HEAT CONDITIONING SYSTEM FOR A MOTOR VEHICLE

Description

technical field

[0001] The present invention relates to the field of thermal conditioning systems. Such systems can be used, in particular, in motor vehicles. These systems allow, for example, the temperature regulation of various vehicle components, such as the passenger compartment or an electrical energy storage battery, when the vehicle is electric or hybrid. Heat exchange is managed primarily by the compression and expansion of a refrigerant circulating in a circuit containing several heat exchangers. Previous technique

[0002] Thermal conditioning systems commonly employ a refrigerant circuit with a main refrigerant circulation loop and at least one branch running parallel to a portion of the main loop. Various valves allow for different refrigerant circulation combinations within the various circuit components. Several heat exchangers and refrigerant expansion devices control heat exchange within the thermal conditioning system. This enables the implementation of different operating modes, such as passenger compartment heating, passenger compartment cooling, or cooling of a specific component of the vehicle's powertrain, such as an electrical energy storage battery.

[0003] A method for controlling a thermal conditioning system of a known type is disclosed by document DE 10 2018 209769 A1.

[0004] A specific operating mode of the climate control system is, for example, a powertrain cooling mode. In this mode, a component of the vehicle's powertrain is cooled. This component could be, in particular, an electrical energy storage battery. This operating mode allows the battery to be cooled, for example, during charging. A thermally coupled evaporator, connected to the battery, provides this cooling. The heat extracted from the battery is transferred to the refrigerant circulating in the evaporator. This heat is then dissipated in another heat exchanger, for example, one that exchanges heat with an external airflow. Another commonly used operating mode is the cabin air conditioning mode.This operating mode cools the airflow supplying the passenger compartment, ensuring passenger comfort in hot environments. To achieve this, another heat exchanger, functioning as an evaporator, is traversed by the airflow supplying the passenger compartment and absorbs heat from this airflow. When the climate control system operates in powertrain cooling mode, the refrigerant flow is interrupted in the evaporator connected to the passenger compartment airflow. A shut-off valve, possibly supplemented by a non-return valve, isolates this section of the circuit from the active section of the refrigerant circuit. When the passenger compartment temperature is sufficiently cool, the refrigerant in the passenger compartment heat exchanger can condense.Since the sealing of the stopping means is generally not total, a progressive accumulation of liquid refrigerant can occur in the heat exchanger which may be traversed by the airflow inside the passenger compartment.

[0005] Such an accumulation of liquid refrigerant can disrupt the operation of the thermal conditioning system, as the amount of refrigerant available for heat exchange may become insufficient. The energy efficiency of the thermal conditioning system is then degraded. The invention proposes a method for controlling a thermal conditioning system to prevent excessive accumulation of liquid refrigerant in the unused heat exchanger when such operating conditions are encountered. Summary

[0006] To this end, the present invention proposes a method for controlling a thermal conditioning system, the thermal conditioning system comprising a refrigerant circuit configured to circulate a refrigerant, according to all the characteristics of claim 1.

[0007] By adjusting the value of at least one operating parameter of the heat recovery ventilation system, it can function with a refrigerant pressure at the outlet of the first evaporator that is below a predetermined pressure threshold. By choosing a sufficiently low value for this threshold, migration of the refrigerant to the second heat exchanger is prevented. This is because, in this case, there is no pressure difference that could induce the movement of gaseous refrigerant from the outlet of the first evaporator to the second heat exchanger.Furthermore, since the outlet pressure of the first evaporator is almost equal to the outlet pressure of the second heat exchanger, controlling the outlet pressure of the first evaporator below the saturated vapor pressure of the refrigerant at the outside air temperature prevents condensation of the refrigerant in the second heat exchanger. This avoids an unwanted accumulation of liquid refrigerant in the second heat exchanger. Several operating parameters can be modified to adjust the refrigerant pressure to a desired value. These parameters can be modified independently or in combination.

[0008] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0009] In one embodiment, the element of the electric powertrain is an electrical energy storage battery. The battery can, in particular, supply electrical energy to an electric traction motor of the vehicle.

[0010] Alternatively, the element of the electric powertrain can also be an electronic control module for an electric traction motor of the vehicle.

[0011] According to one embodiment, the first heat transfer fluid is a heat transfer liquid configured to circulate in a third heat exchanger, the third heat exchanger being configured to exchange heat with the airflow inside the passenger compartment of the motor vehicle.

[0012] According to another embodiment, the first heat transfer fluid is an airflow from inside the passenger compartment of the motor vehicle.

[0013] According to the invention, the process comprises the following steps: a) determine a temperature of the indoor airflow, b) determine a saturation vapor pressure of the refrigerant corresponding to the temperature of the indoor airflow, the pressure (P1) of the refrigerant at the outlet of the first evaporator (5) is controlled so as to be less than the determined value of the saturation vapor pressure (Ps).

[0014] This pressure threshold value prevents the refrigerant charge from shifting to the second heat exchanger. The thermal conditioning system can operate stably, without any gradual degradation of its thermal performance.

[0015] According to one embodiment, the process comprises the following steps: d1) reduce the passage cross-section of the first expansion device to a minimum value, e1) increase the passage cross-section of the second expansion device so that a flow of refrigerant fluid passes through the second heat exchanger.

[0016] By passing a flow of refrigerant fluid through the second heat exchanger, operating conditions are obtained that allow for the evaporation of any refrigerant liquid that may have accumulated in the second heat exchanger.

[0017] According to one example of implementation of the process, the minimum value of the passage cross-section of the first expansion device is zero.

[0018] According to another example of implementation of the process, the minimum value of the passage cross-section of the first expansion device is between 20% and 50% of a maximum passage cross-section of the first expansion device.

[0019] According to another aspect of the process, in which the compression device is of the rotary type, the process comprises the step: d2) increase the rotational speed of the compression device to a value above a predetermined speed threshold.

[0020] Increasing the rotational speed of the compression device, thereby increasing the flow rate of discharged high-pressure refrigerant, is another way to adjust the refrigerant pressure in the first evaporator to a desired value.

[0021] The compression device has a maximum rotation speed, and the predetermined speed threshold is greater than 80% of the maximum rotation speed.

[0022] According to an example of implementation, the process includes the following steps: d3) decrease the passage cross-section of the first decompression device, e3) maintain the passage cross-section of the second decompression device at a value of zero.

[0023] According to another implementation variant of the process, in which the thermal conditioning system includes a fourth heat exchanger configured to exchange heat with an outside airflow, the thermal conditioning system is configured to circulate the first heat transfer fluid through the fourth heat exchanger.

[0024] The fourth heat exchanger cools the heat transfer fluid circulating in the first heat exchanger by dissipating heat into the outside airflow.

[0025] According to one implementation method of the process, step ii) is repeated continuously while the thermal conditioning system is in operation.

[0026] This aspect of the control process is applied particularly when the refrigerant circuit does not include any mechanical device restricting the flow of refrigerant from the second connection point to the outlet of the second heat exchanger.

[0027] According to another implementation of the process, the refrigerant circuit includes a check valve disposed on the first branch branch downstream of the second heat exchanger and upstream of the second connection point, the check valve being configured to block refrigerant flow from the second connection point to an outlet of the second heat exchanger.

