METHOD FOR CONTROLLING A THERMAL CONTROL LOOP, IN PARTICULAR FOR A MOTOR VEHICLE

Description

[0001] The invention relates to a method for controlling a thermoregulation loop, particularly for motor vehicles. A method for controlling a thermoregulation loop of a known type is disclosed in US patent 2018 / 281564 A1.

[0002] Motor vehicles are commonly equipped with a thermal control system that includes a refrigerant circulation loop used to heat or cool different areas or components of the vehicle. This system is notably used to provide thermal treatment to, on the one hand, the airflow sent into the vehicle's passenger compartment and, on the other hand, to a battery or other electrical components of the vehicle.

[0003] In such a case, circuits are known to have two branches, one for the thermo regulation of the airflow and the other for the thermo regulation of the battery.

[0004] The circuit is controlled from various parameters which, while limiting the energy consumption supplied to a compressor in the circuit, optimize thermoregulation both when only one of the two branches is operating and when both branches are operating at the same time.

[0005] However, the applicant observed that the control strategies employed are not entirely satisfactory. Specifically, when the circuit must switch from a configuration where only one branch is operating to one where both branches are operating, the thermal regulation exhibits an excessively long response time. For example, when switching from a configuration where only the airflow temperature regulation branch is operating, particularly in air conditioning mode, to a configuration where both branches are operating, this causes a rapid increase of several degrees in the passenger compartment, which is felt by the passengers before the control strategy allows the temperature to be lowered to a lower value, thus minimizing the perceived temperature.Equivalent phenomena are observed in other configuration changes, namely when moving from a configuration where only the battery thermoregulation branch operates to a configuration where both branches operate, or when moving from a configuration where both branches operate to a configuration where only the airflow thermoregulation branch or the battery thermoregulation branch operates.

[0006] The invention aims to overcome, at least in part, the aforementioned drawbacks and, to this end, proposes a method for controlling a thermoregulation loop through which a refrigerant flows, in particular a thermoregulation loop of a motor vehicle, said loop comprising at least a first and a second branch for fluid circulation, said method being configured to transition the loop from a first state in which the fluid flows in only one of said branches to a second state in which the fluid flows simultaneously in said branches, and vice versa.said method comprising a step of controlling the flow of the fluid in one and / or the other of the branches according to a first control strategy during operation in a steady state of the first or second state and a step of modifying the fluid flow according to a second control strategy during a transition from one of the states to another of the states so as to limit a temperature difference during said transition, wherein the second strategy comprises a calculation of a setpoint value by adding or subtracting an offset value from a value delivered by the first strategy.

[0007] Implementing a specific control strategy, namely the second strategy, during a transition from one state to the other allows for managing transient modes without relying on the strategy used in steady-state mode. This makes it possible to achieve fluid flow in branches that control heat exchange and therefore temperature differences, particularly in the branch operating both before and after the state change.

