Method for controlling a thermal management system for electric vehicles

Abstract

Method for controlling a thermal management system for electric vehicles in different operating modes, comprising heating, cooling and dehumidifying cabin air of a vehicle cabin, wherein the thermal management system comprises a battery (210), an electric coolant heater (220), a heat pump arrangement (1) and a controller (400), the heat pump arrangement (1) comprising - a compressor (10) with a compressor inlet (11) and a compressor outlet (12), - a cabin condenser (20) with a refrigerant-side condenser inlet (21) and a refrigerant-side condenser outlet (22), - an external heat exchanger expansion valve (30), - an outdoor heat exchanger (40) with a refrigerant-side outdoor heat exchanger inlet (41) and a refrigerant-side outdoor heat exchanger outlet (42), wherein the outdoor heat exchanger expansion valve (30) is connected to the outdoor heat exchanger inlet (41), - a chiller expansion valve (70) and a chiller (80) with a refrigerant-side chiller inlet (81) and a refrigerant-side chiller outlet (82), wherein the chiller expansion valve (70) is connected to the refrigerant-side chiller inlet (81), and - a cabin evaporator expansion valve (50) and a cabin evaporator (60) with a refrigerant-side evaporator inlet (61) and a refrigerant-side evaporator outlet (62), wherein the cabin evaporator expansion valve (50) is connected to the evaporator inlet (61), - wherein the cabin condenser (20) and the cabin evaporator (60) are arranged in an HVAC duct (64) for air as coolant, - wherein the HVAC duct (64) has a duct air inlet (64-1) and a duct air outlet (64-2) which leads into the vehicle cabin, - wherein the cabin condenser (20) has a condenser air inlet (20-1) and a condenser air outlet (20-2), and - wherein the cabin evaporator (60) has an evaporator air inlet (60-1) and an evaporator air outlet (60-2), - wherein the chiller (80) comprises a chiller coolant inlet and a chiller coolant outlet, and - wherein the electric coolant heater (220) is connected in series to a battery coolant circuit (200) with the battery (210), a waste heat absorption device (230) for coupling waste heat from the electric vehicle into the battery coolant circuit (200) and the chiller (80), characterized in that that the electric coolant heater (220) is only activated when predetermined operating parameters of the thermal management system are met, which are determined depending on the respective operating mode, and that in a heating mode the electric coolant heater (220) is only activated when the compressor (10) has reached a maximum speed and that the maximum speed of the compressor (10) is determined by reaching a minimum suction pressure at the compressor inlet (11), a speed limit for component protection of the compressor (10) and / or a noise / vibration behavior of the compressor (10).

Description

[0001] The invention relates to a method for controlling a thermal management system according to claim 1.

[0002] Today's electric vehicles have a limited range, especially at low outside temperatures, where a significant amount of electrical energy is used for cabin heating. Heat pumps are now being used to reduce the use of electrical energy for cabin heating.

[0003] The applicant offers highly efficient thermal management systems. There are various system concepts for low-pressure or high-pressure cold storage (storage or collector system). In addition, different arrangements of heat exchangers are possible. An example of these known thermal management systems for electric vehicles with a heat pump arrangement 1 is shown in Fig. 10. The heat pump arrangement 1 connects, via a refrigerant circuit, a compressor 10 with a compressor inlet 11 and a compressor outlet 12, a cabin condenser 20 for heating the air in a vehicle cabin with a condenser inlet 21 and a condenser outlet 22, an external heat exchanger 40 for absorbing heat from or dissipating heat to the environment with an external heat exchanger inlet 41 and an external heat exchanger outlet 42, a chiller or external evaporator 80 with a refrigerant-side chiller inlet 81 and a refrigerant-side chiller outlet 82, wherein the refrigerant-side chiller inlet 81 is connected to a chiller expansion valve 70, a cabin evaporator 60 with a cabin evaporator inlet (evaporator inlet) 61 and a cabin evaporator outlet (evaporator outlet) 62, wherein the A cabin evaporator expansion valve 50 is connected upstream of the cabin evaporator inlet 61.On the air side, an air mixing damper 2 is provided for temperature control with the cabin condenser 20. Optionally, an internal heat exchanger can be arranged for heat transfer between the refrigerant before entering the cabin evaporator expansion valve 50 and the refrigerant after the cabin evaporator outlet 62. A bypass line 100 is provided between the external heat exchanger outlet 42 and the compressor inlet 11, which can be shut off via a shut-off valve (bypass shut-off valve) 90. This bypass line 100 for refrigerant is required in heating or heat pump mode.

[0004] The cabin condenser 20 with air mixing flap 2 and the cabin evaporator 60 are arranged in an HVAC duct 64 with a duct air inlet 64-1 and a duct air outlet 64-2. To ensure adequate heating of the vehicle cabin even at very low temperatures, an electric cabin heater 300 is provided in the HVAC duct 64.

