Propulsion system for electric vehicles

Abstract

A propulsion system (1) for an electric vehicle, comprising: an assembly of four electric propulsion machines (2), each comprising a stator and a rotor having an output shaft capable of rotational motion about an axis; a common gear (11) kinematically connected to the n output shafts and capable of receiving the torque supplied by the electric machines (2) so as to form a first reduction, main gears capable of being driven by the common gear (11), an intermediate shaft (12) capable of being driven by intermediate gears, each main gear being kinematically connected to a corresponding intermediate gear so as to form a pair of gears associated with a second reduction, a secondary shaft (13) capable of driving the vehicle and having a secondary gear kinematically connected to the intermediate shaft (12) so as to form a third reduction.

Description

TECHNICAL FIELD

[0001] The present invention relates to a propulsion system for an electric vehicle. Such a propulsion system notably comprises a plurality of electric propulsion machines providing driving torque, a series of gear trains and a separate selective coupling system able to provide a plurality of reduction ratios and a plurality of separate operating modes for a user of the vehicle.

[0002] Such a vehicle has pure electric propulsion, without a propulsion combustion engine. The electric vehicle can be a motor vehicle or an industrial vehicle, such as a heavy goods vehicle, a bus or a tractor. BACKGROUND

[0003] Such a propulsion system is known, for example, from patent application WO 17080571 A1. The propulsion system according to this patent application comprises a first electric machine and a second electric machine, and a transmission arranged to transmit torque from said electric machines to a pair of driven wheels of a vehicle. The first electric machine is drivingly connected to a first input shaft of the transmission, and the second electric machine is drivingly connected to a second input shaft of the transmission. This propulsion system is characterized by a first torque path which can transmit torque, comprising a single transmission ratio between a first input shaft and an output shaft of the transmission, and a second torque path which can transmit torque, comprising two selectable and separately engageable transmission ratios between a second input shaft and said output shaft of the transmission, the three transmission ratios of the first torque path and of the second torque path being different from each other.

[0004] Such a propulsion system is limited in that the electric machines cannot be operated at the same operating speed since they are located on two different torque paths, thereby complicating the control of the electric machines.

[0005] There is a need to further improve an electric vehicle propulsion system comprising a plurality of electric machines and having a plurality of reduction ratios. SUMMARY

[0006] The present invention aims to meet this need, and according to one of its aspects, this is achieved by means of a propulsion system for an electric vehicle, comprising:

[0007] a set of n electric propulsion machines, n being an integer greater than or equal to 3, each electric propulsion machine comprising a stator and a rotor having an output shaft capable of rotational movement about an axis;

[0008] a common gear connected kinematically to the n output shafts and capable of receiving driving torque provided by the n electric propulsion machines, the n electric propulsion machines being angularly distributed around the common gear so as to form a first reduction gear,

[0009] The propulsion system comprises:

[0010] primary gears, the primary gears being drivable by the common gear;

[0011] intermediate shafts, the intermediate shafts being drivable by intermediate gears, each primary gear being kinematically connected to a corresponding intermediate gear so as to form a pair of gears associated with a second reduction;

[0012] a secondary shaft, the secondary shaft being drivable by a component of one or more drive wheels of the vehicle and having a secondary gear kinematically connected to the intermediate shaft so as to form a third reduction;

[0013] wherein a first selective coupling system, disposed between the common gear and the primary gears or alternatively between the intermediate shafts and the intermediate gears, selects either the first pair of gears or the second pair of gears from a neutral position.

[0014] The angular distribution of the n electric propulsion machines around the common gear allows the propulsion system to be installed with a smaller axial footprint.

[0015] More particularly, the secondary shaft can have a secondary gear kinematically connected to the intermediate shaft by an intermediate gear so as to form a third reduction. For example, the intermediate gear is separate from those gears associated with the second reduction. The secondary shaft can have, for example, three axially aligned intermediate gears.

[0016] Preferably, the n electric propulsion machines are similar, for example wound-rotor or permanent-magnet synchronous electric propulsion machines. In variants, the electric propulsion machines can be, for example, asynchronous machines. The use of a plurality of similar electric propulsion machines can reduce production costs and facilitate the control of the electric propulsion machines.

