Propulsion system of an electric or hybrid vehicle

Abstract

Propulsion assembly (2) of a hybrid or electric vehicle, comprising: - an electric propulsion module (3), comprising: an electric propulsion machine, a voltage converter supplying this electric machine, and a gearbox coupled to the electric machine, this module being suitable for mounting on an axle (1) of the vehicle so that the output of the gearbox provides a motor torque to this axle, and - a control system (6) configured to automatically activate the electric propulsion module (3) so that it provides a motor torque to the axle (1) when at least one of the following conditions is detected by this system (6): - detection of a turn in the vehicle's path, and - detection of a loss of vehicle traction on the ground. [Fig. 1]

Description

Title of the invention: Propulsion assembly for an electric or hybrid vehicle

[0001] The present invention relates to a propulsion assembly for an electric or hybrid vehicle, as well as a powertrain integrating such an assembly.

[0002] It is known to have one or more electric propulsion modules on a rear axle of a hybrid or electric vehicle to make this rear axle a driving axle. The user of the vehicle can then, by activating this electric propulsion module, have an all-wheel drive, the four wheels of the vehicle being driven given that the front axle is already driven by a thermal engine and / or an additional electric propulsion motor. However, the use of such an all-wheel drive is energy-intensive, which goes against the need to reduce CO2 emissions and / or to reduce the waste of resources.

[0003] There is a need to have an electric or hybrid vehicle propulsion system that overcomes the aforementioned drawback.

[0004] The invention aims to meet this need and achieves this, according to one of its aspects, using a propulsion assembly for a hybrid or electric vehicle, comprising:

[0005] - an electric propulsion module, comprising: an electric machine of propulsion, a voltage converter supplying this electric machine, and a reducer coupled to the electric machine, this module being capable of being mounted on an axle of the vehicle so that the output of the reducer provides a motor torque to this axle, and

[0006] - a control system configured to automatically activate the module of electric propulsion so that it provides engine torque to the axle when at least one of the following conditions is detected by this system:

[0007] - detection of a turn in the vehicle's path, and

[0008] - detection of a lack of adhesion of the vehicle to the ground.

[0009] According to the invention, the electric propulsion module is thus not activated at the discretion of the user of the vehicle, but automatically when one or more predefined conditions are detected, these predefined conditions comprising as mentioned above: the detection of a bend in the path of the vehicle and the detection of a lack of grip of the vehicle on the ground. Other conditions are possible such as a regenerative mode or a “boost” mode.

[0010] The control system may be external to the propulsion module. The control system is for example integrated into a vehicle control device, also called a “vehicle control unit” (VCU) in English. The control system is for example example contained in a single case.

[0011] As a further variant, the control system is distributed between several entities. These entities may or may not be positioned together. An entity of the control system, for example an entity detecting a lack of adhesion, may be integrated into the electric propulsion module, while an entity of this control system, for example the one activating the electric propulsion module so that it provides a motor torque to the axle, is integrated into the control device of the aforementioned vehicle.

[0012] The control system comprises, for example, a digital processing unit implementing one or more microcontrollers. The detection of one of the predefined conditions may or may not be carried out by means of a neural network or a Bayesian network.

[0013] The control system can detect a turn in the vehicle's path based on at least one of the following data: value of the vehicle's steering angle, value of the vehicle's yaw angle and vehicle speed. These different values ​​are for example received and analyzed by the control system.

[0014] Alternatively or in combination, this detection of a turn in the vehicle's route can be carried out using geolocation data of the vehicle, data transmitted for example by a mobile telephone network, for example 3G, 4G or 5G. The position of the vehicle can thus be compared, in particular by the control system or by a remote system, to the route taken by the vehicle, so that turn detection is possible.

[0015] The control system can detect a lack of grip of the vehicle on the ground depending on the value of the vehicle's grip coefficient. This grip coefficient is defined in a known manner as the ratio between the braking (or steering) force of the vehicle and the weight of this vehicle. The lack of grip is for example detected when this grip coefficient falls below a threshold value. Other ways of detecting a lack of grip of the vehicle on the ground are possible.

[0016] The control system is for example configured to automatically deactivate the electric propulsion module when the condition is no longer detected, where appropriate after a time delay. This time delay is for example of the order of a few seconds, either after the detection of the exit from the bend, or after the last detection of a grip coefficient value below the threshold value. The automatic deactivation of the propulsion module when the condition is no longer detected makes it possible to use this electric propulsion module only in targeted cases, and therefore to reduce the consumption of electrical energy necessary for the operation of this electric propulsion module.

