FR3067681A1 - VERY LOW VOLTAGE SYSTEM FOR HYBRID MOTOR VEHICLE, ASSOCIATED MOTOR VEHICLE AND METHOD FOR PASSING FROM A FIRST TO A SECOND RUN MODE - Google Patents

Abstract

Since the hybrid motor vehicle is equipped with a traction engine and an electric traction machine, the system includes a main low-voltage power supply battery, a secondary low-voltage power source, very low-voltage edge, comprising a plurality of electrical members, arranged to be powered by at least one of the two sources comprising the main battery and the secondary source, a starter (2) arranged to start the engine by consuming power electric power supplied by the main battery (BTBT_1). According to the invention, said system also comprises a switch device (3) placed on a link (4) for supplying the on-board network (1) by the main battery (BTBT_1) and arranged to electrically isolate the onboard network (1 ) of the main battery (BTBT_1) and the starting device (2) during a transient phase of starting the engine using said starting device.

Description

VERY LOW VOLTAGE SYSTEM FOR A HYBRID MOTOR VEHICLE, ASSOCIATED MOTOR VEHICLE AND METHOD FOR GOING FROM A FIRST TO A SECOND RUNNING MODE [0001] The present invention relates to a very low voltage system or architecture for a hybrid motor vehicle, a hybrid motor vehicle incorporating such a system as well as a method for switching from a first exclusively electric driving mode to a second driving mode using a heat engine, in a hybrid motor vehicle.

In known manner, a hybrid motor vehicle comprises a traction thermal engine, for example of the petrol or diesel type, and a low tension electric traction machine powered by batteries. The batteries can be recharged by this electric machine while the vehicle is running and / or by connection to an electrical distribution network.

The electric machine can generally operate in vehicle traction mode or in generator mode. In vehicle traction mode, it uses the energy supplied by the batteries to drive the vehicle. In generator mode, it uses the kinetic energy of the vehicle when driving to recharge the batteries.

With a hybrid vehicle, different operating or driving modes are achievable. A first mode uses only the heat engine to drive the vehicle. A second mode, called "electric" or "exclusively electric" or "ZEV" (from English "Zero

Emission Vehicle ”), without emission of polluting gases, only uses the electric machine to drive the vehicle forward. Finally, a third mode called "hybrid" uses both the engine and the electric machine to drive the vehicle.

-2 In operation, while the vehicle is moving, it may be necessary to switch from a first driving mode to a second driving mode. For example, while the vehicle is driving in exclusively electric mode, the heat engine can be started to switch to a driving mode using only the heat engine or in hybrid mode. This requires exiting the exclusively electric driving mode and starting the engine while the vehicle is moving.

Document FR2994152 describes a method for managing the output of a solely electric driving mode for a hybrid vehicle comprising a traction thermal engine and an electric traction machine powered by batteries. The electric driving mode is degraded in the case of heavily discharged batteries. Depending on the exit conditions from this degraded driving mode to a hybrid mode, different strategies for starting the combustion engine are applied. These strategies necessarily include keeping the engine running for a defined time or over a minimum distance traveled by the vehicle.

[0007] In a hybrid vehicle, it is known to start the heat engine using an alternator-starter or starter. The alternator-starter is a device placed between the heat engine and a main battery of very low voltage electrical power or "TBT". The expression "very low voltage" or "TBT" is understood here to mean the voltages less than or equal to 60V. The TBT battery is intended to supply a vehicle TBT network, commonly called an “on-board network”, comprising various electrical components. The alternator-starter has a first starter function, to start the internal combustion engine using the main TBT battery, and a second generator function, to recharge the battery using the kinetic energy supplied by the running thermal engine.

Starting the engine using the starter or alternator-starter places a heavy load on the main battery TBT, which generally has the effect of lowering the voltage of the on-board network. Such a

-3 drop in voltage, while the vehicle is moving, may cause discomfort for the driver. In some situations, this can even be potentially dangerous. For example, suppose that a binding event requiring sudden avoidance or that emergency braking occurs during the start-up phase of the engine using the starter or alternator-starter. In order to correct the vehicle's trajectory or brake in an emergency, on-board network security equipment, such as an ESP (in English Electronic Stability Program), intervenes and must suddenly consume a large amount of electrical energy drawn from the TBT battery. In such a situation, the voltage drop linked to the starting of the heat engine can disturb, or even prevent, the proper functioning of the ESP safety equipment of the vehicle.

