FR3070316B1 - INDIRECT INDIRECT AIR CONDITIONING CIRCUIT FOR A MOTOR VEHICLE AND METHOD FOR MANAGING THE SAME - Google Patents

Abstract

The present invention relates to a method for managing an invertible indirect air-conditioning circuit (1) for a motor vehicle comprising a first refrigerant fluid loop (A) in which a refrigerant circulates and comprising a first bifluid heat exchanger (5) arranged together on the first coolant loop (A) and on a second heat transfer fluid loop (B) in which a first heat transfer fluid circulates, the first heat transfer fluid loop (A) comprising a bypass line (80) comprising a second two-fluid heat exchanger (83) for exchanging heat between the refrigerant and a second heat transfer fluid, when the indirect cooling circuit (1) is in a dedicated cooling mode of the second heat transfer fluid in which the refrigerant passes through the pipe bypass (80), a central control unit (90) redirects the refrigerant fluid so that: • if the pressure measured at the pressure sensor (71) of the refrigerant at the outlet of the first bifluid heat exchanger (5) is lower than the limit pressure value, the refrigerant redirection device prevents the passage of the cooling fluid in the bypass loop (30), • if the pressure measured at the pressure sensor (71) of the refrigerant at the outlet of the first bifluid heat exchanger (5) is greater than or equal to a value of pressure limit, the coolant redirection device allows the passage of refrigerant in the bypass loop (30).

Description

The invention relates to the field of motor vehicles and more particularly to a motor vehicle air conditioning circuit and its management method.

Today's motor vehicles are increasingly equipped with an air conditioning system. Generally, in a "conventional" air conditioning circuit, a refrigerant fluid passes successively in a compressor, a first heat exchanger, called a condenser, placed in contact with an air flow outside the motor vehicle to release heat, a device and a second heat exchanger, called evaporator, placed in contact with a flow of air inside the motor vehicle to cool it.

There are also more complex air conditioning circuit architectures that make it possible to obtain an invertible air-conditioning circuit, that is to say that it can use a heat pump operating mode in which it is able to absorb heat. heat energy in the outside air at the first heat exchanger, then called evapo-condenser, and restore it in the passenger compartment including a third dedicated heat exchanger.

This is possible in particular by using an indirect cooling circuit. Indirect means here that the air conditioning circuit comprises two circulation loops of two separate fluids (for example a refrigerant fluid on the one hand and glycol water on the other hand) in order to perform the various heat exchanges.

The air conditioning circuit thus comprises a first refrigerant fluid loop in which a cooling fluid circulates, a second heat transfer fluid loop in which a first coolant circulates, and a first two-fluid heat exchanger arranged jointly on the first refrigerant loop and on the second heat transfer fluid loop, so as to allow the exchange of heat between said loops.

The air conditioning circuit may also include a bypass line comprising an expansion device and a second bifluid heat exchanger. This second bifluid heat exchanger makes it possible in particular to cool a second coolant circulating in another circulation loop. This circulation loop and this second heat transfer fluid can for example be used for cooling the batteries of an electric or hybrid motor vehicle.

However, in the case where the air conditioning circuit is in an operating mode where it only cool this second heat transfer fluid, the refrigerant can reach a high pressure, especially at the evaporator. This high pressure can cause deterioration of the evaporator.

One of the aims of the present invention is therefore to at least partially overcome the disadvantages of the prior art and to provide a method for managing an improved invertible cooling circuit, in particular during a dedicated cooling mode of the second heat transfer fluid.

The present invention therefore relates to a method for managing an invertible indirect air-conditioning circuit for a motor vehicle comprising a first refrigerant loop in which a refrigerant circulates and comprising a first two-fluid heat exchanger arranged jointly on the first refrigerant loop. and on a second heat transfer fluid loop in which a first heat transfer fluid circulates, the first two-fluid heat exchanger being arranged so as to allow exchanges of heat between the first refrigerant loop and the second heat transfer fluid loop, the first loop heat transfer fluid comprising: • a compressor, • the first two-fluid heat exchanger, disposed downstream of said compressor, • a first expansion device allowing constant passage of refrigerant, • a first heat exchanger being intended to be traversed by a air flow inside the motor vehicle, • a second expansion device, • a second heat exchanger to be traversed by a flow of air outside the motor vehicle, and • a bypass loop of the second heat exchanger, A device for redirecting the refrigerant fluid from the first heat exchanger to the second heat exchanger or to the bypass loop, a bypass line connected firstly between the first two-fluid heat exchanger and the first heat exchanger; expansion and secondly between the output of the bypass loop and the compressor, said bypass line comprising a third expansion device disposed upstream of a second bifluid heat exchanger for heat exchanges between the refrigerant and a second heat transfer fluid, said circuit comprising a refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger, the indirect reversible air conditioning circuit comprising a central control unit connected to said refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger and adapted to drive the first coolant redirection device when the indirect cooling circuit is in a dedicated cooling mode of the second heat transfer fluid in which the refrigerant fluid passes through the bypass pipe and does not pass through the second heat exchanger, the central control unit controls the redirection device of the refrigerant so that: • if the pressure measured at the refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger is less than the limit pressure value, the refrigerant redirection device prevents the passage of the cooling fluid in the loop of c bypassing, • if the pressure measured at the refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger is greater than or equal to a limit pressure value, the device for redirecting the refrigerant fluid allows the refrigerant to pass through the refrigerant. bypass loop.

