FR3037113A1 - TORSION DAMPER - Google Patents

Abstract

A torsion damper for a torque transmission device, particularly for a motor vehicle, in particular for a clutch device, the damper being arranged such that the torsional stiffness of the damper decreases over a predetermined angular range of decreasing stiffness (P2; P5) away from a relative angular position of repose (PO).

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to a torsion damper intended to equip 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 Twist dampers are known whose input and output elements are coupled in rotation by damping means for transmitting a torque and damping the 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. We also know the damper document FR2938030.

OBJECT OF THE INVENTION One aspect of the invention proceeds from the idea of solving the drawbacks of the prior art by proposing an elastic blade torsion damper which is particularly effective and in which the performances of the damping are 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 in such a way that the torsional stiffness of the damper decreases over an angular range. predetermined 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 stiffness over certain angular operating ranges allows the desired damping curve to be customized to suit the specific characteristics of the engine. According to other advantageous embodiments, such a torsion damper may have one or more of the following characteristics: Preferably, the damper comprises: a first element and a second element movable in rotation with respect to the other around 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 for transmitting a torque between these two elements, the bending 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 rotation acyclisms between the first element and the second element, a bearing 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 has a cam surface and the other of the support member and the resilient blade have a cam follower arranged to move on the cam surface during relative rotation between the first and second members, reference, the predetermined angular range of decreasing stiffness 15 is 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. Preferably, the cam surface is 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. Advantageously, the angular stiffness of the damper is a function of the profile of the cam surface. Thus a modification of the profile of the cam surface 25 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. Preferably, the predetermined angular range of decreasing stiffness 30 is separated from the relative angular rest position by at least one angular range of constant or increasing stiffness. Preferably, the predetermined angular range of decreasing stiffness is adjacent to the angular range of constant or increasing stiffness.

Preferably, the predetermined angular range of decreasing stiffness is between two angular ranges of constant or increasing stiffness. Preferably, the damper has several decreasing angular ranges of stiffness. Advantageously, two angular ranges of decreasing stiffness are provided on the same side of the relative angular position of rest.

Advantageously, these two decreasing stiffness ranges are separated from each other. Advantageously, these two decreasing stiffness ranges are spaced apart from the relative angular position of rest. Preferably, the damper comprises a maximum angular displacement position. Preferably, the damper comprises stops arranged to come into contact with each other in the angular position of maximum displacement.

Preferably, these stops are integral in rotation with the first and second elements. Preferably, the predetermined angular range of decreasing stiffness is separated from the maximum angular deflection position by at least 25 degrees, in particular by at least 20 degrees, for example by at least 30 degrees. Preferably, 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, 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. The predetermined relative angular position of zero stiffness is a point of inflection of the damping curve of the damper.

Preferably, the torsional stiffness of the damper is substantially equal to 0 over at least one angular range of zero stiffness which comprises said angular position of zero stiffness.

Preferably, the damper has several angular ranges of zero stiffness separated from each other. In other words, the torque / angle torque curve of the damper comprises at least a substantially constant torque zone 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 15 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 so 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, for example 30% of the maximum engine torque.

Preferably, the damper is arranged so that an angular range of zero stiffness is obtained for a torque substantially equal to the maximum engine torque. Preferably, the maximum angular deflection position is on an angular range of zero stiffness. Preferably, the predetermined angular range of decreasing stiffness is between said at least one constant or increasing stiffness range and the zero stiffness angular range.

Preferably, the zero stiffness range is adjacent to the predetermined angular range of decreasing stiffness. Preferably, the zero stiffness range is adjacent to the predetermined angular range of decreasing stiffness on the opposite side to the relative angular position of rest. Preferably, the zero stiffness range is adjacent to said at least one angular range of constant or increasing stiffness.

Preferably, the zero stiffness range is between the predetermined angular range of decreasing stiffness and said at least one angular range of constant or increasing stiffness.

