TORQUE TRANSMITTING DEVICE

Abstract

A torque transmitting device comprising a torque input element intended to be coupled to a crankshaft of an engine, a torque output element intended to be coupled to a transmission input shaft, damping means mounted between the torque input element and the torque output element, with the torque output element being able to pivot relative to the torque input element about an axis, against a resisting torque exerted by the damping means, with the damping means comprising at least one elastic leaf able to be elastically and radially held to rest on a support member, with the elastic leaf being adapted to bend upon rotation of the torque input element relative to the torque output element, with the device further comprising clutch means mounted between the torque input element and the torque output element, wherein the supporting member is carried by the torque input element.

Claims

1. A torque transmitting device (1) comprising a torque input element (5) intended to be coupled to a crankshaft of an engine, a torque output element (8) intended to be coupled to a transmission input shaft, damping means (13, 17) mounted between the torque input element (5) and the torque output element (8), with the torque output element (8) being able to pivot relative to the torque input element (5) about an axis (X), against a resisting torque exerted by the damping means (13, 17), with the device further comprising clutch means (20, 18) mounted between the torque input element (5) and the torque output element (8), wherein the damping means comprise at least one elastic leaf (17) able to be elastically and radially held to rest on a support member (13), with said elastic leaf (17) being adapted to bend upon rotation of the torque input element (5) relative to the torque output element (8), with the supporting member being carried by the torque input element.

2. A device (1) according to claim 1, wherein the torque input element comprises a cover (5) at least partly accommodating the damping means (13, 17) and the clutch means (20, 18), with the supporting member being carried by the cover (5).

3. A device (1) according to claim 2, wherein the supporting member comprises a rolling body (13) so mounted as to pivot about a shaft (14) fixed to or formed by the cover (5).

4. A device (1) according to claim 1, wherein a shaft (14) is welded to the cover (5).

5. A device (1) according to claim 1, wherein the clutch means comprises a piston (20) axially movable from an engaged position in which the torque input element (5) is rotationally coupled to the torque output element (8) through the damping means (13, 17), and a disengaged position.

6. A device (1) according to claim 5, comprising an assistance means (24) exerting an axial stress tending to return the piston (20) to the engaged position thereof.

7. A device (1) according to claim 6, wherein the assistance means consists of at least one washer (24) elastically deformable in the axial direction (X).

8. A device (1) according to claim 5, comprising a supporting flange (18) able to be rotationally friction-coupled to the piston (20) in the engaged position and able to be rotationally uncoupled relative to the piston (20) in the disengaged position, with the elastic leaf (17) being fixed to the supporting flange (18).

9. A device (1) according to claim 4, wherein the piston (20) is rotationally coupled to the torque output element (8).

10. A device (1) according to claim 1, comprising a turbine wheel (3) and an impeller wheel (2) rotationally coupled to the torque input element (5) and able to hydrokinetically drive the turbine wheel (3).

11. A device (1) according to claim 10, comprising a reactor (4), with the impeller wheel (2) being able to hydrokinetically drive the turbine wheel (3) through the reactor (4).

12. A device (1) according to claim 1, wherein the torque output element comprises a central hub (8).

13. A device (1) according to claim 2, wherein a shaft (14) is welded to the cover (5).

14. A device (1) according to claim 3, wherein a shaft (14) is welded to the cover (5).

15. A device (1) according to claim 2, wherein the clutch means comprises a piston (20) axially movable from an engaged position in which the torque input element (5) is rotationally coupled to the torque output element (8) through the damping means (13, 17), and a disengaged position.

16. A device (1) according to claim 3, wherein the clutch means comprises a piston (20) axially movable from an engaged position in which the torque input element (5) is rotationally coupled to the torque output element (8) through the damping means (13, 17), and a disengaged position.

17. A device (1) according to claim 4, wherein the clutch means comprises a piston (20) axially movable from an engaged position in which the torque input element (5) is rotationally coupled to the torque output element (8) through the damping means (13, 17), and a disengaged position.

18. A device (1) according to claim 6, comprising a supporting flange (18) rotationally friction-coupled to the piston (20) in the engaged position and able to be rotationally uncoupled relative to the piston (20) in the disengaged position, with the elastic leaf (17) being fixed to the supporting flange (18).

