FR3069602A1 - SHOCK ABSORBER WITH ELASTIC LIMIT SWITCH - Google Patents

Abstract

The invention relates to a torsion damper for a torque transmission device comprising: - a first element (1) and a second element (2) movable in rotation relative to each other about an axis of rotation X ; and - an elastic damping member (6, 7) for transmitting a torque and damping the acyclisms between the first element (1) and the second element (2), the torsion damper being characterized in that it comprises a end-of-stroke device comprising an elastic blade (11) arranged to be spaced from an abutment surface (29) when the angular displacement between the first element (1) and the second element (2) is less than one deflection threshold (33) and biased and elastically deformed to generate an elastic restoring force acting against the angular deflection between the first element (1) and the second element (2) when said angular displacement is greater than said displacement threshold (33).

Description

SHOCK ABSORBER WITH ELASTIC LIMIT SWITCH

Technical area

The invention relates to the field of torque transmission devices of the torsional damper type intended to equip motor vehicle transmissions.

Technological background

Explosion engines do not generate constant torque and have acyclisms caused by successive explosions in their cylinders. These acyclisms generate vibrations which are capable of being transmitted to the gearbox and thus causing particularly undesirable shocks, noise and noise. In order to reduce the undesirable effects of vibrations and improve the driving comfort of motor vehicles, it is known to equip motor vehicle transmissions with torsional dampers. Such torsional dampers are fitted in particular to double damping flywheels (DVAs), clutch friction, or locking clutches, also called "lock-up" clutches.

The document FR3008152 discloses a double damping flywheel comprising a primary flywheel and a secondary flywheel which can rotate relative to each other about an axis of rotation X. The double damping flywheel comprises means damping elastics which are formed by several flexible arms mounted on one of the flywheels and each carrying a cam surface cooperating with an associated roller mounted to rotate on the other flywheel.

During an angular movement between the primary flywheel and the secondary flywheel, the roller moves along the cam surface and, in doing so, elastically deforms the flexible arm. This elastic deformation makes it possible to absorb vibrations and irregularities in rotation between the primary and secondary flywheels while ensuring the transmission of torque.

Free stops can be provided in order to limit the angular displacement of the primary flywheel relative to the secondary flywheel, for example in the presence of significant torque passing between the primary flywheel and the secondary flywheel. Such stops are obtained by pressing rigid surfaces each carried by one of the flywheels and cooperating with each other. Such stops tend to generate shocks, vibrations and noises which can be harmful to the operation of the device and to the feeling of the driver.

summary

The object of the invention is in particular to provide a simple, effective and economical solution to this problem. In particular, the object of the invention is to produce an end-of-travel stop ensuring good protection of the damping means while limiting the shocks and noise pollution generated by said end-of-travel stop.

For this, the invention provides a torsional damper for a torque transmission device comprising:

- a first element and a second element movable in rotation relative to one another about an axis of rotation X; and

- an elastic damping member arranged between the first element and the second element to transmit a torque and dampen acyclisms between the first element and the second element, the torsion damper being characterized in that it comprises an end device stroke capable of opposing the angular movement between the first element and the second element according to at least a first direction of relative rotation, when the angular movement between the first element and the second element is greater than a first movement threshold from a rest position in which no torque passes between the first element and the second element, the limit switch device comprising:

a first abutment surface carried by the second element,

- An elastic blade carried by the first element, said elastic blade comprising a first contact portion and a first support portion separated circumferentially from one another by an elastically deformable central portion of the elastic blade, the first portion d 'support being arranged to bear against a first support surface carried by the first element, and the first contact portion being arranged in circumferential relation to the first abutment surface in such a way that the first portion contact either:

o remote from the first abutment surface when the angular clearance between the first element and the second element in the first direction of rotation is less than the first deflection threshold, and o urged and displaced by the first abutment surface when said angular deflection is greater than the first clearance threshold, the elastic blade being pressed between the first abutment surface and the first bearing surface by producing an elastic restoring force acting against the angular clearance between the first element and the second element according to the first direction of rotation.

Thanks to these characteristics, the end-of-travel device limits noise and impact when the stop means come into contact. In particular, the end of travel stop is made in an elastic manner. This end of travel stop is thus progressive using the flexing of the elastic blade.

In addition, such an end-of-travel device makes it possible to modify the stiffness of the torsion damper at the end of the travel, that is to say when the angular travel between the first element and the second element reaches the travel threshold. .

According to other advantageous embodiments, such a shock absorber can have one or more of the following characteristics:

According to one embodiment, the elastic blade has a first end and a second end respectively forming the first contact portion and the first support portion. The blade can thus flex between its ends. If desired, the blade can flex as a whole.

According to one embodiment, the end of travel device further comprises a guide device arranged to circumferentially guide the movement of the first contact portion of the elastic blade when said first contact portion is urged by the first abutment surface. Such a guide device makes it possible to orient the deformation of the elastic blade, that is to say to guide the deformation of the blade in a radial direction towards the outside. Thus, the elastic blade works in flexion in order to generate the elastic restoring force opposing the angular movement between the first element and the second element.

According to one embodiment, the guide device is arranged to guide the first contact portion circumferentially in translation.

According to one embodiment, the guide device is arranged to guide the first contact portion in displacement without deformation of said first contact portion. In other words, the guide device is arranged so that the first contact portion retains a substantially identical shape when it is at a distance from the first abutment surface and when it is urged and moved by the first abutment surface. Such a guide device makes it possible to concentrate the deformation stresses of the elastic blade outside the first contact portion.

According to one embodiment, the guide device comprises a first guide surface and a second guide surface carried by the first element, said first and second guide surfaces being arranged radially on either side of the first contact portion of the elastic blade. Such guide surfaces allow effective guidance of the deformation of the elastic blade.

According to one embodiment, one or each guide surface is in contact with the first contact portion when the first abutment surface is at a distance from the first contact portion. According to another embodiment, a clearance is present between one or each guide surface and the first contact portion when the first abutment surface is at a distance from the first contact portion.

According to one embodiment, the first guide surface is arranged radially outside the first contact portion of the elastic blade and the second guide surface is arranged radially inside the first contact portion of the blade elastic.

According to one embodiment, the first guide surface is arranged circumferentially between the second guide surface and the elastically deformable central portion of the elastic blade.

According to one embodiment, a clearance separates the second guide surface from the contact portion of the blade, before the contact portion of the blade comes to bear with the first abutment surface.

According to one embodiment, the first guide surface is in abutment against the contact portion of the blade, before the contact portion of the blade comes into abutment with the first abutment surface.