According to one aspect of the invention, the third expansion device is an electronic expansion valve controlled by the central control unit and when the refrigerant passes through the bypass loop, the opening of the third expansion device is controlled so that the refrigerant fluid at the inlet of the compressor reaches a target superheat value.

According to another aspect of the invention, if the target overheating value of the refrigerant at the inlet of the compressor can not be reached, the opening of the third expansion device is controlled to be at its minimum.

According to one aspect of the invention, the target superheat is between 5 and 22 ° C.

According to one aspect of the invention, the central control unit regulates the speed of the compressor so that the pressure of the coolant at the outlet of the first heat exchanger reaches a target value, said target value of the refrigerant pressure being calculated as a function of a target temperature of a second heat transfer fluid at the outlet of the second bifluid heat exchanger.

According to one aspect of the invention, the refrigerant fluid is selected from R1234yf and R134a.

According to one aspect of the invention, the limit pressure value of the refrigerant at the outlet of the first two-fluid heat exchanger is between 10 and 15 bar.

The present invention also relates to a reversible indirect air-conditioning circuit for a motor vehicle comprising a first refrigerant fluid loop in which a refrigerant circulates and comprising a first two-fluid heat exchanger arranged jointly on the first refrigerant loop and on a second refrigerant loop. heat transfer fluid in which a first heat transfer fluid circulates, the first bifluid heat exchanger being arranged so as to allow exchanges of heat between the first refrigerant loop and the second heat transfer fluid loop, the first heat transfer fluid loop comprising: a compressor, • the first bifluid heat exchanger, arranged downstream of said compressor, • a first expansion device allowing a constant flow of refrigerant fluid, • a first heat exchanger being intended to be traversed by an internal air flow to the motor vehicle, • a second expansion device, • a second heat exchanger to be traversed by a flow of air outside the motor vehicle, and • a bypass loop of the second heat exchanger, • a redirection device refrigerant fluid from the first heat exchanger to the second heat exchanger or to the bypass loop, • a bypass line connected on the one hand between the first two-fluid heat exchanger and the first expansion device and other between the output of the bypass loop and the compressor, said bypass line comprising a third expansion device disposed upstream of a second bifluid heat exchanger allowing the exchange of heat between the refrigerant and a second heat transfer fluid, said circuit comprising a refrigerant pressure sensor at the outlet of the The first indirect heat exchanger circuit comprises a central control unit connected to said refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger and able to control the first coolant redirection device, when the cooling circuit is connected to said refrigerant pressure sensor. indirect cooling is in a dedicated cooling mode of the second coolant in which the coolant flows through the bypass line and does not pass through the second heat exchanger, the central control unit is configured to control the coolant redirection device so that: • if the pressure measured at the refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger is less than the limit pressure value, the refrigerant redirection device prevents the passage of the refrigerant into the refrigerant. co loop ntournement, • if the pressure measured at the level of the refrigerant pressure sensor at the outlet of the first two-fluid heat exchanger is greater than or equal to a limit pressure value, the device for redirecting the refrigerant fluid allows the refrigerant to pass through the refrigerant. bypass loop. Other features and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and nonlimiting example, and the appended drawings in which: FIG. 1 shows a schematic representation of a circuit indirect flow of air conditioning, FIG. 2 shows a schematic representation of the second heat transfer fluid loop of the indirect invertible air conditioning circuit of FIG. 1, according to an alternative embodiment, FIG. 3 shows a schematic representation of a heating device. , Figure 4 shows a schematic representation of an indirect invertible air conditioning circuit of Figure 1 in a cooling operation mode of the second heat transfer fluid, Figure 5 shows a schematic representation of a circuit of indirect reversible air conditioning of Figure 1 in a variant of the mode of the cooling operation of the second heat transfer fluid, FIG. 6 shows a diagram of the evolution of certain parameters of the indirect reversible air conditioning circuit as a function of time in the cooling mode of the second heat transfer fluid of FIGS. 4 and 5.

In the different figures, the identical elements bear the same reference numbers.

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments may also be combined and / or interchanged to provide other embodiments.

In the present description, it is possible to index certain elements or parameters, for example first element or second element as well as first parameter and second parameter or else first criterion and second criterion, etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria close but not identical. This indexing does not imply a priority of one element, parameter or criterion with respect to another, and it is easy to interchange such denominations without departing from the scope of the present description. This indexing does not imply either an order in time for example to appreciate this or that criterion.

