CONTROL OF THE SPEED OF AN ELECTRIC MOTOR COUPLED TO A PRIMARY SHAFT OF A VEHICLE'S GEARBOX

Abstract

A control method is implemented in a vehicle comprising a thermal engine capable of rotating the input shaft of a multi-speed gearbox, and an electric machine coupled to the input shaft that can generate electrical power when driven by the latter at a given rotational speed. This method includes a step (10⁻⁴⁰) in which the future internal temperature of the electric machine is determined at time t for a chosen duration starting at that time t, given the current rotational speed and internal temperature of the electric machine. Then, the electrical power that can be generated by the electric machine at this future internal temperature is determined. If this determined electrical power is below a chosen threshold, the current gear ratio is changed to a higher one. Figure 3

Description

Title of the invention: CONTROL OF THE SPEED OF AN ELECTRIC MACHINE COUPLED TO A PRIMARY SHAFT OF A VEHICLE'S GEARBOX Technical field of the invention

[0001] The invention relates to vehicles comprising a thermal engine and an electric machine coupled to the input shaft of an automated gearbox, and more specifically to the control of the rotational speed of such an electric machine. Prior art

[0002] Certain vehicles, possibly of the automobile type, comprise, on the one hand, a powertrain (or PMT) comprising at least one thermal engine capable of supplying motive power (or engine torque) to the primary shaft of an automated gearbox, and, on the other hand, an electric machine coupled to this primary shaft and capable of generating electrical power when driven by the latter according to a rotational regime.

[0003] It should be noted that this electric machine may optionally be part of the powertrain, and in this case it is also capable of driving the primary shaft of the gearbox when it is supplied with electrical energy by a power (or "traction" or main) battery of the vehicle. The powertrain is then said to be "hybrid".

[0004] When the vehicle is in a purely thermal driving phase, the electrical power generated by the electric machine is generally used to power an electrical power supply network (called "on-board network") equipping the vehicle and to which electrical equipment consuming electrical energy at a very low predefined voltage (typically 12 V or 24 V) is coupled.

[0005] As those skilled in the art know, the electrical power generated by an electric machine depends on its rotational speed but also on the remanent magnetic field of the magnets in its rotor. The intensity of this remanent magnetic field decreases as the internal temperature of the magnets increases, for example, due to the rising temperature of the oil in the gearbox located in the immediate vicinity of, or incorporated into, the electric machine. For example, the intensity of the remanent magnetic field of a NeFeBo type magnet can be reduced by 80% at 130°C.

[0006] Consequently, the continuous electrical power generation capacity of an electrical machine varies with its internal temperature, generally in a substantially inverse parabolic manner. As a result, it frequently happens that the electrical power generated by the electrical machine is insufficient to supply the vehicle's on-board network, which requires using the vehicle's auxiliary battery instead (when it exists).

[0007] To prevent the electrical power generated by the electric machine from becoming insufficient to supply the onboard network, it is possible to significantly increase the intensity of the remanent magnetic field of the rotor magnets. This can be achieved, for example, by doping each magnet with a mass of dysprosium (Dy) equal to approximately 10% of its total mass. However, such a solution considerably increases the cost of the magnets due to the very high cost of dysprosium (a rare earth element).

[0008] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0009] In particular, it proposes for this purpose a control method intended to be implemented in a vehicle comprising a thermal engine suitable for driving in rotation a primary shaft of a gearbox having several ratios, and an electric machine coupled to this primary shaft and suitable for generating electrical power when driven by the latter according to a rotation regime.

[0010] This control method is characterized by the fact that it includes a step in which:

[0011] - we determine at a time t what a future internal temperature of the machine will be electrical power for a chosen duration starting at this instant t in the presence of the current rotational speed and a current internal temperature of the electrical machine, then electrical power that can be generated by the latter in the presence of this future determined internal temperature, and

[0012] - if this determined electrical power is less than a chosen threshold, it is required a change from a current ratio to a higher ratio.

[0013] Thanks to the invention, the introduction of a ratio n+1, higher than that n in progress, induces a notable decrease in the current rotation rate of the primary shaft and therefore also of the electric machine, which makes it possible to limit significantly the increase in the internal temperature in progress and therefore to limit significantly the loss of electrical power generation capacity of the electric machine without it being necessary to dope each magnet of the rotor of this electric machine.

