EP1853471A1

EP1853471A1 - Method for power transmission between a heat engine and the wheels of a motor vehicle and related device

Info

Publication number: EP1853471A1
Application number: EP06709530A
Authority: EP
Inventors: Christophe Cottard; Yvan Le Neindre; Gaëtan ROCQ
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2005-03-01
Filing date: 2006-02-23
Publication date: 2007-11-14
Also published as: JP2008532827A; CN101189150A; WO2006092521A1; FR2882700A1; US20080146406A1; FR2882700B1; BRPI0606198A2

Abstract

The invention essentially concerns a device (1.1) for a motor vehicle power transmission. Said device (1.1) comprises a traction chain consisting of a heat engine (2), a clutch (3) including first and second clutch discs (8, 9), an electrical machine (4), and wheels (6). The shaft (10) of the machine (4) is further connected to a shaft (12) of the wheels (6). The invention is characterized in that said transmission device (1.1) comprises a starter system (7) mechanically independent of the electrical machine (4). Said starter system (7) is connected to the heat engine (2).

Description

A method of transmitting power between a heat engine and wheels of a motor vehicle and associated device.

The present invention relates to a device for transmitting power between a heat engine and wheels of a motor vehicle. The invention aims to make more comfortable driving this vehicle, ensuring in particular the continuity of the torque applied to the wheels. The invention finds a particularly advantageous application in the field of motor vehicles, but it could also be implemented in any type of hybrid land vehicle.

In this text, the term "start" is used to designate the rotation of the crankshaft of the engine. The term "take-off" is used to refer to the motion of the vehicle as it moves from zero speed to non-zero speed. The term "actuation" is used for the electric machine when it is turned on.

Hybrid vehicles are known that combine the use of thermal energy and electrical energy to achieve traction. This combination of energies is carried out so as to optimize the energy efficiency of such vehicles. This optimization of fuel efficiency allows the hybrid vehicle to pollute and consume much less than vehicles that operate solely on thermal energy and whose performance is not optimized. Several types of hybrid power transmission devices are known.

Hybrid type transmission devices comprising a motor and a pair of electrical machines are known first. The wheel shaft, the motor shaft and the shafts of the two machines are interconnected via a mechanical assembly. This mechanical assembly generally consists of at least two planetary gear trains. Such a transmission device is described in the French application FR-A-2832357.

Hybrid type transmission devices including a heat engine and a single electric machine are also known. A shaft of this engine and a shaft of this electric machine are connected between them via a clutch. Such a device is likely to operate in two different modes. In a first mode called electric mode, only the electric machine drives the wheel shaft of the vehicle. In a second mode called hybrid mode, the electric machine and the engine together drive the wheel shaft of the vehicle.

In the hybrid mode, the power provided by the electric machine makes it possible to adjust the torque applied to the wheel shaft while adapting the torque and the speed of the engine to an operating point where the energy consumption is optimized. For this purpose, each member of the transmission device: heat engine, clutch, electric machine and speed variator element, is controlled by a close control device which is itself controlled by a specific computer called supervisory computer. This calculator can be independent or integrated into another computer, such as the engine computer. This supervision computer executes programs for synchronizing among themselves the actions of the different elements of the transmission device. This synchronization is performed in such a way as to best respond to a desire to accelerate a driver. More precisely, according to the acceleration desired by the user and the vehicle's driving conditions, the supervision computer, which controls the various members of the device, decides on the mode of operation, coordinates the transient phases of the various components, and selects points of operation of the engine and the electric machine. By rolling conditions is meant vehicle parameters as well as external parameters likely to influence the driving of the vehicle. The vehicle speed and acceleration are for example vehicle parameters, while the degree of inclination of a slope on which the vehicle rolls or the ambient temperature constitute external parameters. FIG. 1 shows a schematic representation of a transmission device 1 according to the state of the art. This transmission device 1 comprises a heat engine 2, a clutch 3, an electric machine 4, a speed variator element 5 such as a gearbox or a variator, and wheels 6 which form a power train. More specifically, the clutch 3 comprises a first disk 8 and a second disc 9 clutch. The first clutch disk 8 is connected to a shaft 10 of the heat engine 2. And the second clutch disk 9 is connected to a shaft 11 of the electric machine 4. In addition, the shaft 11 of the electric machine 4 and a shaft 12 of the wheels 6 are respectively connected to an input 13 and an output 14 of the speed variator element.

As we have seen, the transmission device 1 is capable of operating in two different modes. In the electric mode, the shaft 12 of the wheels 6 is driven by the electric machine 4 only. The clutch 3 is then open, so that the shaft 10 of the motor 2 and the shaft 11 of the electric machine 4 are not coupled to each other. In this electric mode, the electric machine 4 generally behaves as a motor. Thus, in a particular embodiment, the machine 4 draws energy from a storage system 18, such as a battery, particularly via an inverter 19. The battery 18 delivers a DC voltage signal. In the electrical mode, the inverter 19 thus transforms the DC voltage signal observable between the terminals 20 and 21 of the battery, into AC voltage signals which are applied to phases 22-24 of the electric machine 4.