In the present description, the term "placed upstream" means that one element is placed before another relative to the direction of flow of a fluid. Conversely, "downstream" means that one element is placed after another relative to the direction of fluid flow.

Figure 1 shows an indirect air conditioning circuit 1 for a motor vehicle. This indirect air conditioning circuit 1 comprises in particular: a first refrigerant fluid loop A in which a refrigerant circulates, for example R1234yf, R134a or any other refrigerant adapted to the application, a second loop of coolant B in which circulates a heat transfer fluid, and • a first bifluid heat exchanger 5 arranged jointly on the first coolant loop A and on the second heat transfer fluid loop B, so as to allow exchanges of heat between said first fluid loop refrigerant A and said second heat transfer fluid loop B.

The first refrigerant fluid loop A more particularly comprises, in the refrigerant circulation direction: a compressor 3, the first bifluid heat exchanger 5, disposed downstream of said compressor 3, a first expansion device 7, a first heat exchanger 9 being intended to be traversed by an interior air flow 100 to the motor vehicle, a second expansion device 11, a second heat exchanger 13 to be traversed by an outside air flow 200 to the motor vehicle, and ° a bypass loop 30 of the second heat exchanger 13.

The bypass loop 30 can more specifically connect a first connection point 31 and a second connection point 32.

The first connection point 31 is preferably arranged, in the flow direction of the refrigerant, downstream of the first heat exchanger 9, between said first heat exchanger 9 and the second heat exchanger 13. More particularly, and as illustrated in FIG. 1, the first connection point 31 is arranged between the first heat exchanger 9 and the second expansion device 11. It is however quite possible to imagine that the first connection point 31 is arranged between the second expansion device 11 and the second heat exchanger 13 as long as the refrigerant has the possibility of bypassing said second expansion device 11 or to pass through without suffering pressure loss.

The second connection point 32 is, for its part, preferably located downstream of the second heat exchanger 13, between said heat exchanger 13 and the compressor 3.

In order to control the passage of the cooling fluid within the bypass loop 30 or not, the indirect air conditioning circuit 1 comprises a device for redirecting the refrigerant fluid from the first heat exchanger 9 to said bypass loop 30 or towards the second heat exchanger 13. This device for redirecting the refrigerant may include in particular a first stop valve 33 disposed on the bypass loop 30. This first stop valve 33 may be an all-or-nothing valve or still a proportional valve whose opening amplitude is controlled. In order for the refrigerating fluid not to pass through the second heat exchanger 13, the second expansion device 11 may in particular comprise a stop function, that is to say that it is capable of blocking the flow of refrigerant when 'it is closed. An alternative may be to have a stop valve between the second expansion device 11 and the first connection point 31.

Another alternative (not shown) may also be to have a three-way valve at the first connection point 31.

The first refrigerant fluid loop A may also comprise a non-return valve 23 disposed downstream of the second heat exchanger 13, between said second heat exchanger 13 and the second connection point 32 in order to prevent refrigerant fluid from the first bypass loop 30 does not flow back to the second heat exchanger 13.

By stop valve, check valve, three-way valve or expansion device with stop function, here means mechanical or electromechanical elements that can be controlled by an electronic control unit on board the motor vehicle.

The first refrigerant fluid loop A may also comprise a first internal heat exchanger (not shown) allowing a heat exchange between the high-pressure refrigerant fluid at the outlet of the first two-fluid heat exchanger 5 and the low-pressure refrigerant fluid at the outlet the first heat exchanger 13 or the bypass loop 30. This first internal heat exchanger comprises in particular a low pressure refrigerant inlet and outlet from the second connection point 32, as well as an inlet and an outlet high pressure refrigerant fluid from the first bifluid heat exchanger 5.

By high pressure refrigerant fluid is meant by a refrigerant fluid having undergone an increase in pressure at the compressor 3 and has not yet suffered pressure loss due to one of the expansion devices. By coolant fluid at low pressure is meant by a coolant having undergone a loss of pressure and at a pressure close to that at the inlet of the compressor 3.

The first refrigerant fluid loop A may furthermore also comprise a second internal heat exchanger (not shown) permitting a heat exchange between the high-pressure refrigerant at the outlet of the first internal heat exchanger and the circulating low-pressure refrigerant fluid. in the bypass loop 30. This second internal heat exchanger notably comprises a low-pressure refrigerant inlet and outlet from the first connection point 31, as well as a high-pressure refrigerant inlet and outlet. from the first internal heat exchanger. As illustrated in FIG. 1, the second internal heat exchanger may be disposed downstream of the first stop valve 33.

At least one of the first or second internal heat exchangers may be a coaxial heat exchanger, that is to say comprising two coaxial tubes and between which heat exchanges take place.