Advantageously, the torsional stiffness is between 0 Nm / degree and 3 Nm / degree, in particular between 0 Nm / degree and 2 Nm / degree, in particular between 0 Nm / degree and 1 Nm / degree, in particular between 0 Nm / 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. Preferably, 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. Preferably, the damper comprises several angular ranges of zero stiffness between which the stiffness of the damper is greater than 5 Nm / degree, especially greater than 10 Nm / degree. If desired, the damper comprises an angular range of zero stiffness for a torque of 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 torque.

Preferably, the damper is arranged such that the angular range of zero stiffness 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 displacement of between 30% and 70% of the maximum range of angular displacement considered in a given direction of rotation. relative to the relative angular rest position, in particular between 40% and 60% of this range. Preferably, the resilient blade and the bearing member are 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 blade. support member adapted to recall the first and second elements to said angular position of rest. Advantageously, the damper is arranged such that, in the regions of constant or increasing stiffness, the support element bends the blade when the angular position of the first and second elements deviates from the angular position 20 of rest. Advantageously, the bending of the blade is accompanied by a relative rotation between the first and second elements.

Advantageously, the elastic blade has 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. Advantageously, the cam surface is arranged so that the damper has at least one predetermined range of decreasing stiffness. Advantageously, the cam surface is arranged so that the damper comprises at least a predetermined range of zero stiffness.

Advantageously, the cam surface is arranged so that the damper comprises at least a predetermined range of constant or increasing stiffness.

Preferably, the cam surface has at least one region of increasing stiffness arranged so that the angular stiffness of the damper increases as the cam follower moves over that area away from the relative rest position.

Preferably, the cam surface has two zones of increasing stiffness spaced apart from each other. Preferably, the cam surface has at least one decreasing stiffness zone arranged so that the angular stiffness of the damper decreases as the cam follower moves over this area away from the relative rest position. Preferably, the cam surface has two zones of decreasing stiffness distant from each other.

Preferably, the cam surface has as many zones of decreasing stiffness as the damper has angular ranges of decreasing stiffness.

Advantageously, the cam surface comprises 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 the cam. rest.

Advantageously, the cam surface has two zones of zero stiffness spaced apart from each other. Advantageously, the cam surface is arranged so that the bearing element exerts on the spring blade a load whose support, normal at the point of contact between the blade and the support element, is separated from the spring. 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 straight line passing through the point of contact of the force and parallel to the vector of the force. Preferably, the cam surface is carried by the resilient blade and the cam follower is carried by the bearing member. Thus, one can modify the stiffness of the damping by modifying only the blade of the shock absorber.

Advantageously, the cam follower is formed by a roller rotatably mounted on itself on one of the first and second elements. If desired, the cam follower is rotationally secured to one of the first and second members 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, in particular by rolling and by 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.

Advantageously, the cam surface is 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. the damper of 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 35 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 15 considered here is the force required to bend, at 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 has a radially free, free distal end 30 such that the radial distance between the axis of rotation of said free distal end varies as a function of the angular displacement between the first and second members. The torsion damper may furthermore have one or more of the following features: 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. if necessary, the transmission member with its blades are formed in one piece on the same piece, this piece itself being 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 region is radially movable such that the radial distance between the axis of rotation of said free distal end varies as a function of the angular displacement between the first and second members. the angular sector along which the two flexible blade regions are radially offset from one another extends over at least 1 °, for example over at least 5 °, preferably at least 10 °, especially 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 attachment portion remains fixed, that is, it does not flex when the first and second members rotate relative to each other. the resilient blade has an inner and outer strand connected by a bend, the inner strand developing from the attachment portion to the elbow and the outer strand developing circumferentially from the bend to the free distal end, the inner strand having one of the two radially and radially offset blade regions of the transmission member and the outer strand having the other of the two radially and radially offset blade regions of 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 arranged 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 20 corresponding to a maximum angular displacement between the first element and the second element, the shock absorber comprises two elastically deformable blades mounted integral with one of said first and second elements and the damper comprises two support elements carried by the other of said first and second elements, the support elements being respectively arranged to cooperate with the one and the other of the two elastically deformable blades, and each blade has two flexible blade regions radially offset from one another, 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 has 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 outer surface of the blade other 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 the at least one bearing member has 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 so that the torsional stiffness of the damper is substantially equal to 0 over a predetermined angular range of zero stiffness. Preferably, this 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 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 rotation acyclisms between the first element and the second element; element, a bearing 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 has a cam surface and the other of the support member and the resilient blade includes a cam follower arranged to move on the cam surface upon relative rotation between the first and second members, This angular range of zero stiffness is separated from the relative angular position of rest by a non-zero, constant or increasing angular range of stiffness. 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 large 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, features and advantages thereof will become more apparent in the following description of several particular embodiments of the invention, given solely for illustrative purposes and not limiting, 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 shown, in a transparent manner, so as to visualize the transmission organ. Figure 2 is a sectional view of the double damping flywheel of Figure 1, according 11-ll.

