TRANSMISSION SYSTEM WITH A COUPLING DEVICE

Description

Technical field

[0001] The invention relates to the field of vehicle transmission chains.

[0002] It relates more particularly to a transmission system comprising a first element intended to be driven by an engine, a second element intended to drive at least one wheel shaft of a vehicle and a coupling device capable of selectively coupling the first element to the second element.

[0003] The invention relates in particular to a differential type transmission system intended to transmit and distribute torque from an engine to two wheel shafts of an axle of the vehicle. Technological background

[0004] Document US2015114786 discloses a differential type transmission system. The transmission system comprises a differential housing rotatable about an axis A which is equipped with a toothed wheel driven by a vehicle engine. Inside the housing are housed a carrier ring gear guided in rotation in the housing, two planetary gears which are mounted in rotation on the carrier ring gear about an axis B perpendicular to the axis A, and two planetary gears which each mesh with the two planetary gears and which are each integral in rotation with a wheel shaft.Furthermore, the transmission system comprises a coupling device which allows either the transmission system housing to be coupled to the carrier ring gear in order to enable transmission and distribution of the torque from the engine to the two wheel shafts of the axle or to uncouple them in order to interrupt the transmission of torque between the engine and the wheel shafts.

[0005] The coupling device is a dog clutch device. It comprises a first coupling part having an annular portion arranged outside the housing and projecting elements which extend from the annular portion and pass through orifices provided in the housing, thereby enabling the first coupling part and the housing to be secured in rotation. The projecting elements comprise teeth intended to cooperate with complementary grooves provided on the carrier ring. The first coupling part is axially movable relative to the housing between an uncoupled position and a coupled position in which the teeth of the first coupling part mesh with the grooves of the carrier ring.

[0006] An electromagnetic actuator is capable of exerting an axial force on the first coupling portion so as to move it from the uncoupled position to the coupled position. Furthermore, the transmission system comprises an annular target which is axially fixed to the annular portion of the first coupling portion. The annular target is arranged axially opposite a sensor, such as a Hall effect sensor, which delivers a signal representative of an axial distance between the sensor and the annular target.

[0007] The transmission system further comprises an elastic washer which is arranged axially between the annular target and the housing. This elastic washer has the function in particular of exerting a return force on the first coupling part so as to return it to its uncoupled position when the electromagnetic actuator no longer exerts force on the first coupling part.

[0008] Such a transmission system is not fully satisfactory.

[0009] In particular, the coupling device of the transmission system has many different parts, in particular to provide the target and return functions of the coupling device in its uncoupled position, which increases its complexity, cost and / or size. Summary

[0010] An idea underlying the invention is to propose a transmission system equipped with a coupling device, a target and a sensor capable of delivering a signal representative of the state of the coupling device; this transmission system being simpler and / or less bulky.

[0011] According to one embodiment, the invention provides a transmission system for a motor vehicle comprising: a first element and a second element movable in rotation relative to each other about an axis X, one of the first and second elements being intended to be driven by a motor and the other of the first and second elements being intended to drive at least one wheel shaft of the motor vehicle; and a coupling device which comprises: a first coupling part which is integral in rotation with the first element and a second coupling part which is integral in rotation with the second element, the first coupling part being movable relative to the first element between a coupled position in which the first coupling part is coupled with the second coupling part to transmit a torque between the first element and the second element and an uncoupled position in which the first coupling part and the second coupling part are uncoupled from each other,a disc which comprises a fixing zone which is fixed axially to the first coupling part, the disc comprising an annular portion forming a target and at least one elastic return portion which is configured to deform elastically during the movement of the first coupling part from the uncoupled position to the coupled position and to exert a return force capable of elastically returning the first coupling part to the uncoupled position.

[0012] Thus, the disc has a dual functionality, namely, on the one hand, forming the target whose position is capable of being detected by a sensor so as to deliver a signal indicating the position of the first part of the coupling device and, on the other hand, ensuring the return of the first coupling part to its uncoupled position. This makes it possible to reduce the cost, complexity and size of such a transmission system.

[0013] According to embodiments, such a transmission system may comprise one or more of the following features.

[0014] According to one embodiment, the transmission system comprises a sensor which is arranged opposite the annular portion of the disc and which is configured to deliver a signal representative of a distance between the sensor and the annular portion forming the target.

[0015] According to one embodiment, the sensor is arranged axially opposite the annular portion of the disc.

[0016] According to one embodiment, during the movement of the first coupling part from the uncoupled position to the coupled position, the elastic return portion is elastically constrained between a support zone of the transmission system and the fixing zone. Preferably, said support zone is axially fixed relative to the second coupling part.

[0017] According to one embodiment, the disc is made of spring steel, such as XC 70 steel, advantageously pre-hardened. According to one embodiment, the disc has a thickness of between 0.4 and 1.2 mm, for example of the order of 0.8 mm. According to one embodiment, the disc is made of stainless steel which is a non-magnetic metal, which also limits unwanted leakage of magnetic flux.

