Thermal management system for a motor vehicle and method for operating such a system

Abstract

Thermal management system (100) for a motor vehicle comprising: a refrigerant circuit (10) comprising a compressor (11), an internal condenser (12) which is in heat-exchanging contact with an air duct (30), a first external heat exchanger (13), a first expansion valve (16), an evaporator (17) which is arranged in the refrigerant circuit (10) downstream of the first expansion valve (16) and upstream of the compressor (11) and which is in heat-exchanging contact with an air duct (30), and a chiller (19) which can be switched in parallel with the evaporator (17) in a first cooling mode; a coolant circuit (40) which is in heat-exchanging contact with the chiller (19) and components (41) of an electric drive of the motor vehicle to be cooled; characterized in that the thermal management system (100) is configured so that in a second cooling mode a coolant-refrigerant heat exchanger (19) 19'),which is in heat-exchanging contact with the coolant circuit (40), is arranged or can be switched on the refrigerant side upstream of the first expansion valve (16), - the first external heat exchanger (13) is thermally decoupled, - a radiator is arranged in the coolant circuit (40) as a second external heat exchanger (43), which is arranged in a first coolant branch line (45A), which can be separated from the coolant circuit (40) in the second cooling mode, and - the coolant-refrigerant heat exchanger (19, 19') is arranged in a section (40, 45B) of the coolant circuit separate from the first coolant branch line (45A).

Description

The present invention relates to a thermal management system for a motor vehicle and a method for operating such a system. Thermal management systems for motor vehicles must perform a number of tasks, including, in particular, air conditioning the passenger compartment, cooling and, if necessary, temperature control of the engine, drive, and other components, as well as the energy-efficient planning and execution of these functions. Thermal management systems are particularly important for electric vehicles because there is no waste heat and the range of the electric vehicle can be increased through energy efficiency. Thermal management systems have become established that, in addition to a refrigerant circuit, provide a coolant circuit through which the electric drive components can be thermally coupled and which can temporarily balance the thermal energy in the system. It is the object of the present invention to provide a thermal management system and a method for operating such a system, which shows further possibilities for realizing energy saving potentials during the operation of a motor vehicle. This object is achieved by a thermal management system having the features of claim 1 and a method for operating such a system having the features of claim 12. Advantageous embodiments and further developments emerge from the dependent claims. The thermal management system according to the invention comprises a refrigerant circuit with a compressor, an internal condenser in heat-exchanging contact with an air duct, a first external heat exchanger, a first expansion valve, an evaporator arranged in the refrigerant circuit downstream of the first expansion valve and upstream of the compressor and in heat-exchanging contact with an air duct (for example, in the same air duct as the internal condenser), and a chiller that can be switched in parallel with the evaporator in a first cooling mode. The thermal management system further comprises a coolant circuit in heat-exchanging contact with the chiller and components of an electric drive of the motor vehicle that are to be temperature-controlled.The thermal management system is characterized in that it is configured such that, in a second cooling mode, a coolant-to-refrigerant heat exchanger, which is in heat-exchanging contact with the coolant circuit, is arranged or connectable upstream of the first expansion valve on the refrigerant side, and the first external heat exchanger is thermally decoupled. Instead of releasing heat to the environment via the first external heat exchanger, it can be released to the cooling circuit. This has the advantage that the heat stored in this way can be used later in the system if necessary, or is only stored briefly in the thermal management system to be released again later.This is particularly useful for moderate temperatures between 10°C and 30°C ambient temperatures, when the coolant circuit and the thermal masses connected therein absorb the excess heat in the short term without significantly heating up the vehicle itself or impairing its operation. "Switchable" in the sense of the invention means that corresponding pipe sections can be actively integrated into or excluded from the circuit by means of control devices or valves. "Thermally decoupleable" can include a series of measures suitable for significantly reducing or completely preventing heat exchange, as described in more detail below with examples. The first external heat exchanger can be insulated, in particular on the air side, for example by switching off a fan assigned to it and / or by air dampers that shield it from the air flow intended for heat exchange. Enabling the fan to be switched off at least briefly saves energy and reduces the noise level. The internal condenser is typically located as a heating