Vibration damper for a torque transmission device of a motor vehicle

Abstract

A vibration damper for a torque transmission device comprising a first element and a second element which are rotatable relative to each other around an axis of rotation X; and damping means for transmitting a torque and damping the rotational acyclisms between the first element and the second element. The damping means comprise an elastic blade mounted securely on the first element and provided with a cam surface; and the damper comprises a cam follower carried by the second element and arranged to cooperate with the cam surface. The cam surface is arranged such that, for an angular travel between the first element and the second element relative to an angular rest position, the cam follower exerts a flexion force on the elastic blade producing a reaction force able to return the first and second elements to the angular rest position.

Claims

1. A vibration damper (14) for a torque transmitting device of a motor vehicle having an internal combustion engine and a gearbox, the vibration damper comprising: a first element; and a second element, the first and second elements rotatable on a common axis of rotation relative to each other, one of the first and second elements being an input element adapted to be drivingly coupled to the internal combustion engine and another of the first and second elements being an output element adapted to be drivingly coupled to the gearbox; an elastic blade (4) having a free end (43) and a cam surface (6) preceding the free end (43), the elastic blade (4) mounted securely on the first element, the cam surface (6) formed by a radially outer surface of the elastic blade (4); a cam follower (5) carried by the second element and configured to cooperate with the cam surface (6) of the elastic blade (4), the cam follower (5) being a roller rotatably mounted on the second element (2) so as to be arranged radially outside the elastic blade (4); the cam surface (6) being arranged such that, for an angular travel between the first element (1) and the second element (2) relative to an angular rest position, the cam follower (6) exerts a flexion force on the elastic blade (4) producing a reaction force able to return the first element (1) and the second element (2) to the angular rest position.

2. The vibration damper as claimed in claim 1, wherein the cam surface (6) is formed at the free end (43) of the elastic blade (4).

3. The vibration damper as claimed in claim 2, wherein the elastic blade (4) comprises a portion (41) of radial orientation extended by a curved portion (42), and wherein the cam surface (6) is formed by a radially outer surface of the curved portion (42) of the elastic blade (4).

4. The vibration damper as claimed in claim 1, further comprising a second elastic blade (4) provided with a second cam surface (6) and mounted securely on the first element, and a second cam follower (5) arranged to cooperate with the second cam surface (6) of the second elastic blade (4).

5. The vibration damper as claimed in claim 4, wherein the first and second elastic blades (4) are symmetrical relative to the axis of rotation (X).

6. The vibration damper as claimed in claim 4, wherein the first and second elastic blades (4) are integral.

7. The vibration damper as in claim 4, wherein the first elastic blade and the second elastic blade have a common connecting portion arranged around the axis of rotation X and mounted securely on the first element (1).

8. The vibration damper as claimed in claim 1, wherein the roller (5) is mounted rotatably on the second element (2) via a bearing.

9. The vibration damper as claimed in claim 1, wherein the damper is configured to transmit a torque exceeding 200 N.Math.m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood, and other objectives, details, characteristics and advantages thereof will arise more clearly from the description below of several particular embodiments of the invention which are given solely for illustration and without limitation, with reference to the attached drawings.

(2) On the drawings:

(3) FIG. 1 is a perspective view of a vibration damper according to a first embodiment;

(4) FIG. 2 illustrates the flexion of the blade of the vibration damper according to FIG. 1 on an angular travel between the input and output elements in an direct direction;

(5) FIG. 3 illustrates the flexion of the blade on an angular travel in a reverse direction;

(6) FIG. 4 is a perspective view of a vibration damper according to a second embodiment;

(7) FIG. 5 illustrates in detail the damping means of the vibration damper in FIG. 4;

(8) FIGS. 6a, 6b, 6c illustrate examples of characteristic curves depicting the torque transmitted as a function of the angular travel, obtained by damping means according to the teaching of the invention;

(9) FIG. 7 is a schematic view of a transmission train of a motor vehicle showing the vibration damper between an internal combustion engine and a gearbox.

(10) FIG. 8 is a schematic view of a hydraulic coupling device including the vibration damper according to the present invention in a motor vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(11) A torsional vibration damper 14 shown on FIG. 1 is intended to be integrated in a transmission element of the transmission train of a motor vehicle. This transmission element may for example be an engine flywheel equipped with the torsional vibration damper 14, such as a dual mass flywheel, a lock-up clutch of a hydraulic coupling device, or a clutch friction plate. It is also noted that in the case of a clutch friction plate, the torsional vibration damper 14 according to the invention may be formed as a main damper and/or as a pre-damper.

