EP1028864A1

EP1028864A1 - Motor vehicle with dual engine system

Info

Publication number: EP1028864A1
Application number: EP98954555A
Authority: EP
Inventors: Yves Borgeaud; Benoít CAILLARD; Stéphane HEMEDINGER; William Pannequin
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 1997-11-12
Filing date: 1998-11-10
Publication date: 2000-08-23
Also published as: FR2770808A1; FR2770808B1; WO1999024280A1

Abstract

The invention concerns a motor vehicle with dual engine system comprising an electric engine and a heat engine, wherein a central management unit executes a first task (1200) including the determination of a torque which each engine must provide to supply an engine torque in conformity with the torque requested by the driver, and wherein the heat engine can be stopped. The invention is characterised, at least for some operating modes, the central unit executes a second task (1100) during which the decision to stop or to start the heat engine is taken, and the first and second tasks are executed in parallel, the execution frequency of the second task being less frequently operated than the first.

Description

Motor vehicle with hybrid motorization

The invention relates to an automobi vehicle with hybrid motorization comprising improved means of energy management. The invention relates more particularly to a motor vehicle with hybrid motorization, of the type in which a drive train comprises an electric motor and a heat engine which are capable of contributing to the driving of the vehicle, and of the type in which a central management unit performs a first task comprising the determination of the torque which each engine must supply in order for the power train assembly to supply the vehicle with an engine torque conforming to a torque requested by the driver of the vehicle, and of the type in which the heat engine is capable of being stopped, the vehicle then being driven by the only electric motor supplied with electric current by a storage battery.

In the search for less polluting vehicles than motor vehicles comprising only one heat engine, vehicles with hybrid motorization are presented as a particularly interesting alternative to strictly electric vehicles.

Indeed, the latter have the advantage of not emitting any toxic substances by themselves while being both particularly silent and economical in use. However, electric vehicles get their energy only from the accumulator batteries they carry with them. However, given the poor performance of currently known storage batteries, at least those capable of being used at a reasonable cost in a motor vehicle, electric vehicles can only store a relatively small amount of energy, despite of a substantial mass, which gives them both low autonomy and poor performance.

Also, the solution of a hybrid engine comprising a thermal engine capable of participating in the driving of the vehicle makes it possible to produce vehicles having much higher performance and autonomy, satisfactory for normal use of the vehicle.

There are two main types of hybrid vehicles. In series hybrid vehicles, only the electric motor is capable of driving the drive wheels of the vehicle directly, possibly through a gearbox, a differential and / or a clutch. The electric motor draws its energy from a rechargeable battery of an electric generator which is driven by the heat engine.

In such a type of hybrid vehicle, the electric motor is therefore always in operation and the internal combustion engine can either be stopped, the vehicle then operating in pure electric mode, or be started so that the generator produces electricity to power the electric motor and / or recharge the batteries.

In a parallel hybrid vehicle, the internal combustion engine and the electric motor are both connected, generally by a gearbox system with two inputs, to the drive wheels of the vehicle. Generally, a clutch is interposed between each engine and the drive wheels to allow uncoupling of the engine when it is not used for driving. Motor vehicles of the parallel hybrid type can therefore be driven either using the single electric motor, or using the single combustion engine, or even using the two motors simultaneously. In addition, in some configurations, it it is possible to use the electric motor to start the internal combustion engine and the electric motor can also be "inverted" so that, the internal combustion engine driving the electric motor in rotation, possibly at the same time as it rotates the drive wheels of the vehicle, recharges the batteries.

I t should be noted that there is an alternative embodiment of the hybrid vehicles in parallel in which each of the two thermal and electric motors is coupled not to the same axle, but to different axles.

Whatever the type of hybrid vehicle envisaged, it is therefore necessary to manage as efficiently as possible the control of each of the heat and electric motors to ensure the drive of the vehicle according to the wishes of the driver who determines at each instant the engine torque required to advance the vehicle to accelerate or decelerate the vehicle, or to maintain the vehicle at a stabilized speed.

In particular, the choice of whether or not to use the heat engine is particularly crucial since it makes it possible to determine the autonomy of the vehicle, its performance, all this insofar as the starting of the heat engine is actually possible, which can for example be prohibited in certain areas with particularly heavy traffic or at certain periods to limit pollution.

Furthermore, it is necessary that the transfers of distribution of the power supplied by each of the motors be made in a “transparent” manner for the driver, that is to say by producing only a minimum of disturbances and jerks.

Also, the invention provides a motor vehicle of the type described above, characterized in that, at least for certain operating modes of the power train, the central unit performs a second task during which the stopping or starting of the heat engine is decided, in that the first task and the second task are executed in parallel , and in that the frequency of execution of the second task is lower than that of the first task.

