WO2021038151A1

WO2021038151A1 - Method for protecting a clutch of a hybrid vehicle against overheating

Info

Publication number: WO2021038151A1
Application number: PCT/FR2020/051383
Authority: WO
Inventors: Yohan MILHAU; Ridouane Habbani; Gaetan Rocq; Franck SIRAUDEAU
Original assignee: Psa Automobiles Sa
Priority date: 2019-08-30
Filing date: 2020-07-28
Publication date: 2021-03-04
Also published as: FR3100198A1; FR3100198B1; EP4021750A1; CN114286771A

Abstract

The method protects a clutch (4) of a hybrid vehicle comprising a combustion engine (2), at least one other drive source (10, 18) respectively supplying a combustion engine torque and a drive or assistance torque, a virtual limitation of the combustion engine being fixed above which an analysis and control means imposes on the other drive source (10, 18) an operation at least partially in motor mode. The virtual limitation takes into account at least one actual temperature of the clutch and a speed difference between crankshaft and drive shaft, a maximum temperature of the clutch (4) being predetermined, the at least partial switching of said at least one other drive source (10, 18) into motor mode occurring at least when a detected temperature of the clutch is higher than the maximum temperature, the torque of the combustion engine then being decreased.

Description

DESCRIPTION

TITLE: PROCESS FOR PROTECTING A CLUTCH OF A HYBRID VEHICLE AGAINST OVERHEATING

The present invention claims the priority of French application 1909565 filed on 08.30.2019, the content of which (text, drawings and claims) is incorporated here by reference.

Technical field of the invention

The present invention relates to a method for protecting a clutch of a hybrid vehicle comprising a heat engine, at least one other drive source comprising an energy store, the clutch connecting at least the heat engine to at least one shaft of the engine. drive the wheels of the vehicle, the clutch being protected against overheating.

Prior art

It is known from the state of the art a hybrid vehicle comprising a heat engine, at least one other driving source comprising an energy store, a clutch connecting at least the heat engine to at least one drive shaft of the wheels of the vehicle.

In this configuration, the other motor source (s) have two actuation modes: a motor mode in which they supply energy so as to deliver a traction or assistance torque to the heat engine and a generator mode in which they store energy supplied by the heat engine via the energy store.

The heat engine and the other drive source (s) respectively provide heat engine torque and traction or assistance torque intended to meet an instantaneous drive power demand from the driver of the vehicle.

A means of analysis and control capable of controlling the heat engine and the other motor source (s) is also provided. A virtual limitation of the heat engine is set by the analysis means. Above the virtual limitation, the analysis and control means require the other motor source (s) to operate at least partially in motor mode.

The driver's instantaneous motive power demand is then given priority so that if traction or assistance torque is required or Desirable in response to this desire, the analysis and control means at least partially switch the other driving source (s) to motor mode the time it takes to meet the demand for instantaneous driving power.

The driving source (s) capable of functioning as generators may be placed between the clutch and the wheels of the hybrid vehicle or directly on the wheels. In some life situations it is necessary to use the clutch. This clutch heats up when it is sliding, the energy dissipated in the sliding clutch being equal to the integral of the power dissipated between the crankshaft and the drive shaft of the wheels, this dissipated power being able to be calculated by the product of the speed difference upstream and downstream of the clutch and of the torque transmitted by said clutch.

On a steep slope or high mass of the vehicle, for example by pulling a caravan, or high torque demand from the driver of the vehicle, the clutch heating is very important especially as its cooling system is small.

Consequently, the problem at the basis of the invention is, for a hybrid vehicle comprising at least one motive source other than thermal and a thermal engine connected to at least one drive shaft by a clutch, to prevent the Clutch does heat up in certain driving life situations of the vehicle.