FIG. 3 is a perspective view of the double damping flywheel of FIG. 1. FIG. 4 is a perspective view of the double damping flywheel of FIGS. 1 to 3, in which the secondary flywheel is shown, partially broken away, and disassembling the primary flywheel.

FIG. 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 member and the second member. 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. Fig. 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 deflection 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 torsion damper elements determining the "axial" orientation and from the inside to the outside in the direction of rotation. away from said axis, the "circumferential" orientation is directed orthogonally to the rotational axis 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 element. external located radially periphery.

First of all, reference is made to FIGS. 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 primary flywheels and secondary. 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 bearing with ball bearings 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 10 flywheels primary 2 and secondary 3 are intended to be mounted movable about an axis of rotation X and are further rotatable relative to each other about said axis X. The steering wheel 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 fastening screw holes 8 for securing the primary flywheel 2 to the crankshaft of the engine and, on the other hand, orifices 9 for the fastening of a transmission member on the primary flywheel 2. The primary flywheel 2 carries, on its outer periphery, a ring gear 10 for driving in rotation the primary flywheel 2, to the using a starter. The hub 5 of the primary flywheel has a shoulder 11 serving to support an inner ring of the rolling bearing 4 and which retains said inner ring 25 towards the engine. 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 has a flat annular surface 13, turned on the opposite side to the primary flywheel 2, forming a bearing surface for a friction lining 30 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-a-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 and secondary flywheels 3 are coupled in rotation by a transmission member 30. In the embodiment shown in FIGS. 1 to 4, this damping means comprises two resilient blades 17a, 17b mounted integral with the rotation of the steering wheel. 2. To do this, the elastic blades 17a, 17b are carried by an annular body 18 provided with orifices for the passage of the fastening rivets 9 to the primary flywheel 2. The annular body 18 further comprises orifices 19 for the passage of screws 8 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 resilient blades 17a, 17b have a cam surface 20. The secondary flywheel 3 has two support members 24 each having 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 optionally 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 25 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 movement The rollers 21 are disposed radially outwardly from their respective cam surfaces 20 so as to radially maintain the resilient 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 rotatably mounted 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 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 it 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 10 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 which are produced by the internal combustion engine are transmitted by the crank shaft to the primary flywheel 2 and generate relative rotations between the primary and secondary flywheels 3. These vibrations and irregularities are damped by the bending of the elastic blades 17a and 17b of the transmission member. Figure 5 shows a schematic view of a torsion damper 20 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 FIGS. , 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 117.