[0008] According to various characteristics which may be taken separately or according to any technically possible combinations, forming as many embodiments of the invention: The first and second branches are parallel. The first branch includes a thermoregulation branch for an airflow, specifically an airflow circulating inside the passenger compartment of a motor vehicle. The second branch includes a thermoregulation branch for electrical components, specifically a vehicle battery. In the event of a transition from the first state, in which the fluid flows only in the first branch, to the second state, the modification step includes a closing step of a first expansion valve of the first branch and / or an acceleration step of a compressor in the loop. In the event of a transition from the second state, in which the fluid flows only in the second branch, to the second state, the modification step includes a closing step of a second expansion valve of the second branch and / or an acceleration step of the compressor in the loop.In the event of a transition from the second state to the first alternative of the first state, the modification step includes a step of opening the first expansion valve of the first branch and / or a step of slowing down the compressor of the loop; in the event of a transition from the second state to the second alternative of the first state, the modification step includes a step of opening the second expansion valve of the second branch and / or a step of slowing down the compressor; said compressor acceleration step is carried out by accelerating the compressor by at least 20%, or even at least 25%; said compressor deceleration step is carried out by slowing down the compressor by at least 20%, or even at least 25%; said step of closing the first or second expansion valve is carried out by closing the first or second expansion valve respectively by at least 20%, or even at least 30%.The opening step of the first or second expansion valve is carried out by opening said first or second expansion valve respectively by at least 20%, or even by at least 30%. The first strategy includes taking into account control parameters such as the temperature of an airflow passing through an evaporator of the first branch, the temperature of another fluid passing through a cooler of the second branch allowing heat exchange between said other fluid and the refrigerant, the temperature of the refrigerant at the compressor inlet and / or the pressure of the refrigerant at the inlet and / or outlet of the compressor. The method includes a step of opening or closing a valve located on the first branch and / or the second branch to trigger the transition from one state to another. Said offset value is a constant, said offset value is a value dependent on loop characteristics.said offset value is a function of a cooling power ratio between the cooling power of the chiller and the cooling power of the evaporator; said offset value is a function of a temperature difference between the temperature of the other fluid measured at the outlet of the chiller and a setpoint temperature; the time between the triggering of the transition from one state to the other and reaching the setpoint value(s) resulting from the calculation relating to the second strategy is less than 20 seconds, or even 10 seconds.

[0009] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached drawings in which: There figure 1 schematically illustrates an example of a circulation loop with which the control method according to the invention can be implemented. figure 2 is a graph illustrating the variation of different control parameters of the loop's operation figure 1 as well as the associated variation of different associated physical quantities, according to an example of implementation of the process according to the invention.

[0010] As illustrated in the figure 1 The invention relates to a temperature control loop through which a refrigerant flows, and more specifically to a method for controlling said loop. This is particularly relevant to a temperature control loop for a motor vehicle. This loop is specifically configured to allow the temperature regulation of an interior airflow directed to the vehicle's passenger compartment and / or the temperature regulation of the vehicle's electrical components, such as a battery, using an outside airflow and through direct or indirect heat exchange with said refrigerant. In the case of indirect heat exchange, a heat transfer fluid is preferably used to exchange heat with the refrigerant, the outside airflow, and / or the interior airflow.

[0011] The terms upstream and downstream used in the following description refer to the direction of flow of the fluid in question, i.e. the refrigerant, the heat transfer fluid, the outside airflow and / or the inside airflow.

[0012] The terms "first," "second," etc., used hereafter are not intended to indicate a hierarchical level or order the terms they accompany. These terms simply serve to distinguish the terms in question and may be interchanged without reducing the scope of the invention.

[0013] The refrigerant, for example, is a fluid capable of changing from a liquid to a gaseous phase and vice versa under the temperature and pressure conditions of the refrigerant circulation loop. It could be a fluid known as R134a or R1234yf. It could also be a fluid that remains essentially in a gaseous state, such as R744.

[0014] The heat transfer fluid is, for example, a liquid, in particular water with added antifreeze such as glycol.

[0015] Said loop comprising at least a first branch 2 and a second branch 4 of refrigerant circulation.

[0016] Preferably, it also includes a main branch 6 which forms a closed circuit with the first branch 2 and the second branch 4. In other words, the first branch 2 and the second branch 4 are in parallel with each other. They are located between a first branch point 8 of the main branch 6 and a second branch point 10 of the main branch 6.

[0017] The said main branch 6 includes, for example, a compressor 12 and a two-fluid exchanger 14.

[0018] The two-fluid heat exchanger 14 is advantageously configured to allow heat exchange between the refrigerant and the heat transfer fluid. This two-fluid heat exchanger is integrated into a heat transfer fluid circulation loop 16, partially illustrated. The two-fluid heat exchanger is, for example, a condenser enabling at least partial condensation of the refrigerant exiting the compressor 12. This two-fluid heat exchanger is located between the compressor 12 and the first branch point 8 in the refrigerant loop.

