FR2976418A1 - METHOD FOR ENSURING THE RECHARGING OF AN ELECTRIC ENERGY ACCUMULATOR FOR A HYBRID VEHICLE, IN PARTICULAR ELECTRIC BATTERIES - Google Patents

Abstract

The present invention relates to a method for recharging an electric energy accumulator, in particular an electric battery (26), for a hybrid motor vehicle comprising a heat engine (10), in particular an internal combustion engine, and an electric machine ( 22) connected to said energy accumulator and capable of providing assistance to the engine for acceleration of said vehicle. According to the invention, the method consists in: - establishing a graph with a curve (C) of the state of electric charge (SOC) of said accumulator as a function of the speed (V) of the vehicle by delimiting a zone (A) where the electrical energy of the accumulator is sufficient to provide said assistance and a zone (B) where this energy is insufficient, - when the discharge of the accumulator is such that the value of the state of charge reaches the curve (C ), to recharge said accumulator by the electric machine during deceleration phase of the vehicle.

Description

The present invention relates to a method for recharging an electric energy accumulator for hybrid vehicles, in particular electric batteries.

It relates more particularly, but not exclusively, to plug-in hybrid vehicles of the rechargeable type (or hybrid plug-in vehicle) whose energy accumulator, generally one or more electric batteries, can be recharged by connection to a power source, as on the conventional electricity grid.

As already known, a hybrid-propulsion vehicle comprises a powertrain which uses, as traction / propulsion drive mode, a combustion engine, in particular an internal combustion engine with a speed variation device, and a rotary electric machine. powered by an electrical source, such as one or more batteries. Thus, when it is desired to move the vehicle with a large torque over a wide range of speeds while limiting the generation of exhaust gas and noise, as in an urban site, the use of the electric machine is preferred for drive this vehicle on the move.

On the other hand, the heat engine is used, alone or in association with the electric machine, to move this vehicle during a use requiring a high power and / or a great autonomy of operation.

This has the advantage of optimizing the performance of this vehicle, including reducing emissions of pollutants into the atmosphere and reducing fuel consumption.

In the case of using the heat engine alone, the power it generates is almost always available.

On the other hand, the power of the electric machine, which will be used in combination with the heat engine, depends on the level of energy contained in the batteries.

In one of the operating configurations of the powertrain, which is better known as "electric boost" (or electrical assistance), the power generated by the electric machine makes it possible to provide assistance to the power of the heat engine for thus driving the vehicle with high power. This electric assistance is more particularly used during a request for strong acceleration of the vehicle, especially when a strong pressure on the accelerator pedal up to the position of the pedal said foot to the floor. However, during severe and prolonged use of this electrical assistance, the batteries that power the electric machine are discharged very quickly. These batteries are no longer able to provide the power necessary for the acceleration of the vehicle when their state of charge is below a certain threshold. As a result, the dynamic performance of the vehicle is then decreased.

Several solutions can then be considered to try to remedy this drawback. One of these solutions may be to allocate to the hybrid vehicle maximum performance corresponding to those developed solely by the heat engine and this regardless of the state of charge of the electric batteries. In this configuration, the total power developed at the wheel by the heat engine associated with the electric machine does not exceed that which would be provided by the heat engine alone and this even when the batteries are capable of providing power for driving the machine. vehicle. This solution has the disadvantage of not being able to act on the reduction of the power of the engine. This reduction can result in particular from the reduction of the cubic capacity, which is a vector of gain in consumption.

Another of these solutions may be to degrade the dynamic performance of the hybrid vehicle when the energy level stored in the batteries is too low to achieve the power assistance. This solution has the disadvantage of causing inconvenience in terms of driving comfort because the performance decreases even when the vehicle is asked to reach its maximum performance. The present invention proposes to overcome the above drawbacks with a method which makes it possible to ensure a minimum level of battery charge, even in the event of severe and prolonged driving of the hybrid vehicle, and while having the possibility of use a less powerful engine 15 therefore less fuel consuming.

