WO2016198452A1

WO2016198452A1 - Torsion damper

Info

Publication number: WO2016198452A1
Application number: PCT/EP2016/063037
Authority: WO
Inventors: Carlos Lopez Perez
Original assignee: Valeo Embrayages
Priority date: 2015-06-08
Filing date: 2016-06-08
Publication date: 2016-12-15
Also published as: FR3037113A1

Abstract

Torsion damper (101, 201) for a torque transmitting device, notably for an automobile, particularly for a clutch device, the damper being arranged in such a way that the torsional stiffness of the damper decreases over a predetermined angular range of decreasing stiffness (P2; P5), with increasing distance away from a relative angular position of rest (P0).

Description

TORSION DAMPER

Technical field of the invention

The invention relates to a torsion damper for equipping a torque transmission device. The invention relates more particularly to the field of transmissions for a motor vehicle. This damper can be applied to a transmission device for a manual gearbox automobile, such as a damped friction disc or a double damping flywheel, as well as to a transmission device for an automobile with an automatic gearbox, such as a gearbox. torque converter or lock-up. State of the art

Torsional dampers are known whose input and output elements are coupled in rotation by damping means for transmitting a torque and damping rotation acyclisms. The damping means are generally helical, bent, circumferentially disposed springs in an annular, sealed chamber which is formed between the input and output members.

The damping proposed by these dampers is not entirely satisfactory, in particular because of the high friction, and it has also been proposed to produce torsion dampers with a blade, as described in document FR3000155 which illustrates a damper torsion device comprising elastic damping means formed by an elastic blade provided with a cam, and cooperating with a cam follower.

The damper of document FR2938030 is also known. Object of the invention

One aspect of the invention is based on the idea of solving the disadvantages of the prior art by proposing an elastic blade torsion damper which is particularly efficient and in which the performance of the damping is improved.

The invention thus relates to a torsion damper for a torque transmission device, in particular for a motor vehicle, in particular for a clutch device, the damper being arranged so that the torsional stiffness of the damper decreases over a predetermined angular range. decreasing stiffness away from a relative angular position of rest.

The angular stiffness of the damper is decreasing in the predetermined angular range of decreasing stiffness. In other words, in this angular range, the angular stiffness of the damper decreases when the angular displacement of the damper increases relative to the relative angular position of rest. Angular stiffness is defined as the derivative of the torque / angle characteristic curve. Thus, the presence of angular ranges of decreasing stiffness makes it possible to reduce the angular stiffness in certain ranges of angular displacement for which better damping is desired.

When the stiffness decreases sufficiently to a minimum value, the torsional filtering is greatly improved. The ability of the damper to decrease the stiffness over certain angular operating ranges allows to customize the desired damping curve according to the specificities of the engine.

According to one embodiment of the invention, the damper comprises:

a first element and a second element movable in rotation with respect to each other about an axis of rotation X; the first and second elements being in the relative angular position of rest in the absence of torque transmission,

a transmission member carried by one of the first and second elements, this transmission member comprising an elastic blade arranged to flex to transmit a torque between these two elements, the bending of the elastic blade being accompanied by a rotation relative between the first and second elements, according to the axis of rotation X, for damping the rotation acyclisms between the first element and the second element, - a support element carried by the other of said first and second elements and arranged to cooperate with the blade

one of the support elements and the elastic blade comprises a cam surface and the other of the support element and the elastic blade comprises a cam follower arranged to move on the cam surface during a relative rotation between the first and second elements.

The damper may have one or more of the following characteristics:

The predetermined angular range of decreasing stiffness can be separated from the relative angular position of rest by at least 10 degrees, in particular by at least 20 degrees, for example by at least 30 degrees.

The cam surface can be arranged so that the torsional stiffness of the damper decreases over the predetermined angular range of decreasing stiffness. Thus, the stiffness of the damping can be modified by modifying the cam surface.

The angular stiffness of the damper may be a function of the profile of the cam surface. Thus a modification of the profile of the cam surface results in a modification of the damping curve. The angular stiffness of the damper does not depend in particular on other elastic members such as coil springs.

The predetermined angular range of decreasing stiffness can be separated from the relative angular position of rest by at least one angular range of constant or increasing stiffness.

The predetermined angular range of decreasing stiffness may be adjacent to the angular range of constant or increasing stiffness. The predetermined angular range of decreasing stiffness can be between two angular ranges of constant or increasing stiffness.

The damper may have several angular ranges of decreasing stiffness.

Two angular ranges of decreasing stiffness can be provided on the same side of the relative angular position of rest. These two decreasing stiffness ranges can be separated from each other. Advantageously, these two decreasing stiffness ranges are spaced apart from the relative angular position of rest.

The damper may comprise a maximum angular displacement position.

The damper may comprise stops arranged to come into contact with each other in the angular position of maximum travel. These stops can be integral in rotation of the first and second elements.

The predetermined angular range of decreasing stiffness can be separated from the maximum angular deflection position by at least 10 degrees, in particular by at least 20 degrees, for example by at least 30 degrees.

The damper may be arranged so that the torsional stiffness of the damper is substantially equal to 0 for a predetermined relative angular position of zero stiffness, remote from the relative angular position of rest, the torsional stiffness of the damper being different from 0 between the angular rest position and the zero stiffness position.

By substantially zero is meant any stiffness value close to zero for a vehicle damper, for example between 0 N.m / degree and 3 N.m / degree. The predetermined relative angular position of zero stiffness is a point of inflection of the damping curve of the damper. The torsional stiffness of the damper may be substantially equal to 0 over at least one angular range of zero stiffness which comprises said angular position of zero stiffness.

The damper may comprise several angular ranges of zero stiffness separated from each other. In other words, the torque / angle torque curve of the damper comprises at least one zone of substantially constant torque in at least one angular range of deflection.

Thus, the presence of angular ranges of zero stiffness or substantially equal to 0 improves the filter quality of the damper. In these angular ranges, the filtering properties of the damper are significantly improved. It is possible to avoid resonance phenomena. In the angular ranges of stiffness substantially equal to 0, the filtering of torsional vibrations becomes ideal.

If desired, the damper is arranged such that the angular range of zero stiffness is obtained for a torque comprised between 20% and 60% of the maximum engine torque, in particular between 25% and 50% of the maximum engine torque, example 30% of the maximum engine torque.

The damper can be arranged so that an angular range of zero stiffness is obtained for a torque substantially equal to the maximum engine torque.

