Transmission system equipped with a coupling device

Abstract

The invention relates to a transmission system (1) for a motor vehicle comprising: - a first element (4) and a second element (5) rotatable relative 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 a wheel shaft of the motor vehicle; and - a coupling device (6) which comprises a first coupling part (18) rotationally fixed to the first element (4) and a second coupling part (19) rotationally fixed to the second element (5), the first coupling part (18) being axially movable relative to the first element (4) between a coupled position in which the first coupling part (18) is coupled with the second coupling part (19) to transmit a torque between the first element (4) and the second element (5) and an uncoupled position.Figure for abstract: Fig. 3.

Description

Title of the invention: Transmission system equipped with a coupling device 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 DE102013111891 A1 discloses a transmission system of type differential. The transmission system comprises a differential housing that can rotate about an axis A and is equipped with a toothed wheel driven by a vehicle engine. Inside the housing are housed a carrier ring gear that is guided in rotation in the housing, two planetary gears that are mounted in rotation on the carrier ring gear about an axis B perpendicular to the axis A, and two planetary gears that each mesh with the two planetary gears and that are each integral in rotation with a wheel shaft. Used on a motor vehicle, the differential type transmission system allows the drive wheels to rotate at different speeds when going through a bend: the wheels located on the outside of the bend rotate faster than those located on the inside.

[0005] Furthermore, the transmission system comprises a coupling device which makes it possible either to couple the housing of the transmission system to the carrier ring gear in order to allow 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. The coupling device is controlled by an electromagnetic actuator. 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, which makes it possible to secure in rotation the first coupling part and the housing. The second coupling part of the coupling device comprises the carrier ring gear. The projecting elements of the first coupling part 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] In this coupling device, the transmission of the torque coming from the thermal engine is done by the projecting elements, more precisely by the teeth formed at the end of the projecting elements. This transmission by teeth is therefore only distributed over a few angular sectors, which limits the number of teeth engaging with the complementary grooves provided on the carrier ring. Such a differential type transmission system is not fully satisfactory because its torque transmission capacity is limited.

[0007] Furthermore, the transmission system comprises an annular target which is fixed axially 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.

[0008] 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 a force on the first coupling part.

[0009] Such a transmission system is not fully satisfactory because it has many different parts, in particular to ensure the target and return functions of the coupling device in its uncoupled position, which increases its complexity and its size. Summary

[0010] An idea underlying the invention is to propose a transmission system with high torque transmission capacity whose assembly would be simplified and whose component called "first coupling part" would be simpler to manufacture.

[0011] The invention aims to remedy this problem by proposing a transmission system for a motor vehicle comprising:

[0012] - a first element and a second element movable in rotation relative to each other to the other around a main 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

[0013] - a coupling device which comprises a first coupling part integral in rotation with the first element and a second coupling part integral in rotation with the second element, the first coupling part being axially 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.

[0014] The transmission system is notable in that the first coupling part is an annular-shaped component comprising:

[0015] - a first toothing oriented radially with respect to the main axis X which is arranged to mesh with the first element, and

[0016] - a second axially oriented toothing which is arranged to mesh with the second coupling part,

[0017] the first radially oriented toothing and the second axially oriented toothing forming the annular part of the component

[0018] This transmission system, with this annular-shaped component supporting the first toothing oriented radially relative to the main axis X, has the advantage of transmitting high torques between the electric or thermal motor and the wheels of the vehicle.

[0019] The first radially oriented toothing may have, for example, a straight tooth type geometry.

[0020] The second axially oriented toothing may have, for example, a straight tooth type geometry. The profile of the tooth forming the second axially oriented toothing may vary depending on the radius taken relative to the main axis X.

[0021] Preferably, the first element may be a housing forming a cavity arranged to receive a gear train, the housing supporting on its outer periphery a torque transmission toothed wheel and supporting on the entrance of the cavity an internal spline arranged to mesh with the first radially oriented toothing of the first coupling part. In this way, the torque is now transmitted by the first radially oriented toothing of large diameter engaging with the internal spline of the housing.

[0022] Additionally, the annular portion of the first coupling portion may be inserted into the cavity of the housing.

[0023] Advantageously, the second element may comprise a carrier ring which is guided in rotation around the main axis X inside the housing, two satellite gears which are mounted in rotation on the carrier ring around a second axis Z perpendicular to the main axis X and two planetary gears which are mobile in rotation around the main axis X, are each engaged with the two satellite gears and are each intended to be integral in rotation of a wheel shaft, the second coupling part of the coupling device being rotationally fixed to the carrier ring relative to the main axis X. 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 torque is interrupted between the housing and the carrier ring in the uncoupled position of the coupling device.