[0017] In the meaning of the present application:

[0018] a coupling system that couples two components is selective when it allows the two components to be coupled or uncoupled according to instructions received,

[0019] a coupling system that couples two components and is non-selective permanently couples the two components,

[0020] the two components coupled by one of the above-mentioned coupling systems are fixed to each other so that they rotate integrally. In the case where the coupling system employs a dog clutch, this fixing can correspond to a torque lock, and in the case where the coupling system employs a clutch, this fixing can employ a friction drive, and

[0021] “upstream” and “downstream” are defined with respect to the direction of transmission of torque from the electric propulsion machines to the wheels of the vehicle.

[0022] Preferably, based on a drive torque C0 delivered by the n electric propulsion machines, the countershaft is able to selectively receive: a torque C1 that has been transmitted through the first pair of gears, or a torque C2 that has been transmitted through the second pair of gears, such that C1 > C2.

[0023] Advantageously, a first ratio between the drive torque C0 and the torque C1 that has been transmitted through the first pair of gears can be between 10 and 15, such that 10 < C0 / C1 < 15, and a second ratio between the drive torque C0 and the torque C2 that has been transmitted through the second pair of gears can be between 5 and 10, such that 5 < C0 / C2 < 10.

[0024] Preferably, the n electric propulsion machines can be regularly distributed around the rotation axis of the common gear at an angle D equal to 360° / n.

[0025] Each electric propulsion machine can be configured to operate reversibly, in which case it is associated with electronic equipment such as an inverter / rectifier, allowing it to alternate between being supplied with electrical energy in order to provide a drive torque, and generating electrical energy based on the torque received on its shaft, for example when the vehicle is braking or when the vehicle is starting while rolling.

[0026] Each electric propulsion machine is, for example, a rotary electric propulsion machine.

[0027] Each electric propulsion machine can be configured to operate reversibly, in which case it is associated with electronic equipment such as an inverter / rectifier, allowing it to alternate between being supplied with electrical energy in order to provide a drive torque, and generating electrical energy based on the torque received on its shaft, for example when the vehicle is braking or when the vehicle is starting while rolling.

[0028] The n electric propulsion machines can provide the same mechanical nominal power, for example between 50 kW and 150 kW, for example possibly equal to 120 kW. Using identical electric propulsion machines can reduce the production cost of the propulsion system by reducing the specific development needs from one machine to another and by increasing the volume.

[0029] The propulsion system can comprise a transmission shaft equipped with a universal joint connecting the countershaft to a differential. The differential can be a mechanical differential or an electronic differential controlling the output torque fed to each drive wheel of the vehicle. In particular, the differential can be arranged to selectively receive: a torque C1 that has been transmitted through the first pair of gears, or a torque C2 that has been transmitted through the second pair of gears, such that C1 > C2. The differential can be associated with the rear axle of the vehicle. In variants, the differential can be kinematically connected directly to the countershaft. In this way, the axial footprint of the propulsion system can be reduced.

[0030] Preferably, the propulsion system can comprise a transmission housing supporting the n electric propulsion machines and the common gear by means of at least one guide bearing. Since the n electric propulsion machines are angularly distributed around the common gear, the transmission housing is subjected to more evenly distributed mechanical stresses.

[0031] Advantageously, the transmission housing can comprise a fluid circulation circuit passing between the n electric propulsion machines in order to evacuate the thermal energy emitted during the torque transmission.

[0032] Preferably, the rotation axis of the common gear, the axis of the intermediate shaft and the axis of the layshaft can be parallel.

[0033] Advantageously, the layshaft can be driven by the secondary gearwheel by means of a second selective coupling system. In this way, it is possible to disconnect the propulsion system from the wheels of the vehicle. The propulsion system and in particular the electric propulsion machines are thus protected.

[0034] Preferably, the second selective coupling device can take the form of a dog clutch or a synchronizer.

[0035] According to a first embodiment variant of the application, the first selective coupling system arranged between the common gear and the primary gear takes the form of a dog clutch or a synchronizer.

[0036] According to a second embodiment variant of the application, the first selective coupling system arranged between the common gear and the primary gear takes the form of a dual clutch, in particular a dual wet clutch.

[0037] Preferably, the dual wet clutch can have a radial architecture in which the first multi- disc clutch and the second multi-disc clutch are arranged one above the other radially from one another, the dual wet clutch comprising a torque transmission housing which is common to the first multi-disc clutch and to the second multi-disc clutch and is fixed so as to rotate integrally with the common gear.