According to other characteristics of the invention: the driver can impose on the power train an electric operating mode in which the heat engine is stopped; the driver can impose on the powertrain a regenerative operating mode in which the heat engine is used in particular to ensure the recharging of the battery; the driver can impose on the powertrain a hybrid operating mode in which the central unit executes the second task during which the stopping or starting of the heat engine is decided;

- the decision to stop or start the internal combustion engine is taken in particular as a function of the battery charge level;

- the engine start is decided or confirmed when the battery charge level is below a low threshold level, and in that the engine stop is likely to be decided or confirmed when the battery charge level is above a high threshold level; - the decision to stop or start the thermal engine is taken in particular as a function of the instantaneous torque requested by the driver; - the decision to stop or start the heat engine is taken in particular as a function of the average torque requested by the driver during a predetermined time interval preceding the decision; - the starting of the internal combustion engine is decided - or confirmed when the instantaneous torque requested by the driver is above a high threshold level, and in that the stopping of the internal combustion engine is likely to be decided or to be confirmed when the instantaneous torque and the average torque requested by the driver are less than a low threshold level;

- the stopping of the engine is decided or confirmed when, at the same time, the level of charge of the battery is higher than a high threshold level and the instantaneous torque and the average torque requested by the driver are lower than a low threshold level;

- the decision to stop or start the heat engine is taken in particular as a function of the difference between the torque requested by the driver and the torque actually supplied by the power train;

- in operation of the operating mode selected by the driver, a set charge level for the battery is fixed;

- the drive train is a hybrid set in series in which the driving -wheels of the vehicle are driven exclusively by the electric motor which is supplied by electric current coming either from the battery or from a generator driven by the heat engine ; - the electrical power to be supplied to the battery is determined according to a difference between the actual and reference levels of the battery, taking account of limit values battery charge and discharge power;

- the starting of the internal combustion engine is determined as a function of the electric power to be supplied to the battery, of the electric power absorbed by the electric motor and as a function of a difference between the value of the torque requested by the driver and the value of the torque supplied by the electric motor;

- there is determined a desired level of the p ower provided by the generator function of the power ^"actual supplied by the generator, the actual prov power ie by the battery, and the power to be supplied to the battery, taking into counts the maximum power likely to be supplied by the generator;

- an electric power required is determined as a function of the engine torque requested by the driver, taking into account, at least when this torque is greater in absolute value than a minimum value, a performance of the electric motor ;

- a setpoint value of the torque supplied by the electric motor is determined as a function of the motor torque requested by the driver multiplied by, at least when the required electric power is greater in absolute value than a threshold value , the ratio of the electric power likely to be supplied to the electric motor divided by the electric power required, the electric power likely to be supplied to the electric motor taking into account the electric power required, the real power supplied by the generator, the power likely to be supplied by the battery, and the maximum power likely to be absorbed by the engine;

- the power train is a hybrid set in parallel in which the electric motor and the motor thermiq ue each drive either at least one and the same drive wheel or different drive wheels;

- the drive train operates in regeneration mode, the electric motor only delivers engine torque if the driver causes a sudden increase in the requested torque;

- when the power train is operating in regeneration mode, the heat engine is controlled to provide maximum torque; - when the powertrain operates in hybrid mode and the battery charge level has previously fallen below a low threshold level and has not yet exceeded a high threshold level, the thermal engine is controlled to provide a setpoint torque at least equal to an optimal torque corresponding to optimal efficiency conditions of the heat engine;

- when the power train operates in hybrid mode and the instantaneous torque requested by the driver has previously become greater than a high threshold level without having once again become less than a low threshold level at the same time as the average level is lower at the low threshold level, the thermal engine is controlled to supply a setpoint torque at least equal to a filtered value of the torque requested by the driver; and - if a filtered value of the torque requested by the driver is greater than the maximum torque of the heat engine, the electric motor is requested to supply, as far as possible, the quantity of missing torque.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - Figure 1 is a schematic view illustrating the architecture of a motor vehicle with hybrid motorization, of the parallel type;

- Figure 2-is a view similar to that of Fig ure 1 illustrating a hybrid vehicle of series type;

- Fig ures 3A to 3K are flowcharts illustrating a first strategy for managing a hybrid vehicle in accordance with the teachings of the invention, more particularly intended for a hybrid vehicle of the parallel type; and - FIGS. 4A to 4H illustrate a flowchart of a management strategy according to the invention, more particularly intended for a vehicle of the hybrid type in series.

In a vehicle with hybrid motorization in parallel, of the type illustrated in FIG. 1, a heat engine 10 and an electric motor 12 are both capable of driving the driving wheels of the vehicle directly.

The heat engine 1 0 is generally an internal combustion engine of the reciprocating piston or rotary piston type or else of the turbine type. It is supplied with energy in chemical form by a liquid or gaseous fuel of the hydrocarbon type.

The electric motor 12 is electrically connected to a storage battery 16 carried by the vehicle, optionally by means of an inverter converter 17. The two motors 10, 12 each drive an input shaft 18 in rotation, 20 of a power distribution member 22, the output shaft or shafts 24 of which drive the drive wheels in rotation. The power distribution member 22 may comprise for example a gearbox, a differential and one can choose to interpose between at least one of the motors and the corresponding input shaft 1 8, 20, a device for clutch 25 which makes it possible to couple or uncoupled to will the engine relative to the power distribution member 22.