[0018] According to one embodiment, the disc comprises a plurality of elastic return portions each comprising an elastic blade capable of coming to bear against a support zone of the transmission system. Thus, the elastic blades undergo an increasing bending force during the movement of the first coupling part from the uncoupled position to the coupled position.

[0019] According to one embodiment, the support zone is axially fixed relative to the second coupling part.

[0020] According to one embodiment, each of the elastic blades has a free end. Preferably, said elastic blade bears against the support zone of the transmission system via the ends of the elastic blades.

[0021] According to one embodiment, each elastic blade is arranged in a window formed in the disc.

[0022] According to one embodiment, the elastic blades are regularly distributed around the X axis so as not to generate imbalance.

[0023] According to one embodiment, the coupling device comprises at least two elastic blades and preferably four elastic blades regularly distributed around the X axis and symmetrical two by two with respect to the X axis.

[0024] According to one embodiment, the elastic blades are located radially inside the annular portion forming the target, which makes it possible to limit the radial size of the disc.

[0025] According to one embodiment, each elastic blade extends in a direction having a circumferential component around the X axis. This makes it possible to obtain, for a given radial size, elastic blades of greater length and, consequently, of lower stiffness.

[0026] According to one embodiment, the disc and the elastic blades are dimensioned to generate a stiffness K1 opposing the axial displacement of the first coupling part from the uncoupled position to the coupled position which is between 5 and 50 N / mm.

[0027] According to one embodiment, the first element comprises a housing inside which the second coupling part is housed, the first coupling part comprising an inner portion which is housed inside the housing, an outer portion which is positioned outside the housing and a plurality of connecting portions which axially connect the inner portion and the outer portion of the first coupling part, each of the connecting portions passing through a corresponding through opening provided in the housing.

[0028] According to one embodiment, one of the inner and outer portions of the first coupling part is annular and the other comprises lugs extending axially in line with the connecting portions.

[0029] According to one embodiment, the disc is arranged outside the housing and is fixed to the outer portion of the first coupling part, each support zone being positioned on the housing.

[0030] According to one embodiment, the housing comprises studs projecting axially outwards from the housing towards the disc, each stud having one end forming one of the support zones. This makes it possible to avoid bending the elastic blades during the manufacture of the disc.

[0031] According to one embodiment, when the first coupling part is in the uncoupled position, the elastic blades extend substantially in the plane of the annular portion of the target disc.

[0032] According to one embodiment, the studs have an axial dimension greater than or equal to the travel of the first coupling part between the coupled position and the uncoupled position.

[0033] According to one embodiment, the first element is a differential housing.

[0034] According to one embodiment, the second element comprises a carrier ring which is guided in rotation about the X axis inside the housing, two satellite gears which are mounted in rotation on the carrier ring about a Z axis perpendicular to the X axis and two planetary gears which are movable in rotation about the X axis, are each engaged with the two satellite gears and are each intended to be integral in rotation with a wheel shaft. Thus, the transmission system forms a differential allowing the wheel shafts to rotate at different speeds.

[0035] According to one embodiment, the two satellite gears each comprise a bevel gear which meshes with a complementary bevel gear of the two planetary gears.

[0036] According to one embodiment, the second coupling part of the coupling device is rotationally integral with the carrier ring relative to the X axis. Thus, when the coupling device is in the coupled position, the transmission system distributes the torque coming from the engine to the two wheel shafts. Conversely, the transmission of the torque is interrupted between the housing and the carrier ring in the uncoupled position of the coupling device.

[0037] According to one embodiment, the second coupling part of the coupling device is formed in one piece with the carrier crown.

[0038] According to another embodiment, the second coupling part is rotationally fixed to one of the planetary gears. In such an embodiment, when the latter is in the coupled position, the torque is transmitted between the first element and the second element via the gears but the differential function is blocked by the coupling device, which prevents the wheel shafts from rotating at different speeds.

[0039] According to one embodiment, the disc comprises a plurality of fixing tabs which are fixed to the first coupling part.

[0040] According to one embodiment, each of the fixing tabs has a proximal end connected to the annular target portion and a free end which is fixed to the first coupling part.

[0041] According to one embodiment, each fixing tab is provided in a window formed in the disc.

[0042] According to one embodiment, the fastening tabs extend radially. Preferably, the fastening tabs extend radially inward from a radially outer edge of the windows.

[0043] According to one embodiment, the fixing tabs are regularly distributed around the X axis so as not to generate imbalance.

[0044] According to one embodiment, the coupling device comprises at least two fixing tabs and preferably four fixing tabs regularly distributed around the X axis and symmetrical two by two with respect to the X axis.

[0045] According to one embodiment, the fixing tabs are located radially inside the annular portion forming the target, which makes it possible to limit the radial size of the disc.

[0046] According to one embodiment, the fixing tabs are fixed to the outer portion of the first coupling part, in particular to its legs.

[0047] According to one embodiment, the outer portion of the first coupling part comprises tabs extending axially in the extension of the connecting portions and passing through the windows in which the fixing tabs extend.

[0048] Preferably, each fastening tab is located circumferentially between two elastic blades. There is preferably a circle centered on the X axis intersecting all the elastic blades and all the fastening tabs.

