Abstract:
A cooling device for a motor vehicle, including a cooling circuit configured to cool an engine assembly using a liquid coolant circulated by at least one variable-flowrate pump, the flowrate of each pump being controlled by a control system. The control system is configured to control the flowrate of each pump in a closed-loop regulating system as a function of the temperature of the liquid coolant and of a setpoint temperature.

Description:
BACKGROUND 
     The subject of the invention is a cooling device for an automotive vehicle, comprising a cooling circuit capable of cooling an engine assembly using a coolant circulated by at least one variable flow rate pump. The invention applies advantageously to electric automotive vehicles. 
     In an internal combustion engine, the repeated combustions overheat the parts that are in contact, such as, for example, the pistons, the cylinders, and the valves, and are transmitted to all the mechanical parts of the engine. It is therefore necessary to cool them otherwise there is a risk of destruction. For correct operation, explosion engines thus need an even and suitable temperature. 
     In the case of a vehicle with electrical propulsion, it is also necessary to cool the various elements of the drive system. 
     It is known practice to use a cooling system comprising one or more pumps for circulating a coolant through the engine, and a radiator, which is a heat exchanger used to cool the liquid. In this case, the coolant flow rate is dependent on the engine speed, and is in particular zero when the engine is stopped. 
     It seems desirable to have a cooling device that makes it possible to optimize the operation of the pumps, and in particular to limit their wear and their energy consumption. 
     BRIEF SUMMARY 
     The device according to the invention makes it possible to achieve this objective. 
     The subject of the invention is thus a cooling device for an automotive vehicle, comprising a cooling circuit capable of cooling an engine assembly using a coolant circulated using at least one variable flow rate pump, the flow rate of each pump being controlled by a control system. 
     In the device according to the invention, the control system is able to servo-control the flow rate of each pump in a closed-loop regulation system according to the temperature of the coolant and a setpoint temperature. 
     Thus, the servo-controlling of the flow rate of each pump in closed loop mode makes it possible to limit its wear and its energy consumption. 
     The setpoint temperature may be predetermined according to the temperature outside the vehicle and the speed of the vehicle. 
     The automotive vehicle may be an electric vehicle and the engine assembly may include an electronic driver system. 
     The electric vehicle may include a battery charger assembly, and the cooling circuit is advantageously capable of cooling the charger assembly and the engine assembly. 
     In this case, the device may include a first pump capable of selectively supplying coolant to the engine assembly and a second pump capable of selectively supplying coolant to the charger assembly. 
     To this end, the device may include a first valve capable of preventing a flow of coolant in the charger assembly and a second valve capable of preventing a flow of coolant in the engine assembly. 
     The device may also include a hydraulic restriction for maintaining a minimum flow rate of coolant in the engine assembly. 
     The closed-loop regulation system may include a corrector of proportional-integral type. 
     The corrector may include a saturation block capable of limiting the correction between a minimum value and a maximum value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become more clearly apparent on reading the following description, given as an illustrative and non-limiting example, and with reference to the appended drawings in which: 
         FIG. 1  illustrates, in block diagram form, a cooling device according to the invention, incorporated in an electric vehicle, 
         FIG. 2  illustrates, in block diagram form, a control strategy for the device, and 
         FIG. 3  is a detailed view of a block of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The cooling device  1 , as illustrated in  FIG. 1 , comprises a first electric pump  2 , a second electric pump  3 , a battery charger  4 , an engine assembly  5 , a radiator  6 , as well as a first solenoid valve  7  and a second solenoid valve  8 . The first electric pump  2 , the second electric pump  3 , the first solenoid valve  7  and the second solenoid valve  8  are linked to a control device  9 . 
     The first electric pump  2  is intended to be used when the vehicle is running, whereas the second electric pump  3  is intended to be used when recharging the battery. The flow rate of the first pump  2  and the flow rate of the second pump  3  can be set using a control signal. 
     The charger  4  is used, when the vehicle is stopped, to recharge the electric traction battery, not represented, from the domestic electric mains system. 
     The first solenoid valve  7  is used to short-circuit the second pump  3  and the charger  4 , when the vehicle is running, whereas the second solenoid valve  8  is used to short-circuit the engine assembly  5  when recharging the battery, when it is estimated that the cooling of the engine assembly  5  is not necessary. The second solenoid valve  8  may be linked to a hydraulic restriction  10  which is used to produce a head loss and thus retain a flow rate of coolant in the engine assembly  5 , even when the second solenoid valve  8  is in passing mode. 
     The engine assembly  5  comprises an engine  11  and an electronic driver system  12  intended in particular to convert the DC voltage from the battery into AC voltage. 
     The radiator  6  is used to cool the coolant, in a manner similar to the cooling device of an internal combustion engine. It is equipped with an electric fan, not represented. 
     The engine assembly  5  has to be cooled when the vehicle is running, as does the charger  4  when the vehicle is stopped. The cooling strategy is managed by the control device  9 . The control device  9  is a computer which is linked with sensors of the cooling circuit, in particular coolant temperature sensors. The computer  9  drives the pumps  2 ,  3 , the solenoid valves  7 ,  8 , and the electric fan set of the radiator  6 . The computer  9  is also advantageously linked to other computers of the vehicle, via a CAN (Controller Area Network) bus-type network for example, in order to obtain other measurements necessary to the cooling strategy. 
     The cooling circuit control strategy can be implemented in the form of two modules A, B, as illustrated in  FIG. 2 . The module A relates to the regulation of the temperature of the coolant, whereas the module B relates to the choice of electric pump  2 ,  3 . 
     The module A is responsible for generating a coolant flow rate control according to the state of the vehicle (running or recharging the battery when stopped). The inputs of the module A are:
         the temperature T of the coolant: this can be obtained using one or more temperature sensors,   the temperature T ext  outside the vehicle, and   the speed V of the vehicle.       