condenser or cabin condenser in an air duct of a motor vehicle's air conditioning system. The evaporator is also typically located in the same air duct (or alternatively, in a different air duct) of the air conditioning system. Both heat exchangers then serve to provide air conditioning for the vehicle cabin, but can also be used for other air conditioning purposes, e.g., for refrigerated compartments or air-conditioned utility space. According to one embodiment of the invention, the first external heat exchanger is arranged in a first refrigerant branch line, which can be separated from the refrigerant circuit in the second cooling mode. Such a branch line can typically be implemented cost-effectively as a shut-off parallel line and can completely prevent heat exchange. According to one embodiment of the invention, a radiator is arranged in the coolant circuit as a second external heat exchanger, which is arranged in a first coolant branch line that can be separated from the coolant circuit in the second cooling mode. With a typical arrangement of the external heat exchangers in the front area of the motor vehicle, with such an arrangement, with thermal decoupling of the first and second external heat exchangers, the radiator grille can be closed, if necessary, using an air closure mechanism, e.g., a blind or flap arrangement. This improves the aerodynamic drag of the motor vehicle, which has a positive effect on the motor vehicle's energy consumption. According to one embodiment of the invention, the coolant-refrigerant heat exchanger is the chiller, which can be switched from a previous parallel connection to the evaporator (in the first cooling mode) to a series connection upstream of the first expansion valve and the evaporator in the second cooling mode. This is cost-effective because no additional coolant-refrigerant heat exchanger is required. Typically, in such an arrangement, a second expansion valve can be arranged downstream of the internal condenser, and the chiller can be switched downstream of the second expansion valve. The chiller then operates at an intermediate pressure level, with which the heat absorption into the coolant circuit can be controlled via the second expansion valve. According to one embodiment of the invention, the coolant-refrigerant heat exchanger is an additional heat exchanger in contact with the coolant circuit, which is arranged upstream of the first expansion valve on the refrigerant side. Depending on the design variant, such a heat exchanger can be arranged in various positions. In a first variant, the coolant-refrigerant heat exchanger is arranged in the coolant circuit in a second coolant branch line, which is thermally separable from the coolant circuit (where "thermally separable" can typically be achieved via suitable shut-off devices, but can also be achieved by switching off pumps in this branch line). The second coolant branch line is advantageously arranged parallel to the line section with the chiller. According to a second variant, the coolant-refrigerant heat exchanger can be arranged upstream of the first external heat exchanger in the first cooling mode and can be thermally switched off on the coolant side, while it can be switched on on the coolant side in the second cooling mode (again via the opening of suitable shut-off devices or the switching on of corresponding pumps). According to a third variant, the coolant-refrigerant heat exchanger is arranged downstream of the first external heat exchanger in the first cooling mode and can be thermally deactivated on the coolant side, wherein in the second cooling mode it can be activated on the coolant side and the first external heat exchanger can be deactivated on the air side. According to a fourth variant, the coolant-refrigerant heat exchanger is arranged parallel to the first external heat exchanger in a second refrigerant branch line, which can be separated from the refrigerant circuit in the first cooling mode. According to a fifth variant, the coolant-refrigerant heat exchanger is arranged parallel to the internal condenser in a third refrigerant branch line, which can be activated to the refrigerant circuit in the second cooling mode. The method according to the invention is characterized by the following steps: thermally coupling a coolant-refrigerant heat exchanger on the refrigerant side upstream of the first expansion valve, and thermally decoupling the external heat exchanger. The advantage, as described above, is that the waste heat generated during operation is temporarily absorbed in the coolant circuit and the thermal masses connected therein, and the operation of the first and, if applicable, second external heat exchanger can be dispensed with. The thermal coupling of the coolant-refrigerant heat exchanger is achieved, for example, by switching on at least one pump and / or opening at least one shutoff valve in the coolant circuit.The thermal decoupling of the outdoor heat exchanger is advantageously achieved by closing the first refrigerant branch line and / or switching off a fan and / or closing the vehicle's radiator grille (which is typically located as a front grille in the front section of the vehicle). While switching off the fan already saves several hundred watts of energy, closing the radiator grille can save around 1 kW of power, depending on the driving speed. This benefits the range of an electric vehicle. In the