TRAINING DEVICE FOR VEHICLE

Description

[0001] The present invention relates to a traction device for a vehicle, in particular for a railway vehicle.

[0002] The present invention also relates to a vehicle, in particular a railway vehicle comprising such a traction device.

[0003] Traction devices comprising at least two traction motors, each with an output shaft, are known from the prior art. Each output shaft is designed to drive a respective axle of a vehicle. In some cases, the traction device includes control motors to compensate for any differences in the angular positions and / or rotational speeds of the traction motors.

[0004] However, such control motors can increase the power consumption of the traction device, as well as the weight and volume of said device when such motors have a dedicated power supply.

[0005] Furthermore, to mitigate power supply failures to the traction motors, the traction system typically includes a battery pack charged by a battery charger. However, such a pack contributes to the weight and size of the traction system, as well as its energy consumption.

[0006] Document FR 3 052 729 A1 describes a traction system for a vehicle. The traction system comprises at least two synchronous motors, as well as two control motors operated by control means. A power supply unit is common to all the motors.

[0007] Therefore, there is a need for a traction device with reduced volume, weight and energy consumption, capable of compensating for failures in the power supply of traction motors.

[0008] The invention also relates to a traction device according to claim 1.

[0009] According to other advantageous aspects of the invention, the traction device comprises one or more of the features of claims 2 to 11.

[0010] The invention also relates to a vehicle according to claim 12.

[0011] Other features and advantages of the invention will become apparent from the following description of embodiments of the invention, given by way of example only and with reference to the single figure which is a partial schematic representation of an example implementation of a traction device.

[0012] A vehicle 10 and a traction device 11 are illustrated in the figure.

[0013] Vehicle 10 is, for example, a railway vehicle, such as a train, a tram, or a tram-train.

[0014] The vehicle 10 has at least one axle 12 carrying two wheels 14. In the example illustrated by the figure, the vehicle 10 has at least two axles 12 each carrying two wheels 14.

[0015] In the case of a railway vehicle, said vehicle 10 usually comprises at least one bogie, including at least said axles 12. Each axle 12 is movable in rotation about a first axis X1.

[0016] Advantageously and as illustrated by the figure, each axle 12 is rotationally fixed with a toothed wheel 16 through which said axle 12 is kinematically connected to the traction device 11.

[0017] The traction device 11 includes at least two traction motors 20, a transmission block 22 for each traction motor 20, a control motor 24 for at least one of the traction motors 20, an energy storage unit 26 and a control unit 27. Optionally, the traction device 11 also includes an immobilizing unit 32, advantageously controlled by the control unit 27.

[0018] Each traction motor 20 comprises an output shaft 40. Each traction motor 20 further comprises a stator 40A and a rotor 40B. The rotor 40B is free to rotate relative to the stator 40A and is fixed in rotation to the output shaft 40 of the traction motor 20. Each output shaft 40 is free to rotate about a second axis X2.

[0019] In the example illustrated by the figure, the traction motors 20 are internal rotor motors, that is to say that the stator 40A is located outside the rotor 40B.

[0020] Alternatively, the traction motors 20 are external rotor motors, i.e. the rotor 40B is located outside the stator 40A.

[0021] Advantageously, each traction motor 20 is a synchronous motor. Such a synchronous motor is more efficient and more compact than an asynchronous motor.

[0022] Each traction motor 20 is powered by a power unit 44. According to the invention as illustrated by the figure, the power unit 44 is different from the energy storage unit 26. In the case of a railway vehicle, the power unit 44 is, for example, a catenary or a traction rail.

[0023] Alternatively, the power unit 44 is a battery or a fuel cell.

[0024] Advantageously, the traction device 11 comprises a single converter 46 connecting the power supply unit 44 and several, or even all, of the traction motors 20. The converter 46 is suitable for operating the traction motors 20 in all four quadrants (reverse generator, forward motor, reverse motor, forward generator). In the example shown in the figure, the converter 46 is an inverter. The converter 46 is advantageously controlled by the control unit 27.

[0025] Each transmission block 22 connects the output shaft 40 of the traction motor 20 corresponding to a separate axle 12 of the vehicle 10.