[0028] Alternatively, the refrigerant circuit includes a shut-off valve located on the first branch downstream of the second heat exchanger and upstream of the second connection point.

[0029] A non-return valve, or a shut-off valve, allows you to block, or at least limit, the flow of refrigerant from the outlet of the first evaporator to the outlet of the second heat exchanger.

[0030] The control process may include, before step ii), a step: i1) detect an accumulation of refrigerant in the second heat exchanger, and step ii) is implemented only if an accumulation of refrigerant fluid in the second heat exchanger is detected in step i1).

[0031] In this embodiment, the check valve, or the shut-off valve if used instead of the check valve, limits the flow of refrigerant to the second heat exchanger. This slows the accumulation of liquid refrigerant. It is therefore possible to apply the refrigerant pressure control step at the outlet of the first evaporator only when necessary. Temporary operation under conditions causing condensation of the refrigerant in the second heat exchanger is acceptable, as the accumulation of refrigerant is then slow.

[0032] According to one aspect of the invention, step ii) is followed by an operating step in a so-called traction chain cooling mode in which the first heat transfer fluid receives heat from the refrigerant and the second heat transfer fluid releases heat to the refrigerant, and in which a flow of refrigerant through the second heat exchanger is zero.

[0033] The powertrain cooling system is reactivated once the accumulated coolant has been vaporized by controlling the pressure in the first evaporator. This maximizes the cooling of the vehicle's powertrain component.

[0034] According to an example of process implementation, step i1) of detecting an accumulation of refrigerant in the second heat exchanger comprises the following substeps: determine a temperature of the second heat transfer fluid at the outlet of the first evaporator, if the determined temperature is above a first predetermined threshold, detect an accumulation of refrigerant fluid in the second heat exchanger.

[0035] Alternatively or in addition, step i1) of detecting an accumulation of refrigerant in the second heat exchanger includes the following sub-steps: determine a rate of change of temperature of the second heat transfer fluid at the outlet of the first evaporator, if the determined rate of change is greater than a second predetermined threshold, detect an accumulation of refrigerant fluid in the second heat exchanger.

[0036] A too-rapid increase in the temperature of the second heat transfer fluid indicates a lack of refrigerant circulating in the circuit and participating in heat exchange; in other words, it indicates an excessive accumulation of liquid refrigerant. Monitoring the temperature of the first heat transfer fluid therefore allows for the detection of refrigerant accumulation in the second heat exchanger.

[0037] According to one implementation example, the predetermined threshold depends on the electrical power of the transmission chain element.

[0038] According to one embodiment, in which the thermal conditioning system includes a refrigerant accumulation device disposed on the main loop downstream of the first heat exchanger and upstream of the first connection point, the step of detecting a refrigerant accumulation in the second heat exchanger comprises the following substeps: determine a superheat value of the refrigerant at the outlet of the first evaporator, if the determined superheat is greater than a third predetermined threshold, detect an accumulation of refrigerant in the second heat exchanger.

[0039] When the air conditioning system's design allows the refrigerant to overheat at the compressor inlet, monitoring the overheat value can diagnose a refrigerant deficiency in the refrigerant circuit. Excessive overheating thus indicates a lack of refrigerant circulating in the circuit.

[0040] According to another embodiment, in which the thermal conditioning system includes a refrigerant accumulation device disposed on the main loop downstream of the second connection point and upstream of the compression device, the step of detecting a refrigerant accumulation in the second heat exchanger comprises the following substeps: determine a subcooling value of the refrigerant at the inlet of the first expansion device, if the determined subcooling is less than a fourth predetermined threshold, detect an accumulation of refrigerant in the second heat exchanger.

[0041] When the architecture of the conditioning system allows subcooling of the refrigerant at the outlet of the first heat exchanger, in other words at the inlet of the first expansion device, a value of subcooling that is too low indicates a lack of refrigerant in the circuit.

[0042] According to one implementation method of the process, step ii) of controlling the pressure of the refrigerant fluid at the outlet of the first evaporator is applied for a predetermined duration.

[0043] According to one implementation example, the predetermined duration depends on the temperature of the indoor airflow.

[0044] According to another example of implementation, the process involves the following steps: a) determine an indoor airflow temperature, b) determine a saturated vapor pressure of the refrigerant for the determined value of the indoor airflow temperature, c) determine the difference between the saturated vapor pressure of the refrigerant for the determined value of the indoor airflow temperature and the predetermined threshold, and the predetermined duration depends on the difference determined in step c).

[0045] According to one embodiment, the thermal conditioning system includes a second branch connecting a third connection point located on the main loop downstream of the first connection point and upstream of the first expansion device to a fourth connection point located on the main loop downstream of the first evaporator and upstream of the second connection point, the second branch comprising a third expansion device and a third heat exchanger configured to exchange heat with an outside airflow to the passenger compartment of the motor vehicle.

[0046] The third heat exchanger allows the climate control system to operate in heat pump mode. In other words, in this mode, the heat required to vaporize the refrigerant in the third heat exchanger is extracted from the outside airflow and transferred to the inside airflow in the passenger compartment.

[0047] According to one implementation example, the thermal conditioning system includes an internal heat exchanger arranged jointly on the main loop downstream of the first heat exchanger and upstream of the first connection point, and on the main loop downstream of the second connection point and upstream of the compression device.

[0048] The internal heat exchanger increases the enthalpy change of the refrigerant during the thermodynamic cycle and improves the system's efficiency.

[0049] According to one embodiment, the process comprises the following steps: Heat the internal airflow so that the refrigerant pressure at the outlet of the first evaporator is below a predetermined threshold.

[0050] According to one example of implementation of the process, the thermal conditioning system includes an electric heating device, and the heating of the indoor airflow is achieved by activating an electric heating device.

[0051] The process therefore includes the following step: Activate the electric heating device for a predetermined duration.

[0052] According to one implementation variant of the process, the process comprises the following steps: operate the thermal conditioning system in a so-called energy recovery mode, in which the first heat transfer fluid receives heat from the refrigerant and the second heat transfer fluid gives heat to the refrigerant, to heat the indoor airflow, control the indoor airflow rate to a value below a predetermined threshold.

[0053] These steps help to limit the energy dissipated by the electric heating device, and therefore improve the energy efficiency of the system.

[0054] According to one embodiment, the first heat transfer fluid heats the internal airflow via the third heat exchanger.

[0055] According to one embodiment, the thermal conditioning system includes a movable flap configured to regulate a recirculation rate of the indoor airflow, and the method includes the step: control the position of the movable flap so that the recirculation rate of the indoor airflow is greater than a predetermined threshold.

[0056] According to one implementation variant, the predetermined threshold of the indoor airflow recirculation rate is constant.

[0057] According to another implementation variant, the process includes the step: detect the presence of at least one occupant in the vehicle's passenger compartment; if the presence of at least one occupant is detected, assign a first value to the predetermined threshold of the interior airflow recirculation rate; otherwise, assign a second value to the predetermined threshold of the interior airflow recirculation rate, the second value being greater than the first value.

[0058] The first value of the predetermined threshold for the indoor airflow recirculation rate is between 10% and 60%.