[0019] The main branch further includes an evaporator-condenser 18. This evaporator-condenser 18 is configured to allow heat exchange between the refrigerant and the outside airflow, thereby causing the refrigerant to undergo a phase change, namely condensation or evaporation, depending on the operating mode of the loop. In this loop, the evaporator-condenser 18 is positioned upstream of the compressor 12, specifically between the second branch point 10 and the compressor 12. The evaporator-condenser 18 is located, for example, at the front of the vehicle so that it is traversed by an airflow that has previously passed through a grille of the vehicle.

[0020] Said first branch 2 is preferably configured to allow thermoregulation of the internal airflow. It includes, for example, a first electronic expansion valve 20 and an evaporator 22, positioned in that order according to the direction of circulation of the refrigerant.

[0021] The said first electronic expansion valve 20 is configured to present a variable passage opening of the refrigerant fluid, said passage opening being electronically controllable.

[0022] The evaporator 22 is configured to allow heat exchange between the refrigerant and the interior airflow. This evaporator is located, for example, in a heating, ventilation, and air conditioning (HVAC) unit. This unit is typically located under the vehicle's dashboard.

[0023] Said second branch 4 is preferably configured to allow the thermoregulation of a battery. It includes, for example, a second electronic expansion valve 24 and a cooler 26, positioned in that order according to the direction of circulation of the refrigerant.

[0024] Like the first expansion valve 20, said second electronic expansion valve 24 is configured to present a variable passage opening of the refrigerant fluid, said passage opening being electronically controllable.

[0025] The cooler 26 is configured to allow heat exchange between the refrigerant and the coil, either directly or indirectly. In the illustrated example, this is indirect cooling, with the cooler 26 configured to allow heat exchange between the refrigerant and the heat transfer fluid, and heat exchange also occurring between the heat transfer fluid and the coil. The cooler 26 may be integrated into the same heat transfer fluid circulation loop as the two-fluid heat exchanger 14. Alternatively, it may be integrated into a separate heat transfer fluid circulation loop.

[0026] The second branch 4 further includes a first valve 28 and / or a second valve 30. These are, in particular, on / off valves configured to allow the refrigerant to flow with no or very little pressure loss in the open position, and to stop the refrigerant flow in the closed position. The first valve 28 is located between the first branch point 8 and the second electronic expansion valve 24. The second valve 30 is located between the cooler 26 and the second branch point 10.

[0027] In the illustrated embodiment, the first branch 2 also includes a valve 28', in particular between the first branch point 8 and the first electronic expansion valve 20. Alternatively, another valve may be located in a complementary or alternative manner between the evaporator 22 and the second branch point 10. Also alternatively, said first branch 2 does not include such valves.

[0028] The first expansion valve 20 and / or the second expansion valve 24 operate, for example, between a completely open valve and a partial opening corresponding to the smallest possible opening that results in a very small, or even zero, residual expansion effect. Between these two positions, the expansion of the refrigerant depends on the degree of valve opening. This degree of opening is determined, in particular, by a control step ranging from 0 for the closed position to 5000 for the fully open position. The operating range is, for example, between 0 and 500 steps.

[0029] To facilitate the control of the refrigerant circulation loop, various sensors are provided. In the illustrated example, these include a refrigerant pressure sensor 31 at the outlet of the compressor 12, a heat transfer fluid temperature sensor 32 at the outlet of the two-fluid heat exchanger 14, a temperature sensor 36 of the internal airflow temperature passing through the evaporator 22, a temperature sensor 38 of the external airflow temperature passing through the evaporator-condenser 18, a heat transfer fluid temperature sensor 34 at the outlet of the cooler 26, a pressure sensor 40 at the inlet of the compressor 12 and / or a temperature sensor 42 at the inlet of said compressor 12.