[0026] Each transmission block 22 comprises elements. At least one of the elements is rotationally fixed to the output shaft 40 of the corresponding traction motor 20. In addition, at least one of the elements is capable of rotating an axle 12 of the vehicle 10.

[0027] In the example illustrated by the figure, each transmission block 22 is an epicyclic gear train completed by a reducer.

[0028] Each epicyclic gear train comprises a first, a second, and a third element, selected from an inner planet gear 50, an outer planet gear 52, and a planet carrier 54 carrying at least one planet gear meshing with the inner planet gear 50 and with the outer planet gear 52. The inner planet gear 50 and the outer planet gear 52 are coaxial. The first element is rotationally fixed to the output shaft 40 of the corresponding traction motor 20. The second element is designed to drive a respective axle 12 of the vehicle 10. The third element is rotationally fixed to the corresponding control motor 24.

[0029] In the example illustrated in the figure, the first element is formed by the outer planet gear 52. The outer planet gear 52 is then rotationally fixed to the output shaft 40, and therefore free to rotate about the second axis X2. The outer planet gear 52 has a general shape of revolution about the second axis X2. The outer planet gear 52 has, for example, a ring shape, comprising a toothed inner surface.

[0030] In the example described, the second element is formed by the satellite carrier 54.

[0031] The planet carrier 54 comprises at least one, and generally several, planets, each meshing with the inner planetary gear 50 and with the outer planetary gear 52 (specifically with the inner toothed surface). Thus, each planet is arranged radially between the inner planetary gear 50 and the outer planetary gear 52. Each planet has a general shape of revolution about a respective third axis X3, and each planet is free to rotate about said respective third axis X3. The planet carrier 54 comprises, for example, a circular toothed portion, free to rotate about the second axis X2, and complementary to the gear 16 and meshing with said gear 16. The planet carrier 54 also comprises, for each planet, a support portion connected by a pivot joint to said planet, said pivot joint being defined around the corresponding third axis X3.

[0032] In the example described, the third element is the inner planet 50.

[0033] Furthermore, in this example, the output shaft 40 of the traction motor 20, the output member 60 of the control motor 24, the inner planetary gear 50, the outer planetary gear 52 and the corresponding planet carrier 54 are coaxial.

[0034] Each control motor 24 includes a rotary output member 60. The output member 60 meshes with one of the elements of the transmission block 22. In the example shown in the figure, each rotary output member 60 meshes with the inner planetary gear 50 of the transmission block 22 of the corresponding traction motor 20. Each rotary output member 60 is then free to rotate about the second axis X2.

[0035] Each control motor 24 further comprises a stator 60A and a rotor 60B. The rotor 60B is free to rotate relative to the stator 60A, and is fixed in rotation to the rotating output member 60 of the control motor 24.

[0036] Each control motor 24 is suitable for, in motor mode, driving in rotation at least one of the elements of the corresponding transmission block 22, and for, in generator mode, being driven in rotation by at least one of the elements of the corresponding transmission block 22. The or each control motor 24 is, for example, a synchronous motor or an asynchronous motor.

[0037] Preferably, the number of control motors 24 is equal to the number of traction motors 20, each control motor 24 being associated with a separate traction motor 20. In the example illustrated in the figure, the traction device 11 comprises two traction motors 20, each associated with a separate control motor 24.

[0038] Advantageously, the power of each control motor 24 is much less than the power of each traction motor 20. For example, the power of each control motor 24 is less than or equal to 5% of the power of each traction motor 20. Thus, the control motors 24 do not involve any significant additional electrical consumption.

[0039] The energy storage unit 26 is designed to exchange energy with each control motor 24 depending on the mode, motor or generator, of said control motors 24.

[0040] The energy storage unit 26 is, for example, a battery. The battery's storage capacity is defined by the use cases of the traction device 11, particularly in the event of failure or unavailability of the power supply unit 44.

[0041] Advantageously, the energy storage unit 26 is designed to receive energy only from the control motor(s) 24. This therefore eliminates the need for a charger, such as a battery charger, to charge the energy storage unit 26.