[0059] The second value of the predetermined threshold for the indoor airflow recirculation rate is between 60% and 100%. Brief description of the drawings

[0060] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: [ Fig. 1 ] is a schematic view of a thermal conditioning system according to a first embodiment of the invention, [ Fig. 2 ] is a schematic view of a thermal conditioning system according to a second embodiment of the invention, [ Fig. 3 ] is a schematic view of a thermal conditioning system according to a third embodiment of the invention, [ Fig. 4 ] is a schematic view of a variant of the thermal conditioning system of the figure 3 , [ Fig. 5 ] is a thermodynamic diagram illustrating the operation of the thermal conditioning system, [ Fig. 6 ] is a block diagram of the control method according to the invention, [ Fig. 7 ] is a schematic view of the thermal conditioning system of the figure 1 operating according to a mode of operation, called traction chain cooling mode, [ Fig. 8 ] is a schematic view of the thermal conditioning system of the figure 1 , operating according to a mode of operation, called passenger compartment air conditioning mode, [ Fig. 9 ] represents the temporal evolution of several parameters of the control process. Description of the implementation methods

[0061] To facilitate the reading of the figures, the different elements are not necessarily drawn to scale. In these figures, identical elements have the same reference numbers. Some elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate between similar, but not identical, elements or parameters. This indexing does not imply any priority of one element or parameter over another, and the designations can be interchanged.

[0062] In the following description, the term "a first element upstream of a second element" means that the first element is located before the second element relative to the direction of flow, or path, of a fluid. Similarly, the term "a first element downstream of a second element" means that the first element is located after the second element relative to the direction of flow, or path, of the fluid in question. In the case of a refrigerant circuit, the term "a first element upstream of a second element" means that the refrigerant flows successively through the first element, then the second element, without passing through the compression device. In other words, the refrigerant exits the compression device, possibly passes through one or more elements, then passes through the first element, then the second element, and then returns to the compression device, possibly after passing through other elements.The term "a second element is placed between a first element and a third element" means that the shortest path from the first element to the third element passes through the second element.

[0063] When it is specified that a subsystem includes a given element, this does not exclude the presence of other elements in that subsystem.

[0064] An electronic control unit, not shown in the figures, receives information from various sensors that measure, among other things, the characteristics of the refrigerant at different points in the circuit. The electronic control unit also receives instructions from the vehicle occupants, such as the desired temperature inside the passenger compartment. The electronic control unit implements control laws to operate the various actuators, ensuring that the climate control system 100 is controlled in a way that maintains the received parameters.

[0065] Each of the expansion devices used can be either an electronic or a thermostatic expansion valve. In the case of an electronic expansion valve, the passage area allowing the refrigerant to pass through can be continuously adjusted between a closed position and a fully open position. To achieve this, the system's control unit drives an electric motor that moves a movable damper, thus controlling the passage area available to the refrigerant. For a given position of the movable damper, the passage area is defined as the cross-sectional area of ​​a circular conduit providing the same flow rate for the same pressure differential between the inlet and outlet of the expansion device.

[0066] The compression device 2 can be an electric compressor, that is, a compressor whose moving parts are driven by an electric motor. The compression device 2 has a low-pressure refrigerant intake side, also called the inlet 2a of the compression device, and a high-pressure refrigerant discharge side, also called the outlet 2b of the compression device 2. The internal moving parts of the compressor 2 increase the refrigerant pressure from low pressure at the inlet 2a to high pressure at the outlet 2b. After expansion in one or more expansion devices, the refrigerant exiting the compressor 2 returns to the inlet 2a of the compressor 2 and begins a new thermodynamic cycle.

[0067] Each connection point allows the refrigerant to flow into one of the circuit sections that converge at that point. The refrigerant is distributed between these sections by opening or closing the shut-off valve(s), check valve(s), or expansion valve(s) located on each branch. In other words, each connection point redirects the refrigerant arriving at that point.

[0068] The refrigerant in refrigerant circuit 1 is a chemical fluid such as R1234yf. Other refrigerants can also be used, such as R134a.

[0069] We have represented on the figure 1a thermal conditioning system 100 comprising a refrigerant circuit 1 configured to circulate a refrigerant, the refrigerant circuit 1 comprising: A main loop A comprising successively, according to the direction of refrigerant flow: -- A compression device 2, -- A first heat exchanger 3 configured to exchange heat with a first heat transfer fluid F1, -- A first expansion device 4, -- A first evaporator 5 configured to exchange heat with an element 30 of a motor vehicle's powertrain via a second heat transfer fluid F2, A first branch B connecting a first connection point 11 located on the main loop A downstream of the first heat exchanger 3 and upstream of the first expansion device 4 to a second connection point 12 located on the main loop A downstream of the first evaporator 5 and upstream of the compression device 2,the first branch B comprising a second expansion device 6 and a second heat exchanger 7 configured to exchange heat with an internal airflow Fi to a passenger compartment of the motor vehicle.

[0070] The term "interior airflow" (Fi) refers to the airflow directed towards the passenger compartment of a motor vehicle. This interior airflow (Fi) may circulate within a heating, ventilation, and / or air conditioning (HVAC) system. This system is not shown in the various figures.

[0071] The thermal conditioning system 100 is configured to operate in a so-called traction chain cooling mode, in which the first heat transfer fluid F1 receives heat from the refrigerant and the second heat transfer fluid F2 releases heat to the refrigerant, and in which a flow of refrigerant through the second heat exchanger 7 is zero.

[0072] In the example shown here, element 30 of the electric powertrain is an electrical energy storage battery. Battery 30 can, in particular, supply electrical energy to an electric traction motor of the vehicle. In an alternative (not shown) configuration, element 30 of the electric powertrain can also be an electronic control module for an electric traction motor of the vehicle.

[0073] The circulation of the refrigerant in this operating mode is illustrated on the figure 7On the figure 7 as well as on the figure 8 The portions of the refrigerant circuit 1 in which refrigerant flows are shown with thick lines. The portions in which refrigerant does not flow are shown with dashed lines. In the example shown, the battery 30 is cooled during a charging phase. figure 5This is a pressure-enthalpy diagram of the refrigerant during the thermodynamic cycle performed in the so-called traction chain cooling mode. Point A2a illustrates the state of the refrigerant at low pressure at the inlet of compressor 2, point A2b illustrates the state of the refrigerant at high pressure at the outlet of compressor 2. Point A3 illustrates the state of the refrigerant at high pressure at the outlet of the first heat exchanger 3. Point A4 illustrates the state at the outlet of the first expansion device 4. Point A5 illustrates the state at the outlet of the first evaporator 5. Points A5 and A2b are essentially coincident. The line marked with the symbol S corresponds to the saturation curve of the refrigerant. The amount of heat extracted from the Q30 coil is represented by the enthalpy difference between point A4 and point A5.The amount of heat rejected in the first heat transfer fluid F1 at the first heat exchanger 3 is represented schematically by Q3, and is equal to the enthalpy change between point A2b and point A3. When the battery charging operation is carried out in a cold or cool environment, the temperature of the airflow inside the passenger compartment Fi can be close to the ambient temperature, assumed here to be -10°C. The battery temperature is higher because the charging current heats the battery, and the optimal temperature range for the battery is approximately between 25°C and 35°C. The temperature regulation performed by the thermal conditioning system 100 therefore aims to ensure a battery temperature higher than the ambient temperature at that time. On the... figure 5 The battery temperature is 0°C. The diagram shows the pressure conditions in the first evaporator 5 and in the second heat exchanger 7.