Each transmission member 130a, 130b has a fixing portion 118 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 blade 117. The primary flywheel 102 comprises a support element 124 which comprises a cam follower formed by a roller 121 movable in rotation about a rod 122 fixed on the primary flywheel 102. The roller is therefore rotatably mounted on itself on the primary flywheel 102. The cam follower 121 is integral in rotation with the primary flywheel 102 with respect 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, rolling on the elastic blade carried 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 flywheel The attachment portion 118 of the transmission members 130a, 130b develops circumferentially around the outer ring 127. The inner ring 128 of the ball bearing 104 is carried by the hub 105 of the primary flywheel 102. each fixing member 118 of each transmission member 130a, 130b is fixed to the secondary flywheel 103 by three rivets 129. The attachment portion 118 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 117 has an inner 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 118 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 part of the stresses 10 experienced by the elastic blade 117 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 a general hairpin shape, one leg of which is formed by the outer strand 134 and the other leg is formed together by the attachment portion 118 and the inner strand 132. In the end, the blade 117 has two flexible blade regions radially offset from one another and separated by a void space. The outer strand 134 develops circumferentially from the bend 133 to the free end 137 of the resilient blade 117. The outer strand 134 develops over a circumference of at least 45 ° and up to 180 ° to the bent state of the resilient 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 with a radius of curvature determined according to the desired stiffness of the resilient blade 117. This cam surface 120 may have different radii of curvature depending on the desired point stiffnesses, in order to allow variations. slope of the characteristic curve of the torsion damper, representing the torque transmitted as a function of the angular displacement.

The transmission members 130a and 130b and their elastic blade 117 shown schematically in FIG. 5 are symmetrical with respect to the axis of rotation X. FIG. 6 shows that when a resisting torque is transmitted from the flywheel 5 primary 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 at an angle Q with respect to the elastic blades 117. The displacement of the rollers 121 on the cam surfaces 120 causes the resilient blades 117 to bend.

The flexion of the resilient blades 117 brings about the approximation, on the one hand, 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. 117 of one of the transmission members 130a, 130b with the elbow 133 of the blade 117 of the other transmission members 130a, 130b. Preferably, these 15 approximations must not cause contacts between the outer strand 134 and the attachment portion 118, such contacts generating disturbances in the damping of acyclisms and vibrations. To avoid such contacts, the circumferential length of the fixing portion 118 is limited so that, in the rest position shown in FIG. 5, the fixing portion 118 does not develop circumferentially beyond the formed axis. by the alignment between the cam follower 121 and the axis of rotation X. Preferably, an end 138 of the attachment portion 118 opposite the flexible portion including the blade 117 is located between the corresponding cam follower 121 and the cam follower 121. X axis of rotation during a maximum angular deflection in retro direction between the primary flywheel 102 and the secondary flywheel 103, as represented by the axis 143. Such maximum angular movement is for example limited by a stop end of 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 30 e external strand 134 of an elastic blade 117 and the attachment portion 118 of the transmission member 130, the thickness of the fixing portion 118 is reduced relative to the thickness of the elastic blade 117, and more particularly at least the thickness of the end 138 of the attachment portion 118 is reduced with respect to the thickness of the flexible portion. To avoid contact between the free end 137 of the blade 117 of one of the transmission members 130a and the bend 133 of the blade 117 of the other of the transmission members 130b, the free end 137 of the blades 117 comprises 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 10 117 or loss of cooperation between the cam followers 121 and the cam surfaces 120. The resilient blades 117 and the support members, here the cam followers 121, are arranged such that in operation each follower Cam 121 exerts a bending force on each blade 117 causing them to bend, and producing a reaction force of the blade on the cam follower to bias the primary and secondary flywheels 102 and 103 toward said angular position. e of rest. The damper is arranged so that the support members 121 bend the blades 117 when the angular position of the primary and secondary flywheels departs 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 resilient blade 117 has a free end region 137 and the damper is arranged such that this free end 137 moves with a radial component when the backing member 121 bends the resilient blade 117.

This double damping flywheel thus comprises: 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 relative angular rest position PO 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 flexion 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, for damping rotation acyclisms between the primary flywheel and the secondary flywheel, two support elements 124 carried by the primary flywheel, each support element being arranged to cooperate with each blade 117, the elastic blade 117 having a cam surface; 120 and the support element 124 having a cam follower 121 arranged to move on the cam surface during a relative rotation between the primary flywheels e 15 and secondary, Figure 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 the angular stiffness distinct from one range to another. The angular stiffness is defined as the derivative of the torque / angle characteristic curve, the angle being the relative position of the first and second members with respect to the angular position of repose. 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 as the angle, relative to the angular rest position, increases. In other words, in this second case, the second derivative of the torque / angle characteristic curve is negative.