The maximum angular displacement position can be located on an angular range of zero stiffness.

The predetermined angular range of decreasing stiffness may be between said at least one constant or increasing stiffness range and the zero stiffness angular range. The zero stiffness range may be adjacent to the predetermined angular range of decreasing stiffness.

The zero stiffness range may be adjacent to the predetermined angular range of decreasing stiffness, on the opposite side to the relative angular position of rest.

The zero stiffness range may be adjacent to the at least one angular range of constant or increasing stiffness.

The zero stiffness range may be between the predetermined angular range of decreasing stiffness and said at least one angular range of constant or increasing stiffness. Advantageously, the torsional stiffness can be between 0

N. m / degree and 3 N.m / degree, especially between 0 N.m / degree and 2 N.m / degree, especially between 0 N.m / degree and 1 N.m / degree, in particular between 0 N m / degree and 0.5 Nm / degree over the angular range of zero stiffness. If desired, the angular range of zero stiffness has an amplitude of between 1 and 30 degrees, especially between 2 and 20 degrees, for example between 3 and 10 degrees.

The cam surface can be arranged so that the torsional stiffness of the damper is substantially equal to 0 in the angular range of zero stiffness.

The damper may comprise several angular ranges of zero stiffness between which the stiffness of the damper is greater than 5 N.m / degree, especially greater than 10 N.m / degree.

If desired, the damper comprises an angular range of zero stiffness for a torque comprised between 25% and 50% of the maximum engine torque, and another zero stiffness range for a torque of between 80% and 100% of the torque. maximum engine. The damper can be arranged so that the zero stiffness range is obtained for a torque substantially equal to the maximum engine torque. If desired, the damper is arranged so that the angular range of zero stiffness is within an intermediate range of angular deflection of between 30% and 70% of the maximum range of angular deflection considered in a given direction of rotation by relative to the relative angular position of rest, in particular between 40% and 60% of this range.

The resilient blade and the bearing member may be arranged such that in operation the bearing member exerts a bending force on the blade and responsively produces a reaction force of the blade on the member. bearing adapted to recall the first and second elements to said angular position of rest.

The damper may be arranged such that, in the areas of constant or increasing stiffness, the support member bends the blade when the angular position of the first and second members deviates from the angular position of rest.

Flexion of the blade may be accompanied by relative rotation between the first and second members.

The elastic blade may comprise a free end zone and the damper is arranged so that this free end moves with a radial component when the bearing element bends the elastic blade.

The cam surface can be arranged so that the damper has at least a predetermined range of decreasing stiffness.

The cam surface can be arranged so that the damper has at least a predetermined range of zero stiffness.

The cam surface may be arranged so that the damper has at least one predetermined range of constant or increasing stiffness. The cam surface may comprise at least one region of increasing stiffness arranged so that the angular stiffness of the damper increases when the cam follower moves on this area away from the relative rest position.

The cam surface may comprise two zones of increasing stiffness distant from each other. The cam surface may comprise at least one decreasing stiffness zone arranged so that the angular stiffness of the damper decreases as the cam follower moves on this area away from the relative rest position. The cam surface may comprise two zones of decreasing stiffness distant from each other.

The cam surface may comprise as many zones of decreasing stiffness as the damper has angular ranges of decreasing stiffness.

The cam surface may comprise at least one zone of zero stiffness arranged so that the angular stiffness of the damper is substantially equal to 0 when the cam follower moves on this zone away from the relative position of rest.

The cam surface may comprise two zones of zero stiffness distant from each other. The cam surface may be arranged so that the bearing element exerts on the spring blade a load whose support, normal to the point of contact between the blade and the support element, is separated from the axis of rotation of the damper a distance called lever arm, so that the torque equal to the product of the load and the lever arm is not zero. Here we call support of the force, the line passing through the point of contact of the force and parallel to the vector of the force.

The cam surface may be carried by the resilient blade and the cam follower may be carried by the bearing member. Thus, one can modify the stiffness of the damping by modifying only the blade of the shock absorber.

The cam follower may be formed by a roller rotatably mounted on itself on one of the first and second members.

If desired, the cam follower is integral in rotation with one of the first and second elements relative to the axis of rotation of the damper.

Alternatively, the cam follower is a rolling body movable in rotation with respect to the first and second members. The rolling body moves on the one hand on the elastic blade carried by one of the first and second elements, including rolling and bending, on the other hand on the other of the first and second elements. Preferably, by rolling on the elastic blade carried by one of the first and second elements, the rolling body accomplishes a curvilinear path on the other of the first and second elements on at least one predetermined angular sector, including rolling.

The cam surface can be arranged so that the cam follower exerts on the spring blade a load whose support, normal to the point of contact between the blade and the cam follower, is separated from the axis of rotation of the cam. damping a distance called lever arm, so that the torque equal to the product of the load and the lever arm is not zero. Here we call support of the force, the line passing through the point of contact of the force and parallel to the vector of the force. Thanks to this condition, the angular range of zero stiffness of the damper does not behave like an angular position of rest.

In other words, in operation, that is to say outside the angular position of rest, including in the zero stiffness range, the cam surface is arranged so that the support element produces effort associated with a non-zero lever arm.

In other words, in operation, that is to say outside the angular position of rest, including in the zero stiffness range, the cam surface is arranged so that the line along which the support element produces a bending force on the blade is distant from the axis of rotation of the damper.

To ensure that, in the angular range of zero stiffness, the transmitted torque is substantially the same, it is necessary that the product of the load applied by the support element on the blade and the lever arm is constant. The load considered here is the force necessary to bend, on a given contact point of the blade, this point of contact to the circular path followed by the support element, in particular the cam follower.

Likewise, the cam surface is arranged so that the values of the load and the lever arm are kept greater than 0 in the zero stiffness range. Thus, the damper remains reversible outside its relative angular position of rest, that is to say that the cam follower does not remain blocked on the angular range of zero stiffness.

According to a second embodiment, the cam surface is carried by the support element and the cam follower is carried by the elastic blade, in particular on its free end zone.

Where appropriate, the blade comprises a radially movable free distal end such that the radial distance separating the axis of rotation from said free distal end varies as a function of the angular displacement between the first and the second elements.

In one embodiment of the invention, the torsion damper is intended to transmit a torque between a vehicle engine and a gearbox input shaft, the torque capable of being transmitted in the angular range. predetermined decreasing stiffness is a positive torque traveling from the motor to the input shaft of the gearbox.