[0074] Even though the second heat exchanger 7 is inactive, meaning that the refrigerant flow is blocked because the second expansion valve 6 is closed, this heat exchanger 7 still contains refrigerant. The pressure of this refrigerant is equal to the saturation pressure corresponding to the temperature in the vicinity of the second heat exchanger 7. Since the refrigerant exiting the first evaporator 5 is at a pressure P1 higher than the equilibrium or saturation pressure Ps(Tint) in the second heat exchanger 7, the refrigerant leaving the first evaporator 5 and returning to the compressor 2 can migrate, at the second connection point 12, towards the second heat exchanger 7, and condense there. In other words, the refrigerant circulating in the main loop A and passing through the first evaporator 5 gradually accumulates in the second heat exchanger 7.Point A7b illustrates the liquid fraction of refrigerant in the second heat exchanger 7. The liquid fraction may vary from this illustrative diagram. This gradual accumulation can lead to an insufficient quantity of refrigerant participating in heat exchange, degrading the performance of the thermal conditioning system 100. This uncontrolled accumulation should be avoided.

[0075] To achieve this, the process for controlling the thermal conditioning system 100 includes the following steps: i) determine a pressure P1 of the refrigerant at the outlet of the first evaporator 5, ii) control, as a function of the pressure P1 determined, at least one parameter among the following parameters: passage area S4 of the first expansion device 4, passage area S6 of the second expansion device 6, flow rate Q of refrigerant supplied by the compression device 2, temperature Ti of the internal air flow Fi, so that the pressure P1 of the refrigerant at the outlet of the first evaporator 5 is less than a predetermined pressure threshold Pmax.

[0076] Controlling a parameter means modifying it on demand to produce a desired effect. The flow paths of the first and second expansion devices are controlled by an electrical actuator that adjusts the position of a movable damper. The refrigerant flow rate supplied by the compressor is controlled by the rotational speed of its moving parts. The temperature of the second heat transfer fluid is controlled by adjusting a device that regulates the heat exchange between the second fluid and a heat source. The electronic control unit can manage all the parameters listed.

[0077] By adjusting the value of at least one operating parameter of the heat recovery ventilation system, it can operate with a refrigerant pressure P1 at the outlet of the first evaporator 5 that is lower than a predetermined pressure threshold Pmax. By choosing a sufficiently low value for this threshold Pmax, migration of the refrigerant from the first evaporator 5 to the second heat exchanger 7 is prevented. This is because, in this case, there are no thermodynamic conditions favorable to the condensation of the refrigerant in the second heat exchanger 7. An undesirable accumulation of liquid refrigerant in the second heat exchanger 7 is thus avoided. Several operating parameters can be modified to adjust the refrigerant pressure to a desired value. These parameters can be modified independently or in combination.

[0078] The control process is a method for controlling the quantity of refrigerant circulating in the refrigerant circuit. In other words, the control process allows for controlling the ratio between the quantity of refrigerant in its liquid state and the quantity of refrigerant in its gaseous state in circuit 1.

[0079] According to one embodiment, illustrated on the figure 1The first heat transfer fluid F1 is a heat transfer liquid configured to circulate in a third heat exchanger 8. This third heat exchanger 8 is configured to exchange heat with the airflow Fi inside the passenger compartment of the motor vehicle. The third heat exchanger 8 is located in the air circulation housing of the heating, ventilation, and / or air conditioning system. According to the direction of the airflow Fi, the third heat exchanger 8 is located downstream of the second heat exchanger 7. The arrow Fi, illustrating the flow of the airflow inside the vehicle, passes successively through the second heat exchanger 7 and then the third heat exchanger 8. The first heat transfer fluid F1 circulates in a circuit 23. A circulation pump 29 circulates the first heat transfer fluid in the circuit 23. Similarly, the second heat transfer fluid F2 circulates in a circuit 24.Circuit 24 is thermally coupled with element 30 of the vehicle's traction chain.

[0080] In this embodiment, the first heat exchanger 3 is a two-fluid heat exchanger arranged jointly on the refrigerant circuit 1 and on the first heat transfer fluid circuit 23 F1, so as to allow heat exchange between the refrigerant and the first heat transfer fluid F1. The first heat transfer fluid F1 is, for example, a glycol-water mixture. The passenger compartment is thus heated indirectly, since the heat exchange between the refrigerant and the passenger compartment air is carried out via an intermediate heat transfer fluid. This intermediate heat transfer fluid circulates in the circuit 23.

[0081] According to another embodiment, illustrated on the figure 2The first heat transfer fluid F1 is an airflow Fi inside the passenger compartment of the motor vehicle. The heating of the passenger compartment is provided in a so-called direct manner, by heat exchange between the refrigerant fluid and the airflow Fi intended for the passenger compartment.

[0082] In this embodiment, the first heat exchanger 3 is located within the air circulation housing of the heating, ventilation, and / or air conditioning (HVAC) system. A motor-fan assembly, not shown in the figures, is located within the HVAC system to increase the flow rate of the interior airflow Fi if necessary. The arrow Fi, illustrating the flow of the interior airflow, passes successively through the second heat exchanger 7 and then the first heat exchanger 3. The interior airflow Fi can consist of a recirculated air fraction, i.e., air that was already present in the passenger compartment, and a fresh air fraction, i.e., air drawn from the ambient air outside the vehicle. Various air inlets and movable flaps allow adjustment of the distribution between the recirculated and fresh air fractions in the passenger compartment.

[0083] External airflow (Fe) refers to airflow that is not directed into the vehicle's passenger compartment. In other words, this airflow (Fe) remains outside the vehicle's passenger compartment. Another fan / motor unit, also not shown, can be activated to increase the flow rate of the external airflow (Fe) if necessary. This fan / motor unit is located, for example, at the front of the vehicle, behind the grille.

[0084] The first expansion device 4 has an adjustable flow area between a minimum value Smin4 and a maximum value Smax4. To achieve this, a movable shutter, not shown, can be moved between two extreme positions. The movement of the movable shutter can be continuous, meaning that the shutter can occupy all intermediate positions between the two extremes. In other words, the flow rate through the expansion device can vary continuously depending on the position of the movable shutter. The maximum value of the flow area corresponds to the value obtained when the movable shutter is in its maximum opening position. The minimum value corresponds to the value obtained when the movable shutter is in its minimum opening position. The minimum opening position can be zero. In this case, the expansion device is said to be in the closed position.The movable shutter can then be in contact with a seat, so that the flow rate of refrigerant through the expansion device is zero. Similarly, the second expansion device 6 has a passage cross-section adjustable between a minimum value Smin6 and a maximum value Smax6. According to unshown embodiments, the position of the movable shutter of each of the expansion devices can vary discretely within a set of intermediate positions.

[0085] According to one aspect of the invention, the process comprises the following steps: a) determine a temperature Tint of the indoor airflow Fi, b) determine a saturation vapor pressure Ps of the refrigerant corresponding to the temperature Tint of the indoor airflow Fi, c) assign the determined value of the saturation vapor pressure Ps to the predetermined pressure threshold Pmax.

[0086] This Pmax pressure threshold value prevents the refrigerant charge from shifting towards the second heat exchanger 7. The thermal conditioning system can operate stably, without progressive drift in its thermal performance.