[0042] The traction device 11 further comprises, for each control motor 24, a converter 61 connecting the energy storage unit 26 and said control motor 24. Each converter 61 is suitable for operating the corresponding control motor 24 in all four quadrants, in both directions of rotation, so that the control motor 24 is: in motor mode: powered by the storage unit 26 to drive in rotation at least one of the elements of the corresponding transmission block 22 and in particular the inner planetary gear 50, and in generator mode: capable of supplying energy to the storage unit 26, by being driven in rotation by at least one of the elements of the corresponding transmission block 22 and in particular the inner planetary gear 50.

[0043] The converter 61 is, for example, an inverter. The control of the converter(s) 61 is advantageously carried out by the control unit 27.

[0044] The energy storage unit 26 is, for example, connected to other utilities of the vehicle 10 so as to power said utilities. Such utilities are, for example, the air conditioning system or the lighting system of the vehicle 10.

[0045] The control unit 27 is suitable for measuring or receiving a measurement of the angular position and / or the rotational speed of the output shaft 40 of each traction motor 20. Advantageously, the control unit 27 is suitable for calculating the differences in rotational speed between the output shafts 40 of the traction motors 20 and / or the angular offsets between said output shafts 40.

[0046] The control unit 27 is suitable for receiving a control signal and for operating the control motor(s) 24 and the traction motor(s) 20 via the converters 61 and 46 according to the control signal and, advantageously, other input signals to the control unit 27, such as the state of charge of the energy storage unit 26 or the state of proper operation of the various components of the traction device 11.

[0047] The control signal is, for example, a signal calculated from a user command via a human-machine interface or is a signal automatically generated by a processing unit based on various parameters such as vehicle speed 10.

[0048] Advantageously, the control unit 27 is suitable for controlling each control motor 24 according to a rotational speed of the corresponding element of the transmission block 22. For example, such a rotational speed is established so that the difference in angular position and / or the difference in rotational speed between the output shafts 40 is minimal.

[0049] In the example illustrated by the figure, the control unit 27 is designed to control a rotational speed of the corresponding inner planetary gear 50 as a function of the rotational speeds of each output shaft 40 and / or the angular positions of each output shaft 40. More particularly, the control unit 27 is configured to control the rotational speeds of the inner planetary gears 50 in such a way as to cancel the differences in speed of the output shafts 40 and / or the angular offsets between said output shafts 40.

[0050] Thus, when the speeds of the output shafts 40 are substantially identical, and / or the angular offset is substantially zero, the control unit 27 rotates the inner planetary gears 50 at the same speed, thereby contributing to the traction / braking force delivered by the traction device 11 if the state of the energy storage unit allows it. Conversely, in the event of a difference in speed and / or angular position between the output shafts 40, the control unit 27 varies the speed of at least one of the inner planetary gears 50 to cancel out such a difference.

[0051] For example, when the vehicle 10 is in start-up mode, the control unit 27 is designed to control the control motor(s) 24 to compensate for angular differences in the traction motors 20 before starting said traction motors 20 via the converter 46.

[0052] For example, when the vehicle 10 is in normal operating phase, the control unit 27 is suitable for controlling the control motor(s) 24 and the converter 61 to store energy generated by the rotation of the control motor(s) 24 driven by at least one of the elements of the corresponding transmission block 22 and to store said energy in the energy storage unit 26.

[0053] For example, when the vehicle 10 is in braking phase, the control unit 27 is designed to control the control motor(s) 24 to store energy and store said energy in the energy storage unit 26, and thus assist in braking.

[0054] For example, when one of the traction motors 20 is not functioning, the control unit 27 is designed to control the corresponding control motor 24 to prevent the rotor 40B of said traction motor 20 from being driven by the corresponding axle 12. Alternatively, the control of each control motor 24 according to a rotational speed of the corresponding element of the transmission block 22, established as a function of the angular position and / or the measured rotational speed of each output shaft 40, is carried out by another control unit of the traction device 11, separate from the control unit 27.

[0055] The immobilization unit 32 is suitable for immobilizing at least one of the traction motors 20 associated with a control motor 24. Such immobilization is advantageously reversible.