In the hybrid mode, the shaft 12 of the wheels 6 is driven by the heat engine 2 and the electric machine 4. The clutch 3 is then closed, so that the shaft 10 of the engine 2 and the shaft 11 of the wheels 6 be coupled together. The electric machine 4 generally behaves as a motor or a generator and transmits power to the shaft 12 of the wheels 6 to adjust the observable torque on the shaft 12 of the wheels 6 to the target torque. In the same way as that explained above, the machine 4 transfers energy with the battery 18.

In the electric mode and the hybrid mode, during recovery phases that correspond to a slowing down of the vehicle, the electric machine 4 behaves as a generator. During these recovery phases, the electric machine 4 supplies energy to the battery 18. The inverter 19 then transforms the AC voltage signals observable on the phases 22-24 of the electric machine 4 into a continuous voltage signal which is applied to the terminals 20 and 21 of the battery 18.

In practice, the electric machine 4 is a three-phase synchronous machine. Machines of this type have the advantage of being compact and to have a good return.

In a particular embodiment, the transmission device 1 comprises a flywheel 25. This flywheel 25 contributes to ensuring a filtration function of the ascyclism to ensure continuity in the transmission of the torque of the engine 2 to the shaft 6 of the wheels 12.

Furthermore, the transmission device 1 according to the state of the art comprises an independent control unit here constituted by a supervision computer 26. This supervision computer 26 comprises a microprocessor 26.1, a program memory 26.2, a data memory 26.3, and an interface 26.4 of inputs-outputs connected to each other via a communication bus 31.

The data memory 26.3 comprises data D1-DN corresponding in particular to the characteristics of the various organs of the transmission device 1, namely the heat engine 2, the clutch 3, the electric machine 4 and the speed variator element 5. Some of the data D1-DN correspond for example to the response times of these organs 2-5. Other data D1-DN correspond, for example, to maximum torques and minimum torques applicable to shafts associated with members 2-5. The input-output interface 26.4 receives M1-MN signals observable at the output of sensors (not shown). These sensors make it possible to detect the driving conditions of the vehicle. For example, acceleration and speed sensors make it possible to know respectively the acceleration and the speed of the vehicle at a given instant. A tilt sensor can tell if the vehicle is on a slope or not. In addition, the interface 26.4 receives a MACC signal corresponding to a torque to the desired wheel by a driver. Indeed, when he wants to accelerate, the driver presses with his foot 30 on a pedal 29. Depending on the degree of depression of this pedal 29, the MACC signal is generated.

According to the data D1-DN, the driving conditions, and the desired acceleration by the driver, the microprocessor 26.1 executes one of the programs P1-PN which generates the operation of the transmission device 1 in a particular mode, and the adjustment of the observable torque on the shaft 12 of the wheels 6. More precisely, when the execution of one of the programs P1-PN, the microprocessor 26 controls the interface 26.4, so that signals OMTH, OEMB, OMEL and OBV are respectively transmitted to the engine 2, the clutch 3, the electric machine 4 and the dimmer element 5 to control them.

In the case of an operating mode change, some of the P1-PN programs generate OMTH, OEMB, OMEL, and OBV signal transmissions to transition from one mode to another.

In addition, the organs 2-5 of the transmission device 1 each comprise an internal control system which is not shown. These control systems make it possible to regulate the value of the observable torques on trees associated with these members 2-5.

In one example, for a request for low acceleration from the driver, the supervision computer 26 controls the various members 2-5, so as to operate the transmission device 1 in the electrical mode. The torque applied to the shaft 12 of the wheels 6 is then equal to the observable torque on the shaft 11 of the electric machine 4, to a gear ratio. On the other hand, for a strong acceleration request, the supervision computer 26 controls the various members 2-5, so as to operate the transmission device 1 in the hybrid mode. The torque applied to the shaft 12 of the wheels 6 is then equal to the observable torque on the shaft 11 of the electric machine 4, which is then equal to the sum of the observable torque on the shaft 10 of the heat engine 2 and that of the machine 4. When switching from electric mode to hybrid mode, there is a transient regime, during which the torque of the engine 2 is not available. Indeed, during this transient regime, the engine 2 starts and its shaft 10 begins to mate with the shaft 11 of the electric machine 4, without the torque of the engine 2 is transmitted to the shaft 6 12. This transient is particularly critical since it can occur more than two hundred times per hour of driving, regardless of the speed of the vehicle and gearbox engaged.

During the transient regime, the supervision computer 26 must therefore control the clutch 3 in a specific and precise manner, so that the driver does not even realize the change in vehicle mode. The response time of the engine 2 must therefore be minimal during an acceleration. In addition, it is necessary to ensure that the desired level of acceleration is maintained by the driver throughout the transient regime, while ensuring acoustic comfort to the driver. Indeed, runaway of the engine must be avoided, and the engine start noise should not be heard.