The vehicle thus equipped can therefore be driven either with the aid of a single thermal engine 1 0, or with the aid of only the electric motor 12, or with the aid of the two motors simultaneously. Optionally, the heat engine can have its power distributed between on the one hand the drive of the drive wheels 14, and on the other hand the drive in rotation of the “inverted” electric motor which then turns into an electric generator capable of recharging. the storage battery 16.

Similarly, the electric motor 12 can optionally be used to start the thermal motor 1 0.

In the hybrid vehicle of the series type q which is illustrated in FIG. 2, only the electric motor 12 is connected directly to the drive wheels, possibly by means of a power distribution member (not shown). The electric motor 12 can be supplied with electric energy by the storage battery 16 or by an electric generator 26 which is driven by the electric motor 12.

In all cases, it is possible to provide inverter converters 17 and rectifier 19 if the electric motor is to be supplied with alternating current.

Preferably, to ensure the management of the vehicle drive, each of the main elements of the vehicle is provided with a local control unit, each of these local units being in turn controlled by a central management unit which makes it possible to centralize at the same time information concerning the state of each of the organs, information as for the state of the vehicle and also information as for the wishes of the driver.

The central management unit aims in particular to control the two motors 1 0, 12 so as to make the best use of the energy of the vehicle which is stored either in the electric form in the batteries, or in the form of fuel of the hydrocarbon type. The aim of this management is also to respond at all times as satisfactorily as possible to the wishes of the driver regarding the acceleration and deceleration of the vehicle, this wish being preferably represented by a driving torque C requested at the level of the wheels. driving. Two main tasks are executed cyclically by the central management unit, namely on the one hand the decision to start or stop the internal combustion engine 1 0 and, on the other hand, the determination of the torque setpoints or of power which must supply the electric motor and the internal combustion engine to ensure the drive of the vehicle in accordance with the wishes of the driver.

According to the invention, these two tasks are performed in parallel and they are executed at different frequencies. Thus, the task of determining the torque setpoints to be supplied by the electric motor and the heat engine will for example be executed every forty milliseconds while the task of deciding whether to start or stop the heat engine will be by example performed every second. By decoupling the .sort these two tasks, we manage to obtain a management of the power supplied by the power unit consisting of the two motors 1 0, 12 which allows to respond almost instantaneously to the stresses of the driver. In addition, by making the decision to start and stop the internal combustion engine independent of instantaneous power management, this avoids multiplying these stop and start phases which are both sources accentuated pollution and sources of instability q uant to the total power supplied by the engines q ui can result in jolts felt by the driver and passengers of the vehicle.

The strategy for managing the hybrid vehicle according to the invention will be more particularly described below according to two embodiments, one of which is more particularly suited to a hybrid vehicle of the parallel type illustrated in FIG. 1, and the another is more particularly suitable for a hybrid vehicle of the series type illustrated in FIG. 2.

The first of these two strategies uses a series of variables which are grouped and explained in the table below

In FIG. 3A, the two main tasks which are executed in parallel with each other, at different frequencies, have been illustrated. Of course, the frequencies of 1 hertz and 25 hertz given here for on the one hand the task 1 1 00 of decision to start and stop the thermal engine, and on the other hand the task 1200 determination of torque settings of the motors 1 0, 12 are nonlimiting examples which illustrate the choice according to which the second of these frequencies is much higher than the first.

Each of the tasks 1100 and 1200 illustrated on these figures is broken down into lower level tasks which will be explained with reference to FIGS. 3B to 3K. The step 1100 for starting or stopping the heat engine is explained in FIG. 3B. First of all, in steps 1 101 and 1 102, two filtered values of the requested torque C requested by the driver are calculated. The filters used are for example first order filters, of the low pass type. The first value Cdemandé_filtre1 corresponds to an average of Cdemandé over a very short interval preceding the instant of the calculation and remains representative of the instantaneous value C requested. On the contrary, the value Cdemandé_filtre2 corresponds to a clipped average value of Cdemandé and it is therefore representative of a medium-term trend - of the torque demand formulated by the driver.

Once these two values have been calculated, three lower level tasks are executed during which intermediate boolean variables th_roulage (task 1110), th_recovery (task 1120), th_regeneration, electrical_request and thermal_request (task 1130) are determined.

These lower level tasks will be explained later.

Once these values have been determined, a test is carried out in step 1103 to check whether the heat engine 10 is available, that is to say if it is in a condition to deliver engine torque. If so, the Boolean variables which have just been calculated are kept such that, otherwise, as can be seen in step 1104, the Boolean values th_roulage, th_régénération and th_récupération are forced to zero.

The task 1110 for determining the value of the boolean variable th_roulage is now described with reference to FIG. 3C. In step 1111, it is first of all calculated two levels of threshold Cbas and Chaut to which the filtered values of the requested torque will be compared. These threshold values are notably determined as a function of the state of charge of the battery_ gauge 16.

In step 1112, it is first checked whether the filtered value Cdemandé_filtre1, representative of the instantaneous torque requested by the driver, is greater than the upper threshold level Chaut. If so, a boolean variable intermediate hyst_mode_couple is forced to the “hybrid” value in step 1 1 1 3. If not, in step 1 1 14, it is checked whether the two filtered values of the requested torque Cdemandé_filtre1 and Cdemandé_filtre2 are simultaneously lower than the lower level couple Cbas. In the affirmative, the boolean value hyst_mode_couple is forced in step 1 1 1 5 to the value "electric". If not, the boolean variable hyst_mode_couple is not changed.