Summary of the invention

To this end, the present invention relates to a method for protecting a clutch of a hybrid vehicle comprising a heat engine, at least one other drive source comprising an energy store, the clutch connecting at least the heat engine to at least one heat engine. at least one drive shaft of the wheels of the vehicle, said at least one other driving source having two actuation modes, an engine mode in which it supplies energy so as to deliver a traction or assistance torque to the engine heat source and a generator mode in which it stores energy supplied by the heat engine via the energy store, the heat engine and said at least one other driving source providing respectively a heat engine torque and a traction torque or assistance intended to respond to a demand for instantaneous motive power on the part of the driver, an analysis and control means being able to control the heat engine and said at least one other motive source, a virtual limitation of the heat engine being set by the analysis means above which limitation the analysis and control means requires said at least one other motive source to operate at least partially in engine mode, the instantaneous motive power demand on the part of the driver then being a priority so that if a traction or assistance torque is necessary or desirable in response to this desire, the analysis and control means at least partially switch said at least one other driving source in engine mode the time to respond to the instantaneous driving power demand, remarkable in that the virtual limitation takes into account at least one effective temperature of the clutch as well as a speed difference between a crankshaft associated with the heat engine and said at least one drive shaft, a maximum temperature of the clutch being predetermined, the at least partial switching of said at least one other driving source in engine mode taking place at least when a temperature is detected of the clutch is greater than the maximum temperature and in the presence of a speed difference between the upstream and downstream side of the clutch, the torque transmitted by the clutch and consequently the torque supplied by the heat engine being then diminished.

The principle underlying the present invention is to reduce the torque transmitted by the clutch by applying at least one motor source other than the heat engine. It is then possible to control the power dissipated because the torque from the other driving source is calculated so that the power to be transmitted to the clutch does not exceed a value equivalent to the heat dissipation value of the clutch. At least when a detected clutch temperature is above the maximum temperature means that the changeover is mandatory above the maximum temperature. On the other hand, in an optional embodiment, a partial tilting can take place below this predetermined maximum temperature, as will be notified later.

As a general idea, the maximum temperature can be 180 ° C or above 180 ° C depending in particular on the model of the clutch. The dissipable power is then to be kept below a certain value, for example, below 10 kWatt, which is achieved by at least partial switching of said at least one other motor source to motor mode.

The limitation of the heat engine for the distribution of torque is deceived in the management of the distribution between the engine and one or more driving sources when the temperature of the clutch exceeds a predetermined maximum temperature.

The torque setpoint is performed by the heat engine up to the virtual limitation of the heat engine. Above this virtual limitation, the other motor source (s) are used either in addition to the heat engine working at reduced power or either with a heat engine stopped.

According to the invention, the virtual limitation of the engine is a function of a criterion depending on the temperature of the clutch in order to protect it. This virtual limitation for the protection of the clutch depends on the temperature of the clutch, on the speed difference between the drive shaft and the crankshaft of the heat engine. The lower the delta speed, the greater the torque that can be transmitted before use of the motor source (s), since the dissipated energy will not be greater. With this mechanism, a certain maximum power of dissipation is authorized in the clutch. When the temperature of the clutch is close to its maximum temperature, the maximum permitted power will be close to the heat dissipation power of the clutch.

The torque transmitted by the clutch can be reduced to zero in extreme weather conditions and the time that a delta clutch speed is completely canceled.

In the context of the invention, it is therefore possible to keep the heat engine in operation but with reduced power.

Advantageously, there is a gradual implementation of the at least partial switching of said at least one other motor source in motor mode from a predetermined minimum temperature 50% lower than the maximum temperature.

Taking the nonlimiting example of a maximum temperature of the order of 180 ° C, as previously mentioned at this maximum temperature of 180 ° C, a dissipable power may have to be maintained below 10 kWatt to avoid heating of the l. 'clutch.

On the other hand, in this configuration, the dissipable power at 150 ° C can go up to 40 to 50kWatt before a gradual changeover. Below 100 ° C, the dissipable power may not be regulated by a changeover.

From the maximum dissipable power values for a temperature between 100 and 180 ° C., or even more, a torque is determined as a function of the speed so as not to exceed a predetermined maximum dissipable power for a given temperature.

This makes it possible to anticipate excessive heating of the clutch and to prevent the maximum temperature from being reached or reached too quickly.

Advantageously, prior to at least partial switching of said at least one other motor source to motor mode, the analysis and control means first of all require the heat engine not to supply the energy store when the detected temperature of clutch is above the minimum clutch temperature.