[0038] In a variant, the dual wet clutch can have an axial architecture in which the first multi- disc clutch and the second multi-disc clutch are arranged one next to the other axially from one another, the dual wet clutch comprising a torque transmission housing which is common to the first multi-disc clutch and to the second multi-disc clutch and is fixed so as to rotate integrally with the common gear.

[0039] Advantageously, the common gear can circumferentially surround the torque transmission housing.

[0040] Advantageously, the transmission housing can directly support the torque transmission housing and supply fluid to the first multi-disc clutch and to the second multi-disc clutch.

[0041] According to a third embodiment variant of the application, the first selective coupling system arranged between the intermediate shaft and the intermediate gear takes the form of a dog clutch or a synchronizer.

[0042] Throughout the foregoing, when the propulsion system comprises a first selective coupling system and a second selective coupling system, the propulsion system can further comprise control means for controlling the first selective coupling system and the second selective coupling system, so that the propulsion system can adopt all or some of the following configurations:

[0043] a configuration according to which the layshaft receives the torque C1 transmitted through the first pair of gears, the first selective coupling system being in the first coupling position and the second selective coupling system being in the coupled position,

[0044] a configuration according to which the layshaft receives the torque C2 transmitted through the second pair of gears, the first selective coupling system being in a second coupling position different from the first position and the second selective coupling system being in the coupled position, and

[0045] a maintenance configuration in which the first coupling system and the second coupling system are in the decoupled neutral position.

[0046] The control means can for example be incorporated into the vehicle processor (ECU). In a variant, the control means can be incorporated into the transmission control unit (TCU). In a further variant, the control means can be modular and the control module for controlling the first coupling system is incorporated into the transmission control unit, while the control module for controlling the second coupling system is incorporated into the ECU. BRIEF DESCRIPTION OF DRAWINGS

[0047] Further features and advantages of the application will become apparent on reading the description that follows, with reference to the attached drawings.

[0048] Figure 1 is a front view of a propulsion system for an electric vehicle according to a first embodiment example of the application,

[0049] Figure 2 is a front view of a propulsion system for an electric vehicle according to a second embodiment example of the application, Figure 1 is a partial isometric view of the propulsion system of

[0050] Figure 3 shows a propulsion system according to a third embodiment example of the application,

[0051] Figure 4 shows a propulsion system according to a fourth embodiment example of the application.

[0052] Figure 5 shows a propulsion system according to a fourth embodiment example of the application.

[0053] For greater clarity, in all the figures, the same reference numbers have been used to identify the same or similar elements. DETAILED DESCRIPTION

[0054] Figure 1 and Figure 2 A propulsion system 1 for an electric vehicle V according to a first embodiment example of the application is shown.

[0055] Here, this propulsion system 1 is purely electric, that is to say it does not use a combustion engine to drive the vehicle, which in this case is an industrial vehicle, for example a heavy goods vehicle. This propulsion system 1 comprises an assembly of n electric propulsion machines 2, n being an integer greater than or equal to 3, each comprising a stator and a rotor having an output shaft that can rotate about an axis of rotation. In the example described, the electric propulsion machines are rotary electric propulsion machines. Figure 1 and Figure 2 In the first embodiment example of the application shown, the assembly comprises four electric propulsion machines 2a, 2b, 2c and 2d.

[0056] The rotary electric propulsion machines 2a, 2b, 2c, 2d are of the same type and are for example permanent magnet synchronous machines. Each electric propulsion machine provides the same mechanical nominal power, which is of the order of 100 kW for example. In variants, these electric propulsion machines can be for example asynchronous machines.

[0057] As can be seen in Figure 2 In the example described, the first electric propulsion machine 2a has a rotor with a first output shaft that rotates about a first axis of rotation XI, the second electric propulsion machine 2b has a rotor with a second output shaft that rotates about a second axis of rotation X2, the third electric propulsion machine 2c has a rotor with a third output shaft that rotates about a third axis of rotation X3, and the fourth electric propulsion machine 2d has a rotor with a fourth output shaft that rotates about a fourth axis of rotation X4. In the example described, the axes of rotation of the rotary electric propulsion machines are parallel but do not coincide, the axes of rotation of the four electric propulsion machines 2a, 2b, 2c, 2d are not aligned.

[0058] The four electric propulsion machines are regularly distributed at an angle Δ equal to 90° around the common gear's axis of rotation.

