Method for managing a thermal management circuit for an electric or hybrid vehicle

Abstract

The invention relates to a method for managing a thermal management circuit (1) for an electric or hybrid motor vehicle, the management method being configured to control the thermal management circuit (1) in a first operating mode with priority cooling of the batteries. In the management method, a compressor (2) is configured to control the temperature of the air flow (X) intended for the passenger compartment at the outlet of a first heat exchanger (5) so as to reach and maintain a target temperature, a first expansion device (4) is configured to control the pressure of the refrigerant at the outlet of a radiator (3) so as to reach and maintain an optimised operating pressure, and a second expansion device (7) is configured to control the temperature of the heat transfer fluid at the outlet of a second heat exchanger (8) so as to reach and maintain a target temperature, while monitoring the overheating of the refrigerant at the outlet of the second heat exchanger (8) so as to reach and maintain overheating of between 3° and 5°C.

Description

Description Title of the invention: Method for managing a thermal management circuit for an electric or hybrid vehicle

[0001] The invention relates to the field of electric and hybrid motor vehicles and more particularly to a method of managing a thermal management circuit for the passenger compartment as well as the batteries of such a motor vehicle.

[0002] Modern electric and hybrid vehicles increasingly incorporate thermal management systems for both the batteries and the passenger compartment. For batteries to operate at peak efficiency, they must remain within an optimal temperature range. Therefore, it is necessary to cool them during use to prevent them from exceeding this optimal operating temperature. Similarly, it may also be necessary to heat them, for example in cold weather, to ensure they reach this optimal operating temperature as quickly as possible. The ability to heat or cool the passenger compartment is also crucial for ensuring passenger comfort.

[0003] H is known for its efficient thermal management of batteries and the passenger compartment, utilizing refrigerant circuits with one or more expansion valves and heat exchangers. However, when using such a thermal management circuit to control both battery and passenger compartment temperatures, priority may be given to either the batteries or the passenger compartment depending on various parameters. For example, priority may be given to the passenger compartment while driving, while priority may be given to the batteries during charging, particularly during rapid charging, which generates heat.

[0004] Generally, cooling priority is given to the batteries when their cooling requirements exceed those of the passenger compartment. Conversely, cooling priority is given to the passenger compartment when its cooling requirements exceed those of the batteries. If these conditions are not met, the subcooling at the outlet of an external heat exchanger may be insufficient, thus reducing the efficiency of the thermal management system. The precise moment for switching between priorities is therefore crucial and complex to determine in order to avoid compromising the efficiency of the thermal management system.

[0005] One of the aims of the present invention is therefore to remedy at least partially the disadvantages of the prior art and to propose an improved method of managing a thermal management circuit.

[0006] The present invention therefore relates to a method for managing a thermal management circuit for an electric or hybrid motor vehicle, said thermal management circuit comprising: - a main loop comprising, in the direction of refrigerant flow, a compressor, a radiator, a first expansion device, a first heat exchanger configured to exchange heat directly or indirectly with an airflow destined for of the passenger compartment and a refrigerant accumulator, - a bypass branch connecting the refrigerant outlet of the radiator to the refrigerant inlet of the refrigerant accumulator, said bypass branch comprising, in the direction of refrigerant flow, a second expansion device and a second heat exchanger configured to exchange with the vehicle's batteries via a heat transfer fluid circuit, the first expansion device, the second expansion device and the compressor being connected to a control unit, said thermal management method being configured to control the thermal management circuit in a first operating mode with priority cooling of the batteries, in which the refrigerant flows successively through the compressor and the radiator,a first part of the refrigerant fluid passing through the first expansion device where it undergoes a pressure loss and the first heat exchanger before reaching the refrigerant accumulator, a second part of the refrigerant fluid passing through the bypass branch and through the second expansion device where it undergoes a pressure loss and the second heat exchanger before reaching the refrigerant accumulator, in said management process, the compressor is configured to control the temperature of the airflow to the passenger compartment at the outlet of the first heat exchanger so as to reach and maintain a target temperature,The second expansion device is configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger so as to reach and maintain a target temperature while monitoring the superheat of the refrigerant fluid at the outlet of the second heat exchanger so as to reach and maintain a superheat between 3° and 5°C.

[0007] According to one aspect of the invention, the thermal management method is configured to control the thermal management circuit in a first operating mode with priority cooling of the passenger compartment, in which the refrigerant circulates successively in the compressor and the radiator, a first part of the refrigerant passing through the first expansion device where it undergoes a pressure loss and the first heat exchanger before reaching the refrigerant accumulator, a second part of the refrigerant passing through the bypass branch and through the second expansion device where it undergoes a pressure loss and the second heat exchanger before reaching the refrigerant accumulator, in said management method,The compressor is configured to control the temperature of the airflow to the passenger compartment at the outlet of the first heat exchanger so as to reach and maintain a target temperature, the second expansion device being configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger so as to reach and maintain a target temperature of said heat transfer fluid at the outlet of the second heat exchanger. while monitoring the superheat of the refrigerant fluid at the outlet of the second heat exchanger so as to achieve and maintain a superheat greater than or equal to 5 °C.