Preferably, the first internal heat exchanger may be a coaxial internal heat exchanger with a length of between 50 and 120 mm, whereas the second internal heat exchanger may be a coaxial internal heat exchanger with a length of between 200 and 700mm.

The first coolant loop A may also comprise a desiccant bottle 14 disposed downstream of the first bifluid heat exchanger 5, more precisely between said first bifluid heat exchanger 5 and the first expansion device 7. Such a desiccant bottle 14 disposed on the high pressure side of the air conditioning circuit, that is to say downstream of the two-fluid heat exchanger 5 and upstream of an expansion device, has a smaller footprint and a reduced cost compared to other phase separation solutions such as an accumulator which would be disposed on the low pressure side of the air conditioning circuit, that is to say upstream of the compressor 3, in particular upstream of the first internal heat exchanger.

The first refrigerant fluid loop A also comprises a bypass line 80 of the first expansion device 7 and the first heat exchanger 9. This bypass line 80 comprises a third expansion device 12 arranged upstream of a second heat exchanger 83. This second bifluid heat exchanger 83 is also arranged jointly on a secondary thermal management loop. The secondary thermal management loop may more particularly be a loop in which circulates a second heat transfer fluid and connected to heat exchangers or cold plates at batteries and / or electronic elements.

The bypass line 80 is connected on the one hand upstream of the first expansion device 7. This connection is made at a first junction point 81 disposed upstream of the first expansion device 7, between the first heat exchanger bifluid 5 and said first expansion device 7.

The bypass line 80 is connected on the other hand at a second junction point 82 disposed upstream of the compressor 3, between the third heat exchanger 13 and said compressor 3. In FIG. 1, the second junction point 82 is disposed between the second connection point 32 of the bypass loop 30 and the compressor 3. However, it is quite possible to imagine other embodiments for example on the bypass loop 30 downstream of the first shutoff valve 33.

The first 7 and second 11 expansion devices may be electronic expansion valves, that is to say the pressure of the refrigerant output fluid is controlled by an actuator which fixes the opening section of the expansion device, thereby fixing the fluid pressure at the outlet. Such an electronic expansion valve is particularly adapted to let the refrigerant fluid without loss of pressure when said expansion device is fully open.

These expansion devices can thus be electronic expansion valves controllable by a central control unit 90 integrated into the vehicle.

More particularly, the first expansion device 7 is an expansion valve permitting constant passage of refrigerant fluid. By this it is meant that it has no stop function and that even at its lowest opening, it passes a flow of refrigerant fluid.

The third expansion device 12 may have a stop function in order to allow the refrigerant to pass through the bypass line 80. An alternative is to have a stop valve on the bypass line 80, upstream of the third expansion device 12. This third expansion device 12 may be an electronic expansion valve controlled by the central control unit 90 or a thermostatic expansion valve or a tube orifice.

According to a variant not shown, the first refrigerant fluid loop A may also comprise a first internal heat exchanger (IHX for "internai heat exchanger") allowing a heat exchange between the refrigerant at the outlet of the bifluid heat exchanger 5 and the refrigerant at the outlet of the second heat exchanger 13 or the bypass line 30. This first internal heat exchanger comprises in particular an inlet and a coolant outlet from the second connection point 32, and an inlet and a coolant outlet from the bifluid heat exchanger 5.

The first refrigerant fluid loop A may comprise, in addition to the first internal heat exchanger, a second internal heat exchanger allowing a heat exchange between the high-pressure refrigerant at the outlet of the first internal heat exchanger and the refrigerant fluid at the outlet. low pressure circulating in the bypass line 30, that is to say from the first connection point 31. By high pressure refrigerant fluid is meant by a refrigerant fluid having undergone an increase in pressure at the compressor 3 and that it has not yet undergone a loss of pressure because of the electronic expansion valve 7 or the tube orifice 11. This second internal heat exchanger notably comprises an inlet and a coolant outlet coming from the first connection point 31, as well as a high-pressure refrigerant inlet and outlet from the first internal heat exchanger.

At least one of the first or second internal heat exchanger may be a coaxial heat exchanger, that is to say having two coaxial tubes and between which the heat exchange takes place.

Preferably, the first internal heat exchanger may be a coaxial internal heat exchanger with a length of between 50 and 120 mm, whereas the second internal heat exchanger may be a coaxial internal heat exchanger with a length of between 200 and 700mm.

The second heat transfer fluid loop B may comprise: the first bifluid heat exchanger 5, a first circulation pipe 50 of the first heat transfer fluid comprising an internal radiator 54 intended to be traversed by an internal air flow 100 to the motor vehicle, and connecting a first connection point 61 disposed downstream of the first bifluid heat exchanger 5 and a second connection point 62 arranged upstream of said first two-fluid heat exchanger 5, a second circulation line 60 of the first fluid coolant having an external radiator 64 to be traversed by an external air flow 200 to the motor vehicle, and connecting the first connection point 61 disposed downstream of the first bifluid heat exchanger 5 and the second connection point 62 arranged upstream said first bifluid heat exchanger 5, and a pump 17 disposed downstream or upstream of the first Bifluid heat exchanger 5, between the first connection point 61 and the second connection point 62.