This temporary measure makes it possible to reduce overheating of the clutch by not requiring the heat engine to supply the energy store electrically. If this is not sufficient, the other motor source or sources are started and compensate for a decrease in the production of torque from the heat engine, or even its stopping. Advantageously, the virtual limitation also takes into account two load thresholds of the energy store predefined in the analysis and control means, one being defined as a priority load threshold and the other being defined as a threshold of shed load, the priority load threshold being lower than the shed load threshold, with when the analysis and control means determines that a load level of the energy store is lower than the priority load threshold and that the detected temperature of the clutch is greater than the minimum temperature, the analysis and control means reduces or cancels the at least partial tilting of said at least one other driving source and keeps the heat engine in operation.

This makes it possible not to completely discharge an energy store which is then insufficiently charged. An intermediate solution can take place with a heat engine operating at reduced power so as not to consume too much the other motor source (s).

Advantageously, said at least one other driving source comprises at least two other driving sources connected respectively to a drive shaft, a first of said at least two other driving sources being switched as a priority to said at least one second source.

Advantageously, when, after switching the first priority driving source, the detected temperature remains above the maximum temperature of the clutch, said at least one second source is also switched.

The invention also relates to an assembly of a heat engine, of at least one other driving source comprising an energy store, of a clutch connecting at least the heat engine to at least one drive shaft of the vehicle wheels. and an analysis and control means, remarkable in that it implements such a method for protecting the clutch.

Advantageously, said at least one other driving source is an electrical machine, the energy store being at least one battery.

The present invention relates to a hybrid motor vehicle, remarkable in that it comprises such an assembly.

The present invention allows protection of the clutch by controlling its temperature as well as controlling electrical energy, optimizing the cooling system with little or no impact on the performance and control of traction. For a four-wheel drive vehicle, there is no impact on the distribution between front driveshaft and rear driveshaft.

Advantageously, the motor vehicle is a four-wheel drive vehicle with a front drive shaft coupled to a front electric machine and a shaft. rear drive coupled to a rear electric machine, the analysis and control means having priority front electric machine tilting means relative to the rear electric machine tilting means. Brief description of the figures

Other characteristics, aims and advantages of the present invention will become apparent on reading the detailed description which follows and with regard to the appended drawings given by way of non-limiting examples and in which:

[Fig 1] Figure 1 is a diagram of a hybrid vehicle that can implement the method of protection against overheating of a clutch of a heat engine according to the present invention,

[Fig 2] Figure 2 shows an embodiment of a flowchart of the protection method according to an embodiment of the present invention in the case of a hot clutch with respectively sufficient and insufficient energy storage load ,

[Fig 3] Figure 3 shows torque curves provided by a heat engine and two electric machines front and rear as well as virtual limits with and without implementation of the method according to the invention,

[Fig 4] Figure 4 shows three groups of power curves supplied by a heat engine and at least one source other than heat for a four-wheel drive motor vehicle in various cases with and without implementation of the method according to l 'invention.

Detailed description of the invention

All the figures are to be taken in combination and reference may be made in the description relating to a figure to references found in one of the other figures. With reference to FIG. 1, the present invention relates to a method for protecting a clutch 4 of a hybrid vehicle comprising a heat engine 2, at least one driving source 10, 18 other than heat, hereinafter referred to as other source. motor and comprising an energy store 12, the clutch 4 connecting at least the heat engine 2 to at least one wheel drive shaft 8, 26 of the vehicle.

The present invention relates more particularly to an architecture in which the take-off clutch is positioned between the other drive source (s) 10, 18 and the heat engine 2. If a gearbox is closed, then the drive source (s) 10, 18 can be connected directly to the wheels 8, 26.

As will be specified in the description of FIG. 1, the motor source or sources 10, 18 can advantageously be electric machines but can be replaced, for example, by pneumatic or hydraulic technology. The clutch 4 can be controlled so as to respond to a request from this strategy. There is provided a transmission 6 having different speed ratios and connected to the front driving wheels 8 of this vehicle.