[0087] The thermal conditioning system 100 includes a sensor for measuring the temperature of the indoor airflow Fi, not shown. The sensor can be a thermistor, for example, a negative temperature coefficient thermistor. The temperature sensor can also be a thermocouple. The sensor is positioned in the airflow Fi, near the second heat exchanger 7 and preferably upstream of it.

[0088] Adjusting the distribution between the flow rate of refrigerant circulating in the first heat exchanger 5 and the flow rate of refrigerant circulating in the second heat exchanger 7 ensures control of the pressure P1 at the outlet of the first evaporator 5. Thus, according to one embodiment, the process comprises the following steps: d1) reduce the passage cross-section S4 of the first expansion device 4 to a minimum value Smin, e1) increase the passage cross-section S6 of the second expansion device 6 so that a flow of refrigerant fluid passes through the second heat exchanger 7.

[0089] By passing a flow of refrigerant fluid through the second heat exchanger 7, operating conditions allowing evaporation of any refrigerant liquid that may have accumulated in the second heat exchanger 7 are obtained.

[0090] Indeed, the pressure of the refrigerant flow passing through the second heat exchanger 7 is then lower than the saturation pressure Ps of the refrigerant for a temperature equal to the temperature Tint of the indoor airflow Fi. Thus, the liquid refrigerant accumulated in the second heat exchanger 4 evaporates and rejoins the quantity of refrigerant circulating in the refrigerant circuit 1.

[0091] The minimum value Smin of the flow area S4 of the first expansion valve 4 can be zero. In other words, the first expansion valve 4 is then in the closed position, and the refrigerant flow rate in the first evaporator 5 is zero. The cooling of the battery by the first evaporator 5 is then no longer active. By zero flow rate, we mean zero, excluding leaks. The refrigerant flow rate through the first evaporator 5 is thus negligible compared to the refrigerant flow rate through the active heat exchangers of the thermal conditioning system 100. When the only active heat exchanger is the second heat exchanger 7, the system is in passenger compartment air conditioning mode and provides cooling of the airflow Fi inside the passenger compartment. The refrigerant circulation in this operating mode is illustrated in the figure 8 .

[0092] The thermal conditioning system 100 includes a fourth heat exchanger 9 configured to exchange heat with an outside airflow Fe. The thermal conditioning system is configured to circulate the first heat transfer fluid F1 through the fourth heat exchanger 9. The fourth heat exchanger cools the heat transfer fluid circulating in the first heat exchanger 3 by dissipating heat into the outside airflow Fe. The cabin air conditioning mode utilizes this operation. Heat extracted from the interior airflow Fi is rejected into the first heat exchanger 3 and then into the outside airflow Fe at the fourth heat exchanger 9. The fourth heat exchanger 9 is located, for example, in the front of the vehicle, behind the vehicle's grille.The outside airflow Fe thus passes through the vehicle's grille and then performs a heat exchange with the fourth heat exchanger 9. The fourth heat exchanger 9 is connected to the circuit 23, at two connection points 41 and 42.

[0093] According to another example of implementation of the process, the minimum value Smin of the passage section S4 of the first expansion device 4 is between 20% and 50% of a maximum passage section Smax of the first expansion device 4.

[0094] In this case, a flow of refrigerant circulates in the first evaporator 5 and a simultaneous flow of refrigerant circulates in the second heat exchanger 7. As before, the pressure of the refrigerant flow through the second heat exchanger 7 is lower than the saturation pressure Ps(Tint) of the refrigerant corresponding to the ambient temperature Tint. The liquid refrigerant accumulated in the second heat exchanger 7 can thus evaporate and rejoin the quantity of refrigerant circulating in the refrigerant circuit 1. Cooling of the vehicle's powertrain component 30 then remains active, with reduced thermal cooling power. Cooling of the passenger compartment air is ensured simultaneously. This scenario is illustrated in the figure 9Figure 1 schematically represents the evolution over time of the cross-sectional area S4 of the first expansion device 4, the cross-sectional area S6 of the second expansion device 6, and the pressure P1 of the refrigerant at the outlet of the first evaporator 5. At time t0, the pressure P1 is above the maximum permissible pressure threshold Pmax, allowing refrigerant to migrate towards the second heat exchanger 7. At time t1, step ii) of controlling the pressure P1 of the refrigerant at the outlet of the first evaporator 5 is implemented. The cross-sectional area S4 of the first expansion device 4 is reduced, but not eliminated. The cross-sectional area S6 of the second expansion device 6 is increased. The pressure P1 decreases and falls below the predetermined pressure threshold Pmax.

[0095] Controlling the flow rate Q of high-pressure refrigerant supplied by the compression device 2 is another way of ensuring control of the pressure P1 at the outlet of the first evaporator 5. According to another aspect of the process, in which the compression device 2 is of the rotary type, the process includes the step: d2) increase the rotational speed of the compression device 2 up to a value greater than a predetermined speed threshold Nmin.

[0096] An increase in the rotational speed of the compression device, allowing an increase in the flow rate of discharged high-pressure refrigerant, is a way of lowering the pressure of the refrigerant in the first evaporator 5.

[0097] To achieve this, the electric motor driving the moving parts of the compression unit 2 is controlled by the electronic control unit to obtain a set speed. The chosen set speed is higher than the predetermined minimum speed threshold Nmin. This speed ensures a sufficiently high refrigerant flow rate so that the pressure in the first evaporator 5 drops to a sufficiently low value. As a result, the low-pressure refrigerant exiting the first heat exchanger 5 cannot reach the second heat exchanger 7.

[0098] The compression device 2 has a maximum rotational speed Nmax, and the predetermined speed threshold Nmin is greater than 80% of the maximum rotational speed Nmax. The maximum rotational speed Nmax is, for example, 6000 rpm. The predetermined speed that ensures the pressure P1 of the refrigerant at the outlet of the first evaporator 5 is below the predetermined pressure threshold Pmax is, for example, 5000 rpm.

[0099] Controlling the flow cross-section of the first expansion device 4, while allowing the thermal conditioning system 100 to operate in energy recovery mode, is another way to ensure control of the pressure P1 at the outlet of the first evaporator 5. Thus, the process comprises the following steps: d3) decrease the passage cross-section of the first decompression device 4, e3) maintain the passage cross-section of the second decompression device 6 at a value of zero.

[0100] Reducing the cross-sectional area of ​​the first expansion device 4 degrades heat exchange in the first evaporator 5. The temperature, and therefore the pressure, of the refrigerant decreases to maintain the same level of heat exchange in the system. This step of reducing the cross-sectional area of ​​the first expansion device is iterated until the pressure P1 of the refrigerant at the outlet of the first evaporator 5 is below the predetermined pressure threshold Pmax.

[0101] According to one implementation method of the process, step ii) is repeated continuously when the thermal conditioning system 100 is in operation.

[0102] This aspect of the control procedure is particularly applied when the refrigerant circuit does not include any device restricting the flow of refrigerant from the second connection point 12 to the outlet 7b of the second heat exchanger 7. This scenario corresponds to the figures 1 and 2 .

[0103] In other words, the refrigerant pressure P1 at the outlet of the first evaporator 5 is maintained below the predetermined pressure threshold Pmax for the entire duration that the heat conditioning system 100 is operating. This means that the refrigerant pressure P1 at the outlet of the first evaporator 5 can be continuously monitored while the system is running, thus preventing the gradual accumulation of refrigerant in the second heat exchanger 7.