[0056] More precisely, the immobilizing unit 32 is movable in at least two positions: a first position (or position 0 in the figure) in which the rotors 40B and 60B of the corresponding traction motors 20 and control motors 24 are free, and a second position (or position 1' in the figure) in which only the rotor 40B of the corresponding traction motor 20 is immobilized. Thus, in the example illustrated in the figure, when the immobilizing unit 32 immobilizes the rotor 40B of one of the traction motors 20, the outer planetary gear 52 of the corresponding transmission block 22 is then prevented from rotating. When the rotor 40B of the traction motor 20 is not prevented from rotating by the immobilizing unit 32, the outer planetary gear 52 of the corresponding transmission block 22 is free to rotate about the second axis X2.

[0057] For example, the immobilizing unit 32 includes at least one brake suitable for immobilizing the outer planetary ring 52 in the second position and releasing the outer planetary ring 52 in the first position.

[0058] Preferably, the immobilizing unit 32 is also movable in a third position (or position 1 in the figure) in which only the rotor 60B of the corresponding control motor 24 is immobilized. Thus, in the example illustrated in the figure, when the immobilizing unit 32 immobilizes the rotor 60B of one of the control motors 24, the inner planetary gear 50 of the corresponding transmission block 22 is then prevented from rotating. When the rotor 60B of the control motor 24 is not prevented from rotating by the immobilizing unit 32, the inner planetary gear 50 of the corresponding transmission block 22 is free to rotate about the second axis X2.

[0059] Alternatively or in addition, the immobilizing unit 32 includes at least one dog clutch for immobilizing the faulty motor. In the event of a failure of a control motor 24, the dog clutch is engaged in the third position (for example, by activating an electromagnet), which immobilizes the rotor 60B of the control motor 24. This allows the traction motor 20 associated with the faulty control motor 24 to remain operational, with control being transferred to the other control motors 24. In the event of a loss of power to the train, the dog clutch is engaged in the second position, which immobilizes the rotor 40B of the traction motor 20, thus allowing the transmission of torque from the control motor 24, powered by the energy storage unit 26, to the corresponding axle 12.

[0060] The control of the immobilization unit 32 is advantageously carried out by the control unit 27.

[0061] The control unit 27 is equipped, where appropriate, to detect an anomaly or to receive an anomaly signal for each traction motor 20. In this description, the term "anomaly" means any malfunction of a motor that may impair the proper operation of said motor and / or the integrity of said motor.

[0062] For example, the fault signal for a traction motor 20 is generated by the converter 46 connected to said traction motor 20. Thus, the converter 46 is designed to detect a short circuit in each traction motor 20 or in a power supply circuit for said traction motor 20. The converter 46 therefore includes, for example, short-circuit detection devices and / or temperature measurement devices for detecting a temperature rise above a predetermined threshold. Thus, a fault is considered detected, for example, when a short circuit is detected or when the temperature exceeds the predetermined threshold.

[0063] Preferably, the control unit 27 is also equipped, where appropriate, to detect an anomaly or to receive an anomaly signal for each of the control motors 24.

[0064] For example, the fault signal for a control motor 24 is generated by the converter 61 connected to said control motor 24. Thus, the converter 61 is suitable for detecting a short circuit, in the control motor 24 or in a power supply circuit of said control motor 24. The converter 61 then includes, for example, short circuit detection elements, and / or temperature measurement elements enabling the detection of a temperature rise beyond a predetermined threshold.

[0065] Preferably, the control unit 27 is also capable, where appropriate, of detecting or receiving a signal indicating that the power supply unit 44 is faulty or unavailable.

[0066] Depending on the state of said anomaly and / or availability signals, the control unit 27 is suitable for controlling the immobilization unit 32 and / or the control motors 24.