The present invention improves the situation.

To this end, the invention relates to a very low voltage system for a hybrid motor vehicle equipped with a thermal traction engine and an electric traction machine, comprising:

• a main low-voltage power supply battery;

• a secondary source of very low voltage electrical power;

• a very low voltage on-board network, comprising a plurality of electrical components, capable of being supplied at least by one of the elements of the group formed by the main battery and the secondary source;

• a starter arranged to start the internal combustion engine by consuming electrical energy supplied by the main battery, characterized in that said system comprises a switching device placed on a supply link of the on-board network by the main battery and arranged for electrically isolate the on-board network from the main battery and the starting device during a transient phase of starting the heat engine using the starting device.

Advantageously, the switching device is arranged to electrically isolate the on-board network from the main battery during the transient phases of starting the heat engine using the starting device (starter or alternator-starter), while the vehicle is in driving mode exclusively with the electric traction machine.

The addition of a switching device between the very low voltage main battery and the on-board network of the vehicle makes it possible to electrically isolate, temporarily, the on-board network of the main very low voltage or TBT battery and the starting device (itself connected to the main battery), when starting the engine, while the vehicle is traveling using exclusively the electric traction machine or while the vehicle is initially stopped. This makes it possible to make the on-board network voltage insensitive to disturbances relating to the starting of the engine.

According to a first aspect of the invention, the secondary source comprises a voltage converter between said electrical machine and the on-board network. When the switch device associated with the main battery is opened, the on-board network can continue to be supplied by the voltage converter, for example a DC-DC (from the “Direct Current”), between the electric machine and the on-board network.

According to a second aspect of the invention, the secondary source comprises an additional or auxiliary battery of very low voltage electrical power supply, arranged to be recharged by a voltage converter between said electrical machine and the on-board network.

The use of an additional, or auxiliary TBT battery, guarantees the supply of a sufficient amount of electrical energy and with a very fast response time, compatible with sudden current calls from security organs. energy-consuming such as ESP or electric power steering. The system of the invention is thus capable of rapidly supplying the electrical energy necessary in the event of stress on one or more organs

-5electric from the on-board network during the start-up phase of the heat engine while the vehicle is in exclusively electric driving. This turns out to be particularly advantageous when an electrical member consuming a great deal of electrical energy, for example trajectory correction or electric power steering equipment, is activated during this transient phase of starting the thermal engine to switch from a mode of electric driving in a driving mode using the heat engine.

Advantageously, the system includes another switching device, associated with the additional battery. This other switching device can be arranged to open when the vehicle is in inactive traction mode (that is to say when neither the heat engine nor the electric machine are activated, the vehicle being stopped) and / or in the event of an additional battery overvoltage.

Advantageously also, the starting device is an alternator-starter. This can be arranged to recharge the main battery when the heat engine is running.

The switch device associated with the main battery can integrate a module for diagnosing the state of the main battery.

The switch device associated with the additional battery can integrate a module for diagnosing the state of said additional battery.

According to another aspect of the invention, the additional battery is connected between an electrical ground point and a supply link of the on-board network by the voltage converter.

The invention also relates to a hybrid motor vehicle comprising a traction thermal engine, an electric traction machine and a very low voltage system as defined above.

The invention also relates to a method for switching from a first to a second driving mode for a hybrid motor vehicle, said vehicle comprising a traction thermal engine, an electric machine

-6 traction, a main battery of very low voltage electrical power, a secondary source of very low voltage electrical power and a very low voltage on-board network, the first driving mode being exclusively electric and the second driving mode using the internal combustion engine, said method comprising a step of starting the electric motor using said main battery implemented by a starting device, for example while the vehicle is in driving mode exclusively with the electric traction machine, characterized in that 'It comprises a step consisting in electrically isolating the on-board network from the main battery and from the starting device before said step of starting the heat engine, the on-board network then being supplied by the secondary source.

Other characteristics and advantages of the present invention will appear more clearly on reading the following detailed description of an embodiment of the invention given by way of non-limiting example and illustrated by the accompanying drawings, wherein :

FIG. 1 represents a diagram of a very low voltage system of a hybrid motor vehicle, according to a particular embodiment of the invention;

FIG. 2 represents a flow diagram of the steps of the method according to a particular embodiment of the invention.

It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention defined by the appended claims.

In Figure 1, there is shown schematically a system, or architecture, very low voltage 100 of a hybrid vehicle VH.