[0014] The control method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0015] - in its step, the chosen duration can be between five seconds and fifteen seconds;

[0016] - in the presence of the first option, in its step, the chosen duration may be equal to ten seconds;

[0017] - in its step, the future internal temperature can be determined in a first table which establishes a correspondence between pairs of rotation regime and current internal temperature and future internal temperatures;

[0018] - in its step, the electrical power that can be generated can be determined in a second table which establishes a correspondence between internal temperatures and electrical powers;

[0019] - in its stage, in the presence of an electrical power supply network equipping the vehicle and to which are coupled electrical equipment of the latter consuming electrical energy at a predefined very low voltage, the chosen threshold can be an electrical power capable of providing a chosen voltage greater than or equal to this predefined very low voltage;

[0020] - in the presence of the last option, in its step, the chosen voltage can be between 100% of the predefined extra low voltage and 120% of the predefined extra low voltage.

[0021] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing the control method of the type presented above in a vehicle comprising a thermal engine suitable for rotating a primary shaft of a gearbox having several ratios, and an electric machine coupled to this primary shaft and suitable for generating electrical power when driven by the latter according to a rotational regime, to control the rotational regime of the electric machine.

[0022] The invention also proposes a control device intended to equip a vehicle comprising a thermal engine suitable for driving in rotation a primary shaft of a gearbox having several ratios, and an electric machine coupled to this primary shaft and suitable for generating electrical power when driven by the latter according to a rotation regime.

[0023] This control device is characterized in that it comprises at least one processor and a memory arranged to perform the operations consisting of:

[0024] - to determine at a given time t what the future internal temperature of the machine will be electrical power for a chosen duration starting at said instant t in the presence of the current rotational speed and a current internal temperature of the electrical machine, then electrical power that can be generated by the latter in the presence of this future determined internal temperature, and

[0025] - if this determined electrical power is less than a chosen threshold, to require a changing a current ratio to a higher ratio.

[0026] The invention also provides for a vehicle, possibly of the automobile type, comprising, on the one hand, a thermal engine suitable for driving in rotation a primary shaft of a gearbox having several ratios, and an electric machine coupled to this primary shaft and capable of generating electrical power when driven by the latter according to a rotational regime, and, on the other hand, a control device of the type of that presented above.

[0027] For example, the electric machine can also be suitable for driving the primary shaft of the gearbox in rotation when it is supplied with electrical energy by a vehicle power battery. Brief description of the figures

[0028] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0029] [Fig. 1] schematically and functionally illustrates an example of an embodiment of a vehicle comprising a control device according to the invention, and a hybrid powertrain supervised by a supervisory computer,

[0030] [Fig.2] schematically and functionally illustrates an example of an embodiment of a supervisory computer comprising a control device according to the invention, and

[0031] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention. Detailed description of the invention

[0032] The invention aims in particular to propose a control method, and an associated DC3 control device, intended to allow control of the rotational speed rr(t) of an electric machine ME coupled to the primary shaft AP of an automated gearbox BV and to which can also be coupled a thermal drive machine MMT of a powertrain (or GMP) of a vehicle V.

[0033] In what follows, vehicle V is considered, by way of non-limiting example, to be of the automobile type. For example, it is a car, as illustrated in [Fig. 1]. However, the invention is not limited to this type of vehicle. It relates in fact to any type of vehicle (land, sea (or river), or air) comprising a thermal engine and an electric machine coupled to the input shaft of an automated gearbox.

[0034] A vehicle V comprising a hybrid GMP transmission chain (and therefore comprising at least one electric motor ME and at least one thermal motor MMT associated with an automated gearbox BV, a CS supervisory computer, a BS auxiliary battery, a BP (rechargeable) power (or main or traction) battery, a CV converter, and a DC3 control device according to the invention) has been schematically represented on [Fig.1], by way of illustrative example.

[0035] It should be noted that the invention also relates to vehicles comprising, on the one hand, a purely thermal powertrain, that is to say comprising at least one thermal engine suitable for being coupled to the primary shaft of an automated gearbox to supply it with engine torque, and, on the other hand, an electric machine coupled to this primary shaft and which can only generate electrical power when driven by the latter according to a rotation regime.

[0036] Furthermore, the transmission chain could also allow a four-wheel drive (or 4x4) or 4x2 mode.