[0008] According to another aspect of the invention, the first expansion device is configured to control the pressure of the refrigerant fluid at the outlet of the radiator so as to achieve and maintain an optimized operating pressure or to achieve an optimized subcooling at the outlet of the radiator.

[0009] According to another aspect of the invention, the thermal management circuit comprises, connected to the control unit: - a temperature sensor for the refrigerant fluid located at the outlet of the second heat exchanger, - a refrigerant pressure sensor located between the outlet of the second heat exchanger and the compressor inlet, - a temperature sensor for the refrigerant fluid at the inlet of the accumulator; the superheat of the refrigerant fluid at the outlet of the second heat exchanger is calculated based on: - the theoretical saturation temperature of the refrigerant at the pressure measured by the refrigerant pressure sensor between the outlet of the second heat exchanger and the compressor inlet, and - the temperature measured by the refrigerant temperature sensor at the outlet of the second heat exchanger.

[0010] According to another aspect of the invention, the thermal management method is configured to control the thermal management circuit in a second cabin cooling operating mode, in which the refrigerant circulates successively through the compressor and the radiator, the first expansion device where it undergoes a pressure loss and the first heat exchanger before reaching the refrigerant accumulator; in said management method, the compressor is configured to control the temperature of the airflow to the cabin at the outlet of the first heat exchanger so as to reach and maintain a target temperature; the first expansion device is configured to control the pressure of the refrigerant at the outlet of the radiator so as to reach and maintain an optimized operating pressure.

[0011] According to another aspect of the invention, the control and command of the thermal management circuit is continuous from one operating mode to another and from one cooling priority to another.

[0012] According to another aspect of the invention, if the temperature of the refrigerant at the outlet of the compressor is greater than or equal to a maximum value, or if the maximum rotational speed of the compressor is reached, then the first expansion device reduces the pressure loss of the refrigerant passing through it.

[0013] According to another aspect of the invention, the thermal management circuit includes a temperature sensor of the refrigerant fluid at the outlet of the compressor connected to the control unit.

[0014] According to another aspect of the invention, if overheating occurs at the refrigerant inlet of the accumulator, or if the high pressure of the refrigerant reaches a maximum value, then the first expansion device reduces the pressure loss of the refrigerant passing through it.

[0015] According to another aspect of the invention, the thermal management circuit includes a refrigerant fluid pressure sensor at the outlet of the radiator, said pressure sensor being connected to the control unit.

[0016] According to another aspect of the invention, the thermal management circuit includes a temperature sensor disposed in the airflow to the passenger compartment at the outlet of the first heat exchanger, said temperature sensor being connected to the control unit.

[0017] According to another aspect of the invention, the thermal management circuit includes a temperature sensor for the heat transfer fluid of the heat transfer fluid circuit at the outlet of the second heat exchanger, said temperature sensor being connected to the control unit.

[0018] According to another aspect of the invention, the thermal management circuit includes a temperature sensor for the refrigerant fluid at the outlet of the radiator, said temperature sensor being connected to the control unit.

[0019] Other features and advantages of the present invention will become more apparent upon reading the following description, provided by way of illustration and not limitation, and the accompanying drawings in which:

[0020] [Fig 1] Figure 1 is a schematic representation of a cooling circuit within a thermal management circuit,

[0021] [Fig 2] Figure 2 is a schematic representation of the cooling circuit elements connected to a control unit,

[0022] [Fig 3] Figure 3 is a schematic representation of a cooling circuit of the thermal management circuit according to a first operating mode,

[0023] [Fig 4] Figure 4 is a schematic representation of a cooling circuit of the thermal management circuit according to a second operating mode,

[0024] [Fig 5] Figure 5 is a schematic representation of a cooling circuit of the thermal management circuit according to a third operating mode.

[0025] In the different figures, identical elements bear the same reference numbers.

[0026] The following are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0027] In this description, certain elements or parameters can be indexed, such as first element or second element, first parameter and second parameter, first criterion and second criterion, etc. In this case, it is simply indexing to differentiate and name similar but not identical elements, parameters, or criteria. This indexing does not imply any priority for an element. A parameter or criterion is defined in relation to another, and such designations can easily be interchanged without departing from the scope of this description. This indexing also does not imply a chronological order, for example, for evaluating one criterion over another.