In step 1 1 16, it is then checked whether the boolean variable hyst_mode_couple is equal to the value "hybrid". If so, the boolean value th_roulage is forced to 1 in step 1 1 1 8. If not, the boolean value th_rou iage is forced to zero in step 1 1 17.

The task 1120 for determining the value of the boolean variable th_recovery will now be described with reference to FIG. 3D. In step 1121, it is first checked whether the state of charge of the battery 16, represented by the variable gauge_battery, is less than a lower threshold level thresholdjauge_bas. In the affirmative, a boolean variable hyst_mode_batterie is forced to the value “hybrid” in step 1 122. In the negative, it is checked in step 1 123 if the value gauge_battery is greater than a higher threshold level thresholdjauge_haut. If so, the boolean variable hyst_mode_batterie is forced to the value “electric” in step 1 124. If not, the variable hyst_mode_batterie retains the same value as during the previous execution of the task.

In step 1125, it is checked whether the variable hyst_mode_batterie is equal to the value "hybrid". If yes, the value th_recovery is forced to the value 1 in step 1 127. If not, this variable is forced to the value zero in step 1 126. Task 1 1 30 is described with reference to Figure 3E. The aim of this task is to determine the value of the boolean variables th_regeneration, electric_request ^" and thermal_request. According to one aspect of the invention, the strategy of managing the powertrain of the hybrid vehicle which is proposed here allows the driver to select one of three operating modes of the power train.

In an electric mode, the driver prohibits the use of a heat engine. The boolean variables hyst_mode_couple and hyst_mode_batterie are forced to the variable “electrical”, the variable demand_electric is forced to the value “true”, the variable demand_thermiq ue -is forced to the value “false” and the variable th_regeneration is forced to the value "0".

The driver can also select an operating mode in regeneration of the power train. This operating mode requires the powertrain to start the internal combustion engine to ensure, in addition to driving the vehicle, recharging the battery 16. The boolean variables hyst_mode_couple and hyst_mode_batterie are in this case forced to the value "Hybrid". The boolean variables electrical_request and thermal_request are forced to the value “true” while the variable th_regenerate is forced to the value “1”.

The driver can also select a hybrid operating mode of the power train. In this operating mode, the heat engine 10 will only be used when necessary, as will be seen later. In this mode, the demand_electric variable is forced to the value "true". The demand_thermiq ue variable is forced to the value “true” if one or other of the variables hyst_mode_batterie and hyst_mode_couple are equal to the value "hybrid". Otherwise, the demand_thermiq ue variable is forced to the value "false". The variable th_regeneration is forced to the value "0". The second main task 1200 of this first strategy for managing a hybrid vehicle will now be described, with reference to FIGS. 3F to 3K, this second task being executed at a frequency fast enough to be able to satisfy the driver's request. This second task 1200, which consists in determining the set point couples Ce_ref and Ct_ref of the electric motor and of the heat engine, itself comprises two lower level tasks r 121 0 and 1220 which will be explained respectively in FIGS 3G at 3H and 31 at 3K. As can be seen in Figure 3G, the purpose of task 121 0 is to determine limit motor torques for the electric motor and the internal combustion engine. In step 121 1, it is first checked whether the heat engine is available. In the affirmative, variables of limiting torque Ctmax and Ctmin of the thermal engine are respectively assigned the values Cth_traction_max and Cth_freinage_max which are linked in particular to the speed and the temperature of the engine used. If not, the values of Ctmax and Ctmin are forced to zero in step 1213. In step 1214, it is then checked whether the electric motor is available. If not, the variables Cemax and Cemin are forced to zero in step 1217.

In the affirmative, the variable Cemin is assigned to step 121 5 the larger of two values among: - a value Cel_freinage_max, which depends in particular on the supply voltage and the temperature of the motor; - PbatmaxR X -.

NOT

The value of the maximum torque of the electric motor is determined in task 1216 which is broken down in fig ure 3H. Indeed, it is first of all tested in step 1216a if the variable th_regeneration is equal to 1, that is to say if the driver has selected the operating mode in regeneration of the power unit. If so, we can see that the value of Cemax is forced to zero in step 1216c, unless the driver, as verified in step 1216b, performs a kickdown maneuver by which it increases significantly and quickly the requested torque. This maneuver generally corresponds to a rapid depressing of the accelerator pedal.

In this case, or in the event of a negative response to the test of step 1216a, the value Cemax is fixed in step 1216d to the smallest of the values:

- PbatmaxD x -

NOT

- Cel_traction_max.

The task 1220 for calculating the torque setpoints Ce_ref and Ct_ref illustrated in FIG. 31 comprises two sub-tasks 1221 and 1222 which will be described respectively with reference to FIGS. 3J and 3 K. The sub-task 1221 consists in calculating a intermediate value Ct_ref_int. For this, it is first determined, in step 1221 a, a value Ct_ref1 which is equal to the largest of three values:

- th_roulage x Cdemandé

- th_regeneration x Ct_maximum

- th_recovery x Ct_optimal.