[0037] The auxiliary battery BS is responsible for supplying electrical power to an electrical power supply network (referred to as the vehicle's on-board network) RB, supplementing that supplied by the converter CV, which is powered by the main battery BP via a main electrical circuit, and sometimes replacing this converter CV. For example, this auxiliary battery BS may be configured as a very low voltage (VLV) battery (typically 12 V or 24 V). It is (here) rechargeable at least by the converter CV, which uses electrical energy stored in the main battery BP for this purpose. In the following, for the sake of non-limiting example, the auxiliary battery BS is considered to be a 12 V lead-acid battery.

[0038] The RB on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) are coupled which consume electrical energy having a predefined very low voltage tbt.

[0039] The main electrical circuit (or "high voltage" or "power" circuit) is connected, on the one hand, to the power battery BP via an interface device, and, on the other hand, to electronic equipment, such as the CV converter and the ME electric machine. It may also optionally allow the power battery BP to be recharged by an external power source temporarily connected to the vehicle V.

[0040] As illustrated in [Fig.1], the transmission chain also includes, here, a drive shaft AM, a first coupling device DC1, a second coupling device DC2, and a transmission shaft AT.

[0041] The operation of the transmission chain (and therefore of the powertrain) is supervised by a CS supervisory computer.

[0042] The MMT thermal drive machine comprises a crankshaft (not shown) which is fixedly attached to the drive shaft AM in order to drive the latter (AM) in rotation or to be driven in rotation by this drive shaft AM. This MMT thermal drive machine is designed to provide, here for the drive wheels of the vehicle V, a thermal engine torque which is defined by a thermal torque setpoint, for example determined by the CS supervisory computer.

[0043] The operation of the MMT thermal engine is controlled by a CMT thermal engine computer and supervised by the CS supervisory computer. It should be noted that the CMT thermal engine computer and the CS supervisory computer could be part of the same "supercomputer".

[0044] Furthermore, the MMT internal combustion engine is designed to be coupled to the primary shaft AP of the gearbox BV, via at least the first coupling device DC1, to drive it in rotation (and thus supply it with internal combustion engine torque). This latter device (DC1) is designed to deliver torque derived from the internal combustion engine torque, in particular (here) for at least one set Tl of drive wheels, when it is at least partially closed (or open) and therefore when it couples the MMT internal combustion engine to the gearbox BV (and more precisely to a clutch of the latter (BV)).

[0045] For example, the first coupling device DC1 could be a hydraulic circuit clutch. But it could be of another type.

[0046] Also, for example, the Tl axle can be located in the front PVV section of the vehicle V. Preferably, and as illustrated, it is coupled to the AT driveshaft via a differential (here, the front one) DV. However, in a variant, this Tl axle could be the one referenced as T2, which is located in the rear PRV section of the vehicle V. The engine torque, which is produced by the powertrain to drive the drive wheels (here, of the front axle Tl), is therefore supplied to these wheels at the output of the differential DV.

[0047] It should be noted that in the example illustrated, but not limited to, in [Fig. 1], the crankshaft of the MMT internal combustion engine is also coupled to a belt, which is itself coupled to a starter-alternator AD that is electrically powered by the auxiliary battery BS (and which can also (here) recharge the latter (BS)). Thus, the starter-alternator AD can supply torque to the belt, which can then supply this torque to the crankshaft to start the MMT internal combustion engine. The MMT internal combustion engine can also, in this case, be started by the electric motor ME when the first coupling device DC1 is at least partially closed and the electric motor ME supplies torque to the input shaft (as in the case of the hybrid powertrain). It should be noted that in a variant, the starter-alternator AD could be powered by the power battery BP.

[0048] The electric machine ME is coupled to the primary shaft AP of the gearbox BV so that it is capable of generating electrical power pe when driven by this primary shaft AP at a rotational speed rr(t). The rotational speed rr(t) at any given time t can be measured, for example periodically, by a dedicated sensor (not shown) coupled to the primary shaft AP.

[0049] For example, this coupling between the electric machine ME and the primary shaft AP can be done downstream of the first coupling device DC1, by means of the second coupling device DC2.

[0050] This second coupling device DC2 can, for example, include a cascade of gears connecting the electric machine ME to the input of the gearbox BV (downstream of the first coupling device DC1).

[0051] It should be noted that, given that in the illustrated and described example the powertrain is hybrid, the electric machine ME is also capable, when supplied with electrical energy by the power battery BP, of operating at a rotational speed rr(t) to provide the primary shaft AP with an electric motor torque defined by an electrical torque setpoint (for example, determined by the supervisory computer CS), here for the drive wheels of vehicle V. The electric machine ME therefore provides, here, the electric motor torque it produces for the train T1 and / or for the internal combustion engine MMT. However, in one variant, this first train T1 could be the second train T2, which is located in the rear section PRV of vehicle V, and in another four-wheel-drive variant, the electric motor torque could be transmitted to both the first T1 and second T2 trains.