[0028] In this description, "upstream" means that an element is positioned before another in relation to the direction of fluid flow. Conversely, "downstream" means that an element is positioned after another in relation to the direction of fluid flow.

[0029] Figure 1 shows a thermal management system for an electric or hybrid motor vehicle comprising a thermal management circuit 1 through which a refrigerant is intended to circulate. This refrigerant could, for example, be R744.

[0030] The thermal management circuit 1 comprises a main loop A and a branch branch B.

[0031] The main loop A includes, in the direction of circulation of a refrigerant fluid, a compressor 2, a radiator 3, a first expansion device 4, a first heat exchanger 5 configured to exchange directly or indirectly with an airflow X destined for the passenger compartment and a refrigerant fluid accumulator 6.

[0032] The radiator 3 may in particular be an evaporative condenser or a gas evaporative cooler placed on the vehicle so as to be traversed by an external airflow, for example at the front.

[0033] The first heat exchanger 5 can be an evaporator, for example, located within a heating, ventilation, and air conditioning (HVAC) system. This first heat exchanger 5 is also designed to carry an airflow X destined for the vehicle's passenger compartment.

[0034] The main branch A may also include an internal heat exchanger 9. The internal heat exchanger 9 is specifically configured to allow heat exchange between the high-pressure refrigerant from the radiator 3 and the low-pressure refrigerant towards the compression device 2. This internal heat exchanger 9 notably improves the coefficient of performance of the thermal management device 1.

[0035] The first internal heat exchanger 9 is, in the example illustrated in Figure 1, located on the main loop A, downstream of the radiator 3 with regard to its high pressure part and, also on the main loop A, upstream of the low pressure refrigerant inlet of the compression device 2 with regard to its low pressure part, more particularly downstream of the refrigerant accumulator 6.

[0036] Branch B connects the coolant outlet of the radiator 3 to the coolant inlet of the coolant accumulator 6. Branch B includes, in the direction of coolant flow, a second expansion device 7 and a second heat exchanger 8 configured to exchange with the motor vehicle batteries via a heat transfer fluid circuit Y.

[0037] Branch B thus connects a first connection point 20a to a second connection point 20b. The first connection point 20a is located on the Main loop A downstream of the refrigerant outlet of radiator 3, between said refrigerant outlet of radiator 3 and the first expansion device 4. In the example illustrated in Figure 1, the first connection point 20a is located downstream of the high-pressure section of the internal heat exchanger 9. The second connection point 20b is located on the main loop A, downstream of the first heat exchanger 5, between said first heat exchanger 5 and the compressor 2. More specifically, the second connection point 20b is located upstream of the refrigerant accumulator 6.

[0038] The second heat exchanger 8 can be configured to thermally regulate the vehicle's batteries. This second heat exchanger 8 is thermally connected to a heat transfer fluid circuit Y, which is itself configured to thermally manage the batteries. This heat transfer fluid circuit Y can circulate, in particular, a heat transfer fluid such as water or glycol water.

[0039] The thermal management circuit 1 also includes a first refrigerant redirection device 4, 7 towards the first heat exchanger 5 and / or towards the bypass branch B. In the example illustrated in Figure 1, this first redirection device is composed of the first 4 and second 7 expansion devices which include in particular a stop function blocking the circulation of the refrigerant when they are closed. Other embodiments of this first redirection device 4, 7 can also be envisaged such as for example a three-way valve disposed on the first connection point 20a of the branch branch B.

[0040] The thermal management circuit 1 may also include a non-return valve 10 located on the main branch A upstream of the second connection point 20b. This non-return valve 10 is specifically configured to prevent backflow of heat transfer fluid from the bypass branch B towards the first heat exchanger 5.

[0041] As shown in Figure 2, the first expansion device 4, the second expansion device 7 and the compressor 2 are connected to a control unit U in order to control the openings of the first 4 and second 7 expansion devices respectively and to control the rotation speed of the compressor 2.

[0042] The thermal management circuit 1 may also include, connected to the control unit U, various pressure and temperature sensors of the refrigerant fluid as well as the heat transfer fluid.

[0043] This control unit U can notably be an electronic unit, for example linked to the electronic control unit (ECU) of the motor vehicle.

[0044] The thermal management circuit 1 can thus include a temperature sensor Tl of the refrigerant, located at the outlet of the second heat exchanger 8. More particularly, this temperature sensor Tl is located on the branch branch B downstream of the second heat exchanger 8, between said second heat exchanger 8 and the second connection point 20b of the branch branch B.

[0045] The thermal management circuit 1 may include a refrigerant pressure sensor PI located between the outlet of the second heat exchanger 8 and the inlet of the compressor 2. More In particular, this PI pressure sensor can be disposed on the main branch A upstream of the refrigerant accumulator 6, between the second connection point 20b of the branch B and said refrigerant accumulator 6.

