FR3023598A1 - TORQUE TRANSMISSION DEVICE FOR A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to a torque transmission device for a motor vehicle, comprising a torque input element (6), a torque output member (24, 8), a first group of elastic members (10a, 10b ) mounted between the torque input and output elements, adapted to act against the rotation of one of said input or torque output elements, upon rotation of one of said input elements; input or torque output relative to each other over a first predetermined angular range, a second group of resilient members (38), mounted with clearance between the input and torque output members, in parallel with the first group of elastic members (10a, 10b) and adapted to act against the rotation of one of said torque input or output elements, over a second defined angular range, lower than the first angular range, characterized in that the elastic members of the second gro upe comprise at least one spring washer (38) capable of generating a return force extending along the axis of said washer (38).

Description

The present invention relates to a torque transmission device for a motor vehicle. Such a device generally comprises a torque input element intended to be coupled directly or indirectly to a crankshaft, a torque output element intended to be coupled to an input shaft of a gearbox, and a first group of resilient members mounted between the input and torque output members and acting against the rotation of one of said input and torque output members relative to the other. When the torque transmission device is LTD (Long Travel Damper) type, it comprises several pairs of elastic members, the elastic members of the same pair being arranged in series via a phasing member so that that the elastic members of each group deform in phase with each other. In order to allow the damping of large torques, it is known to add to the aforementioned device a second group of elastic members, mounted with clearance between the input and torque output elements, in parallel with the first group of members. resilient and adapted to act against the rotation of one of said input elements over a limited angular range, particularly at the end of the angular stroke. The angular displacement, or the angular offset noted a, of the torque input element with respect to the torque output element, is defined with respect to a rest position (a = 0) in which no torque is transmitted through the device. The second group of elastic members makes it possible to increase the stiffness of the damping device at the end of the angular stroke, that is to say for a significant angular offset of the torque entry element with respect to the torque output element (or vice versa).