The indirect reversible air conditioning circuit 1 comprises, within the second heat transfer fluid loop B, a device for redirecting the first heat transfer fluid from the first bifluid heat exchanger 5 to the first circulation pipe 50 and / or to the second heat pipe. circulation 60.

As illustrated in FIG. 1, said device for redirecting the first heat transfer fluid from the first bifluid heat exchanger 5 can in particular comprise a second stop valve 63 arranged on the second circulation pipe 60 in order to block or not the first fluid. coolant and prevent it from circulating in said second circulation pipe 60.

This embodiment makes it possible in particular to limit the number of valves on the second heat transfer fluid loop B and thus makes it possible to limit production costs.

According to an alternative embodiment illustrated in FIG. 2, representing the second heat transfer fluid loop B, the device for redirecting the first heat transfer fluid from the first bifluid heat exchanger 5 may notably comprise a second stop valve 63 arranged on the second circulation line 60 to block or not the first heat transfer fluid and to prevent it from circulating in said second circulation line 60, and • a third stop valve 53 disposed on the first flow line 50 so to block or not the first heat transfer fluid and prevent it from circulating in said first circulation pipe 50.

The second heat transfer fluid loop B may also include an electric heating element 55 of the first heat transfer fluid. Said electric heating element 55 is in particular arranged, in the flow direction of the first heat transfer fluid, downstream of the first bifluid heat exchanger 5, between said first bifluid heat exchanger 5 and the first junction point 61.

The internal radiator 54 and the first heat exchanger 9 are more particularly disposed within a heating, ventilation and / or air conditioning device 40. As illustrated in FIG. 3, the heating, ventilation and / or air conditioning device 40 may comprise a supply line 41a outside air and a supply line 41b recirculated air (that is to say that comes from the passenger compartment). These two supply lines 41a and 41b both bring air to the first heat exchanger 9 so that it passes through. In order to choose where the air passing through the first heat exchanger 9 comes from, the heating, ventilation and / or air conditioning device 40 comprises a shutter 410a, for example a drum-type shutter, able to completely close or partially supply line 41a outside air or supply line 41b recirculated air.

Within it, the heating, ventilation and / or air conditioning device 40 comprises a heating pipe 42a which makes it possible to supply air having passed through the first heat exchanger 9, at the level of the internal radiator 54 so that it the crossbar and is heated before arriving in a distribution chamber 43. This heating pipe 42a also comprises a shutter 420a shutter able to close completely or partially.

The heating, ventilation and / or air conditioning device 40 may also comprise a bypass line 42b of the external radiator 54. This bypass line 42b allows the air passed through the first heat exchanger 9 to go directly into the distribution chamber 43, without passing through the internal radiator 54. This bypass 42b also comprises a shutter 420b shutter able to close completely or partially.

At the distribution chamber 43 the air can be sent to the windshield by an upper line 44a, the dashboard of the cabin through a median pipe 44b and / or down the dashboard of the passenger compartment. cockpit by a lower pipe 44c. Each of these conduits 44a, 44b, 44c having a shutter 440 capable of closing completely or partially.

The heating, ventilation and / or air conditioning device 40 also comprises a blower 46 in order to propel the internal air flow 100. This blower 46 may be arranged upstream of the first heat exchanger 9 according to the flow direction of the flow of air. indoor air 100.

As illustrated in FIG. 1, the indirect reversible air conditioning circuit 1 comprises a central control unit 90 enabling it to switch from one mode of operation to another. The central control unit 90 is in particular connected to a temperature sensor 72 of the first heat transfer fluid disposed downstream of the first bifluid heat exchanger 5 and is able to control the first shut-off valve 33. For this, the central unit control 90 is connected to the coolant redirection device. If said coolant redirection device comprises a first stop valve 33, the central control unit 90 controls its opening and closing and its opening amplitude if it is a progressive valve. The central control unit 90 may also be able to control the redirection device of the first heat transfer fluid. For this, the central control unit 90 is also connected to the second stop valve 63 and controls its opening and closing. The central control unit 90 can also be connected to the compressor 3 in order to control the speed of the latter. The central control unit 90 can also be connected to the various expansion devices 7, 11 and 12, in order to control their opening and thus define the pressure loss that the refrigerant undergoes when passing through them, to check whether they can be crossed. without loss of pressure or if they block the flow of refrigerant. The central control unit 90 can also be connected to different sensors measuring different parameters of the refrigerant or a secondary heat transfer fluid. By secondary coolant means here a heat transfer fluid which exchange heat energy with the refrigerant. This may especially be the first heat transfer fluid, the second heat transfer fluid or the internal air flow 100. These sensors may be for example: • a pressure sensor 71 at the outlet of the first bifluid heat exchanger 5, more precisely between the desiccant bottle 14 and the first junction point 81 • a temperature sensor 73 of the internal air flow 100 at the outlet of the first heat exchanger 9, • a temperature sensor 74 of the outside air, • a sensor of pressure and temperature 75 at the inlet of the compressor 3 and • a temperature sensor 76 of the second heat transfer fluid within the secondary thermal management loop at the outlet of the second bifluid heat exchanger 83, and • a pressure sensor coming out of the first heat exchanger 9.