In other words, the torque transmitted by the damper in the angular range of decreasing stiffness is transmitted in the direct direction, that is to say from the engine to the gearbox.

The torsion damper may furthermore have one or more of the following characteristics: the blade is arranged to deform in a plane perpendicular to the axis of rotation X.

- The transmission member may be formed by a stack of lamellae.

- The transmission member comprises two blades arranged symmetrically with respect to the axis of rotation.

- The transmission member comprises a plurality of blades regularly arranged around the axis of rotation.

- Where appropriate, the transmission member with its blades are formed integrally on the same part, this part itself can be formed by a stack of lamellae.

alternatively, the damper comprises two transmission members arranged symmetrically with respect to the axis of rotation.

- Where appropriate, the two transmission members are mounted at a distance from each other, these transmission members being formed on separate parts

- The damper comprises a plurality of transmission members regularly arranged around the axis of rotation.

each transmission member comprises a single blade.

- For a predetermined angular sector, the transmission member comprises two flexible blade regions radially offset from one another in a radial direction, a free space radially separating said two flexible blade regions.

one of the flexible blade regions is located between the axis of rotation and the other of the flexible blade regions. the free end zone is radially movable so that the radial distance separating the axis of rotation from said free distal end varies as a function of the angular displacement between the first and second elements.

the angular sector along which the two flexible blade regions are radially offset from each other extends over at least 1 ° for example over at least 5 °, preferably at least 10 °, notably at least 30 ° .

- The transmission member comprises a fixing portion on one of the first and second elements and a flexible portion comprising the elastic blade.

preferably, the fixing portion remains fixed, in other words it does not flex when the first and second elements rotate relative to one another.

the elastic blade comprises an internal strand and an external strand connected by a bend, the inner strand developing from the attachment portion to the elbow and the outer strand developing circumferentially from the elbow to the free distal end, the inner strand having one of the two blade regions flexible and radially offset from the transmission member and the outer strand having the other of the two blade regions flexible and radially offset from the transmission member.

- The fixing portion develops circumferentially over a length less than the length of the outer strand of the elastic blade.

the fixing portion develops circumferentially over a length less than 50% of the length of the outer strand, preferably less than 30%.

- Said at least one support element is disposed radially outside the outer strand of said at least one blade.

the outer strand extends circumferentially over at least 45 ° and can extend circumferentially up to 180 ° in a bent state of the blade corresponding to a maximum angular displacement between the first element and the second element,

the damper comprises two resiliently deformable blades mounted integral with one of said first and second elements and the damper comprises two bearing elements carried by the other of said first and second elements, the support elements being respectively arranged to cooperate with both of the two elastically deformable blades, and each blade has two flexible blade regions radially offset from each other, a free space radially separating said flexible blade regions of each of the blades.

- The elastically deformable blades are symmetrical with respect to the axis of rotation.

the distal end of each elastically deformable blade comprises an internal clearance, the clearance of a blade having a radius of curvature greater than the radius of curvature of an outer surface of the other blade so that said external surface of the another blade can fit into the clearance.

the elastically deformable blades are fixed at a distance from one another to the first or second element.

- The blade of the flexible portion has a cam surface and said at least one support member comprises a cam follower arranged to cooperate with the cam surface.

- The cam follower is a roller rotatably mounted on the first or second element, by means of a rolling bearing.

The invention also relates to a torque transmission element, in particular for a motor vehicle, comprising a torsion damper mentioned above.

The invention also relates to a torsion damper for a torque transmission device, in particular for an automobile, in particular for a clutch device, the damper being arranged such that the torsional stiffness of the damper is substantially equal to 0 on a predetermined angular range of zero stiffness.

The torsional stiffness can be between 0 N.m / degree and 3 N.m / degree, in particular between 0 N.m / degree and 2 N.m / degree, in particular between 0 N.m / degree and 1 N.m / degree, especially between ON. m / degree and 0.5 Nm / degree over the predetermined angular range of zero stiffness.

According to one embodiment, this torsion damper is intended to transmit a torque between a vehicle engine and a box input shaft. speed, the torque capable of being transmitted in the predetermined angular range of zero stiffness is a positive torque traveling from the motor to the input shaft of the gearbox.

In other words, the torque transmitted by the damper in the angular range of zero stiffness is transmitted in the direct direction, that is to say from the engine to the gearbox.

This damper may comprise:

a first element and a second element movable in rotation relative to each other about an axis of rotation X; the first and second elements being in the relative angular position of rest in the absence of torque transmission,

a transmission member carried by one of the first and second elements, this transmission member comprising an elastic blade arranged to flex to transmit a torque between these two elements, the bending of the elastic blade being accompanied by a rotation relative between the first and second elements, along the axis of rotation X, for damping the rotation acyclisms between the first element and the second element,

a support element carried by the other of said first and second elements and arranged to cooperate with the blade

one of the support elements and the elastic blade comprises a cam surface and the other of the support element and the elastic blade comprises a cam follower arranged to move on the cam surface during a relative rotation between the first and second elements,

This angular range of zero stiffness is separated from the relative angular rest position by an angular range of non-zero stiffness, constant or increasing.

One aspect of the invention is based on the idea of reducing the stiffness of the damper on certain ranges of angular displacement in order to allow a better damping of the acyclisms. One aspect of the invention is based on the idea of increasing the maximum angular deflection between the input element and the output element. An object of the invention is to provide a torsion damper for filtering quality acyclisms. An object of the invention is to provide an elastic blade having a significant length. An object of the invention is to provide a blade having a cam surface of great length.

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the appended figures.

In these figures:

FIG. 1 is a front view of a double damping flywheel illustrating the general operation of a torsion damper, in which the secondary flywheel is represented, in a transparent manner, so as to visualize the transmission member .

- Figure 2 is a sectional view of the double damping flywheel of Figure 1, according 11-ll.

- Figure 3 is a perspective view of the double damping flywheel of Figure 1.

- Figure 4 is a perspective view of the double damping flywheel of Figures 1 to 3, wherein the secondary flywheel is shown, partially broken away and disassembled from the primary flywheel.

- Figure 5 is a schematic view of a torsion damper according to a first embodiment of the invention in the rest position.

- Figure 6 is a schematic view of the torsion damper of Figure 5 in a maximum angular displacement position between the first element and the second element.

FIG. 7 is an example of a characteristic curve obtained with a double damping flywheel according to the first embodiment, representing the torque transmitted as a function of the angular displacement.