Document US 2010/0133063 discloses a LTD type torque transmission device comprising two groups of elastic members arranged in parallel, the second group being made active only at the end of angular travel a of the torque input element. relative to the torque output element (or vice versa). It can be seen that the representation of the function M = f (a) defining the torque M transmitted through the device as a function of the angular offset a, comprises a first linear portion of slope Ka (for small values of the angular offset a) and a second linear portion of slope kb larger (for the high values of the angular offset a). Ka and Kb are the angular stiffness of the device, respectively at the beginning and end of the angular stroke. If we define by K1 the cumulative stiffnesses of the first springs of each pair of the first group, by K2 the cumulative stiffness of the second springs of each pair of the first group and by K3 the cumulative stiffness of the springs of the second group, then Ka = ( K1.K2) / (K1 + K2) and Kb = Ka + K3. In the document US 2010/0133063, the torque input element comprises in particular two guide washers and the torque output element comprises in particular an annular web attached to a hub intended to be coupled to an input shaft. a gearbox. The first and second groups of elastic members are mounted radially outside the aforementioned hub. The torque transmission device therefore has a large radial size. However, depending on the applications, it may be necessary to reduce this radial size. In order to remedy this drawback, patent application FR 13 62697 in the name of the Applicant and not yet published, describes a torque transmission device for a motor vehicle, comprising a torque input element, an output element of a pair, a first group of resilient members mounted between the input and torque output members, arranged to act against the rotation of one of said input or torque output members, when the rotating one of said input or torque output members relative to the other over a first predetermined angular range, a second group of resilient members, mounted with clearance between the input and output torque members in parallel with the first group of elastic members and designed to act against the rotation of one of said input or torque output elements, over a second defined angular range, lower than the first range of ngulaire, the torque output element having a first radially inner hub, intended to be coupled to an input shaft of a gearbox, wherein the elastic members of the second group are housed, at least in part, in a housing of the first hub. The structure of the torque transmission device according to the invention makes it possible to reduce the axial size in comparison with the known structure of the document US 2010/0133063. However, in this document, the elastic members of the second group are formed by helical compression springs. Given the limited radial size, the stiffness of the springs of the second group is also limited. Indeed, the stiffness of the spring being all the more important that the diameter of the spring wire is important. However, the wire diameter of each spring is limited by the radially outer diameter of the springs. The invention aims to overcome this drawback, by proposing a torque transmission device for a motor vehicle, comprising a torque input element, a torque output element, a first group of elastic members mounted between the elements. a torque input and output device, adapted to act against the rotation of one of said input or torque output elements, upon rotation of one of said input or output elements relative to each other over a first determined angular range, a second group of resilient members, mounted with clearance between the input and torque output members, in parallel with the first group of elastic and designed members. to act against the rotation of one of said input or torque output elements, over a second defined angular range, lower than the first angular range, characterized in that the elastic members of the cond group comprise at least one spring washer adapted to generate a return force extending along the axis of said washer. The use of elastic washers makes it possible to overcome the dimensional constraints of the springs and to increase the stiffness of the elastic members of the second group, while being able to use standard washers. According to one embodiment of the invention, the elastic members of the second group comprise elastic washers of frustoconical shape, each washer comprising one end of larger diameter and one end of smaller diameter, connected by a frustoconical wall, at least two elastic washers being stacked in the same direction so that the frustoconical walls of the washers bear against one another. When the identical spring washers are stacked in the same direction, the stiffness of the stack is equal to the sum of the stiffness of the washers, the displacement of the stack (axial distance of deformation of the washers) being equal to the displacement of each washer. In addition, the elastic members of the second group may comprise elastic washers of frustoconical shape, each washer comprising an end of larger diameter and a smaller diameter end, connected by a frustoconical wall, at least two elastic washers being stacked in the opposite direction or head to tail, so that said washers are supported on each other by their ends of larger diameter or their ends of smaller diameter, and not by their frustoconical walls. When identical spring washers are stacked in the opposite direction, then the stiffness of the stack is equal to the stiffness of each washer, the displacement of the stack being equal to the sum of the deflections of each washer. Of course, it is possible to combine stacking washers in the same direction and stacking the washers in the opposite direction, so as to obtain significant stiffness and clearance. In this way, it is possible to easily vary the stiffness and deflection of each stack, from standard washers, that is to say, washers sold commercially. Preferably, the input and torque output elements comprise radial bearing surfaces of the spring washers, offset with respect to the radial plane passing through the axis of rotation of the torque entry element relative to the torque output element. In addition, the torque output member may comprise a first radially inner hub, intended to be coupled to an input shaft of a gearbox, the elastic members of the second group being housed, at least in part, in a housing of the first hub. In addition, the first group may comprise at least a first elastic member and at least one second elastic member, arranged in series via a phasing member, so that the elastic members of the first group deform into phase with each other, the phasing member being movable with respect to the torque input member and with respect to the torque output member. Furthermore, the resilient members of the first group may bear, on the one hand, on an annular web belonging to the torque input element or respectively to the torque output element, and on the other hand to two guide washers which extend radially on either side of the annular web and which are rotatable relative to the annular web, the guide washers belonging to the torque output element or respectively to the element of couple entry.

In this case, at least one of the guide washers may comprise a radially inner periphery rotatably coupled to a second hub pivotally mounted around a cylindrical portion of the first hub.The invention also relates to a hydrodynamic torque converter for a motor vehicle, characterized in that it comprises at least one device of the aforementioned type. The invention will be better understood and other details, features and advantages of the invention will become apparent on reading the following description given by way of non-limiting example with reference to the accompanying drawings, in which: FIG. 1 is a diagrammatic representation a torque converter equipped with a torque transmission device according to the invention, Figure 2 is an axial sectional view of the torque transmission device according to the invention, Figure 3 is a perspective view of said device FIG. 4 is an exploded perspective view of the device, FIG. 5 is an exploded perspective view of a portion of the device, FIG. 6 is a perspective view of a portion of the device, FIGS. 7 to 9 are views illustrating different variants of stacking spring washers, Figures 10 and 11 are schematic views illustrating the operation of the device, Figure 12 is a diagram showing the function M = f (a) defining the torque M transmitted through the device as a function of the angular offset α between the torque input element and the torque output element.