The terms "very low voltage" or "TBT >> or" Low Voltage >> designate a range of electrical voltages whose limits have been set by standards and / or in a regulatory manner. More specifically, in the

-7present description, the expression "very low voltage" designates the field of electrical voltages less than or equal to 60 Volts in direct current.

The VH hybrid vehicle includes a traction thermal engine, for example of the petrol or diesel type, and an electric traction machine, not shown in FIG. 1.

The electrical machine is connected to low-voltage Bbt batteries. In a known manner, these Bbt batteries comprise, for example, electrochemical cells or capacitors grouped into one or more modules connected in series or in parallel. The electric machine is here of low voltage type. Its nominal operating voltage is for example 200 Volts, 300 Volts or more.

Low voltage or "BT >> or" High Voltage >> designates a range of electrical voltages whose limits have also been set by standards and / or in a regulatory manner. More precisely, in the present description, the “low voltage” designates the field of electrical voltages greater than 60V and less than 1500 V in direct current.

The electric machine is intended to run the VH hybrid vehicle by consuming the electric energy supplied by the low-voltage batteries Bbt- The Bbt batteries can be recharged by the electric machine during the running of the VH vehicle and / or by connection to an electrical distribution network.

The TBT 100 system of the hybrid vehicle VH comprises a main battery of very low voltage electrical power supply Btbtj, one or more secondary sources of very low voltage electrical power supply or TBT, a very low voltage on-board network or TBT 1 and a starting device 2, for example an alternator-starter or a starter.

TBT on-board network 1 comprises, in known manner, a set of electrical components such as various computers, lighting devices (vehicle lights, interior lighting), a device for

-8 air conditioning, vehicle trajectory correction equipment, for example an ESP (Electronic Stability Program) device, a DAE device for electric power steering, etc. It has a nominal operating voltage belonging to the field of very low voltage or TBT, for example 12 Volts.

The main battery TBT Btbt_i is intended to supply the on-board network 1. According to the invention, it is connected to the on-board network 1, by means of a switch device 3, and to an electrical ground point M of the VH hybrid vehicle. The switching device 3 is placed on a supply line 4 of the on-board network 1 by the main battery B _T bt_i- H is connected to the battery Btbt_i, to a power supply input of the on-board network 1 and to ground M The role of the switching device 3 is to electrically isolate the on-board network 1 from the main battery B _TB t_i and from the starting device 2. In the example described here, it is designed to open or close the supply link 4 between the on-board network 1 and the main TBT battery Btbt_i The alternator-starter or starter 2 is placed between the engine (not shown) and the main TBT battery B _T bt_i- The alternator starter or starter 2 a a first starter function to start the internal combustion engine by consuming electrical energy supplied by the main battery TBT Btbt_i and a second generator function to recharge the battery B _T bt_i using the kinetic energy f provided by the engine running. In known manner, it is here connected to the battery B _T bt_i by means of a safety fuse 6.

A first secondary source of very low voltage power supply here comprises a voltage converter 5 intended to convert the voltage between the low voltage electric machine (not shown) and the very low voltage on-board network 1. The voltage converter 5 is connected to an output of the electrical machine, to a power supply input from the on-board network 1 and to earth Μ. It includes here a DC-DC converter (from the English "Direct Current" for direct current) intended to convert a source of direct current (DC) of a

-9 level of tension to another. In this case, it has the function of converting the LV type voltage delivered by the low voltage electric machine (for example 200V, 300V or more) into a TBT type voltage supply from the on-board network 1 (here 12V) . The converter 5 is connected to the on-board network 1 via a second TBT power supply link 7.

A second secondary very low voltage power source here comprises an extra or auxiliary very low voltage battery Btbt_2- Its role is to supply a power supply voltage TBT to the on-board network 1, here a nominal voltage of 12V, in particular to replace the main battery B _T bt_i in certain situations, as will be described later. The secondary battery TBT is connected between earth M and the link 7 (for example at a connection point 8 of the link 7). It is thus connected to a power supply input of the on-board network 1. The battery B _T bt_2 is arranged to be recharged by the voltage converter 5, using the electrical energy supplied by the electrical machine.