- Figure 8 is a schematic and partial view of the blade and the cam follower of the first embodiment.

- Figure 9 is a schematic view of the blade transmission member of the first embodiment illustrating the deflection of the blade during an angular movement between the flywheels, primary and secondary in a forward direction. - Figure 10 is a schematic and partial view of a blade damper, according to a second embodiment.

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 elements of the torsion damper determining the "axial" orientation and, from the inside towards the outside while moving away of said axis, the "circumferential" orientation is directed orthogonally to the axis of rotation of the torsion damper and orthogonal to the radial direction. Thus, an element described as circumferentially developing is an element whose component develops in a circumferential direction. Similarly, the indication of an angle is interpreted as delimited by two lines of a plane perpendicular to the axis of rotation X and secant at said axis of rotation X. The terms "external" and "internal" are used to define the relative position of one element relative to another, with reference to the axis of rotation of the torsion damper, an element close to the axis is thus described as internal as opposed to an external element located radially at the periphery.

Referring first to Figures 1 to 4 which illustrate the general operation of a torsion damper with elastically deformable blades fitted to a double damping flywheel 1. The first and second elements are formed here by the flywheels of primary and secondary inertia . The double damping flywheel 1 comprises a primary flywheel 2, intended to be fixed at the end of a crankshaft of an internal combustion engine, not shown, and a secondary flywheel 3 which is centered and guided on the primary flywheel 2 by means of a rolling ball bearing 4. The secondary flywheel 3 is intended to form the reaction plate of a clutch, not shown, connected to the input shaft of a gearbox. The primary flywheels 2 and secondary 3 are intended to be mounted movable about an axis of rotation X and are, moreover, rotatable relative to each other about said axis X.

The primary flywheel 2 comprises a radially inner hub 5 supporting the rolling bearing 4, an annular portion 6 extending radially from the hub 5 and a cylindrical portion 7 extending axially, on the opposite side to the motor, from the outer periphery of the annular portion 6. The annular portion 6 is provided, on the one hand, with screw holes 8 for fixing , intended for fixing the primary flywheel 2 on the crankshaft of the engine and, on the other hand, for passing rivets 9 for attaching a transmission member to the primary flywheel 2. The primary flywheel 2 carries, on its outer periphery, a ring gear 10 for driving in rotation of the primary flywheel 2, using a starter.

The hub 5 of the primary flywheel has a shoulder 1 1 serving to support an inner ring of the rolling bearing 4 and which retains said inner ring towards the motor. Similarly, the secondary flywheel 3 has on its inner periphery a shoulder 12 serving to support an outer ring of the rolling bearing 4 and retaining said outer ring in the opposite direction to the motor.

The secondary flywheel 3 comprises a flat annular surface 13, turned on the opposite side to the primary flywheel 2, forming a bearing surface for a friction lining of a clutch disc, not shown. The secondary flywheel 3 has, close to its outer edge, pads 14 and orifices 15 for mounting a clutch cover. The secondary flywheel 3 further comprises orifices 16, arranged vis-à-vis the orifices formed in the primary flywheel 2, and for the passage of the screws 8, when mounting the double damping flywheel 1 on the crankshaft.

The primary flywheels 2 and secondary 3 are coupled in rotation by a transmission member 30. In the embodiment shown in Figures 1 to 4, this damping means comprises two resilient blades 17a, 17b mounted integral in rotation with the primary flywheel 2. To do this, the elastic blades 17a, 17b are carried by an annular body 18 provided with orifices allowing the passage of the fastening rivets 9 to the primary flywheel 2. The annular body 18 further comprises orifices 19 for the passage of screw 8 for fixing the double damping flywheel 1 to the nose of the crankshaft. The two resilient blades 17a, 17b are symmetrical with respect to the axis of rotation X of the clutch disc.

The elastic blades 17a, 17b have a cam surface 20. The secondary flywheel 3 has two support elements 24 which each comprise a cam follower 21 arranged to cooperate each with a cam surface of their own. The resilient blades 17a, 17b have a curved portion extending substantially circumferentially. The radius of curvature of the curved portion and the length of this curved portion are determined according to the desired stiffness of each elastic blade 17a, 17b. Each elastic blade 17a, 17b may, as desired, be made in one piece or be composed of a plurality of lamellae arranged axially against each other.

The bearing elements comprise cam followers formed by rollers 21 carried by cylindrical rods 22 fixed on the one hand to the secondary flywheel 3 and on the other hand to a web 23. The rollers 21 are mounted to rotate on the cylindrical rods 22 about an axis of rotation parallel to the axis of rotation X. The rollers 21 are held in abutment against their respective cam surface 20 and are arranged to roll against said cam surface 20 during a relative movement between the primary and secondary flywheels 3. The rollers 21 are arranged radially outside their respective cam surface 20 so as to radially maintain the elastic blades 17a, 17b when subjected to centrifugal force. In order to reduce the parasitic friction likely to affect the damping function, the rollers 21 are advantageously mounted in rotation on the cylindrical rods by means of a rolling bearing. For example, the rolling bearing may be a ball bearing or roller. In one embodiment, the rollers 21 have an anti-friction coating.

Each cam surface 20 is arranged such that, for an angular displacement between the primary flywheel 2 and the secondary flywheel 3, relative to a relative angular position of rest, each roller 21 moves on the cam surface 20 which is clean and, in doing so, exerts a bending force on the elastic blade 17a, 17b. By reaction, the elastic blade 17a, 17b exerts on the roller 21 a return force which tends to bring the primary flywheels 2 and secondary 3 to their relative angular position of rest. Thus, the resilient blades 17a, 17b are able to transmit a driving torque from the primary flywheel 2 to the secondary flywheel 3 (forward direction) and a resistant torque of the secondary flywheel 3 to the primary flywheel 2 (retro direction). The torsional vibrations and the irregularities of torque that are produced by the internal combustion engine are transmitted by the crankshaft to the primary flywheel 2 and generate relative rotations between the primary flywheel 2 and secondary 3. These vibrations and irregularities are damped. by flexing the elastic blades 17a and 17b of the transmission member.

FIG. 5 represents a schematic view of a torsion damper according to the invention in the rest position according to a first embodiment of the invention. FIG. 6 represents a schematic view of this damper in the position of maximum angular deflection, in the retro direction. With reference to FIGS. 5 and 6, elements identical or similar to the elements of FIGS. 1 to 4, that is to say fulfilling the same function, bear the same reference numeral increased by 100.