[0046] The thermal management circuit 1 may also include a temperature sensor T2 of the refrigerant fluid at the inlet of the accumulator 6. More particularly, this temperature sensor T2 may be disposed on the main branch A upstream of the refrigerant fluid accumulator 6, between the second connection point 20b of the branch branch B and said refrigerant fluid accumulator 6.

[0047] The pressure sensor PI and the temperature sensor T2 can advantageously be placed in the same location on the main branch A and in particular be combined into a single pressure / temperature sensor.

[0048] The thermal management circuit 1 may also include a temperature sensor T3 of the refrigerant at the outlet of the compressor 2. More specifically, this temperature sensor T3 is located on the main branch A, downstream of the compressor 2, between said compressor 2 and the radiator 3.

[0049] The thermal management circuit 1 may also include a pressure sensor P2 of the refrigerant fluid at the outlet of the radiator 3. More specifically, this pressure sensor P2 is located on the main branch A, downstream of the radiator 3, between said radiator 3 and the high pressure part of the internal heat exchanger 9.

[0050] The thermal management circuit 1 may include a temperature sensor T4 located in the airflow X to the passenger compartment at the outlet of the first heat exchanger 5.

[0051] The thermal management circuit 1 may include a temperature sensor T5 of the heat transfer fluid of the heat transfer fluid circuit Y at the outlet of the second heat exchanger 8. More specifically, this temperature sensor T5 is located on the heat transfer fluid circuit Y downstream of the second heat exchanger 8.

[0052] The thermal management circuit 1 may include a temperature sensor T6 of the refrigerant at the outlet of the radiator 3. More specifically, this temperature sensor T6 is located on the main branch A, downstream of the radiator 3, between said radiator 3 and the high-pressure part of the internal heat exchanger 9.

[0053] The pressure sensor P2 and the temperature sensor T6 can advantageously be placed in the same location on the main branch A and in particular be combined into a single pressure / temperature sensor.

[0054] Other more complex architectures of the thermal management circuit 1 can be imagined, in particular to add specific operating modes such as a heat pump mode.

[0055] Figures 2 to 4 illustrate the different operating modes of the thermal management circuit 1. In these figures, arrows indicate the direction of refrigerant flow. Active pipes and components are shown with solid lines, while inactive pipes and components are shown with dashed lines.

[0056] First mode of operation:

[0057] The thermal management circuit 1 can be configured to operate in a first operating mode illustrated in Figure 3, in which the refrigerant is compressed by the compressor 2 and then circulates through the radiator 3. As it passes through the radiator 3, the refrigerant releases heat energy, for example to the external airflow.

[0058] A first part of the refrigerant then passes through the first expansion device 4 and undergoes a pressure loss to reach a low pressure before passing through the first heat exchanger 5. While passing through the first heat exchanger 5, the refrigerant absorbs heat energy, for example from the internal airflow, by cooling the latter.

[0059] At the outlet of the radiator 3, a second part of the refrigerant passes into the bypass branch B, passes through the second expansion device 7 and undergoes a pressure loss to reach low pressure before passing through the second heat exchanger 8. While passing through the second heat exchanger 8, the refrigerant absorbs heat energy, notably from the heat transfer fluid circulating in the heat transfer fluid circuit Y.

[0060] The refrigerant fluid from both the first heat exchanger 5 and the bypass branch B then joins the refrigerant accumulator 6 and the compressor 2.

[0061] If the internal heat exchanger 9 is present, its high-pressure part is traversed by high-pressure refrigerant from the radiator 3 and its low-pressure part is traversed by low-pressure refrigerant from the refrigerant accumulator 6.

[0062] This first operating mode allows for the cooling of the internal airflow passing through the first heat exchanger 5, for example, to cool the passenger compartment of the motor vehicle, as well as the cooling of the heat transfer fluid in the heat transfer fluid circuit Y passing through the second heat exchanger 8, for example, to cool the vehicle's batteries. Excess heat energy from the refrigerant is dissipated into the outside air via the radiator 3.

[0063] In this first mode of operation, the first redirection device 4, 7 allows both the circulation of the refrigerant fluid from the radiator 3 towards the bypass branch B and towards the first heat exchanger 5.

[0064] According to this first mode of operation, cooling priority can be given to the cooling of the batteries, that is to say that the cooling power is mainly devoted to the heat exchanges of the second heat exchanger 8 and only partly to the heat exchanges of the first heat exchanger 5.

[0065] In this scenario where cooling is prioritized for the batteries, the thermal management circuit 1 is configured so that the compressor 2 is set to control the temperature of the airflow X to the passenger compartment at the outlet of the first heat exchanger 5 in order to reach and maintain a target temperature. This target temperature is determined, in particular, by the passenger compartment temperature setpoint desired by the user. The temperature of the airflow X can be measured by the temperature sensor T4.