In step 1221 c, this variable Ct_ref1 is filtered by a low-order first order filter to give the intermediate variable Ct ref int. Step 1222 of adjusting Ce_ref and Ct_ref will now be described with reference to FIG. 3K. In step 1222a, the value of Ct_ref is first of all fixed at the value Ct_ref_int determined above. Then, in step 1222b, it is checked whether this value is greater than the value Ctmax. If so, in step 1222c, Ct_ref is forced to the value Ctmax and Rt_sup is forced to the value zero. If not, in step 1222d, the value of Rt_sup is fixed at the difference of Ctmax-Ct_ref. In the two response cases at step 1222b, it is then checked at step 1222e if the value of Ct_ref is less than the value of Ctmin. If so, in step 1222f, Ct_ref is forced to the value r Ctmin and Rt_inf is forced to zero. If not, Rt_inf is set equal to the difference between Ct_ref and Ctmin in step 1222g.

In the two response cases at step 1222e, Ct_ref is then forced to the value Cdem-Ct_ref, Re_sup is forced to the value Cemax-Ce_ref and the variable Re_inf is forced to the value Ce_ref-Cemin at step 1222h. Then in step 1 222i, i l is checked if the value of

Re_sup is negative. If not, the process 1222o is carried out directly. If so, in step 1222j, the variable D_sup is fixed at the value Rt_sup + Re_sup, the variable Ce_ref is fixed at the value Cemax, the value Re_sup is fixed at zero and the variable Re_inf is fixed at the value of the difference between Cemax and Cemin. Then, in step 1222k, it is checked whether the value D_sup is negative. If it is, in step 12221, the variable Ct_ref is fixed at the value Ct_max and the variable Rt_sup is fixed at zero; otherwise, in step 1222m, the variable Ct_ref is fixed at the value Ctmax-D_sup and the variable Rt_sup is fixed at the value D_sup.

In both cases of response at step 1222k, so that in the case of a negative response to the test of step 1222i, it is then verified in step 1222o if the variable Re_inf is negative. If so, at step 1222p. the variable D_inf is fixed _r at the value Rt_inf + Re_inf, the variable Ce_ref is fixed equal to the value Cemin, the variable Re_sup is fixed equal to the difference of Cemax minus Cemin and the variable Re_inf is fixed at the value zero.

Then, in step 1222q, it is checked whether the variable D_inf is negative. If so, in step 1222s, the variable Ct_ref is fixed equal to the value r Ctmin and the variable Rt_inf is fixed to the value n ulle. If not, the variable Ct__ref is fixed equal to the value Ctmin + D_inf and the variable Rt_inf is fixed equal to the value D_inf.

If not, it is done directly at the end of the task.

As can be seen from the detailed description of this first hybrid vehicle management strategy, when the driver has selected the hybrid operating mode for the powertrain, the engine is started during task 1 1 30, if one of the variables hyst_mode_batterie and hyst_mode_couple is equal to the value "hybrid". If neither is at the hybrid value, the engine is stopped. Thus, it can be deduced from step 121 3 that the heat engine can start if the driver requests a torque requested from the wheel sufficiently high that the variable Cdemandé_filtre 1 is greater than the high threshold Chaut. Likewise, it can be deduced from steps 1,122 and 1,121 that the thermal engine is started when the battery charge level becomes lower than a lower threshold level. However, with this first strategy, stopping the the heat engine is only caused when both the conditions of step 1114 and of step 1123 are satisfied, that is to say when the battery reaches a state of charge greater than one. _. upper threshold level and when, at the same time, the instantaneous and average filtered values of the torque requested by the driver are less than a low threshold level.

Thus, according to this strategy, it can be seen that the decision to start the heat engine depends in particular on the level of charge of the battery, the instantaneous torque requested by the driver, and the average torque requested by the driver.

It can also be seen that, when the power train operates in hybrid mode, the value of the torque Ct_ref which will be requested from the heat engine depends on the variables th_roulage and th_récupération determined by tasks 1110 and 1120. Thus, when the charge level of the battery has previously become below a low threshold level and it has not yet exceeded a high threshold level, it appears from task 1120 that the value of th_recovery is equal to 1 so that the calculated intermediate value Ct_ref1 in step 1221b cannot be less than the torque Ct_optimal that the motor provides when it is controlled under optimal performance conditions. The value Ct_ref of the setpoint torque imposed on the heat engine cannot therefore fall below a level corresponding to this optimal torque.

On the contrary, still when the driver has selected the hybrid operating mode of the powertrain, it appears from task 1110 that, when the condition of step 1112 has been fulfilled and as long as that of step 1114 has not not been, the value of the variable th_roulage is equal to 1 so that, under these conditions, the value of Ct_ref1 calculated in step 1221b cannot be less than the torque requested by the driver.

Furthermore, it appears from task 1222 that if the filtered value Ct_ref_ nt of the torque requested by the driver exceeds the threshold Ctmax of the torque likely to be supplied by the heat engine, the electric motor is requested in step 1222h to supply the missing torque, within the limits of the possibilities of the electric motor and the battery.