To this end, the invention relates to a method for recharging an electric energy accumulator, in particular an electric battery, for a hybrid motor vehicle comprising a heat engine, in particular an internal combustion engine, and an electrical machine connected to said electric vehicle. energy accumulator and capable of providing assistance to the heat engine for the acceleration of said vehicle, characterized in that it consists in: - establishing a graph with a curve of the state of electric charge of said accumulator as a function of the speed of the vehicle by delimiting an area 25 where the electric energy of the accumulator is sufficient to provide said assistance and an area where this energy is insufficient, - when the discharge of the accumulator is such that the value of the state of charge reaches the curve, to recharge said accumulator by the electric machine during deceleration phase of the vehicle. The method may include recharging the accumulator with an amount of energy at least equal to the amount of energy expended during the preceding acceleration.

The method may include recharging said accumulator using the regenerative braking of the vehicle.

The method may include recharging said accumulator using the energy of the engine.

The other features and advantages of the invention will now appear on reading the following description, given solely by way of illustration and not limitation, and to which are appended: - Figure 1 which is a diagram showing an example configuration of the power train of a hybrid vehicle and FIG. 2 which illustrates a graph showing a curve representative of the state of charge of the batteries (SOC in%) as a function of the speed (V in km / h) of the vehicle. hybrid.

FIG. 1 illustrates a non-limiting example of a configuration of a hybrid vehicle powertrain.

This powertrain comprises an internal combustion engine 10 whose crankshaft 12 is connected to a speed variation device 14, such as a robotized gearbox. This box comprises an input shaft 16 which is connected to the crankshaft 12 through a controlled-control coupling 18, such as a clutch. This box also includes an output shaft 20 whose role will be explained later in the description. This group also comprises an electric machine 22 with a rotor 24 which is connected to electric energy accumulators 26, such as batteries, through electrical conductors 28.

This electric machine can function as an electric drive motor for the vehicle or as an electric power generator to recharge the batteries.

The output shaft 20 of the gearbox 14 and the rotor 24 of the electric machine 24 result in a motion transmission device 30 to a driving axle 32 carrying the wheels 34 of the vehicle, directly or via a differential bridge 36. This device 30 makes it possible to transmit to the axle 32 the rotational movement coming from the output shaft 20 and / or the rotor 24. Likewise, this device makes it possible to transmit the rotational movement of the wheels by the axle is towards the rotor (battery recharge) or towards the engine (engine brake). The powertrain also comprises a computing and processing unit 38 which receives, via communication lines 40, information from the various sensors and / or probes (not shown). This information then makes it possible to evaluate the various operating parameters of the vehicle, such as its speed or the electrical state of charge of the batteries.

Although extended, this unit can also control by bidirectional control lines (not shown) all the vehicle components necessary for its operation. These organs are in particular the power and control circuit of the electric machine 22. As already mentioned, in order to ensure the use of the electric machine as an electric motor to fulfill the electrical assistance function, it is therefore necessary to guarantee at all times a sufficient level of electrical energy in the batteries. This stored energy must be able to participate in the acceleration of the vehicle to the maximum speed required, and this with the maximum performance of the vehicle.

For this, the applicant has established, by calculation and simulation, a graph with a curve C (Figure 2) of the state of electric charge of the batteries (SOC: State Of Charge) according to the speed of the vehicle (V). This curve thus makes it possible to define two zones: a zone A where the electrical energy stored in the batteries is sufficient to provide electrical assistance and a zone B where this energy is insufficient.

This curve is thus integrated into tables of the computing and processing unit 38 so as to be associated with the operation of the vehicle.

Thus, when the state of charge of the batteries 26 is in the zone A, any request for acceleration to go from a speed VI to a speed V2 of the vehicle can be carried out by the heat engine 10 associated with the assistance. The electric charge generated by the electric motor 22. During this acceleration, which lasts for a determined period of time t, the state of charge of the batteries goes from a value XI to a terminal value X2 with X2 which is less than xi. This acceleration can be reproduced with the same level of electrical assistance as long as the value of the state of charge of the batteries is included in zone A, that is to say is greater than or equal to curve C. Below of this curve, the battery charge is no longer sufficient to perform the electric assist function with the same level of performance. The acceleration achieved will then be lower and the time t to achieve it will increase, which affects driving comfort.

In order to always be able to ensure a state of electric charge of the batteries sufficient for one (or more) acceleration (s), it is expected to spare the discharge of the batteries when the level of the charge of the battery is equal that of the curve C. Thus, during a moderate acceleration phase which can be achieved by the power generated by the only capacities of the heat engine, then only this heat engine will be used to drive the driving axle 32 and thus the wheels 34.