A hydrodynamic torque converter according to the invention is shown schematically and partially in FIG. 1. This converter makes it possible to transmit a torque of an output shaft of an internal combustion engine of a motor vehicle, such as for example than a crankshaft 1, to an input shaft 2 of a gearbox. The torque converter conventionally comprises an impeller impeller 3, adapted to hydrokinetically drive a turbine blade wheel 4, via a reactor 5. The impeller wheel 3 is coupled to the crankshaft 1 and the turbine wheel 4 is coupled to a turbine hub 6, itself coupled to two guide washers 7, referenced 7a and 7b. As best seen in Figure 2, the guide ring 7b and the turbine hub 6 are rotatably mounted about a central hub splined 8, to be coupled to the input shaft 2 of the gearbox . The guide washer 7a is mounted around the turbine hub 6 and fixed thereto via pins 6a (Figure 6). The two guide washers 7a, 7b extend radially and delimit between them an internal space 9 (FIGS. 5 and 6) accommodating elastic members 10a, 10b of a first group, which are, for example, helical compression springs. Each member 10a, 10b may be composed of two concentric helical springs. The guide ring 7b has a cylindrical rim 11 at its radially outer periphery, extending towards the guide ring 7a and fixed thereto. The free end of the cylindrical flange 11 comprises tabs 13 extending axially through orifices 14 of the washer 7a. These tongues 14 are riveted on the outer periphery of the guide ring 7a and can be welded thereto, so as to ensure the attachment of the two guide rings 7a, 7b. The guide washers 7a, 7b conventionally comprise windows 15 for accommodating the elastic members 10a, 10b.

A splined hub 18 is also fixed by riveting on the rear face of the guide washer 7b. This splined hub 18 comprises a radial portion 19 fixed on said rear face of the guide washer 7b, and a corrugated cylindrical flange 20 extending rearwardly from the radially outer periphery of the radial portion 19. A clutch 21 (FIG. 1) makes it possible to transmit a torque from the crankshaft 1 to the guide washers 7, in a determined operating phase, without involving the impeller wheel 3 and the turbine wheel 4. This clutch 21 comprises a coupled input element 22 at the crankshaft 1 and an output member 23, comprising the splined hub 18. A radially extending annular web 24 is mounted in the inner space and is fixed to the central hub 8, via rivets. better visible in Figure 5, the annular web 24 has a radially inner annular portion 25 from which tabs 26 (Figure 4), for example three in number, extend radially outwardly. Each lug 26 has two opposite faces 27 serving to support the elastic members 10a, 10b, inclined with respect to each other and with respect to the radial direction. Two abutment studs 28 extend circumferentially on either side of each tab 26, at its outer periphery. The elastic members of the first group 10a, 10b are circumferentially mounted between the annular web 24 and the guide washers 7a, 7b. More particularly, the elastic members 10a, 10b are arranged in pairs. The elastic members of the same pair are arranged in series via a common phasing member 29 (Figure 4), so that the elastic members 10a, 10b deform in phase with each other. In the embodiment shown in the figures, the torque converter comprises three pairs of elastic members 10a, 10b. Thus, for each pair of elastic members 10a, 10b, depending on the direction of rotation of the guide washers 7a, 7b with respect to the annular web 24, one of the elastic members (for example 10a) is intended to bear, on the one hand, on the corresponding end of the windows 15 of the guide washers 7a, 7b and, on the other hand, on the phasing member 29. The other elastic member (for example 10b) is then intended to take support, on the one hand, on the phasing member 29 and, on the other hand, on one of the faces 27 of the corresponding tab 26 of the annular web 24. The phasing member 29 comprises an annular portion 30 to from which tabs 31, here three in number, extend radially inwardly. Each lug 31 has two opposite faces 32 serving to support the resilient members 10a, 10b, inclined relative to each other and relative to the radial direction. Two abutment zones 33, forming shoulders, extend circumferentially on either side of each tab 31. The abutment pads 28 of the tabs 26 of the annular web 24 are able to bear respectively on the abutment zones 33 support portions 31 of the phasing member 29. The pads 28 and the zones 33 are positioned and dimensioned so as to limit the compression of the resilient members 10a, 10b and avoid, when it comes to coil springs, that the turns of the springs are contiguous during their compression, both in the direction of rotation said direct direction in the opposite direction of rotation, said sense retro. The forward direction corresponds to the case of operation in which torque is transmitted from the torque input member to the torque output member. In certain phases of operation, for example when the user abruptly removes his foot from the accelerator, a resisting torque is transmitted from the torque output member to the torque input member, which may cause rotation of the phasing member 29 in the retro direction. The device further comprises pendular masses 35 movably mounted at the radially outer periphery of an annular support 36 (Figure 1), the radially inner periphery of said support 36 being rotatably coupled to the washer 7b and the hub 18. The masses The pendulums 35 are movably mounted on the support 36 via rollers 37 and spacers 37 ', as is known per se, these masses 35 being intended to improve the filtration of vibrations and rotational acyclisms. A spacer member 41 is mounted axially between the annular web 24 and the support 36, said support 36 being wedged axially between the member 41 and the radial portion 19 of the hub 18. The device further comprises a second group of members elastics in the form of spring washers 38, Belleville washer type, and partly mounted in an annular housing 39 of the hub 8 and, partly, in an annular housing 40 of the hub 6. The housing 39 of the hub 8 opens axially rearward and the housing 40 of the hub 6 uncorking axially forwardly. The two housings 39, 40 delimit an internal volume whose dimensions are adjusted so as to hold the elastic washers 38 in position in said housings 39, 40. The elastic washers 38 are stacked, as will be better described hereinafter, so as to to form groups or stacks, here in number of six. Each stack comprises a first end 42 intended to bear against an abutment of the hub 6 and a second end 43 intended to bear against an abutment of the hub 8, or vice versa, depending on the direction of rotation (forward direction or retro direction ) of the torque input member with respect to the torque output member (Figures 5 and 6).

