FR2999991A1 - System for cooling traction battery of e.g. hybrid motor vehicle, has cooling devices utilizing fluid internal and air external to vehicle as internal and external sources, respectively, to cool battery during stopping phase of vehicle - Google Patents

Abstract

The system has a cooling device (3) for utilizing the fluid internal to a motor vehicle as an internal cold source to cool a traction battery (1) of the vehicle during a stopping phase of the vehicle. Another cooling device (4) utilizes the air external to the vehicle as an external cold source to cool the battery during the stopping phase. A driving device selects one of the cooling devices according to the respective temperatures of the cold sources, and controls starting of the selected cooling device during the stopping phase.

Description

The invention relates to a cooling system of a motor vehicle battery. A hybrid motor vehicle comprises a heat engine and an electric motor powered by a traction battery. In the driving phase of the vehicle with the electric motor, the temperature of this battery increases rapidly. FIG. 1 shows the theoretical evolution of the temperature Ti of a motor vehicle traction battery as a function of time t, in the case of a vehicle without a battery cooling system. Moments t1 and t2 respectively represent the start and end times of a driving phase of the vehicle with the electric motor powered by the battery. Initially, in the figure, at the instant LI the temperature of the battery is 34 ° C. During the rolling phase, the temperature Ti increases rapidly to reach at time ti a high temperature denoted Ti H, between 55 ° C and 60 ° C, then the temperature Ti of the battery stagnates at the high value Ti H between moments t1 and t2. At time t2, the vehicle is stopped. The period after time t2 is a so-called parking phase, or stop, during which the vehicle is parked, at a standstill, without charging the battery. During this parking phase, the temperature Ti decreases. However, it can be seen in FIG. 1 that this reduction is very slow and that, after the lapse of about two hours of parking, the temperature Ti remains high, higher than 35 ° C. In practice, the operation of a hybrid vehicle is controlled by a law of energy management. According to this law, by default, the electric motor is used in rolling phase. However, since the temperature of the battery supplying the electric motor reaches a first threshold 51, between 45 and 50 ° C, the power delivered by the battery is voluntarily limited. This is what the skilled person calls the "derating". Above a second threshold S2, of the order of 60 ° C, the use of the electric motor is interrupted and, where appropriate, the heat engine is used instead.

The motor vehicle is generally equipped with a battery cooling system for cooling the battery while driving. This not only avoids the derating, but also improves the life of the battery.

FIG. 1 shows the evolution of the temperature T2, as a function of the time t on the abscissa, of a traction battery of a motor vehicle equipped with a cooling system. In operation, during the driving phase from instant to time t2, the battery is cooled. Initially, at time to, the temperature of the battery is 34 ° C in Figure 1. During the rolling phase, the temperature T2 rises and then stabilizes globally around a high value noted T2H of the order of 40 ° C. During the parking phase after time t2, the temperature T2 decreases but slowly. The temperature T2 of the battery remains greater than 35 ° C for a period of at least two hours after the start t2 of the parking phase. However, if at the restart of the vehicle, the battery has not had time to cool sufficiently, its temperature may not be low enough to avoid a "derating" shortly after restarting.