specified method, the waste heat generated by the refrigerant circuit during cooling operation is temporarily stored in the vehicle. This is not possible under all external conditions (e.g., after periods of downtime in hot weather or blazing sun) and not for an unlimited period of time, as this would otherwise risk overheating of the coolant circuit, the components connected to it, and the vehicle itself. Therefore, the method according to the invention is advantageously carried out when certain external conditions are detected and only for a specific period of time before switching to the first, "normal," cooling mode. The thermal management system is advantageously operated in a first cooling mode when the temperature of the component of the motor vehicle's electric drive to be tempered is greater than or equal to a specified first limit temperature. Conversely, if the temperature of the component to be tempered is less than a specified second limit temperature, the thermal management system is operated in a second cooling mode according to the method described above. The first limit temperature and the second limit temperature can have the same value or be different. Advantageously, the first limit temperature is higher than the second limit temperature. This can potentially avoid constant switching back and forth between the two cooling modes. Alternatively, other parameters can be taken into account for switching between the first and second cooling modes, such as the outside temperature, the vehicle's speed, and / or the period of time the thermal management system was already operating in the first cooling mode. In particular, it can be provided that the vehicle's speed is detected and that the system switches from the second cooling mode to the first cooling mode if the vehicle speed is lower than a limit speed, even though the temperature of the component to be tempered is lower than the specified first limit temperature. This temporary, premature switching from the second to the first cooling mode (even though the limit temperature has not yet been reached) has the advantage that operation in the second cooling mode is reserved, as far as possible, for those driving sections in which the driving speed is relatively high and thus the expected energy savings are greatest. The invention will now be explained in more detail using exemplary embodiments and with reference to the figures. Fig. 1 schematically shows a circuit arrangement of a thermal management system in connection with the invention, Fig. 2 schematically shows the structure of a refrigerant circuit according to the prior art, Figs. 3 - 7 schematically show circuit arrangements of refrigerant circuits for thermal management systems according to exemplary embodiments of the invention and Fig. 8 schematically shows a coolant circuit for a thermal management system according to an exemplary embodiment of the invention. Fig. 2 schematically illustrates the structure of a prior art refrigerant circuit 10, as used in particular for the air conditioning of motor vehicles. The refrigerant circuit 10 is driven by a compressor 11, whereby in a cooling mode, the external heat exchanger 13 is arranged in the high-pressure region and releases excess heat by transfer to the ambient air (indicated by an arrow). Via a downstream expansion valve 16, the refrigerant cooled by the outside air is expanded and thereby further cooled before it can be used for a cooling function in the low-pressure region at the evaporator 17, which is arranged in a motor vehicle air conditioning system. The considerations of the present invention are based on not necessarily or continuously discharging the excess heat to the environment, but instead storing it at least temporarily in the coolant circuit 40—driven by at least one pump 42—and components 41 arranged therein, in particular an electric drive, via a chiller 19 or other refrigerant-to-coolant heat exchanger 19'. The thermal management system 100 designed in this way, according to Fig. 1, comprises the refrigerant circuit 10, which is coupled to the coolant circuit via the chiller 19 and / or the refrigerant-to-coolant heat exchanger 19', and a control device 50 for controlling the thermal management system in at least a first and a second cooling mode. With reference to Figs. 3 to 7, the circuit arrangements of refrigerant circuits 10 for thermal management systems 100 according to exemplary embodiments of the invention are explained in more detail schematically below. The refrigerant circuit 10 for a first exemplary embodiment is explained generally with reference to Fig. 3. Further exemplary embodiments are described with reference to Figs. 4 to 7, in which case only the differences from the first exemplary embodiment will be discussed and most reference numerals are omitted. The refrigerant circuit 10 comprises a compressor 11, an internal condenser 12, which is in heat-exchanging contact as a cabin condenser in an air duct 30 of an air conditioning system of the motor vehicle, and a first external heat exchanger 13, which is arranged in a first refrigerant branch line 25A in the front area of the motor vehicle. Downstream of this, a refrigerant collector 14 is integrated, which collects liquid refrigerant and, via a riser, conveys the refrigerant downstream under defined conditions. It is fluidly connected downstream to the first expansion valve 16. Depending on the