An exhaust line 50 has means capable of treating the exhaust gases, including in particular the unburnt gases, coming from the combustion chamber of the heat engine 2, such as for example a particulate filter and / or an oxidation catalyst . The input shaft of the transmission 6 receiving the movement of the clutch 4, has as another driving source a front traction electric machine 10 powered by a second low voltage traction battery 12, as an energy store. In this way, the front electric machine 10 can deliver torque to the driving wheels 8 without going through the clutch 4, using the different speed ratios offered by the transmission 6.

An on-board charger 14 can be connected by an external socket 16 to an electricity distribution network, to recharge the second traction battery 12 when the vehicle is stationary. The second traction battery 12 has a low voltage, which may for example be 220 or 300 volts.

The second traction battery 12 also supplies a rear electric traction machine 18 successively connected by a reduction gear 20 and a clutch system 22, to a rear differential 24 distributing the movement towards the rear wheels 26 of the vehicle. An alternator 30, also referred to as an alternator-starter, permanently connected by a belt 32 to the heat engine 2, supplies an on-board network, called an auxiliary circuit, comprising a battery of the very low voltage auxiliary circuit 34.

In addition, the battery of the very low voltage auxiliary circuit 34, also called the first battery as opposed to the second traction battery 12, can be charged by a DC / DC voltage converter 36, receiving electrical energy from the second traction battery. 12 or a front 10 or rear 18 electric machine if the energy level of this second traction battery 12 is insufficient.

When the vehicle is braked or when the accelerator pedal is released, the electric machines 10, 18 work as a generator, delivering braking torque, to recharge the second traction battery 12 and recover energy.

An analysis and control means, not shown in Figure 1, controls the operation of such a powertrain to meet the demands of the driver while optimizing energy consumption and emissions of polluting gases according to conventional strategies.

In this exemplary embodiment, the second traction battery 12 constitutes the energy store according to the invention while the assembly formed by the electric machine before traction 10 and the rear electric traction machine 18 constitutes the other driving source according to the invention.

In general, the other motor source or sources 10, 18, namely for example the electric machines of FIG. 1, have two modes of actuation.

The first mode is an engine mode in which they supply energy so as to deliver traction or assistance torque to the heat engine 2.

The second mode is a generator mode in which they store the energy supplied by the heat engine 2 via the energy store 12.

The heat engine 2 and the other drive source (s) 10, 18 respectively provide heat engine torque and traction or assistance torque intended to meet an instantaneous drive power demand on the part of the driver.

As previously mentioned, the analysis and control means are able to control the heat engine 2 and the other motor source (s) 10, 18. A virtual limitation of the heat engine 2 is set by the analysis means.

Above this virtual limitation, the analysis and control means require the other motor source (s) 10, 18 to operate at least partially in motor mode, the demand for instantaneous motor power on the part of the driver then having priority. so that if a traction or assistance torque is necessary or desirable in response to this desire of the driver expressed as a torque in Newton meters (Nm), the analysis and control means at least partially switch the other (s) motor sources 10, 18 in motor mode, the time to meet the demand for instantaneous motor power.

At least partial means that in the case of several other driving sources 10, 18 only part of the other driving sources can be switched.

According to the invention for protection against overheating of the clutch 4, the virtual limitation takes into account at least one effective temperature of the clutch 4 as well as a speed difference between a crankshaft associated with the heat engine and said at least a drive shaft.

A maximum temperature of the clutch 4 is thus predetermined so as not to irreversibly damage this clutch.

The at least partial switching of the other driving source (s) 10, 18 in engine mode takes place when a detected temperature of the clutch 4 is greater than the predetermined maximum temperature of the clutch 4 and in the presence of a deviation. speed between upstream and downstream of the clutch, a source of clutch heating. The torque transmitted by the clutch and consequently the torque supplied by the heat engine 2 are then reduced, or even canceled.

Tipping is more suitable for low engine speed. Conversely, with a hot clutch and high speed, therefore with the clutch closed, it is however possible to continue to use the heat engine 2 without increasing the temperature of the clutch 4.