(12) The torsional vibration damper 14 comprises an input element 1 and an output element 2 which are arranged, in the transmission train, on the side of an internal combustion engine 10 and on the side of a gearbox 12, respectively, as illustrated in FIG. 7. For example, when the vibration damper according to the invention is integrated in a dual mass flywheel, the input element 1 may comprise or be carried by a first inertia flywheel intended to be fixed to the end of a drive shaft, such as a crankshaft of an internal combustion engine 10, while the output element 2 comprises or is carried by a second inertia flywheel, generally forming a reaction plate of a clutch for connection to a driven shaft, such as an input shaft of the gearbox 12. FIG. 8 shows the vibration damper 14 of the present invention employed in a hydraulic coupling device 20 for a transmission train of a motor vehicle 23 between the internal combustion engine 10 and the gearbox 12.

(13) The input element 1 and output element 2 are rotatable about a common axis of rotation X. The input element and output element 2 are guided in rotation relative to each other by means of a bearing such as a roller bearing 3.

(14) The input element 1 and output element 2 are connected in rotation by damping means. The damping means are able to transmit a torque exceeding 200 N.Math.m, preferably exceeding 300 N.Math.m, (see FIG. 6a-6c) driving the input element 1 towards the output element 2 (direct direction) and a resistant torque of the output element 2 towards the input element 1 (reverse direction). Secondly, the damping means develop an elastic return torque tending to return the input element 1 and the output element 2 to a relative angular rest position.

(15) The damping means comprise an elastic blade 4. The elastic blade 4 has a free distal end 43 and a connecting portion 44 spaced from the free distal end 43. The connecting portion 44 of the elastic blade 4 is securely (i.e., non-moveably or fixedly) mounted in rotation on the input element 1. At one free end 43, the elastic blade 4 has a cam surface 6 preceding (or anterior to) the free distal end 43 of the elastic blade 4 and arranged to cooperate with a cam follower: a roller 5 mounted on the output element 2. The elastic blade 4 is designed so that it can tolerate high stresses which may amount to 1500 MPa. The elastic blade 4 is for example made of 51CV4 steel which has undergone dedicated heat treatment such as quenching followed by annealing.

(16) The connecting portion 44 of the elastic blade 4 is fixed (i.e., non-moveably coupled) to the input element 1 close to the axis of rotation X. The elastic blade 4 further comprises an arm portion 41 extending substantially radially outwardly from the connecting portion 44 on the input element 1. The arm portion 41 is extended via an elbow by a curved portion 42 adjacent to the connecting portion 44. The curved portion 42 extends substantially circumferentially. As illustrated in FIGS. 1-5, a radially outer surface of the curved portion 42 of the elastic blade 4 forms the cam surface 6, which is anterior to the free distal end 43 of the elastic blade 4, i.e., is disposed between the free end 43 and the arm portion 41 of the elastic blade 4. The radius of curvature of the curved portion 42, and the distance between the elbow extending between the portion 41 and the curved portion 42, are determined as a function of the desired stiffness of the elastic blade 4. The elastic blade 4 may, as required, be produced from one piece or be composed from a plurality of blades axially fixed to each other.

(17) The roller 5 is mounted rotatably on the output element 2 around the axis of rotation 7. The roller 5 is held resting against the cam surface 6 and is arranged to roll against said cam surface 6 on a relative movement between the input element 1 and the output element 2. The roller 5 is arranged radially outside the cam surface 6 so as to hold the elastic blade 4 radially when it is subjected to centrifugal force. In order to reduce the parasitic friction liable to affect the damping function, the roller 5 is mounted in rotation on the output element 2 by means of a roller bearing. For example, the roller bearing may be a ball bearing or a roller bearing. In one embodiment, the roller 5 has an antifriction coating.

(18) FIG. 1 illustrates the input element 1 and the output element 2 in a relative angular rest position.

(19) The cam surface 6 is arranged such that, for an angular travel between the input element and the output element to either side of this relative angular rest position, the roller 5 moves on the cam surface 6 and by doing so, exerts a flexion force on the elastic blade 4. In reaction, the cam surface 6 exerts a return force on the roller 5 which tries to bring the input element 1 and output element 2 back to their relative angular rest position.