[0017] In all of the above, the electric propulsion module may comprise a first housing part receiving the electric propulsion machine and the voltage converter, and a second housing part receiving the reduction system and containing oil.

[0018] The reduction system comprises, for example, several pinions and the oil makes it possible to lubricate these pinions.

[0019] When the electric propulsion module comprises such a first and second housing part, a cooling circuit for the electric propulsion machine and the voltage converter may be provided, this circuit being arranged outside the second housing part and using a cooling liquid such as water or glycol water. The oil is for example exclusively contained in the housing part receiving the reduction system, not directly cooling the electric propulsion machine and / or the voltage converter.

[0020] This cooling circuit may comprise an additional dissipation portion, in particular a coil-shaped portion, and / or a radiator carried by the module, to dissipate all or part of the heat recovered by the liquid circulating in the cooling circuit. The radiator is for example attached to the outside of the wall of the module, for example via screws or any other fixing means. The heat dissipation in the first housing part may be done without heat transfer to the oil in the second housing part. No heat exchanger is for example provided between the cooling circuit and the oil.

[0021] As a variant of what has just been described, and whether or not there is an additional dissipation portion of the cooling circuit and / or a radiator, the electric propulsion module may comprise a heat exchanger making it possible to transmit to the oil in the second housing part all or part of the heat recovered by the liquid circulating in the cooling circuit. The oil present in the reduction system can then be used to dissipate all or part of the heat recovered by the liquid circulating in the cooling circuit from the voltage converter and the electric propulsion machine. Furthermore, this heating of the oil by the heat recovered by the cooling circuit can make it possible to improve the efficiency of the reduction system arranged in the second housing part. The heat exchanger can be arranged in the second housing part.The second housing part is, for example, partially filled with oil, and the heat exchanger is then immersed in the oil. A sealed wall is, for example, provided between the first and second housing parts, and this wall is crossed by a supply conductor of the cooling circuit towards the heat exchanger, and by a return conductor of this cooling circuit coming from the heat exchanger.

[0022] Alternatively, the heat exchanger may be arranged in the first part of housing, in which case a channel through which the oil circulates from the second housing part can be provided in the first housing part. In the latter case, a pump can be provided to force the circulation of oil in this channel. This pump can have a dual function, namely to force this circulation of oil, but also to force the circulation of the liquid in the cooling circuit. This dual function can be ensured using a single electric motor.

[0023] When the electric propulsion module comprises such a first and second housing part, all or part of the outer surface of the second housing part may carry cooling reliefs making it possible to dissipate the heat existing in this second housing part to the outside of the module. Equipping the second housing part with cooling reliefs makes it possible to increase the exchange surface of the module with the air, and therefore the dissipation of heat to the outside of the module, thus improving the cooling by the air. The second housing part thus plays, alone or in combination with other parts, the role of a radiator. These reliefs may be different from the stiffening ribs of this second housing part.

[0024] When the electric propulsion module comprises such a first and second housing part, cooling reliefs may also be carried by the outer surface of the first housing part. Here again, these reliefs may be different from stiffening ribs of this first housing part. The entire outer surface of the first housing part carries, for example, cooling reliefs and the entire outer surface of the second housing part carries, for example, other cooling reliefs. Whether carried by the first or by the second housing part, the cooling reliefs may be fins. These fins may be arranged in rows, and a pitch, constant or not, may exist between two adjacent rows. These rows may or may not all have the same orientation.If necessary, the same fins may extend on the one hand over the first housing part and on the other hand over the second housing part. The cooling reliefs may be made in one piece with the housing part carrying them. Alternatively, these cooling reliefs are attached to this housing part.

[0025] As a variant of what has just been described, the outer surface of the second housing part may be devoid of cooling reliefs. In such a case, cooling reliefs may nevertheless be carried by the outer surface of the first housing part. The entire outer surface of the first housing part carries, for example, cooling reliefs. These cooling reliefs may be fins. These fins may be arranged in rows, and a pitch, constant or not, may exist between two adjacent rows. These rows may or not all have the same orientation. These cooling reliefs can be made in one piece with the first part of the housing or be added to this first part of the housing.