The present invention improves the situation. To this end, the invention relates to a cooling system of a traction battery of a motor vehicle, characterized in that it comprises a cooling device arranged to use a fluid internal to the vehicle as an internal cold source for cooling the vehicle. battery during a stop phase of the vehicle. The invention proposes to use a fluid internal to the vehicle, for example the air of the passenger compartment, after stopping the vehicle. When the vehicle is stopped, the central HVAC system of the vehicle ("Heating Ventilation and Air-Conditioning") is usually shut down to avoid excessive energy consumption. However, the air conditioning present in the passenger compartment of the vehicle remains cold for several minutes after stopping the vehicle. Thanks to the invention, this air conditioning can be used to quickly cool the battery after stopping the vehicle. Instead of the air of the passenger compartment of the vehicle could be used for example the water of a cooling water circuit of the vehicle. In a particular embodiment, the system comprises a cooling device arranged to use outside air to the vehicle 10 as an external cold source for cooling the battery during the stopping phase of the vehicle. Alternatively or additionally, the battery can be cooled by the outside air to the vehicle during the stopping phase thereof. Advantageously, the system comprises a control device arranged to select one of the two cooling devices, as a function of the respective temperatures of the internal cold source and of the external cold source, and to control the start-up of the cooling device. Selected during the stopping phase of the vehicle. Thus, when the vehicle is stationary, two cold sources, one internal and the other external, can potentially be used to cool the battery: - the fluid inside the vehicle (cabin air or water). a cooling water circuit for example) and / or - the air outside the vehicle. When the vehicle is stopped, the temperatures of these two cold sources are determined and compared. The cold source with the lowest temperature is selected and used to cool the battery. Take the case where the air outside the vehicle is hot, higher than 25 ° C, and where the air in the passenger compartment is conditioned at a temperature of the order of 20 ° C to 23 ° C. In this first case, the system of the invention uses the air conditioning of the cabin to cool the battery, just after stopping the vehicle. Take the case where the outside air is cold, for example at a temperature below 20 ° C, and where the air in the cabin is warmed to a temperature above the outside temperature. In this second case, the system of the invention uses outside air to cool the battery, just after stopping the vehicle. In a first embodiment, the vehicle having a passenger compartment and a cabin air-conditioning system, the cooling device 10 using an internal cold source is arranged to use the air of the passenger compartment of the vehicle as an internal cold source. In a first embodiment, it comprises a fan adapted to force the flow of air taken either in the passenger compartment of the vehicle or outside the vehicle to the battery. In a second variant embodiment, the cooling device using an internal cold source comprises an exchanger adapted to cool a liquid from the air taken from the passenger compartment of the vehicle. Thus, the cabin air, used as an internal heat sink, can be either driven directly to the battery, or used to cool a liquid, such as water, through an exchanger (or radiator) , intended to cool the battery. In a second embodiment, the cooling device using an internal cold source is connected to a cooling water circuit inside the vehicle, the water of the circuit being used as an internal cold source. In this case, the internal cold source is the water of the cooling water circuit of the vehicle. It may be a dedicated water circuit to cool the battery or able to cool several elements of the vehicle.

Advantageously, the cooling device using an external cold source comprises an exchanger adapted to cool a liquid from the air taken from the outside of the vehicle.

The invention also relates to a motor vehicle incorporating a cooling system as previously defined. The invention will be better understood from the following description of the method and cooling system of the invention, according to various embodiments, with reference to the accompanying drawings, in which: FIG. 2 represents a diagram of the system cooling according to a first embodiment; FIG. 3 represents a diagram of a motor vehicle integrating the cooling system of FIG. 2; FIG. 4 represents a control device for the cooling system of FIG. 2; FIG. 5 represents curves of evolution of the temperature of the cooled battery notably by use of the cooling system of FIG. 2; FIG. 6 represents a diagram of the cooling system according to a second embodiment and FIG. 7 represents a flowchart of the steps of the cooling method according to the invention. From the outset, it will be noted that the corresponding elements of the various modes and embodiments described have the same references, unless otherwise indicated. The cooling system of the invention is intended for cooling a traction battery 1 of an electric or hybrid motor vehicle 2. It comprises a first and a second cooling device 3, 4 of the battery. The battery 1 is here housed in a trunk of the vehicle 2, inside 5 an enclosure. The vehicle 2 is equipped with a HVAC system (Heating Ventilation and Air-Conditioning) able to heat or cool the passenger compartment 6 of the vehicle 2 according to a set of 10 cabin interior temperature set by a user. The vehicle 2 also comprises, in a conventional manner, a 14V onboard electrical network capable of supplying the different on-board electronic equipment. The first cooling device 3 is arranged to use a fluid internal to the vehicle as an internal cold source for cooling the battery. The second cooling device 4 is arranged to use the outside air of the motor vehicle, in other words the air present in the external environment of the vehicle, as an external cold source for cooling the battery. In a first embodiment, the fluid used as an internal heat sink is the interior air of the passenger compartment 6 of the vehicle 2, that is, the conditioned air when the HVAC system is turned on. The first device 3 comprises in this case a conduit 7 communicating with the interior of the passenger compartment 6 and adapted to draw air therein. The second cooling device 4, able to use the outside air to the vehicle to cool the battery 1, comprises a conduit 8 equipped with a filter 9 and communicating with the outside of the vehicle 2, here under the vehicle 2. The 8 is able to draw air outside the vehicle 2. An air supply duct 10 is connected, at an outlet end, to one or more through openings in the wall of the vehicle. enclosure and, at an inlet end, to the conduit 7 and the conduit 8.