Such an arrangement of the guide surfaces allows a better distribution of the deformation stresses of the elastic blade.

According to one embodiment, the first and second guide surfaces are offset circumferentially along the first contact portion.

Such guide surfaces also make it possible to generate friction between the elastic blade and the first element in order to allow better dissipation of the energy linked to impacts between the first element and the second element.

According to one embodiment, the first element comprises a cavity facing the second element, the elastic blade being housed in said cavity and projecting from the cavity in the direction of the second element, the cavity having radial dimensions in a plane orthogonal to the axis of rotation X greater than the radial dimensions of the central portion of the elastic blade in said plane orthogonal to the axis of rotation X so as to allow the deformation of the central portion of the elastic blade in said cavity. Such a cavity allows simple and rapid mounting of the elastic blade on the first element.

According to one embodiment, a first circumferential end of the cavity forms the first bearing surface.

According to one embodiment, the elastic blade is prestressed circumferentially in the cavity. This makes it possible to make up for any deviations in the dimensioning of the cavity and of the blade linked to the manufacturing tolerances.

According to one embodiment, the end-of-travel device further comprises a rigid stop comprising a first stop surface carried by the first element and a second stop surface carried by the second element, said first and second surfaces stop being opposite circumferential and arranged for:

- on the one hand, be distant from each other during a relative rotation between the first element and the second element according to the first direction of rotation less than a first maximum relative travel between the first element and the second element , said first maximum relative travel being greater than the first travel threshold, and,

- on the other hand, to be in abutment against one another in order to limit the relative angular movement between the first element and the second element according to the first direction of rotation when said relative angular movement reaches said first maximum relative movement.

According to one embodiment, the end-of-travel device further comprises an axial retaining member arranged to axially hold the elastic blade on the first element.

According to one embodiment, the axial retaining member is carried by the first element so that the blade is interposed axially between the first element and said axial retaining member. This axial retaining member can take many forms. In one embodiment, and the axial retaining member is a retaining plate axially covering an axial face of the blade opposite the cavity.

According to one embodiment, the end-of-travel device also comprises a second bearing surface carried by the first element and a second abutment surface carried by the second element, the elastic blade comprising a second bearing portion and a second contact portion separated from each other by the elastic central portion of the elastic blade, the second support portion being arranged to bear against the second support surface, and the second contact portion being arranged in with respect to the circumference of the second abutment surface in such a way that the second contact portion is:

- at a distance from the second abutment surface when the angular movement between the first element and the second element in a second direction of rotation opposite to the first direction of rotation is less than a second movement threshold from the rest position, and

- stressed and moved by the second abutment surface when said angular clearance is greater than said second deflection threshold, the elastic blade being pressed between the second abutment surface and the second bearing surface and by producing a restoring force acting on the 'against the angular movement between the first element and the second element in the second direction of rotation. Thus, the same elastic blade can participate in the end of travel stop regardless of the direction of relative rotation between the first element and the second element.

According to one embodiment, the guide device is arranged to guide the second contact portion circumferentially in displacement.

According to one embodiment, the guide device is arranged to guide the second contact portion circumferentially in translation.

According to one embodiment, the guide device is arranged to guide the second contact portion in displacement without deformation of said second contact portion. In other words, the guide device is arranged so that the second contact portion retains a substantially identical shape when it is at a distance from the second abutment surface and when it is urged and moved by the second abutment surface. Such a guide device allows the stresses of deformation of the elastic blade to be concentrated outside the second contact portion. In addition, such a guide device makes it possible to maintain the second contact portion in position when the first contact portion is biased and moved by the first abutment surface. Thus, the guide device can advantageously concentrate the stresses in the blade outside the first and second contact portions, that is to say in the central portion of the blade. In other words, the deformations of the elastic strip are concentrated circumferentially in the central portion of the elastic strip, between the two contact portions. The resistance of the elastic blade is thus reinforced.

According to one embodiment, the guide device comprises a third guide surface and a fourth guide surface, the third guide surface being disposed radially outside the second contact portion of the elastic blade and the fourth surface guide being disposed radially inside the second contact portion of the elastic blade, the third guide surface being arranged circumferentially between the elastically deformable central portion of the elastic blade and the fourth guide surface. Thus, such a guide device allows a good distribution of the stresses on the elastic blade regardless of the direction of stress of said elastic blade. More particularly, the deformation of the elastic blade is concentrated circumferentially between on the one hand the pair the first and second guide surfaces and on the other hand the pair of third and fourth guide surfaces.

According to one embodiment, the elastic blade is arranged so that the elastically deformable central portion of the elastic blade is able to flex alternately in the first direction of relative rotation and in the second direction of relative rotation of the damper, respectively when the angular displacement between the first element and the second element according to the first direction of rotation is greater than the first deflection threshold and when the angular displacement between the first element and the second element according to the second direction of rotation is greater than the second deflection threshold .

According to one embodiment, a radially external face of the cavity forms a radial support zone of the elastic blade against which the blade is supported when the angular movement between the first element and the second element exceeds the first or the second threshold of travel, preferably when said angular travel between the first element and the second element exceeds a radial contact threshold travel greater than the first angular travel threshold.

According to one embodiment, the radius of curvature of the radially external face of the cavity is greater than the radius of curvature of the elastic blade so as to allow better deformation of the blade in the cavity on either side of the zone radial support of the blade on the radially outer face of the cavity.

Advantageously, such a support zone is centered circumferentially on the radially external face of the cavity, allowing a balanced deformation of the blade on either side of the support zone.

According to one embodiment, the elastic blade has a first end forming the first contact portion. According to one embodiment, a circumferential edge of the first end opposite the elastically deformable central portion of the elastic blade is opposite the first abutment surface. In other words, the first contact portion has a circumferential edge forming a surface for cooperation with the first abutment surface. According to one embodiment, said circumferential edge of the first contact portion comprises a circumferential shoulder, a lower portion of said edge being arranged to cooperate with the first bearing surface and an upper portion of said circumferential edge forming the surface for cooperation with the first stop surface.

According to one embodiment, the elastic blade has a second end forming the second contact portion. According to one embodiment, a circumferential edge of the second end opposite the elastically deformable central portion of the elastic blade is opposite the second abutment surface. In other words, the second contact portion has a circumferential edge forming a surface for cooperation with the second abutment surface. According to one embodiment, said circumferential edge of the second contact portion comprises a circumferential shoulder, a lower portion of said edge being arranged to cooperate with the second bearing surface and an upper portion of said circumferential edge forming the surface for cooperation with the second stop surface.