[0052] It should also be noted that the electric machine ME can also be arranged here to recover a torque defined by a setpoint from the vehicle V, for example during a regenerative braking phase, and in this case, this recovered torque can be used to recharge the power battery BP associated with the electric machine ME. But the recovery can also be made from a portion of the internal combustion engine torque supplied by the internal combustion engine MMT.

[0053] The operation of the electric machine ME is controlled by an electric machine computer CME, and supervised by the supervisory computer CS.

[0054] As illustrated in [Fig. 1], the electric machine ME is equipped with a temperature sensor CT arranged to measure its current internal temperature at time t ti(t), for example periodically. It is thus possible to determine the current internal temperature ti(t) of the rotor magnets of the electric machine ME.

[0055] It should be noted that in the example illustrated, but not limited to, in [Fig. 1], the differential DV is not part of the gearbox BV. However, in an alternative embodiment, it could be part of this gearbox BV.

[0056] For example, the power (or main or traction) battery BP can be of the cellular type. In this case, it comprises electrical energy storage cells, possibly electrochemical (such as lithium-ion (or Li-ion) or Ni-MH or Ni-Cd cells). Also, for example, this power battery BP can be of the 48 V type. But this is not mandatory. Indeed, it could alternatively be of the 450 V, 600 V, or even 800 V type, for example.

[0057] As mentioned above, the gearbox is automated. For example, it may be a dual-clutch (or DCT) gearbox. However, it could have only one clutch associated with a single input shaft. This gearbox has several (at least two) gear ratios, referenced n, with n = 1 to N (ratio 1 being the lowest and ratio N being the highest). For example, N could be between 5 and 9.

[0058] The operation of the BV gearbox is controlled by a CB gearbox computer, and supervised by the CS supervision computer.

[0059] As illustrated, but not limited to, in [Fig. 1], the vehicle V also includes an accelerator pedal PA which can be operated (here) by a foot of the driver of the vehicle V, and which has a percentage of depressment from which an overall torque command is defined, which then represents the driver's intention regarding the acceleration of the vehicle V. This overall torque command can, for example, be determined by the supervisory computer CS, and the powertrain must supply the drive wheels (here of the front axle T1) with an engine torque which must correspond (within a certain tolerance) to this overall torque command.

[0060] As mentioned above, the invention proposes in particular a control method intended to allow control of the rotational speed rr(t) of the electric machine ME of the vehicle V.

[0061] This control method can be implemented at least partially by the DC3 control device (illustrated at least partially in Figures 1 and 2), which for this purpose comprises at least one PR1 processor, for example of the microprocessor type, and at least one first MD1 memory. This DC3 control device can therefore be implemented in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). By way of example, it could be a microcontroller.

[0062] The MD1 memory is random access memory (RAM) to store instructions for the implementation by the PR1 processor of at least part of the control process. The PR1 processor may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is defined as any type of device capable of performing at least one electrical or electronic operation.

[0063] In the example illustrated, but not limited to, Figures 1 and 2, the DC3 control device is part of the CS supervisory computer. However, this is not mandatory. Indeed, the DC3 control device could comprise its own dedicated computer, which could then be coupled to the CS supervisory computer, or it could be part of another computer embedded in the vehicle V and ensuring at least one other function, such as for example the CME electrical machine calculator.

[0064] As illustrated non-limitingly in [Fig.3], the (control) method according to the invention includes a step 10-40 which is implemented each time the thermal engine MMT supplies thermal engine torque to the primary shaft AP by means of placing the first coupling device DC1 in a state at least partially closed and the electric machine ME generates electrical power pe, for example to supply the on-board network RB and / or recharge the power battery BP.

[0065] Step 10-40 of the process includes a substep 10 in which one (for example, the control device DC3) begins by determining, at time t, the future internal temperature fti(t+dc) of the electric machine ME for a chosen duration starting at that time t, in the presence of the current rotational speed rr(t) and the current internal temperature ti(t) of the electric machine ME. It should be noted that the current internal temperature ti(t) is measured by the temperature sensor CT and the current rotational speed rr(t) is measured by a dedicated sensor.

[0066] Step 10-40 of the process also includes a substep 20 in which the electrical power pepg that can be generated by the electric machine ME in the presence of the future internal temperature fti(t+dc) is determined (for example the control device DC3).