design, the first expansion valve 16 can be a thermostatic or electronically controlled expansion valve and can optionally also be fully shut off. At the first expansion valve 16, the refrigerant is expanded, evaporated in an evaporator 17, and, after passing through an internal heat exchanger 18, sucked back in by the compressor 11. The evaporator 17 is also arranged in the air duct 30 of the motor vehicle's air conditioning system, upstream of the heating condenser, in order to provide air conditioning for the passenger compartment together with the latter. A number of additional components are provided in the refrigerant circuit 10, which are mentioned here as examples: Additional expansion valves 15, 20, which are fully electronically controllable and can also be completely closed or opened. Furthermore, a number of shut-off valves 21A-21C and a throttle 21D (with check valve) are provided, which are required to adjust the active refrigerant branch lines for different operating modes. Furthermore, in connection with the thermal management system 100 according to the following exemplary embodiments, at least one fan 35 in the front area of the motor vehicle and, if appropriate, an air flap 31 in the air duct 30 are also important. A chiller 19 with the upstream expansion valve 20 is arranged in parallel with the evaporator 17 and can be switched on. The chiller 19 and a radiator 43 as a second external heat exchanger are integrated into the coolant circuit 40, with the radiator 43 also being arranged in the front area of the motor vehicle (e.g., in front of or behind the first external heat exchanger 13 in relation to the air flow). The layout of the coolant circuit 40 will be explained in more detail with reference to Fig. 8. According to the invention, the thermal management system 100 can be operated in a first and a second cooling mode. Cooling modes are all operating modes in which the evaporator 17 is not deactivated. In a broader sense, this also includes a mixed mode (dehumidification mode / reheat mode), in which both the evaporator 17 and the internal condenser 12 in the air duct 30 are actively operated for heat exchange. The thermal management system 100 can also be operated in other operating modes, which are only briefly discussed here but are familiar to those skilled in the art. In particular, this relates to a pure heating mode (heat pump mode). Heat pump mode can be achieved, for example, by using the electric expansion valve 15 with a throttling function (i.e., not fully open, as in cooling mode).In this case, the outdoor heat exchanger 13 is operated as an evaporator in the low-pressure range with the radiator grille 36 open, in order to provide thermal energy from the ambient air at a low temperature level for a heating function. For this purpose, the shut-off valve 21A is closed, and the shut-off valves 21C and 21B are opened. In the first cooling mode, the refrigerant circuit 10 operates as follows: The refrigerant is pumped by the compressor 11 through the internal condenser 12 with the shutoff valve 21C closed, the shutoff valve 21A open, and the electronic expansion valve 15 fully open (without throttling) to the first external heat exchanger 13. The internal condenser 12 (cabin condenser) is thermally inactivated by closing the air flap 31 in the air duct 30, so that, minus minor losses, hardly any thermal energy is transferred into the air duct 30. At the external heat exchanger 13, the excess heat is dissipated to the environment via the open radiator grille 36, as is known per se.When the shut-off valve 21B is closed, the cooled and at least partially condensed refrigerant enters the refrigerant collector 14, in which the liquid refrigerant collects at the bottom. From there, it is led via a riser line to the first expansion valve 16, expands, and returns to the suction side of the compressor 11 via the evaporator 17. In parallel, a portion of the refrigerant is directed via the chiller 19 under the control of the electronic expansion valve 20. The mass flow in the two parallel lines results from the coordination of the opening degrees of the expansion valves 16 and 20, because both lines meet upstream of the suction side of the compressor 11, so that the same pressure prevails downstream of the chiller 19 and the evaporator 17. For the second cooling mode, a coolant-refrigerant heat exchanger 19, 19' is provided, which is in heat-exchanging contact with the coolant circuit 40 and is arranged or connectable upstream of the first expansion valve 16 on the refrigerant side. Furthermore, the first external heat exchanger 13 is configured to be thermally decoupled, which will be discussed in more detail below. According to the first exemplary embodiment according to Fig. 3, a separate coolant-refrigerant heat exchanger 19' is arranged downstream of the internal condenser 12 (cabin condenser) and upstream of the refrigerant collector 14. According to a second exemplary embodiment according to Fig. 4, a separate coolant-refrigerant heat exchanger 19' is arranged downstream of the first external heat exchanger 13 and upstream of the refrigerant collector 14. For the first two exemplary embodiments, the coolant-refrigerant heat exchanger 19' is thermally deactivated in the first cooling mode by being shut down on the coolant side, so that, apart from minor losses, no thermal energy is dissipated into the coolant circuit 40. In the