FR2905897A1 - THERMAL MANAGEMENT SYSTEM FOR THE AIR CONDITIONING AND ENGINE COOLING OF A MOTOR VEHICLE, COMPRISING IN PARTICULAR A GAS COOLER - Google Patents

Abstract

An engine coolant flows between a motor output (S) and a motor input (E) in a loop comprising an engine cooling radiator (24), a thermostat (26) controlling the flow of liquid in the radiator as a function of temperature, and a high temperature heat exchanger (E1). The exchanger comprises a hot circuit (44) traversed by a cooling fluid of an air conditioning circuit, in particular a CO2 air conditioning circuit and a cold circuit (38) through which the engine coolant passes. Means (46) regulate the supply of the cold circuit of the exchanger, to collect the coolant from the engine output when the engine is cold, and to collect the coolant from the radiator outlet when the engine is hot.

Description

1 Thermal management system for air conditioning and cooling

  The invention relates to air conditioning circuits for motor vehicles. It relates more particularly to air-conditioning circuits using as a cold source engine coolant. These include air conditioning circuits using a refrigerant such as carbon dioxide CO2 operating in the supercritical state, that is to say, where the fluid remains mostly at the same time. gaseous state in the air conditioning circuit. Such a circuit essentially comprises a compressor, a gas cooler, an internal heat exchanger, an expander, an evaporator and an accumulator. The gas cooler, which replaces the condenser of conventional air conditioning circuits, is arranged to cool the gaseous refrigerant by heat exchange with either the ambient air (air / gas type heat exchanger) or with the coolant of the engine (heat exchanger of water / gas type, also known as Water / Gas Cooler or WGC). It is to the circuits comprising this last type of exchanger that the invention relates. Such an air conditioning circuit where a gaseous refrigerant such as CO2 is cooled in a water / gas type heat exchanger 2905897 2 is described for example in FR-A-2,875,743 (Valeo Thermal Systems). It should be noted, however, that the present invention is not limited to air conditioning circuits using a refrigerant fluid operating in the supercritical state such as CO2, but that its teachings can also be applied to other types of refrigerants, for example. examples of fluorinated compounds commonly used such as HFC 134a, which are present in the circuit under two different phases, namely a gaseous phase and a liquid phase. The starting point of the invention lies in the observation that the use of a water / gas exchanger in such circuits does not make it possible to use all the potential of the exchanger in a certain number of operating cases. , especially when the engine is hot, which penalizes the efficiency of the air conditioning loop.

  The object of the invention is to solve this problem by proposing a new configuration of the air conditioning circuit which makes it possible to optimize the efficiency of the heat exchange between the coolant and the engine coolant when the latter is hot, without penalizing the temperature rise of the engine when it is cold. The thermal management system of the invention is of the type disclosed in particular by the aforementioned FR-A-2 875 743, that is to say comprising an engine cooling loop with: a motor comprising a motor input and an engine output for a motor engine coolant; an engine cooling radiator; and a high temperature heat exchanger allowing a heat exchange between a cooling fluid of the air conditioning circuit and the engine coolant.

In a characteristic manner of the invention, this thermal management system furthermore comprises means for regulating the supply of engine coolant to the heat exchanger as a function of the temperature, arranged to detect the coldest point. of said loop, and withdrawing the coolant from said coldest point. Thus, the heat exchanger is always fed with the coldest liquid in the engine cooling loop. Said coldest point may in particular be the engine output, in the cold engine condition, and the radiator output, in the hot engine condition.

This regulation makes it possible to make the best use of the potential of the water / gas heat exchanger, by coupling it: at the outlet of the engine when the latter is cold (which has the further advantageous consequence) of helping to the temperature rise of the engine and providing an additional heating possibility), and then at the radiator outlet once the engine is warm, so as to make the exchanger work with a coolant at a lower temperature.

The regulating means may in particular be means operating in response to the temperature of the coolant at the outlet of the engine.

The thermal management system of the invention is particularly suitable for air conditioning circuits where the refrigerant is a fluid operating in the supercritical state such as CO2, the heat exchanger then being a gas cooler for this purpose. refrigerant. But this application is not limiting, and the teachings of the invention are also applicable to air conditioning circuits using a refrigerant comprising a fluorinated compound, for example a HFC 134a type compound. Very advantageously, the engine cooling loop 15 further comprises a thermostat capable of selectively controlling the circulation of the cooling liquid in the radiator as a function of the temperature of this liquid, the circulation being authorized in a hot and prohibited engine condition. in a cold engine condition.