The other driving source (s) 10 and 18 are therefore used to limit the overheating of the clutch 4. The heat engine 2 is then less stressed, which makes it possible to reduce the energy dissipated in the clutch 4.

Thus, the lower the speed delta, the higher the torque that can be transmitted before use of the other electrical source (s). With this mechanism a certain maximum power of dissipation is authorized in the clutch 4. When the temperature of the clutch will be close to its maximum temperature, the maximum authorized power will be close to the thermal dissipation power of the clutch 4 and without exceed it so as not to increase the temperature of the clutch.

The torque transmitted by clutch 2 can be reduced until it is canceled, with heat engine 2 stopped.

This is possible when the torque demand by the driver is reduced or when the energy store 12 is sufficiently charged.

The heat engine 2 also supplies the energy store 12 during its operation via the alternator or starter-alternator, which can also heat up the clutch 4. To anticipate maximum heating of the clutch 4 or slow down this heating. , it can be envisaged to implement at least partial and progressive switching of the other motor source (s) 10, 18 in motor mode from a predetermined minimum temperature 50% lower than the maximum temperature.

Prior to at least partial switching of the other motor source (s) 10, 18 in motor mode, the analysis and control means can first of all require the heat engine not to supply the energy store 12 when the temperature is reached. detected of clutch 4 is higher than the minimum temperature of clutch 4. Heat engine 2 is then less stressed and heats up less like clutch 4.

Later, the switching of the other driving source (s) 12, 18 occurs when the temperature detected even without power supply to the energy store 12 becomes higher than the maximum temperature of the clutch 4.

On the other hand, for prevention, this at least partial tilting can take place before this maximum temperature is reached when a clutch heating gradient is important by leading to a too rapid foreseeable reaching of the maximum temperature of the clutch. The determination of an excessively large heating gradient is within the competence of those skilled in the art, in particular taking into account the model of the clutch. The virtual limitation can also take into account two load thresholds of the energy store 12 predefined in the analysis and control means.

A first threshold can be defined as a priority load threshold and a second threshold can be defined as a shed load threshold. The priority load threshold is lower than the load shedding threshold.

When the analysis and control means determines that a charge level of the energy store 12 is below the priority charge threshold and that the detected temperature of the clutch 4 is above the minimum temperature, the means of analysis and control can reduce or cancel the at least partial tilting of said at least one other driving source 10, 18 and keeps the heat engine 2 in operation.

FIG. 2 shows a flowchart of the protection method according to the present invention. Reference C symbolizes a hot clutch. It is then possible to proceed either with no luring of the target recharging power, which is referenced A, this in the case where the charge of the energy store is insufficient or with a luring of the target recharging power, which is referenced B in the case where the charge of the energy store is sufficient.

In case B, an attempt is made to push the override power until later to avoid further heating the clutch by luring the override power into an acceptable energy store load range.

If, despite this, it is necessary to achieve priority power, then the behavior of the powertrain is identical with the clutch hot or not hot, protection against overheating of the clutch no longer taking priority.

When at least two other motor sources connected respectively to a drive shaft are present, it is possible to switch only a first 10 of said at least two other motor sources 10, 18 in priority to said at least one second source 18.

However, when, after the switching of the first prime mover source 10, the detected temperature remains above the maximum temperature of the clutch 4, the second source 18 is also switched. This applies consecutively to several other power sources present in the hybrid vehicle.

Referring again mainly to Figure 1, the present invention also relates to an assembly of a heat engine 2, at least one other motor source 10, 18 comprising an energy store 12, a clutch 4 connecting at least the engine thermal 2 to at least one drive shaft of the vehicle wheels and of an analysis and control means. The assembly thus produced implements a method for protecting the clutch 4 as previously described, essentially by means of calculation present in the analysis and control means for determining the virtual limitation as a function of the temperature. measured by a temperature sensor or estimated of the clutch and the speed deviation measured by sensors of rotation of the crankshaft and the shaft or shafts of wheels.

The other driving source (s) 10, 18 can be electrical machines, the energy store 12 being able to be at least one battery.

The present invention relates to a hybrid motor vehicle comprising an assembly as described above.