In Figures 5 and 6, the damper comprises two transmission members 130a, 130b mounted remote from each other on the secondary flywheel 103, symmetrically about the axis of rotation X, and each transmission member 130a, 130b comprises a single elastic blade 1 17.

Each transmission member 130a, 130b has a fastening portion 1 18 fixed relative to the secondary flywheel 103 to allow the rotation of the elastic blades 117 with the secondary flywheel 103. A cam surface 120 is carried by each elastic blade 17. The primary flywheel 102 comprises a support element 124 which comprises a cam follower formed by a roller 121 rotatable about a rod 122 fixed on the primary flywheel 102. The roller is thus rotatably mounted on itself on the primary flywheel 102. The cam follower 121 is integral in rotation with the primary flywheel 102 relative to the axis of rotation of the damper.

Alternatively, to increase the angular deflection, the cam follower could be rotatable relative to the first and second members. The cam follower, or rolling body, would move on the one hand on the elastic blade carried by the secondary flywheel, including rolling and bending, on the other hand on the primary flywheel. Preferably by rolling on the elastic blade worn by the secondary flywheel, the rolling body would perform a curvilinear path on the primary flywheel on at least one predetermined angular sector, including rolling.

A rolling bearing 104 is mounted between the primary flywheel 102 and the secondary flywheel 103. This rolling bearing 104 has an outer ring 127 carried by the secondary flywheel 103 which cooperates with an inner ring 128 carried by the primary flywheel 102. The fixing portion 1 18 of the transmission members 130a, 130b develops circumferentially around the outer ring 127. The inner ring 128 of the rolling bearing 104 is carried by the hub 105 of the primary flywheel 102.

The fixing portion 118 of each transmission member 130a, 130b is fixed to the secondary flywheel 103 by three rivets 129.

The fixing portion 1 18 fixed on the secondary flywheel 103 is extended by a flexible portion. The deformable flexible portion comprises an elastically deformable blade 117. The blade 117 carries on a radially outer face a cam surface 120 cooperating with the cam follower 121.

Each elastic blade 1 17 has an internal strand 132, a bend 133 and an outer strand 134. The inner strand 132 of a blade 117 extends the attachment portion 118. The bend 133 extends the inner strand 132 and the outer strand 134 extends the elbow 133.

The inner strand 132 develops circumferentially around the outer ring 127 from the attachment portion 1 18 to the elbow 133. The inner strand 132 is not secured by the rivets 129 to the secondary flywheel 103. can be deformed during an angular travel between the primary flywheel 102 and the secondary flywheel 103. Thus, the internal strand 133 absorbs a portion of the stresses experienced by the resilient blade 1 17 during this angular deflection.

The elbow 133 forms an angle of approximately 180 ° so that a first end 135 of the contiguous elbow 133 of the inner strand 132 is located radially between the axis of rotation X and a second end 136 of the contiguous elbow 133 of the outer strand 134 The elastic blade 117 thus has the general shape of a hairpin hair of which one branch is formed by the outer strand 134 and the other branch is formed jointly by the fixing portion 1 18 and the inner strand 132. In other words, the blade 1 17 comprises two radially offset flexible blade regions from each other and separated by an empty space. The outer strand 134 develops circumferentially from the elbow

133 to the free end 137 of the elastic blade 117. The outer strand 134 develops over a circumference of at least 45 ° and up to 180 ° in the bent state of the elastic blade 117. The cam surface 120 develops on an outer face of the outer strand 134. Advantageously, the cam surface 120 develops circumferentially at an angle of about 125 ° to 130 °. The cam surface 120 develops circumferentially according to a radius of curvature determined according to the desired stiffness of the elastic blade 117. This cam surface 120 may have different radii of curvature depending on the desired point stiffnesses, in order to allow variations in slope of the characteristic curve of the torsion damper, representing the torque transmitted as a function of the angular deflection.

The transmission members 130a and 130b and their elastic blade 117 shown schematically in Figure 5 are symmetrical with respect to the axis of rotation X. In Figure 6, it can be seen that when a resistive torque is transmitted from the primary flywheel 102 to the secondary flywheel 103 (retro direction), the torque to be transmitted causes a relative movement between the primary flywheel 102 and the secondary flywheel 103 in a first direction. The rollers 121 are then moved by an angle Ω with respect to the elastic blades 1 17. The displacement of the rollers 121 on the cam surfaces 120 causes the resilient blades 1 17 to bend.

The flexion of the elastic blades 1 17 causes the approximation of the outer strands 134 of the blades 117 with the attachment portion 118 of their transmission member and, on the other hand, the approach of the free end 137 of the blade 1 17 of one of the transmission members 130a, 130b with the elbow 133 of the blade 1 17 of the other transmission members 130a, 130b. Preferably, these approximations must not cause contacts between the external strand 134 and the fixing portion 118, such contacts generating disturbances in the damping of acyclisms and vibrations.

To avoid such contacts, the circumferential length of the fixing portion 1 18 is limited so that, in the rest position shown in Figure 5, the fixing portion 1 18 does not develop circumferentially beyond the axis formed by the alignment between the cam follower 121 and the axis of rotation X. Preferably, an end 138 of the attachment portion 1 18 opposite the flexible portion comprising the blade 117 is located between the corresponding cam follower 121 and the axis of rotation X during a maximum angular deflection in the retro direction between the primary flywheel 102 and the secondary flywheel 103, as represented by the axis 143. Such a maximum angular displacement is for example limited by an end stop stroke comprising a stop 139 on the primary flywheel 102 facing circumferentially a stop 140 on the secondary flywheel 103. In another embodiment, not shown, to avoid contact between the briar n external 134 of an elastic blade 117 and the attachment portion 1 18 of the transmission member 130, the thickness of the fixing portion 118 is reduced relative to the thickness of the elastic blade 1 17, and more particularly at least the thickness of the end 138 of the fixing portion 118 is reduced with respect to the thickness of the flexible portion. To avoid contact between the free end 137 of the blade 1 17 of one of the transmission members 130a and the bend 133 of the blade 117 of the other transmission members 130b, the free end 137 of the blades 1 17 has a clearance 141.

The length of the elastic blade 117 and the arrangement of the outer strand 134, the elbow 133 and the inner strand 132 of the elastic blade 117 allows the transmission of a high torque without risk of degradation of the elastic blades 117 or loss of cooperation between cam followers 121 and cam surfaces 120.