In the existing transmission devices 1, to switch from an electric mode to a hybrid mode, the clutch 3 transmits a breakaway torque to the heat engine 2. This breakaway torque is intended to drive the engine 2 in rotation and start it up. During transmission of the tearing torque, the electric machine 4 applies a torque which compensates for this breakaway torque, so that there is no variation in the torque applied to the shaft 12 of the wheels 6. The FIG. 2 shows, in particular, chronograms of signals observable on the various members 2-5 of the transmission device 1 according to the state of the art. These signals are observable during a transient regime, when the transmission device 1 passes from an electrical operating mode to a hybrid operating mode. More specifically, FIG. 2 shows the torque signals CEMB,

CMEL and CMTH which respectively correspond to the observable torque on the clutch 3, on the shaft 11 of the electric machine 4, and on the shaft 10 of the heat engine 2.

FIG. 2 also shows the evolution over time of torque signals CCONS and CREEL respectively corresponding to the setpoint torque to be applied to the shaft 12 of the wheels 6 and to the torque actually observable on this shaft 12 of the wheels 6. The signal of DCONS torque setpoint is developed from the MACC signal and M1-MN signals from the sensors. The signals OEMB and OMEL are emitted by the computer 26 to the clutch 3 and the electric machine 4 to control them. For simplicity, the OMTH and OBV signals which respectively control the heat engine 2 and the electric machine 4 are not shown. Finally, Figure 2 shows on the same chronogram the evolution in the time of the speed of rotation WMEL of the electric machine 4, and the speed of rotation WMTH of the heat engine 2.

Between instants t0 and t1, the reference torque CCONS increases exponentially, in particular in correspondence with a request for acceleration of the driver. This setpoint torque CCONS increases, so that at time t1, it has already reached the peak torque CMELMAX of the electric machine 4. Furthermore, between times t0 and t1, the electric machine 4 has a pair CMEL which increases to stabilize at the nominal torque CMELNOM of this electric machine 4. The rotation speed WMEL of the electric machine 4 is non-zero and increases linearly. The heat engine 2 is at a standstill and its shaft 10 is not coupled with the shaft 11 of the electric machine 4. The heat engine 2 therefore has a pair CMTH and a rotation speed WMTH which are both zero . As the engine is stopped, the torque CREEL measured on the shaft 12 of the wheels 6 is equal to the torque CMEL of the electric machine

4. The torque CREEL measured on the shaft 12 is therefore less than the expected torque CCONS expected. No torque is observable on the clutch 3.

Between times t1 and t2, the transmission device 1 enters a first transient phase. In this first phase, the reference torque CCONS is always globally equal to the peak torque CMELMAX of the electrical machine 4. At time t1, a first signal 31 is emitted by the supervision computer 26 to the clutch 3. This signal 31 controls this clutch 3, so that this clutch 3 transmits a breakaway torque CARR to the engine 2 to make it come into rotation. This breakaway torque CARR is taken from the drive train. Therefore, a second signal 32 is emitted by the computer 26 at the same time as the signal 31, and to the electrical machine 4. This signal 32 controls the electric machine 4, so that its CMEL couple compensates for the torque. CARR pulling taken by the clutch 3. Thus, in this first transient phase, the clutch torque signal CEMB decreases and reaches a negative value equal to the value of the tearing torque CARR. Meanwhile, the torque signal CMEL of the electric machine 4 increases by a value - CARR opposite the value of the tearing torque CARR. A torque signal CMTH of the heat engine 2 corresponding to the starting torque of this engine 2 is then observable. The heat engine 2 then has a speed of rotation WMTH which increases, but which remains lower than the speed of rotation WMEL of the electric machine 4. The heat engine 2 still does not transmit its torque to the shaft 6 of wheels 12, since it is not coupled with the shaft 11 of the electric machine 4. The torque CREEL measured on the shaft 12 is therefore always less than the expected torque CCONS expected on this shaft 12. The first transitional phase aims to to pass to the heat engine 2 his first compressions. Thus, the heat engine 2 performs between two and four revolutions, without its shaft 10 being coupled with the shaft 11 of the electric machine 4. After these few turns, the heat engine 2 operates at a speed WMTH sufficient to be independent.