[0049] According to one embodiment, the free end of each of the fixing tabs is clipped into a groove provided in the first coupling part, in particular in its legs. The groove may be hollowed out radially.

[0050] According to another embodiment, the free end of each of the fixing tabs is fixed by a fixing member, such as a screw, to the first coupling part, in particular to one of its legs.

[0051] According to one embodiment, the coupling device further comprises an actuator comprising a casing intended to be fixed to the chassis of the vehicle and a piston axially movable relative to the casing between a retracted position and a deployed position and the piston bearing against an actuation zone of the disc so that the movement of the piston from the retracted position to the deployed position causes the movement of the first coupling part of the coupling device from the uncoupled position to the coupled position. Thus, the disc also makes it possible to transmit the actuation force between the actuator and the first coupling part, which makes it possible to further reduce the cost, complexity and size of the transmission system.

[0052] According to one embodiment, the actuator comprises an electromagnet defining a housing inside which the piston is axially movable between the retracted position and the deployed position, the piston comprising an annular body made of ferromagnetic material. Such an electromagnetic actuator is particularly advantageous in that it has excellent responsiveness.

[0053] According to one embodiment, the actuator comprises a paramagnetic tip which is fixed to the piston body and which cooperates with the actuation zone of the disc. This prevents unwanted leakage of magnetic flux.

[0054] According to one embodiment, the actuator comprises a magnetic cover against which the body of the piston abuts when the piston is in the deployed position. Thus, the magnetic cover ensures that the piston is held in the deployed position, which makes it possible to de-energize the electromagnet.

[0055] According to one embodiment, the magnetic cover comprises a shoulder against which a shoulder of the piston body abuts when the piston is in the deployed position.

[0056] According to one embodiment, the disc is capable of elastically deforming between the actuation zone and the disc attachment zone during movement of the actuator piston from the retracted position to the deployed position. Thus, the disc also makes it possible to compensate for manufacturing tolerances of the coupling device.

[0057] According to one embodiment, the actuating zone of the disc is spaced from a stop zone of the first coupling part by an axial clearance which is dimensioned so that the disc deforms during the movement of the actuator piston from the retracted position to the deployed position in order to compensate for axial manufacturing tolerances of the coupling device and so that the actuating zone of the disc abuts against the stop zone of the first coupling part when said axial manufacturing tolerances of the coupling device have been compensated.

[0058] According to one embodiment, the axial play is between 0.2 and 1.5 mm.

[0059] According to one embodiment, the disc is sized to generate a stiffness K2 opposing an axial movement of the piston towards the first coupling part which is between 50 and 500 N / mm.

[0060] The stiffness K2 is greater than the stiffness K1. Advantageously, the stiffness K2 is between 4*K1 and 20*K1 for example 10*K1.

[0061] According to one embodiment, the actuation zone of the disc is an internal annular portion. This makes it possible to limit the radial size of the coupling device.

[0062] According to one embodiment, the internal annular portion comprises oil passage grooves. The presence of oil makes it possible to limit the friction likely to be generated between the piston and the disc.

[0063] According to one embodiment, the coupling device is a dog clutch device, one of the first and second coupling parts comprising teeth and the other comprising corresponding grooves in which said teeth are engaged when the first coupling part is in the coupled position.

[0064] According to one embodiment, the coupling device is a disconnecting device capable of selectively interrupting the transmission of torque between the first element and the second element.

[0065] According to one embodiment, the invention also relates to a motor vehicle and a transmission system mentioned above.

[0066] According to one embodiment, the motor vehicle comprises an electric machine and the first element of the transmission system is capable of being driven by the electric machine.

[0067] The electric machine and transmission system can be integrated into an electric axle.

[0068] According to a second aspect, the invention also provides a transmission system for a motor vehicle comprising: a first element and a second element movable in rotation relative to each other about an axis X, one of the first and second elements being intended to be driven by a motor and the other of the first and second elements being intended to drive at least one wheel shaft of the motor vehicle; and a coupling device which comprises: a first coupling part which is integral in rotation with the first element and a second coupling part which is integral in rotation with the second element, the first coupling part being movable relative to the first element between a coupled position in which the first coupling part is coupled with the second coupling part to transmit a torque between the first element and the second and an uncoupled position in which the first coupling part and the second coupling part are uncoupled from each other,a transmission member which comprises a fixing zone which is fixed axially to the first coupling part, an actuator comprising a casing intended to be fixed to the chassis of the vehicle and a piston axially movable relative to the casing between a retracted position and a deployed position, the piston bearing against an actuation zone of the transmission member so that the movement of the piston from the retracted position to the deployed position causes the movement of the first coupling part of the coupling device from the uncoupled position to the coupled position, the transmission member being capable of elastically deforming between the actuation zone and the fixing zone of the transmission member during the movement of the piston of the actuator from the retracted position to the deployed position.

[0069] In this way, the transmission member makes it possible to compensate for the manufacturing tolerances of the coupling device.

[0070] Preferably, the transmission member is a disc. An outer portion may form a sensor target.

[0071] This second aspect of the invention may include one or more of the features mentioned in the context of the first aspect of the invention.