According to one embodiment, the first end and / or the second end extend circumferentially.

According to one embodiment, the first end forms both the first contact portion and the second support portion, and the second end forms both the second contact portion and the first support portion. Thus, such is simple to perform and advantageously allows the stop at the elastic end of travel in the two directions of relative rotation between the first element and the second element.

According to one embodiment, a second end of the cavity forms the second bearing surface.

Such a cavity is simple to produce and thus makes it possible both to accommodate the elastic blade and to block the circumferential movement of the elastic blade in order to allow its elastic deformation.

According to one embodiment, the rigid stop also comprises a third stop surface carried by the second element and a fourth stop surface carried by the first element, said third and fourth stop surfaces being facing each other. circumferential screws and arranged for:

- on the one hand, being distant from each other during a relative rotation between the first element and the second element according to the second direction of rotation less than a second maximum relative travel between the first element and the second element , said second maximum relative travel being greater than the second travel threshold, and,

- on the other hand, to be in abutment against one another in order to limit the relative angular movement between the first element and the second element according to the second direction of relative rotation when said angular movement reaches said second maximum relative movement.

According to one embodiment, the elastic blade, in particular its central portion, is arched in a plane perpendicular to the axis of rotation so as to flex with radial and circumferential components. According to one embodiment, the elastic blade is arched so that its top is arranged radially on the outside

According to one embodiment, the elastic blade is arched with a concavity facing the axis of rotation X. Such a blade is simple to produce and to integrate into the torsion damper.

The elastic blade is arranged in such a plane to flex radially, the end of travel stop thus generating no additional space and therefore making it possible to produce the end of travel stop with space, in particular axial space, reduced. Indeed, the deflection of the elastic blade and of the flexible arm takes place orthogonally to the axis X. The arm and at least part of the elastic blade occupy the same axial space so that the axial space requirement is limited.

Within the meaning of the invention, the flexing of the arm and of the elastic blade in the same axial space means that the elastic blade and the arm have at least one axial covering plane.

Thus, advantageously, the elastic blade does not generate additional axial dimensions compared to the axial dimensions of the elastic arm.

Thus, the geometry of the blade promotes its bending in a plane perpendicular to the axis of rotation.

According to one embodiment, the blade develops circumferentially around the axis of rotation X,

According to one embodiment, the radius of curvature of the blade is centered on a point located radially inside the blade.

According to one embodiment, the elastic blade is not a split circular cylindrical pin.

According to one embodiment, the damping member comprises a flexible arm carried by one of the first and the second element and cooperating with a support element arranged between the flexible arm and the other from the first element and the second element for cooperating with said flexible arm, the support element and the flexible arm being arranged such that, during an angular movement between the first element and the second element, the support element exerts a bending force on the flexible arm producing a reaction force capable of transmitting a torque and absorbing the rotational acyclisms between the first element and the second element, the flexible arm comprising a cam surface and the bearing element comprising a follower cam arranged to move on the cam surface when torque is transmitted by the damper and the first member and the second member rotate one relative to the other, the elastic blade of the limit switch extending circumferentially on either side of the cam follower.

According to one embodiment, the radial support zone and the axis of rotation of the cam follower are aligned with the axis of rotation of the torsion damper. In other words, according to one embodiment, the support zone is radially opposite the cam follower.

According to one embodiment, the first element carries a first lug projecting axially towards the second element and carrying the second guide surface.

According to one embodiment, the first element carries a second lug projecting axially towards the second element and carrying the fourth guide surface.

According to one embodiment, the first lug develops circumferentially along the cavity.

According to one embodiment, the second lug develops circumferentially along the cavity.

According to one embodiment, the first lug and the second lug are arranged circumferentially on either side of the support element. According to one embodiment, the first lug and the second lug are symmetrical with respect to the axis of rotation X.

According to one embodiment, the elastic blade develops circumferentially on either side of the support element.

According to one embodiment, the elastic blade develops circumferentially outside the support element.

According to one embodiment, the first element comprises a circular peripheral skirt. According to one embodiment, the first guide surface is formed by a radially internal face of the peripheral skirt. According to one embodiment, the third guide surface is formed by the radially internal face of the peripheral skirt.

According to one embodiment, the first stop surface is formed by a first projecting portion of the peripheral skirt. According to one embodiment, the third stop surface is formed by a second projecting portion of the peripheral skirt.

According to one embodiment, the support element is a cam follower comprising a roller capable of rolling on a cam surface carried by the flexible arm.

According to one embodiment, the cam follower is carried by the first element and the roller of the cam follower is arranged radially between the flexible arm and the central portion of the elastic blade.

According to one embodiment, the cam follower is arranged radially outside the flexible arm.

According to one embodiment, the elastic blade is arranged radially outside the cam follower.

According to one embodiment, the elastically deformable central portion of the elastic blade is arranged radially outside the cam follower. Thus the cam follower retains the flexible arm vis-à-vis centrifugal forces and the elastic blade, due to its spacing from the axis of rotation, absorbs less force. In addition, such a blade can thus occupy a large circumferential space in the torsion damper without requiring significant modification of the torsion damper and, in particular, without imposing additional bulk.

According to one embodiment, in the absence of stress on the elastic blade by either of the first or second abutment surface, a radial clearance separates the elastically deformable central portion of the elastic blade from the radially face external facing the cavity.

According to one embodiment, the elastically deformable central portion of the elastic blade has a radius of curvature greater than or equal to a radius of curvature of the roller of the cam follower.

According to one embodiment, the radius of curvature of the cavity is greater than or equal to the radius of curvature of the support element.

According to one embodiment, during its deformation radially outwards, the central portion of the blade can bear radially on the radially internal face of the skirt. This support can guide and limit, if necessary, the deformation of the central portion of the blade.

In another embodiment, the blade is arranged so that the central portion is spaced from the skirt for any angular movement greater than the first movement threshold. This allows in particular to use advantageously a large part of the capacities of the blade.

According to one embodiment, the end of travel device comprises two elastic blades.

According to one embodiment, the two elastic blades are symmetrical with respect to the axis of rotation X.