A switch device 9 can be associated with the additional battery Β _Τ βτ_2 · It is interposed between the additional battery B _T bt_2 and the power supply link 7 (or the power supply input of the on-board network 1) and is also connected to earth M of the vehicle VH. It makes it possible to open or close the link between the additional battery Btbt_2 and the supply link 7. In a particular embodiment of the invention, the switch device Btbt_2 is open when the vehicle is in inactive traction mode ( that is to say when neither the heat engine nor the electric machine exerts a traction action, the vehicle being stopped). The switching device 9 can also be designed to open in the event of abnormal overvoltage / overheating of the additional battery B _T bt_2- Apart from these situations (traction mode inactive and abnormal overvoltage / heating of the additional TBT battery), the switch device 9 is here closed. The additional TBT battery Btbt_2 is thus connected to the converter 5 and to the on-board network 1. It can be recharged by the converter 5 and makes it possible to supply the on-board network 1. On

- 10 could however consider other strategies for controlling the opening and closing of the switching device 9 associated with the auxiliary TBT battery B _TB t ₂ In any event, the switching device 9 is closed during an engine start-up phase while the vehicle is in exclusively electric driving mode, in order to supply the on-board network 1 during this period.

A safety fuse 10 can also be provided on the link between the additional battery, the Btbt_2 battery and the power supply link.

7.

The switch device 3 associated with the main TBT battery Btbt_i can integrate a diagnostic module arranged to assess the state of the main battery Btbt_i, in particular its electrical capacity.

Similarly, the switch device 9 associated with the additional TBT battery B _T bt_2 can integrate a diagnostic module arranged to assess the state of the main battery Btbt_2, in particular its electrical capacity.

The system also includes a control device, not shown, intended to control the operation of the starting device 2 and the switching devices 3 and 9.

We will now describe the operation of the TBT system

100 of the VH hybrid vehicle in a situation where the VH vehicle leaves an exclusively electric driving mode and goes into a driving mode using the heat engine. This operation corresponds to a method for switching from a first to a second driving mode for the VH hybrid motor vehicle, the first driving mode being exclusively electric and the second driving mode using the heat engine.

[0043] During a step E1 of driving in electric mode, the vehicle VH is initially running in exclusively electric mode,

- 11 that is to say that it only uses the electric traction machine to drive (the thermal engine is stopped).

In a step E2, an instruction is transmitted to the control device to switch from exclusively electric mode to a mode using the heat engine, for example the mode using only the heat engine or the hybrid mode. The mode change instruction can be generated by a driving mode management computer of the VH hybrid vehicle automatically or following a command from the driver. For example, the mode change can be triggered by the taxiing mode management calculator in the event of detection of a state of charge of the low-voltage batteries Bbt supplying the electrical machine, which is below a predefined threshold.

Then, during a transient step E3, which will be detailed below, the VH hybrid vehicle leaves the exclusively electric mode to enter the mode using the heat engine.

Finally, during a step E4, the hybrid vehicle drives in the driving mode using the heat engine (either the mode using only the heat engine, or the hybrid mode, depending on the choice of the control device).

The transient step E3 of switching from the first exclusively electric mode to the second mode using the heat engine comprises a first step E31 of electrical isolation of the on-board network 1 during which the on-board network 1 is electrically isolated from the battery main Btbtj and of the starting device 2. More precisely here, the switching device 3 associated with the main TBT battery Btbtj is open to electrically isolate the on-board network 1 from the main battery B _TB t_i and from the starting device 2. Thus, the power supply link 4 between the main battery B _T bt_i and the on-board network 1 is interrupted. The on-board network 1 is temporarily disconnected, electrically isolated, from the main battery Btbtj but continues to be supplied here by the two secondary sources, namely the converter 5 and the additional battery TBT B _T bt_2- During a second

- 12 step E32, the alternator-starter 2 starts the heat engine using the electrical energy supplied by the main battery Btbtj · [0048] During a next step E33, after starting the heat engine, the switch device 3 is closed in order to connect, or electrically connect, the on-board network 1 again to the main battery B _T bt_i [0049] Thanks to the temporary opening of the supply link 4, the main battery Btbtj is isolated from the on-board network 1 and the starting device 2 during the transient phase of activation of the starting device 2 (that is to say during the transient phase of starting the heat engine). The on-board network 1 is thus preserved from a voltage drop linked to the starting of the heat engine but continues to be supplied by the converter 5 and by the secondary battery Btbt_2 (the switching device 9 being closed).

The use of the additional TBT battery has the advantage of providing the on-board network 1 with sufficient electrical energy, whatever the needs of the on-board network, and this with a very rapid response time, which is compatible with sudden and energy-consuming current calls (ESP or DAE for example), during the starting phase of the electric motor while the VH hybrid vehicle is in exclusively electric driving mode. This is particularly advantageous in a situation where a large energy-consuming electrical member, for example ESP equipment or electric power steering, of the on-board network 1 is activated during this phase of starting the heat engine.