[0072] According to a third aspect, the invention also provides a transmission system for a motor vehicle comprising: a first element and a second element movable in rotation relative to each other about an axis X, one of the first and second elements being intended to be driven by a motor and the other of the first and second elements being intended to drive at least one wheel shaft of the motor vehicle; and a coupling device which comprises: a first coupling part which is integral in rotation with the first element and a second coupling part which is integral in rotation with the second element, the first coupling part being movable relative to the first element between a coupled position in which the first coupling part is coupled with the second coupling part to transmit a torque between the first element and the second and an uncoupled position in which the first coupling part and the second coupling part are uncoupled from each other,a disc which comprises a fixing zone which is fixed axially to the first coupling part and an annular portion forming a target, an actuator comprising a casing intended to be fixed to the chassis of the vehicle and a piston axially movable relative to the casing between a retracted position and a deployed position, the piston bearing against an actuating zone of the disc so that the movement of the piston from the retracted position to the deployed position causes the movement of the first coupling part of the coupling device from the uncoupled position to the coupled position.

[0073] Thus, the disc has a dual functionality, namely, on the one hand, forming the target whose position is detected by a sensor so as to deliver a signal indicating the position of the first part of the coupling device and, on the other hand, transmitting the actuating force between the piston of the actuator and the first coupling part, which makes it possible to reduce the cost, complexity and size of the transmission system.

[0074] This third aspect of the invention may include one or more of the features mentioned in the context of the first aspect of the invention.

[0075] In particular, the disc is capable of elastically deforming between the actuation zone and the disc attachment zone during movement of the actuator piston from the retracted position to the deployed position.

[0076] According to a fourth aspect, the invention also provides a transmission system for a motor vehicle comprising: a first element and a second element movable in rotation relative to each other about an axis X, one of the first and second elements being intended to be driven by a motor and the other of the first and second elements being intended to drive at least one wheel shaft of the motor vehicle; and a coupling device which comprises: a first coupling part which is integral in rotation with the first element and a second coupling part which is integral in rotation with the second element, the first coupling part being movable relative to the first element between a coupled position in which the first coupling part is coupled with the second coupling part to transmit a torque between the first element and the second and an uncoupled position in which the first coupling part and the second coupling part are uncoupled from each other,a transmission member which comprises a fixing zone which is fixed axially to the first coupling part, the transmission member comprising an elastic return portion which is configured to deform elastically during the movement of the first coupling part from the uncoupled position to the coupled position and to exert a return force capable of elastically returning the first coupling part to the uncoupled position, an actuator comprising a casing intended to be fixed to the chassis of the vehicle and a piston axially movable relative to the casing between a retracted position and a deployed position, the piston bears against an actuation zone of the transmission member so that the movement of the piston from the retracted position to the deployed position causes the movement of the first coupling part of the coupling device from the uncoupled position to the coupled position.

[0077] Thus, the transmission member has a dual functionality, namely, on the one hand, ensuring the return of the first coupling part to its uncoupled position and, on the other hand, transmitting the actuating force between the piston of the actuator and the first coupling part, which makes it possible to reduce the cost, complexity and size of the transmission system.

[0078] This fourth aspect of the invention may comprise one or more of the features mentioned in the context of the first aspect of the invention.

[0079] In particular, the transmission member is capable of elastically deforming between the actuation zone and the disk attachment zone during movement of the actuator piston from the retracted position to the deployed position. There are thus two distinct elastic stiffnesses ensuring on the one hand the elastic return of the first coupling part and on the other hand allowing compensation for the tolerances of the dimension chain.

[0080] Preferably, the transmission member is a disc. An outer portion of this disc may form a sensor target. Brief description of the figures

[0081] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings. [ fig.1 ] There figure 1is an overall view, in section, of a transmission system equipped with a coupling device according to a first embodiment. fig.2 ] There figure 2 is a broken sectional view with intersecting planes of the transmission system of the figure 1 when the coupling device is in the uncoupled position. fig.3 ] There figure 3 is a sectional view similar to that of the figure 2 when the coupling device is in the coupled position. [ fig.4 ] There figure 4 is a partial side view of the coupling device of the figures 1 to 3 illustrating the disc and the first coupling part of the coupling device. fig.5 ] There Figure 5 is a broken sectional view with intersecting planes according to the section planes VV of the figure 4 , illustrating in particular the housing, the disc and the first coupling part of the coupling device. fig.6 ] There figure 6is a partial side view of a coupling device according to an alternative embodiment illustrating the housing, the disc and first coupling part of the coupling device. fig.7 ] There figure 7 is a broken sectional view with intersecting planes, according to section planes VII-VII of the figure 6 . Description of the embodiments

[0082] In the description and the claims, the terms "external" and "internal" as well as the orientations "axial" and "radial" will be used to designate, according to the definitions given in the description, elements of the transmission system. By convention, the "radial" orientation is directed orthogonally to the X axis of rotation of the transmission system determining the "axial" orientation and, from the inside to the outside away from said axis, the "circumferential" orientation is directed orthogonally to the X axis and orthogonally to the radial direction.