[0104] According to another embodiment of the process, the refrigerant circuit 1 includes a non-return valve 21 disposed on the first branch branch B downstream of the second heat exchanger 7 and upstream of the second connection point 12, the non-return valve 21 being configured to block refrigerant flow from the second connection point 12 to an outlet 7b of the second heat exchanger 7. figure 3 The diagram illustrates this configuration. The non-return valve 21 is a passive component, i.e., without electrical control.

[0105] According to an alternative design not shown, the refrigerant circuit 1 includes a shut-off valve located on the first branch B downstream of the second heat exchanger 7 and upstream of the second connection point 12. The shut-off valve is electrically controlled by the electronic control unit. When the shut-off valve is in the closed position, the flow of refrigerant from the second connection point 12 to the outlet 7b of the second heat exchanger 7 is blocked.

[0106] The control process may include, before step ii), a step: i1) detect an accumulation of refrigerant fluid in the second heat exchanger 7, and step ii) is implemented only if an accumulation of refrigerant fluid in the second heat exchanger 7 is detected in step i1).

[0107] In this embodiment, the check valve 21, or the shut-off valve if used instead of the check valve 21, limits the flow of refrigerant to the second heat exchanger 7. This slows the accumulation of liquid refrigerant compared to a system without any device restricting refrigerant flow to the outlet 7b of the second heat exchanger 7. Consequently, the refrigerant pressure control step at the outlet of the first evaporator 5 can be applied only when necessary. Temporary operation under conditions generating a pressure differential that allows migration and condensation of the refrigerant in the second heat exchanger 7 is acceptable, as the accumulation is then slow.

[0108] The detection of refrigerant accumulation in the second heat exchanger 7 occurs when the system has operated for a sufficient period under conditions where the refrigerant pressure P1 at the outlet of the first evaporator 5 was higher than the saturated vapor pressure corresponding to the temperature of the internal airflow Fi. The applied control step reduces the refrigerant pressure P1 at the outlet of the first evaporator 5 to a value lower than the saturated vapor pressure Ps corresponding to the temperature Tint of the internal airflow Fi, thus allowing the refrigerant, which had previously been liquefied in the second heat exchanger 7, to evaporate.

[0109] According to one aspect of the invention, step ii) is followed by an operating step in a so-called powertrain cooling mode, in which the first heat transfer fluid F1 receives heat from the refrigerant and the second heat transfer fluid F2 releases heat to the refrigerant, and in which the flow of refrigerant through the second heat exchanger 7 is zero. In other words, the evaporation of the refrigerant in the first evaporator 5 absorbs heat from the second heat transfer fluid F2 and cools the component 30 of the vehicle's powertrain, which in this case is an electrical energy storage battery. The second heat exchanger 7 is not thermally active, since no flow of refrigerant circulates through it.

[0110] Powertrain cooling mode operation is reactivated when the accumulated coolant has been vaporized by pressure control in the first evaporator 5. Cooling of the vehicle's powertrain element 30 is thus maximized.

[0111] In other words, when an accumulation of liquid refrigerant is detected, the thermal conditioning system 100 switches to an operating mode that vaporizes the accumulated refrigerant, allowing it to circulate again and participate in heat exchange. When this operating mode is no longer needed because all the accumulated liquid refrigerant has been vaporized, the thermal conditioning system 100 returns to its initial operating mode. The operation of the thermal conditioning system 100 comprises a succession of phases during which the refrigerant accumulates in liquid form, and phases during which the accumulated liquid refrigerant is evaporated through active control of the refrigerant pressure in the first evaporator 5.The operating time during the phase allowing the evaporation of the refrigerant in the second heat exchanger 7 is, for example, on the order of 1 minute for an ambient temperature of -5°C. This phase can be triggered after approximately 2 hours of operation in traction chain cooling mode, during which the pressure in the first evaporator 5 is higher than the saturation pressure Ps corresponding to the air temperature in the vicinity of the second heat exchanger 7.

[0112] We will now describe various means of detecting an excessive accumulation of liquid refrigerant in the second heat exchanger 7.

[0113] According to an example of implementation of the process, step i1) of detecting an accumulation of refrigerant fluid in the second heat exchanger 7 comprises the following substeps: determine a temperature of the second heat transfer fluid F2 at the outlet of the first evaporator 5, if the determined temperature is greater than a first predetermined threshold Th1, detect an accumulation of refrigerant fluid in the second heat exchanger 7.

[0114] Alternatively or in addition, step i1) of detecting an accumulation of refrigerant in the second heat exchanger 7 includes the following sub-steps: determine a rate of change of temperature T2 of the second heat transfer fluid F2 at the outlet of the first evaporator 5, if the determined rate of change is greater than a second predetermined threshold Th2, detect an accumulation of refrigerant in the second heat exchanger 7.

[0115] A too rapid increase in the temperature of the second heat transfer fluid F2 indicates a lack of refrigerant circulating in circuit 1, in other words, an excessive accumulation of liquid refrigerant. Monitoring the temperature of the second heat transfer fluid therefore allows for the detection of refrigerant accumulation in the second heat exchanger 7.

[0116] According to one implementation example, the predetermined threshold Th2 depends on the electrical power of element 30 of the transmission chain. The higher the electrical power, for example the electrical power for charging the battery, the higher the threshold Th2.

[0117] According to one embodiment, in which the thermal conditioning system includes a refrigerant fluid accumulation device 10' disposed on the main loop A downstream of the first heat exchanger 3 and upstream of the first connection point 11, the step of detecting a refrigerant fluid accumulation in the second heat exchanger 7 comprises the following substeps: determine a superheat value sh of the refrigerant at the outlet of the first evaporator 5, if the determined superheat sh is greater than a third predetermined threshold Th3, detect an accumulation of refrigerant in the second heat exchanger 7.

[0118] When the design of the air conditioning system allows for superheating of the refrigerant entering the compression unit, excessive superheat indicates a lack of refrigerant circulating in the circuit. The superheat, sh, is equal, by definition, to the difference between the actual temperature of the refrigerant at the outlet of the first evaporator 5 and the condensation temperature of the refrigerant at the pressure prevailing in the first evaporator 5. This design is illustrated in particular in the... Figures 1 And 3 .

[0119] According to another embodiment, in which the thermal conditioning system includes a refrigerant fluid accumulation device 10 disposed on the main loop A downstream of the second connection point 12 and upstream of the compression device 2, the step of detecting a refrigerant fluid accumulation in the second heat exchanger 7 comprises the following substeps: determine a subcooling value sc of the refrigerant at the inlet of the first expansion device 4, if the determined subcooling sc is less than a fourth predetermined threshold Th4, detect an accumulation of refrigerant in the second heat exchanger 7.

[0120] When the air conditioning system architecture allows for subcooling of the refrigerant at the outlet of the first heat exchanger, i.e., at the inlet of the first expansion device, a subcooling value that is too low indicates a lack of refrigerant in the circuit. The subcooling value sc is, by definition, equal to the difference between the actual temperature of the refrigerant at the inlet of the first expansion device 4 and the condensation temperature of the refrigerant at the pressure prevailing at the inlet of the first expansion device 4. This architecture is illustrated in the figure 2 .