[0059] The output shafts of the four electric propulsion machines are simultaneously engaged with a common gear 11 arranged inside the axes XI, X2, X3 and X4. The common gear 11 is kinematically connected to the four output shafts and receives the driving torques CO provided by the four electric propulsion machines, which are angularly distributed around the common gear so as to form first reducers Zl, Z2.

[0060] The transmission housing 3 supports the four electric propulsion machines and the common gear 11 by means of guide bearings 15. The guide bearings can be roller bearings or ball bearings. The transmission housing 3 notably comprises a central core 3a located at the center of the electric propulsion machines. The central core 3a comprises a fluid circulation circuit 4 passing between the four electric propulsion machines in order to evacuate the thermal energy emitted during the transmission of the torque within the propulsion system. The fluid can be a cooling oil or an aqueous solution.

[0061] The propulsion system 1 comprises primary gears Z3, Z5 that can be driven by the common gear by means of a first selective coupling system 10. The first selective coupling system 10, provided between the common gear 11 and the primary gears Z3, Z5, can select the first pair of gears Z3, Z4 or the second pair of gears Z5, Z6 from a neutral position of disengaged coupling. This first selective coupling system 10 with three positions takes the form of a dog clutch. In a variant, the first coupling system can comprise two coupling sub-assemblies, a first coupling sub-assembly associated only with the first pair of gears Z3, Z4 and a second coupling sub-assembly associated only with the second pair of gears Z5, Z6. In a variant, the coupling system can take the form of a synchronizer.

[0062] The propulsion system 1 comprises an intermediate shaft 12 that can be driven by intermediate gears Z4, Z6 and Z7, each primary gear Z3, Z5 being kinematically connected to a corresponding intermediate gear Z4, Z6 in order to form a pair of gears associated with a second reduction. The intermediate shaft 12 is rotationally supported by a housing attached to the transmission housing 3 by means of guide bearings 14.

[0063] The propulsion system 1 also comprises a lay shaft 13 that can drive an assembly of one or more drive wheels of the vehicle. The lay shaft 13 has a lay gear Z8 that is kinematically connected to the intermediate shaft 12 by means of the intermediate gear Z7 in order to form a third reduction Z7, Z8.

[0064] In this first embodiment example of the application, the rotation axis 110 of the common gear 11, the rotation axis 120 of the intermediate shaft 12 and the rotation axis 130 of the lay shaft 13 are parallel.

[0065] Depending on the configuration of the first selective coupling system 10 for selecting the first pair of gears Z3, Z4 or the second pair of gears Z5, Z6, the lay shaft 13 receives different torque values. Based on the drive torque Co transmitted by the four electric propulsion machines, the lay shaft selectively receives: a torque Ci that has been transmitted by the first pair of gears, or a torque C2 that has been transmitted by the second pair of gears, such that Ci > C2.

[0066] Advantageously, a first ratio between the drive torque C0 and the torque C1 that has been transmitted through the first pair of gears Z3, Z4 can be between 10 and 15, such that 10 < C0 / C1 < 15, and a second ratio between the drive torque C0 and the torque C2 that has been transmitted through the second pair of gears Z5, Z6 can be between 5 and 10, such that 5 < C0 / C2 < 10.

[0067] As an indication, in the case of an industrial vehicle, the first ratio can be equal to 10.5 and the second ratio can be equal to 6.

[0068] As Figure 1 As shown, a propeller shaft 6 equipped with a universal joint connects the countershaft 13 to the differential 7. The differential 7 can be a mechanical differential or an electronic differential that controls the output torque fed to each drive wheel of the vehicle. In particular, the differential can be arranged to selectively receive: the torque C1 that has been transmitted through the first pair of gears Z3, Z4, or the torque C2 that has been transmitted through the second pair of gears Z5, Z6.

[0069] Now, the transition phase of the propulsion system 1 to a higher reduction ratio will be described.

[0070] During the operating phase of the electric vehicle V between times t0 and t1, it is considered that the first reduction ratio is engaged and the first selective coupling system 10 is considered to be in the first coupling position, in which the first pair of gears Z3, Z4 is selected.

[0071] Between times t1 and t2, the propulsion system transfers from the engaged position to the neutral position, at which time the dog clutch disengages. The first selective coupling system 10 is now in the disengaged neutral position. To prepare for the engagement of the dog clutch in the second coupling position, the relative rotational speed between the common gear 11 and the main gear Z5 is measured by using various speed sensors present in the propulsion system 1. During this phase, the electric propulsion machine no longer provides torque.