[0083] THE figures 1 to 5illustrate a transmission system 1 according to a first embodiment. The transmission system is here a differential which is used, in a transmission chain of a vehicle, to transmit and distribute a torque coming from an engine, not illustrated, to two wheel shafts 2, 3 of an axle of a motor vehicle. Such a transmission system can, for example, be part of a secondary transmission chain capable of transmitting a torque from a secondary engine of the vehicle, such as an electric motor, to a rear or front axle of a vehicle while a primary transmission chain is capable of transmitting a torque from a main engine, for example a thermal engine, to the wheel shafts of another axle of the vehicle. According to other embodiments not illustrated, the transmission system can also take a form other than that of a differential.

[0084] The transmission system comprises a first element 4, movable in rotation around the axis X, and intended to be driven by a motor, such as an electric motor not shown, a second element 5, also movable in rotation around the axis X and intended to drive the wheel shafts 2, 3, and a coupling device 6 capable of selectively coupling or uncoupling the first element 4 and the second element 5.

[0085] The first element 4 comprises a toothed wheel 7 which is intended to be driven by the motor via a reduction gear train, not shown. This first element 4 also comprises a housing 8 which is fixed in rotation with the toothed wheel 7. The housing 8 comprises two parts 9, 10 which are fixed to each other. To do this, in the embodiment shown, each of the two parts 9, 10 comprises an external flange 11, 12 by which the two parts 9, 10 are fixed to the toothed wheel 7 and to each other.

[0086] The second element 5 comprises a carrier ring 13 of annular shape which is guided in rotation, around the axis X, inside the housing 8. To do this, the housing 8 comprises an internal cylindrical portion cooperating with a cylindrical external surface of the carrier ring 13 in order to guide it in rotation relative to the housing 8. The second element 5 further comprises two satellite gears 14, 15, visible on the figure 1, which are rotatably mounted on the carrier ring 13 around an axis Z, perpendicular to the axis X. The two satellite gears 14, 15 each comprise a bevel gear which meshes with a complementary bevel gear of two planetary gears 16, 17. The two planetary gears 16, 17 are rotatable around the axis X and are each integral in rotation with one of the two wheel axles 2, 3. The carrier ring 13, the satellite gears 14, 15 and the planetary gears 16, 17 form a differential allowing the two wheel shafts 2, 3 to rotate at different speeds.

[0087] Furthermore, the transmission system 1 comprises a coupling device 6 which, in the coupled position, makes it possible to transmit a torque between the first element 4 and one of the elements of the second element 5, here the carrier ring 13. Thus, the transmission system makes it possible, when the coupling device 6 is in the coupled position, to transmit a torque from the engine to the wheel shafts 2, 3 by exercising the differential function allowing different rotation speeds of the wheel shafts 2, 3. However, in another embodiment not shown, the coupling device is configured to couple the first element 4 with one of the two planetary gears 16, 17. The planetary gears 16, 17 then have two sets of teeth, preferably axially back to back. One cooperates with the planetary gears, the other cooperates with the first coupling part.In such an embodiment, the carrier crown 13 is integral in rotation with the housing 8 and the coupling device then aims to prevent the two wheel shafts 2, 3 from rotating at different speeds.

[0088] Returning to the embodiment shown, it can be seen that the coupling device 6 comprises a first coupling part 18 which is integral in rotation with the housing 8 while being axially movable along the axis X relative to said housing 8. The first coupling part 18 is movable between an uncoupled position, shown in the figure 2 , and a coupled position, shown on the figure 3. In the uncoupled position, the first coupling part 18 is uncoupled from a second coupling part 19 which is rotationally fixed to the carrier ring 13 so that the transmission of torque is interrupted between the housing 8 and the carrier ring 13. On the contrary, in the coupled position, the first coupling part 18 is coupled to the second coupling part 19, which allows the transmission of torque between the housing 8 and the carrier ring 13.

[0089] In the embodiment shown, the coupling device 6 is a dog clutch device. Thus, one of the first and second coupling parts 18, 19 comprises teeth while the other comprises corresponding grooves in which said teeth are engaged when the first coupling part 18 is in the coupled position. In the embodiment shown, the second coupling part 19 is formed in one piece with the carrier crown 13. In other words, teeth or grooves are provided in the lateral face of the carrier crown 13 which is turned opposite the first coupling part 18. However, although the invention is described in connection with a dog clutch device, it is not limited thereto and the coupling device may be of another type and in particular be a friction coupling device.

[0090] As shown in the Figure 5, the first coupling part 18 comprises an inner portion 20 which is housed inside the housing 8, an outer portion 21 which is positioned outside the housing 8 and connecting portions 22 which are regularly distributed around the axis X and which each pass through a corresponding through opening 23 provided in the housing 8, which makes it possible to secure the first coupling part 18 in rotation to the housing 8 while allowing relative axial movement between the first coupling part 18 and the housing 8. In the embodiment shown, the inner portion 20 is annular while the outer portion 21 comprises lugs extending axially in the extension of the connecting portions 22.However, according to another variant embodiment, the structure is inverted and the outer portion 21 is annular while the inner portion 20 comprises a plurality of axially oriented tabs extending in the extension of the connecting portions 22.