19. A device (1) according to claim 7, comprising a supporting flange (18) rotationally friction-coupled to the piston (20) in the engaged position and able to be rotationally uncoupled relative to the piston (20) in the disengaged position, with the elastic leaf (17) being fixed to the supporting flange (18).

Description

[0054] The invention will be better understood, and other details, characteristics and advantages of the invention will appear upon reading the following description given by way of a non restrictive example while referring to the appended drawings wherein:

[0055] FIGS. 1 and 2 are axially sectional views of a torque converter according to a first embodiment of the invention,

[0056] FIG. 3 is an axially sectional view of a part of a torque converter according to a second embodiment of the invention,

[0057] FIG. 4 is sectional view of a part of said torque converter according to a third embodiment of the invention,

[0058] FIG. 5 is a perspective view of a part of said torque converter according to the third embodiment of the invention.

[0059] FIGS. 1 to 2 illustrate a torque converter according to a first embodiment of the invention. Such device makes it possible to transmit a torque from the output shaft of an internal combustion engine in a motor vehicle, such as for instance a crankshaft, to a transmission input shaft. The axis of the torque converter 1 bears reference X.

[0060] In the following, the words axial and radial are defined relative to the X axis.

[0061] The torque converter 1 comprises an impeller bladed wheel 2, able to hydrokinetically drive a turbine bladed wheel 3 through a reactor 4.

[0062] The impeller wheel 2 is fastened to a cover 5 consisting of two bell-shaped parts 5a, 5b assembled together by welding and defining an internal volume 6 accommodating the impeller wheel 2, the turbine wheel 3 and the reactor 4. Said cover also more generally referred to as the cover 5, comprises fastening means 7 making it possible to rotationally couple said cover 5 with the crankshaft.

[0063] The torque converter 1 further comprises a central hub 8, having an X axis, the radially internal periphery of which comprises ribs 9 and accommodated in the internal volume 6 of the cover 5. The central hub 8 comprises an annular rim 10 which radially extends outwards, and a cylindrical portion 11 positioned in front of the rim 10, i.e. on the right in FIGS. 1 and 2.

[0064] The turbine wheel 3 is fastened to the annular rim 10 of the central hub 8, for instance by rivets or by welding. The turbine wheel 3 also comprises coupling fingers or lugs 12 which axially extend frontwards, at an angle or not relative to the X axis.

[0065] The turbine wheel 3, the coupling lugs 12 and the central hub 8 may consist of one or more different parts without the operation of the torque converter being affected since such parts are fixed together.

[0066] Two supporting members or rolling bodies 13 shaped as rollers or cylindrical rollers, are mounted on the cover 5 and accommodated in the internal volume 6.

[0067] As illustrated in the embodiment FIG. 3, the rolling bodies 13 are so positioned as to be diametrally opposed. The rolling bodies 13 are mounted about shafts 14 which axially extend, with said shafts 14 being fixed to a front radial portion 15 of the portion 5b of the cover 5, for instance by friction welding. Other fastening means may be considered, of course, such as screws, or rivets, for instance, or by press-fitting into an opening of the cover 5. The rolling bodies 13 are mounted on the shafts 14 through rolling bearings 16, such as needle bearings, for instance.

[0068] The torque converter 1 further comprises two elastic leaves 17. As can be seen in FIG. 3, each elastic leaf 17 comprises a fastening portion 17a, which is fastened to an annular supporting flange 18 by rivets 19, here three in number for each leaf 17, and an elastic portion comprising a radially internal strand 17b, a radially external strand 17c, and a bowed or bent portion 17d connecting the internal strand 17b and the external strand 17c. The bowed or bent portion 17d has an angle of approximately 180. In other words, the elastically deformable portion of the elastic leaf 17 comprises two regions radially shifted relative to each other and separated by a radial space. Such leaf 17 is for example known from document FR 3 008 152 in the name of the Applicant.