[0026] In all of the above, the cooling circuit may be in direct contact only with the stator of the electric propulsion machine, and not with its rotor, or may be in direct contact only with the rotor of the electric propulsion machine, and not with its stator. Alternatively, in all of the above, the cooling circuit may comprise a first branch directly in contact with the stator and a second branch, parallel to the first branch, and directly in contact with the rotor. According to this variant, the cooling circuit thus comes directly into contact with the stator via its first branch and also directly into contact with the rotor via its second branch.

[0027] As a variant of what has just been described, the electric propulsion machine may not be received in the same housing part as the voltage converter. The electric propulsion module comprises, according to this variant, a first housing part receiving the electric propulsion machine and the reduction system and containing oil, and a second housing part receiving the voltage converter, the module further comprising a cooling circuit for the voltage converter. According to this variant, the cooling circuit may not come into contact with the electric propulsion machine, being for example arranged only in the second housing part. Where appropriate, a heat exchanger may or may not be provided, so as to transmit to the liquid circulating in the cooling circuit heat recovered by the oil in contact with the electric propulsion machine.As already mentioned, cooling reliefs such as fins may be provided on the outer surface of the first and / or second housing part.

[0028] In all of the above when the electric propulsion module comprises a first housing part and a second housing part:

[0029] - the first housing part and the second housing part may be rigidly fixed together, for example by means of screws, and / or

[0030] - each aforementioned housing part may be in one piece or be formed by the assembly of sub-parts of housings, and / or

[0031] - the joining of the first housing part and the second housing part can fully define the outer surface of the electric propulsion module.

[0032] In all of the above, the module may comprise only three interfaces with the outside, namely a first interface for supplying electrical energy to the electric propulsion module from an electrical energy storage unit, a second interface for transmitting the engine torque generated by the module, and a third interface for exchanging information to control the module.

[0033] The module can be fixed to the axle by screws.

[0034] In all of the above, the electric propulsion machine may be a synchronous machine or an asynchronous machine. When it is a synchronous machine, it may have a wound rotor or a permanent magnet rotor. The nominal power supplied by the electric propulsion machine may be between 10 and 35 kW, for example of the order of 15 kW or 25 kW for a supply voltage whose nominal value is 48V. In the case of an electric machine adapted to a high voltage supply, the nominal power supplied by this electric machine may be a few hundred kW, for example 400 kW.

[0035] The reduction system may comprise several gears, for example two or more gears. The reduction system may define a single ratio, the value of this single ratio being for example between 2 and 50. Alternatively, the reduction system may be configured to define two or three distinct ratios.

[0036] The voltage converter may be an inverter / rectifier, for example using field effect transistors, such as MOSFET transistors, or IGBTs. The transistors are for example made of gallium nitride (GaN), silicon carbide (SiC) or silicon. In the case of a supply voltage with a nominal value of 48V, MOSFET transistors will be preferred, for example, and in the case of a supply voltage corresponding to high voltage, IGBTs will be preferred, for example.

[0037] The invention also relates, according to another of its aspects, to an electric or hybrid vehicle propulsion system, comprising:

[0038] - the above set

[0039] - a first axle, capable of receiving torque from a thermal engine and / or a machine

[0040] additional electric propulsion, and

[0041] - a second axle on which is mounted, in particular rigidly fixed, the module of propulsion,

[0042] the propulsion system being devoid of a transmission shaft between the first axle and the second axle.

[0043] The invention thus makes it possible to have a four-wheel drive system without coupling the first axle and the second axle via a transmission shaft.

[0044] The first axle is for example the front axle of the vehicle and the second axle is the rear axle of the vehicle. The electric propulsion module can be directly mounted on the second axle.

[0045] The second axle can carry a single electric propulsion module or carry two separate electric propulsion modules, each electric propulsion module then being as described above and dedicated to one of the two wheels associated with this second axle. In this case, these two propulsion modules can be activated simultaneously by the control system when the predefined condition(s) are detected.

[0046] The invention also relates, according to another of its aspects, to a hybrid vehicle powertrain, comprising:

[0047] - the above propulsion system, and

[0048] - a heat engine coupled to the first axle so as to provide a driving torque to this first axle,

[0049] the powertrain being devoid of an additional electric propulsion machine providing engine torque to the first axle.