The motor vehicle may be a four-wheel drive vehicle with a front drive shaft coupled to a front electric machine 10 and a rear drive shaft coupled to a rear electric machine 18.

Each other driving source 10, 18 can be located between the clutch 4 of the motor vehicle and the wheels, or directly on the wheels.

The analysis and control means may have tilting means of the front electric machine 10 with priority over the tilting means of the rear electric machine 18. This is not, however, limiting.

The virtual limitation for the protection of the clutch 4 depends on the temperature of the clutch and the speed difference between the input shaft and the crankshaft.

The rejection here preferably takes place on the front electric machine 10 despite the fact that the rear electric machine 18 frequently has better efficiency.

As the torque distribution will depend on the speed deviation, it will be very dynamic, which is why we favor the front electric machine over the rear electric machine so as not to have any repercussions on the torque repair. on front and rear shafts.

If the front electric machine 10 is not able to satisfy the take-off aid, the rear electric machine 18 will take care of it. It is advantageous for the modification of the torque distribution between the heat engine 2 and the other driving source (s) to have no impact on the shift laws due to the rapid dynamics of the speed delta. The energy store 12 can be a traction battery. In the event of so-called priority recharging of the traction battery, the strategy of unloading the heat engine either by disconnecting it from the alternator-starter or by reducing the torque supply power cannot be applied so as not to empty the traction battery. However, it is possible to temporarily shift the priority load threshold by reducing it so that the use of one or more other motor sources can be favored.

The front electric machine is used to compensate for the hot clutch 4 despite the rear electric machine having priority because this avoids a torque distribution impact.

Figure 3 shows two series of torque curves C in Newtons. meter (N.m).

For the first upper series of curves, the C TAV curve is the front axle torque curve, the C TAR curve is the rear axle torque curve. It is visible that the upper horizontal line symbolizing the virtual limit Ls without implementation of the method for protecting the clutch from overheating is greater than the lower horizontal line symbolizing the virtual limit L with implementation of the method.

For the second lower series of curves, the consMth curve is the torque setpoint curve transmitted by the clutch, the AR advise curve is the torque reference curve supplied by the rear electric machine and the AV advise curve is the curve of torque setpoint supplied by the front electric machine.

The virtual limit Ls is the virtual limit without implementation of the method for protecting the clutch from overheating and is greater than the virtual limit L with the implementation of the method. The references Le AV and Le AR are respectively the virtual limits of the front electric machine and of the rear electric machine.

Figure 4 shows three groups of power curves P in kWatt (kW) as a function of time t in seconds (s) for a motor vehicle with a heat engine and at least one motive source other than heat, the vehicle being four wheels motor. The first group of curves shows a raw priority power curve Pp b, a priority power curve as a function of a clutch temperature Pp T and a minimum priority power curve for the protection of the load contained in the storage device d energy Ppmi.

The second series of curves below the first series shows a minimum priority power curve for the protection of the load contained in the energy store, a raw priority power curve and a priority power curve as a function of a temperature. of the clutch in analogy with the first series of curves but without these three curves being referenced.

In addition, the second set of curves shows a synthetic priority power curve for the protection of the Psp clutch.

The third series of curves below the second series shows a minimum priority power curve for the protection of the load contained in the energy store, a raw priority power curve and a priority power curve. as a function of a clutch temperature in analogy with the first and second series of curves but without these three curves being referenced.

In addition, the third series of curves shows a final coordinated Ppfc priority power curve. In Oval 01 of the first set of curves, the clutch heats up. The power to be taken from the heat engine is limited or even canceled by the electrical system including the energy store in order to prevent the clutch from slipping further.

In Oval 02 of the second set of curves, the clutch heats up but the charge level of the energy store drops below the priority charge threshold. Priority power inhibition is performed to ensure minimum recharging in order to have a charge level above the priority charge threshold.

In Oval 03 of the third set of curves, the clutch heats up. The final power is finally reduced if the priority load threshold is exceeded. This reduction can preferably be done at low speed because with a hot clutch and a high speed whereby the clutch is closed, it is possible to continue charging the energy store without causing an increase in the temperature of the clutch.