According to one embodiment, the elastic blade is a first elastic blade, the end of travel device further comprising a second elastic blade carried by the first element, the end of travel device also comprising a third abutment surface carried by the second element and a third bearing surface carried by the first element, a first contact portion of the second elastic blade being arranged facing the circumference of the third abutment surface and a first bearing portion of the second elastically deformable blade being arranged in circumferential relation to the third bearing surface, the second elastic blade being arranged in such a way that the first contact portion of the second elastic blade is at a distance from the third surface of stop when the angular movement between the first element and the second element in the first direction of rotation is less than or equal to the first deflection threshold and urged by the third abutment surface to exert a circumferential compression force on the second elastic blade between the third abutment surface and the third bearing surface so that the second elastic blade produce an elastic restoring force acting against the angular movement between the first element and the second element in the first direction of rotation when the angular movement is greater than said first movement threshold.

According to one embodiment, the end-of-stroke device further comprises a fourth abutment surface carried by the second element and a fourth bearing surface carried by the first element, a second contact portion of the second elastic blade being arranged in circumferential relation to the fourth abutment surface and a second bearing portion of the second elastic blade being arranged in circumferential relation to the fourth bearing surface, the second elastic blade being arranged in in such a way that the second contact portion of the second elastic blade is at a distance from the fourth abutment surface when the angular clearance between the first element and the second element according to the second direction of rotation is less than or equal to the second clearance threshold and urged by the fourth abutment surface to exert a circumferential compression force on the d second elastic blade between the fourth abutment surface and the fourth bearing surface so that the second elastic blade produces an elastic restoring force acting against the angular movement between the first element and the second element in the second direction of rotation when the angular travel is greater than said second travel threshold.

According to one embodiment, when the limit switch is actuated and the elastic blade bends, even when the first and second stop surfaces are in contact, the elastic blade is able to pivot the first and second elements in the direction the damper rest position.

In other words, the shock is not blocked.

According to one embodiment, the force exerted by the first abutment surface and / or the second abutment surface is circumferential.

According to one embodiment, the elastic blade is compressed when it is stressed by the first abutment surface.

According to one embodiment, the elastic blade deforms at least in part by buckling.

According to one embodiment, the force is oriented in the direction in which the first contact portion of the elastic blade extends.

According to a second aspect, the invention relates to a torque transmission device, in particular for a motor vehicle transmission train, the torque transmission device comprising a torsion damper according to the first aspect of the invention intended to transmit a torque from the engine to the gearbox.

According to one embodiment, a flexible arm is a deformable arm.

According to one embodiment, a flexible arm consists of an arm flexibly attached to the second element.

According to one embodiment, the blade has no fixing portion.

Brief description of the figures

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely by way of illustration and without limitation. , with reference to the accompanying drawings.

- Figure 1 is a front view of a torsional damper with arms on which the secondary flywheel is partially illustrated;

- Figure 2 is a sectional view of the torsional damper arm of Figure 1 according to section A-A illustrated in Figure 1;

- Figure 3 is a detail view from above of the torsion damper of Figure 1 illustrating the elastic blade housed in the cavity of the primary flywheel;

- Figure 4 is a sectional view of a detail of Figure 3 according to section l-l illustrated in Figure 3;

- Figure 5 is a sectional view of a detail of Figure 3 according to section II-II illustrated in Figure 3;

- Figure 6 is a perspective view of the torsion damper of Figure 1 in which the secondary flywheel is only partially illustrated in a position of maximum relative travel between the primary flywheel and the secondary flywheel;

- Figure 7 is a schematic representation of an elastic blade of Figure 1 illustrating the deformation of said elastic blade in two opposite relative directions of rotation of the primary flywheel and the secondary flywheel;

- Figure 8 is a graph illustrating a curve representative of the torque transmitted as a function of the relative angular movement between the primary flywheel and the secondary flywheel;

- Figure 9 is a detail view illustrating an alternative embodiment of the axial retaining member illustrated in Figure 5;

- Figure 10 shows another embodiment of the blade;

- Figure 11 shows another embodiment of the blade;

Detailed description of embodiments

In the description and the claims, the terms external and internal as well as the axial and radial orientations will be used to designate, according to the definitions given in the description, elements of the torsion damper. By convention, the radial orientation is directed orthogonally to the axis X of rotation of the torsion damper determining the axial orientation and, from the inside to the outside away from said axis, the circumferential orientation is directed orthogonally to the axis of the torsion damper and orthogonally to the radial direction. The terms external and internal are used to define the relative position of an element with respect to another, with reference to the axis X of rotation of the torsional damper, an element close to the axis is thus qualified as internal as opposed to an external element located radially on the periphery.

The following description is made with reference to the figures in the context of a torsional damper of the double flywheel type. This description is not limiting and the invention is applicable by analogy to any other type of torsion damper.

A double damping flywheel as illustrated in FIGS. 1 to 7 comprises a primary flywheel 1, hereinafter primary flywheel 1, and a secondary flywheel 2, hereinafter secondary flywheel 2, which are arranged in the transmission chain of a motor vehicle, respectively on the engine side and on the gearbox side. The primary flywheel 1 constitutes an input element of the double damping flywheel and is intended to be fixed to the end of a driving shaft, such as the crankshaft of an engine. The secondary flywheel 2 constitutes an output element of the double damping flywheel and forms a reaction plate of a clutch coupling to a driven shaft, such as the input shaft of a gearbox.

The primary flywheel 1 and the secondary flywheel 2 have a respectively internal and external hub. The primary flywheel 1 and the secondary flywheel 2 are mounted so that they can rotate about a common axis of rotation X by means of a bearing radially interposed between the internal hub and the external hub.

The primary flywheel 1 comprises a primary plate 3 developing radially outward from the internal hub. A peripheral portion of the primary plate 3 carries a skirt 4 projecting axially in the direction of the secondary flywheel 2. The secondary flywheel 2 has a secondary plate 5 developing radially outward from the external hub.

The primary flywheel 1 and the secondary flywheel 2 are coupled in rotation by a damping means. This damping means comprises two flexible and elastic arms 6 each cooperating with a respective cam follower 7.

In the embodiments illustrated in FIGS. 1 to 7, the arms 6 are produced independently, each arm 6 comprising a mounting portion 8 and a flexible portion 9 which are specific to it. The two arms 6 as illustrated in FIG. 6 are symmetrical with respect to the axis of rotation X. This symmetry of the arms 6 makes it possible to advantageously make the two arms 6 identically. Thus, the characteristics described for one of the arms 6 apply by analogy to the other arm 6. Similarly, the description made below for a cam follower 7 applies by analogy to the two cam followers .