[0069] The external strand 17d develops on the circumference with an angle ranging from 120 to 180. The radially external strand 17c comprises a radially external surface 17e which forms a raceway supported by the corresponding rolling body 13, with said rolling body 13 being positioned radially outside the external strand 17c of the elastic leaf 17. The raceway 17e has a globally convex shape. The raceway 17e may directly consist of a zone of the external strand 17c or of a part which is added onto said external strand 17c.

[0070] Between each elastic leaf 17 and the matching rolling body 21, the transmitted torque is broken down into radial stresses and peripheral stresses. Radial stresses make it possible for the matching blade 17 to bend and peripheral stresses make it possible for the matching rolling body 13 to move on the raceway 17e of the blade 17 and to transmit the torque.

[0071] The flange 18 is accommodated in the inner space 6 of the cover 5 and comprises a portion which radially extends and comprises a radially external area 18a, a radially median area 18b and a radially internal area 18c, axially shifted with respect to one another and connected by annular arched areas 18d, so as to give said radial portion some axial elasticity. The radially internal periphery of the radial portion of the flange 18 comprises a cylindrical rim 18e which extends frontwards, mounted about a rear cylindrical portion of a centring pin 19 having an X axis, fixed on the cover 5. The pin 19 and the cover 5 may of course be a single part.

[0072] The torque converter 1 further comprises clutch means adapted to rotationally couple the flange 18 and the hub 8, in an engaged position, and adapted to release the hub 8 of the flange 18, in a disengaged position.

[0073] The clutch means comprise an annular piston 20 which extends radially and is accommodated in the inner space 6 of the cover 5, the radially external periphery of which comprises a resting area 21 equipped with clutch lining and adapted to rest on the radially external area 18a of the flange 18, in an engaged position, so as to provide a rotational coupling of the flange 18 and the piston 20.

[0074] The radially external periphery of the piston 20 is provided with a cylindrical rim 22 extending forwards and mounted about the cylindrical portion 11 of the central hub 8 so that the piston 20 can axially slide along said cylindrical portion 11.

[0075] The radially external periphery of the piston 20 comprises coupling fingers or lugs 23 which axially extend backwards, and which are inserted into, or cooperate with the coupling fingers or lugs 12 of the turbine wheel 3 so as to provide a rotational coupling between the turbine wheel 3 and the piston 20, while enabling an axial displacement of the piston 20 relative to the turbine wheel 3.

[0076] The axial motion of the piston 20 is controlled by pressure chambers positioned on either side of the piston 20 between a disengaged position in which it is spaced from the flange 18 and an engaged position in which it is held to rest on the flange 18.

[0077] In order to facilitate the motion of the piston 20 toward the engaged position thereof, an assistance washer 24 elastically deformable in the axial direction, for instance a Belleville type washer, is mounted between the rim 10 of the hub 8 and the radial portion of the piston 20, about the cylindrical portion 11 of the hub 8. The washer 24 more particularly has a conical shape, with the radially internal periphery of the washer 24 resting on the rim 10, and with the radially external periphery of the washer 24 resting on the piston 20.

[0078] Such assistance washer 24 exerts a stress axially oriented frontwards on the piston 20, so that it is returned to its engaged position in which it rests on the flange 18. Thus, in the rest position, i.e. when the pressure in the pressure chambers positioned on either side of the piston 20 is globally balanced, the piston 20 returns to its engaged position. Such clutch means are thus of the normally closed type.

[0079] The assistance washer 24 also makes it possible to reduce the clutch engaging time, since the stress it exerts makes it possible to increase the piston 20 frontward motion speed, in the case of a clutch control. The stress exerted by the assistance washer 24 eventually makes it possible to increase the torque which can be transmitted through the clutch means.

[0080] The stress exerted by the assistance washer 24 ranges from 1000 to 8000 N, for instance, which makes it possible to reduce the clutch engaging time between 15% and 65%, from preference by approximately 40% and to increase the torque which can be transmitted through the clutch means between 5% to 70%, from preference by approximately 35%, as compared with the prior art.

[0081] Such clutch means make it possible to transmit a torque from the crankshaft to the transmission input shaft, in a determined operation phase, without any action by the hydrokinetic coupling means consisting of the impeller wheel 2, the turbine wheel 3 and the reactor 4.