The resilient blades 17 and the support members, here the cam followers 121, are arranged such that in operation each cam follower 121 exerts a bending force on each blade 117 causing them to flex, and producing reaction a reaction force of the blade on the cam follower able to recall the primary and secondary flywheels 102 and 103 to said angular position of rest.

The damper is arranged so that the support elements 121 bend the blades 1 17 when the angular position of the primary and secondary flywheels deviates from the angular position of rest.

The bending of the blades 117 is accompanied by a relative rotation between the primary and secondary flywheels 102 and 103.

Each elastic blade 1 17 has a free end zone 137 and the damper is arranged so that this free end 137 moves with a radial component when the bearing element 121 bends the elastic blade 1 17. This double damping flywheel therefore includes:

a primary flywheel 102 and a secondary flywheel 103 movable in rotation relative to each other about an axis of rotation X; the primary and secondary flywheels being in the relative angular rest position P0 in the absence of torque transmission,

- Two transmission members 130a and 130b carried by the secondary flywheel, each transmission member 130a, 130b having an elastic blade 117 arranged to flex to transmit a torque between these two flywheels 102 and 103, the bending of the elastic blade 117 being accompanied by a relative rotation between the primary and secondary flywheels 102 and 103, along the axis of rotation X, to dampen the rotation acyclisms between the primary flywheel and the secondary flywheel,

two bearing elements 124 carried by the primary flywheel, each support element being arranged to cooperate with each blade 1 17,

the elastic blade 117 having a cam surface 120 and the bearing element 124 comprising a cam follower 121 arranged to move on the cam surface during a relative rotation between the primary and secondary flywheels,

FIG. 7 illustrates the variation of the torque (C) in Nm transmitted as a function of the angle (A) in degrees, thanks to the curve C1 for the damper 1 of the invention and thanks to the curve C2 for a damper devoid of angular range of decreasing stiffness.

As can be seen in this Figure 7, the damper 1 of the invention has different damping ranges characterized by changes in angular stiffness distinct from one range to another. The angular stiffness is defined as the derivative of the torque / angle characteristic curve, the angle considered being the relative position of the first and second elements relative to the angular position of rest. For example, the stiffness is increasing over an angular range, when, in this range, the angular stiffness increases as the angle, relative to the angular position of rest, increases. In other words, in this case, the second derivative of the torque / angle characteristic curve is positive. Conversely, the stiffness is decreasing over an angular range, when, in this range, the angular stiffness decreases when the angle, relative to the angular position of rest, increases. In other words, in this second case, the second derivative of the torque / angle characteristic curve is negative.

As seen in FIG. 7, the damper is arranged so that the angular stiffness of the damper is decreasing in predetermined angular ranges of decreasing stiffness P2 and P5, moving away from a relative angular position of rest. PO.

In other words, on these angular ranges, the angular stiffness of the damper decreases away from the relative angular position of rest.

The predetermined angular range of decreasing stiffness is separated from the relative angular rest position by about 40 degrees.

In FIG. 7, it can be seen that the damper comprises, in the direct transmission direction, successively, moving away from the relative angular position of rest:

a first angular range of increasing stiffness (P1),

a first angular range of decreasing stiffness (P2),

a first angular range of zero stiffness or substantially equal to 0 (P3), a second angular range of increasing stiffness (P4),

a second angular range of decreasing stiffness (P5),

a second angular range of zero stiffness or substantially equal to 0 (P6).

To obtain the angular ranges of decreasing stiffness P2 and P5, the cam surface is arranged so that the torsional stiffness of the damper decreases over the predetermined angular range of decreasing stiffness P2 or P5. The predetermined angular range of decreasing stiffness P2 is separated from the relative angular rest position PO by an angular range of constant or increasing stiffness P1. The predetermined angular range of decreasing stiffness P2 is adjacent to the angular range of constant or increasing stiffness P1.

It can be seen that the two decreasing stiffness angular ranges P2 and P5 are separated from each other.

The second predetermined angular range of decreasing stiffness P5 is separated from the relative angular rest position PO by the second angular range of constant or increasing stiffness P4. The second predetermined angular range of decreasing stiffness P5 is adjacent to the second angular range of constant or increasing stiffness P4. The first predetermined angular range of decreasing stiffness P2 is between the two angular ranges of constant or increasing stiffness P1 and P4.

The damper has a maximum angular deflection position Pmax.

To do this, the stops 139 and 140, which are visible in Figures 5 and 6, are integral in rotation of the first and second elements and are arranged to come into contact with each other in the angular position of maximum travel . The first predetermined angular range of decreasing stiffness P2 is separated from the maximum angular deflection position Pmax by about 30 degrees.

FIG. 7 also shows that the damper is arranged so that the torsional stiffness of the damper is substantially equal to 0 for a predetermined relative angular position of zero stiffness β, remote from the relative angular position of rest PO, the torsional stiffness of the damper being different from 0 between the angular rest position PO and the position of zero stiffness β.

The predetermined relative angular position of zero stiffness β is a point of inflection of the curve C1. The torsional stiffness of the damper is substantially equal to 0 over two angular ranges of zero stiffness P3 and P6. The first angular range of zero stiffness P3 comprises said angular position of zero stiffness.

Thus, in these angular ranges of stiffness substantially equal to 0, the filtering properties of the damper are significantly improved.

The damper is arranged here so that the angular range of zero stiffness P3 is obtained for a torque equal to about 30% of the maximum engine torque.

The damper is arranged so that the second zero stiffness range P6 is obtained for a torque substantially equal to the maximum engine torque. The angular ranges of zero stiffness P3 and P6 are zones of constant torque.

The presence of angular ranges of zero stiffness or substantially equal to 0 improves the filter quality of the damper. The maximum angular deflection position Pmax is located on the angular range of zero stiffness P6.

The first predetermined angular range of decreasing stiffness P2 is between the first constant stiffness angular range P1 and the first zero stiffness angular range P3. Similarly, the second predetermined angular range of decreasing stiffness P5 is between the second constant stiffness angular range P4 and the second zero stiffness range P6.

Each angular range of zero stiffness P3 and P6 is adjacent to the predetermined angular range of decreasing stiffness P2 and P5.

The first zero stiffness range P3 is adjacent to the second angular range of constant or increasing stiffness P4.

The first zero stiffness range P3 is between the first predetermined angular range of decreasing stiffness P2 and the second constant or increasing angular range of stiffness P4.