Each arm 6 is mounted on and integral in rotation with the secondary flywheel 2 around the axis X. The arms 6 are mounted on the secondary flywheel 2 by any suitable means, for example by riveting the mounting portion 8 on the secondary plate 5. A radially outer face of the flexible portion 9 of each arm 6 has a cam surface 10 cooperating with one of the cam followers 7. Each arm 6 is elastically deformable. The arms 6 are for example made of a spring material such as a spring steel, for example by a fine cutting process on a sheet 12 mm thick.

Each cam follower 7 comprises a roller mounted on the primary flywheel 1 movable in rotation about an axis of rotation parallel to the axis X. Each roller is mounted in rotation on a rod carried by the primary plate 3 via of a landing.

The torsion damper illustrated in FIG. 1 is in a rest position in which no torque transits between the primary flywheel 1 and the secondary flywheel 2. Torque transmission between the primary flywheel 1 and the secondary flywheel 2 is accompanied a relative travel between the primary flywheel 1 and the secondary flywheel 2. During this relative travel, the cam follower 7 moves along the cam surface 10. The flexible portion 9 is able to flex elastically when the follower cam 7 moves along the cam surface 10 from the rest position of the torsion damper. The flexing of the flexible portion 9 generates a reaction force tending to return the torsional damper to the rest position.

The damping means is thus able to transmit a driving torque from the primary flywheel 1 to the secondary flywheel 2 (direct direction) and a resistant torque from the secondary flywheel 2 to the primary flywheel 1 (retro direction). The arms 6 develop an elastic return torque tending to return the primary flywheel 1 and the secondary flywheel 2 to a relative angular position of rest. The document

FR3008152 describes the general operation of such a torsion damper with flexible and elastic arms.

In an embodiment not shown, the mounting of the arms 6 and of the cam followers 7 is reversed so that the element carrying the arms 6 is the primary flywheel 1 and the element carrying the cam followers 7 is the secondary flywheel 2.

In an embodiment not shown, the arms 6 are joined by a common mounting portion 8, for example in the form of an annular mounting portion 8 from which develop the flexible portions 9 of each of the arms 6. Furthermore , the arms 6 can be produced using a plurality of lamellae superposed axially by clinching.

In order to avoid degradation of the damping means in the event of transmission of an excess torque, for example resulting from limiting conditions of use of the torsional damper or from a malfunction of the powertrain, the damper of torsion comprises a limit switch device making it possible to limit the angular clearance between the primary flywheel 1 and the secondary flywheel 2. This limit switch device allows progressive abutment between the primary flywheel 1 and the secondary flywheel 2 during a relative rotation between the primary flywheel 1 and the secondary flywheel 2 exceeding a predetermined travel threshold. Such a limit switch device is, for example, active during the extreme stress phases of the torsion damper, which no longer ensures filtration of acyclic movements and makes it possible to attenuate the shocks and noise nuisances which may occur during travel. angle between the primary flywheel 1 and the secondary flywheel 2.

The end-of-travel device comprises two elastic blades 11 arranged on the primary flywheel 1 and two abutment surfaces 12 arranged on the secondary flywheel 2. The two elastic blades 11 are symmetrical with respect to the axis X so that only one blade elastic is illustrated in Figure 1 and the description below made for said elastic blade 11 applies by analogy to the other elastic blade 11. Similarly, the two abutment surfaces 12 are symmetrical with respect to the axis X, the description below of an abutment surface 12 applying by analogy to the other abutment surface.

The blade 11 develops axially in a direction parallel to the axis of rotation X. The blade 11 develops circumferentially along a curve whose concavity is turned towards the axis of rotation X. The blade 11 has a central portion 13 having a radius of curvature greater than the radius of the roller of the cam follower 7. For example, the radius of curvature of the central portion 13 of the blade 11 is close to the radius of curvature of the skirt 4. The blade 11 has a first circumferential end 14 and a second circumferential end 15 situated respectively on either side circumferentially of the central portion 13.

This blade 11 is made of a material allowing its elastic deformation, for example in a material identical to the material used to manufacture the arms 6 such as a spring steel.

The blade 11 is mounted on the primary flywheel 1 radially outside the cam follower 7. This positioning of the blade 11 radially outside the cam follower 7 provides greater circumferential space for the blade 11 without harming the amplitude of the angular movement between the primary flywheel 1 and the secondary flywheel 2, thus making it possible to produce a circumferentially elongated blade 11 and making it possible to store more energy during a deformation of said blade 11. In addition, the blade 11 develops circumferentially on either side of the cam follower 7. The blade 11 is arranged on the primary flywheel so that, for any relative angular position between the primary flywheel 1 and the secondary flywheel 2, a radial clearance is present between the cam follower 7 and said blade 11.

The primary flywheel 1 comprises a cavity 16 formed in the thickness of the primary plate 3, for example by machining such as by milling in the cast iron of the primary plate 3. This cavity 16 has a shape similar to the shape of the blade 11, c 'is to say a concave shape whose concavity is turned towards the cam follower 7. In a similar manner to the blade 11, this cavity 16 develops circumferentially on either side and radially outside the follower of cam 7. The radial dimensions of the cavity 16 are slightly greater than the radial dimensions of the blade 11 so as to allow the elastic deformation of the blade 11 in the cavity 16 as explained below.

The primary flywheel 1 also comprises two lugs 17 each projecting from the primary plate 3 in the direction of the secondary flywheel 2. These lugs 17 develop circumferentially on either side of the cam follower 7 along the cavity 16. In addition , the skirt 4 has two projecting portions 18 radially inwardly and developing circumferentially along the cavity 16. A circumferential end opposite to the cam follower 7 of each protruding portion 18 has a stop surface 19 developing radially from so as to be contiguous with the radially internal surface of the skirt from which said projecting portion 18 projects radially inwards.

The cavity 16 develops circumferentially beyond the projecting portions 18 and the lugs 17. In other words, a circumferentially central portion of the cavity 16 is extended axially in the direction of the secondary flywheel 2 by the lugs 17 and the projecting portions 18 and the ends circumferentials of said cavity 16 are not extended axially by said projecting portions 18 and the pins 17. An angle of 1 to 5 ° around the axis X for example separates the stop surface 19 from the corresponding circumferential end of the cavity 16.

A radially outer face of each lug 17 has a boss 20 projecting radially outward. Similarly, the protruding portions 18 each have a boss 21 projecting radially inward. These bosses 20, 21 each form a guide surface to guide the deformation of the blade 11 as explained below. As illustrated in FIG. 1, each boss 20 is inserted circumferentially between the boss 21 of the projecting portion 18 opposite said boss 20 and a corresponding circumferential end of the cavity 16. In other words, said boss 20 is closer from the circumferential end of the cavity 16 as a corresponding boss 21.