[0121] Once an excessive accumulation of refrigerant in the second heat exchanger 7 is detected, step ii) of pressure control at the outlet of the first evaporator 5 is activated in order to cause the evaporation of the accumulated refrigerant.

[0122] According to one implementation method of the process, step ii) of controlling the pressure P1 of the refrigerant fluid at the outlet of the first evaporator 5 is applied for a predetermined duration Dapp.

[0123] According to one implementation example, the predetermined duration Dapp depends on the temperature of the indoor airflow Fi.

[0124] According to another example of implementation, the process involves the following steps: a) determine a temperature Tint of the indoor airflow Fi, b) determine a saturation vapor pressure Ps of the refrigerant for the determined value of the temperature Tint of the indoor airflow Fi, c) determine the difference between the saturation vapor pressure Ps of the refrigerant for the determined value of the temperature Tint of the indoor airflow Fi and the predetermined threshold Pmax, and the predetermined duration Dapp depends on the difference determined in step c).

[0125] The duration of the pressure control phase, allowing the evaporation of the refrigerant in the second heat exchanger 7, is for example on the order of 1 minute for an internal airflow temperature Fi of the order of -5°C.

[0126] The described process can be applied to thermal conditioning system architectures incorporating additional heat exchangers. figure 3 and the figure 4They illustrate such a configuration.

[0127] In one embodiment, the thermal conditioning system comprises a second branch C connecting a third connection point 13 located on the main loop A downstream of the first connection point 11 and upstream of the first expansion device 4 to a fourth connection point 14 located on the main loop A downstream of the first evaporator 5 and upstream of the second connection point 12. The second branch C includes a third expansion device 18 and a third heat exchanger 19 configured to exchange heat with an outside airflow Fe to a passenger compartment of the motor vehicle. The fourth heat exchanger 9 is located upstream, in the direction of flow of the outside airflow Fe, of the third heat exchanger 19.

[0128] The third heat exchanger 19 enables operation in heat pump mode. In other words, the heat required for the vaporization of the refrigerant in the third heat exchanger 19 is extracted from the outside airflow Fe and transferred to the inside airflow Fi in the passenger compartment. This transfer can be carried out directly or indirectly via the first heat transfer fluid F1.

[0129] Depending on the method of implementation of figures 3 and 4The thermal conditioning system 100 includes an internal heat exchanger 31 arranged jointly on the main loop A downstream of the first heat exchanger 3 and upstream of the first connection point 11, and on the main loop A downstream of the second connection point 12 and upstream of the compression device 2. The internal heat exchanger 31 increases the enthalpy change of the refrigerant during the thermodynamic cycle and improves the efficiency of the system.

[0130] The internal heat exchanger 31 has a first heat exchange section 31a located on the main loop downstream of the first heat exchanger 3 and upstream of the first connection point 11. The internal heat exchanger 31 has a second heat exchange section 31b also located on the main loop A downstream of the second connection point 12 and upstream of the compression device 2. The internal heat exchanger 31 is configured to allow heat exchange between the refrigerant in the first heat exchange section 31a and the refrigerant in the second heat exchange section 31b.

[0131] According to another implementation example, the process includes the steps: - Heat the internal airflow Fi so that the pressure P1 of the refrigerant fluid at the outlet of the first evaporator 5 is less than a predetermined threshold Pmax.

[0132] By heating the air surrounding the second heat exchanger 7, which is in this case the passenger compartment evaporator, this evaporator 7 ceases to be a cold point in the refrigerant circuit, a cold point where the refrigerant is likely to accumulate in a liquid state. In other words, heating the airflow near the second heat exchanger 7 allows the pressure value corresponding to point A7b on the figure 5This is done to reduce and gradually eliminate the pressure differential between point A5 and point A7b. Indeed, increasing the temperature of the internal airflow near the second heat exchanger 7 raises the saturated vapor pressure in the second heat exchanger 7. The maximum allowable pressure threshold Pmax thus takes on a higher value when the air surrounding the second heat exchanger 7 is heated than when the air surrounding the second heat exchanger 7 is not heated. The threshold Pmax can, for example, be taken as equal to the condensation pressure of the refrigerant at the temperature corresponding to the temperature of the air surrounding the second heat exchanger 7.

[0133] According to an example of implementation of the process, the thermal conditioning system 100 includes an electric heating device 20, and the heating of the indoor airflow Fi is achieved by activating an electric heating device 20.

[0134] The electric heating device 20 is, for example, a heating element. The electric heating device 20 is positioned near the second heat exchanger 7 so as to locally increase the temperature of the environment surrounding the second heat exchanger 20. In the figures, the electric heating device 20 is positioned upstream of the third heat exchanger 8. According to an alternative configuration not shown, the electric heating device 20 can be positioned downstream of the third heat exchanger 8. It is not necessary to heat the entire vehicle interior. The flow rate of the interior airflow Fi is then zero or limited to a very low value, so as not to dissipate the heat from the heating device 20 throughout the vehicle interior.

[0135] The process therefore includes the following step: Activate the electric heating device 20 for a predetermined time.

[0136] Alternatively or in addition, the process may include the following steps: operate the thermal conditioning system in a so-called energy recovery mode in which the first heat transfer fluid F1 receives heat from the refrigerant and the second heat transfer fluid F2 gives heat to the refrigerant, to heat the indoor airflow Fi, control the flow rate of the indoor airflow Fi to a value below a predetermined threshold.

[0137] The first heat transfer fluid F1 heats the interior airflow Fi via the third heat exchanger 8. This step is applied before the climate control system operates in battery cooling mode. This step increases the temperature near the second heat exchanger 7 to prevent it from becoming a cold spot during the battery cooling phase. By using heat extracted from the battery 30 to heat the passenger compartment, the power supplied by the heater 20 can be reduced, or in some cases completely eliminated. This step also cools the battery before or at the start of a charging phase. This cooling preconditions the battery before a fast charging phase.Indeed, in the case of fast charging under high electrical power, it can be difficult to maintain the battery at its set temperature throughout the charging process, as the heat to be dissipated may exceed the maximum power that the first evaporator 5 can dissipate. Ensuring battery cooling before fast charging begins allows for better temperature control at the end of the charging cycle.

[0138] According to one embodiment, the thermal conditioning system includes a movable flap 26 configured to regulate a recirculation rate of the indoor airflow Fi, and the method includes the step: control the position of the movable flap 26 so that the recirculation rate of the indoor airflow Fi is greater than a predetermined threshold Fmax.

[0139] The movable flap 26 allows adjustment of the amount of outside air that can reach the vehicle's passenger compartment. When the flap 26 is in a position that blocks the entry of fresh air from outside the vehicle, the interior airflow Fi consists entirely of recirculated air. Conversely, the movable flap 26 can be positioned to maximize the flow of outside air entering the passenger compartment. The position of the flap 26 is continuously adjustable between these two extreme positions.

[0140] By keeping the air renewal in the passenger compartment at a low value, i.e. by minimizing the supply of fresh air, the energy required to maintain the temperature in the vicinity of the second heat exchanger 7 is reduced.

[0141] According to one implementation variant, the predetermined threshold Fmax of the indoor airflow recirculation rate Fi is constant.