[0091] Furthermore, the coupling device 6 comprises an actuator 24, illustrated in the figures 1 to 3 , allowing the first coupling part 18 to be moved axially. The actuator 24 comprises a casing 25 which is intended to be mounted on the chassis of the vehicle, fixed in rotation relative to the latter, by means of fixing members not illustrated. The casing 25 comprises an internal skirt 26 which is fitted around a portion of the part 9 of the housing 8. The internal skirt 26 comprises a cylindrical guide portion which cooperates with a corresponding cylindrical portion of the housing 8 and thus allows the rotation of the housing 8 relative to the fixed casing 25 of the actuator 24.

[0092] The actuator 24 is an electromagnetic actuator. It comprises an electromagnet 27 defining an internal housing and a piston 28 axially movable within the internal housing between a retracted position, illustrated in figure 2 , and a deployed position, illustrated on the figure 3. The actuator 24 further comprises a magnetic cover 29 which closes the internal housing and which comprises a stop 30, such as a shoulder, to define the deployed position of the piston 28. The piston 28 comprises a body 31, of annular shape, made of ferromagnetic material, such as iron or steel for example. The piston 28 further comprises a paramagnetic tip 32, also of annular shape, which is fixed to the body 31 of the piston 28 and by which the actuating force is transmitted to the first coupling part 18. The paramagnetic tip 32 of the piston 28 thus makes it possible to avoid undesirable leaks of magnetic flux towards the other components of the coupling device 6. Furthermore, the body 31 of the piston 28 comprises a shoulder 33 intended to come into abutment against the shoulder 30 of the magnetic cover 29 when the piston 28 is in the deployed position.

[0093] When the electromagnet 27 is energized with an intensity greater than a threshold intensity, it allows the piston 28 to be moved from the retracted position, illustrated in the figure 2 , towards the deployed position, illustrated on the figure 3 . When the piston 28 is in the deployed position, the magnetic cover 29 exerts an attraction on the body 31 of the piston 28, which allows it to be maintained in the deployed position. The supply intensity of the electromagnet 27 can then be reduced as long as it remains greater than said threshold intensity. When the electromagnet 27 is switched off or is supplied with an intensity lower than the threshold intensity, an elastic return means, described below, which returns the first coupling part 18 to the uncoupled position, makes it possible to overcome the attractive force between the magnetic cover 29 and the body 31 of the piston 28 and to return the piston 28 from the deployed position to the retracted position.

[0094] The coupling device 6 is also equipped with a target 34 which is axially fixed to the first coupling part 18. Furthermore, the coupling device 6 comprises a contactless sensor 35, shown in the figure 1 , which is positioned axially opposite the target 34 and which is configured to deliver a signal representative of the axial distance between the target 34 and the sensor 35. Thus, the sensor 35 is capable of delivering a signal representative of the position of the first coupling part 18, such a signal being used to ensure the reliability of the control of the coupling device 6 and in particular to verify that the coupling device 6 is indeed in the uncoupled position or in the coupled position. The sensor 34 is for example a Hall effect sensor.

[0095] Furthermore, the coupling device 6 comprises a disc 36, visible in its entirety on the figure 4, which is formed in one piece and is axially fixed to the first coupling part 18. The disc 36 provides numerous functionalities described below and thus makes it possible to limit the cost, complexity and size of the coupling device 6.

[0096] Firstly, the disc 36 provides the function of target 34. To do this, the disc comprises an annular portion 37, arranged at the radially external periphery of the disc 36. This annular portion 37 is arranged axially opposite the sensor 35 and thus forms the target 34.

[0097] Secondly, the disc 36 acts as an elastic return means for returning the first coupling part 18 to the uncoupled position when the piston 28 of the actuator 24 returns to the retracted position.

[0098] To do this, the disc 36 comprises elastic blades 41, four in number in the embodiment shown. The elastic blades 41 each have a free end 42 which bears against a bearing zone of the housing 8 and a proximal end connected to the rest of the disc 36. The elastic blades 41 are each arranged in windows 43 positioned radially inside the annular portion 37. The elastic blades 41 extend circumferentially around the axis X, which makes it possible to obtain, for a given radial size, elastic blades 41 of greater length and, consequently, of lower stiffness. As shown in the figures 2 , 3 And 5, the free end 42 of the elastic blades 41 bears against the ends of studs 44 projecting axially from the housing 8 towards the disc 36. The studs 44 project by an axial dimension greater than the travel of the first coupling part 18 between the uncoupled position and the coupled position. Advantageously, as shown in the figure 3 , the axial dimension of the studs 44 is such that, when the coupling device 6 is in the uncoupled position, the elastic blades 41 extend substantially in the plane of the annular portion 37 forming the target 34.

[0099] The elastic blades 41 thus each form an elastic return portion which is configured to flex elastically during the movement of the first coupling part 18 from the uncoupled position to the coupled position. In reaction, the elastic blades 41 exert a return force capable of returning said first coupling part 18 to the uncoupled position.