In a first embodiment, corresponding to a configuration in which the thermostat is arranged between the radiator outlet and the motor inlet: the outlet of the heat exchanger is connected to the engine inlet downstream of the thermostats. ; and the regulating means comprise a temperature-controlled feed selection member adapted to connect the inlet of the heat exchanger to either the engine outlet upstream of the radiator, in the cold engine condition, or to the radiator in downstream thereof, in the hot engine condition. In a simplified variant of this first embodiment: the output of the heat exchanger is connected to the motor input downstream of the thermostat; the inlet of the heat exchanger is connected to the radiator downstream thereof; and the regulating means comprise a temperature controlled flow control member, serially connected with the heat exchanger. In a second embodiment, corresponding to a configuration where the thermostat is disposed between the motor output and the radiator inlet: the output of the heat exchanger 10 is connected to the motor input; the inlet of the heat exchanger is connected both to the radiator downstream thereof and to a pipe connected to the motor output upstream of the thermostat; and the regulating means comprise a temperature controlled flow control member, connected in series in said pipe connected to the motor output. In a simplified variant of this second embodiment: the outlet of the heat exchanger is connected to the motor inlet; the inlet of the heat exchanger is connected to the radiator downstream thereof; and the regulating means comprises a temperature controlled flow control member, shunted on the thermostat.

An example embodiment of the thermal management system of the invention will now be described with reference to the appended drawings in which the same numerical references designate identical or functionally similar elements from one figure to the next. . Figure 1 is a diagram showing a motor vehicle air conditioning circuit traversed by a refrigerant fluid operating in the supercritical state, wherein the circuit is configured according to the prior art. FIG. 2 illustrates in more detail the implementation of the gas cooler of the diagram of FIG. 1 in the engine cooling loop, again according to the prior art. FIG. 3 illustrates a first embodiment of the engine / air-cooled water / gas exchanger cooling circuit according to the present invention. FIG. 4 illustrates a simplified variant of the circuit shown in FIG. 3. FIG. 5 illustrates a second embodiment of the engine / air conditioning cooling system with a water / gas exchanger according to the present invention.

FIG. 6 illustrates a simplified variant of the circuit shown in FIG. 5. FIGS. 1 and 2 illustrate a motor vehicle air conditioning circuit according to the prior art, of the type using a refrigerant fluid operating in the supercritical state such as the CO2, where the coolant temperature is lowered by heat exchange with the engine coolant.

The circuit essentially comprises a compressor 10, for example an externally controlled compressor controlled by a control electronics 12. The compressed refrigerant then flows through a gas cooler comprising one or more successive heat exchangers in the compressor. example shown three heat exchangers E1, E2 and E3 connected in series. At the outlet of the cooler 14, the fluid passes through an in-dull exchanger 16 and is then expanded in a pressure reducer 18, for example an expansion valve controlled also by the control electronics 12. The fluid thus expanded is driven to an exchanger 20 performing the same function as the evaporator of a conventional refrigerant phase change air conditioning circuit, then to an accumulator 22 and the internal exchanger 16, before being recycled to the compressor 10. The gas cooler 14 comprises for example, as illustrated in Figure 10, a series of three exchangers El, E2, E3 respectively operating at high temperature, low temperature and very low temperature. The high temperature is usually of the order of 80 to 100 C (typically 90 C), and the low temperature of the order of 50 to 70 C (typically 60 C). The very low temperature, meanwhile, is of the order of 30 to 60 C (typically 50 C) in the case of a water / gas exchanger using the engine coolant, or a temperature dependent on the ambient air in the case of an air / gas exchanger. The first exchanger E1 is a water / gas exchanger using as a cold source the engine coolant, generally water added with antifreeze (glycoated water) or similar liquid. The low temperature and very low temperature heat exchangers E2 and E3 can also use as coolant source the engine coolant, via a separate loop of the loop feeding the heat exchanger E1, or by contact with ambient air taken at the outside of the vehicle. In simplified embodiments, the third stage E3 of the cooler may be omitted.

In the remainder of the description, the implementation of the high-temperature heat exchanger E1 will be discussed, but it will be understood that the teachings of the invention are also applicable, as necessary, to another heat exchanger using as coolant source the engine coolant, when one seeks a configuration to optimize the heat exchange with the engine coolant.

The motor M is cooled by a circulating liquid loop, outside the engine, between an output S and an inlet E. This liquid is cooled by a motor cooling radiator 24, under the control of a thermostat 26 constituted of a temperature-controlled valve preventing or reducing the passage of the coolant in the radiator 24 until the engine has reached its full operating temperature, so as not to penalize the rise in temperature of the at startup. The engine coolant also feeds an engine oil cooler 28 and a heater 30 for optionally heating the pulsed air into the passenger compartment by heat exchange with the hot liquid from the engine.

The coolant is driven in motion outside the engine in the different loops by a circulating pump 32.

