'.sub.1, and 24'.sub.2, disposed one inside the other. 
In the embodiment shown, the friction clutch is completed by friction means 
acting axially between the two coaxial parts A, B which constitute the 
clutch. 
In this embodiment, friction ring 28 is applied to hub disk 11 on the side 
for example of annular guide 12, carried by support ring 29 secured 
against rotation by axial lugs 30 on this annular guide 12. 
An axially acting elastic ring 36 of the type for example sold under the 
trade name ONDUFLEX, is interposed axially between support ring 29 and 
annular guide 12, to maintain friction ring 28 in permanent contact with 
hub disk 11. 
These arrangements are well known per se, and as they do not constitute 
part of the present invention, will not be described in further detail 
here. 
Also in a manner known per se, to delimit the possible relative angular 
movement between coaxial parts A, B, hub disk 11 is equipped at its 
periphery with radially projecting pins 32 each individually engaged 
between two axial shoulders 33T, 33R formed for this purpose in ring 14, 
with, for the idle configuration of the damper assembly, a circumferential 
clearance J'T in one direction corresponding to increasing torque of the 
damper assembly, and J'R in the opposite direction corresponding to 
decreasing torque of said damper assembly. 
In the embodiment shown, circumferential clearances J'T, J'R are identical, 
but as shown, this is not necessarily the case. 
In all embodiments, these clearances J'T, J'R are respectively greater than 
previously mentioned clearances JT, JR. 
In the embodiments shown, pins 32 are circumferentially offset with respect 
to apertures 25, 25'. 
According to the invention, at least one of axial shoulders 33T, 33R in 
ring 14 is transversely in the shape of a channel, this indentation having 
a uniform cross section along its circumferential extension, through this 
fact being open at each of its circumferential ends. 
In the preferred embodiment shown, each of indentations 34T, 34R in ring 14 
is offset circumferentially with respect to openings 16 in said ring, and, 
in practice, the two indentations 34T, 34R in ring 14 for each of pins 32 
of hub disk 11 extend respectively on each side of an opening 16 therein. 
However, in the embodiment shown, there is only a reduced number of pins 32 
as compared with 16, this number being for example six, as shown. 
As will be noted, indentations 34T, 34R in ring 14 are very easily formed 
by simple local deformation thereof, the circumferential ends of said 
indentations being sheared without removal of material. 
The integrity of ring 14 is thus advantageously practically retained. 
This advantage is enhanced in practice as the local deformation of ring 14 
required to form an indentation 34T, 34R therein advantageously affects 
only part of the axial width of said ring. 
It will be appreciated that the action of the punching tool used operates 
in the radial direction, from the exterior towards the center. 
As will also be noted, in its continuous section, ring 14 retains a simple 
configuration which in cross section is almost rectilinear, without any 
radial displacement of its free edge 17. 
As will finally be noted, the indentations according to the invention which 
form axial shoulders 33T, 33R advantageously enable the torsional damper 
to be assembled with hub disk 11 in line with ring 14, facilitating said 
assembly operation and, hub disk 11 once positioned in ring 14 is 
peripherally enveloped in its entirety by said ring, including in the 
plane perpendicular to its pins 32, providing excellent protection 
thereof. 
In service, coaxial part B constitutes in practice a driving part, its 
friction disk 18 being intended to be clamped in the axial direction by 
its friction pads 22 between two plates constrained to rotate with a 
driving shaft, in this case the output shaft of the motor of an automotive 
vehicle, and, coaxial part A constitutes a driven part, its hub 10 being 
intended to be linked in rotation to a driven shaft generally by a channel 
arrangement, for example the input shaft to a gearbox in the case of an 
automotive vehicle. 
If torque is then applied to coaxial part B in a direction of arrow F in 
FIG. 1, this coaxial part B drives coaxial part A. 
However, initially, the only parts acting are springs 24. 
After absorbing the preliminary assembly stress normally presented by said 
springs in their housings, these springs 24 yield elastically, so that a 
relative angular movement develops between coaxial part B and coaxial part 
A in the direction of rotation of the damper assembly, as shown in the 
diagram in FIG. 6, on which the relative angular movement D is shown as 
the abscissa and the corresponding transmitted torque C as the ordinate. 
For a value D1 of angular movement D, corresponding to an absorption of 
circumferential clearance JT, springs 24' in turn take effect, as before, 
after absorption of their preliminary stress, and add their effect to that 
of springs 24, which remain in compression. Finally, for a value D2 of 
relative angular movement D corresponding to an absorption of 
circumferential clearance J'T, pins 32 of hub disk 11 come into contact 
with the corresponding axial shoulders 33T of ring 14, through the effect 
of the circumferential abutment between them. 
There is then positive drive to coaxial part A through coaxial part B 
without intervention of springs 24, 24' which nevertheless remain in 
compression. 
Because of this, an additional torque may then be transmitted from coaxial 
part B to coaxial part A. 
In the direction of decreasing torque, the process is reversed. 
Such a procedure is known per se, and will not therefore be described in 
further detail here. 
As will be appreciated, to simplify the diagram in FIG. 6, the hysteresis 
effects due to friction ring 28 have not been taken into account. 
As is known, for the same value of relative angular movement D these 
hysteresis effects lead to a difference in the value of the torque 
transmitted for the increasing direction of torque compared to its value 
for the decreasing direction of torque. 
In the embodiment shown in FIG. 7, each of indentations 34T, 34R in ring 14 
for each of pins 32 of hub disk 11 is in the shape of a quarter ellipsoid 
obtained by sectioning on two mutually or thorgonal planes of symmetry, 
open at only one of its circumferential ends, where it forms the 
corresponding axial shoulder 33T, 33R, while being closed at the other 
end. 
These indentations 33T, 33R therefore decrease in cross section from their 
open circumferential end to their closed circumferential end. 
The punching tool used is advantageously simplified, a single shearing 
stroke being required for each indentation. 
In addition, in this embodiment, the median circumferential lines of each 
of the two indentations 33T, 33R in ring 14 for each of pins 32 of hub 
disk 11, shown by the sectional lines in FIG. 7, are each rectilinear and 
substantially in line with each other, as shown on FIG. 7. 
In all cases, there is advantageously axial continuity of material for the 
ring through each of the indentations, except for the circumferential ends 
thereof. 
As will be appreciated, the present invention is not limited to the 
embodiments described and shown, but encompasses all variants of execution 
and/or combination of the various elements thereof. 
In addition, the field of application of the invention is not limited only 
to those torsional dampers incorporating only two coaxial parts mounted to 
rotate relative to one another, but also extends to the case in which move 
coaxial parts, mounted to rotate in pairs, are provided within such a 
torsional damper.