[0072] Between times t2 and t3, the reversible electric propulsion machine 2 is enabled to decelerate the common gear 11, so as to synchronize the rotational speed of the common gear 11 and the rotational speed of the main gear Z5.

[0073] Between times t3 and t4, the dog clutch engages to couple the common gear to the associated main gear when the rotational speeds of the common gear 11 and the associated main gear Z5 are synchronized. When the first selective coupling system 10 is in the second coupling position in which the second pair of gears Z5, Z6 is selected, the second reduction ratio is engaged.

[0074] After time t4, the electric propulsion machine provides torque again.

[0075] Because of the use of the reversible electric propulsion machine 2, the chuck engagement and disengagement time can be reduced without the need for a gearbox brake.

[0076] The transition phase of propulsion system 1 changing to a lower reduction ratio will now be described.

[0077] During the operation phase of the electric vehicle V between time t0 and t1, it is assumed that the second reduction ratio is engaged and the first selective coupling system 10 is considered to be in the second coupling position, in which the second pair of gears Z5, Z6 are selected.

[0078] Between times t1 and t2, the propulsion system shifts from the engaged position to the neutral position, at which point the claw clutch disengages. The first selective engagement system 10 is now in the disengaged neutral position. To prepare for the engagement of the claw clutch 10 in the first engagement position, the relative rotational speed between the common gear 11 and the main gear Z3 is measured using various speed sensors present in the propulsion system. During this phase, the electric propulsion machine no longer provides torque.

[0079] Between time t2 and t3, the reversible electric propulsion machine 2 is activated to accelerate the common gear 11, thereby synchronizing the rotational speed of the common gear 11 with the rotational speed of the main gear Z3.

[0080] Between times t3 and t4, the claw clutch engages to connect the common gear to the associated primary gear when the rotational speed of the common gear 11 and the rotational speed of the associated primary gear Z3 are synchronized. When the first selective coupling system 10 is in the first coupling position where the first pair of gears Z3, Z4 is selected, the first reduction ratio is engaged.

[0081] After time t4, the electric propulsion machine provides torque again.

[0082] Because of the use of the reversible electric propulsion machine 2, the chuck engagement and disengagement time can be reduced without the need for a gearbox brake.

[0083] In this first embodiment of the invention, the secondary shaft 13 can be driven by the secondary gear Z8 via a second selective coupling system 20. In this way, the propulsion system can be disconnected from the vehicle's wheels. This second selective coupling device can take the form of a claw clutch or a synchronizer.

[0084] Figure 3 A second embodiment of the invention is shown, which differs from the first embodiment in that the first selective coupling system 10 is positioned between the intermediate shaft 12 and the intermediate gears Z4, Z6. The advantage of this arrangement is that it allows the selective coupling system to be offset and facilitates the integration of its control equipment into the propulsion system.

[0085] The operation of this second embodiment is similar to that of the first embodiment of the invention because the structure of the propulsion system 1 remains unchanged. The common gear 11 is still kinematically connected to the four output shafts and receives the drive torque C0 provided by the four electric propulsion machines, which are angularly distributed around the common gear to form the first reducers Z1, Z2.

[0086] During the transition phase to a lower or higher reduction ratio, the rotational speeds of the intermediate gears Z4 and Z6 and the intermediate shaft 12 are still synchronized by accelerating or decelerating the common gear 11, but taking into account the reduction ratio of the first pair of gears or the reduction ratio of the second pair of gears.

[0087] In this second embodiment of the invention, the secondary shaft 13 is driven by the secondary gear Z8 via a second selective coupling system 20. In this way, the propulsion system can be disconnected from the vehicle's wheels. This second selective coupling device takes the form of a claw clutch.

[0088] The propulsion system also includes a control component 50 for controlling the first selective coupling system 10 and the second selective coupling system 20 when they are present. The control component 50 is programmed such that the propulsion system can be configured as follows:

[0089] Configuration (i), according to which the secondary shaft 13 receives torque C1 transmitted via the first pair of gears, the first selective coupling system 10 is in the first coupled position and the second selective coupling system 20 is in the coupled position.