In the known embodiment, illustrated in FIG. 2, in addition to the motor cooling loop 34 including the radiator 24, the circuit includes a loop 36 including the heat exchanger E1, which is permanently supplied with the liquid. cooling directly from the engine output S, the liquid being at the engine temperature. More precisely, the cold circuit 38 of the exchanger E1 is connected via its inlet 40 to the output S of the engine, while its outlet 42 is connected to a point situated downstream of the radiator 24, so as to recycle to the The heat exchanger 44 circulates, for its part, is supplied by the gas to be cooled, which is then directed to the low temperature and very low temperature stages. E2 and E3. The configuration just described does not make it possible to use all the potential of the exchanger E1 in a certain number of operating cases, in particular when the engine is hot, which penalizes the efficiency of the engine. air conditioning loop. FIG. 3 illustrates a first embodiment of the invention making it possible to solve this problem by improving the efficiency of the heat exchange when the engine is hot, without penalizing the rise in temperature of the latter when it is hot. is cold. The configuration illustrated in this FIG. 3 corresponds to a case in which the thermostat 26 is disposed on the side of the engine inlet E, downstream of the radiator 24.

In this diagram, the inlet 40 of the cold circuit 38 of the exchanger E1 is connected to a regulating member 46, such as a temperature-controlled valve, for selectively coupling the inlet 40 of the heat exchanger. either at a first inlet 48 when the engine is cold, or at a second inlet 50 when the engine is hot. The output 42 of the cold circuit 38 is, in turn, connected to the engine inlet E at a point downstream of the thermostat 26, so as to allow the return of the liquid to the engine even when the thermostat is closed. The inlet 48 of the regulating member 46 is connected to the motor output S at a point situated upstream of the radiator 24, while the inlet 50 is connected to a point situated downstream of this same radiator 24. The selection of one or other of the inputs 48 or 50 may be progressive (in the case where the member 46 is for example a thermostat or a proportional valve), or abrupt (in the case where the member 46 is an all-or-nothing valve). The control of the valve as a function of temperature can be a control integrated into the valve, which changes the position of the latter as a function of the temperature of the liquid circulating inside. This control can also be an external command from a signal delivered by one or more external sensors or probes, placed at a suitable point of the coolant circuit; the control can then also take into account the outside temperature, in particular to take 30 differentiated actions depending on whether it is a starting situation of the engine in cold weather or hot weather.

When the coolant is cold, the regulator 46 selects the inlet 48, which has the effect of supplying the exchanger El with the liquid (cold) coming directly from the motor output M. The liquid reheated by the exchanger E1 is returned to the engine, which incidentally contributes to accelerating the rise in temperature thereof. Once the engine is warm, the regulator 46 selects the inlet 50, which has the effect of supplying the exchanger E1 with the liquid after the latter has been cooled by the radiator 24, therefore at a lower temperature than the output of the engine, thus improving the heat transfer in the heat exchanger El.

Thus, under all circumstances, the heat exchanger E1 is fed with the coldest liquid in the engine cooling loop, which provides maximum efficiency for the heat exchanger E1, and thus contributes all the more to improving the efficiency. overall air conditioning system. FIG. 4 illustrates a simplified variant of the circuit of FIG. 3, in which the regulator 52 is a temperature-controlled valve or similar element placed in series with the exchanger E1 in the loop circulating the liquid. The inlet 40 of the exchanger E1 is connected to a point situated downstream of the radiator 24 and upstream of the thermostat 26, while its outlet 42 is connected to the motor inlet E at a point situated downstream of the thermostat. 26.

With this configuration, the regulating member 52 makes it possible to force the passage of the coolant with a certain flow rate in the exchanger E 1 even when the thermostate 26 is closed or partially open, thus making it possible to improve the efficiency of the heat exchange in certain particular conditions, for example during summer starts (this configuration being less favorable than that of Figure 3 to a rapid rise in engine temperature, or the possibility of additional heating). FIG. 5 illustrates a second embodiment of the invention, corresponding to a configuration in which the thermostate 26 is disposed on the output side of the motor, that is to say upstream of the radiator 24. In this scheme, the heat exchanger E1 is arranged in series with the radiator 24 downstream thereof. More specifically, the inlet 40 of the heat exchanger E1 is connected firstly to the radiator 24 outlet, directly, and secondly to the motor output S via a pipe 54 including a regulating member 56 and connected to the engine output S upstream of the thermostat 26. The output 42 of the exchanger E1 is connected to the engine input E. The regulating device 56 is a thermostat or a controlled valve allowing regulating the flow in line 54 as a function of temperature, this flow rate being maximum when the temperature of the coolant is low, and minimal or zero when this temperature is high. When the engine is cold, the regulator 56 ensures a maximum flow in the pipe 54, so that the liquid coming from the motor outlet feeds the exchanger E1, which increases the efficiency of the latter and contributes furthermore at a rapid temperature rise of the engine. However, the coolant does not circulate in the radiator 24, because of the closing of the thermostat 26 (which avoids penalizing the temperature rise of the engine).