The blade 11 is housed in the cavity 16. The circumferential dimensions of the blade 11 are greater than or equal to the circumferential dimensions of the cavity 16. Thus, the circumferential ends 14, 15 of the blade 11 are, in the rest position of the torsion damper as illustrated in FIG. 1, in contact or in abutment against a corresponding circumferential end of the cavity 16.

The blade 11 projects axially from the cavity 16 in the direction of the secondary flywheel 2. Thus, a first portion of the blade 11 housed in the cavity 16 develops axially in the axial size of the primary plate 3 and a second portion of the blade 11 projects axially from the cavity 16 and develops axially beyond the cavity 16. The second portion of the blade 11 develops axially in the axial size of the damping means. Typically, the second portion of the blade 11 does not protrude axially in the direction of the secondary flywheel 2 beyond the arms 6 or the cam followers. In other words, the blade 11 is arranged to flex radially in a plane perpendicular to the 'axis of rotation X common with the bending plane of the arms 6. The blade 11 has for example an axial thickness of the order of 7 to 8 mm. The blade 11 can thus advantageously be positioned in the axial size of the primary flywheel 1 and in the axial size imposed by the presence of the damping means, that is to say of the arms 6 and / or of the cam followers 7, and therefore does not require additional axial space. Thus, the torsion damper does not have a large axial size, this axial size is not increased by the presence of the blade 11.

In the embodiment illustrated in FIGS. 1 to 6, the blade 11 is retained axially in the cavity 16 by an axial retention member formed by a retaining plate 22 interposed axially between the blade 11 and the secondary flywheel

2. As illustrated in FIGS. 2 or 5, an upper surface 23 of the skirt 4 facing the secondary flywheel 2 has a counterbore 24. The blade 11 is flush with the said counterbore 24. The retaining plate 22 is develops radially from the skirt 4 to the lugs 17. A radially external end of the retaining plate 22 is housed in the counterbore 24. A radially internal end of the retaining plate 22 axially interposed between the lugs 17 and the secondary flywheel 2 is fixed on the lugs 17. The fixing of the retaining plate 22 on the lugs 17 can be carried out in different ways, for example by riveting, screwing or the like. In addition, the retaining plate 22 includes a circular recess making it possible to accommodate the roller of the cam follower 7.

Figures 3 to 5 illustrate in detail the arrangement of the blade 11 in the cavity 16 in the rest position of the torsion damper. Only the first circumferential end 14 of the blade arranged in a first end 25 of the cavity 16 is illustrated in these figures 3 to 5, the corresponding description of these figures 3 to 5 applying by analogy to the arrangement of the blade 11 in the cavity 16 at the second circumferential end 15 of the blade 11 in a second circumferential end 26 of the cavity 16.

As illustrated in FIG. 3, the first circumferential end 14 of the blade 11 defines a contact portion cooperating with the guide surfaces formed by the bosses 20 and 21 respectively of the lug 17 and of the projecting portion 18 opposite -radial screw of said first circumferential end 15. In other words, the first circumferential end 15 of the blade 11 is in radially inward contact with the boss 20 of said lug 17 and in radially outward contact with the boss 21 of said projecting portion 18. Furthermore, as illustrated in FIG. 4, a circumferential face 27 of said first circumferential end 14 is in contact, with or without support, with a first circumferential face 28 formed by the first circumferential end 25 of the cavity 16. Similarly, a circumferential face of the second circumferential end 15 is in contact, with ec or without support, with a second circumferential face 36 (see FIG. 7) formed by the second circumferential end 26 of the cavity 16.

As illustrated in FIG. 4, the first circumferential end 14 may include a circumferential shoulder. Such a shoulder generates a circumferential offset between the first portion of the blade 11, that is to say housed in the cavity 16, and the second portion of the blade 11, that is to say outside the cavity 16 Such a shoulder can for example be linked to construction constraints.

As illustrated in FIG. 1, the secondary flywheel 2 has two abutment surfaces 12, a first abutment surface 29 of said two abutment surfaces 12 and a second abutment surface 30 of said two abutment surfaces 12. These abutment surfaces are by example formed by pins projecting from the secondary plate 5 in the direction of the primary plate 3. Each abutment surface 29, 30 is facing circumferentially on the one hand from one of the circumferential ends 14, 15 of the blade 11 and, on the other hand, a corresponding stop surface 19. More particularly, each abutment surface 29, 30 faces a circumferential face of a face of the second portion of the blade 11, that is to say situated outside the cavity 16, formed by an edge of the circumferential end 14, 15 opposite the central portion 13. Thus, the first abutment surface 29 is facing circumferentially on the one hand from the first circumferential end 14 of the blade 11 and, on the other hand, from a first surface stop 31 formed by the projecting portion 18 cooperating with said first circumferential end 14 of the blade

11. Similarly, the second abutment surface 30 is facing circumferential on the one hand from the second circumferential end 15 of the blade 11 and on the other hand from a second stop surface formed by the portion protruding 18 cooperating with said second circumferential end 15 of the blade.

The relative angular movement between the primary flywheel 1 and the secondary flywheel 2 in a first direction of rotation 32, during a torque transmission between the primary flywheel 1 and the secondary flywheel 2, brings the first abutment surface 29 closer to the first circumferential end 14 of the blade 11. When said relative angular movement reaches a first predetermined threshold movement 33 (see FIG. 8), the first abutment surface 29 comes into contact with the first circumferential end 14 of the blade 11.

When the relative angular movement between the primary flywheel 1 and the secondary flywheel 2 according to this first direction of rotation 32 exceeds said first threshold travel 33, the first abutment surface 29 bears circumferentially on the first circumferential end 14 of the blade 11. However, the circumferential face of the second circumferential end 15 of the blade 11 is in circumferential contact with the second circumferential face 36 formed by the second circumferential end 26 of the cavity 16. Consequently, the support of the first abutment surface 29 on the first circumferential end 14 of the blade 11 results in the application of a circumferential compression force on the blade 11, said blade 11 being compressed between the first abutment surface 29 and the second circumferential face 36 of the cavity 16. Under the effect of this circumferential compressive force, the blade 11 ten d to flex elastically, deforming radially outward. This elastic deformation of the blade 11 generates a restoring force which opposes the relative rotation between the primary flywheel 1 and the secondary flywheel 2.