Between times t2 and t3, the transmission device 1 enters a second transient phase. In this second phase, the setpoint torque CCONS is always globally equal to CMELMAX. Moreover, the torque signal CMEL of the electrical machine 4 decreases from a value CNOM-CARR to the nominal torque value CMELNOM of the electric machine 4. And the torque signal CEMB of the clutch 3 becomes zero again. The transmission phase of the tearing torque thus ends between t2 and t3. As the shaft 10 of the heat engine 2 is still not coupled with the shaft 11 of the electric machine 4, the torque CREEL is always equal to the CMEL couple of the electric machine 4 and remains below the setpoint torque CCONS. The rotation speed WMEL of the shaft 11 of the electric machine 4 increases linearly. The speed of rotation WMTH of the shaft 10 of the heat engine 2 increases to reach at time t3 the speed of rotation WMEL of the electric machine 4. This second transient phase is thus intended to rev up the engine 2 to allow, as will be seen below, a sliding of the clutch disks 8 and 9 relative to each other. Between times t3 and t4, the transmission device 1 enters a third transient phase. In this third phase, the set torque CCONS is always globally equal to the peak torque CMELMAX of the electric machine 4. As soon as the rotation speed WMTH of the heat engine 2 is greater than that of the electric machine 4, a signal 33 is emitted by the supervision computer 26 to the clutch 3. This signal 33 controls the sliding of the disks 8 and 9 clutch relative to each other. The heat engine 2 then transmits a portion of its torque CMTH to the shaft 12 of the wheels 6 via the clutch 3. The torque signal CEMB observable on the clutch 3 then increases linearly, while the signal of CMEL torque of the electric machine 4 decreases globally symmetrically with respect to the torque signal CEMB of the clutch 3. The torque CREEL then increases linearly since the heat engine 2 begins to transmit torque to the shaft 12 of the wheels 6. Alternatively, the torque of the electric machine 4 could be controlled so that its torque maintains the CMELMAX value. The heat engine 2 then adapts its torque, so that the target torque CCONS is satisfied.

Between times t4 and t5, the transmission device 1 enters a fourth transitional phase. In this fourth transient phase, it firstly occurs a docking of the engine, then, in a second step, a closure of the clutch 3. More specifically, during the docking of the engine 2, the rotational speed WMTH of the heat engine 2 converges towards that of the electric machine 4. When these two speeds are equal, a signal 34 is emitted to the clutch 3 by the supervision computer 26. This signal 34 controls the closing of this clutch 3. The rotational speeds of the engine WMTH and the machine WMEL are then identical throughout this phase between t4 and t5. The torque CEMB of the clutch 3 increases, while the torque signal CMEL of the electric machine 4 decreases in a generally symmetrical manner with respect to the torque signal CEMB of the clutch 3. This torque CMEL compensates for the torque CEMB in order to achieve CCONS.

Between times t5 and t6, the transmission device 1 enters a fifth transitional phase. In this fifth phase, the reference torque CCONS increases slightly, in the manner of a step for example. The motor members 2 and 4 of the device 1 then converge to their optimal torque setpoint signal, if they have not already reached it. The clutch is kept closed and its torque CEMB increases to exceed the CMTH. Rotational speeds of the engine WMTH and WMEL electric machine increase with the speed of the vehicle. The CREEL torque signal follows the evolution of the reference torque signal CCONS.

The management of this transitional regime presents major difficulties of implementation. These difficulties are due essentially to the great sensitivity of the organs 2-5. Indeed, from one temperature to another, the organs 2-5 do not have the same characteristics. Moreover, from one temperature to another, couples observable on trees 2-5 associated with these organs vary. With such a transmission device 1, it is therefore difficult to obtain a constant starting time, whatever the driving conditions. Indeed, this starting time varies significantly depending on the temperature of the engine 2. This start time is much shorter when the engine 2 is hot than when it is cold. In addition, it is difficult to perfectly coincide over time the removal of the pulling torque CARR on the clutch 3 and the application of the CNOM-CARR compensating torque by the electric machine 4. Now this synchronization in the samples of the torque is necessary to guarantee the absence of a break in torque when starting the engine 2.

It is also difficult to apply a compensation torque exactly equal to the torque taken by the clutch. Indeed, it is difficult to estimate the torque to be applied to the clutch 3 during the transmission of the tearing torque CARR according to the temperature of the heat engine 2. Furthermore, between times t1 and t4, the electric machine 4 can not supply its CMELMAX peak torque to achieve the CCONS setpoint torque. The electric machine 4 can not operate at its peak torque because it must have a torque guard to compensate for the breakaway torque CARR taken by the clutch 3, regardless of the speed of the vehicle. In other words, the electric machine 4 must always operate at its maximum nominal torque CMELNOM, so as to be able to operate at any time at a higher torque allowing it to compensate for the breakaway torque CARR.

However, this couple guard is not always available. FIG. 3 thus shows that the torque guard of the electric machine 4 is available only when its WMEL operating regime is lower than its basic WB regime. More precisely, FIG. 3 represents the observable CMEL couple on the shaft 11 of the electric machine 4 as a function of its rotation speed WMEL, for a given power. The curve PCRETE represented in dashed lines corresponds to a peak power of the electric machine 4. The PNOM curve represented in dashed lines corresponds to a nominal power of the electric machine 4. The hatched portion of the figure corresponds to the torque guard of the electric machine 4. For a WMEL speed of the electric machine 4 lower than the basic speed WB, the difference between the value of the peak torque CMELMAX and the value of the nominal torque CNOM corresponds to a sufficient torque guard to compensate the torque of tearing CARR. On the other hand, for the WMEL regimes of the electric machine 4 greater than the basic speed WB, the difference in the torque of the electric machine 4 operating at its peak power PCRETE and the torque of the electric machine 4 operating at its nominal power PNOM corresponds insufficient torque protection to compensate for the application of the CARR breakaway torque. Indeed, when the electric machine 4 operates at a higher speed than the basic speed, the torque guard decreases rapidly, substantially in 1 / x. For the speeds of the electric machine 4 higher than the basic speed WB, the starting of the heat engine 2 therefore inevitably results in a sample of torque at the wheel 6. This torque sampling causes a failure between the actual acceleration of the vehicle and the desired acceleration by the driver. In one example, the value of the basic WB regime is 2000 rpm.