The indirect invertible air conditioning circuit 1 described above can operate according to different modes of operation, in particular a dedicated cooling mode of the second heat transfer fluid at the level of the second bifluid heat exchanger 83, illustrated in FIG.

In this dedicated cooling mode of the second heat transfer fluid, the refrigerant flows through the bypass line 80 and does not pass through the second heat exchanger 13.

More specifically, the refrigerant successively passes into: • the compressor 3 at which it undergoes a pressure increase, • the first bifluid heat exchanger 5 at which the coolant transfers heat energy to the first heat transfer fluid in the second loop of coolant B, • the third expansion device 12 at which the refrigerant undergoes a loss of pressure, • the second bifluid heat exchanger 83 at which the refrigerant absorbs heat energy of the second heat transfer fluid , cooling it before joining the compressor 3.

In this dedicated cooling mode of the second heat transfer fluid, the coolant redirection device ensures that the refrigerant does not circulate in the bypass loop 30, for example by closing the first stop valve 33. the device for redirecting the refrigerant fluid ensures that the refrigerant does not circulate in the second expansion device 11 and the second heat exchanger 13. For this, the second expansion device 11 is completely closed if it has a stop function or a stop valve arranged upstream of said second expansion device 11 is closed.

The first expansion device 7 is in turn closed at its maximum in order to let as little refrigerant as possible into the first heat exchanger 9. The internal air flow 100 is also stopped to prevent heat exchange at the level of the heat exchanger. first heat exchanger 9.

At the level of the second heat transfer fluid loop B, the heat transfer fluid releases the heat energy recovered at the first bifluid heat exchanger 5 into the outside air flow 200 at the external radiator 64. For this, the second valve stop 63 is open. The heat transfer fluid does not exchange heat with the internal air flow 100. For this, the third stop valve 53 (visible in Figure 2) is closed if it is present or the internal air flow 100 bypasses the internal radiator 54 within the heating, ventilation and / or air conditioning device 40.

The present invention relates to a method for managing the indirect reversible air conditioning circuit 1 when it operates in this dedicated cooling mode of the second heat transfer fluid.

In this management method, the central control unit 90 controls the redirection device of the refrigerant fluid so that: • if the pressure measured at the pressure sensor 71 of the refrigerant at the outlet of the first bifluid heat exchanger 5 is less than the limit pressure value, the coolant redirection device prevents the passage of the refrigerant in the bypass loop 30, as shown in Figure 4, • if the pressure measured at the pressure sensor 71 of the coolant at the outlet of the first bifluid heat exchanger 5 is greater than or equal to a limit pressure value, the device for redirecting the refrigerant fluid allows the refrigerant to pass through the bypass loop 30, as illustrated in FIG. 5.

In order for the refrigerant to pass through the bypass loop 30, the central control unit 90 opens more particularly the first stop valve 33.

While a portion of the refrigerant fluid passes through the bypass loop 30, another portion of the refrigerant fluid continues to flow into the bypass line 80.

The fact of passing the refrigerant in the bypass loop 30 makes it possible to reduce the pressure of the refrigerant at the level of the first heat exchanger 9. In fact, because the first expansion device 7 passes refrigerant, the pressure at the first heat exchanger 9 increases and may exceed a limit pressure beyond which the first heat exchanger 9 may be damaged. For example, the pressure at which the first heat exchanger 9 begins to deteriorate may be of the order of 30 bars. With a factor of safety factor 2, the limit pressure beyond which the heat transfer fluid passes in the bypass loop 30 is between 10 and 15 bar.

When the refrigerant passes through the bypass loop 80, the opening of the third expansion device 12 is controlled so that the refrigerant fluid at the inlet of the compressor 3 reaches a target superheat value, for example between 5 and 22 ° C. .

If the target superheat value of the refrigerant at the inlet of the compressor 3 can not be reached, the opening of the third expansion device 12 is controlled to be at its minimum.

According to this management method, the central control unit 90 can also regulate the speed of the compressor 3 so that the pressure of the refrigerant measured by the pressure sensor 77 at the outlet of the first heat exchanger 9 reaches a target value. This target value of the refrigerant pressure is more particularly calculated as a function of a target temperature of the second heat transfer fluid at the outlet of the second bifluid heat exchanger 83. This target temperature of the second heat transfer fluid can be, for example, a target temperature in order to cool the batteries of an electric or hybrid vehicle.

