Angular damping device fitted with friction means variable according to rotation speed

An angular damping device (10) for a motor vehicle temporary wet coupling system comprises two radial guide washers (24) which are positioned axially one on each side of a web (12),at least two elastic members (38) with circumferential action which are circumferentially interposed in series between the web (12) and the guide washers (24), and a phase member (42) which comprises at least one radial phase lug (48). The phase member (42) further comprises two friction pads which can parted axially against each of the guide washers (24). Each of the friction pads comprises a retaining face (54) for retaining an elastic member (38) against the action of centrifugal force. The elastic member (38) is partially inserted between the two retaining faces (54)in the manner of a wedge.

This application is a national stage application of International Application No. PCT/FR2011/051188 filed May 25, 2011, which claims priority to French Patent Application No. 10/54239 filed Jun. 1, 2010, of which the disclosures are incorporated herein by reference and to which priority is claimed.

FIELD OF THE INVENTION

The present invention relates to an angular damping device for a motor vehicle temporary wet coupling system.

The present invention more particularly relates to an angular damping device between a first coaxial shaft and a second coaxial shaft in a motor vehicle temporary wet coupling system which comprises:a radial web which is intended to be rotationally coupled to the first shaft;two radial guide washers which are positioned axially one on each side of the web and which are rotationally coupled to the second shaft;at least two elastic members with circumferential action which are circumferentially interposed in series between the web and the guide washers;a phase member which comprises at least one radial phase lug circumferentially interposed between two elastic members in series, the phase member comprising at least two friction pads which can be axially pressed towards each of the two radial guide washers by application of an axial clamping force so that they are axially clamped against each of the guide washers.

BACKGROUND OF THE INVENTION

Such a damping device is generally used in automatic clutch systems, of the torque converter type, to transmit torque between a turbine shaft and a friction locking clutch.

Such a device can also be used in a so-called “wet” friction clutch.

Such a damping device in particular is used to filter the vibrations coming from the engine, in particular due to elastic members and associated so-called “hysteresis” friction pads.

The damping devices of this type are very effective in attenuating vibrations in certain given frequency ranges. However, a resonance phenomenon has been observed whose frequency and level vary according to the rotation speed of the damping device on the one hand and the transmitted torque on the other hand.

SUMMARY OF THE INVENTION

The object of the present invention is to mitigate this drawback by proposing a damping device of the type described above, characterized in that each friction pad comprises at least one retaining face of at least one of the elastic members against the action of centrifugal force, the retaining faces being axially positioned at a distance from one another and the elastic member being partially inserted between the two retaining faces in the manner of a wedge, so that the axial component of the centrifugal force exerted on each retaining face by the elastic member clamps each friction pad against the associated guide washer with a dynamic clamping force.

According to other features of the invention:each retaining face is in contact with the elastic member according to an angle of incidence ranging between 1° and 89° relative to the radial direction;the angle of incidence ranges between 15 ° and 45°, a static clamping force being permanently applied by clamping elastic means in order to press the friction pads;each friction pad is formed by a resiliently flexible deformable lug, said deformable lug being mounted pre-stressed against the associated guide washer;at least one of the deformable lugs is formed by a phase lug;the inner face of the two guide washers comprises ramps facing one another in such a manner as to vary the axial position of the friction faces relative to a reaction face, so that the static clamping force varies according to the angular position of the phase member relative to the guide washers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For continuing the description, the following are adopted:axial orientation directed back and forth along the rotational axis of the damping device, and indicated by the arrow “A” of the figures,radial orientation directed orthogonally to the axis of the damping device from the interior to the exterior going away from said axis;circumferential orientation directed orthogonally to the axis of the damping device and orthogonally to the radial directions.

For continuing the description, elements with similar, identical or the same functions are designated with the same reference numbers.

FIG. 1shows an angular damping device which is intended to be arranged in a motor vehicle temporary coupling system. The damping device10here is intended to be arranged in a so-called “wet” torque converter (not shown) for coupling, with angular damping, a turbine of the converter to a locking clutch of the converter.

The angular damping device made according to the teachings of the invention can also be applied to any other type of so-called “wet” clutch systems in which the damping device10can be immersed in a liquid such as oil.

The angular damping device10enables a first driving shaft (not shown) to be coupled, with angular damping, to a second driven shaft (not shown) coaxial with axis “B”.

The device10comprises a torque input member which is formed here by a radial web12which is intended to be rotationally coupled to the first driving shaft. As shown in more detail onFIG. 2, the web12has the shape of a circular washer coaxial with axis “B” and which is intended to be rotationally coupled with a hub14.

The web12has three windows16which are arranged in an arc along a ring coaxial with axis “B”. The windows are regularly distributed around axis “B”, so that the windows extend at an angle of approximately 120°. The windows16are circumferentially separated from one another by three radial thrust spokes18.

In addition the web12on its periphery comprises three external thrust lugs20. Each external thrust lug20extends radially projecting from the outer peripheral edge of the web12.