As illustrated in FIG. 6, when the relative angular clearance between the primary flywheel 1 and the secondary flywheel 2 according to the first direction of rotation 32 reaches a maximum clearance 34 (see FIG. 8) greater than the first threshold clearance 33, the first surface of stop 29 comes into contact with the first stop surface 31. This contact between the first stop surface 29 and first stop surface 31 fulfills the role of frank end-of-travel stop between the primary flywheel 1 and the secondary flywheel 2 Thus, the elastic deformation of the blade 11 constitutes an elastic end-of-travel stop prior to the frank stop between the primary flywheel 1 and the secondary flywheel 2.

During its deformation under the effect of the support of the first abutment surface 29, the blade 11 is guided in deformation by the bosses 20, 21 cooperating with the first circumferential end 14 of the blade 11. In fact, the bosses 20, 21 situated on either side radially of the first circumferential end 14 of the blade 11 guide said first circumferential end 14 of the blade 11 in circumferential translation when the first abutment surface 29 is pressed. In addition, the circumferential offset between the boss 20 of the lug 17 and the boss 21 of the projecting portion 18 allows better guiding in translation of the first circumferential end 14 of the blade 11 and a deformation of the central portion 13 of the blade 11 radially outwards. This guiding of the blade 11 advantageously allows a better distribution of the stresses undergone by the blade 11 during its deformation. In addition, the support of the blade 11 on the bosses 20, 21 makes it possible to adapt the stiffness of the blade 11, and therefore the stiffness of the torsion damper, to the needs of the system. Furthermore, the guidance of the first circumferential end 14 by the bosses 20, 21 generates friction allowing better dissipation of energy.

During its deformation radially outwards, the central portion 13 of the blade 11 can bear radially on the radially internal face of the skirt 4. This support can guide and limit, if necessary, the deformation of the central portion 13 of the blade on either side of said support. Preferably, this support is radially aligned with the axis of rotation of the cam follower 7.

In another embodiment, the blade is arranged so that the central portion 13 of the blade 11 is spaced from the skirt 4 for any angular movement greater than the first movement threshold 33. This allows in particular to have a larger portion of the blade 11 which deforms.

The operation of the elastic end-of-travel stop produced above in the context of a relative angular movement between the primary flywheel 1 and the secondary flywheel 2 according to the first direction of rotation 32 applies in a similar manner to an angular movement relative between the primary flywheel 1 and the secondary flywheel 2 in a second direction of rotation 35 opposite to the first direction of rotation 32. Thus, the above description of the cooperation between the secondary flywheel 2 and the blade 11 in the context of a first abutment surface 29 of the secondary flywheel 2 cooperating with the first circumferential end 14 of the blade 11 applies by analogy to the cooperation between the second abutment surface 30 of the secondary flywheel 2 and the second circumferential end 15 of the blade 11 according to the second direction of rotation 35. Thus, FIG. 7 schematically illustrates the deformation of the blade 11 according to whether the blade undergoes a compressive force sion between the first abutment surface 29 and the second circumferential face 36 of the cavity 16 or between the second abutment surface 30 and the first circumferential face 28 of the cavity 16. Thus, as illustrated in this figure 7, the blade 11 operates similarly in the two directions of rotation 32, 35 relative between the primary flywheel 1 and the secondary flywheel 2. However, a second threshold travel between the primary flywheel 1 and the secondary flywheel 2 according to the second direction of rotation 35 can be with an angular value identical or different to the angular movement corresponding to the first threshold movement 33. In this FIG. 7, the blade 11 is shown in solid lines when it is not subjected to the compressive force exerted by the abutment surfaces 12 and in dotted lines when it is subjected to said compressive force and is therefore in a bent position.

FIG. 8 illustrates with reference to curve 37 the torque transmitted by the end-of-travel device of the torsion damper as a function of the angular clearance between the primary flywheel 1 and the secondary flywheel 2. It can be seen that the curve has two slopes 38 and 39.

The slope 37 illustrates the initial phase of the end of travel phase, when the angular travel between the primary flywheel 1 and the secondary flywheel 2 is greater than the first travel threshold 33, after contact between the abutment surfaces 29 and the first circumferential ends 14 of the blades 11. At this stage, the first circumferential ends 14 of the blades 11 are not firmly held radially by the two guide surfaces formed by the bosses 20, 21. The bosses 20 forming the second and fourth guide surfaces cooperating respectively with the first circumferential end 14 and the second circumferential end 15 can at this stage be slightly distant from said first circumferential end 14 and the second circumferential end 15 respectively forming the first and second contact portions of the blade 11.

The slope 39, steeper than the slope 38 illustrates the role played by the guide device, that is to say by the bosses 20, 21 forming the guide surfaces of the blade 11. The guide device allows obtain greater stiffness when each circumferential end 14, 15 of blade 11 is held radially firmly by the guide device.

In the case where the blade 11 is not mounted sufficiently prestressed in the cavity 16 and the circumferential ends 14, 15 of the blade 11 are not held firmly radially in said cavity 16, the first phase of the limit switch device with the first slope 38 allows the second end-of-travel phase to be progressively reached with the second stiffness slope 39.

The angular movement between the primary flywheel 1 and the secondary flywheel 2 can be between 0.7 and 5 degrees, in particular between 1 and 3 degrees.

Advantageously, the end-of-travel device of the torsion damper can have a stiffness of between 1000Nm / ^e and 6000Nm / ^e . Furthermore, the blade may have an elastic limit between 900 and 1500 MPa.

FIG. 9 illustrates an alternative embodiment of the axial holding member of the blade 11 on the primary flywheel 1. In this variant, the holding plate 22 is replaced by a rivet 40 with a shouldered head mounted on the primary flywheel 1. A head 41 of this rivet protrudes from the primary plate 3 in the direction of the secondary flywheel 2. One end of the rivet head 41 opposite the primary plate 3 has a shoulder 42 developing radially in the direction of the blade 11 and axially covering the blade 11. This shoulder 42 can take different forms, such as a washer shape or a square shape. This rivet 40 with a shouldered head can be positioned in different places on the primary plate 3.

The blade is shown in Figures 1 to 7 as a lamella but could take different forms, in particular at its circumferential ends.

Thus in FIG. 10, it can be seen that at least one of the circumferential ends 14, 15 of the blade 11 can be bent. A contact portion of the blade 11, formed on this curved portion, can thus be more radially extended.

In Figure 11, we see that the central portion 13 of the blade 11 may have different arcuate portions 13a, 13b, 13c. Thus, the blade 11 can be made more flexible.