[0090] Configuration (ii), according to which the secondary shaft 13 receives torque C2 transmitted via the second pair of gears, the first selective coupling system 10 is in a second coupling position different from the first position, and the second selective coupling system 20 is in the coupling position, and

[0091] Maintenance configuration (iii), in which the first connection system and the second connection system are in a disconnected neutral position.

[0092] The control of the connection system implemented by the control element 50 to obtain the above configurations (i) to (iii) is shown in the table below.

[0093]

[0094] Configuration (i) is suitable, for example, for low vehicle speeds where high torque is required.

[0095] Configuration (ii) is suitable for high vehicle speeds, for example, where low torque is required.

[0096] Configuration (iii) is, for example, suitable for operation as a maintenance mode, in which the vehicle's wheels can rotate without driving the propulsion system.

[0097] Figure 4 A third embodiment of the invention is shown, which differs from the first embodiment in that the first selective coupling system 10 is disposed between the common gear and the main gear and adopts a dual clutch, particularly a dual wet clutch. The advantage of this dual wet clutch is that it eliminates the need for synchronization of the rotational speeds of the common gear 11 and the main gears Z3 and Z5.

[0098] The dual wet clutch has a radial configuration in which a first multi-disc clutch E1 and a second multi-disc clutch E2 are arranged radially above and below each other. More specifically, in this example, the first multi-disc clutch E1 is arranged radially around the second multi-disc clutch E2. The torque transmission housing 40 shared by the first multi-disc clutch E1 and the second multi-disc clutch E2 is fixed and rotates integrally with a common gear 11.

[0099] The first multi-plate clutch E1 is associated with the first pair of gears Z3 and Z4, while the second multi-plate clutch E2 is associated with the second pair of gears Z5 and Z6. The neutral position, where the engagement is broken, is obtained by simultaneously disengaging both clutches.

[0100] Advantageously, the first multi-disc clutch E1, radially arranged around the second multi-disc clutch E2, is associated with a first ratio between the drive torque C0 and the torque C1 already transmitted through the first pair of gears Z3, Z4. The second multi-disc clutch E2 is associated with a second ratio between the drive torque C0 and the torque C2 already transmitted through the second pair of gears Z5, Z6.

[0101] Figure 5 A fourth embodiment of the invention is shown, which differs from the third embodiment in that a common gear 11 circumferentially surrounds a torque transmission housing 40. In this fourth embodiment, the torque transmission housing 40, shared by the first and second multi-disc clutches, is fixed and rotates integrally with the common gear 11. For example, the common gear 11 is attached to the torque transmission housing 40 or directly machined onto the housing 40.

[0102] Advantageously, the transmission housing 3 directly supports the torque transmission housing 40 and supplies fluid to the first and second multi-plate clutches, particularly to the control chambers of clutches E1 and E2. A pressurized fluid supply conduit 41 leading to the transmission housing 3 passes through the torque transmission housing 40 and extends axially through the guide bearing 15.

[0103] In a variant, the dual wet clutch can have an axial configuration in which a first multi-disc clutch E1 and a second multi-disc clutch E2 are axially adjacent to each other, and in which a torque transmission housing shared by the first and second multi-disc clutches is fixed and rotates integrally with a common gear. In this variant, the common gear circumferentially surrounds the torque transmission housing.

[0104] The present invention is not limited to the examples already described.

Claims

1. A propulsion system (1) for an electric vehicle, the propulsion system comprising: A component of n electric propulsion machines (2), where n is an integer greater than or equal to 3, each electric propulsion machine comprising a stator and a rotor, the rotor having an output shaft capable of rotational movement about an axis; A common gear (11) kinematically connected to the n output shafts and capable of receiving a driving torque C0 provided by the n electric propulsion machines (2), the n electric propulsion machines being angularly distributed around the common gear so as to form a first reduction gear (Z1, Z2); The propulsion system comprises: A main gear (Z3, Z5) capable of being driven by the common gear (11); An intermediate shaft (12) capable of being driven by intermediate gears (Z4, Z6, Z7), each main gear (Z3, Z5) being kinematically connected to a corresponding intermediate gear (Z4, Z6, Z7) so as to form a pair of gears associated with a second reduction gear; A secondary shaft (13) capable of driving a component of one or more drive wheels of the vehicle and having a secondary gear (Z8) kinematically connected to the intermediate gear of the intermediate shaft (12) so as to form a third reduction gear; Wherein a first selective coupling system (10) provided between the common gear (11) and the main gear or alternatively between the intermediate shaft (12) and the intermediate gear selects a first pair of gears or a second pair of gears from a neutral position.

