WO2008125766A2

WO2008125766A2 - Method and device for recharging the electric energy storage of a vehicle

Info

Publication number: WO2008125766A2
Application number: PCT/FR2008/050362
Authority: WO
Inventors: Stéphane Beddok
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2007-03-13
Filing date: 2008-03-04
Publication date: 2008-10-23
Also published as: WO2008125766A3; FR2913825A1; FR2913825B1

Abstract

The invention relates to a method and a device for recharging the electric energy storage (21) of a vehicle including a battery (22). According to the invention, the method comprises dividing said storage (21) into at least two electric energy storage modules (25-26), serially connecting said modules during the use thereof for supplying electric energy, and connecting in parallel said modules for recharging said storage using the battery.

Description

Method and device for recharging an electrical energy store of a vehicle

The present invention claims the priority of the French application 0753774 filed on 13/03/2007 whose content (description, claims and drawings) is incorporated herein by reference.

The present invention relates to a method and a device for charging an electrical energy store of a vehicle.

[0003] Motor vehicles are increasingly equipped with an additional source of electrical energy, for the storage of electricity, in addition to the conventional 12-volt battery that powers the vehicle's on-board system. This storer of electrical energy makes it possible to perform certain functions such as electric traction for hybrid vehicles, the automatic stopping and restarting of the engine when the vehicle is stationary, the recovery of electrical energy during braking phases. and traction assistance. Some of these functions require the use of a reversible alternator capable of supplying mechanical energy.

[0004] Figure 1 shows a conventional architecture with two sources of electrical energy. An electrical energy storage device 10 is connected, in series with a DC / DC converter 1 1, to a 12-volt battery 12 which supplies devices connected to the on-board vehicle network (for example headlights or windscreen wipers). , the connection to the devices being symbolized by the arrow 13. The storer 10 may be for example a supercapacitor. This type of capacitor makes it possible to store a large amount of energy and to restore it faster than with a battery. One 14 of the two terminals of the battery 12 is connected to the earth, the other terminal 15 being connected to the converter 1 1. The terminal 16 of the storage unit 10 is connected to the ground, the other terminal 17 being connected to the converter 1 1 and an electric machine 18, for example a reversible alternator coupled to the crankshaft of the engine of the vehicle. When the latter is running, the alternator supplies electrical power to the storage unit 10 and the battery 12.

When the electric machine 18 is a reversible alternator, the architecture shown in FIG. 1 allows:

the restart of the thermal engine: the reversible alternator 18 transforms the electrical energy supplied by the electrical energy store 10 into mechanical energy. This mechanical energy can drive the engine to ensure a restart.

the supply of additional mechanical energy to the heat engine: the reversible alternator 18 transforms the electrical energy supplied by the storage unit 10 into mechanical energy. This mechanical energy thus supplied is added to that provided by the heat engine. The power transmitted to the wheels of the vehicle is therefore greater.

energy recovery during braking phases of the vehicle: the reversible alternator 18 transforms the mechanical energy supplied by the heat engine into electrical energy. This electrical energy is stored in the storage unit 10 or the 12V 12 battery.

- The vehicle's on-board power supply: the electrical energy is supplied to the on-board electrical system, when the engine is running, by the reversible alternator 18 and the DC / DC converter 1 1, and when the combustion engine is stopped (Stop phase) by the energy store 10 or the battery 12.

- The voltage at the terminals of the energy store 10 changes according to the energy it contains. Thus, this tension increases when the storer energy 10 is charged: the store is powered by another source of electrical energy (the battery 12 via the DC / DC converter or or the electric machine 18). The voltage at the terminals of the storer decreases when the energy store 10 is discharged because of the flow of current to an electrical consumer appliance (arrow 13) supplied by the electrical energy store 10 or because it is deliberately decided to unload the storer for reasons of safety or life of the components. This voltage also decreases because of the self-discharge of the energy store 10: even if the storer does not supply any electricity-consuming appliance (zero current flow), the phenomenon of self-discharge causes a drop in the voltage. at the terminals of the storer. Over a period of several days, this voltage can tend to 0 Volt (almost unloaded storage). The voltage at the terminals of the energy store can therefore be close to 0 volts.

On some applications, the correct operation of the vehicle requires a voltage of the energy store above a threshold as soon as the engine starts to operate, a very short time after the "awakening" of the vehicle. The possibility of having a voltage close to 0V in the extended stopping phase of the vehicle is incompatible with the minimum voltage requirement at the start of the engine.

According to the invention, it achieves a pre-charge of the electrical energy storage using another source of energy upon awakening of the computers of the vehicle. This awakening generally takes place by sending a signal characteristic of imminent use of the vehicle, for example the unlocking action of the vehicle doors with a remote control (also called "plip").