Instead of using a main battery Btbtj and two secondary sources (converter 5 and additional battery Btbt_2) for supplying the on-board network 1, the system could use only the main electrical storage device Btbtj (instead of the two electrical storage devices B _T bt_i and B _T bt_2) if the occurrence of the risk of unavailability of the ESP or DAE is deemed acceptable. For example, one could not use an additional battery Btbt_2- This additional battery B _tbt _2 makes it possible to eradicate the risk of insufficient energy available in the occurrence of consequent current calls during the phase

- 13 critical transient for switching from a ZEV traction mode to a mixed thermal / electric traction mode.

In the foregoing description, the switch device 3 associated with the main battery B _T bt_i makes it possible to electrically isolate the on-board network 1 from the main battery B _T bt_i and from the starting device 2 during a starting phase of the internal combustion engine while the vehicle is in an exclusively electric driving phase. The invention could also apply to a situation where the vehicle is not in an exclusively electric driving phase, in particular when the heat engine is started while the vehicle is stopped (no traction mode being active ).

Claims (10)

1. Very low voltage system for a hybrid motor vehicle equipped with a traction thermal engine and an electric traction machine, comprising: • a main battery (Btbtj) for very low voltage power supply; • a secondary source (5, Btbt_2) of very low voltage power supply; • a very low voltage on-board network (1), comprising a plurality of electrical components, capable of being supplied at least by one of the elements of the group formed by the main battery (Btbtj) and the secondary source (5, Btbtj) ; • a starting device (2) arranged to start the heat engine by consuming electrical energy supplied by the main battery (Btbtj), characterized in that said system comprises a switching device (3) placed on a link (4) on-board power supply (1) by the main battery (Btbtj) and designed to electrically isolate the on-board network (1) from the main battery (Btbtj) and the starting device (2) during a transient phase starting the heat engine using said starting device (2). 2. System according to claim 1, characterized in that the switching device ( 3) is arranged, on command of a control device, to electrically isolate the on-board network (1) from the main battery (Btbtj) and from the starting device (2) during a starting phase of the internal combustion engine using said starting device (2) while the vehicle is in driving mode exclusively with the electric traction machine. - 153. System according to one of the preceding claims, characterized in that the secondary source comprises at least one of the elements of the group comprising a voltage converter (5) between said electrical machine and the on-board network (1) and an additional very low voltage power supply battery (Btbt_2), arranged to be recharged by a voltage converter (5) between said electric machine and the on-board network (1). 4. System according to claim 3, characterized in that it comprises another switching device (9) associated with the additional battery (Btbt_2), arranged to open when the vehicle is in inactive traction mode. 5. System according to claim 3 or 4, characterized in that the switch device associated with the additional battery (Btbt_2) is arranged to open in the event of overvoltage of the additional battery (Btbt_2). 6. System according to one of the preceding claims, characterized in that the starting device is an alternator-starter arranged to recharge the main battery (Btbt_i) when the heat engine is running. 7. System according to one of the preceding claims, characterized in that at least one of the switching devices (2, 9) includes a module for diagnosing the state of the associated battery (Btbtj, Btbt_2). 8. System according to claims 3 to 7, characterized in that the additional battery (Btbt_2) is connected between an electrical ground point (M) and a connection (7) supplying the on-board network by the voltage converter ( 5). 9. Hybrid motor vehicle comprising a thermal traction engine, an electric traction machine and a very low voltage system as defined by one of the preceding claims. - 1610. Method for switching from a first to a second driving mode for a hybrid motor vehicle, said vehicle comprising a traction thermal engine, an electric traction machine, a main battery of very low voltage electrical power supply (Btbt_i) , a secondary source 5 very low voltage electrical supply (5, Btbt_2) and a very low voltage on-board network (1), the first driving mode being exclusively electric and the second driving mode using the heat engine, said method comprising a step ( E32) for starting the electric motor using said main battery (Btbtj) implemented by a starting device (2), characterized 10 in that it comprises a step (E31) consisting in electrically isolating the on-board network (1) from the main battery (Btbt_i) and from the starting device (2) before said step (E32) of starting the heat engine, the on-board network (1) then being supplied by the secondary source (5, Btbt_2).