second cooling mode, a flow through the coolant side is then provided so that excess heat can be transferred to the coolant circuit 40. The thermal decoupling of the first external heat exchanger 13 takes place on the air side in both exemplary embodiments, i.e.i.e., in particular by switching off the fan 35 and / or closing the radiator grille 36. In addition, in the refrigerant circuit 10, only minor changes or adjustments to the expansion valves 15, 16, 20 and no changes to the shut-off valves 21A - 21C are necessary. According to the third exemplary embodiment shown in Fig. 5, a separate coolant-refrigerant heat exchanger 19' is arranged parallel to the first external heat exchanger 13 in a second refrigerant branch line 25B, which is parallel to the first refrigerant branch line 25A and can be separated from the refrigerant circuit 10 in the first cooling mode. In the first cooling mode, the shut-off valve 21G is closed and the shut-off valve 21H is open; in the second cooling mode, the situation is reversed. The thermal decoupling of the first external heat exchanger 13 thus also occurs on the refrigerant side, whereby the fan 35 can advantageously also be switched off and the cooling grille 36 can also be closed. According to the fourth embodiment shown in Fig. 6, a separate coolant-to-refrigerant heat exchanger 19' is arranged parallel to the internal condenser 12 in a third refrigerant branch line 25C, which can be connected to the refrigerant circuit in the second cooling mode. In the first cooling mode, the shut-off valve 21F is open and the second shut-off valve 21E is closed; in the second cooling mode, the situation is reversed. In one embodiment, the valves 21E and 21F can also be configured as proportional valves, setting a proportional opening / closing degree. According to the fifth embodiment shown in Fig. 7, the coolant-refrigerant heat exchanger 19' is the chiller 19, which, starting from a parallel connection to the evaporator 17 in the first cooling mode, can then be switched to a series connection upstream of the first expansion valve 16 and the evaporator 17 in the second cooling mode. This requires additional refrigerant branch lines 25D and 25E, additional shut-off valves 21J, 21K, 21L, and other settings of various other components, as described below. In the second cooling mode, the shut-off valve 21A remains open, but the closable expansion valve 15 is completely closed, so that the refrigerant flows via the refrigerant branch line 25D and the open shut-off valve 21K (which must be kept closed in the first cooling mode) to the electric expansion valve 20.This allows a variable pressure level in dehumidification / reheat mode to balance the heat dissipation from the cabin condenser and the chiller 19. When the shutoff valve 21L is closed (which is open in the first cooling mode), the refrigerant flows back via the refrigerant branch line 25E to the refrigerant receiver 14 when the shutoff valve 21J is open (which is closed in the first cooling mode), from where the circuit is closed via the first expansion valve 16 and the evaporator 17. In the second cooling mode, the chiller 19 is thermally coupled or decoupled on the coolant side and the first external heat exchanger 13 is thermally decoupled or decoupled on the air side, analogous to the first and second exemplary embodiments. Referring to Fig. 8, the coolant circuit 40 is configured as follows in one embodiment variant, suitable for all exemplary embodiments: Components 41 of the electric drive of the motor vehicle, here the drive battery, the chiller 19, and at least one pump 42A, are arranged in a first sub-circuit. Further components 41', here the charger and inverter, the chiller 19, and a further pump 42B are arranged in a second sub-circuit. Both sub-circuits can be operated in various configurations, including independently and individually, via shut-off devices 44A, 44B, 44C. The shut-off devices are designed here as 3-way or 4-way valves. The radiator 43 is arranged as a second external heat exchanger in a first coolant branch line 45A. In the first cooling mode, the radiator 43 is integrated into the cooling circuit 40, but in the second cooling mode, it can be separated from the coolant circuit 40 by means of the shut-off devices 44A, 44C. The coolant-refrigerant heat exchanger 19' is arranged in the coolant circuit 40 in a second coolant branch line 45B arranged parallel to the chiller 19, which can be separated from the coolant circuit 40 via the shut-off device 44B in the first cooling mode and connected in the second cooling mode. Furthermore, the operation of the pumps 42A, 42B can moderate the heat transfer between the coolant circuit 40 and the refrigerant circuit 10. It should be mentioned in passing that a third coolant branch line 45C can optionally be provided for a rapid heating function to temporarily bypass the thermal mass of the components 41 (here the battery). The method according to the invention will now be briefly explained by way of example based on the described exemplary embodiments of the thermal management system 100. Starting from a normal cooling operation in the first cooling mode, the first external heat exchanger 13 (and possibly also the radiator 43 as the second external heat exchanger) release excess heat via the open radiator grille 36 to the drawn-in ambient air. The chiller 19 is connected in parallel with the evaporator 17 on the