The invention therefore proposes in particular to solve these problems of guard torque and synchronization during the transmission of the tearing torque. The invention proposes to start the engine without ever taking torque from the wheel and with identical starting times, regardless of the speed of the electric machine and the temperature of the engine.

To this end, in the invention, the known architecture of the transmission device is completed by a starting system which is independent of the electric machine. In fact, this independent starting system drives the heat engine independently of the machine electric. In the invention, it is no longer the clutch but the starter system that transmits the heat engine its tearing torque in order to start it. Thus, this starting system makes it possible to separate the problems of starting the engine with those of the vehicle power train.

The introduction of the starter system leads to a simplification of the control of the clutch and the electric machine during transient conditions. The new architecture thus makes it possible to avoid synchronization between the actions of the clutch and the electric machine. In this new architecture, the problem of estimating the torque applied by the electric machine to compensate for the breakaway torque has disappeared, since the clutch is no longer directly involved in starting the engine.

This starting system also allows a better exploitation of the characteristics of the clutch and the machine. Thus, it is no longer necessary for the electric machine to have a torque guard to compensate for the torque taken by the clutch. If an acceleration so requires, the electric machine can operate at its peak torque to ensure traction of the vehicle, even if the engine is not available. Thus, in general, when acceleration requires, the electric machine operates at its peak torque as the clutch remains open, when starting the engine. And when the clutch is closed, the electric machine is operated at its peak torque, or at a lower torque if a set torque can be met.

In a particular embodiment, the starter system takes the form of a controlled starter.

The invention therefore relates to a power transmission method implementing a power transmission device of a motor vehicle comprising an electric machine connected on the one hand to a heat engine by a clutch and on the other hand to a motor shaft. wheels, in which, to start the engine, when the electric machine is already rotating,

a pulling torque is transmitted to the shaft of the heat engine, characterized in that:

to transmit this breakaway torque, the shaft of the heat engine is rotated by means of a starting system mechanically independent of the electric machine.

In addition, the invention relates to a power transmission device of a motor vehicle comprising an electric machine connected on the one hand to a heat engine by a clutch and on the other hand to a wheel shaft, characterized in that it comprises a mechanically independent starting system of the electric machine, this starting system being connected to the heat engine.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative purposes but in no way limitative of the invention. These figures show:

- Figure 1 (already described): a schematic representation of a power transmission device according to the state of the art;

- Figure 2 (already described): chronograms representing the evolution over time of observable signals on bodies of a transmission device of the state of the art, during a change of mode;

- Figure 3 (already described): a graphical representation of a torque guard of an electric machine; - Figure 4: a schematic representation of a transmission device according to the invention comprising a starter system;

- Figure 5: chronograms representing in particular the evolution in time of observable signals on organs of a transmission device according to the invention, during a change of mode. FIG. 4 shows a schematic representation of a transmission device 1.1 according to the invention. Like the transmission device 1 according to the state of the art, this transmission device 1.1 comprises a heat engine 2, a clutch 3, an electric machine 4, a speed variator element and wheels 6. The four components 2- 5 and the wheels 6 of the vehicle form a pull chain, and are arranged in the same manner as in the transmission device 1 according to the state of the art. In addition, according to the invention, the transmission device 1.1 comprises a starting system 7 connected to the heat engine 2.

This starting system 7 is connected to the engine 2 and drives it in rotation in order to start it. The boot system 7 is mechanically independent of the electric machine 4. In fact, the starting system 7 starts the heat engine 2 without drawing power to the traction chain. Consequently, the starting of the heat engine 2 has no longer any impact on the continuity of the torque applied to the shaft 12 of wheels 6. Moreover, the electric machine 4 no longer has to operate under power to be able to transmit at any time the tearing torque to the heat engine 2. Indeed, as we will see, in the invention, it is the system 7 startup that provides the tearing torque. The starter system 7 therefore never participates in traction.

It is therefore dimensioned accordingly to generate a power just sufficient to start the engine 2, power which is substantially lower than that of the electric machine 4 and which does not require a high supply voltage. In a particular embodiment, the heat engine 2 comprises a first pulley 15 which is attached to one end of its shaft 10. And the starting system 7 comprises a second pulley 16 which is attached to one end of its shaft 31. A belt 17 passes through a groove of these two pulleys 15 and 16, so as to connect the starting system 7 to the heat engine 2.