[0067] Thus, in the example illustrated in the figure, when a fault in a traction motor 20 is detected, such as a short circuit, the torque applied by the control motor 24 to the output member 60, and in particular to the inner planetary gear 50, is reduced. Indeed, the operating point of the control motor 24 (torque, speed) is set by the control unit 27. In this case, the torque is reduced and the speed of the output member 60 increases, but the product of the torque and the speed remains less than the maximum power that the control motor 24 can deliver. The inner planetary gear 50 is then freed to rotate, and the distribution of the axle's motion transmission between the outer planetary gear 52 and the inner planetary gear 50 is modified.The inner planetary gear 50 will begin to rotate faster, and the outer planetary gear 52 will slow down until the outer planetary gear 52 comes to a complete stop, while the inner planetary gear 50 will rotate at high speed but with very low or even zero torque. In this case, the inner planetary gear 50 is free to rotate, and the axle can no longer drive the outer planetary gear 52, and therefore the traction motor 20. In other words, the rotation of the output shaft 40 of the traction motor 20 no longer interferes with the rotation of the axle 12. It is then possible to stop the traction motor 20, without any residual rotation due to the axle 12, to correct the detected anomaly and, if necessary, to immobilize the traction motor after it has stopped, via the immobilizer unit 32.

[0068] Indeed, in the traction device 11 described, there is transmission of motion and torque between the axle 12 and the traction motor 20 only if the internal planetary gear provides a torque having at least the same order of magnitude as that which passes between the axle 12 and the traction motor 20.

[0069] The traction motor and the axle are thus decoupled in the event of a traction motor failure and can be easily and quickly recoupled if the failure is only temporary. This is achieved simply by increasing the torque applied to the inner planetary gear. If the traction motor is released by initiating its rotation and a torque is applied to the inner planetary gear via the control motor, the inner planetary gear will slow down until it stops, while the outer planetary gear will rotate faster. The traction motor can then be reactivated to control the axle's rotation.

[0070] Such an embodiment makes it possible in the event of failure of the traction motor 20 and in particular of short circuit, to prevent the traction motor 20 from continuing to turn by being driven by the axle while it is short-circuited, and thus to prevent an electromagnetic force generated by the rotating field of the traction motor from causing a very strong current in the short-circuit loop, which would lead to heating that could lead to fire.

[0071] When an anomaly of a control motor 24 is detected, the rotor 60B of said control motor 24 is immobilized by the immobilization unit 32. The inner planetary gear 50 is then immobilized in rotation, which preserves the normal operation of the corresponding traction motor 20.

[0072] In one variant, the control and command functions of the control unit 27 are carried out by means of several units placed near or integrated into the equipment they control or from which they receive signals.

[0073] An example of the operation of the traction device 11 will now be described.

[0074] During the operation of the traction device 11, the control unit 27 continuously measures or continuously receives a measurement of the angular position and / or the rotational speed of each output shaft 40. Advantageously, the control unit 27 calculates the differences in rotational speed between the output shafts 40 of the traction motors 20 and / or the angular offsets between said output shafts 40.

[0075] Similarly, when the traction device 11 includes an immobilization unit 32, the control unit 27 continuously monitors (either directly or via signal reception) the presence of an anomaly on the traction motors 20 and / or control motor 24.

[0076] During the operation of the traction device 11, the immobilizing unit 32 is maintained in the first position as long as no anomaly is detected.

[0077] Initially, when the vehicle 10 is starting, the control unit 27 commands the starting of the control motor(s) 24 to compensate for angular and / or speed differences in the traction motors 20. The energy storage unit 26 then supplies energy to the control motor(s). In the example illustrated in the figure, the output member 60 of the control motor(s) 24 then drives the inner planetary gear 50 of the epicyclic gear train in rotation. Thus, during the starting phase, in addition to compensating for angular positions and speed differences, the control motors 24 contribute to the engine effort, thereby enabling improved acceleration characteristics or reducing the performance of the traction motors 20 without affecting the system's performance.

[0078] Then, when the vehicle 10 is in normal operating mode, the control unit 27 commands the control motor(s) 24 to switch to generator mode to produce energy and store said energy in the energy storage unit 26. In the example illustrated in the figure, the output member 60 of each control motor 24 is then driven in rotation by the inner planetary gear 50 of the epicyclic gear train. Thus, in normal operating mode, the control motors 24 act as a battery charger. Given the available power, it is possible to power functions other than those normally connected to it using the energy storage unit 26, which leads to improved availability of said functions.