There will now be described more particularly with reference to FIGS. 4A to 4H a second strategy for managing a hybrid vehicle according to the invention intended more particularly to be applied in the context of a hybrid vehicle of the series type. This second strategy calls on a series of variables which are grouped and explained in the table below.

As can be seen in FIG. 4A, the central management unit of the powertrain is responsible for the execution of three main tasks. The first 21 00 of these tasks here consists in determining the torque setting of the electric motor. It is executed for example every forty milliseconds, that is to say at a frequency of 25 hertz. In parallel, the second task 2200 is executed, which consists of the decision to start or stop the heat engine. Its period is one second and its frequency is 1 hertz.

I t is also provided a third main task 2300, also executed in parallel, and during which the power setpoint of the electric generator Pge_ref is determined. Its execution period is for example 500 milliseconds, corresponding to a frequency of 2 hertz to take account of the inertia of the assembly formed by the internal combustion engine and the generator.

The first of these main tasks is described with reference to Figure 4B. As can be seen in this figure, the task 2100 for determining the torque setpoint of the electric motor Ce_ref begins with the execution of the sub-task 21 1 0 for calculating the required electric power Pel_demandé.

This subtask is described with reference to Fig ure 4C. First of all, in step 21 1 1, the Pel value of the power absorbed by the electric motor is determined. This power is positive when the engine drives the vehicle and it is negative when, during a vehicle slowing down, the electric motor is used as a generator to recharge the battery 16. This Pel value is equal to the voltage of the electrical supply network multiplied by the sum of the currents supplied by the battery on the one hand and by the electric generator on the other.

In step 21 12, the mechanical power supplied by the electric motor Pmec is defined as being the product of the setpoint torque Ce_ref by the speed of rotation N of the electric motor 12. In step 21 1 3, the requested mechanical power Pmec_demandé is defined as being equal to the torque Cdemandé by the driver multiplied by the speed N of rotation of the electric motor. In step 21 14, it is determined whether the absolute value of the mechanical power Pmec is greater than a threshold value Pmini. If so, a step 21 1 5 defines an efficiency of the electric motor which is equal to the absolute value of the ratio of the electric power Pel divided by the mechanical power Pmec. If not, the value of this yield is arbitrarily set to 1 in step 21 16.

In step 21 17, a filtered value R_filter of this efficiency is determined, for example using a first order filter. In step 21 18, the. requested electrical power

Pel_demandé is determined as being the product of the filtered value of efficiency by the mechanical power required.

The execution of task 21 00 for determining the torque setting of the electric motor then continues at step 21 01 during which it is checked whether the absolute value of the electric power requested is greater than a threshold level Pmini. If not, the setpoint torque Ce_ref is set equal to the torque requested by the driver. If so, it is first determined the power Pge provided by the generator. If it delivers a current Ige, this power is worth U times Ige.

In step 2103, the traction power which the battery 16 must supply is calculated. This value Pbat_demandé is equal to the electric power necessary to supply the requested torque minus the power supplied by the generator. In step 2104, the power capable of being supplied by the battery is determined as being the minimum value between the following two values:

- the maximum battery discharge power (PbatmaxD) and - the minimum value between

^* the power requested from the battery (Pbat_demandé);

^* the maximum battery recharge power (PbatmaxR). In step 21 05, it is then determined the electric power which the system can be supplied with, this value being the smaller of the following two values: the maximum power of the thermal engine

Pmoteur_max; and - the sum of the power likely to be supplied by the battery (Pbat_possible) with the power supplied by the generator Pge.

Then in step 2106, the reference torque Ce_ref is determined as being the product of the torque requested by the driver by the ratio of the electric power that the system can provide divided by the requested electric power. The second main task 2200 of this second strategy for managing a hybrid vehicle consists in the decision to start or stop the thermal engine. As can be seen in the. FIG. 4C, this task 2200 begins with the execution of task 231 0 for calculating the recharging power of the battery which is illustrated in FIG. 4G. As can be seen in this figure, it is therefore determined, in steps 2312, 231 3, 2314, a reference state of charge Soc_ref according to the operating mode selected by the driver of the vehicle. In step 231 5, a difference value is determined between this reference state of charge Soc_ref and the real state of charge. In step 231 6, the requested battery power is defined as being a filtered value of this difference, for example by a first order filter. However, in step 231 7, it is verified that this calculated value of the battery recharging power does not exceed the limit powers of charge and discharge of the battery, in which case the recharging power of the battery battery is forced to one of these limit values. The task of deciding whether to start or stop the thermal engine can then be carried out in step 2201 in which the electrical power Pel is determined in the same way as seen above in step 21 1 1. This electrical power is filtered by a first order filter to obtain in step 2202 the variable Pel_filtreB.

A calculation is then made of the difference between the torque requested by the driver and the torque actually applied to the drive wheels by the electric motor. This calculation of the value deviation_provision is the subject of task 221 0 illustrated in FIG. 4E in which it can be seen that this value is obtained by filtering through a first order filter the difference between the torque requested by the Cdemandé driver and the torque provided by the Ce_ref electric motor.