[0024] Preferably, the coupling device may be a dog clutch device, the second coupling part having an axially oriented complementary toothing which is arranged to mesh with the axially oriented second toothing of the first coupling part when the first coupling part is in the coupled position.

[0025] Advantageously, the second coupling part of the coupling device can be formed in one piece with the carrier ring.

[0026] Preferably, the first radially oriented toothing and the second axially oriented toothing may be contiguous. Thus, the component called "first coupling part" is axially compact.

[0027] Advantageously, the bottom of the first radially oriented toothing defines a circumferential surface and the bottom of the second axially oriented toothing defines a flat surface, the two surfaces may have a circular edge in common.

[0028] According to a variant of the invention, the first toothing and the second toothing may have the same number of teeth.

[0029] According to a variant of the invention, the teeth of the first radially oriented toothing can be aligned with the teeth of the second axially oriented toothing, so that the bottom of the first toothing communicates directly with the bottom of the second toothing.

[0030] According to a variant of the invention, the teeth of the first radially oriented toothing can be angularly offset with the teeth of the second axially oriented toothing, so that the bottom of the second toothing communicates directly with the top of a tooth of the first toothing.

[0031] In a complementary manner, the coupling device may comprise an electromagnetic actuator bearing on the first coupling part which is arranged to move the first coupling part between the coupled and uncoupled positions by means of a pusher piston, and also an elastic return device partially fixed on the first element which is arranged to deform elastically during the axial movement of the first coupling part.

[0032] Preferably, the elastic return device can be interposed axially between the electromagnetic actuator and the first coupling part.

[0033] Advantageously, the annular part of the first coupling part may comprise connecting pads extending axially in the direction of the electromagnetic actuator to support the elastic return device and come to bear on the electromagnetic actuator.

[0034] Thus, the elastic return device jointly ensures the interface between the coupling device and the electromagnetic actuator while 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.

[0035] Advantageously, the elastic return device comprises a first fixing zone fixed to the first coupling part, a second fixing zone fixed to the first element and an elastic return portion connecting the first fixing zone to the second fixing zone.

[0036] According to one embodiment, the elastic return device may be an annular disc comprising on its internal periphery the actuating portion, the disc being capable of deforming elastically between the actuating portion and the second fixing zone during axial movement of the pusher piston.

[0037] According to another aspect of the invention, the electromagnetic actuator may comprise:

[0038] - a base and an external casing defining a hollow housing;

[0039] - a solenoid placed inside the housing;

[0040] - a closing cover attached to the base to form an opening annular in the housing, said closing cover covering one of the side faces of the solenoid;

[0041] - a pusher piston, of cylindrical shape comprising a piston body and a pusher part, which is axially movable within the housing between a retracted position and a deployed position in which the body of the piston comes to bear on the closing cover and the pusher part passes through the annular opening,

[0042] the electromagnetic actuator being remarkable in that the pusher piston, made in a single piece from a ferromagnetic material, surrounds the solenoid and comprises a conical surface defining an air gap with the closing cover.

[0043] This electromagnetic actuator with its pusher piston, made from a single piece of ferromagnetic material such as steel, has the advantage of being more reactive than a pusher piston made partially from paramagnetic material such as brass, which has a higher density. The single-piece pusher piston is therefore lighter.

[0044] Advantageously, the closing cover may also comprise a conical surface complementary to the pusher piston, the air gap being produced between the two truncated cones of the pusher piston and the closing cover. According to a variant, the The conical surface of the pusher piston and the complementary conical surface of the closing cover have similar angles. In another variant, the conical surface of the pusher piston and the complementary conical surface of the closing cover have different angles. This avoids the phenomenon of adhesion of the two surfaces.

[0045] Preferably, the air gap may be located on a diameter greater than the outer diameter of the solenoid. The particular geometry of the pusher piston and the closing cover thus limits unwanted leakage of magnetic flux outside the actuator. For example, the air gap is defined by the outer diameter of the closing cover.

[0046] Advantageously, the pusher portion of the pusher piston may comprise an external collar extending radially from the piston body, the external collar being located outside the housing of the electromagnetic actuator.