The electrical machine 4 is here connected to a storage device 18, such as a battery. Alternatively, the storage system 18 is an inertia machine, or a supercapacitor.

In a particular embodiment, the transmission device 1.1 may also include the flywheel 25. This flywheel 25 is connected to the shaft 10 of the engine 2, between this engine 2 and the clutch 3.

Furthermore, the transmission device 1.1 according to the invention also comprises the supervision computer 26. When executing one of the programs P1-PN, the microprocessor 26.1 controls the interface 26.4, so that, in addition to the signals OMTH, OEMB, OMEL, OBV, an ODEM signal is sent to the system 7 start to order it. The OMTH and OMEL signals respectively control the heat engine 2 and the electric machine 4, so that the heat engine 2 is still operating at its optimum operating point where, for a given power, its consumption is minimum. Again, in the case of a change in operating mode, some of the P1-PN programs generate OMTH, OEMB, OMEL, OBV, and ODEM signal transmissions for transition from one mode to another. The starting system 7 also includes an internal control system which is not shown. This control system makes it possible to regulate the value of the breakaway torque that this starting system 7 applies to the shaft 10 of the heat engine 2.

In the invention, the clutch 3 is a dry or wet clutch. FIG. 5 shows, in particular, chronograms of the signals observable on the various members 2-5 of the transmission device 1.1 according to the invention. As for FIG. 2, these signals are observable during the transient regime, when the transmission device 1.1 changes from an electrical operating mode to a hybrid operating mode. The signals associated with the transmission device 1 according to the state of the art are shown in dotted lines to be able to compare them with the signals associated with the transmission device 1.1 according to the invention shown in solid lines. Moreover, in order to be able to compare the different signals, the reference torque signal CCONS is the same as that of FIG. 2.

At time t0, the electric machine 4 has already been actuated, that is to say that it is already rotating. The vehicle has therefore a priori already taken off, that is to say that it is already moving. The heat engine 2 is in turn off: it therefore has a rotation speed WMTH and a torque CMTH zero at time tO.

Between times t0 and t1, the setpoint torque CCONS increases, so that at time t1, it has already reached the peak torque CMELMAX of the electric machine 4. Between instants t1 and t2, the pair CMEL of the Electric machine 4 increases, so as to follow the requested torque CCONS set. Unlike FIG. 2, the electric machine 4 operates at its peak torque CMELMAX when the heat engine 2 is not available. The fact that the machine 4 can operate at its peak torque CMELMAX allows the transmission device 1.1 to provide a torque equal to the requested setpoint torque CCONS. Thus, the torque CREEL measured on the shaft 12 of the wheels 6 corresponds exactly to the torque CCONS of deposit. The torque guard is no longer necessary, since the electric machine 4 is no longer directly involved in starting the heat engine 2. The speed of rotation WMEL of the electric machine 4 is non-zero and increases linearly. The heat engine 2 is still at a standstill and its shaft 10 is not coupled with the shaft 11 of the electric machine 4. The heat engine 2 therefore always has a torque CMTH and a rotation speed WMTH which are zero both.

Between times t1 and t2, the transmission device 1.1 enters a first transient phase. In this first phase, the reference torque CCONS is always equal to the peak torque CMELMAX of the electric machine 4. Unlike the device 1 of the prior art, no torque CEMB is observable on the clutch 3 since this clutch 3 does not transmits more the breakaway torque CARR ensuring the starting of the heat engine 2. The electric machine 4 therefore still operates at its peak torque CMELMAX because it no longer has to compensate during this first phase the breakaway torque CARR. The torque CREEL measured on the shaft 12 is therefore still equal to the reference torque CCONS. At the end of the execution of one of the programs P1-PN by the computer 26, a signal 35 is sent to the system 7 start. This signal 35 controls the starting system 7 which drives the heat engine 2. A torque signal CMTH corresponding to the starting torque of this heat engine 2 is then observable. The heat engine 2 then has a speed WMTH of rotation which is lower than that of the electric machine 4. The heat engine 2 does not yet transmit torque to the shaft 12 of the wheels 6, since it is not yet coupled. with the shaft 11 of the electric machine 4. As in the previous first transient phase, the heat engine 2 thus passes its first compressions so as to reach a sufficient regime to be autonomous. Once the heat engine 2 is autonomous, a signal is emitted by the computer 26 to the starter system 7, so as to cut the starter system 7, in other words stop it.

Between times t2 and t3, the transmission device 1.1 enters a second transient phase. In this second phase, the electric machine 4 still operates at its peak torque CMELMAX. The torque signals CCONS, CREEL, CMEL therefore always have values equal to CMELMAX. The torque signal CMTH of the heat engine 2 decreases slightly, while the speed of rotation WMTH of this heat engine 2 increases to reach at time t3 the speed of rotation WMEL of the electric machine 4. No torque CEMB is observable on the clutch 3. The second phase is again intended to rev up the engine 2 to allow, as will be seen below, a sliding of the discs 8 and 9 clutch 3 the one compared to the other.