The diagram of FIG. 6 shows the variation of various parameters of the indirect reversible air-conditioning circuit 1 as a function of time during its operation in the dedicated cooling mode of the second heat-transfer fluid and whether or not the refrigerant fluid passes through the loop. The experimental parameters of this diagram are the following: • a second two-fluid heat exchanger 83 delivering a thermal power of 2 kW to the cooling fluid, • an external temperature illustrated by the curve T74 passing from 45 to 25 ° C, The refrigerant used in the first refrigerant loop A is R1234yf.

The curve Pcomp_out corresponds to the evolution of the refrigerant pressure at the outlet of the compressor 3.

The curve P9_out corresponds to the evolution of the pressure of the refrigerant at the outlet of the first heat exchanger 9.

The curve T76 corresponds to the evolution of the temperature of the second heat transfer fluid at the outlet of the second bifluid heat exchanger 83.

The curve EXV7 corresponds to the evolution of the opening of the first expansion device 7, expressed in pulses / 100.

In the interval 20 to 80 min, a portion of the coolant flows into the bypass loop 30, the first stop valve 33 is opened. Curve P9_out then shows that the pressure is relatively constant at a relatively low value, for example less than 6 bar. The temperature of the second heat transfer fluid at the outlet of the second bifluid heat exchanger 83 shown by curve T76 is for its part at a value of about 25 ° C plus or minus 2 ° C.

The curve EXV7 shows that in this interval, the first expansion device 7 has the lowest possible opening.

In the range of 80 to 103 min, the coolant does not pass through the bypass loop 30, the first stop valve 33 is closed. The curve P9_out shows a sudden rise in the pressure of the refrigerant at the outlet of the first heat exchanger 9. The pressure of the refrigerant at the outlet of the first heat exchanger 9 thus meets the pressure of the refrigerant at the outlet of the compressor 3. the curves P9_out and Pcomp_out join at a value between 18 and 11 bar during this interval.

The temperature of the second heat transfer fluid at the outlet of the second bifluid heat exchanger 83 shown by the curve T76 remains for its value at about 25 ° C plus or minus 2 ° C.

In this interval, the curve EXV7 shows that the first expansion device 7 has the smallest possible opening although greater than its opening during the interval of 80 to 103 min.

In the interval 103 to 110 min, the first shut-off valve 33 is reopened and a part of the refrigerant fluid passes into the bypass loop 30. The curve P9_out then shows that the pressure returns to a rather low value, by example less than 6 bar. The temperature of the second heat transfer fluid at the outlet of the second bifluid heat exchanger 83 shown by the curve T76 is for its part always at a value of the order of 25 ° C plus or minus 2 ° C.

The curve EXV7 shows that in this interval, the first expansion device 7 returns to the lowest possible opening.

The passage of a portion of the refrigerant in the bypass loop 30 during the dedicated cooling mode of the second heat transfer fluid does not therefore penalize the cooling of said second heat transfer fluid.

Thus, it can clearly be seen that the method of management of the indirect reversible air-conditioning circuit 1 according to the invention makes it possible to prevent the first heat exchanger 9 from undergoing a refrigerant pressure that is too high when the indirect reversible air-conditioning circuit 1 is in a dedicated cooling mode of the second heat transfer fluid.

Claims (8)