[0082] In operation, the torque from the crankshaft is transmitted to the cover 5 through the fastening means 7. In the disengaged position of the piston 20, the torque goes through the hydrokinetic coupling means, i.e. the impeller wheel 2 and then the turbine wheel 3 fixed to the hub 8. The torque is then transmitted to the transmission input shaft coupled to the turbine hub 8 through the internal ribs 9 of the hub 8.

[0083] In the engaged position of the piston 20, the torque from the cover 5 is transmitted to the flange 18 through the damping means formed by the elastic leaves 17 and by the supporting members 13. The torque is then transmitted to the hub 8 through the piston 20, and then to the transmission input shaft coupled to the hub 8 through the internal ribs 9 of said hub 8.

[0084] In the engaged position of the piston 20, when the torque transmitted between the cover 5 and the hub 8 varies, the radial stresses exerted between each elastic leaf 17 and the matching rolling body 13 vary and the bending of the elastic leaf 17 is modified. The modification in the bending of the leaf 17 comes with a motion of the rolling body 13 along the matching raceway 17e due to peripheral stresses.

[0085] The raceways 17e have profiles so arranged that, when the transmitted torque increases, the rolling bodies 13 each exert a bending stress onto the matching elastic leaf 17 which causes the free distal end of the elastic leaf 17 to move towards the X axis and a relative rotation between the cover 5 and the hub 8 such that the later move away from their relative rest position. Rest position means the relative position of the flange 5 relative to the hub 8, wherein no torque is transmitted between the latter.

[0086] The profiles of the raceways 17e are thus such that the rolling bodies 13 exert bending stresses having radial components and circumferential components onto the elastic leaves 17.

[0087] The elastic leaves 17 exert, onto the rolling bodies 13, a backmoving force having a circumferential component which tends to rotate the rolling bodies 13 in a reverse direction of rotation and thus to move back the turbine wheel 3 and the hub 8 towards their relative rest position, and a radial component directed outwards which tends to maintain the raceway 17e supported by the matching rolling body 13.

[0088] When the flange 5 and the hub 8 are in their rest position, the elastic leaves 17 are preferably radially pre-stressed toward the X axis so as to exert a reaction force directed radially outwards, so as to maintain the leaves 17 supported by the rolling bodies 13.

[0089] The profiles of the raceways 17e may equally be so arranged that the characteristic transmission curve of the torque according to the angular displacement is symmetrical or not relative to the rest position. According to an advantageous embodiment, the angular displacement may be more important in a so-called direct direction of rotation than in an opposite, so-called reverse direction of rotation.

[0090] The angular displacement of the cover 5 relative to the hub 8 may be greater than 20, preferably greater than 40.

[0091] The elastic leaves 17 are regularly distributed around the X axis and are symmetrical relative to the X axis so as to ensure the balance of the torque converter 1.

[0092] The torque converter 1 may also comprise friction means 25 so arranged as to exert a resisting torque between the cover 5 and the hub 8 during the relative displacement thereof so as to dissipate the energy stored in the elastic leaves 17. The friction means consist, for instance, of a friction ring 25 fixed to the cover 5 or to the flange 18 respectively, and able to rest on and rub the flange 18, or the cover 5 respectively.

[0093] FIGS. 4 and 5 show a part of a torque converter 1 according to a third embodiment of the invention, which is different from the ones disclosed above while referring to FIGS. 1 to 3 in that the torque input element comprises a supporting cage comprising two spaced apart partitions 26, 27 connected together by axially extending spacers 28.

[0094] The spacers 28 may be provided as a single piece with one of the partitions 26, 27, as in the case shown in FIGS. 4 and 5.

[0095] The shaft 14 comprises a first and a second axial end 14a engaged into openings having a matching shape in the partitions 26, 27, with the shaft 14 further comprising an axially median portion 14b used for supporting the leaf 17 and axially located between the two partitions 26, 27. The shaft 14 is thus not cantilevered, and the stresses can be taken up at each end 14a of the shaft 14.

[0096] The partitions 26, 27 are fixed together and to the cover 5 by rivets 29.

[0097] The cage 26, 27, 28 may of course consist, at least partially, of the cover.

[0098] The operation of such a torque converter 1 is similar to the one disclosed above while referring to FIGS. 1 to 3.