[0100] Furthermore, the disc 36 comprises a plurality of fixing tabs 38, visible on the figure 4, also four in number in the embodiment shown. The fixing tabs 38 are circumferentially distributed around the axis X and each have a free end 39 defining a fixing zone which is fixed to the outer portion 21 of the first coupling part 18. The fixing tabs 37 are arranged in windows 40 formed in a portion of the disc 36 arranged radially inside the annular portion 37 forming a target 34. Each of the windows 40 associated with the tabs is thus arranged circumferentially between two windows 43 associated with the elastic blades. The fixing tabs 38 project radially inwards from a radially outer edge of said windows 40. Furthermore, the tabs of the outer portion 21 pass through said windows 40. Furthermore, as shown in the figures 2 , 3 And 4, the legs of the outer portion 21 each comprise a groove in which the free end 39 of one of the fixing tabs 38 is clipped, which makes it possible to fix the disc 36 to the first coupling part 18, simply, without additional fixing member.

[0101] By way of example, according to one embodiment, the disc 36 and more particularly the fixing tabs 38 and the elastic blades 41 are dimensioned to generate a stiffness K1 opposing the axial displacement of the first coupling part 18 towards the coupled position of between 5 and 50 N / mm.

[0102] Thirdly, the disc 36 also makes it possible to transmit the actuating force between the piston 28 of the actuator 24 and the first coupling part 18. To do this, the piston 28 of the actuator 24 is in contact against an internal annular portion 45 of the disc 36 which defines an actuating zone. Furthermore, the disc 36 is able to deform elastically between said actuating zone and the free ends 39 of the fixing tabs 38 when the piston 28 of the actuator 24 is moved from the retracted position to the deployed position. This makes it possible to compensate for the tolerances of the chain of dimensions of the coupling device 6 by ensuring that the piston 28 as well as the first coupling part 18 move over their entire stroke during their respective movement to the deployed position and the coupled position.In other words, this makes it possible to guarantee both that the piston 28 is, in the deployed position, in abutment against the magnetic cover 29 of the actuator 24, and that the first coupling part 18 is, in the coupled position, in axial abutment against the second coupling part 19. As shown in the . Figure 5, the internal annular portion 45 of the disc 36 is spaced from a stop zone of the first coupling part 18 by an axial clearance 49 which is greater than the axial manufacturing tolerances of the coupling device 6. The axial clearance 49 is, for example, between 0.2 and 1.5 mm. Thus, during the movement of the piston 28 of the actuator 24 from the retracted position to the deployed position, the disc 36 and in particular its internal annular portion 45 deforms in order to take up axial manufacturing tolerances of the coupling device and then the internal annular portion 45 of the disc 36 comes into abutment against the stop zone of the first coupling part 18 when said axial manufacturing tolerances of the coupling device 6 have been taken up.

[0103] According to an advantageous embodiment, the disc 36 has cutouts 46, notably shown in the figure 4, extending circumferentially in an area positioned radially between the inner annular portion 45 of the disc 36 which defines the actuation area and the windows 43. Such cutouts 46 are advantageous in that they further increase the flexibility of the disc 36.

[0104] For example, according to one embodiment, the disc 36 is dimensioned to generate a stiffness K2 opposing an axial approach of the piston 28 of the actuator 24 towards the first coupling part 18 which is between 50 and 500 N / mm. The stiffness K2 is greater than the stiffness K1. Advantageously, the stiffness K2 is between 4*K1 and 20*K1.

[0105] Fourthly, the disc 36 provides a sliding interface limiting the friction forces caused by the relative rotation of the disc 36, which is movable in rotation around the axis X, relative to the piston 28 which is fixed in rotation. According to an advantageous variant, in order to further limit the friction likely to be generated between the piston 28 and the disc 36, the annular portion 45 of the disc 36 comprises, on its face facing the piston 28, grooves 47 for the passage of oil, shown in the figure 4 .

[0106] The disc 36 is for example made of spring steel, such as XC 70 steel, advantageously pre-hardened. For example, the disc 36 has a thickness of between 0.4 and 1.2 mm, for example of the order of 0.8 mm. Alternatively, the disc 36 is made of stainless steel.

[0107] THE figures 6 and 7represent a coupling device 6 according to another embodiment. This coupling device 6 does not differ from that described above in relation to the figures 1 to 5 than by the method of fixing the disc 36 to the first coupling part 18. In this embodiment, the free end 39 of each of the fixing tabs 38 is fixed by a fixing member 48, such as a screw, to the outer portion 21 of the first coupling part 18, which makes it possible to ensure greater rigidity of the fixing of the disc 36 to the first coupling part 18.