[0067] Step 10-40 of the process also includes a substep 40 in which, when the determined electrical power pepg is less than a chosen threshold sc, and therefore on (for example, the control device DC3), a change in the current ratio n in the gearbox BV is requested to a ratio (n+1) greater than the latter (n). This is because there is considered to be a risk of a problem with the generation of electrical power by the electric machine ME. This request can be sent to the supervisory computer CS or to the gearbox computer CB.

[0068] It will be understood that by establishing a ratio n+1 higher than the current ratio n, this induces a significant decrease in the current rotational speed rr(t) of the primary shaft AP and therefore also of the electric machine ME. This makes it possible to significantly limit the increase in the internal temperature ti(t) and thus to significantly limit the loss of electrical power generation capacity of the electric machine ME. Consequently, the probability that the electrical power generated by the electric machine ME will be insufficient to supply the on-board network RB is very low, or even zero. The invention is therefore particularly advantageous because it avoids having to dope each magnet of the rotor of the electric machine ME with a mass of dysprosium, which is particularly economical.

[0069] For example, and as illustrated non-limitingly in [Fig. 3], step 10-40 of the process may also include a substep 30 in which the electrical power pepg, determined in substep 20, can be compared (for example, by the control device DC3) to the chosen threshold sc. If the determined electrical power pepg is less than the chosen threshold sc (i.e., pepg < sc), there is a risk of insufficient electrical power generation by the electric machine ME, and substep 40 is carried out. Conversely, if the determined electrical power pepg is greater than or equal to the chosen threshold sc (i.e., pepg > sc), there is no risk of insufficient electrical power generation by the electric machine ME, and substep 10 is carried out again with the following rotational speed rr(t+l) and the following internal temperature ti(t+l) of the electric machine ME.

[0070] Also, for example, in substep 10 of step 10-40, one (for example, the DC3 control device) can use a chosen duration of which is between five seconds and fifteen seconds.

[0071] By way of illustration, this chosen duration of can be equal to ten seconds. But other values ​​for the chosen duration of can be used. For example, this duration of can be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0072] Also, for example, in substep 10 of step 10-40, one (for example, the control device DC3) can determine the future internal temperature fti(t + dc) in a first lookup table that establishes a correspondence between pairs of current rotational speed and internal temperature and future internal temperatures. It will be understood that it suffices to determine in this first lookup table the future internal temperature fti(t + dc) which is stored corresponding to the pair comprising the current rotational speed rr(t) and the current internal temperature ti(t).

[0073] But in a variant one (for example the DC3 control device) could determine the future internal temperature fti(t+dc) by means of at least one mathematical formula having as parameters the current rotation regime rr(t) and the current internal temperature ti(t).

[0074] Also, for example, in substep 10 of step 10-40, one (for example, the DC3 control device) can determine the electrical power that can be generated pepg in a second lookup table that establishes a correspondence between internal temperatures and electrical powers. It will be understood that it suffices to determine in this second lookup table the electrical power that can be generated pepg, which is stored corresponding to the future internal temperature fti(t+dc).

[0075] But in a variant one (for example the DC3 control device) could determine the electrical power that can be generated pepg by means of at least one mathematical formula having as a parameter the future internal temperature fti(t+dc).

[0076] Also, for example, when the on-board network RB (to which electrical equipment consuming electrical energy at the predefined extra-low voltage tbt is coupled), in substep 30 of step 10-40, one (for example, the control device DC3) can use a chosen threshold sc which is an electrical power capable of supplying a chosen voltage te which is greater than or equal to this predefined extra-low voltage tbt. Thus, it can be guaranteed that the electrical power generated by the electric machine ME will be sufficient to supply at least the on-board network RB.

[0077] Also, for example, in substep 30 of step 10-40, the selected voltage te, which is used to set the selected threshold sc, can be between 100% of the predefined extra-low voltage tbt and 120% of the predefined extra-low voltage tbt. It will be understood that the higher the selected voltage te is compared to the predefined extra-low voltage tbt, the more assured it is that the electrical power generated by the electric machine ME will be sufficient to supply at least the onboard network RB.