     The inputs of the module B are:
         the flow rate control D com  from the module A, and   the state E of the vehicle: this is a signal originating from the central computer of the car which has the value 1 if the vehicle is in battery recharging mode and has the value 0 if the vehicle is in running mode.       

     The outputs of the module B are:
         the flow rate control D com1  for the first pump, used in running mode. This is a signal between 0 and 100 and expressing the percentage of the maximum flow rate that can be produced by the pump, and   the flow rate control D com2  of the second pump, used in recharging mode. This is a signal between 0 and 100 and expressing the percentage of the maximum flow rate that can be produced by the pump.       

     To put it simply, a choice can be made to use only the second pump if the vehicle state signal has the value 1 and to use only the first pump if the vehicle state signal has the value 0. 
     One embodiment of the flow rate control is illustrated in detail in  FIG. 3 . The objective is to automatically vary the flow rate control between a minimum flow rate value D min  and a maximum flow rate value D max , according to the temperature of the coolant. As long as the temperature of the coolant is below a setpoint temperature, the flow rate control remains at the minimum value D min . As soon as the temperature of the coolant exceeds the setpoint temperature, the flow rate control is obtained by closed-loop regulation, the setpoint concerned being the setpoint temperature, and the feedback loop concerned being the measured temperature of the coolant. 
     This objective is achieved by virtue of the blocks A 1  to A 6  of the module A. 
     The block A 1  generates the temperature setpoint value T cons  for the coolant according to the temperature T ext  outside the vehicle and the speed V of the vehicle. In fact, the greater the speed V of the vehicle, the greater the capacity of the radiator to cool, and therefore, the more possible it is to increase the temperature setpoint value T cons . Similarly, the colder the outside temperature T ext , the more effective the radiator becomes and therefore the more possible it is to increase the temperature setpoint value T cons . The block A 1  thus produces the temperature setpoint value T cons  by linear interpolation based on maps. 
     The block A 2  then generates an error signal ΔT which is the difference between the setpoint temperature T cons  and the measured temperature T. The signal ΔT is sent to the block A 3  which is a corrector block PI (proportional-integral), well known to those skilled in the art. It would also, however, be possible to use a corrector of proportional type or a corrector of integral type. 
     The inputs of the block A 3  are:
         the error signal ΔT from the block A 2 ,   the flow rate control D com  sent at the preceding sampling instant; if the control is saturated at the value D min  or at the value D max , the corrector is informed thereof and the integral action is in turn also saturated,   the proportional gain G of the corrector PI, for example 1%,   the integral time constant C t  of the corrector PI, for example 500 s.       

     The output of the block A 3  corresponds to the desired increase ΔD in flow rate relative to the minimum flow rate D min . This control should be saturated. 
     The block A 4  produces this saturation, between 0 (no desired flow rate increase) and D max -D min . This saturated control is then stored by the delay block A 5  which is used at the next sampling instant, to inform the corrector PI of any saturation. 
     Finally, the block A 6  produces the final flow rate control D comf . The final control D comf  is computed by adding to the value D min  the variation ΔD requested by the corrector PI. 
     The flow rate control is thus successfully made to change automatically between the two values D min  and D max . The value D min  may, for example, be set to 30% of the maximum flow rate that can be produced by the pump. It is in fact shrewd practice to retain a non-zero minimum flow rate D min  even if the temperature is low, to obtain a uniform temperature all along the circuit of the coolant and thus avoid the formation of hotspots. The value D max  may be set to 80% of the maximum flow rate, for example if there is a desire not to over-stress the pump. 
     The coolant flow rate control strategy is thus particularly simple to implement on a computer. It demands little computation time and makes it possible to reduce electrical consumption. 
     Although the device described above has two pumps, the invention may also relate to a device that has one or more than two pumps. It may also be applied to a petrol engine equipped with electric water pumps.