More particularly, the hub 8 comprises, for each stack, two radial shoulders 44 radially inner and two radial shoulders 45 radially external, forming bearing surfaces for the corresponding ends 42, 43 of the stacks.

Said radial bearing surfaces 44, 45 are thus offset from the radial plane passing through the axis of the hub 8. The hub 6 comprises lugs 46 (FIGS. 4 and 5) extending axially forwardly within the housing 38 and intended to support the corresponding ends of the elastic members 38. The tabs 46 are interposed each time between two stacks of washers 38. Figures 7 to 9 show different types of possible stacks of spring washers 38. In a first embodiment illustrated in Figure 7, each stack comprises elastic washers 38 of frustoconical shape (here three in number), each washer 38 comprising a larger diameter end 47 and a smaller diameter end 48, connected by a frustoconical wall 49, the spring washers 38 being stacked in the same direction so that the frustoconical walls 49 of the washers 38 bear against one another s.

When the identical spring washers 38 are stacked in the same direction, the stiffness of the stack is equal to the sum of the stiffness of the washers 38, the displacement of the stack (axial distance of deformation of the washers 38) being equal to the deflection of each washer 38.

In a second embodiment illustrated in FIG. 8, the washers 38 are stacked in opposite directions or head-to-tail, so that said washers abut one another by their ends 47 of larger diameter or by their ends of smaller diameter 48 only, and not by their frustoconical walls 49.

When identical spring washers 38 are stacked in the opposite direction, then the stiffness of the stack is equal to the stiffness of each washer 38, the displacement of the stack being equal to the sum of the deflections of each washer 38.

According to a third embodiment illustrated in FIG. 9, it is also possible to combine the stack of washers 38 in the same direction and the stack of washers 38 in the opposite direction, so as to obtain considerable stiffness and deflection. . The stacks of spring washers 38 are mounted with a circumferential clearance situated between the ends 42, 43 and the abutments 44 or the lugs 46. This circumferential clearance is noted j in FIG. 10. In operation, the guide washers 7a, 7b and the hub 6 is pivoted relative to the web 24 and the hub 8, an angle a (in the forward direction or in the retro direction).

As long as this angle a is less than the angular clearance j, that is to say at an angle ai, then only the elastic members 10a and 10b of the first group are active, that is to say act against the rotation of the torque input member (washers 7a, 7b and hub 6) relative to the torque output member (web 24 and hub 8).