[0047] Preferably, the outer collar may form a stop with the outer casing of the housing when the pusher piston is in its retracted position. The particular geometry of the pusher portion defines a stable retracted position for the pusher piston.

[0048] According to another of its aspects, the invention also relates to a motor vehicle and a transmission system incorporating all or part of the characteristics mentioned above.

[0049] Advantageously, the motor vehicle comprises an electric machine and the first element of the transmission system is capable of being driven by the electric machine.

[0050] The electric machine and the transmission system can be integrated within an electric axle.

[0051] Other characteristics and advantages of the invention are highlighted by the following description of non-limiting examples of embodiments of the different aspects of the invention. Brief description of the figures

[0052] The invention will be better understood, and other aims, 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 appended drawings.

[0053] [Fig-1] [Fig.l] is an overall view, in section, of a transmission system equipped with an electromagnetic actuator according to a first embodiment.

[0054] [Fig.2] [Fig.2] is an isometric view of the transmission system of [Fig.l].

[0055] [Fig.3] [Fig.3] is an exploded view of the transmission system of [Fig.l].

[0056] [Fig.4] [Fig.4] is an isometric view of the first coupling part of [Fig.l].

[0057] [Fig.5] [Fig.5] is an isometric view of the first coupling part according to a second embodiment. Description of the embodiments

[0058] 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 main axis X of rotation of the transmission system determining the "axial" orientation and, from the inside to the outside moving away from said axis, the "circumferential" orientation is directed orthogonally to the main axis X and orthogonally to the radial direction.

[0059] Figures 1 to 4 illustrate 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 a thermal or electric 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.

[0060] The transmission system comprises a first element 4, movable in rotation around the main 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 main 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.

[0061] The first element 4 comprises a toothed wheel 7 which is intended to be driven by the motor via a reduction gear train 40, shown here schematically. This first element 4 also comprises a housing 8 which is integral in rotation with the toothed wheel 7. The housing 8 is here illustrated in a single piece, but could be composed of several parts fixed together.

[0062] The second element 5 comprises a carrier ring 13 of annular shape which is guided in rotation, around the main axis X, inside the housing 8. For this 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 in [Fig.l], which are mounted in rotation on the carrier ring 13 around a secondary axis Z, perpendicular to the main 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 movable in rotation around the main 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 shafts of wheel 2, 3 to rotate at different speeds.

[0063] 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 components 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.

[0064] The coupling device 6 comprises a first coupling part 18 which is rotationally fixed to the housing 8 while being axially movable along the main axis X relative to said housing 8. The first coupling part 18 is movable between an uncoupled position, shown in [Fig.l], and a coupled position. In the uncoupled position, the first coupling part 18 is uncoupled from a second coupling part 19 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.

[0065] 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 ring 13. In other words, teeth or grooves are provided in the lateral face of the carrier ring 13 which is turned opposite the first coupling part 18.

[0066] As shown in Figures 3 and 4, the first coupling part 18 is an annular-shaped component comprising:

[0067] - a first toothing 18a oriented radially with respect to the main axis X which is arranged to mesh with the first element 4, and;

[0068] - a second axially oriented toothing 18b which is arranged to mesh with the second coupling part 19,

[0069] the first radially oriented toothing and the second axially oriented toothing forming the annular part 18f of the component. This 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.

[0070] The housing 8 forms a cavity 8b arranged to receive a gear train and supports on its external periphery 8a the torque transmission toothed wheel 7. On the entrance of the cavity 8b, the housing 8 supports an internal groove 8c arranged to mesh with the first radially oriented toothing 18a of the first coupling part 18. The internal groove 8c is for example a straight groove of geometry complementary to the geometry of the first radially oriented toothing 18a. Alternatively, the internal groove 8c may be a succession of recesses capable of receiving the first radially oriented toothing 18a.

[0071] Complementarily, the second coupling part 19 comprises an axially oriented complementary toothing 9a which is arranged to mesh with the axially oriented second toothing 18b of the first coupling part 18 when the first coupling part 18 is in the coupled position. The axially oriented complementary toothing 9a is for example a series of grooves having a geometry complementary to the geometry of the axially oriented second toothing 18a. The axially oriented complementary toothing 9a may comprise teeth or grooves arranged on the lateral face of the bearing crown 13 perpendicular to the main axis X.

[0072] In this first embodiment of the invention, the first radially oriented toothing 18a and the second axially oriented toothing 18b are contiguous. In particular, the bottom of the first radially oriented toothing 18a defines a circumferential surface 18c and the bottom of the second axially oriented toothing 18b defines a flat surface 18d, the two surfaces 18c, 18d have a circular edge 18e in common.