As can be 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. rest P0.

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 position of rest by about 40 degrees. In FIG. 7, it can be seen that, in the direction of direct transmission, the damper successively moves away from the relative angular position of rest: a first angular range of increasing stiffness (PI), 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 stiffness zero or substantially equal to 0 (P6). To obtain the decreasing stiffness angular ranges P2 and P5, the cam surface is arranged such 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. .

It will be seen that the two decreasing angular ranges of decreasing stiffness 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 constant or increasing angular range 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 displacement position of 15 Pmax. To this end, the stops 139 and 140, which are visible in FIGS. 5 and 6, are integral in rotation with the first and second elements and are arranged to come into contact with one another in the angular displacement position. maximum. 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 in such a way that the torsional stiffness of the damper is substantially equal to 0 for a predetermined relative angular position of zero stiffness [3, distant from the relative angular position of rest P0 , the torsional stiffness of the damper being different from 0 between the angular rest position PO and the zero stiffness position R. The predetermined relative angular position of zero stiffness [3 is an inflection point 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 areas of constant torque. The presence of angular ranges of zero stiffness or substantially equal to 20 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 decreasing stiffness range P2 is between the first constant stiffness angular range P1 and the first zero stiffness angular range P3. Similarly, the second predetermined angular decreasing stiffness range P5 is between the second angular range of constant stiffness 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 P4. In the angular range of zero stiffness, the torsional stiffness is substantially equal to 0, that is to say between here 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 in such a way 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 Nm / degree, for an angular displacement 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 engine torque. maximum. The damper is arranged so that the first angular range of zero stiffness is within an intermediate range of angular displacement of between 50% and 70% of the maximum angular displacement range considered in the direct direction of rotation relative to the relative angular position of 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 such that the damper curve of the damper has the two predetermined zero stiffness ranges P3 and P6. The cam surface is arranged such that the damping curve of the damper comprises the two predetermined constant or increasing stiffness ranges P1 and P4. FIG. 8 shows how the cam surface can be arranged to obtain the damping curve of FIG. 7. The cam surface has two zones of increasing stiffness S1 and S4 arranged so that the angular stiffness of the damper increases when the cam follower moves on these areas away from the relative position of rest. 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 areas of decreasing stiffness S2 and S5 are spaced from each other. The cam surface has two areas 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, both areas being arranged so that the stiffness angular of the 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 117 under the action of the bearing 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 10 between the primary flywheel and the secondary flywheel in a first direction D1. The roller 121 is then moved at an angle θ relative to the elastic blade 117. The displacement of the roller 121 on the cam surface 120 causes a flexion of the elastic blade 117 along an arrow f. To illustrate the flexion of the elastic blade 117, the elastic blade 117 is shown in solid lines in its angular position of rest and in dashed lines, with the same references followed by a r, during an angular deflection of angle 0. 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 reaction force whose tangential component constitutes a restoring force which tends to bring the primary and secondary flywheels towards their relative angular position of rest.

The damper is arranged such that, in the regions of constant or increasing stiffness, 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 at 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 act as an angular position of rest. In other words, in operation, that is to say outside the angular position of rest P0, including in the zero stiffness range, the cam surface is arranged so that the support element produces in 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 "f" of the blade at the cam followers is a function of the angular displacement "0", the cam surface geometry of the blade "y = F (x)", the initial position and the diameter of the cam follower bearing. 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: f * 3 * Elame * 'blade' L3 With "Eiame" and "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 "0" relative 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" Eiame "," blade "and" L ". For a given damper, it is possible to calculate the Torque / Angle characteristic curve by considering these parameters, thus obtaining the value of the torsional stiffness (evolution of the torque per degree of angular deflection) which varies according to these same parameters. .