[0030] The loop is preferably configured to operate according to different modes of temperature control for the interior airflow and / or different modes of temperature control for the battery. Temperature control modes for the interior airflow include, for example, a cabin air conditioning mode in which the interior airflow is cooled, a heat pump mode in which the interior airflow is heated, and / or a dehumidification mode in which the airflow is cooled and then reheated. Other temperature control modes for the interior airflow are also possible. In these different temperature control modes for the interior airflow, the refrigerant circulates in the first branch 2, although it is also possible that there is no refrigerant circulation in said first branch 2.The battery temperature control modes include a battery cooling mode, a battery heating mode, and / or a mode with neither battery heating nor cooling. In these different battery temperature control modes, the refrigerant may or may not circulate in the second branch 4.

[0031] To enable these different modes, the heat transfer fluid circulation loop, in which the two-fluid heat exchanger 14 is integrated, advantageously includes a first additional heat exchanger (not shown), for example, located at the front of the vehicle, behind the grille. This first additional heat exchanger is configured to allow heat exchange between the outside airflow and the heat transfer fluid. It is located, for example, in series with the condenser-evaporator 18, depending on the direction of the outside airflow, upstream and / or downstream. It is used, for example, in air conditioning mode to release into the outside airflow the heat generated by the heat transfer fluid in the two-fluid heat exchanger 14. It could be, for example, a cooling radiator.

[0032] Advantageously, the heat transfer fluid circulation loop also includes a second, additional heat exchanger (not shown) configured to allow heat exchange between the indoor airflow and the heat transfer fluid. This second heat exchanger is located, for example, in the HVAC unit, specifically downstream of the evaporator 22, depending on the direction of the outdoor airflow. It is used, for example, in heat pump mode, to supply the indoor airflow with the heat absorbed by the heat transfer fluid in the dual-fluid heat exchanger 14. This could be, in particular, a heating radiator and / or air heater.

[0033] According to various variants not illustrated, to allow the greatest number of thermoregulation modes, said refrigerant circulation loop includes different branches in addition to those of the illustrated embodiment, said branches being traversed or not by the refrigerant depending on the thermoregulation modes chosen.

[0034] The heat transfer fluid circulation loop advantageously includes at least one fluid drive pump. According to various (not illustrated) variations, to allow for the greatest number of temperature control modes, it includes different branches, some of which may or may not be used by the heat transfer fluid depending on the temperature control modes chosen.

[0035] As will be understood, in this type of application, depending on the thermoregulation modes chosen for the internal fluid and / or for the battery, the refrigerant circulates either only in the first branch 2, or in the second branch 4, or simultaneously in both branches 2 and 4. In other words, we are either in a first state with circulation in only one of these branches 2 and 4, or in a second state with simultaneous circulation in both branches 2 and 4. Furthermore, in the event of a change in the thermoregulation modes, the transition from one state to the other may then be necessary.

[0036] The method according to the invention is thus configured to take the refrigerant circulation loop from a first state in which the fluid circulates in only one of said branches 2, 4 to a second state in which the fluid circulates simultaneously in said branches 2, 4, and vice versa.

[0037] That being said, apart from these moments of state change, the process according to the invention includes a step of controlling the flow of the refrigerant in one or both of the branches 2, 4 according to a first control strategy. This is therefore a control strategy that is executed during operation in a steady-state mode of the first or second state, that is to say, when the refrigerant loop remains in the first or second state. In other words, in the illustrated example, whether the loop is used with or without thermoregulation of the coil and / or with or without thermoregulation of the internal airflow, the first strategy is executed as long as the loop remains in the first or second state, even if the variables involved are not the same from one state to the other. The purpose of this first strategy is, in particular, to minimize the energy supplied to the compressor 12 to ensure the chosen thermoregulation modes.