[0066] The first expansion device 4 can be configured to control the refrigerant pressure at the outlet of the radiator 3 in order to achieve and maintain an optimized operating pressure, that is, within a pressure range around the optimal operating pressure. This pressure can be measured for monitoring purposes by the pressure sensor P2. This optimized operating pressure is determined according to tables, notably those established by the manufacturer based on tests. This is particularly relevant for a supercritical refrigerant such as R744a.

[0067] Alternatively, the first expansion device 4 can be configured to control the refrigerant pressure at the outlet of the radiator 3 in order to achieve optimized subcooling at the outlet of the radiator 3, i.e., within a subcooling range around an optimal operating subcooling level. This optimized subcooling is determined according to tables, notably those established by the manufacturer based on tests. This is particularly relevant for a subcritical refrigerant such as RL234YF.

[0068] The subcooling at the outlet of radiator 3 corresponds in particular to the subtraction of the temperature of the refrigerant at the outlet of radiator 3, measured by the temperature sensor T6 with the theoretical saturation temperature of the refrigerant at the pressure at the outlet of radiator 3, measured by the pressure sensor P2.

[0069] The second expansion device 7 is configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger 8 in order to reach and maintain a target temperature, while simultaneously monitoring the superheat of the refrigerant at the outlet of the second heat exchanger 8 to achieve and maintain a superheat between 3° and 5°C. This target temperature can be determined, in particular, to maintain the coils within a temperature range in which their performance is adequate. The temperature of the heat transfer fluid at the outlet of the second heat exchanger 8 can be measured by the temperature sensor T5.

[0070] The superheating of the refrigerant at the outlet of the second heat exchanger 8 corresponds in particular to the subtraction of the temperature of the refrigerant at the outlet of the second heat exchanger 8 from the theoretical saturation temperature of the refrigerant at the pressure at the outlet of the second heat exchanger 8.

[0071] The superheat of the refrigerant at the outlet of the second heat exchanger 8 can thus be calculated as a function of: - the theoretical saturation temperature of the refrigerant at the pressure measured by the PI pressure sensor of the refrigerant between the outlet of the second heat exchanger 8 and the inlet of the compressor 2, and - the temperature measured by the temperature sensor Tl of the refrigerant at the outlet of the second heat exchanger 8.

[0072] In the case where the pressure sensor PI is located far from the second heat exchanger 8, for example if it is positioned on the main branch downstream of the accumulator 6 or the low-pressure section of the internal heat exchanger 9, an estimate of the outlet pressure of the second heat exchanger 8 can be made as a function of forecasts of refrigerant pressure losses caused by this distance and the elements between the second heat exchanger 8 and the pressure sensor PI.

[0073] According to this first mode of operation, the priority of cooling can instead be given to the cooling of the passenger compartment, that is to say that the cooling power is mainly devoted to the heat exchanges of the first heat exchanger 5 and only partly to the heat exchanges of the second heat exchanger 8.

[0074] In this scenario where cooling priority is given to the passenger compartment, the thermal management circuit 1 is configured so that the compressor 2 is set to control the temperature of the airflow X destined for the passenger compartment, exiting the first heat exchanger 5, in order to reach and maintain a target temperature. This target temperature is determined, in particular, by the passenger compartment temperature setpoint desired by the user. The temperature of the airflow X can be measured by the temperature sensor T4.

[0075] The first expansion valve 4 is configured to control the refrigerant pressure at the outlet of the radiator 3 in order to achieve and maintain an optimized operating pressure, i.e., within a pressure range around the optimal operating pressure. This pressure can be measured for monitoring purposes by the pressure sensor P2. This optimized operating pressure is determined according to tables, notably those established by the manufacturer based on tests.

[0076] The second expansion device 7 is configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger 8 so as to reach and maintain a target temperature of said heat transfer fluid at the outlet of the second heat exchanger 8, while simultaneously monitoring the superheat of the refrigerant at the outlet of the second heat exchanger 8 in order to reach and maintain a superheat of 5°C or higher. This target temperature can be determined, in particular, to maintain the coils within a temperature range in which their performance is adequate. The temperature of the heat transfer fluid at the outlet of the second heat exchanger 8 can be measured, in particular, by the temperature sensor T5.

[0077] The superheating of the refrigerant at the outlet of the second heat exchanger 8 corresponds in particular to the subtraction of the temperature of the refrigerant at the outlet of the second heat exchanger 8 from the theoretical saturation temperature of the refrigerant at the pressure at the outlet of the second heat exchanger 8.