refrigerant side, so that both provide a cooling function. If present, the further refrigerant-coolant heat exchanger 19' is deactivated on the coolant side by separating the second coolant branch line 45B from the coolant circuit 40 or its coolant flow driven by the pumps 42A and possibly 42B via the shut-off device 44B. When switching to the second cooling mode, either the chiller 19 is deactivated on the refrigerant side, as shown in Fig.7, connected upstream of the first expansion valve 16, or, if present, the refrigerant-to-coolant heat exchanger 19' is actively integrated into the coolant circuit 40 by opening the shut-off device 44B. At the same time, the first coolant branch line 45A is closed by the shut-off device 44A and the first outdoor heat exchanger 13 is thermally inactivated, ie, the fan 35 is switched off, the radiator grille 36 is closed, and if necessary, the first refrigerant branch line 25A is separated from the refrigerant circuit 10. Switching to the second cooling mode can advantageously be used when a corresponding temperature corridor of the outside temperature is detected, typically between 10°C and 30°C, in particular between 15 and 25°C, and the motor vehicle has not otherwise heated up internally, e.g., due to prolonged parking in the sun or previous operation. In this case, the thermal mass of the battery or other components 41, 41' integrated in the coolant circuit 40 can briefly absorb thermal energy, so that operation with an outside heat exchanger can be temporarily dispensed with. In this case, the motor vehicle can be operated with the radiator grille 36 closed and the fan 35 switched off for a limited period of time, e.g., 5 minutes, or until a critical limit temperature is reached in the coolant circuit 40, thus saving energy. According to one exemplary embodiment, an upper and a lower limit temperature are defined for the temperature of the coolant circuit 40, on the basis of which the decision is made about switching between the first and second cooling mode. The limit temperatures are to be defined depending on the design and are based on the permissible operating temperatures of the components 41, 41' in the coolant circuit 40. In typical applications, the first limit temperature is between 35°C and 60°C, e.g., 50°C. The second limit temperature is typically 0°C to 10°C, e.g., 5°C lower. If the temperature in the coolant circuit 40 is lower than the first limit temperature when the motor vehicle is started (and if a cooling function for the driver's cab is requested at the same time), the thermal management system 100 can immediately switch to the second cooling mode, e.g., leave the fan 35 switched off and close or keep the radiator grille 36 closed.If the upper limit temperature is exceeded, the system switches to the first cooling mode to prevent overheating of the coolant circuit 40 and the components 41, 41'. Switching between the two cooling modes can also be done proactively and, if necessary, planned in advance. When the motor vehicle is temporarily stopped at a traffic light or a railroad crossing, it may be possible to switch to the first cooling mode early (i.e., in particular, to open the radiator grille 36) to reserve the second cooling mode for times of higher driving speed. Furthermore, a corresponding switching pattern can be planned at the start of the journey, e.g., using recorded navigation data for the upcoming route. The method according to the invention is installed on the control device 50 as an executable program. All necessary inputs and measured values for detecting the criteria for switching between different operating modes, in particular for switching between the first and second cooling modes, can be detected via the control device 50. All necessary control signals for operating the compressor 11, for changing the opening degrees and / or for opening / closing the expansion valves 15, 16, 20, for adjusting the shut-off valves 21A-21C and 21E-21L, for opening / closing the air flap 31 and / or the radiator grille 36, for operating the fan 35, adjusting the shut-off devices 44A-44C, and for operating the pumps 42A, 42B can be generated by the control device. LIST OF REFERENCE SYMBOLS 10 Refrigerant circuit 11 Compressor 12 Internal condenser, heating heat exchanger 13 Outdoor heat exchanger 14 Refrigerant receiver 15, 16, 20 Expansion valves 17 Evaporator 18 Internal heat exchanger 19 Chiller 19' Second refrigerant-coolant heat exchanger 21A - 21C Shut-off valves 21D Throttle with check valve 21E - 21L Shut-off valves 25A - 25E Refrigerant branch lines 30 Air duct of an air conditioning system 31 Air damper 35 Fan for the first and second outdoor heat exchanger 36 Closable radiator grille 40 Coolant circuit 41, 41' Components of an electric drive, in particular vehicle battery 42 Coolant pump 43 Radiator / second outdoor heat exchanger 44A - 44C Shut-off device 45A - 45C Coolant branch lines 50 Control device 100 Thermal management system

Claims