[0038] The said first strategy advantageously includes taking into account control parameters such as the temperature of the airflow through the evaporator 22, the temperature of the heat transfer fluid at the outlet of the two-fluid exchanger 14, the temperature of the heat transfer fluid at the outlet of the cooler 26, the temperature of the refrigerant fluid at the inlet of the compressor 12 and / or a pressure of the refrigerant fluid at the inlet and / or outlet of the compressor 12.

[0039] The said first strategy makes it possible to determine, in particular, a speed of the compressor 12 and / or a degree of opening of the first regulator 20 and / or of the second regulator 24.

[0040] However, it has been observed that if this initial strategy is maintained during a transition from one state to another, significant temperature differences occur that can be felt by the occupants of the passenger compartment. This is the case, for example, when transitioning from the first state to the second state in the scenario where the first state corresponds to refrigerant circulation in the first branch 2, in air conditioning mode. One explanation is that the power of the compressor 12 is then abruptly divided between the first branch 2 and the second branch 4, and that the control parameters of the first branch, particularly the measurement of the interior airflow temperature, have a relatively long response time, notably due to the technology used for the associated sensor 36.It is therefore necessary to wait for the sensor's response time for the control process to generate a reaction tending to limit the temperature difference, in particular by accelerating the rotation speed of compressor 12.

[0041] To avoid this, more efficient sensors could be used, but they are expensive. The control method according to the invention, on the other hand, offers a solution without changing the sensor by implementing a step that modifies the flow of the refrigerant according to a second control strategy during the transition from one state to another.

[0042] In the event of a transition from the first alternative state, in which the fluid flows only in the first branch 2, to the second state, the modification step includes a closing step of the expansion valve 20 of the first branch 2 and / or an acceleration step of a compressor 12 of the loop,

[0043] In the event of a transition from a second alternative from the first state in which the fluid flows only in the second branch 4 to the second state, the modification step includes a closing step of the expansion valve 24 of the second branch 4 and / or a step of accelerating the compressor 12.

[0044] In the event of a transition from the second state to the first alternative of the first state, that is to say the one where the refrigerant circulates only in the first branch 2, the modification step includes a step of opening the expansion valve 20 of the first branch 2 and / or a step of slowing down the compressor 12.

[0045] In the event of a transition from the second state to the second alternative of the first state, that is to say the one where the refrigerant circulates only in the second branch 4, the modification step includes a step of opening the expansion valve 24 of the second branch 4 and / or a step of slowing down the compressor 12.

[0046] In these different scenarios, the compressor 12 acceleration step is carried out by accelerating the compressor, for example, by at least 20%, or even by at least 25%. The compressor 12 deceleration step is carried out by decelerating the compressor 12, for example, by at least 20%, or even by at least 25%.

[0047] The closing step of the first or second regulator 20, 24 is carried out by closing the regulator by at least 20%, or even by at least 30%. The opening step of the first or second regulator 20, 24 is carried out by opening said regulator by at least 20%, or even by at least 30%.

[0048] Preferably, the process includes a step of opening or closing the valve(s) 28, 28' located on the first branch 2 and / or the second branch 4 to trigger the transition from one state to another. In other words, in this variant, it is the order in which said valve(s) 28, 28' are opened and / or closed that determines the switch from the first to the second strategy.

[0049] The second strategy includes, for example, calculating a setpoint value by adding or subtracting an offset value from a value provided by the first strategy. This involves calculating a setpoint value for the rotational speed of compressor 12 and / or the opening angle of the first and / or second expansion valve 20, 24. In other words, the setpoint value calculated according to the second strategy for the speed of compressor 12 is equal to a setpoint value for said speed from the first strategy, to which an offset value is added or subtracted. Similarly, the setpoint value calculated according to the second strategy for the opening angle of the first or second expansion valve 20, 24 is equal to a setpoint value for said opening angle from the first strategy, to which an offset value is added or subtracted.

[0050] According to a first embodiment, the offset value is a predetermined constant. Alternatively, it is a value dependent on characteristics of the refrigerant loop and / or one or both of the heat transfer fluid loops.