In the angular range of zero stiffness, the torsional stiffness is substantially equal to 0, that is to say included here between 0 N. m / degree and 2 N. m / degree.

The angular range of zero stiffness P3 has an amplitude of about 5 degrees.

To obtain this damping curve, the cam surface is arranged so that the torsional stiffness of the damper is substantially equal to 0 in the angular range of zero stiffness.

The angular ranges of zero stiffness P3 and P6 are separated from each other.

Between the angular ranges of zero stiffness, the stiffness of the damper is non-zero, here greater than 20 N.m / degree, for an angular movement of about 55 degrees. The damper is arranged so that the first zero-stiffness angular range P3 is obtained for a torque equivalent to approximately 30% of the maximum engine torque, and the second zero-stiffness angular range P6 is obtained for a torque equal to the maximum engine torque. .

The damper is arranged such that the first angular range of zero stiffness is in an intermediate range of angular displacement of between 50% and 70% of the maximum range of angular deflection considered in the direction of direct rotation relative to the position relative angular rest.

The cam surface is arranged so that the damping curve of the damper comprises the two predetermined ranges of decreasing stiffness P2 and P5.

The cam surface is arranged so that the damping curve of the damper comprises the two predetermined ranges of zero stiffness P3 and P6.

The cam surface is arranged so that the damping curve of the damper comprises the two predetermined constant or increasing stiffness ranges P1 and P4. Figure 8 shows how the cam surface can be arranged to obtain the damping curve of Figure 7.

The cam surface has two areas of increasing stiffness S1 and S4 arranged so that the angular stiffness of the damper increases as the cam follower moves over these areas away from the relative rest position.

The two zones of increasing stiffness S1 and S4 are distant from each other. The cam surface has two zones of decreasing stiffness S2 and S5 arranged so that the angular stiffness of the damper decreases as the cam follower moves over these areas away from the relative rest position.

The two zones of decreasing stiffness S2 and S5 are distant from each other. The cam surface has two zones of zero stiffness S3 and S6 spaced from the area of the cam surface occupied by the cam follower in the relative angular position of rest, these two zones being arranged so that the angular stiffness of the cam damper is substantially equal to 0 when the cam follower moves on these two zones away from the relative position of rest.

The two areas of zero stiffness S3 and S6 are distant from each other.

FIG. 9 shows the behavior of the blade 1 17 under the action of the support element 124. When a driving motor torque is transmitted from the primary flywheel to the secondary flywheel (forward direction), the torque to be transmitted causes a relative movement between the primary flywheel and the secondary flywheel in a first direction D1. The roller 121 is then moved by an angle Θ with respect to the elastic blade 117. The displacement of the roller 121 on the cam surface 120 causes the elastic blade 117 to bend in an arrow f. To illustrate the flexion of the elastic blade 117, the elastic blade 117 is shown in solid lines in its angular rest position and in dashed lines, with the same references followed by a ', at an angular angular deflection Θ .

The bending force P depends in particular on the geometry of the elastic blade 117 and its material, in particular its transverse modulus of elasticity. The bending force P is decomposed into a radial component and a tangential component. The tangential component allows the transmission of the engine torque. In response, the elastic blade 117 exerts on the roller 121 a force reaction whose tangential component constitutes a restoring force which tends to bring the primary and secondary flywheels to their relative angular position of rest.

The damper is arranged so that, in the constant or increasing stiffness ranges, the support element 124 bends the blade 117 when the angular position of the primary and secondary flywheels deviates from the angular position of rest.

The cam surface is arranged so that the cam follower 121 exerts on the spring blade 117 a load P whose support, normal to the point of contact between the blade and the cam follower, is at a distance E (lever arm) the axis of rotation of the damper so that the torque C equal to the product of the load P and the distance E is not zero. The force support is called the line passing through the point of contact of the force and parallel to the vector of the force. Thanks to this condition, the angular range of zero stiffness of the damper does not behave like an angular position of rest.

In other words, in operation, that is to say outside the angular position of rest PO, including in the zero stiffness range, the cam surface is arranged so that the support element produces effort associated with a non-zero lever arm relative to the axis of rotation.

In other words, the cam surface is arranged so that the straight line along which the support member produces a bending force on the blade is spaced from the axis of rotation of the damper.

The radial displacement of the blade at the cam follower is a function of the angular deflection, the geometry of the cam surface of the blade y = F (x), the initial position and the diameter. These parameters are also involved in the calculation of the lever arm "E".

For a given angular deflection, the load "P" exerted by the bearing element on the blade to achieve a desired radial displacement "f" is given by the relation: "P * f * ³ * Elame * I _{lame ^}

L ³

With "E _blade " and "I _blade " the Young's modulus and the quadratic moment of the blade, and "L" the length between the contact "bearing element / blade" and the embedding of the blade.

In summary: the torque transmitted by the damper with a cam follower roller of given dimension depends on the angular displacement'O "with respect to the angular position of rest, the cam surface contact geometry of the blade'y = F (x) "(which also determines the radial displacement" f "and the lever arm" E "), and the geometry and material of the blade" E _blade "," Ii _soul "and" L ". For a given damper, the characteristic curve can be calculated

Torque / Angle considering these parameters. This gives the value of the torsional stiffness (evolution of the torque per degree of angular deflection) which varies according to these same parameters. Thus one can modify the torsional stiffness of the damper by modifying the geometry of the blade 1 17, and in particular of the cam surface 120.

It is thus possible to obtain the characteristic of a double damping flywheel blade whose torsional stiffness gradient is substantially zero in certain ranges of angular deflection.

To ensure that on the angular range of zero stiffness, the transmitted torque "C" is the same, it is necessary that the product of the load "P" normal applied by the support element on the blade and the arm of lever "E" is constant. The load considered here is the force necessary to bend, on a given contact point of the blade, this point of contact to the circular path followed by the support element, in particular the cam follower.

Likewise, the cam surface is arranged such that the values of the load (P) and the lever arm (E) are maintained greater than 0 in the zero stiffness range. Thus, the damper remains reversible outside its relative angular position of rest, that is to say that the cam follower does not remain blocked on the angular range of zero stiffness. Figure 10 shows a second embodiment of the invention.

With reference to FIG. 10, elements identical or similar to the elements of FIGS. 1 to 4, that is to say fulfilling the same function, bear the same reference numeral increased by 200.