The task of deciding whether to start or stop the heat engine is continued in step 2203 by determining the value of the power requested from the electric generator Pge_demB. This value is equal to a weighted sum of the previously calculated values Pbat_demandé, Pel_filtreB and Ecart_prestation. In step 2204, it is checked if this value Pge_demB is greater than a threshold value Pge_mini and if, at the same time, the operating mode selected by the driver is different from the electric motor. If this double condition is verified, then the Boolean variable GE_requested is forced to the value "true" and the heat engine is then started to supply electric current. On the contrary, if the double condition of step 2204 is not fulfilled, the variable G E_requested is forced to the value "false" in step 2206 so that the heat engine is commanded to stop.

When the thermal engine is started, it is then possible to control it so that it drives the electric generator so that it produces sufficient power. To this end, a task setpoint for the power of the electric generator Pge_ref is calculated at task 2300. This task illustrated in Fig ure 4F, begins with the execution of the task of the lower level 231 _^ 0 q ui has been described above and which consists of the calcu of the charging power of the battery. Then, in step 2301, the electric power Pel absorbed by the electric motor is calculated in the same way as was seen in steps 2201 and 21 1 1. This value is then filtered in step 2302, for example by a first order filter, to give an intermediate value Pel_filtreA. In step 2303, it is determined the weighted sum Pge_demA of the recharge power of the battery Pbat_demandé with the value Pel_filtreA calculated in step 2302. In step 2304, the power of cp.signe of the electric generator Pge_ref is defined as being the smallest the value Pge_demA, calculated in step 2303, and the maximum power likely to be supplied by the generator Pge_max.

As can be seen from steps 2203, 2204, 2205 and 2206, the decision to start a thermal engine depends in particular on the following three parameters:

- the state of charge of the battery, because the value Pbat_demandé is calculated in particular as a function of the difference between the actual state of charge of the battery and a reference state of charge (see steps 231 5, 2316, 2317) ; - the engine torque requested, because the value

Ecart_prestation depends of course on this requested couple (see steps 221 1 and 2212); and

- the difference between the service provided by the system and that requested by the driver.

Claims

RESELL I CATION S

1. Motor vehicle with hybrid motorization, of the type in which a power unit comprises an electric motor (12) and a heat engine (10) which are capable of contributing to the driving of the vehicle, and of the type in which a central management unit performs a first task (1200, 2100) comprising the determination of the torque that q ue must supply each engine so that the power train provides the vehicle with an engine torque in accordance with a torque requested (Cdemanded) by the driver of the vehicle, and type in which the internal combustion engine (1 0) is capable of being stopped, the vehicle then being driven by the only electric motor (12) supplied with electric current by a storage battery (16), characterized in that , at least for certain operating modes (hybrid) of the power train, the central unit performs a second task (1100, 2200) during which the stop is decided o u starting the internal combustion engine, in that the first task and the second task are executed in parallel and in that the execution frequency of the second task is lower than that of the first task.

2. Motor vehicle according to claim 1, characterized in that the driver can impose on the power unit an electric operating mode in which the heat engine (10) is stopped.

3. Motor vehicle according to one of the preceding claims, characterized in that the driver can impose on the powertrain a regenerative operating mode in which the heat engine (1 0) is used in particular to ensure the recharging the battery (16).

4. Motor vehicle according to any one of the preceding claims, characterized in that the driver can impose on the powertrain a hybrid operating mode in which the central unit performs the second task during which the stop is decided or starting the engine.

5. Motor vehicle according to claim 4, characterized in that the decision to stop or start the heat engine (10) is taken in particular according to a charge level (gauge_battery, ploughshare) of the battery (16).

6. Motor vehicle according to claim 5, characterized in that the starting of the heat engine (10) is decided or confirmed when the charge level (gauge_battery) of the battery (16) is below a low threshold level (thresholdjauge_bas) , and in that the stopping of the heat engine (10) is likely to be decided or to be confirmed when the level of charge of the battery is higher than a high threshold level (threshold_gauge_ low).

7. Motor vehicle according to any one of claims 4 to 6, characterized in that the decision to stop or start the heat engine (10) is taken in particular as a function of the instantaneous torque

(Cdemandé_filtre1) requested by the driver.

8. Motor vehicle according to any one of claims 4 to 7, characterized in that the decision to stop or start the heat engine (10) is taken in particular according to the average torque (Cdemandé_filtre2) requested by the driver during a predetermined time interval preceding the decision.

9. Motor vehicle according to claim 7 taken in combination with claim 8, characterized in that the starting the thermal engine (10) is decided or confirmed when the instantaneous torque (Cdemandé_filtre1) requested by the driver is above a high threshold level (Chaut), and in that the stopping of the thermal engine (10) is likely to be decided or confirmed when the instantaneous torque (Cdemandé_filtre 1) and the average torque (Cdemandé_fi! tre2) requested by the driver are below a low threshold level (Cbas).