The free outer end of each external thrust lug20in addition exhibits two edges22which circumferentially extend projecting from either side of the external lug20. Each external lug20thus has the form of a “T”.

The external lugs20here are arranged in angular coincidence with the spokes18.

As shown onFIG. 1, the damping device10in addition exhibits a torque output member which is formed here by two radial guide washers24which are axially arranged on either side of the web12. The two guide washers24are rotationally connected to the second shaft by means of a splined hub25.

Each guide washer24exhibits a radial flange26which is provided with a central passage28to allow the passage of the drive shaft and the hub14of the web12.

Each flange26is also perforated by three interior windows30each of which is arranged to align with the windows16of the web12.

Each flange26further includes three exterior windows32which are arranged to align with the spaces circumferentially delimited by two external thrust lugs20of the web12.

The interior30, respectively exterior32windows of each flange26are circumferentially separated from one another by spokes34which have an axial curvature directed towards the web12.

The rear guide washer24also has an outer peripheral skirt36axially extending towards the other guide washer24. The free axial edge of the skirt36is intended to be fixed to the outer peripheral edge of the front guide washer24.

Thus, the flange26of each guide washer24has an inner ring35which radially separates the central passage28of the interior windows30, an intermediate ring37which radially separates the interior windows30from the exterior windows32, and an outer ring39which radially separates the exterior windows32of the skirt36.

When the two guide washers24are assembled, their flanges26are spaced apart by a distance sufficient to allow the web12to rotate between the two flanges26without friction.

The damping device10further comprises a first outer row of elastic members38with circumferential action and a second inner row of elastic members40with circumferential action.

The elastic members38,40are formed here by coil springs, the principal axis of which being of circumferential orientation.

In the inner row, the elastic members40are divided into three groups of two elastic members40. The elastic members40of each group are circumferentially located in series in a common associated window16of the web12, as shown onFIG. 2.

In the outer row, the elastic members38are divided into three groups of two elastic members38. The elastic members38of each group are circumferentially located in series between two associated thrust lugs20of the web12, as shown onFIG. 2.

The elastic members38,40are axially secured in their respective housings by the edges of the interior30and external32windows of the guide washers24, as shown in more detail onFIG. 3.

Each group of two elastic members38,40is thus circumferentially interposed in series between the web12and the guide washers24.

More specifically, for the inner row, each group of two elastic members40is circumferentially interposed between a radius18of the web12and the corresponding spokes34of the guide washers24. The spokes34of the guide washers24in effect have a curvature as shown onFIG. 3which enables them to come into contact with an end of one of the elastic members40of the group.

Similarly, for the outer row, each group of two elastic members38is circumferentially interposed between a thrust lug20of the web12and the corresponding spokes34of the guide washers24. The spokes34of the guide washers24also have a curvature as shown onFIG. 3which enables them to come into contact with an end of one of the elastic members40of the group.

The two elastic members38,40of each group being mounted in series, the two ends facing these two elastic members38,40are adapted to bear on one another during the transmission of torque between the web12and the guide washers24.

So that the elastic members38,40are stressed substantially along their principal axis, it is known to provide the damping device10with a phase member42.

Such a phase member42is shown in more detail onFIG. 2. The phase member42is formed here by two radial phase rings44which have dimensions corresponding to the intermediate ring37of the guide washers24.

Each phase ring44further includes three inner phase lugs46which radially extend towards the interior and three outer phase lugs48which radially extend towards the exterior. Each inner phase lug46is arranged in angular coincidence with an outer phase lug48.

The phase lugs46,48are regularly arranged around the phase ring44, substantially 120 ° from each other.

As shown onFIGS. 3 and 4, each phase lug46,48is circumferentially interposed between the two elastic members38,40in series of each group.

The phase rings44are axially arranged on both sides of the web12, as shown onFIG. 3. Each phase ring44more particularly is mounted floating between the web12and the associated guide washer24. The phase rings44are held in position through the contact between the phase lugs46,48and the elastic members38,40.

During operation of the damping device10, the elastic members38,40are generally compressed so as to cushion the torque surges. The web12rotates at a specific angle around axis “B” relative to the guide washers24, causing compression of the elastic members38,40of each group. Because of this compression, the phase rings44rotate at half of the specific angle relative to the guide washers24.

It was found that the damping device10could vibrate in a harmful way with certain higher speeds of rotation and/or torque values.

To solve this problem, it is proposed to equip the phase member42with at least two friction pads which can be axially separated by application of an axial clamping force so that a friction face50of said friction pads is axially clamped against each inner face of the guide washers24. Thus, the contact between the phase member42and the guide washers24can eliminate certain vibrations.

The friction pads are arranged in pairs between two guide washers24, so that two friction faces50of a pair are axially aligned. Thus, while the two friction pads of a pair are axially separating, the friction face50of each will rub against the inner face of an associated guide washer24.

The friction pads are advantageously formed by the outer phase lugs48. Each friction face50is carried by a free outer end portion of each outer phase lug48. Each friction face50is thus axially disposed opposite to the outer ring39of one of the guide washers24.