[0051] According to another embodiment, applicable in particular to the degree of opening of the first expansion valve 20 and / or the second expansion valve 24, said offset value is a function of a cooling power ratio between the cooling power of the cooler 26 and the cooling power of the evaporator 22.

[0052] According to another embodiment, applicable in particular to the rotational speed of the compressor 12, said offset value is, for example, a function of a temperature difference between the temperature of the heat transfer fluid measured at the outlet of the cooler 26 and a setpoint temperature of said temperature. This function is, in particular, a linear function taking into account a predetermined constant and a coefficient. This coefficient is chosen to favor reaching the setpoint temperature of the indoor airflow, using the first branch 2, or of the heat transfer fluid, using the second branch 4.

[0053] The time between the triggering of the transition from one state to the other—that is, according to the illustrated example, between the opening or closing of valve(s) 28, 28' of one of branches 2, 4, and the attainment of the setpoint values ​​mentioned above, namely the setpoint values ​​incorporating the aforementioned time lag—is preferably less than 20 seconds, or even 10 seconds. This means that the control law chosen to reach these setpoint values ​​is selected so as to achieve the setpoint in less than 20 seconds, or even less than 10 seconds. This allows for a reaction time long enough to prevent premature wear of the components while being short enough to limit temperature deviations relative to the system's inertia.

[0054] Once this setpoint value is reached, the first control strategy is advantageously resumed.

[0055] There figure 2 illustrates a transition from the first state in the alternative where the refrigerant circulates only in the first branch 2, in air conditioning mode, to the second state.

[0056] The x-axis indicates time, in minutes. The y-axis shows various values. These are the temperature of the heat transfer fluid at the outlet of the cooler 26, in degrees Celsius, curve 50, the rotation speed of the compressor 12, in thousands of revolutions per minute, curve 52, the degree of opening of the first expansion valve 20, in hundreds of steps, curve 54, the temperature of the internal airflow, in degrees Celsius, curve 56, and the dissipation power of the cooler 26, in kW, curve 58.

[0057] In the period illustrated A on the x-axis, we are in the first state in the alternative with circulation of the refrigerant fluid only in the first branch 2, the loop operating in air conditioning mode.

[0058] The strategy applied is the first strategy. The temperature of the internal airflow passing through the evaporator 22 is stable, between 3 and 4°C, as is the rotation speed of the compressor 12, around 3000 rpm, and the degree of opening of the first expansion valve 20, around 180 steps.

[0059] At the same time, the refrigerant does not circulate in the second branch 4 and the power dissipation of the cooler is zero.

[0060] However, under the conditions chosen for the test, the temperature of the heat transfer fluid at the outlet of the cooler 26 increases regularly and at a given moment, located in a period marked B, occurring between the thirty-fourth and thirty-fifth minutes, a temperature threshold is reached for said fluid, here a temperature located between 35 and 36° C. At such a temperature of the heat transfer fluid, it becomes necessary to cool the battery.

[0061] Advantageously, the control method according to the invention detects such a threshold crossing and causes the transition from the first state to the second state by opening said valves 28, 28' so that the refrigerant then circulates simultaneously in the first branch 2 and in the second branch 4, this to ensure cooling of the battery while remaining in air conditioning mode.

[0062] According to the method of the invention, the second strategy is then applied by adding a deviation of more than +1000 rpm to the compressor speed setpoint, ensuring that this setpoint is reached in less than 20 seconds. In addition, a deviation of more than -30 steps is applied to the opening degree of the first expansion valve, ensuring that this setpoint is reached in less than 10 seconds (given the accuracy of the graph of the figure 2 (this difference is not visible).