A shutter 12 with two positions P1 and P2, here a single flap type "ON / OFF" is mounted at the intersection between the three ducts 10, 7 and 8. When the flap 12 is in the position Pi , the duct 7 is closed and the duct 8 is passing. In this position Pi, air taken outside the vehicle 2 through the conduit 8 is led to the battery 1. When the flap 12 is in the P2 position, the conduit 7 is passing and the conduit 8 is closed. In this position P2, air taken from the passenger compartment of the vehicle 2 via the duct 7 is conducted to the battery 1. The flap 12 is connected to a motor powered by the on-board electrical network of the vehicle.

A fan 11, mounted in the duct 10, is able to pulse the air taken either in the passenger compartment 6 or outside the vehicle 2, to the battery 1. The fan 11 is connected to a motor connected also to the on-board electrical network of the motor vehicle 2.

In Figure 4, there is shown a device 18 for controlling the cooling system. The device comprises three temperature measuring probes 13, 14, 17 and a control module 15. The probes 13, 14 and 17 are adapted to measure respectively: the interior temperature of the passenger compartment 6; the temperature outside the vehicle 2 and the temperature of the battery 1. The control module 15 is connected to: - input to the temperature probes 13, 14 and 17 and to a vehicle computer 16 and - at the output, the fan motor 11 and the shutter motor 12.

The cooling method of the battery 1, corresponding to the operation of the cooling system of the vehicle 2, will now be described, according to a first embodiment.

In FIG. 5, curves Ti and T2, previously explained, are shown. As a reminder, the curve Ti corresponds to the theoretical evolution of the temperature of the battery 1, in the absence of cooling thereof. The curve T2 corresponds to the evolution of the temperature of the battery 1 when the latter is cooled during a rolling phase and uncooled during the stopping phase. The curve T3 represents the evolution of the temperature of the battery 1 during the stopping phase of the vehicle, the battery 1 being cooled during this phase by the cooling system of the invention.

Note the moment of beginning of a rolling phase of the vehicle and t2 the end time of this driving phase and the beginning of a stop phase, or parking, of the vehicle. It is considered here that the vehicle is not in charge during the stopping phase.

During the rolling phase, the battery 1 is cooled in a known manner. For example, the battery 1 is cooled using the cooling device 3 which takes air conditioning in the passenger compartment 6 of the vehicle 2 and pulses this air on the battery through the ducts 7 and 10 and by means of the fan 11. Consideration could be given to directly using the HVAC air conditioning system of vehicle 2 or a dedicated HVAC system to cool the battery while driving the vehicle 2. During the taxiing phase, the battery temperature changes according to the T2 curve. oscillating around a high value T2H of the order of 40 ° C. At time t2, the vehicle 2 is stopped during a step E0. The control module 15 is informed of the shutdown of the vehicle 2 by the on-board computer 16. It then raises the internal temperature Tint in the passenger compartment 6 of the vehicle 2 and the temperature Text outside the vehicle 2 , provided by the probes 13 and 14, in a step El. As a function of the temperature difference ΔT between the internal temperature Tint and the outside temperature Text, the control module 15 selects the cold source SF whose temperature is the lowest (that is to say, the interior air of the passenger compartment 6, or the air outside the vehicle 2), during a step E2. During a step E3, the control module 15 triggers a cooling operation of the battery 1 with the selected cold source SF, substantially at the start time t2 of the stop phase. To trigger the cooling operation, the control device 15 transmits a first control signal SC1 to the valve 12 so that it is positioned in the adapted position P1 or P2, according to the selected cold source, and a second control signal SC2 to the fan 11 to turn it on. During the cooling operation, denoted E4, according to the selected cold source, one of the two ducts 7 and 8 draws air, inside or outside, in the passenger compartment 6 or outside the vehicle 2, and the collected air is led through the duct 10 and by means of the fan 11 to the battery 1. The cold air thus taken and driven can be pulsed directly on the battery or on the enclosure of the battery 1.