[0073] Since the first toothing 18a and the second toothing 18b have the same number of teeth, it is possible for the teeth of the radially oriented first toothing 18a to be aligned with the teeth of the axially oriented second toothing 18b, so that the bottom of the first toothing communicates directly with the bottom of the second toothing. This makes it easier to obtain the teeth by machining.

[0074] Furthermore, the transmission system 1 comprises an electromagnetic actuator 50, illustrated in more detail in [Fig. 3], making it possible to axially move the first coupling part 18. The electromagnetic actuator 50 comprises a housing 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 housing comprises in particular a base 51 and an external casing 52 forming a hollow housing 50a.

[0075] The electromagnetic actuator 50 comprises a solenoid 57 and a pusher piston 54 axially movable within the housing 50a between a retracted position, illustrated in [Fig. 3], and an extended position. The solenoid may be a coil consisting of a metal electrical wire wound regularly in a helix around a plastic support (for insulation). The outside diameter of the winding defines the outside diameter of the solenoid. In another variant of the invention, a soft iron core may be added to the solenoid 57 to form an electromagnet.

[0076] The electromagnetic actuator 50 also comprises a closing cover 59 attached to the base 51 to form an annular opening in the housing, said closing cover covering one of the lateral faces of the solenoid. The closing cover 59 closes the housing 50a and comprises a stop 60 to define the deployed position of the pusher piston 54.

[0077] The pusher piston 54, of revolution shape around the main axis X, comprises a piston body 54a and a pusher part 54b, which is axially movable within the housing between a retracted position and a deployed position in which the piston body 54a comes to bear on the closing cover 59 and the pusher part passes through the annular opening,

[0078] According to the invention, the electromagnetic actuator is remarkable in that the piston pusher 54, made in one piece from a ferromagnetic material, surrounds the solenoid 57 and comprises a conical surface defining an air gap E with the closing cover 59. The closing cover 59 also comprises a conical surface complementary to the pusher piston forming the stop 60, the air gap E being produced between the two truncated cones of the pusher piston and the closing cover. In the embodiment illustrated in [Fig.l], the conical surface of the pusher piston 54 and the complementary conical surface 60 of the closing cover 59 have different angles. This avoids the phenomenon of adhesion of the two surfaces.

[0079] It will also be specified that the air gap E is located on an implantation diameter greater than the outside diameter of the solenoid 57. The particular geometry of the pusher piston 54 and the closing cover 59 thus limits unwanted leaks of magnetic flux outside the actuator. For example, the air gap E is defined by the outside diameter of the closing cover 59.

[0080] The electromagnetic actuator 50 is protected by the cylindrical outer casing 52 which has an axial rim 61 to define the retracted position of the pusher piston 54. The pusher piston 54 bears on the axial rim 61 by means of an outer collar 54d arranged on the outer periphery of the pusher piston.

[0081] Flowing through an alternating or direct current, via the electrical connection 58, with an intensity greater than a threshold intensity, the solenoid 57 produces a magnetic field in its vicinity, the force of the magnetic field making it possible to move the pusher piston 54 axially within the chamber between a retracted position and a deployed position in which the pusher piston comes to bear on the closing cover. The annular opening of the housing produced by the closing cover 59 tends to create an electromagnetic leak which attracts the pusher piston 54. The pusher piston 54 then moves axially until it comes into abutment on the closing cover 59. This defines the deployed position.

[0082] When the pusher piston is in the deployed position, the closing cover 59 exerts an attraction on the piston body 54a, which allows it to be maintained in the deployed position. The supply intensity of the solenoid 57 can then be reduced as long as it remains greater than said threshold intensity. When the solenoid 57 is switched off or is supplied with an intensity lower than the threshold intensity, an elastic return device 30, described below, allows the first coupling part 18 to be returned to the uncoupled position.

[0083] The elastic return device 30 is partially fixed to the first element 4 and deforms elastically during the movement of the first coupling part 18 between the uncoupled position and the coupled position. Said elastic return device is produced in the present case in the form of a multifunctional disc 30, visible in [Fig. 2], which is formed in a single piece and is fixed axially to the first coupling part 18. The disc 30 provides numerous functionalities described below and thus makes it possible to limit the cost, complexity and size of the coupling device 6.