[0063] After these setpoint values ​​are reached, the first strategy then resumes over the period marked C. To achieve the desired cooling values ​​for the passenger compartment and the battery, the compressor is brought to a speed of 6000 rpm and the first expansion valve 2 is brought to a control step of approximately 140. With these characteristics, the temperature of the interior airflow passing through the evaporator 22 is 6°C and the temperature of the heat transfer fluid at the outlet of the cooler 26 is 21°C, this in relation to the dissipation power of said cooler established at approximately 2.2 KW.

[0064] During period B, it was observed that the temperature of the interior airflow did indeed increase by +4°C, but without the invention, by maintaining the first strategy, it would have increased by almost double before starting to fall back down, which would have resulted in a strong feeling in the passenger compartment.

Claims

1. A method for controlling a thermoregulation loop traversed by a refrigerant fluid, said loop comprising at least a first and a second branch (2, 4) for fluid circulation, said method being configured to switch the loop from a first state in which the fluid circulates in only one of said branches (2, 4) to a second state in which the fluid circulates simultaneously in said branches (2, 4), and vice versa, the method comprising a step of controlling a fluid flow in one and / or the other of the branches (2, 4) according to a first control strategy during operation in a steady mode of the first or second state, and a step of modifying the fluid flow according to a second control strategy during a transition from one of the states to another of the states so as to limit a temperature deviation during said transition, characterized in that the second strategy comprises a calculation of a set point value by adding or subtracting an offset value to a value delivered by the first strategy.

2. The method according to claim 1, wherein the first branch (2) comprises an airflow thermoregulation branch and / or the second branch (4) comprises a battery thermoregulation branch.

3. The method according to any one of claims 1 or 2, wherein, in case of a transition from an alternative of the first state in which the fluid circulates only in the first branch (2) to the second state, the modification step comprises a step of closing a first expansion valve (20) of the first branch (2) and / or a step of accelerating a compressor (12) of the loop, in case of a transition from an alternative of the first state in which the fluid circulates only in the second branch (4) to the second state, the modification step comprises a step of closing a second expansion valve (24) of the second branch (4) and / or a step of accelerating the compressor (12), in case of a transition from the second state to the first alternative of the first state, the modification step comprises a step of opening the first expansion valve (20) of the first branch (2) and / or a step of decelerating the compressor (12), in case of a transition from the second state to the second alternative of the first state, the modification step comprises a step of opening the second expansion valve (24) of the second branch (4), and / or a step of decelerating the compressor (12).

4. The method according to claim 3, wherein said compressor (12) acceleration step is performed by accelerating the compressor (12) by at least 20%, or even by at least 25%, and / or said compressor (12) deceleration step is performed by decelerating the compressor (12) by at least 20%, or even by at least 25%.

5. The method according to any one of claims 3 or 4, wherein said step of closing the first or second expansion valve (20, 24) is performed by closing respectively the first or second expansion valve (20, 24) by at least 20%, or even by at least 30%, and / or said step of opening the first or second expansion valve (20, 24) is performed by opening respectively said first or said second expansion valve by at least 20%, or even by at least 30%.

6. The method according to any one of claims 3 to 5, wherein the first strategy comprises taking into account control parameters from among a temperature of an air flow passing through an evaporator (22) of the first branch (2), a temperature of another fluid passing through a cooler (26) of the second branch (4) allowing heat exchange between said another fluid and the refrigerant fluid, a temperature of the refrigerant fluid at the inlet of the compressor (12) and / or a pressure of the refrigerant fluid at the inlet and / or outlet of the compressor (12).

7. The method according to any one of the preceding claims, comprising a step of opening or closing a valve (28, 28') located on the first branch (2) and / or the second branch (4) to initiate the transition from one of the states to another of the states.

8. The method according to claim 1, wherein said offset value is a constant and / or a value depending on characteristics of the loop.

9. The method according to any one of claims 7 or 8, wherein a duration between an initiation of the transition from one of the states to the other of the states and an attainment of the setpoint value(s) resulting from the calculation related to the second strategy is less than 20 seconds, or even less than 10 seconds.