This is a pre-damper 201 comprising:

a web 202 and a splined hub 203 rotatable relative to each other about an axis of rotation X; the sail and hub being in the relative angular position of rest in the absence of torque transmission,

a transmission member 230 carried by a splined hub and comprising two resilient blades 217a and 217b arranged to flex to transmit a rotational torque between the web 202 and the hub 203, the bending of the elastic blades 217a and 217b being accompanied by a rotation relative to the web 202 and the hub 203, along the axis of rotation X, to dampen the rotation acyclisms between the web and the hub,

a bearing element 224 carried by the web 202 and being arranged to cooperate with each of the blades 217a, 217b, via two cam surfaces 220a and 220b (not shown),

each blade 217a, 217b having a cam follower 221a, 221b (not shown) arranged to move on its own cam surface 220a, 220b during a relative rotation between the web 202 and the hub 203 .

The cam surface is thus carried here by the support element 224 and the cam follower 221 is carried by the elastic blade 217a, in particular on its free end zone 237. This type of damper is described in the application FR2938030.

The transmission member 230 comprises an annular fixing portion 218 rotatably connected to an output element, here the corrugated hub 203, and the two Flexible curved resilient blades 217a and 217b extend around the annular fixing portion 218 to a little less than 180 degrees.

The teachings and damping characteristics mentioned above can be applied to this damper.

When one of the two rotating elements begins to rotate relative to the other, in one direction or the other, the free end 237 of each elastic blade 217a slides on the cam surface 220a, which tends to bring this free end 237 of the fastening portion 218, and results in a bending of the elastic blade 217a.

The cam surface 220a successively comprises, in a given direction of rotation relative to the relative angular position of rest: a first zone of constant or increasing stiffness S1 ', a first zone of decreasing stiffness S2', a first zone of zero stiffness S3 ', a second zone of constant or increasing stiffness S4', a second zone of decreasing stiffness S5 ', and a second zone of zero stiffness S6'.

Thus we obtain the same type of damping curve as that of Figure 7, with an angular clearance which is here smaller.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

In particular, the blades of the damping means may be independent of one another or linked to one another by a central section. Similarly, it is possible to secure one of the blades of the damping means to one of the elements and the other of the blades of the damping means to the other of the elements.

Furthermore, the figures illustrate a torsion damper in the context of a double damping flywheel, but such a torsion damper can be installed on any suitable device. Thus, such torsion dampers can equip the friction clutch, in the case of a manual or robotic transmission, or locking clutches, also called "lock-up" clutches, equipping the hydraulic coupling devices, in the case of an automatic transmission. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

In the claims, any reference sign in parentheses could be construed as a limitation of the claim.

Claims

1. Torsional damper (101, 201) for a torque transmission device, in particular for an automobile, in particular for a clutch device, the damper being arranged so that the torsional stiffness of the damper decreases over an angular range predetermined decreasing stiffness (P2; P5) away from a relative angular rest position PO.

2. Damper according to the preceding claim comprising:

a first element (102; 202) and a second element (103; 203) rotatable relative to one another about an axis of rotation X; the first and second elements being in the relative angular position of rest (P0) in the absence of torque transmission,

a transmission member (130; 230) carried by one of the first and second elements, this transmission member comprising an elastic blade (117;

217a; 217b) arranged to flex to transmit a rotational torque between these two elements, the flexion of the elastic blade being accompanied by a relative rotation between the first and second elements, along the axis of rotation X, to dampen the rotating acyclisms between the first element and the second element,

a support element (124, 224) carried by the other of said first and second elements and arranged to cooperate with the blade,

one of the support element and the elastic blade has a cam surface (120; 220a) and the other of the support element and the elastic blade comprises a cam follower (121; 221 a ) arranged to move on the cam surface during relative rotation between the first and second members,

Shock absorber according to claim 2, characterized in that the cam surface (120; 220a) is arranged such that the torsional stiffness of the damper decreases over the predetermined angular range of decreasing stiffness (P2; P5).

4. Shock absorber according to one of the preceding claims, characterized in that the predetermined angular range of decreasing stiffness (P2; P5) is separated from the relative angular rest position by at least one angular range of constant or increasing stiffness (P1; P4).

5. Shock absorber according to one of the preceding claims, characterized in that the damper comprises several angular ranges of decreasing stiffness (P2, P5) separated from each other.

6. Shock absorber according to one of the preceding claims, characterized in that the damper is arranged so that the torsional stiffness of the damper is substantially equal to 0 for a predetermined relative angular position of zero stiffness (β), remote from the relative angular position of rest (PO), the torsional stiffness of the damper being different from 0 between the angular position of rest (PO) and the position of zero stiffness (β).

7. Shock absorber according to the preceding claim, characterized in that the torsional stiffness of the damper is substantially equal to 0 over at least one zero stiffness range (P3; P6) which comprises said angular position of zero stiffness.

8. Shock absorber according to the combination of claims 4 and 7, characterized in that the predetermined angular range of decreasing stiffness (P2; P5) is between said at least one constant or increasing stiffness range (P1; P3) and the angular range. zero stiffness (P3; P6).

9. Damper according to the combination of claims 2 and 7, characterized in that the cam surface is arranged so that the torsional stiffness of the damper is substantially equal to 0 in the angular range of zero stiffness (P3; P6 ).

10. Damper according to claim 7, characterized in that the damper comprises several angular ranges of zero stiffness (P3, P6) separated from each other.

11. Shock absorber according to one of claims 2, 3 or 9, characterized in that the cam surface (120; 220a) comprises at least one decreasing stiffness zone (S2; S5, S2 '; S5') arranged so that the angular stiffness of the damper decreases when the cam follower moves on this area away from the relative position of rest.

Shock absorber according to one of Claims 2, 3, 9 or 11, characterized in that the cam surface (120) is carried by the elastic blade (117) and the cam follower (121) is supported by the element support (124).

13. Shock absorber according to one of claims 2, 3, 9, 1 1, or 12, characterized in that the cam follower is formed by a roller (121) rotatably mounted on one of the first and second elements .

Shock absorber according to one of Claims 2, 3, 9, or 1 1, characterized in that the cam surface (220a) is carried by the support element (224) and the cam follower (221 a ) is carried by the elastic blade (217a), in particular on its free end zone (237).

15. torsion damper according to one of the preceding claims characterized in that the damper is intended to transmit a torque between a vehicle engine and a gearbox input shaft, the torque capable of being transmitted in the range predetermined angular decreasing stiffness is a positive torque traveling from the engine to the input shaft of the gearbox.