Between times t3 and t4, the transmission device 1.1 enters a third transient phase. In this third phase, the set torque CCONS is always equal to the peak torque CMELMAX of the electric machine 4. As with the device 1 of the state of the art, as soon as the rotation speed WMTH of the heat engine 2 is greater than that WMEL of the electric machine 4, a signal 36 is transmitted to the clutch when executing one of the programs P1-PN. This signal 36 controls the sliding of the disks 8 and 9 clutch relative to each other. The heat engine 2 then transmits a portion of its torque CMTH to the shaft 12 of the wheels 6 via the clutch 3. The observable torque on the clutch 3 increases in a calibrated manner and in an example in a linear manner. Indeed, this clutch 3 transmits a torque to the traction chain. The torque signal CMEL of the electric machine 4 then decreases in an example linearly. The CREEL torque is therefore always equal to the setpoint DCONS torque. The torque signal CMTH of the heat engine 2 then enters a second oscillation. In a variant, the electric machine 4 retains a torque equal to CMELMAX and the motor 2 adapts its torque to satisfy the CCONS setpoint.

Between times t4 and t5, the transmission device 1.1 enters a fourth transitional phase. The set torque CCONS is always equal to the peak torque CMELMAX of the electric machine 4. As with the device 1 of the state of the art, in this fourth transient phase, it first occurs a docking of the engine, then in a second step, closing the clutch 3. When docking the heat engine 2, the rotation speed WMTH of the heat engine 2 converges to that WMEL of the electric machine 4, and when these two speeds are substantially equal, a signal 37 is emitted to the clutch 3 to control its closure. In practice, this signal 37 is emitted when the difference between the speed of rotation WMTH of the heat engine 2 and the speed of rotation WMEL of the electric machine 4 is lower in absolute value to a value between 0 and 15% of the speed. 4. The clutch torque CEMB increases until the clutch 3 closes and then stabilizes. The torque signal CMEL of the electric machine 4 always decreases symmetrically with respect to the torque CEMB of the clutch 3. The torque signal CREEL measured on the shaft 12 of wheels 6 is identical to the reference torque signal CCONS.

Between times t5 and t6, the transmission device 1.1 enters a fifth transitional phase. In this fifth phase, the reference torque signal CCONS increases slightly, in a calibrated manner, in the manner of a step, for example. As previously, in this fifth phase, the motor members 2 and 4 of the device 1 converge to their optimal torque setpoint with respect to a consumption of the heat engine 2, if they have not already reached it. Furthermore, the clutch torque signal CEMB increases to maintain the closing of the clutch 3, and exceeds the torque signal of the heat engine 2. The speeds of rotation WMTH and WMEL of the engine 2 and the electric machine 4 increase with the speed of the vehicle.

Thus, when starting the heat engine 2, the clutch 3 is open and remains open for a predetermined time which extends between t0 and t3. This duration may be a function of the setpoint torque CCONS requested by the driver and / or the time that the engine 2 to become autonomous. In a variant, the clutch 3 is already closed when the engine 2 is started. In this variant, the starting system 7 and the electric machine 4 participate together in the transmission of the breakaway torque CARR to the engine 2. for example, the starting system 7 is connected to the heat engine 2 by means of a first reduction unit which has a lower ratio than that of a second reduction unit through which the electric machine 4 and the heat engine 2 are connected, so that the torque applied to the shaft 10 of the heat engine 2 by the system of start 7 is greater than the torque applied to this shaft 10 by the electric machine.

Thanks to the invention, during the entire duration of the transient regime, between t1 and t6, the electric machine 4 has a higher rotation speed WMEL than it possesses when it is used with the transmission device 1 of the state of the art. The hatched portion on the timing diagram of the rotation speeds WMEL and WMTH thus represents the acceleration gain achieved by a device 1.1 according to the invention with respect to the device 1 according to the state of the art. Furthermore, in the invention, during the transmission of the tearing torque, the actions applied to the clutch 3 by the heat engine 2 and the electric machine 4 are independently of one another. An action on the clutch 3 by the electric machine 4 is that of driving the vehicle. An action on the clutch 3 by the engine 2 is actually an action by the starter system 7 which is that of starting the engine 2. The independence of these actions implies that it would be possible to use a clutch 3 that would not be mechanical.

In addition, during the entire duration of the transient regime t1-t6, the torque CREEL measured on the shaft 12 of the wheels 6 is always equal to the target torque CCONS when this target torque is less than or equal to CMELMAX. On the other hand, with the device 1 of the state of the art, the measured torque CREEL was lower than the setpoint torque CCONS.

Thanks to the invention, it therefore eliminates jolts during a start of the engine 2. Indeed, since the start of the engine 2 is performed independently of the electric machine 4, the impact of the start on a Longitudinal dynamic of the vehicle is zero.

In addition, the boot is more robust. Indeed, the starting system 7 starts the heat engine 2 with a generally constant torque, whatever the WMEL speed of the electric machine 4. The start of the engine 2 are fast and of equal quality, regardless of the speed of the electric machine 4.