The patent application FR 2 791 481 proposes a method according to which a central unit of a vehicle performs an advance charge of a backup accumulator when it detects a signal representative of the intention of the driver to proceed. when starting the vehicle. However, as the charge of the accumulator or the super capacitor by the alternator only begins after an action on the starting system of the engine (for example, action on the "ignition key"), the The voltage at the terminals of the super capacitor can reach a desired minimum threshold value only after a certain time, at least several seconds. This is what happens if the load of the energy storage is carried out for example using the alternator since the latter only works if the engine is started. As long as the energy store is not recharged, some functions are not available, in particular the DC / DC converter can not transmit the energy of the electric machine (the alternator) and the energy consumers 13 (such as lighting or air conditioning elements) are only powered on the battery, the risk of falling voltage. The architecture shown in Figure 1 is therefore hardly compatible with a comfortable use of the vehicle.

In addition, if the energy store 10 is recharged using the battery 12, through the converter 1 1, the charging voltage is limited to the voltage of the battery (12 volts), less the difference in voltage between the input and the output of the converter. It is therefore not possible to charge the energy store 10 to a voltage greater than, at most, the voltage of the battery 12.

The present invention provides a method of recharging the energy store removing, at least in part, the disadvantages of the prior art. According to the invention, the method consists of dividing said storage device into at least two electrical energy storage modules, to connect in series said modules during their use for the supply of electrical energy and to connect them in parallel for recharging. said storer using a source of electrical energy, a battery for example. The electrical energy store may for example be divided into two substantially identical storage capacity modules. According to the invention, the method consists in dividing said storage unit (21) into n electrical energy storage modules (25-26), each storage module i having, at full load, a voltage at these terminals. V _imax, characterized in that the modules are connected in series to obtain the equivalent of a storage unit whose voltage at the terminals, at full load, is equal to

and the modules are connected in parallel to obtain the equivalent of a circuit comprising n electrical energy storageers of a full load voltage equal to VV _max [0013] Thus, when the modules are connected in parallel, they can be recharged "at full charge" by the battery, quickly, until a state of charge is reached in which the voltage at their terminals is for example about 2/3 of their maximum voltage, and from from this moment, be connected in series, so that they are then able to provide a voltage equal to the sum of the voltages of each module.

In a preferred embodiment, the modules are supercapacitors and are two in number, each being able to provide a maximum voltage of the order of 15 volts.

The method according to the invention is particularly advantageous if the vehicle has been left stationary for a long enough period, so that energy storage are completely discharged. The parallel connection of the modules can advantageously be controlled by a signal representative of the intention to start the vehicle - hence with a recharge of the super-capacitors up to a voltage of about 10 volts which can be obtained very quickly with a battery of 12 Volts. As soon as this charging is complete, the modules are connected in series and are therefore able to provide a voltage of about 20 volts, sufficient to restart the vehicle so for example to operate immediately in Stop and Start mode. Preferably, the recharging of the energy store by the battery is through a DC / DC converter.

The invention also relates to a device for charging an electrical energy store of a vehicle comprising a source of electrical energy and a DC / DC converter connected in series between said storage of electrical energy and said source. According to the invention, said storage unit is constituted by at least two electrical energy storage modules and the device comprises connection means in series or in parallel with said modules, said connection means being able to consist of switches.

Said energy source may be a battery.

Said modules for storing electrical energy may consist of batteries or super-capacitors.

Other advantages and features of the invention will become apparent from the following description of an embodiment of the invention, given by way of non-limiting example, with reference to the accompanying drawings and in which:

FIG. 1 represents the electrical architecture conventionally used for the devices of the prior art; FIG. 2 shows the electrical diagram of the device according to the invention;

- Figures 3 and 4 show the diagram of the device according to the invention when the storer is in normal use position (Figure 3) and specific charging position (Figure 4).

In Figure 2, an electric machine 20 of a vehicle, such as an alternator, preferably reversible, is operated when the engine (not shown) of the vehicle is running. In this case, the electrical machine 20 supplies electrical power to a storer 21 and a source of electrical energy such as a battery 22. A DC / DC converter 23 is placed between the energy store 21 and the battery 22. The latter has one of its two terminals connected to a reference potential (the earth) and the other terminal to the converter 23 and to the various power-consuming devices powered by the onboard network (power supply symbolized by the arrow 24). According to the invention, the electrical energy store 21 consists of several electrical energy storage modules, in the example of FIG. 2, two modules 25 and 26. These modules can be, for example, supercapacitors or batteries. . Switches 27 and 28 make it possible to connect these modules, either in series or in parallel. Each of the two switches has two poles: for the switch 27, a first pole 29 connected to earth and a second pole 30 connected to one of the two terminals of the first module 25, the other terminal being connected to the electrical machine 20 The two poles 31 and 32 of the switch 28 are respectively connected to the electrical machine 20 and to one of the two terminals of the storer 26, the other terminal being connected to the earth. A conductive element 33 makes it possible to interconnect the poles 30 and 32 so as to connect the modules 25 and 26 in series.