[0078] The superheat of the refrigerant at the outlet of the second heat exchanger 8 can thus be calculated as a function of: - the theoretical saturation temperature of the refrigerant at the pressure measured by the PI pressure sensor of the refrigerant between the outlet of the second heat exchanger 8 and the inlet of the compressor 2, and - the temperature measured by the temperature sensor Tl of the refrigerant at the outlet of the second heat exchanger 8.

[0079] In the case where the PI pressure sensor is located far from the second heat exchanger 8, for example if it is positioned on the main branch downstream of the accumulator 6 or the low pressure part of the internal heat exchanger 9, an estimate of the outlet pressure of the second heat exchanger 8 can be made based on predictions of pressure losses of the refrigerant fluid caused by this distance and the elements between the second heat exchanger 8 and the pressure sensor PI.

[0080] Thus, by controlling the superheat of the refrigerant fluid at the outlet of the second heat exchanger 8, it is possible to prioritize the cooling of the batteries with a superheat between 3° and 5°C and to prioritize the cooling of the passenger compartment with a superheat greater than or equal to 5°C.

[0081] This thermal management circuit 1 process allows a cooling priority to be given to the batteries or the passenger compartment by playing on a single superheat parameter of the refrigerant fluid at the outlet of the second heat exchanger 8, facilitating the switch from one cooling priority to another.

[0082] Second mode of operation:

[0083] The thermal management circuit 1 can be configured to operate in a second mode, illustrated in Figure 4, in which the refrigerant is compressed by the compressor 2 and then circulates through the radiator 3. As it passes through the radiator 3, the refrigerant releases heat energy, for example, to the external airflow. The refrigerant then passes through the first expansion device 4 and undergoes a pressure drop, reaching a low pressure before passing through the first heat exchanger 5. As it passes through the first heat exchanger 5, the refrigerant absorbs heat energy, for example, from the internal airflow, thus cooling it. The refrigerant then returns to the refrigerant accumulator 6 and the compressor 2.

[0084] If the internal heat exchanger 9 is present, its high-pressure part is traversed by high-pressure refrigerant from the radiator 3 and its low-pressure part is traversed by low-pressure refrigerant from the refrigerant accumulator 6.

[0085] This second operating mode allows the internal airflow passing through the first heat exchanger 5 to be cooled, for example, to cool the passenger compartment of the motor vehicle. The excess heat energy from the refrigerant is dissipated into the outside air via the radiator 3.

[0086] In this second mode of operation, the first redirection device 4, 7 prevents the circulation of the refrigerant fluid from the outlet of the radiator 3 towards the bypass branch B.

[0087] According to this second operating mode, the management process is configured so that the compressor 2 is set up to control the temperature of the airflow X destined for the passenger compartment, exiting the first heat exchanger 5, in order to reach and maintain a target temperature. This target temperature is determined, in particular, by the passenger compartment temperature setpoint desired by the user. The temperature of the airflow X can be measured by the temperature sensor T4.

[0088] The first expansion device 4 can be configured to control the refrigerant pressure at the outlet of the radiator 3 so as to achieve and maintain an optimized operating pressure, i.e., within a pressure range around the pressure Optimal operating pressure. This pressure can be measured for monitoring purposes using pressure sensor P2. This optimized operating pressure is determined according to tables, notably those established by the manufacturer based on tests. This is particularly relevant for a supercritical refrigerant such as R744a.

[0089] Alternatively, the first expansion device 4 can be configured to control the refrigerant pressure at the outlet of the radiator 3 in order to achieve optimized subcooling at the outlet of the radiator 3, i.e., within a subcooling range around an optimal operating subcooling level. This optimized subcooling is determined according to tables, notably those established by the manufacturer based on tests. This is particularly relevant for a subcritical refrigerant such as RL234YF.

[0090] The subcooling at the outlet of radiator 3 corresponds in particular to the subtraction of the temperature of the refrigerant at the outlet of radiator 3, measured by the temperature sensor T6 with the theoretical saturation temperature of the refrigerant at the pressure at the outlet of radiator 3, measured by the pressure sensor P2.

[0091] This thermal management circuit 1 process also allows switching from one operating mode to another by adjusting a single parameter.

[0092] The control and command of the thermal management circuit can thus be continuous from one operating mode to another and from one cooling priority to another.

[0093] According to the management process, regardless of whether the operating mode is first or second, or regardless of the cooling priority, if the refrigerant temperature at the outlet of compressor 2 is greater than or equal to a maximum value, or if the maximum rotational speed of compressor 2 is reached, then the first expansion device 4 reduces the pressure drop of the refrigerant flowing through it. The refrigerant temperature at the outlet of compressor 2 can be measured, in particular, by the temperature sensor T3. The maximum refrigerant temperature at the outlet of compressor 2 corresponds to a temperature value determined by the compressor resistance 2, beyond which the performance of compressor 2 may decrease and / or beyond which compressor 2 may be damaged.The maximum rotational speed of compressor 2 is the maximum speed at which compressor 2 can operate.