[0050] The invention also relates, according to another of its aspects, to a hybrid vehicle powertrain, comprising:

[0051] - the above propulsion system,

[0052] - a heat engine coupled to the first axle so as to provide a torque engine at this

[0053] first axle,

[0054] - an additional electric propulsion machine, coupled to the first axle of so as to provide engine torque to this first axle in addition to or as a replacement for the engine torque provided by the thermal engine, and

[0055] - a gearbox,

[0056] the rotor of the additional electric propulsion machine being connected to the crankshaft of the heat engine, or to the input of the gearbox from the point of view of the engine torque transmitted to the first axle, or to the output of the gearbox from the point of view of the engine torque transmitted to the first axle, or at the gearbox. "Connected" here means "solid at least in rotation".

[0057] If necessary, another additional electric propulsion machine can be mounted on the first axle, in addition to that coupled to the first axle and mentioned above.

[0058] The invention also relates, according to another of its aspects, to an electric vehicle powertrain, comprising:

[0059] - the above propulsion system, and

[0060] - an additional electric propulsion module, comprising: a machine electric of

[0061] additional propulsion, an additional voltage converter supplying this machine

[0062] electric, and an additional reducer coupled to the additional electric propulsion machine, this additional propulsion module being mounted on the first axle of the vehicle so that the output of the additional reducer provides driving torque to this first axle.

[0063] This additional propulsion module may be similar, in terms of structure, in particular with a first and a second housing part, to that described previously.

[0064] Each of the above powertrains may comprise an electrical energy storage unit, in particular an electrical energy storage unit having a nominal voltage whose value is 48V or a value greater than 300V.

[0065] For each of the above powertrains, the invention only allows the transition to all-wheel drive with four-wheel drive in targeted cases.

[0066] The invention also relates, according to another of its aspects, to a method for controlling an electric or hybrid vehicle propulsion system, comprising:

[0067] - a first axle, capable of receiving torque from a thermal engine and / or a machine

[0068] additional electric propulsion,

[0069] - a second axle on which is mounted, in particular rigidly fixed, a module of propulsion, this propulsion module comprising: an electric propulsion machine, a voltage converter supplying this electric machine, and a reducer coupled to the electric machine, the output of the reducer being capable of providing a motor torque to this second axle, and

[0070] - a control system configured to automatically activate the module of electric propulsion so that it provides engine torque to the second axle when at least one of the following conditions is detected by this system:

[0071] - detection of a turn in the vehicle's path, and

[0072] - detection of a lack of adhesion of the vehicle to the ground.

[0073] All or part of the above still applies to this method.

[0074] The invention may be better understood by reading the following description of a non-limiting example of its implementation and by examining the attached drawing in which:

[0075] [fig. 1] is a schematic of an axle on a propulsion assembly according to an example of

[0076] implementation of the invention is mounted, and

[0077] [fig.2] represents on the same diagram different powertrains to which applies

[0078] the invention, and

[0079] [fig.3] represents an algorithm for detecting a turn.

[0080] [fig.l] shows an axle 1 and a propulsion assembly 2 according to an example of implementation of the invention.

[0081] The axle 1 is here a rear axle of an electric or hybrid vehicle on which an electric propulsion module 3 is mounted. This electric propulsion module 3 here comprises an electric propulsion machine, a voltage converter supplying the stator of this electric machine from an electrical energy storage unit of the vehicle, and a reducer supplying a motor torque to the rear axle 1.

[0082] The electric propulsion module 3 is for example as described in one of the applications below filed in France by Valeo Embrayages:

[0083] - application for filing number 19 00545 filed on 01 / 22 / 2019,

[0084] - application for filing number 19 05239 filed on 05 / 20 / 2019, or

[0085] - application for filing number 19 05237 filed on 05 / 20 / 2019.

[0086] The electric propulsion machine may be a synchronous machine or a asynchronous machine. The nominal power supplied by the electric propulsion machine can be between 10 and 35 kW, for example in the order of 15 kW or 25 kW for a supply voltage with a nominal value of 48V.

[0087] The reduction system may comprise several gears, for example two or more gears. The reduction system may define a single ratio, the value of this single ratio being for example between 2 and 50. Alternatively, the reduction system may be configured to define two or three distinct ratios.

[0088] The voltage converter may be an inverter / rectifier, for example using field effect transistors, such as MOSFET transistors, or IGBTs.