Figure 3 shows the circuit diagram of Figure 2 with the modules 25 and 26 connected in series, the two switches 27 and 28 being closed on the conductive element 33. Note that in this case, the two modules 25 and 26 form an energy store equivalent to the storer 10 of FIG. 1. This arrangement is used when the storer is not in a specific charging position, for example when he is supplying power to a device (for example example to the reversible alternator 20 for starting the engine or to provide additional traction to the vehicle.

Figure 4 shows the two modules 25 and 26 connected in parallel, for the specific recharge of the energy store. Both modules can be recharged using the 12 Volt battery. If the voltage drop across the converter 23 is ignored, both modules are each charged at a voltage equal to that of the battery (12 volts). When switching switches 27 and 28 to connect the modules 25 and 26 in series (FIG. 3), the voltages at the terminals of the modules

25 and 26 are added: there is then a voltage of two times twelve volts, or 24 volts, at the terminals of the electrical energy store consists of the two modules connected in series. This provides a sufficient recharge to, for example, start the engine (when the electric machine 20 is a reversible alternator).

Switches 27 and 28 may be electromechanical, electrical or electronic. The two energy storage modules 25 and

26 can be super-capacitors or a 24V battery separated into 2 modules of 12V or two batteries of 12 Volts each. The control of the switches 27 and 28 is advantageously activated by a signal characteristic of the driver's desire to use the vehicle, for example by an action on the remote control of the vehicle or by the opening of a door. The control of the switches 27 and 28 is controlled by an electronic control according to the vehicle information (voltage measurements at the terminals of the battery 22 and the energy storage modules 25 and 26, depending on the state of the converter, ...), the electronic control can also control the converter. This electronic control can be provided by the central controller of the vehicle or by a microprocessor specially programmed to control the recharging of the energy store. The latter can be carried out periodically during the stopping of the vehicle by an alarm clock of the electronic control (for example every 3 or 4 days in case of prolonged stop of the vehicle).

The architecture with switches, which has just been described with reference to Figures 2-4, allows the almost complete recharge (greater than 15 volts) of the electrical energy storage with a battery of 12 volts, before the starting the vehicle. The alternator no longer has to perform additional charging after startup and all possible functions with a Reversible alternator (Stop & Start, braking energy recovery, additional energy supply to the engine) are available immediately.

Other embodiments than that described and shown may be designed by those skilled in the art without departing from the scope of the present invention. For example, the electrical energy store 10 has been split into two modules, but it could have been in a larger number. The word "recharge" previously used for the electrical energy storage also includes the load of the storer.

Claims

A method of recharging an electrical energy store (21) of a vehicle comprising an electric power source (22) and an alternator, the method being characterized by dividing said storage container (21). ) in n modules of storage of electrical energy (25-

26), each storage module i having, at full load, a voltage at these terminals

characterized in that the modules are connected in series to obtain the equivalent of a storage unit whose voltage at the terminals,

at full load, is equal to

z max and the modules are connected in parallel to obtain the equivalent of a circuit comprising n electrical energy storage of a voltage at full load equal to £ Vj _max

2. Method according to claim 1, characterized in that the parallel connection is controlled when the state of charge of the energy store is less than a minimum threshold voltage.

3. Method according to claim 1 or 2, characterized in that the parallel connection of said modules is controlled by a signal representative of the intention to start the vehicle.

4. Method according to one of the preceding claims characterized in that the electrical energy store (21) is divided into two modules (25-26) of substantially identical storage capacity.

5. Method according to one of the preceding claims characterized in that the source of electrical energy (22) is a battery and recharging the energy store by the battery is through a DC / DC converter (23) .

6. Device for charging an electrical energy store (21) of a vehicle having a source of electrical energy (22) and a DC / DC converter (23) connected in series between said storer of electrical energy and said source, characterized in that said storer is constituted by at least two electrical energy storage modules (25-26) and in that the device comprises connecting means (27-28-33) in series or in parallel with said modules.

7. Device according to claim 6 characterized in that said connection means are constituted by switches (27-28).

8. Device according to one of claims 6 and 7 characterized in that said storage modules of electrical energy are constituted by batteries.

9. Device according to one of claims 6 and 7 characterized in that said power storage modules are constituted by super-capacitors.

10. Device according to one of claims 6 and 9 characterized in that said source of electrical energy is a battery.