Thus, the torsional stiffness of the damper can be modified by modifying the geometry of the blade 117, and in particular of the cam surface 120. It is thus possible to obtain the characteristic of a double damper flywheel blade whose Torsional stiffness gradient is substantially zero in certain ranges of angular deflection. To ensure that in the angular range of zero stiffness the transmitted torque "C" is the same, the product of the normal "P" load applied by the bearing member to the blade and the arm 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 so that the values of the load (P) and the lever arm (E) 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 stuck 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 number increased by 200. This is a pre-damper 201 comprising: a sail 202 and a splined hub 203 movable in rotation 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 hub spline and having two resilient blades 217a and 217b arranged to flex to transmit a torque between the veil 202 and the hub 203, the bending of the elastic blades 217a and 217b being accompanied by a relative rotation between 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 upon relative rotation between the web 202 and the hub 203. The cam surface is thus moved to ci 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 member, here the splined hub 203, and the two curved flexible resilient blades 217a and 217b extend around the annular fixing portion 218 on 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 members begins to rotate relative to each other, in either direction, the free end 237 of each resilient blade 217a slides on the cam surface 220a, which tends to bring this free end 237 closer to the fastening portion 218, and results in a flexion of the elastic blade 217a.

The cam surface 220a comprises successively, 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 quite obvious that it is in no way limited thereto and that it comprises all the technical equivalents of the means described as well as their combinations if these These 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. Likewise, 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. Moreover, 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 clutch friction, in the case of a manual or robotic transmission, or the 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 forth 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 can not be interpreted as a limitation of the claim.

Claims (17)

REVENDICATIONS1. Torsional damper (101, 201) for a torque transmission device, in particular for a motor vehicle, in particular 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) away from a relative angular position of rest P0. 2. Shock absorber according to the preceding claim comprising: a first element (102; 202) and a second element (103; 203) 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 (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 a elastic blade (117; 217a; 217b) arranged to flex to transmit a torque between these two elements, the bending 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 rotation 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 element d and the resilient blade has a cam surface (120; 220a) and the other of the support member and the resilient blade includes a cam follower (121; 221a) arranged to move on the surface cam during a burst relative relationship between the first and second elements, 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). 3037113 36 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 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. 10 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 ([3), remote the relative angular position of rest (P0), the torsional stiffness of the damper being different from 0 between the angular position of rest (P0) and the position of zero stiffness ([3). 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 angular range of zero stiffness (P3; P6) which comprises said angular position of zero stiffness. 8. Damper 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 range angular zero stiffness (P3; P6). Shock absorber according to the combination of claims 2 and 7, characterized in that the cam surface is arranged in such a way that the torsional stiffness of the damper is substantially equal to 0 in the angular range of zero stiffness (P3; P6). 10. Shock absorber according to claim 7, characterized in that the damper comprises several angular ranges of zero stiffness (P3; P6) 35 separated from each other. 3037113 37 Shock absorber according to Claim 2, characterized in that the elastic blade (117; 217a; 217b) and the support element (124,224) are arranged in such a way that, in operation, the bearing element exerts a bending force on the elastic blade and producing in reaction a reaction force of the blade on the bearing element adapted to return the first and second elements to said angular position of rest. Damper according to Claim 2, characterized in that the cam surface (120; 220a) comprises at least one decreasing stiffness area (S2; S5, S2 '; S5') arranged so that the angular stiffness of the the damper decreases when the cam follower moves over this area away from the relative rest position. 15 13. Damper according to claim 2, characterized in that the cam surface (120) is carried by the resilient blade (117) and the cam follower (121) is carried by the support member (124). 14. Shock absorber according to claim 2, characterized in that the cam follower 20 is formed by a roller (121) rotatably mounted on one of the first and second elements. 15. Damper according to claim 2, characterized in that the cam surface is arranged so that the cam follower exerts on the elastic blade 25 a load (P) whose support, normal to the point of contact between the blade and the blade. cam follower, is at distance (E) from 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. A shock absorber according to claim 2, characterized in that the cam surface (220a) is carried by the support member (224) and the cam follower (221a) is carried by the resilient blade (217a), especially on its free end zone (237). 3037113 38 17. Damper according to claim 2, characterized in that said at least one blade has a free distal end (137, 237) radially movable so that the radial distance separating the axis of rotation of said free distal end varies according to angular deflection between the first and second elements.