[0089] The electric propulsion module 3 is for example screwed onto the rear axle 1, the axis of rotation of the electric propulsion machine being here parallel to the axis of rotation of the wheels 5 mounted on this axle 1.

[0090] The assembly also comprises a control system 6 for the electric propulsion module 3, this control system 6 being able to be mounted on the rear axle 1 or integrated into the vehicle and remote from the axle 1. The control system 6 is for example integrated into the vehicle control device (VCU). The control system 6 may comprise a digital processing unit, implementing one or more microcontrollers. If necessary, the control system 6 may communicate directly or indirectly with a remote data server via a telephone communication network, as will be seen later.

[0091] As can be seen in [fig.2], the axle 1 carrying an electric propulsion module 3 of a propulsion assembly 2 according to the invention can be integrated into several types of vehicle powertrains 20, each of these powertrains topropulsions further comprising another axle 8 constituting in this case the front axle of the vehicle. In each of these powertrains 20, no transmission shaft is present between the front axle 8 and the rear axle 1.

[0092] Thus, in an application in a hybrid powertrain, no other electric propulsion machine may be present, in which case only the thermal engine 22 of the vehicle provides engine torque to the front axle 8 via a clutch 24 and a gearbox 25.

[0093] In another application in a hybrid powertrain, an additional electric propulsion machine 30 is provided and its rotor is rotationally fixed to the crankshaft 28 of the heat engine 22, being connected to the latter by a belt.

[0094] In another application in a hybrid powertrain, an additional electric propulsion machine 30 is provided, having its rotor integral in rotation with the crankshaft 28 of the thermal engine, and being arranged upstream of the clutch 24, from the point of view of the engine torque passing towards the front axle 8.

[0095] In another application in a hybrid powertrain, an additional electric propulsion machine 30 is provided, having its rotor integral in rotation with the input of the gearbox 25 from the point of view of the engine torque passing to the front axle 8. This additional electric propulsion machine is here decoupleable from the thermal engine 22 via the clutch 24.

[0096] In another application in a hybrid powertrain, an additional electric propulsion machine 30 is provided, having its rotor rotationally fixed to the output of the gearbox 25 from the point of view of the engine torque passing to the front axle 8.

[0097] In another application in a hybrid powertrain not shown, the additional electric propulsion machine 30 is arranged at the gearbox 25.

[0098] In all the above applications in a hybrid powertrain, one or more additional electric propulsion machines 30 may still be mounted directly on the front axle 8, in addition to the additional rotating electric machine 30 already mentioned.

[0099] In an application in an electric powertrain, an electric propulsion module similar to that described previously is mounted on the front axle 8.

[0100] In all these powertrains, the front axle 8 is the driving axle, receiving engine torque from the thermal engine 22 and / or engine torque from an additional electric propulsion machine 30 or from an electric propulsion module.

[0101] The invention consists in automatically activating the electric propulsion module 3 of the propulsion assembly 2 which is mounted on the rear axle 1, so that the vehicle switches to four-wheel drive operation, when one or more predefined conditions are detected by the control system 6. These predefined conditions include in the example considered: the detection of a bend in the vehicle's path, and the detection of a lack of grip of the vehicle on the ground. Other conditions are possible, for example the detection of a regenerative mode or a "boost" mode.

[0102] To detect the presence of a turn, the control system 6 can use at least one of the following data: value of the steering angle of the vehicle, value of the yaw angle of the vehicle and speed of the vehicle. These different values ​​are for example received and analyzed by the control system 6 according to the algorithm of fig 3. As a variant or in addition to this algorithm, the control system 6 can use geolocation data of the vehicle to perform this turn detection. The control system 6 communicates for example, directly or indirectly, with a remote server via a mobile telephone network, for example 3G, 4G or 5G. Knowing the position of the vehicle and the route of the road that this vehicle is taking, the control system 6 can compare this position and this route and detect the presence of a turn.

[0103] The detection of a grip defect by the control system 6 is carried out for example by comparing the grip coefficient of the vehicle with a threshold value and by considering this grip defect detected when the value of this grip coefficient falls below a threshold value.

[0104] The control system 6 is in the example considered configured to automatically deactivate the electric propulsion module 3 when the condition is no longer detected, if necessary after a time delay. This time delay is for example of the order of a few seconds, either after the detection of the exit from the bend, or after the last detection of a grip coefficient value below the threshold value.

[0105] The invention is not limited to the example which has just been described.