When the engine is hot, the flow in line 54 is gradually reduced (in the case of a thermostat or a proportional valve) or stops abruptly (in the case of an "all or nothing" valve). The exchanger E1 will then be fed with the coolant leaving the radiator, therefore at a lower temperature than that of the hot coolant leaving the engine, thus improving the efficiency of the air conditioning circuit. FIG. 6 illustrates a simplified variant of the circuit of FIG. 5. In this simplified variant, the pipe 54 supplying the exchanger E1 is omitted and replaced by a bypass 60 on the thermostat 26, this branch comprising the regulating member 58. The latter allows under certain conditions, for example during cold starts in summer, to force with a reduced flow the passage of the liquid in the radiator 24, and consequently in the exchanger El. In this variant, it will be noted that the thermostat 26 and the regulating member 58, which is for example a temperature-controlled valve, can be integrated in one and the same functional block 62 making it possible to control the de-bit in the branch 34 including the radiator 24 to take into account the presence of the exchanger E1 downstream of the radiator 24.

Claims (10)

claims   1. Thermal management system, in particular for a motor vehicle air-conditioning circuit, comprising an engine cooling loop, the loop comprising: a motor (M), said motor comprising an engine input (E) and an engine output (S) for an engine cooling liquid, an engine cooling radiator (24), and a high temperature heat exchanger (E1) allowing a heat exchange between a cooling fluid of the air conditioning circuit and the cooling liquid. characterized in that it further comprises: means (46; 52; 56; 58) for regulating the engine coolant supply of the heat exchanger (E1) as a function of the temperature, arranged to: • detect the coldest point of said loop, and collect the coolant from said coldest point.   2. Thermal management system according to claim 1, characterized in that said coldest point is: the engine output, in the cold engine condition, and the radiator output, in the hot engine condition.   3. Thermal management system according to one of claims 1 and 2, characterized in that the regulating means (46; 52; 56; 58) are means operable in response to the temperature of the cooling liquid. motor output.   4. Thermal management system according to one of claims 1 to 3, characterized in that the refrigerant is a fluid operating in the supercritical state, preferably CO2, and the heat exchanger is a cooler. gas for this coolant. 10   5. Thermal management system according to one of claims 1 to 3, characterized in that the refrigerant comprises a fluorinated compound, preferably a compound of HFC 134a type. 15   6. Thermal management system according to one of claims 1 to 5, characterized in that the engine cooling loop further comprises a thermostat (26) adapted to selectively control the circulation of the coolant in the radiator according to the temperature of this liquid, the circulation being allowed in a hot engine condition and prohibited in a cold engine condition.   7. Thermal management system according to claim 6, characterized in that, the thermostat (26) being disposed between the radiator outlet (24) and the motor inlet (E). the outlet (42) of the heat exchanger (E1) is connected to the motor inlet (E) downstream of the thermostat, and the control means comprises a power supply selector (46) controlled in temperature, suitable for connecting the inlet (40) of the heat exchanger: either to the engine outlet (S) upstream of the radiator, in the cold engine condition; or to the radiator (24) downstream thereof, in the hot engine condition.   8. Thermal management system according to claim 6, characterized in that the thermostat (26) is disposed between the radiator outlet (24) and the motor inlet (E). the outlet (42) of the heat exchanger (El) is connected to the motor inlet (E) downstream of the thermostat, where the inlet (40) of the heat exchanger is connected to the radiator (24); ) downstream thereof, and the regulating means comprises a temperature-controlled flow control member (52) connected in series with the heat exchanger (El). 15   Thermal management system according to claim 6, characterized in that, the thermostat (26) being arranged between the motor output (S) and the radiator inlet (24): the outlet (42) of the exchanger of heat is connected to the motor inlet (E), the inlet (40) of the heat exchanger is connected both to the radiator (24) downstream thereof and to a connected pipe (54). at the motor output (S) upstream of the thermostat, and the regulating means comprise a temperature controlled flow control member (56) connected in series in said conduit connected to the motor output.   10. Thermal management system according to claim 6, characterized in that, the thermostat (26) being arranged in-30 is the motor output (S) and the inlet of the radiator (24). the outlet (42) of the heat exchanger is connected to the motor inlet (E), where the inlet (40) of the heat exchanger is connected to the radiator (24) downstream of the heat exchanger and the regulating means comprise a temperature controlled flow control member (58) which is bypassed to the thermostat.