1 0. Motor vehicle according to claim 6 taken in combination with claim 9, characterized in that the stopping of the heat engine (1 0) is decided or confirmed when both the load level ( battery gauge (1 6) is greater than a high threshold level (threshold gauge_high) and the instantaneous torque (Cdemandé_filtre 1) and the average torque (Cdemandé_filtre2) requested by the driver are lower than a low threshold level (Cbas ).

1 1. Motor vehicle according to any one of Claims 4 to 1 0, characterized in that the decision to stop or start the internal combustion engine (1 0) is taken in particular as a function of a difference (difference) between the requested torque (Cdemandé) by the driver and the torque actually supplied by the power train.

12. Motor vehicle according to any one of the preceding claims taken in combination with at least one of claims 2 to 4, characterized in that, in operation of the operating mode selected by the driver, a set level is fixed charging (soc_ref) of the battery (16).

1 3. Motor vehicle according to one of the preceding claims, characterized in that the drive train is a series hybrid assembly in which the drive wheels of the vehicle are driven exclusively by the electric motor (12) which is supplied with electric current from the battery (16) which is recharged by a generator (26) driven by the heat engine (10).

14. Motor vehicle according to claim 13 taken in combination with claim 12, characterized in that the electrical power (Pbat_demandé) to be supplied to the battery (16) is determined as a function of a difference (Ecart_soc) between the levels actual (soc) and reference (soc_ref) of battery charge, taking into account limit values of battery charge (PbatmaxR) and discharge (PbatmaxD) power (16).

15. Motor vehicle according to claim 14, characterized in that the starting of the heat engine (10) is determined as a function of the electric power (Pbat_demandé) to be supplied to the battery (16), of the absorbed electric power (Pel_filtreB) by the electric motor (12) and as a function of a difference (Deviation_prestation) between the value of the torque requested by the driver and the value of the torque supplied by the electric motor (12).

16. Motor vehicle according to claim 14 or

15, characterized in that a set level (Pge_ref) of the power supplied by the generator (26) is determined as a function of the real power (U ^* lge) supplied by the generator (26), of the real power (U ^* lbat) supplied by the battery (16), and the power (Pbat_demandé) to be supplied to the battery (16), taking into account the maximum power (Pge_max) likely to be supplied by the generator (26).

17. Motor vehicle according to any one of the preceding claims 13 to 15, characterized in that a necessary electrical power (Pel_demandé) is determined as a function of the engine torque (Cdemandé) requested by the driver, taking into account, at least when this couple is greater in absolute value than a minimum value, of an efficiency of the electric motor (R).

1 8. Motor vehicle according to claim 16, characterized in .ce that a set value (Cref) of the torque supplied by the electric motor (12) is determined as a function of the engine torque requested by the driver multiplied by, at least when the required electric power (Pe! _requested) is greater in absolute value than a threshold value (Pmini), of the ratio of the electric power (Pel_possible) likely to be supplied to the electric motor (12) d divided by the necessary electric power (Pel_possible), the electric power (Pel_possible) likely to be supplied to the electric motor (12) taking into account the necessary electric power (Pel_demandé), of the real power (Pge) provided by the generator, the power (Pbat_possible) capable of being supplied by the battery (16), and the maximum power (Pmoteur_max) capable of being absorbed by the engine.

1 9. Motor vehicle according to one of the claims 1 to 12, characterized in that the power unit is a hybrid unit in parallel in which the electric motor (12) and the heat engine (1 0) drive each is at least one and the same drive wheel or different drive wheels.

20. Motor vehicle according to claim 19 taken in combination with claim 3, characterized in that when the drive train operates in regeneration mode, the electric motor (10) delivers engine torque only if the driver causes an increase brutal of the requested couple (kickdown).

21. Motor vehicle according to one of claims 19 or 20 taken in combination with claim 3, characterized in that when the power train operates in regeneration mode, the heat engine (1 0) is controlled to provide maximum torque (Ct_maximum).

22. Motor vehicle according to any one of claims 1 9 to 21 taken in combination with claim 4, characterized in that when the power train operates in hybrid mode and q ue the charge level (gauge_battery) of the battery (1 6) has previously fallen below a low threshold level (thresholdjauge_bas) and has not yet exceeded a high threshold level (thresholdjauge_haut), the heat engine (1 0) is controlled to provide a setpoint torque (Ct_ref1 ) at least equal to an optimal torque (Ct_optimal) corresponding to optimal efficiency conditions of the thermal engine.

23. Motor vehicle according to any one of the preceding claims 1 9 to 22 taken in combination with claim 4, characterized in that when the power train operates in hybrid mode and q ue the instantaneous torque (Cdemandé_filtre 1) requested by the conductor has previously become above a high threshold level (Chaut) without having once again become below a low threshold level (Cbas) at the same time as the average level (Cdemandé_filtre2) is below the low threshold level (Cbas), the the heat engine (1 0) is controlled to supply a setpoint torque at least equal to a filtered value of the torque requested by the driver.

24 Motor vehicle according to any one of the preceding claims 19 to 23, characterized in that, if a filtered value (Ct_ref_int) of the torque requested by the driver is greater than the maximum torque (Ct_max) of the heat engine (1 0), the electric motor (12) is used to supply, as far as possible, the quantity of missing torque (Cdem - Ctref).