For example, a radially outwardly arcuate portion 13b is arranged circumferentially between two radially inwardly arcuate portion 13a and 13b.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention. In particular, the above description is made in the context of a torsional damper comprising a damping member formed by flexible arms but said damping member 10 could include helical springs.

The use of the verb "comprise", "understand" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those set out in a claim.

In the claims, any reference sign in parentheses should not be interpreted as a limitation of the claim.

Claims (14)

1. Torsional damper for a torque transmission device comprising: - a first element (1) and a second element (2) movable in rotation relative to one another about an axis of rotation X; and - an elastic damping member (6) arranged between the first element (1) and the second element (2) for transmitting a torque and damping acyclisms between the first element (1) and the second element (2), the torsional damper being characterized in that it comprises an end-of-travel device capable of opposing the angular movement between the first element (1) and the second element (2) according to at least a first direction of relative rotation (32 ), when the angular movement between the first element (1) and the second element (2) is greater than a first movement threshold (33) from a rest position in which no torque transits between the first element (1) and the second element (2), the limit switch device comprising: - a first abutment surface (29) carried by the second element (2), - an elastic blade (11) carried by the first element (1), said elastic blade (11) comprising a first contact portion (14) and a first support portion (15) separated circumferentially from one another by an elastically deformable central portion (13) of the elastic blade (11), the first bearing portion (15) being arranged to bear against a first bearing surface (36) carried by the first element (1), and the first contact portion (14) being arranged in circumferential relation to the first abutment surface (29) in such a way that the first contact portion (14) is: o at a distance from the first abutment surface (29) when the angular movement between the first element (1) and the second element (2) in the first direction of rotation (32) is less than the first movement threshold (33), and o urged and moved by the first abutment surface (29) when said angular travel is greater than the first travel threshold (33), the elastic blade (11) being pressed between the first abutment surface (29) and the first surface support (36) by producing an elastic restoring force acting against the angular movement between the first element (1) and the second element (2) in the first direction of rotation (32). 2. Torsional damper according to one of the preceding claims, in which the elastic blade (11) has a first end and a second end respectively forming the first contact portion (14) and the first support portion (15). 3. Torsional damper according to claim 1 or 2, in which the end-of-travel device further comprises a guide device (20, 21) arranged to circumferentially guide the movement of the first contact portion (14) of the blade. (11) elastic when said first contact portion (14) is biased by the first abutment surface (29). 4. Torsional damper according to claim 3, in which the guide device comprises a first guide surface (21) and a second guide surface (20) carried by the first element (1), said first and second guide surfaces. being arranged radially on either side of the first contact portion (14) of the elastic blade (11). 5. Torsion damper according to one of claims 1 to 4, in which the first element (1) comprises a cavity (16) facing the second element (2), the elastic blade (11) being housed in said cavity ( 16) and projecting from the cavity (16) in the direction of the second element (2), the cavity (16) having radial dimensions in a plane orthogonal to the axis of rotation X greater than the radial dimensions of the central portion (13 ) blade (11) elastic in said plane orthogonal to the axis of rotation X so as to allow the deformation of the central portion (13) of the blade (11) elastic in said cavity (16). 6. Torsional damper according to claim 5, in which a first circumferential end (26) of the cavity forms the first bearing surface (36). 7. Torsional damper according to one of claims 5 to 6, in which the elastic blade (11) is prestressed circumferentially in the cavity (16). 8. Torsion damper according to one of the preceding claims, in which the end-of-travel device further comprises a rigid stop comprising a first stop surface (19, 31) carried by the first element (1) and a second stop surface carried by the second element (2), said first and second stop surfaces being facing each other circumferentially and arranged for: - on the one hand, to be distant from each other during a relative rotation between the first element (1) and the second element (2) according to the first direction of rotation (32) less than a first relative clearance maximum between the first element (1) and the second element (2), said first maximum relative travel being greater than the first travel threshold (33), and, - on the other hand, to be in abutment against each other in order to limit the relative angular movement between the first element (1) and the second element (2) according to the first direction of rotation (32) when said angular movement relative reaches said first maximum relative travel. 9. Torsional damper according to one of claims 1 to 8, in which the end-of-travel device further comprises a second bearing surface (28) carried by the first element (1) and a second abutment surface ( 30) carried by the second element (2), the elastic blade (11) comprising a second bearing portion (14) and a second contact portion (15) separated from each other by the central portion (13 ) elastic of the elastic blade (11), the second bearing portion (14) being arranged to bear against the second bearing surface (28), and the second contact portion (15) being arranged opposite -circumferential screw of the second abutment surface (30) in such a way that the second contact portion (15) is: - away from the second abutment surface (30) when the angular clearance between the first element (1) and the second element (2) in a second direction of rotation (35) opposite to the first direction of rotation (32) is less at a second deflection threshold from the rest position, and - stressed and moved by the second abutment surface (30) when said angular clearance is greater than said second deflection threshold, the elastic blade (11) being pressed between the second abutment surface (30) and the second bearing surface ( 28) and by producing a restoring force acting against the angular movement between the first element (1) and the second element (2) according to the second direction of rotation (35). 10. Torsional damper according to the preceding claim in combination with claim 2, wherein the first and second ends of the elastic blade (11) respectively form the first contact portion (14) and the second contact portion (15). 11. Torsional damper according to the preceding claim, wherein the first end forms both the first contact portion and the second support portion, and the second end forms both the second contact portion and the first portion d 'support. 12. Torsional damper according to one of the preceding claims, in which the elastic blade (11), in particular its central portion (13), is arcuate in a plane perpendicular to the axis of rotation so as to flex with components radial and circumferential. 13. Torsional damper according to one of the preceding claims, in which the damping member comprises a flexible arm (6) carried by one of the first (1) and the second element (2) and cooperating with a support element (7) arranged between the flexible arm (6) and the other from the first element (1) and the second element (2) to cooperate with said flexible arm (6), the support element ( 7) and the flexible arm (6) being arranged so that, during an angular movement between the first element (1) and the second element (2), the support element (7) exerts a force of bending on the flexible arm (6) producing a reaction force capable of transmitting a torque and damping the acyclic rotation between the first element (1) and the second element (2), the flexible arm (6) comprising a cam surface (10) and the support element (7) comprising a cam follower arranged to move on the surface cam face (10) when a torque is transmitted by the shock absorber and the first element (1) and the second element (2) rotate relative to each other, the elastic blade (11) of the device limit switch extending circumferentially on either side of the cam follower (7). 14. Torsional damper according to the preceding claim, wherein the elastic blade is arranged radially outside the cam follower.