[0084] The pusher part 54b comprises a bearing surface 54f arranged to bear on the disc 30 of the transmission system by which the actuating force is transmitted to the first coupling part 18. The bearing surface 54f is perpendicular to the main axis X.

[0085] Firstly, the disc 30 provides the function of target 34 for evaluating the position of the pusher piston 54. To do this, the disc comprises an annular portion 37, arranged at the radially external periphery of the disc 30. This annular portion 37 is arranged axially opposite the sensor 70 and thus forms the target 34. The target 34 is fixed axially to the first coupling part 18. Furthermore, the device coupling device 6 comprises a contactless sensor 70, shown in [Fig.l], 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 70. Thus, the sensor 70 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 70 is for example a Hall effect sensor.

[0086] Secondly, the disc 30 makes it possible to transmit the actuating force between the pusher piston 54 of the electromagnetic actuator 50 and the first coupling part 18. To do this, said elastic return device comprises an actuating portion 35 which can be moved axially relative to the first element 4. The pusher piston 54 is in contact against an internal annular portion 35 of the disc 30 which defines the actuating portion.

[0087] Thirdly, the disc 30 acts as an elastic return means for returning the first coupling part 18 to the uncoupled position when the pusher piston 54 of the electromagnetic actuator 50 returns to the retracted position.

[0088] To do this, the disc 30 comprises a first fixing zone fixed to the first coupling part 18, a second fixing zone fixed to the first element 4 and an elastic return portion 31 connecting the first fixing zone to the second fixing zone. The annular disc 30 comprises on its internal periphery the actuating portion 35 and deforms elastically between the actuating portion 35 and the second fixing zone during the axial movement of the pusher piston 54. Thus, the elastic return device 30 is interposed axially between the electromagnetic actuator 50 and the first coupling part 18.

[0089] As illustrated in [Fig. 3], the annular portion 18f of the first coupling portion 18 comprises connecting pads 18g extending axially in the direction of the electromagnetic actuator 50 to support the elastic return device 30 and to bear on the electromagnetic actuator. Thus, the first coupling portion 18 comprises an annular portion 18f which is housed inside the housing 8 and connecting pads 18g which are regularly distributed around the main axis X and which each pass through a corresponding opening 82 formed in the housing 8, by means of an attached plate 80.

[0090] The disc 30 comprises a plurality of elastic return portions 31 each made in the form of an elastic blade which connects the first fixing zone to the second fixing zone. The elastic blades 31 each have a free end 32 which bears against a bearing zone of the housing 8 and a proximal end connected to the rest of the disc 30. The elastic blades 31 are each arranged in windows 33 positioned radially inside the annular portion 37. The elastic blades 31 extend circumferentially around the main axis X, which makes it possible to obtain, for a given radial size, elastic blades 31 of greater length and, consequently, of lower stiffness. As shown in [Fig.2], the free end 32 of the elastic blades 31 bears against the ends of bosses 81 projecting axially from the attached plate 80 of the housing 8 towards the disc 36. The bosses 81 project by an axial dimension greater than the travel of the first coupling part 18 between the uncoupled position and the coupled position. The disc 30 comprises four elastic blades 31 in the embodiment shown.

[0091] The elastic blades 31 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 31 exert a return force capable of returning said first coupling part 18 to the uncoupled position.

[0092] Furthermore, the disc 30 is fixed to the first coupling part 18 by means of fixing screws 90.

[0093] Fourthly, the disc 30 provides a sliding interface limiting the friction forces caused by the relative rotation of the disc 30, which is movable in rotation about the main axis X, relative to the pusher piston 54 which is itself fixed in rotation. In particular, the pusher part 54b of the pusher piston comprises a bearing surface 54f arranged to come to bear on the disc 30, as illustrated in [Fig. 4]. The bearing surface 54f of the pusher piston 54 comprises a surface treatment facilitating sliding.

[0094] This first embodiment of the invention illustrates the case where the elastic return device 30 is arranged 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. In this first embodiment, the coupling device 6 is normally open, that is to say that the first and second coupling parts 18, 19 are fitted into each other only when the electromagnetic actuator 50 is active, that is to say supplied with current via the electrical connection 58. This first embodiment makes it possible to reduce the cost, complexity and size of the transmission system.

[0095] A second embodiment of the invention will now be described with reference to [Fig. 5], which differs from the previous one by a different arrangement of the first and second teeth 18a, 18b of the first coupling part 18.