[0142] According to another implementation variant, the process includes the step: detect the presence of at least one occupant in the vehicle's passenger compartment; if the presence of at least one occupant is detected, assign a first value Fmax1 to the predetermined threshold Fmax of the recirculation rate of the interior airflow Fi; otherwise, assign a second value Fmax2 to the predetermined threshold Fmax of the recirculation rate of the interior airflow Fi, the second value Fmax2 being greater than the first value Fmax1.

[0143] The first value Fmax1 of the predetermined threshold Fmax of the indoor airflow recirculation rate Fi is between 10% and 60%. The second value Fmax2 of the predetermined threshold Fmax of the indoor airflow recirculation rate Fi is between 60% and 100%.

[0144] When at least one occupant is detected, a minimum level of air exchange in the passenger compartment must be maintained to ensure healthy cabin air quality. Conversely, when no occupants are detected in the vehicle, the need for air exchange is lower, and the outside air intake can be minimal, thus retaining heat in the passenger compartment. The energy required to maintain a sufficient temperature near the second heat exchanger 7 to prevent refrigerant migration can therefore be reduced when the vehicle is unoccupied. This scenario corresponds to the situation where the occupants have left the vehicle while the battery is charging. The vehicle's energy efficiency is thus improved.

[0145] The presence of at least one occupant in the vehicle is detected, for example, based on the response of pressure sensors located in the vehicle's seats.

Claims

1. Method for controlling a thermal conditioning system (100), the thermal conditioning system (100) comprising a refrigerant fluid circuit (1) configured to circulate a refrigerant fluid, the refrigerant fluid circuit (1) comprising: - A main loop (A) comprising successively in the direction of circulation of the refrigerant fluid: - A compression device (2), - A first heat exchanger (3) configured to exchange heat with a first heat transfer fluid (F1), - A first expansion device (4), - A first evaporator (5) configured to exchange heat with an element (30) of a drivetrain of a motor vehicle via a second heat transfer fluid (F2), - A first bypass branch (B) connecting a first connection point (11) arranged on the main loop (A) downstream of the first heat exchanger (3) and upstream of the first expansion device (4) to a second connection point (12) arranged on the main loop (A) downstream of the first evaporator (5) and upstream of the compression device (2), the first bypass branch (B) comprising a second expansion device (6) and a second heat exchanger (7) configured to exchange heat with an interior air flow (Fi) to a passenger compartment of the motor vehicle, the thermal conditioning system being configured to operate according to an operating mode referred to as drivetrain cooling mode in which the first heat transfer fluid (F1) receives heat from the refrigerant fluid and the second heat transfer fluid (F2) transfers heat to the refrigerant fluid, and in which a flow rate of refrigerant fluid through the second heat exchanger (7) is zero, the method - being characterised in that it comprises - comprising the steps: - a) determining a temperature (Tint) of the interior air flow (Fi), - b) determining a saturated vapour pressure (Ps) of the refrigerant fluid corresponding to the temperature (Tint) of the interior air flow (Fi), - i) determining a pressure (P1) of the refrigerant fluid at the outlet of the first evaporator (5), - ii) controlling, as a function of the determined pressure (P1), at least one parameter among the following parameters: passage cross-section (S4) of the first expansion device (4), passage cross-section (S5) of the second expansion device (6), flow rate (Q) of refrigerant fluid supplied by the compression device (2), temperature (T1) or interior air flow (Fi), so that the pressure (P1) of the refrigerant fluid at the outlet of the first evaporator (5) is lower than the determined value of the saturated vapour pressure (Ps).

2. Method according to Claim 1, comprising the steps: - d1) reducing the passage cross-section (S4) of the first expansion device (4) to a minimum value (Smin). - e1) increasing the passage cross-section (S6) of the second expansion device (6) so that a flow rate of refrigerant fluid passes through the second heat exchanger (7).

3. Method according to one of the preceding claims, wherein step ii) is repeated continuously when the thermal conditioning system (100) is in operation.

4. Method according to one of Claims 1 or 2 wherein the refrigerant fluid circuit (1) comprises a non-return valve (21) arranged on the first bypass branch (B) downstream of the second heat exchanger (7) and upstream of the second connection point (12), the non-return valve (21) being configured to block a circulation of the refrigerant fluid from the second connection point (12) towards an outlet (B) of the second heat exchanger (7).

5. Method according to one of Claims 1 or 2 - comprising the step: - i) detecting an accumulation of refrigerant fluid in the second heat exchanger (7), and wherein step ii) is implemented only if an accumulation of refrigerant fluid in the second heat exchanger (7) is detected in step i).

6. Method according to Claim 5, wherein the thermal conditioning system comprises a refrigerant fluid accumulation device (10') arranged on the main loop (A) downstream of the first heat exchanger (3) and upstream of the first connection point (11), and wherein the step of detecting an accumulation of refrigerant fluid in the second heat exchanger (7) comprises the sub-steps: - determining a superheat value (sh) of the refrigerant fluid at the outlet of the first evaporator (5), - if the determined superheat (sh) is greater than a third predetermined threshold (Th3), detecting an accumulation of refrigerant fluid in the second heat exchanger (7).

7. Method according to Claim 5, wherein the thermal conditioning system comprises a refrigerant fluid accumulation device (10) arranged on the main loop (A) downstream of the second connection point (12) and upstream of the compression device (2), and wherein the step of detecting an accumulation of refrigerant fluid in the second heat exchanger (7) comprises the sub-steps: - determining a subcooling value (sc) of the refrigerant fluid at the inlet of the first expansion device (4), - if the determined subcooling (sc) is lower than a fourth predetermined threshold (Th4), detecting an accumulation of refrigerant fluid in the second heat exchanger (7).

8. Method according to one of the preceding claims, comprising the steps: - Heating the interior air flow (Fi) so that the pressure (P1) of the refrigerant fluid at the outlet of the first evaporator (5) is lower than a predetermined threshold (Pmax).

9. Method according to the preceding claim, wherein the thermal conditioning system (100) comprises an electric heating device (20), and wherein the heating of the interior air flow (Fi) is carried out by the activation of an electric heating device (20).

10. Method according to Claim 8 or 9, comprising the steps: - operating the thermal conditioning system according to a mode referred to as energy recovery mode in which the first heat transfer fluid (F1) receives heat from the refrigerant fluid and the second heat transfer fluid (F2) transfers heat to the refrigerant fluid, in order to heat the interior air flow (Fi), - controlling the flow rate of the interior air flow (Fi) to a value lower than a predetermined threshold.

11. Method according to the preceding claim, wherein the thermal conditioning system comprises a movable flap (26) configured to adjust a recirculation rate of the interior air flow (Fi), wherein the method comprises the step: - controlling the position of the movable flap (26) so that the recirculation rate of the interior air flow (Fi) is greater than a predetermined threshold (Fmax).

12. Method according to the preceding claim, comprising the step: - detecting the presence of at least one occupant in the passenger compartment of the vehicle, - if the presence of at least one occupant is detected, assigning a first value (Fmax1) to the predetermined threshold (Fmax) of the recirculation rate of the interior air flow (Fi), - otherwise assigning a second value (Fmax2) to the predetermined threshold (Fmax) of the recirculation rate of the interior air flow (Fi), the second value (Fmax2) being greater than the first value (Fmax1).