[0108] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0109] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

1. Transmission system (1) for a motor vehicle, comprising: - a first element (4) and a second element (5) movable in rotation with respect to each other about an axis X, one of the first and second elements (4, 5) being intended to be driven by a motor and the other of the first and second elements (4, 5) being intended to drive at least one wheel shaft (2, 3) of the motor vehicle; and - a coupling device (6) which comprises: - a first coupling part (18) which is locked in rotation with the first element (4) and a second coupling part (19) which is locked in rotation with the second element (5), the first coupling part (18) being movable with respect to the first element (4) between a coupled position in which the first coupling part (18) is coupled to the second coupling part (19) to transmit a torque between the first element (4) and the second element (5) and a decoupled position in which the first coupling part (18) and the second coupling part (19) are decoupled from each other, characterized in that the transmission system (1) further comprises: - a disc (36) which comprises a fixing region which is fixed axially to the first coupling part (18), the disc (36) comprising an annular portion (37) forming a target (34) and at least one elastic return portion (41) which is configured to deform elastically during the movement of the first coupling part (18) from the decoupled position to the coupled position and to exert a return force capable of elastically returning the first coupling part (18) to the decoupled position.

2. Transmission system (1) according to Claim 1, comprising a sensor (35) which is arranged facing the annular portion of the disc (36) and which is configured to deliver a signal representative of a distance between the sensor (35) and the annular portion forming a target (34) .

3. Transmission system (1) according to Claim 1 or 2, wherein the disc (36) comprises a plurality of elastic return portions each comprising an elastic blade (41) capable of bearing against a bearing region of the transmission system (1), said bearing region being axially fixed with respect to the second coupling part (5) .

4. Transmission system (1) according to any one of Claims 1 to 3, wherein the first element (4) comprises a housing (8) inside which the second coupling part (19) is housed, the first coupling part (18) comprising an inner portion (20) which is housed inside the housing (8), an outer portion (21) which is positioned outside the housing (8) and a plurality of connecting portions (22) which axially connect the inner portion (20) and the outer portion (21) of the first coupling part (18), each of the connecting portions (22) passing through a corresponding through-opening (23) formed in the housing (8) .

5. Transmission system (1) according to Claim 4 taken in combination with Claim 3, wherein the disc (36) is arranged outside the housing (8) and is fixed to the outer portion (21) of the first coupling part (18), each bearing region being positioned on the housing (8), with in particular the housing (8) comprising studs (44) projecting axially towards the outside of the housing (8) in the direction of the disc (36), each stud (44) having one end forming one of the bearing regions.

6. Transmission system (1) according to any one of Claims 4 to 5, wherein the second element (5) comprises a carrier ring (13) which is guided in rotation about the axis X inside the housing (8), two planet gears (14, 15) which are mounted in rotation on the carrier ring (13) about an axis Z perpendicular to the axis X and two sun gears (16, 17) which are movable in rotation about the axis X, are each engaged with the two planet gears (14, 15) and are each intended to be locked in rotation with a wheel shaft (2, 3), with in particular the second coupling part (19) of the coupling device (6) being locked in rotation with the carrier ring (13) with respect to the axis X.

7. Transmission system (1) according to any one of Claims 1 to 6, wherein the disc (36) comprises a plurality of fixing tabs (38) which are fixed to the first coupling part (18).

8. Transmission system (1) according to any one of Claims 1 to 7, wherein the coupling device (6) further comprises an actuator (24) comprising a casing (25) intended to be fixed to the chassis of the vehicle and a piston (28) movable axially with respect to the casing (25) between a retracted position and a deployed position and wherein the piston (28) bears against an actuating region of the disc (36) such that movement of the piston (28) from the retracted position to the deployed position causes movement of the first coupling part (18) of the coupling device (6) from the decoupled position to the coupled position; and wherein the disc (36) is capable of deforming elastically between the actuating region and the fixing region of the disc (36) during the movement of the piston (28) of the actuator (24) from the retracted position to the deployed position.

9. Transmission system according to Claim 8, wherein the actuating region of the disc (36) is separated from an abutment region of the first coupling part (18) by an axial clearance (49) which is dimensioned such that the disc (36) deforms during the movement of the piston (28) of the actuator (24) from the retracted position to the deployed position in order to compensate for axial manufacturing tolerances of the coupling device (6) and that the actuating region of the disc (36) comes into abutment against the abutment region of the first coupling part (18) when said axial manufacturing tolerances of the coupling device (6) have been compensated for.

10. Transmission system (1) according to Claim 8 or 9, wherein the disc (36) is dimensioned to generate a stiffness opposing axial approach of the piston (28) towards the first coupling part (18) which is between 50 and 500 N / mm.

11. Transmission system (1) according to any one of Claims 8 to 10, wherein the actuating region of the disc (36) is an inner annular portion (45).

12. Transmission system (1) according to Claim 11, wherein the inner annular portion (45) comprises oil passage grooves (47).

13. Transmission system (1) according to any one of Claims 1 to 12, wherein the coupling device (6) is a dog clutch device, one of the first and second coupling parts (18, 19) comprising teeth and the other comprising corresponding grooves in which said teeth are engaged when the first coupling part (18) is in the coupled position.

14. Transmission system (1) according to any one of Claims 1 to 13, wherein the coupling device is a disconnection device capable of selectively interrupting the transmission of the torque between the first element and the second element.

15. Motor vehicle comprising an electric machine and a transmission system (1) according to any one of Claims 1 to 14, the first element of the transmission system being driven by the electric machine.