Thermal management system (100) for a motor vehicle with - a refrigerant circuit (10) comprising a compressor (11), an internal condenser (12) which is in heat-exchanging contact with an air duct (30), a first external heat exchanger (13), a first expansion valve (16), an evaporator (17) which is arranged in the refrigerant circuit (10) downstream of the first expansion valve (16) and upstream of the compressor (11) and is in heat-exchanging contact with an air duct (30), and a chiller (19) which can be switched in parallel to the evaporator (17) in a first cooling mode, - a coolant circuit (40) which is in heat-exchanging contact with the chiller (19) and components (41) of an electric drive of the motor vehicle to be tempered, characterized in that the thermal management system (100) is configured such that in a second cooling mode - a coolant-refrigerant heat exchanger (19, 19'),which is in heat-exchanging contact with the coolant circuit (40), is arranged or connectable upstream of the first expansion valve (16) on the refrigerant side, and- the first external heat exchanger (13) is thermally decoupled. Thermal management system (100) according to claim 1, characterized in that the first external heat exchanger (13) is arranged in a first refrigerant branch line (25A) which can be separated from the refrigerant circuit (10) in the second cooling mode. Thermal management system (100) according to claim 1 or 2, characterized in that a radiator is arranged in the coolant circuit (40) as a second external heat exchanger (43), which is arranged in a first coolant branch line (45A) which can be separated from the coolant circuit (40) in the second cooling mode. Thermal management system according to one of claims 1 to 3, characterized in that the coolant-refrigerant heat exchanger (19') is the chiller (19), which can be switched from a parallel connection to the evaporator (17) in the second cooling mode to a series connection upstream of the first expansion valve (16) and the evaporator (17). Thermal management system (100) according to claim 4, characterized in that a second expansion valve (20) is arranged downstream of the inner condenser (12), and the chiller (19) can be switched downstream of the second expansion valve (20). Thermal management system (100) according to one of claims 1 to 3, characterized in that the coolant-refrigerant heat exchanger (19) is an additional heat exchanger in contact with the coolant circuit (40) which is arranged on the refrigerant side upstream of the first expansion valve (16). Thermal management system (100) according to claim 6, characterized in that the coolant-refrigerant heat exchanger (19) is arranged in the coolant circuit (40) in a second coolant branch line (45B) which is thermally separable from the coolant circuit (40). Thermal management system (100) according to claim 6 or 7, characterized in that the coolant-refrigerant heat exchanger (19)- is arranged downstream of the first external heat exchanger (13) in the first cooling mode and can be thermally switched off on the coolant side and- can be switched on on the coolant side in the second cooling mode, wherein the first external heat exchanger (13) can be switched off on the air side. Thermal management system (100) according to claim 6 or 7, characterized in that the coolant-refrigerant heat exchanger (19) is arranged parallel to the first external heat exchanger (13) in a second refrigerant branch line (25B) which can be separated from the refrigerant circuit (10) in the first cooling mode. Thermal management system (100) according to claim 6 or 7, characterized in that the coolant-refrigerant heat exchanger (19) is arranged parallel to the inner condenser (12) in a third refrigerant branch line (25C), which can be connected to the refrigerant circuit (10) in the second cooling mode. Method for operating a thermal management system (100) according to one of the preceding claims, characterized by the following steps: - thermally coupling a coolant-refrigerant heat exchanger (19; 19') on the refrigerant side upstream of the first expansion valve (16) and - thermally decoupling the external heat exchanger (13). Method for operating a thermal management system (100) according to claim 11, characterized in that the thermal coupling of the coolant-refrigerant heat exchanger (19; 19') is carried out by switching on at least one pump (42) and / or opening at least one shut-off valve (44) in the coolant circuit. Method for operating a thermal management system (100) according to claim 11 or 12, characterized in that the thermal decoupling of the external heat exchanger (13) takes place by closing the first refrigerant branch line (25A) and / or switching off a fan (35) and / or closing the radiator grille (36) of the motor vehicle. Method for operating a thermal management system (100) according to one of claims 11 to 13, characterized in that - the thermal management system (100) is operated in the first cooling mode when the temperature of the component (41) of an electric drive of the motor vehicle to be tempered is greater than or equal to a specified first limit temperature, and - the thermal management (100) is operated in the second cooling mode according to a method according to one of claims 12 to 14 when the temperature of the component (41) of an electric drive of the motor vehicle to be tempered is less than a specified second limit temperature. Method for operating a thermal management system (100) according to claim 14, characterized in that - the vehicle speed of the motor vehicle is detected and - switching from the second cooling mode to the first cooling mode occurs when the vehicle speed is lower than a limit speed, although the temperature of the component (41) to be tempered is lower than the specified first limit temperature.

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