(20) The function of the vibration damper will now be explained in relation to FIGS. 2 and 3.

(21) When a driving motor torque is transmitted from the input element 1 to the output element 2 (direct direction), the torque to be transmitted causes a relative travel between the input element 1 and the output element 2 in a first direction (see FIG. 2). The roller 5 is then moved through an angle relative to the elastic blade 4. The movement of the roller 5 on the cam surface 6 causes a flexion of the elastic blade 4 according to arrow A. To illustrate the flexion of the blade 4, the blade 4 is shown in solid lines in its angular rest position and in dotted lines in its angular travel.

(22) The flexion force P depends in particular on the geometry of the blade and its material, in particular its modulus of transverse elasticity. The flexion force P breaks down into a radial component Pr and a tangential component Pt. The tangential component Pt allows transmission of the engine torque. In reaction, the elastic blade 4 exerts a reaction force on the roller 5, the tangential component of which constitutes a return force which tries to bring the input element 1 and output element 2 back to their relative angular rest position.

(23) When a resistant torque is transmitted from the output element 2 to the input element 2 (reverse direction), the torque to be transmitted causes a relative travel between the input element 1 and the output element 2 in a second opposite direction (see FIG. 3). The roller 5 is then moved through an angle relative to the elastic blade 4. In this case, the tangential component Pt of the flexion force has an opposite direction to the tangential component of the flexion force illustrated on FIG. 2. Similarly, the elastic blade exerts a reaction force in the opposite direction to that illustrated on FIG. 2, so as to bring the input element 1 and output element 2 back to their relative angular rest position.

(24) The torsional vibrations and the torque irregularities produced by the internal combustion engine are transmitted by the drive shaft to the input element 1, and also generate relative rotations between the input element 1 and output element 2. These vibrations and irregularities are damped by the flexion of the elastic blade 4.

(25) FIGS. 6a, 6b and 6c illustrate characteristic curves of the vibration dampers produced in accordance with the teaching of the invention. FIG. 6a shows the characteristic curve of a pre-damper intended to be fitted to a clutch friction plate, while FIGS. 6b and 6c represent characteristic curves of main dampers intended to be fitted to clutch friction plates. These characteristic curves represent the torque transmitted, expressed in Nm, as a function of the angular travel, expressed in degrees. The relative travel between the input element 1 and output element 2 in the direct direction is shown in dotted lines, whereas the travel in the reverse direction is shown in solid lines. It is noted that a vibration damper according to the invention in particular allows characteristic damping curves of which the gradient varies progressively without discontinuity.

(26) Advantageously, the cam surface 6 and the elastic blade 4 are arranged such that the characteristic function of the torque transmitted as a function of the angular travel is a monotonous function.

(27) Also, the cam surface 6 and the elastic blade 4 are arranged such that the transmissible torque is greater than the maximum engine torque when the roller 5 reaches the two ends of the cam track 4.

(28) For certain applications, the cam surface 6 and the elastic blade 4 may be arranged such that the characteristics of the torque transmitted as a function of the angular travel in the reverse direction and in the direct direction are symmetrical relative to the angular rest position.

(29) FIGS. 4 and 5 show a second embodiment of the invention wherein the vibration damper comprises two elastic blades 4. The first and the second elastic blades 4 are formed from a single piece and are symmetrical relative to the axis of rotation X. Moreover, the first elastic blade and the second elastic blade (4) have a common connecting portion 45 arranged around the axis of rotation X and mounted securely on the first element 1. Each of the blades 4 has a cam surface 6 cooperating with a cam follower 5. Such a structure firstly allows a balanced vibration damper, and secondly may be advantageous when the engine torque to be transmitted is high.

(30) In one embodiment (not illustrated), a torque transmission element according to the invention is fitted with two dampers as described above, arranged in series.

(31) In another embodiment (not illustrated), a torque transmission element is fitted with two dampers as described above, arranged in parallel.

(32) Although the invention has been described in connection with several particular embodiments, it is evident that it is in no way limited to this and comprises all technical equivalents of the means described and their combinations where these fall within the scope of the invention. In particular, it is evident that although, in the embodiment described above, the elastic blade is mounted securely on the input element and the cam follower is mounted on the output element, the elastic blade may equally well be mounted on the output element while the cam follower is mounted on the input element.