[0094] According to the management procedure, regardless of whether the operating mode is first or second, or regardless of the cooling priority, if superheat occurs at the refrigerant inlet of accumulator 6, or if the high pressure of the refrigerant reaches a maximum value, then the first expansion device 4 reduces the pressure drop of the refrigerant flowing through it. The superheat at the refrigerant inlet of accumulator 6 can thus be calculated by subtracting the theoretical saturation temperature of the refrigerant at the inlet pressure of the refrigerant at the accumulator inlet pressure from the theoretical saturation temperature of the refrigerant at the inlet pressure of the refrigerant at accumulator 6.

[0095] This overheating can therefore be calculated based on: - the theoretical saturation temperature of the refrigerant at the pressure measured by the PI pressure sensor of the refrigerant at the inlet of the accumulator 6, and - the temperature measured by the temperature sensor T2 of the refrigerant at the inlet of the refrigerant of the accumulator 6.

[0096] The high-pressure value of the refrigerant depends on the type of refrigerant and the thermal management circuit itself (particularly the compressor 2). For example, for R744a, the maximum pressure can be around 128 bar. The high pressure within the thermal management circuit 1 can be measured by pressure sensor P2.

[0097] Third mode of operation:

[0098] The thermal management circuit 1 can also be configured to operate in a third mode, illustrated in Figure 5, in which the refrigerant is compressed by the compressor 2 and then circulates through the radiator 3. As it passes through the radiator 3, the refrigerant releases heat energy, for example, to the external airflow. The refrigerant then flows into the bypass branch B, passes through the second expansion device 7, and undergoes a pressure drop to reach a low pressure before passing through the second heat exchanger 8. As it passes through the second heat exchanger 8, the refrigerant absorbs heat energy, notably from the heat transfer fluid circulating in the heat transfer fluid circuit Y. The refrigerant then returns to the refrigerant accumulator 6 and the compressor 2.

[0099] If the internal heat exchanger 9 is present, its high-pressure part is traversed by high-pressure refrigerant from the radiator 3 and its low-pressure part is traversed by low-pressure refrigerant from the refrigerant accumulator 6.

[0100] This third operating mode allows the heat transfer fluid in the heat transfer fluid circuit Y, passing through the second heat exchanger 8, to be cooled, for example, to cool the vehicle's batteries. Excess heat energy from the refrigerant is dissipated into the outside air via the radiator 3.

[0101] In this third mode of operation, the first redirection device 4, 7 allows the circulation of the refrigerant from the outlet of the radiator 3 towards the bypass branch B and blocks the passage of the first heat exchanger 5 by the refrigerant.

[0102] Thus, we can clearly see that the management process makes it easier to switch from one cooling priority to another within the first operating mode, but also makes it easier to switch from one operating mode to another, particularly between the first and second operating modes.

Claims

Demands

1. A method for managing a thermal management circuit (1) for an electric or hybrid motor vehicle, said thermal management circuit (1) comprising: - a main loop (A) comprising, in the direction of circulation of a refrigerant fluid, a compressor (2), a radiator (3), a first expansion device (4), a first heat exchanger (5) configured to exchange directly or indirectly with an airflow (X) destined for the passenger compartment and a refrigerant fluid accumulator (6), - a bypass branch (B) connecting the refrigerant outlet of the radiator (3) to the refrigerant inlet of the refrigerant accumulator (6), said bypass branch (B) comprising, in the direction of refrigerant flow, a second expansion device (7) and a second heat exchanger (8) configured to exchange with the vehicle's batteries via a heat transfer fluid circuit (Y), the first expansion device (4), the second expansion device (7) and the compressor (2) being connected to a control unit (U), said thermal management method being configured to control the thermal management circuit (1) in a first operating mode with priority cooling of the batteries, in which the refrigerant flows successively through the compressor (2) and the radiator (3),a first part of the refrigerant fluid passing through the first expansion device (4) where it undergoes a pressure loss and the first heat exchanger, (5) before joining the refrigerant accumulator (6), a second part of the refrigerant passing through the bypass branch (B) and through the second expansion device (7) where it undergoes a pressure loss and the second heat exchanger (8) before joining the refrigerant accumulator (6), in said management method, the compressor (2) is configured to control the temperature of the airflow (X) to the passenger compartment at the outlet of the first heat exchanger (5) so as to achieve and maintain a target temperature, the second expansion device (7) being configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger (8) so as to achieve and maintain a target temperature while monitoring the superheat of the refrigerant at the outlet of the second heat exchanger (8) so as to achieve and maintain a superheat of between 3° and 5°C.