1. A method for managing an invertible indirect air conditioning circuit (1) for a motor vehicle comprising a first refrigerant fluid loop (A) in which a refrigerant circulates and comprising a first bifluid heat exchanger (5) arranged jointly on the first refrigerant loop (A) and a second heat transfer fluid loop (B) in which a first heat transfer fluid circulates, the first bifluid heat exchanger (5) being arranged to allow heat exchange between the first loop refrigerant fluid (A) and the second heat transfer fluid loop (B), the first heat transfer fluid loop (A) comprising: • a compressor (3), • the first bifluid heat exchanger (5), disposed downstream of said compressor (3), • a first expansion device (7) constantly passing coolant, • a first heat exchanger (9) being intended to be e traversed by an interior air flow (100) to the motor vehicle, • a second expansion device (11), • a second heat exchanger (13) being intended to be traversed by an outside air flow (200) to the motor vehicle, and • a bypass loop (30) of the second heat exchanger (13), • a device for redirecting the refrigerant fluid from the first heat exchanger (9) to the second heat exchanger (13) or to the bypass loop (30), • a bypass line (80) connected on the one hand between the first two-fluid heat exchanger (5) and the first expansion device (7) and on the other hand between the output of the bypass loop (30) and the compressor (3), said bypass line (80) having a third expansion device (12) disposed upstream of a second bifluid heat exchanger (83) for heat exchange between the refrigerant fluid ant and a second heat transfer fluid, said circuit comprising a pressure sensor (71) of the refrigerant at the outlet of the first bifluid heat exchanger (5), characterized in that the indirect reversible air conditioning circuit (1) comprises a central unit of control (90) connected to said pressure sensor (71) of the refrigerant at the outlet of the first bifluid heat exchanger (5) and adapted to drive the first coolant redirection device, when the indirect air conditioning circuit (1) is in a dedicated cooling mode of the second coolant in which the coolant passes through the bypass line (80) and does not pass through the second heat exchanger (13), the central control unit (90) controls the redirecting device of the refrigerant so that: • if the pressure measured at the pressure sensor (71) of the refrigerant at the outlet of the first heat exchanger bifluid (5) is less than the limit pressure value, the coolant redirection device prevents the passage of the refrigerant in the bypass loop (30), • if the pressure measured at the pressure sensor (71) of the refrigerant fluid at the outlet of the first bifluid heat exchanger (5) is greater than or equal to a limit pressure value, the device for redirecting the refrigerant fluid allows the passage of refrigerant in the bypass loop (30). 2. A method of managing an invertible indirect air conditioning circuit (1) according to the preceding claim, characterized in that the third expansion device (12) is an electronic expansion valve controlled by the central control unit (90). and that as the coolant passes into the bypass loop (80), the opening of the third expansion device (12) is controlled so that the refrigerant fluid at the inlet of the compressor (3) reaches a target superheat value. 3. A method for managing an invertible indirect air conditioning circuit (1) according to the preceding claim, characterized in that if the target superheat value of the refrigerant at the inlet of the compressor (3) can not be reached, the opening the third expansion device (12) is controlled to be at its minimum. 4. A method of managing an invertible indirect air conditioning circuit (1) according to one of claims 2 or 3, characterized in that the target superheat is between 5 and 22 ° C. Method for managing an invertible indirect air-conditioning circuit (1) according to one of the preceding claims, characterized in that the central control unit (90) regulates the speed of the compressor (3) so that the pressure refrigerant at the outlet of the first heat exchanger (9) reaches a target value, said target value of the refrigerant pressure being calculated as a function of a target temperature of a second heat transfer fluid at the outlet of the second bifluid heat exchanger (83). 6. A method of managing an invertible indirect air conditioning circuit (1) according to one of the preceding claims, characterized in that the refrigerant is selected from R1234yf and R134a. 7. A method of managing an invertible indirect air-conditioning circuit (1) according to one of the preceding claims, characterized in that the limit pressure value of the refrigerant at the outlet of the first bifluid heat exchanger (5) is included between 10 and 15 bars. Inverter reversible air conditioning circuit (1) for a motor vehicle comprising a first refrigerant fluid loop (A) in which a refrigerant circulates and comprising a first bifluid heat exchanger (5) arranged jointly on the first refrigerant loop ( A) and on a second heat transfer fluid loop (B) in which a first heat transfer fluid circulates, the first bifluid heat exchanger (5) being arranged so as to allow the exchange of heat between the first refrigerant loop (A). and the second coolant loop (B), the first heat transfer fluid loop (A) comprising: • a compressor (3), • the first bifluid heat exchanger (5), disposed downstream of said compressor (3), • a first expansion device (7) permitting constant passage of refrigerant, • a first heat exchanger (9) being intended to be traversed by a flow of air interior (100) to the motor vehicle, • a second expansion device (11), • a second heat exchanger (13) intended to be traversed by an outside air flow (200) to the motor vehicle, and • a bypass loop (30) of the second heat exchanger (13), • a device for redirecting the coolant from the first heat exchanger (9) to the second heat exchanger (13) or to the bypass loop (30). ), A bypass line (80) connected on the one hand between the first bifluid heat exchanger (5) and the first expansion device (7) and on the other hand between the exit of the bypass loop (30) and the compressor (3), said bypass line (80) having a third expansion device (12) arranged upstream of a second bifluid heat exchanger (83) for exchanging heat between the refrigerant and a second fluid calo carrier, said circuit comprising a pressure sensor (71) of the refrigerant fluid at the outlet of the first bifluid heat exchanger (5), characterized in that the indirect reversible air conditioning circuit (1) comprises a central control unit (90) connected to said pressure sensor (71) of the refrigerant at the outlet of the first two-fluid heat exchanger (5) and adapted to drive the first coolant redirection device, when the indirect air-conditioning circuit (1) is in a dedicated cooling mode a second coolant in which the coolant flows through the bypass line (80) and does not pass through the second heat exchanger (13), the central control unit (90) being configured to control the coolant redirection device so that: • if the pressure measured at the pressure sensor (71) of the refrigerant at the outlet of the first heat exchanger fluid (5) is less than the limit pressure value, the coolant redirection device prevents the passage of refrigerant in the bypass loop (30), • if the pressure measured at the pressure sensor (71) of the refrigerant fluid at the outlet of the first bifluid heat exchanger (5) is greater than or equal to a limit pressure value, the device for redirecting the refrigerant fluid allows the passage of refrigerant in the bypass loop (30).