[0079] Then, when the vehicle 10 is braking, the control unit 27 commands the control motor(s) 24 to switch to generator mode to store energy in the energy storage unit 26, thus assisting with braking. In the example shown in the figure, the output member 60 of each control motor 24 is then driven in rotation by the inner planetary gear 50 of the epicyclic gear train. Thus, during braking, the control motors 24 contribute to the braking effort and ensure electric braking down to zero km / h, regardless of the track conditions near the stopping point. The traction device 11 therefore eliminates the need for mechanical braking as long as the energy storage unit 26 has sufficient storage capacity available before braking.

[0080] In the event of a power failure of the traction motors 20, the control motors 24 provide emergency traction by being powered by the energy storage unit 26. The immobilizing unit 32 in the second position then immobilizes the rotor 40B of the traction motor 20 in rotation, which allows the transmission of the torque from the control motor 24 to the axle 12.

[0081] In the event of a failure of a traction motor 20, for example, a short circuit within the motor, the torque of the control motor 24 is at least significantly reduced relative to the torque of the assembly formed by the rotor 40B and the outer planetary gear 52, or even eliminated, thus preventing the transmission of motion from the axle 12 to the rotor 40B of the traction motor 20, as explained previously. The faulty motor can then be electrically disconnected without requiring equipment with a high breaking capacity. Such a system is fully reversible and allows for the temporary isolation of the traction motor 20.

[0082] When the control unit 27 detects or receives a fault signal indicating that one of the control motors 24 is not functional, the control unit 27 moves the corresponding immobilizing unit 32 into the third position to immobilize the rotor 60B of said control motor 24. Any other control motors 24 then replace the defective control motor 24 by compensating for the angular and / or speed differences between the traction motors 20, calculated by the control unit 27.

[0083] Thus, the traction device 11 allows the energy from the energy storage unit 26 to be used to power the control motors 24. Since the control motors 24 can operate in motor mode or generator mode in both directions of travel, the energy storage unit 26 can be recharged via the control motors 24. The control motors 24 are therefore controlled independently. The traction device 11 thus eliminates the need for a dedicated battery charger, which reduces the weight and size of the traction device 11 and helps to stabilize energy consumption.

[0084] Furthermore, in the event of a power failure to the traction motors 20, the associated control motors 24 can then be put into motor mode and be controlled to replace said traction motor 20. This makes it possible to improve the availability of the traction device 11 in the event of a power failure, in areas which are not equipped or in phases of operation in which the use of the power unit 44 is problematic, and this without requiring a battery with a dedicated charger.

[0085] The traction device 11 is also particularly suitable for operation with synchronous traction motors 20 due to the presence of the control motor(s) 24 intended to compensate for differences in angular positions and / or rotational speeds between the rotors 40B of said traction motors 20. Thus, this helps to simplify the traction device 11 and to reduce its weight and volume, as well as its energy efficiency.

[0086] Such a traction device 11 therefore has a reduced volume, weight and energy consumption and is capable of compensating for failures in the power supply of the traction motors 20.

[0087] A person skilled in the art will understand that the invention is not limited to the embodiment previously described.

[0088] For example, the traction device 11 could include more than two traction motors 20.

[0089] According to another variant, at least one of the traction motors 20 is not associated with a control motor 24.

[0090] In addition, the three elements of each epicyclic train can be connected interchangeably to either of the traction motor 20, axle 12 or corresponding control motor 24.

[0091] Finally, the sizing and energy management of the storage unit 26 can also meet different operational objectives than those previously described.

Claims

1. Assembly comprising: - a power supply unit, and - a traction device (11) for a vehicle (10), particularly for a railway vehicle, the device comprising: - at least two traction motors (20), each traction motor (20) comprising an output shaft (40), each traction motor (20) being supplied by the power supply unit, - for each traction motor (20), a transmission assembly (22) comprising elements, at least one of the elements being secured in rotation with the output shaft (40), - for at least one of the traction motors (20), an associated control motor (24), the or each control motor (24) being capable, in a motor mode, of rotating at least one of the elements of the corresponding transmission assembly (22), and, in a generator mode, of being driven in rotation by at least one of the elements of the corresponding transmission assembly (22), the control motor(s) (24) being intended to compensate for any differences in angular positions and / or in rotational speeds of the traction motors (20), - an energy storage unit (26) capable of exchanging energy with the or each control motor (24), the energy storage unit (26) being different from the power supply unit (44), and - an instrumentation and control unit (27) of the or each control motor (24), capable of receiving at least one control signal and of controlling the or each control motor (24) according to the at least one control signal.