2. A management method according to the preceding claim, characterized in that said thermal management method is configured to control the thermal management circuit (1) in a first operating mode with priority cooling of the passenger compartment, in which the refrigerant circulates successively through the compressor (2) and the radiator (3), a first portion of the refrigerant passing through the first device of expansion (4) where it undergoes a pressure loss and the first heat exchanger (5) before joining the refrigerant accumulator (6), a second part of the refrigerant passing through the bypass branch (B) and through the second expansion device (7) where it undergoes a pressure loss and the second heat exchanger (8) before joining the refrigerant accumulator (6), in said management method, the compressor (2) is configured to control the temperature of the airflow (X) to the passenger compartment at the outlet of the first heat exchanger (5) so as to reach and maintain a target temperature,the second expansion device (7) being configured to control the temperature of the heat transfer fluid at the outlet of the second heat exchanger (8) so as to reach and maintain a target temperature of said heat transfer fluid at the outlet of the second heat exchanger (8) while monitoring the superheat of the refrigerant at the outlet of the second heat exchanger (8) so as to reach and maintain a superheat greater than or equal to 5°C.

3. A method for managing any one of the preceding claims, characterized in that the first expansion device (4) is configured to control the pressure of the refrigerant fluid at the outlet of the radiator (3) so as to achieve and maintain an optimized operating pressure or achieve optimized subcooling at the outlet of the radiator (3).

4. A management method according to any one of the preceding claims, characterized in that the thermal management circuit (1) comprises, connected to the control unit (U): - a temperature sensor (Tl) of the refrigerant fluid located at the outlet of the second heat exchanger (8), - a refrigerant pressure sensor (PI) located between the outlet of the second heat exchanger (8) and the inlet of the compressor (2), - a temperature sensor (T2) of the refrigerant fluid at the inlet of the accumulator (6), the superheat of the refrigerant fluid at the outlet of the second heat exchanger (8) being calculated as a function of: - the theoretical saturation temperature of the refrigerant at the pressure measured by the pressure sensor (PI) of the refrigerant between the outlet of the second heat exchanger (8) and the inlet of the compressor (2), and - the temperature measured by the temperature sensor (Tl) of the refrigerant at the outlet of the second heat exchanger (8).

5. A management method according to any one of the preceding claims, characterized in that said thermal management method is configured to control the thermal management circuit (1) in a second passenger compartment cooling operating mode, in which the refrigerant circulates successively through the compressor (2) and the radiator (3), the first expansion device (4) where it undergoes a pressure drop, and the first heat exchanger (5) before joining the refrigerant accumulator (6), in said management process, the compressor (2) is configured to control the temperature of the airflow (X) to the passenger compartment at the outlet of the first heat exchanger (5) so as to reach and maintain a target temperature, the first expansion device (4) is configured to control the pressure of the refrigerant at the outlet of the radiator (3) so as to reach and maintain an optimized operating pressure.

6. A management method according to any one of the preceding claims, characterized in that the control and command of the thermal management circuit is continuous from one operating mode to another and from one cooling priority to another.

7. A management method according to any one of the preceding claims, characterized in that if the temperature of the refrigerant at the outlet of the compressor (2) is greater than or equal to a maximum value, or if the maximum rotational speed of the compressor (2) is reached, then the first expansion device (4) reduces the pressure loss of the refrigerant passing through it.

8. Management method according to the preceding claim, characterized in that the thermal management circuit (1) includes a temperature sensor (T3) of the refrigerant fluid at the outlet of the compressor (2) connected to the control unit (U).

9. A management method according to any one of the preceding claims, characterized in that if overheating occurs at the refrigerant inlet of the accumulator (6), or if the high pressure of the refrigerant reaches a maximum value, then the first expansion device (4) reduces the pressure loss of the refrigerant passing through it.

10. Management method according to the preceding claim, characterized in that the thermal management circuit (1) includes a pressure sensor (P2) of the refrigerant fluid at the outlet of the radiator (3), said pressure sensor (P2) being connected to the control unit (U).

11. A management method according to any one of the preceding claims, characterized in that the thermal management circuit (1) includes a temperature sensor (T4) disposed in the airflow (X) to the passenger compartment at the outlet of the first heat exchanger (5), said temperature sensor (T4) being connected to the control unit (U).

12. A management method according to any one of the preceding claims, characterized in that the thermal management circuit (1) includes a temperature sensor (T5) of the heat transfer fluid of the heat transfer fluid circuit (Y) at the outlet of the second heat exchanger (8), said temperature sensor (T5) being connected to the control unit (U). 17

13. A management method according to any one of the preceding claims, characterized in that the thermal management circuit (1) includes a temperature sensor (T6) of the refrigerant fluid at the outlet of the radiator (3), said temperature sensor (T6) being connected to the control unit (U).

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