[0096] [Fig. 5] is a perspective view of the first coupling part 18 in which the teeth of the radially oriented first toothing 18a are angularly offset with the teeth of the axially oriented second toothing 18b, so that the bottom of the second toothing communicates directly with the top of a tooth of the first toothing. With this tooth arrangement, it is possible to adapt the number of teeth according to the torque demand to be transmitted.

[0097] Although the invention has been described in connection with several particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the 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.

[0098] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

1. Claims Transmission system (1) for a motor vehicle comprising: - a first element (4) and a second element (5) movable in rotation relative to each other around a main 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) rotationally fixed to the first element (4) and a second coupling part (19) rotationally fixed to the second element (5), the first coupling part (18) being axially movable relative to the first element (4) between a coupled position in which the first coupling part (18) is coupled with the second coupling part (19) to transmit a torque between the first element (4) and the second element (5) and an uncoupled position in which the first coupling part (18) and the second coupling part (19) are uncoupled from each other, wherein the first coupling part (18) is an annular-shaped component comprising: - a first toothing (18a) oriented radially relative to the main axis (X) which is arranged to mesh with the first element (4), and; - a second axially oriented toothing (18b) which is arranged to mesh with the second coupling part (19), the first radially oriented toothing and the second axially oriented toothing forming the annular part (18f) of the component, wherein the first element (4) is a housing (8) forming a cavity (8b) arranged to receive a gear train, the housing (8) supporting on its external periphery (8a) a torque transmission toothed wheel (7) and supporting on the entrance of the cavity (8b) an internal spline (8c) arranged to mesh with the first radially oriented toothing (18a) of the first coupling part (18), characterized in that the annular part (18f) of the first coupling part (18) is inserted into the cavity (8b) of the housing (8).

2. Transmission system (1) according to the preceding claim, wherein the second element (5) comprises a carrier ring (13) which is guided in rotation about the main axis (X) inside the housing (8), two satellite gears (14, 15) which are mounted in rotation on the carrier ring (13) about a second axis (Z) perpendicular to the main axis (X) and two planetary gears (16, 17) which are rotatable about the main axis (X), are each engaged with the two satellite gears (14, 15) and are each intended to be rotationally secured to a wheel shaft (2, 3), the second coupling part (19) of the coupling device (6) being rotationally secured to the carrier ring (13) relative to the main axis (X).

3. Transmission system (1) according to one of the preceding claims, wherein the coupling device (6) is a dog clutch device, the second coupling part (19) comprises an axially oriented complementary toothing (9a) which is arranged to mesh with the axially oriented second toothing (18b) of the first coupling part (18) when the first coupling part (18) is in the coupled position.

4. Transmission system (1) according to one of claims 1 to 3, in which the first radially oriented toothing (18a) and the second axially oriented toothing (18b) are contiguous.

5. Transmission system (1) according to one of claims 1 to 4, wherein the first toothing (18a) and the second toothing (18b) have the same number of teeth.

6. Transmission system (1) according to one of claims 1 to 5, in which the teeth of the first radially oriented toothing (18a) are aligned with the teeth of the second axially oriented toothing (18b), so that the bottom of the first toothing communicates directly with the bottom of the second toothing.

7. Transmission system (1) according to the preceding claim, in which the bottom of the first radially oriented toothing (18a) defines a circumferential surface (18c) and the bottom of the second axially oriented toothing (18b) defines a flat surface (18d), the two surfaces (18c, 18d) have a circular edge (18e) in common.

8. Transmission system (1) according to one of claims 1 to 5, in which the teeth of the first radially oriented toothing (18a) are angularly offset with the teeth of the second toothing (18b) oriented axially, so that the bottom of the second toothing communicates directly with the top of a tooth of the first toothing.

9. Transmission system (1) according to one of the preceding claims, wherein the coupling device (6) comprises an electromagnetic actuator (50) bearing on the first coupling part (18) which is arranged to move the first coupling part (18) between the coupled and uncoupled positions by means of a pusher piston (54), and also an elastic return device (30) partially fixed on the first element (4) which is arranged to deform elastically during the axial movement of the first coupling part (18).

10. Transmission system (1) according to the preceding claim, in which the elastic return device (30) is interposed axially between the electromagnetic actuator (50) and the first coupling part (18).

11. Transmission system (1) according to the preceding claim, in which the annular part (18f) of the first coupling part (18) comprises connecting pads (18g) extending axially in the direction of the electromagnetic actuator (50) to support the elastic return device (30) and to bear on the electromagnetic actuator.

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