[0078] By way of illustration, the chosen voltage te may be equal to 105% of the predefined extra-low voltage tbt. However, other values ​​of the chosen voltage te may be used. For example, this voltage te may be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0079] It should also be noted, as illustrated but not limited to [Fig. 2], that the CS supervisory computer (or the dedicated computer of the DC3 control device) may also include a mass memory (MM), in particular for storing each current rotational speed rr(t) and each current internal temperature ti(t), as well as any intermediate data involved in all its calculations and processing. Furthermore, this CS supervisory computer (or the dedicated computer of the DC3 control device) may also include an input interface (IE) for receiving at least each current rotational speed rr(t) and each current internal temperature ti(t), for use in calculations or processing, possibly after having been shaped and / or demodulated and / or amplified, in a manner known per se, by means of a PR2 digital signal processor.Furthermore, this CS supervisory computer (or the dedicated computer of the DC3 control device) can also include an IS output interface, notably to deliver each gear change message (or command) (n —> n+1).

[0080] It should also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means such as electronic circuits (or hardware), such as the PR1 processor, is suitable for implementing the control method described above to control the rotation speed rr(t) of the electric machine ME of vehicle V.

Claims

Demands

1. A control method for a vehicle (V) comprising a thermal engine (MHE) adapted to drive in rotation a primary shaft (P) of a gearbox (GV) having several ratios, and an electric machine (EM) coupled to said primary shaft (PHE) and adapted to generate electrical power when driven by the latter (PHE) according to a rotation regime, characterized in that it comprises a step (10-40) in which a future internal temperature of said electric machine (EM) is determined at a time t for a chosen duration starting at said time t in the presence of the current rotation regime and a current internal temperature of said electric machine (EM), and then an electrical power that can be generated by the latter (EM) in the presence of this determined future internal temperature,and if this determined electrical power is less than a chosen threshold, a change from the current ratio to a ratio greater than that threshold is required.

2. Method according to claim 1, characterized in that in said step (10-40) said chosen duration is between five seconds and fifteen seconds.

3. Method according to claim 1 or 2, characterized in that in said step (10-40) said future internal temperature is determined in a first table establishing a correspondence between pairs of rotation regime and current internal temperature and future internal temperatures.

4. A method according to any one of claims 1 to 3, characterized in that in said step (10-40) said electrical power that can be generated is determined in a second table establishing a correspondence between internal temperatures and electrical powers.

5. A method according to any one of claims 1 to 4, characterized in that in said step (10-40), in the presence of an electrical supply network (RB) equipping said vehicle (V) and to which are coupled electrical equipment of the latter (V) consuming electrical energy at a predefined very low voltage, said chosen threshold is an electrical power capable of supplying a chosen voltage greater than or equal to said predefined very low voltage.

6. Method according to claim 5, characterized in that in said step (10-40) said selected voltage is between 100% of said predefined very low voltage and 120% of said predefined very low voltage.

7. Product computer program comprising a set of instructions which, when executed by processing means, is suitable for implementing the control method according to any one of claims 1 to 6, in a vehicle (V) comprising a thermal engine (MHE) suitable for rotating a primary shaft (P) of a gearbox (GV) having several ratios, and an electric machine (EM) coupled to said primary shaft (P) and suitable for generating electrical power when driven by the latter (P) according to a rotational regime, for controlling said rotational regime of the electric machine (EM).

8. Control device (DC3) suitable for equipping a vehicle (V) comprising a thermal engine (MHE) suitable for rotating a primary shaft (P) of a gearbox (GV) having several ratios, and an electric machine (EM) coupled to said primary shaft (PHE) and suitable for generating electrical power when driven by the latter (PHE) according to a rotational regime, characterized in that it comprises at least one processor (P1) and at least one memory (MD) arranged to perform the operations of determining at a time t what will be a future internal temperature of said electric machine (EM) for a chosen duration starting at said time t in the presence of the current rotational regime and a current internal temperature of said electric machine (EM), then an electrical power that can be generated by the latter (EM) in the presence of this determined future internal temperature,and if this determined electrical power is less than a chosen threshold, requiring a change from the current ratio to a ratio higher than that threshold.

9. Vehicle (V) comprising a thermal motive machine (MMT) adapted to drive in rotation a primary shaft (AP) of a gearbox (BV) having several ratios, and an electric machine (ME) coupled to said primary shaft (AP) and adapted to generate electrical power when driven by the latter (AP) according to a rotation regime, characterized in that it further comprises a control device (DC3) according to claim 8. 15

10. Vehicle according to claim 9, characterized in that said electric machine (ME) is suitable for driving said primary shaft (AP) of the gearbox (BV) in rotation when it is supplied with electrical energy by a power battery (BP) of said vehicle (V).

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