To enable clamping of each friction face50, each outer phase lug48is flexible in an axial direction and defines elastic clamping means.

According to one variant of the invention, not shown, the friction pads are formed by flexible lugs distinct from the phase lugs and defining elastic clamping means. They are for example lugs radially extending inwards from a second outer peripheral ring which is carried by each phase lug.

The friction faces50here are clamped against the associated guide washer24with a so-called “static” clamping force. This is an axial clamping force, the intensity of which being independent of the rotation speed of the damping device10.

The static clamping force is constantly applied by the elastic clamping means for pressing the friction pads.

Advantageously, the outer phase lugs48of the two phase rings44are resiliently flexible. At rest each outer phase lug48of a phase ring44is axially inclined in a direction opposite to the other phase ring44. Thus, in this quiescent state, the axial distance between the friction faces50of a pair is greater than the axial distance between the outer rings39of the two guide washers24. The outer phase lugs48are thus axially mounted pre-stressed between the guide washers24.

In the example shown onFIG. 3, the two phase rings44are axially supported against one another by means of a spacer52. Thus, the reaction of the static clamping force of a friction face50against a guide washer24is taken over by the other guide washer24through the other friction face50of the pair.

According to a variant not shown of the invention, the phase member comprises a single ring having pairs of phase lugs, the two lugs of a pair being axially aligned.

According to one variant of the invention, not shown, the reaction of the static clamping force of a friction pad is taken over by the web. In this case each phase ring axially bears on the web.

In addition it was found that the static clamping force was not sufficient to attenuate the vibrations of the damping device10at certain very high rotation speeds. It is found in some applications that the friction should increase with the speed in order to advantageously reduce the vibrations.

To remedy this problem, the damping device10proposes that a dynamic clamping force is superimposed on the static clamping force of each friction face50. This dynamic clamping force increases in proportion to the rotation speed, thereby enabling the vibrations that occur at high speed to be attenuated to a higher degree without reducing the effectiveness of the damping device10at low speed on account of too great friction.

To do this, each friction pad formed by an outer phase lug48comprises at least one retaining face54of at least one of the elastic members38against the action of centrifugal force. The retaining face54is formed by an interior face of an edge which circumferentially extends on either side of the free outer end of the outer phase lug48.

Each retaining face54is in permanent contact with the elastic member38. The retaining faces54of a pair of phase lugs48are axially arranged at a distance from one another and the elastic member38is partially inserted between said two retaining faces54in the manner of a wedge. Thus, when the damping device10rotates, the elastic members are radially pressed between the two retaining faces54so as to move them apart. This causes the increase of the radial and axial load on the outer phase lugs48of the pair, and thus, the clamping of each friction face50against the associated guide washers24.

To enable this effect to materialize, and as shown onFIG. 5, there is radial clearance “j” between the external edge of the corresponding external window32of each guide washer24and the elastic member38. The radial clearance “j” is sufficient to allow the elastic member38to act on the retaining faces54.

More specifically, as shown onFIG. 5, each retaining face54of a pair is in contact with the elastic member38according to an angle of incidence “α” relative to the radial direction. The force exerted by the elastic member38on the retaining face54under the effect of centrifugal force can therefore be decomposed into a dynamic axial clamping force and a vertical force.

For this effect to occur, the angle of incidence “α” ranges between 1° and 89°. It is noted that the dynamic axial clamping force is proportional to both the angle of incidence “α” and the centrifugal force.

The angle of incidence “α” is preferably between 15 ° and 45 °.

According to one variant of the invention, not shown, the friction faces of the friction pads are not clamped against the guide washers when the damping device is not rotating. Thus, friction only occurs when the damping device rotates past a threshold speed. In this case, the radial clearance between the windows and the elastic members is greater because the elastic members may be radially displaced.

According to another aspect of the invention, the damping device10is also equipped with means for increasing the static clamping force depending on the torque transmitted by the web12. The rotational angle of the web12relative to the guide washers24is all the greater, the higher the transmitted torque.

To permit this increase in the static clamping force, the inner face of the outer ring39of the two guide washers24comprises ramps56which circumferentially extend in an arc along the path that each friction face50can traverse while damping. Thus, the axial distance between the two guide washers24can vary according to the rotational angle of the phase rings44.

The axial position of the friction faces50relative to the reaction face of the static clamping force may thus vary, the reaction face being formed here by the inner face of the other guide washer24. This causes a variation of the static clamping force depending on the angular position of the phase rings44relative to the guide washers24.

The damping device10made according to the teachings of the invention is thus inexpensive to produce because it does not require extra components, in particular to produce the static clamping force.

The damping device10is also particularly effective for damping vibrations that specifically occur when the rotation speed is high, irrespective of the transmitted torque.

In addition, the dynamic clamping force is very easy to control because it depends mainly on the angle of incidence “α” of the elastic member38on the retaining face54. Such a parameter is easy to master.

The damping device10also allows damping of vibrations that specifically occur when the transmitted torque is high, irrespective of the rotation speed.