2. Assembly according to claim 1, wherein when the or one of the control motors (24) is controlled in a motor mode, the energy storage unit (26) supplies energy to said control motor (24), and when the or one of the control motors (24) is controlled in a generator mode, the energy storage unit (26) receives energy from said control motor (24).

3. Assembly according to claim 1 or 2, wherein each transmission assembly (22) is a planetary gear train, each planetary gear comprising first, second and third elements, selected from among an inner sun gear (50), an outer sun gear (52), and a planet carrier (54) carrying at least one planetary gear meshing with the inner sun gear (50) and with the outer sun gear (52), the first element being secured in rotation with the output shaft (40) of the corresponding traction motor (20), the second element being capable of driving a respective axle (12) of the vehicle (10) in rotation, the third element being configured to be secured in rotation with an output shaft of the corresponding control motor (24).

4. Assembly according to claim 3, wherein, for at least one planetary gear train, the first element is the outer sun gear (52), the second element is the planet carrier (54) and the third element is the inner sun gear (50).

5. Assembly according to any one of claims 1 to 4, wherein each of the traction motors (20) and the control motor(s) (24) comprises a stator (40A, 60A) and a rotor (40B, 60B) movable in rotation relative to the stator (40A, 60A), the traction device (11) comprising an immobilisation unit (32) for at least one of the traction motors (20) associated with a control motor (24), the immobilisation unit (32) being movable according to at least two positions: a first position wherein the rotors (40B, 60B) of the corresponding traction motors (20) and control motors (24) are free and a second position wherein only the rotor (40B) of the corresponding traction motor (20) is immobilised, the instrumentation and control unit (27) being capable of detecting a lack of power supply of the traction motors (20) corresponding to a stoppage of the traction motors, the instrumentation and control unit (27) being, also, capable of holding the immobilisation unit (32) in the first position when the instrumentation and control unit (27) does not detect a lack of power supply of the corresponding traction motor (20), and of switching the immobilisation unit (32) into the second position when the instrumentation and control unit (27) detects a lack of power supply of the corresponding traction motor (20).

6. Assembly (11) according to claim 5, wherein the immobilisation unit (32) is, furthermore, movable according to a third position in which only the rotor (60B) of the corresponding control motor (24) is immobilised, the instrumentation and control unit (27) being, furthermore, capable of detecting an anomaly or receiving an anomaly signal for each control motor (24), and capable of switching the immobilisation unit (32) into the third position when an anomaly of the corresponding control motor (24) is detected.

7. Assembly according to any one of claims 1 to 6, wherein the instrumentation and control unit (27) is capable of measuring or receiving a measurement of an angular position and / or a rotational speed of the output shaft (40) of each traction motor, and of controlling each control motor (24) according to a desired rotational speed of the corresponding element of the transmission assembly (22), said desired rotational speed being established according to the angular position and / or the rotational speed measured for the output shaft (40) of each traction motor.

8. Assembly according to any one of claims 1 to 7, wherein the instrumentation and control unit (27) is capable of detecting an anomaly or receiving an anomaly signal for each traction motor (20) and reducing the torque applied by the associated control motor (24) when an anomaly of the associated traction motor (20) is detected.

9. Assembly according to claim 8, wherein the instrumentation and control unit (27) is also capable of increasing the torque applied by each control motor (24) to activate force transmission between the associated traction motor (20) and an axle intended to be moved by said traction motor (20).

10. Assembly according to any one of claims 1 to 9, wherein the traction device (11) comprising a single converter (46) connected between the power supply unit (44) and several of the traction motors (20).

11. Assembly according to any one of claims 1 to 10, wherein the traction motors (20) are synchronous motors, preferably permanent magnet motors.

12. Vehicle (10), particularly a railway vehicle, comprising: - at least two axles (12), and - at least one traction device (11) of an assembly according to any one of claims 1 to 11, wherein each transmission assembly (22) is kinematically linked to a separate axle (12).