2. The propulsion system according to claim 1, wherein, Based on the driving torque C0 transmitted by the n electric propulsion machines, the secondary shaft (13) can selectively receive: the torque C1 that has been transmitted through the first pair of gears, or the torque C2 that has been transmitted through the second pair of gears, such that C1 > C2.

3. The propulsion system according to claim 2, wherein, A first ratio between the driving torque C0 and the torque C1 that has been transmitted through the first pair of gears is between 10 and 15, such that 10 < C0 / C1 < 15, and a second ratio between the driving torque C0 and the torque C2 that has been transmitted through the second pair of gears is between 5 and 10, such that 5 < C0 / C2 < 10.

4. The propulsion system according to any one of claims 1 to 3, wherein, The n electric propulsion machines (2) are regularly distributed at an angle Δ equal to 360° / n around the axis of rotation (110) of the common gear.

5. The propulsion system according to claim 4, comprising a transmission housing (3), the transmission housing supporting the n electric propulsion machines (2) and the common gear (11) by means of at least one guiding bearing (15).

6. The propulsion system according to claim 5, wherein, The transmission housing (3) comprises a fluid circulation circuit (4) passing between the n electric propulsion machines (2) in order to discharge the thermal energy generated during torque transmission.

7. The propulsion system according to claim 1, wherein, The axis of rotation (110) of the common gear (11), the axis (120) of the intermediate shaft (12) and the axis (130) of the secondary shaft (13) are parallel.

8. The propulsion system according to claim 1, comprising a transmission shaft (6) equipped with a universal joint, the transmission shaft connecting the secondary shaft (13) to a differential (7).

9. The propulsion system according to claim 1, wherein, The n electric propulsion machines (2) provide the same nominal mechanical power.

10. The propulsion system according to claim 9, wherein, The nominal power of the machine is between 50kW and 150kW.

11. The propulsion system according to claim 1, wherein, The first selective coupling system (10) disposed between the common gear and the main gear takes the form of a claw clutch or a synchronizer.

12. The propulsion system according to claim 1, wherein, The first selective coupling system (10) located between the common gear (11) and the main gear employs a dual clutch.

13. The propulsion system according to claim 12, wherein, The first selective coupling system (10) disposed between the common gear (11) and the main gear is in the form of a dual wet clutch.

14. The propulsion system according to claim 1, wherein, The secondary shaft (13) is driven by the secondary gear (Z8) via a second selective coupling system (20).

15. The propulsion system according to claim 14, wherein, The second selective coupling system (20) takes the form of a claw clutch or synchronizer.

16. The propulsion system according to claim 13, wherein, The dual wet clutch has a radial structure, wherein the first multi-disc clutch and the second multi-disc clutch (E1, E2) are arranged radially above and below each other. The dual wet clutch includes a torque transmission housing (40), which is shared by the first multi-disc clutch and the second multi-disc clutch and is fixed to rotate integrally with the shared gear (11).

17. The propulsion system according to claim 1, wherein, The secondary shaft (13) is driven by the secondary gear (Z8) via the second selective coupling system (20). The propulsion system includes a control component (50) for controlling the first selective coupling system (10) and the second selective coupling system (20), such that the propulsion system (1) can employ all or some of the following configurations: - Configuration (i), according to the configuration, the secondary shaft (13) receives torque C1 transmitted through the first pair of gears, the first selective coupling system (10) is in a first coupling position and the second selective coupling system (20) is in a coupling position. - Configuration (ii), according to the configuration, the secondary shaft (13) receives torque C2 transmitted via the second pair of gears, the first selective coupling system (10) is in a second coupling position different from the first coupling position, and the second selective coupling system (20) is in the coupling position, and - Maintenance configuration (iii), in which the first selective connection system (10) and the second selective connection system (20) are in a disconnected neutral position.

18. The propulsion system of claim 16, wherein the common gear circumferentially surrounds the torque transmission housing.

19. The propulsion system according to claim 16, comprising a transmission housing (3) supporting the n electric propulsion machines (2) and the common gear (11) by means of at least one guide bearing (15), the transmission housing directly supporting the torque transmission housing and supplying fluid to the first multi-disc clutch and the second multi-disc clutch.

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