In the case where the internal temperature Tint in the passenger compartment 6 is lower than the temperature Text outside the vehicle 2, the control module 15 selects the interior air of the passenger compartment 6 of the vehicle 2 as a cold source for cooling the battery 1 It then transmits control signals to the valve 12 so that it goes into position P2 and the fan 11 to turn on. The conduit 7 thus draws air into the passenger compartment 6 and the fan 11 pulses this air to the battery 1. In the case where the interior temperature in the passenger compartment 6 is greater than the temperature outside the vehicle 2, the control module 15 selects the outside air to the vehicle 2 as a cold source for cooling the battery 1. It then transmits control signals to the valve 12 so that it goes into position P1 and the fan 11 to start working. The conduit 8 thus draws air into the environment outside the vehicle 2 and the fan 11 pulses this air on the battery 1.

FIG. 5 shows the evolution of the temperature T3, during the stopping phase, subsequent to the instant t2, in the event of cooling by the selected cold source (indoor air or outside air) as described above. above. In the example of Figure 5, the selected cold source has a temperature of 23 ° C. It is either the interior temperature of the passenger compartment or the temperature outside the vehicle, depending on the chosen cold source. In FIG. 5, it can be seen that the temperature of the battery 1 decreases rapidly after the instant t2 and that after a cooling time of about 30 minutes here, the temperature of the battery 1 reaches a low value T3B of about 24 ° C and stabilizes at this value.

During the cooling operation E4, the probe 17 regularly reads the temperature of the battery 1, denoted Tbat, and supplies it to the control device 15. The control device 15 thus monitors the evolution of the temperature Tbat of the battery 1 during a step E5, in order to detect a stabilization of the temperature Tbat of the battery 1. A stabilization of the temperature is detected when the temperature Tbat of the battery does not vary substantially during a test period, for example five minutes. If a temperature stabilization Tbat is detected, the cooling operation is interrupted during a step E6.

After the first cooling operation (E0-E6), a second cooling operation can be carried out later, during the stopping phase of the vehicle 2, in the case where the temperature of the battery 1 increases and exceeds a predefined threshold temperature Ts for example 35 ° C. Indeed, following the first cooling operation carried out just after stopping the vehicle 2, the temperature of the battery Tbat may increase because, for example, the vehicle is parked in the sun.

After step E6 of the end of the first cooling operation, the control device 15 continues to monitor the temperature of the battery, during a step E7, by regularly taking the temperature Tbat from the battery 5 1 using of the probe 17. If the temperature Tbat of the battery 1 increases and exceeds the threshold temperature Ts, the control device 15 repeats the steps E1 to E6 previously explained. The cold source (cabin interior air 6 or vehicle outside air 2) with the lowest temperature is selected and a new cooling operation is initiated using the selected new cold source. In the first embodiment that has just been described, the battery 1 is cooled by cold air pulsed directly on the battery or on the battery enclosure. A second embodiment of the cooling system of the invention will now be described with reference to FIG. 6. For the sake of clarity, only the elements of this second embodiment which differ from the elements of the first embodiment will be explained. In the second embodiment, in place of air, the battery 1 is cooled by a liquid, in this case water. One could obviously consider the use of another liquid. The internal cold source used by the first cooling device 3 is the water of a cooling water circuit inside the vehicle. It may be a water circuit specific to the battery 1 or able to cool several elements of the vehicle, such as the battery and power electronics. The external cold source, used by the second cooling device 4, is the air outside the vehicle and there is provided an exchanger 24 (or a radiator) for cooling the water for cooling the battery 1 with the aid of the outside air taken. In FIG. 6, the arrows with patterns represent the cooling water circuit. The arrows without filling represent the air circuit. The vehicle cooling water circuit 2 comprises an HVAC module 20 for water. The cooling system also comprises a conduit 25 for supplying water to the battery 1, equipped with a water pump 26. This conduit 25 communicates at an output end with the battery 1, and at one end of inlet with a duct 21 of the first cooling device 3 and with a duct 22 of the second cooling device 4, via the shutter flap 12. The duct 22 is able to take air outside the vehicle and to conduct cooled water to the conduit 25. It comprises two parts 22A and 22B. The first part 22A communicates with the outside of the vehicle 2 and is equipped with a fan 23. The latter is intended to take the outside air and to pulse it to the exchanger 24. The exchanger 24 has the role cooling water with the withdrawn outdoor air and transmitting this cooled water to the conduit 25 through the conduit portion 22B. The duct 21 is able to take water cooled in the cooling water circuit of the vehicle and to conduct this cooled water to the conduit 25. As previously explained, the shutter 12 has two positions P1 and P2 to allow a cooling of the battery 1 is by the cooled water 30 taken from the water circuit of the vehicle 2, or by water cooled with the outside air.