Advantageously, this motor will be used at a higher power level so that the electric machine serves as a generator and thus partially recharge the batteries.

In the event that the desired acceleration can not be obtained by the only power source that is the engine, and if the state of charge of the batteries is in zone A, then the engine is used to the maximum power it can supply on the one hand, and the electric machine is used, as electrical assistance, to provide the complement of power on the other hand. The calculation method used to determine curve C is such that, by the power distribution between the heat engine and the electric machine (provided that the state of charge of the batteries is in zone A before acceleration ), the state of charge of these batteries is advantageously in this zone A at the end of this acceleration.

Two cases can then occur after obtaining this acceleration.

In one case, the driver then requests a constant speed to the vehicle, which can be achieved by the engine alone. Depending on the power developed by the engine, you can recharge the batteries if necessary while keeping the vehicle speed constant.

In another case, the vehicle goes into the deceleration phase after the acceleration phase. In the latter case, the unit 38 will control the electric motor 22 to recharge the batteries with an energy at least equal to the energy expended during the preceding acceleration, in order to maintain a state of charge located in the area A. This can be achieved by using the energy from the driving axle 32 via the motion transmission device 30 to drive the electric motor 22 as an electric power generator for the batteries 26. This is known as recuperative braking. However, this amount of energy recovered by the regenerative braking may be insufficient to ensure that the state of charge of the batteries remains in zone A.

The use of an active refill made by the engine, however, provides the required level of energy. This consists, during the deceleration of the vehicle, in using the mechanical energy from the engine 10 via the gearbox 14, in addition to the energy from the driving axle 32. At the same time this additional energy supplied to the device 30 will be absorbed by the electric machine 26, through the rotor 24, so that the power absorbed to the driving axle 32 meets the demand of the driver. The power absorbed by the electric motor, then operating as a generator, is increased.

Considering that the vehicle is subjected in normal use to accelerations 20 bounded below, it is possible to calculate the recharging power required, during any deceleration of the speed V2 to the speed VI, so that the energy stored in the batteries during this deceleration is greater than or equal to the energy expended during the opposite acceleration. The setpoint of this recharging power will consist of a table dependent on the vehicle speed, and stored in the calculation unit 38.

In this way, the state of charge of the batteries is always located in the zone A described in FIG. 2 and the batteries thus contain at all times sufficient energy to achieve acceleration up to a determined speed of the vehicle and this without degrade the performance of this vehicle.

Depending on the performance of the electric motor and the batteries, and in particular the maximum permissible power for charging these batteries, the energy recharged during the deceleration will be limited. At high speed in particular, it will limit the power available to limit the energy spent during acceleration to the value of the energy recharged during deceleration.

In case of critical use of the vehicle, especially if the vehicle is subjected to a very strong deceleration that does not allow a sufficient recharge 10 and following a severe use of the vehicle which has led to a state of charge on the curve C, said state of charge varies very little while the speed of the vehicle decreases very quickly. In this case, the value of the state of charge (SOC) will cross the curve C and enter the zone B. In this case of infrequent use of the use of the vehicle, it will be necessary to reduce the performance of the vehicle. acceleration available.

Claims (4)

CLAIMS1) A method for recharging an electric energy accumulator, in particular electric batteries (26), for a hybrid motor vehicle comprising a heat engine (10), in particular an internal combustion engine, and a connected electrical machine (22) energy accumulator audit and capable of providing assistance to the heat engine for the acceleration of said vehicle, characterized in that it consists in: - establishing a graph with a curve (C) of the state of electric charge (SOC ) of said accumulator according to the speed (V) of the vehicle by delimiting a zone (A) where the electric energy of the accumulator is sufficient to provide said assistance and a zone (B) where this energy is insufficient, - when the discharge of the accumulator is such that the value of the state of charge reaches the curve (C), to recharge said accumulator by the electric machine during deceleration phase of the vehicle. 2) A method for recharging an electric energy accumulator according to claim 1, characterized in that it consists in recharging the accumulator with a quantity of energy at least equal to the amount of energy expended during the previous acceleration. 3) A method for recharging an electric energy accumulator according to one of the preceding claims, characterized in that it consists in recharging said accumulator using the regenerative braking of the vehicle. 4) A method for recharging an electric energy accumulator according to one of the preceding claims, characterized in that it consists in recharging said accumulator using the energy of the engine.