The electric machine 4 of the device 1.1 according to the invention is dimensioned in the same way as the electric machine 4 of the device 1 of the state of the art. However, since it is possible to exploit peak torque CMELMAX for the traction of the vehicle the time that the engine 2 starts and is available, the response to a desire for acceleration of the driver is almost instantaneous.

To show the interest of the invention, the signals associated with the device 1.1 during the transient regime are represented here for a setpoint torque CCONS generally equal to the peak torque CMELMAX of the electric machine 4. However, the pace of these signals would be very similar to that shown in Figure 5 for CCONS setpoint pairs of different values. Alternatively, the device 1.1 is used to start the engine 2 during a take-off of the vehicle, when the electric machine 4 has not yet been actuated.

Claims

1 - Power transmission method implementing a device (1.1) for power transmission of a motor vehicle comprising an electric machine (4) connected on the one hand to a heat engine (2) by a clutch (3) and on the other hand to a shaft (12) of wheels (6), in which, to start the engine (2), when the electric machine (4) is already rotating,

a breakaway torque (CARR) is transmitted to the shaft (10) of the heat engine (2) by driving the shaft (10) of the heat engine (2) in rotation, with the aid of a system of starting (7) mechanically independent of the electric machine (4), characterized in that:

- The starting system (7) does not participate in the traction of the vehicle.

2 - Process according to claim 1, characterized in that:

- When starting the heat engine (2), the clutch (3) is open and remains open for a predetermined time.

3 - Process according to claim 2, characterized in that: - the electric machine (4) is operated at its peak torque

(CMELMAX), as long as the clutch (3) remains open.

4 - Method according to one of claims 2 to 3, characterized in that:

- after starting the heat engine (2), a rotation speed (WMTH) of the shaft (10) of the heat engine (2) is increased until this speed (WMTH) is greater than that ( WMEL) of the shaft (11) of the electric machine (4).

5 - Method according to one of claims 2 to 4, characterized in that: - after starting the heat engine (2), we slide the discs (8, 9) of the clutch relative to the another, one of the disks (8) of this clutch (3) being connected to a shaft (10) of the heat engine (2), another disk (9) of this clutch (3) being connected to a shaft (11) of the electric machine (4). 6 - Process according to claim 5, characterized in that: - converging a speed (WMTH) of the shaft (10) of the engine (2) to a rotation speed (WMEL) of the shaft (11) of the machine (4), and

the clutch (3) is closed when the rotation speed (WMTH) of the shaft (10) of the heat engine (2) is substantially equal to the rotational speed (WMEL) of the shaft (11) of the electric machine (4).

7 - Method according to one of claims 2 to 6, characterized in that:

- After closing the clutch (3), converts the heat engine (2), and the electric machine (4) to their optimal target torque with respect to a consumption of the engine (2).

8 - Method according to one of claims 1 to 7, characterized in that:

- Once the heat engine (2) is started, it is expected that it passes its first compression to be autonomous, then cut the starter system (7).

9 - Device (1.1) for power transmission of a motor vehicle comprising an electric machine (4) connected on the one hand to a heat engine (2) by a clutch (3) and on the other hand to a shaft (12). ) of the wheels (6), this device (1.1) comprising a starting system (7) mechanically independent of the electric machine (4), this starting system (7) being connected to the heat engine (2), characterized in that :

- The starter system (7) is such that it does not participate in the traction of the vehicle.

10 - Device according to claim 9, characterized in that the clutch (3) is a mechanical clutch.

11 - Device according to claim 10, characterized in that it comprises a first and a second disk (8, 9), the first disk (8) being connected to a shaft (10) of the engine (2) thermal, the second disc (9) clutch being connected to a shaft (11) of the electric machine (4).

12 - Device according to one of claims 9 to 11, characterized in that:

- a shaft (31) of the starter system (7) is connected to a shaft (10) of the engine (2) via a thermal belt (17), this belt (17) passing through a first pulley (15) hooked to the shaft (10) of the engine (2) and a second pulley (16) hooked to the shaft (31) of the starter system (7).

13 - Device according to one of claims 9 to 12, characterized in that it is provided with a flywheel (25) of inertia, the flywheel (25) being connected to the shaft (10) of the thermal engine (2), between this engine (2) and the clutch (3).

14 - Device according to one of claims 9 to 13, characterized in that it comprises a system (18) for storing energy connected to the electric machine (4).

15 - Device according to claim 14, characterized in that:

the storage system (18) is a battery.

16 - Device according to one of claims 9 to 15, characterized in that it comprises a supervision computer (26) which controls changes in operating mode of the device according to received signals (MACC, M 1-MN) corresponding in particular to a requested acceleration.

17 - Device according to claim 16, characterized in that:

- The supervision computer (26) comprises means (26.1-26.4) for operating the heat engine (2) and the electric machine (4) at particular operating points.

18 - Device according to one of claims 9 to 17, characterized in that the starter system (7) is a controlled starter.