[0005] The thermal management system or heat pump arrangement 1 further comprises a battery 210 and an electric coolant heater 220, a waste heat absorption device 230, and a coolant pump 240. The electric coolant heater 220, the coolant pump 240, the chiller 80, the waste heat absorption device 230, and the battery 210 are connected in series to form a battery coolant circuit 200. Evaporation heat is supplied to the chiller 80 via the battery coolant circuit 200.

[0006] A valve unit 110 is arranged between the outdoor heat exchanger outlet 42 and the chiller expansion valve 70 on the one hand, and the outdoor heat exchanger inlet 41 and the condenser outlet 22 on the other. The valve unit comprises a first and a second refrigerant inlet 111, 113, as well as a first and a second refrigerant outlet 112, 114. Optionally, a high-pressure side refrigerant reservoir can be provided in the valve unit 110. Depending on the operating mode, the valve unit 110 blocks, directs, or throttles the refrigerant flows between the refrigerant inlets 111, 113 and the refrigerant outlets 112, 114. By means of a controller 400, the heat pump arrangement 1 or the thermal management system can be operated in various operating modes, such as heating, cooling, or dehumidification mode.

[0007] In a heat pump or heating mode, refrigerant condensed in the cabin condenser 20 is supplied to the valve unit 110 via the first refrigerant inlet 111. Liquid refrigerant is then supplied to the chiller expansion valve 70 via the second refrigerant outlet 114, and the chiller expansion valve 70 creates a controlled expansion. The expanded refrigerant is evaporated in the chiller 80 by heat input via the battery coolant circuit 200 and compressed in the compressor 10. The compressed refrigerant gas from the compressor 10 is condensed in the cabin condenser, releasing heat to the air supplied to the vehicle cabin.

[0008] A disadvantage of the heat pump arrangement according to Fig. 10 with today's commonly used refrigerants, such as R134a or R1234yf, is that they cannot fully cover the heat demand for vehicle cabin heating at very low temperatures, -20°C and below. This is due to the low suction pressure of the compressor 10 at very low temperatures. If the suction pressure drops, the density of the refrigerant and thus the refrigerant mass flow rate decreases for a given maximum volumetric flow rate of the compressor 10. This reduces the refrigerant mass flow and consequently the heat flow supplied to the vehicle cabin via the cabin condenser 20.

[0009] There are various ways to increase the heating, such as gas injection systems, hot gas bypass heating systems or electric cabin heaters 300 - see Fig. 10. The aforementioned measures require additional costs and additional installation space, which is not always available. The electric heaters 300 and 220 reduce the range of an electric vehicle.

[0010] From DE 10 2011 109 055 A1 and US 11 104 205 B2, it is known to arrange the electric coolant heater upstream of the chiller so that the heat can be transferred to the cabin via the refrigerant circuit. Furthermore, from US 11 104 205 B2, control strategies for using the electric coolant heater for cabin heating in electric vehicles are known. In this case, the available heat from the external heat exchanger is estimated in advance using calculations. If this is insufficient to achieve the required cabin heating output and the coolant temperature at the chiller inlet is below a predetermined temperature threshold, the electric coolant heater is switched on, and the heat is coupled into the refrigerant circuit via the chiller and released to the vehicle cabin via the cabin condenser.A single heating operation or a combined operation is described in which the heat from the electric coolant heater and ambient heat from the outdoor heat exchanger is coupled into the refrigerant circuit.

[0011] Thermal management systems for electric vehicles that operate in different operating modes are also known from DE 10 2015 218 825 A1, DE 10 2021 001 328 T5, DE 10 2021 131 215 A1, DE 11 2018 002 250 T5, and DE 11 2020 004 427 T5. DE 11 2021 001 328 T5 discloses detecting the coolant temperature at the chiller coolant inlet. DE 10 2015 218 825 A1 discloses controlling the compressor speed based on the coolant temperature and limiting it to a maximum speed.

[0012] The disadvantage of DE 11 2018 002 250 T5 is that the waste heat from the vehicle is not utilized and that the activation of the electric coolant heater is poorly designed. The disadvantage of DE 11 2020 004 427 T5 is that the activation of the electric coolant heater is not linked to the compressor speed.

[0013] From DE10 2021 131 215 A1, which represents the closest prior art, it is further known that the electric coolant heater is switched on or off depending on the respective operating mode and unspecified operating parameters.

[0014] Based on DE10 2021 131 215 A1, the object of the present invention is to provide a more efficient method for controlling a thermal management system for electric vehicles in different operating modes and a method for switching between the operating modes.

[0015] This object is achieved by a method according to claim 1.

[0016] Heat from the coolant heater and the compressor, ambient heat, and waste heat from the vehicle are used for cabin heating. An electric heater in the HVAC duct is unnecessary, as the electric coolant heater in the battery coolant circuit is used for cabin heating when needed. To further increase efficiency, the electric coolant heater is only activated when predetermined operating parameters of the thermal management system are met, which are determined depending on the respective operating mode. In heating mode, the electric coolant heater is only activated when the compressor has reached a maximum speed. This maximum compressor speed is determined by reaching the minimum suction pressure at the compressor inlet, the speed limit for component protection of the compressor, and / or the noise / vibration behavior of the compressor - claim 1.