[0106] The invention still applies when instead of a single propulsion module electric 3, two electric propulsion modules 3 are mounted on the rear axle 1. In this case, each of these electric propulsion modules 3 is coupled to a wheel 5 mounted on the axle 1, and these two electric propulsion modules 3 can be activated simultaneously by the control system 6 when the predefined condition(s) mentioned above are detected.

Claims

Claims

1. Propulsion assembly (2) of a hybrid or electric vehicle, comprising: - an electric propulsion module (3), comprising: an electric propulsion machine, a voltage converter supplying this electric machine, and a reducer coupled to the electric machine, this module being able to be mounted on an axle (1) of the vehicle so that the output of the reducer provides a motor torque to this axle, and - a control system (6) configured to automatically activate the electric propulsion module (3) so that it provides a motor torque to the axle when a turn in the path of the vehicle is detected by this system (6), and the control system (6) being configured to automatically activate the electric propulsion module (3) so that it provides a motor torque to the axle when a lack of grip of the vehicle on the ground is detected.

2. Assembly according to claim 1, in which the detection of a turn by the control system (6) is carried out as a function of at least one of the following data: value of the steering angle of the vehicle, value of the yaw angle of the vehicle and speed of the vehicle, geolocation data.

3. Assembly according to claim 1 or 2, in which the detection of a lack of adhesion of the vehicle to the ground by the control system (6) is carried out as a function of the value of the adhesion coefficient of the vehicle.

4. An assembly according to any one of the preceding claims, wherein the control system (6) is configured to automatically deactivate the electric propulsion module (3) when the condition is no longer detected, possibly after a time delay.

5. Electric or hybrid vehicle propulsion system, comprising: - the assembly (2) according to any one of the preceding claims, - a first axle (8), capable of receiving torque from a heat engine (22) and / or an additional electric propulsion machine (30), and - a second axle (1) on which the electric propulsion module (3) is mounted, the propulsion system being devoid of a transmission shaft between the first axle (8) and the second axle (1).

6. Propulsion system according to claim 5, the second axle (1) carrying a single electric propulsion module (3) or two electric propulsion modules, each electric propulsion module then being dedicated to one of the two wheels (5) associated with this second axle (1).

7. Hybrid vehicle powertrain (20), comprising: - the propulsion system according to claim 5 or 6, and - a heat engine (22) coupled to the first axle (8) so as to provide engine torque to this first axle (8), the powertrain (20) being devoid of an additional electric propulsion machine (30) providing engine torque to the first axle (8).

8. A hybrid vehicle powertrain (20), comprising: - the propulsion system according to claim 5 or 6, - a heat engine (22) coupled to the first axle (8) so as to provide engine torque to this first axle (8), - an additional electric propulsion machine (30), coupled to the first axle (8) so as to provide engine torque to this first axle (8) in addition to or in replacement of the engine torque provided by the heat engine (22), and - a gearbox (25), the rotor of the additional electric propulsion machine (30) being connected to the crankshaft (28) of the heat engine (22), or to the input of the gearbox (25) from the point of view of the engine torque passing to the first axle (8), or to the output of the gearbox (25) from the point of view of the engine torque transmitted to the first axle (8), or at the level of the gearbox (25).

9. An electric vehicle powertrain (20), comprising: - the propulsion system according to claim 5 or 6, and - an additional electric propulsion module, comprising: an electric machine of additional propulsion, an additional voltage converter powering this machine electric, and an additional reducer coupled to the electric propulsion machine additional, this additional propulsion module being mounted on the first axle (8) of the vehicle so that the output of the additional reducer provides engine torque to this first axle (8).

10. Method for controlling an electric or hybrid vehicle propulsion system, comprising: - a first axle (8), capable of receiving torque from a thermal engine (22) and / or a machine additional electric propulsion (30), - a second axle (1) on which an electric propulsion module (3) is mounted, this electric propulsion module (3) comprising: an electric propulsion machine, a voltage converter supplying this electrical machine, and a reducer coupled to the electric machine, the output of the reducer being capable of providing a motor torque to this second axle (1), and - a control system (6) configured to automatically activate the propulsion module electric (3) so that it provides a motor torque to the second axle (1) when at least one of the following conditions is detected by this system (6): - detection of a turn in the vehicle's path, and - detection of a lack of vehicle grip on the ground.

Images