The water pump 26 is intended to bring the cooling water from the selected cold source to the battery 1. The shutter 12, the water pump 26 and the fan 23 are controlled for a control device 18 similar to that of Figure 4. In addition, the control device 18 is adapted to control the operation of the fan 23. In the second embodiment which has just been described, the battery 1 10 is cooled by water , the internal cold source being the water of a cooling water circuit of the vehicle and the external cold source being the air outside the vehicle. In a variant, the internal cold source is the air of the passenger compartment 6 of the vehicle 2. In this case, the first cooling device comprises an exchanger (or a radiator) for cooling water with the air taken from 15 cabin 6. One could also consider using the water circuit of the vehicle 2 to warm the battery. It would be advisable to adapt a positive thermal coefficient (PTC) on the water circuit.

The method of cooling the battery using the system according to the second embodiment described above is similar to that of FIG. 7.

The cooling system could comprise only one cooling device capable of cooling the battery using the internal cold source. In this case, during a stopping phase of the vehicle, the battery would be cooled from a fluid internal to the vehicle used as a cold source.

It is pointed out that the cooling operation is triggered at the time of the stopping of the vehicle or substantially after, in the minutes following the stopping of the vehicle, and in any event before increasing the temperature of the internal cold source to the vehicle . Combined cooling could also be envisaged using, during the same cooling operation, the two cold sources, internal and external (internal fluid of the vehicle and outside air), during the stopping phase of the vehicle.

Claims (11)

REVENDICATIONS1. Cooling system for a traction battery (1) of a motor vehicle (2), characterized in that it comprises a cooling device (3) arranged to use a fluid internal to the vehicle (2) as an internal cold source to cool the battery (1) during a stopping phase of the vehicle. 2. System according to claim 1, characterized in that it comprises a cooling device (3) arranged to use outside air to the vehicle (2) as an external cold source to cool the battery (1) during the phase d stopping the vehicle. 3. System according to claim 2, characterized in that it comprises a control device (15) arranged to select one of the two cooling devices, according to the respective temperatures of the internal cold source and the external cold source. , and to control the start of the selected cooling device (3, 4) during the stopping phase of the vehicle (2). 4. System according to one of claims 1 to 3, characterized in that the vehicle (2) having a passenger compartment (6) and an air conditioning system of the passenger compartment, the cooling device using an internal cold source (3). ) is arranged to use the air of the passenger compartment (6) of the vehicle as internal cold source. 5. System according to claim 4, characterized in that it comprises a fan (11) adapted to force the flow of air taken either in the passenger compartment (6) of the vehicle (2), or outside the vehicle (2) to the battery (1). 6. System according to claim 4, characterized in that the cooling device (3) using an internal cold source comprises a heat exchanger adapted to cool a liquid from the air taken from the passenger compartment (6) of the vehicle (2). ). 7. System according to one of claims 1 to 3, characterized in that the cooling device (3) using an internal cold source is connected to a cooling water circuit internal to the vehicle (2), the water of the circuit being used as an internal heat sink. 8. System according to one of claims 1 to 7, characterized in that the cooling device (4) using an external cold source comprises an exchanger (24) adapted to cool a liquid from the air taken from the outside the vehicle (2). 15 9. System according to one of claims 1 to 8, characterized in that it comprises - a first conduit (7) adapted to drive the internal cold source; A second conduit (8) adapted to conduct the external cold source; - a shutter (12) arranged to switch between a first position (P1) in which the first duct (7) is closed and the second duct (8) is open and a second position (P2) in which the first conduit (7) is open and the second conduit (8) is closed. 10. System according to one of claims 1 to 9, characterized in that it is arranged to operate from the start of the stopping phase of the vehicle (2) and until stabilization of the battery temperature (1). 10 11. System according to one of claims 1 to 10, characterized in that, during the stopping phase of the vehicle (2), it is arranged to operate a first time at the beginning of the stopping phase and, at least a second time, later during the stopping phase in the case where the temperature of the battery (1) increases and exceeds a predefined threshold temperature.