When the entire game j is caught (Figure 11), that is to say when the angle a is greater than or equal to ai, then the elastic members 38 of the second group act in parallel elastic members 10a, 10b of the first group. It can thus be seen in the diagram of FIG. 12 that the curve illustrating the torque M transmitted through the device as a function of the angular offset a, comprises a first linear portion of slope Ka (for the low values of the angular offset a, this is that is, for a less than a1) and a second linear portion of greater kb slope (for the high values of the angular offset a, that is to say for a greater than ai). Ka and Kb are the angular stiffness of the device, respectively at the beginning (a <a1) and at the end of the angular stroke (a ai). If one defines by K1 the cumulative stiffnesses of the first springs 10a of each pair of the first group, by K2 the cumulative stiffnesses of the second springs 10b of each pair of the first group and by K3 the cumulative stiffnesses of the stacks of the second group, then Ka = (K1.K2) / (K1 + K2) and Kb = Ka + K3. Such a device thus allows damping and transmission of very large torques, while having a relatively small axial and radial dimensions. The position a = 0 is defined by the rest position of the device in which no torque is transmitted through said device.

Claims (9)

REVENDICATIONS1. Torque transmission device for a motor vehicle, comprising a torque input member (7, 6), a torque output member (24, 8), a first group of elastic members (10a, 10b) mounted between the torque input and output elements, adapted to act against rotation of one of said input or torque output elements, upon rotation of one of said input elements or torque output relative to each other over a first predetermined angular range, a second group of elastic members (38), mounted with clearance between the input and torque output elements, in parallel with the first group of resilient members (10a, 10b) and adapted to act against rotation of one of said torque input or output members over a second defined angular range, less than the first angular range, characterized in that what the elastic members of the second group comprise at less a spring washer (38) adapted to generate a return force extending along the axis of said washer (38). 2. Device according to claim 1, characterized in that the elastic members of the second group comprise elastic washers (38) of frustoconical shape, each washer (38) comprising an end of larger diameter (47) and a lower end diameter (48), connected by a frustoconical wall (49), at least two elastic washers 25 (38) being stacked in the same direction so that the frustoconical walls (49) of the washers (38) bear against each other. on others. 3. Device according to claim 1 or 2, characterized in that the elastic members of the second group comprise elastic washers (38) of frustoconical shape, each washer (38) comprising an end of larger diameter (47) and an end of weaker diameter (48), connected by a frustoconical wall (49), at least two elastic washers (38) being stacked in the opposite direction so that said washers (38) are supported on each other by their ends larger diameter (47) or their smaller diameter ends (48). 4. Device according to one of claims 1 to 3, characterized in that the input and torque output elements comprise radial surfaces (44, 45, 46) for supporting the spring washers (38), offset from the radial plane passing through the axis of rotation of the torque input member (7, 6) relative to the torque output member (24, 8). 5. Device according to one of claims 1 to 4, characterized in that the torque output member having a first hub (8) radially inner, intended to be coupled to an input shaft (2) of a gearbox, the elastic members (38) of the second group being housed, at least in part, in a housing (39) of the first hub (8). Torque transmission device according to one of claims 1 to 5, characterized in that the first group comprises at least a first elastic member (10a) and at least one second elastic member (10b), arranged in series by the intermediate of a phasing member (29), so that the elastic members (10a, 10b) of the first group deform in phase with each other, the phasing member (29) being movable relative to the torque input member (7, 6) and the torque output member (24, 8). 7. Device according to one of claims 1 to 6, characterized in that the elastic members (10a, 10b) of the first group are supported, on the one hand, on an annular web (24) belonging to the element of torque input or respectively to the torque output member, and secondly to two guide washers (7a, 7b) which extend radially on either side of the annular web (24) and which are movable in rotation with respect to the annular web (24), the guide washers (7a, 7b) belonging to the torque output member or the torque input member respectively. 8. Device according to claim 7, characterized in that at least one of the guide washers (7a, 7b) has a radially inner periphery coupled in rotation to a second hub (6) pivotally mounted around a cylindrical portion of the first hub (8). 9. Hydrodynamic torque converter for a motor vehicle, characterized in that it comprises at least one device according to one of claims 1 to 8.