The invention is in no way limited to the embodiments described and illustrated which have been given only by way of example.

Claims

1. A method of protecting a clutch (4) of a hybrid vehicle comprising a heat engine (2), at least one other driving source (10, 18) comprising an energy store (12), the clutch ( 4) connecting at least the heat engine to at least one drive shaft of the vehicle's wheels, said at least one other drive source (10, 18) having two actuation modes, one engine mode in which it supplies power. energy so as to deliver a traction or assistance torque to the heat engine (2) and a generator mode in which it stores energy supplied by the heat engine (2) via the energy store (12), the heat engine (2) and said at least one other motive power source (10, 18) supplying respectively a thermal engine torque and a traction or assistance torque intended to meet an instantaneous motive power demand on the part of the driver, a analysis and control means being able to control the heat engine (2) and said e at least one other motive source (10, 18), a virtual limitation of the heat engine being set by the analysis means above which limitation the analysis and control means imposes on said at least one other motive source (10, 18) to operate at least partially in engine mode, the demand for instantaneous motive power on the part of the driver then having priority so that if a traction or assistance torque is necessary or desirable in response to this desire, the analysis and control means at least partially switch said at least one other driving source (10, 18) to motor mode the time to meet the demand for instantaneous driving power, characterized in that the virtual limitation takes into account at least one effective temperature of the clutch (4) as well as a speed difference between a crankshaft associated with the heat engine and said at least one drive shaft, a maximum temperature of the clutch (4) being predetermined, the at least partial switching of said at least one other driving source (10, 18) in engine mode taking place at least when a detected temperature of the clutch (4) is greater than the maximum temperature of the clutch (4) and in the presence of a speed difference between the upstream and downstream side of the clutch (4), the torque transmitted by the clutch (2) and consequently the torque supplied by the heat engine (2 ) being then reduced.

2. Method according to the preceding claim, in which a gradual implementation of the at least partial switching of said at least one other motor source in motor mode is carried out from a predetermined minimum temperature 50% lower than the maximum temperature. .

3. Method according to the preceding claim, wherein, prior to the at least partial tilting of said at least one other drive source (10, 18) in engine mode, the analysis and control means firstly impose on the heat engine not to supply the energy store (12) when the detected temperature of the clutch (4) is higher than the minimum temperature of the clutch (4).

4. Method according to any one of the two preceding claims, in which the virtual limitation also takes into account two load thresholds of the energy store (12) predefined in the analysis and control means, one being defined. as a priority load threshold and the other being defined as a shed load threshold, the priority load threshold being lower than the shed load threshold, with when the analysis and control means determines that a load level of the energy store (12) is below the priority load threshold and the detected temperature of the clutch (4) is greater than the minimum temperature, the analysis and control means reduces or cancels the at least partial tilting of said at least one other driving source (10, 18) and keeps the heat engine (2) in operation.

5. Method according to any one of the preceding claims, wherein said at least one other drive source (10, 18) comprises at least two other drive sources respectively connected to a drive shaft, a first (10) of said at least two other motor sources (10, 18) being switched in priority to said at least one second source (18).

6. Method according to the preceding claim, wherein, when, after the switching of the first motor source (10) priority, the detected temperature remains above the maximum temperature of the clutch (4), said at least one second source ( 18) is also tilted.

7. Assembly of a heat engine (2), of at least one other motor source (10, 18) comprising an energy store (12), of a clutch (4) connecting at least the heat engine (2). ) to at least one drive shaft of the vehicle's wheels and of an analysis and control means, characterized in that it implements a method for protecting the clutch (4) according to any one of the preceding claims.

8. Assembly according to the preceding claim, wherein said at least one other motor source (10, 18) is an electrical machine, the energy store (12) being at least one battery.

9. Hybrid motor vehicle, characterized in that it comprises an assembly according to any one of claims 7 or 8.

10. Motor vehicle according to the preceding claim, which is a four-wheel drive vehicle with a front drive shaft coupled to a front electric machine (10) and a rear drive shaft coupled to a rear electric machine (18), the analysis and control means having tilting means of the front electric machine (10) with priority over the tilting means of the rear electric machine (18).