[0017] According to the advantageous embodiment according to claim 2, in heating mode, the air flow in the duct after the cabin evaporator is divided by means of an air mixing flap through the cabin condenser or past it, whereby the pressure at the compressor outlet and thus the heat transfer of the compressor to the refrigerant is influenced.

[0018] It has been found to be advantageous to control the heating output of the electric coolant heater in heating mode with at least one of the following operating parameters of the heat pump arrangement as a reference variable - Claim 3 Refrigerant pressure at the compressor outlet, Refrigerant superheat at the chiller outlet, Refrigerant superheat at the compressor inlet, Refrigerant superheat at the outdoor heat exchanger outlet, Air temperature at the condenser air outlet and / or Air temperature at the duct air outlet.

[0019] According to the advantageous embodiment according to claim 4, the heating output of the electric coolant heater is limited if the coolant temperature at the chiller inlet and thus the suction pressure at the compressor inlet are too high to allow heat absorption from the environment via the external heat exchanger. This also increases efficiency and limits the use of electrical energy from the battery.

[0020] The embodiment according to claim 5 relates to a concrete control strategy for the heating output of the electric coolant heater, in which the reference variable for controlling the heating output of the electric coolant heater is the refrigerant pressure at the compressor outlet, and in which the reference variable for the degree of opening of the chiller expansion valve is the refrigerant superheat at the chiller outlet or the refrigerant superheat at the compressor inlet.

[0021] The embodiment according to claim 6 relates to an alternative control strategy for the heating output of the electric coolant heater, in which the reference variable for controlling the heating output of the electric coolant heater is the refrigerant superheat at the chiller outlet or the refrigerant superheat at the compressor inlet, and in which the reference variable for the degree of opening of the chiller expansion valve is the refrigerant pressure at the compressor outlet.

[0022] The control strategies according to claim 5 or 6 ensure that the coolant temperature in the battery coolant circuit remains as low as possible, so that heat losses to the environment remain small.

[0023] It has been found to be advantageous to control the heating output of the electric coolant heater in dehumidification mode with at least one of the following operating parameters of the heat pump arrangement as a reference variable - claim 7: Refrigerant pressure at the compressor outlet, Air temperature at the condenser air outlet, Air temperature at the duct air outlet, Refrigerant superheat at the chiller outlet, Refrigerant superheat at the compressor inlet, and / or Air temperature at the evaporator air outlet.

[0024] In the advantageous embodiment according to claim 8, dehumidification takes place without heat dissipation via the external heat exchanger. The electric coolant heater is activated when the compressor has reached maximum speed or when the refrigerant superheat at the chiller outlet or compressor inlet falls below a predetermined minimum value. This maximum compressor speed is determined by reaching the minimum suction pressure at the compressor inlet, the speed limit for component protection of the compressor, and / or the noise / vibration behavior of the compressor. The minimum suction pressure at the compressor inlet is determined by the sealing concept of the heat pump arrangement and the resulting maximum negative pressure in the refrigerant circuit compared to the ambient pressure.

[0025] According to a preferred embodiment according to claim 9, the degree of opening of the chiller expansion valve regulates the air temperature at the evaporator air outlet. This avoids a two-solution control problem of the compressor speed when controlling the air temperature at the evaporator air outlet via the compressor speed.

[0026] In the advantageous embodiment according to claim 10, dehumidification with heat dissipation takes place via the outdoor heat exchanger. The electric coolant heater is activated when the outdoor heat exchanger expansion valve reaches a predetermined minimum opening value. This minimum opening value ensures a minimum required differential pressure across the expansion valve(s).

[0027] In dehumidification mode, it is possible to calculate the required coolant temperature at the chiller inlet with knowledge of the heat exchanger behavior, since the suction pressure level is defined by the cabin evaporator target temperature.

[0028] According to the advantageous embodiment according to claim 11, icing of the cabin evaporator is also prevented by controlling the electric coolant heater. The electric coolant heater increases the coolant temperature at the chiller coolant inlet and thus the suction pressure at the compressor inlet. This results in the evaporation temperature in the cabin evaporator rising, preventing icing.

[0029] According to the advantageous embodiment according to claim 12, the electric coolant heater is also used when switching from one operating mode to another to maintain the air temperature at the duct air outlet at the desired value. Since there is no air-side electric cabin heater, the compressor must operate continuously even during switching between operating modes. The electric coolant heater ensures the absorption of heat into the refrigerant circuit at the chiller, the necessary heating output in the cabin, and the necessary superheating of the refrigerant at the compressor inlet. In the next step, a predetermined opening of the bypass shutoff valve enables a controlled displacement of the liquid refrigerant stored in the external heat exchanger while ensuring refrigerant superheating upstream of the compressor.

[0030] The advantageous embodiment according to claim 13 relates to a concrete embodiment of the switching between the operating modes, whereby the external heat exchanger can be used as an evaporator.

[0031] According to the advantageous embodiment according to claim 14, the required heating output of the electric coolant heater is estimated mathematically, and this calculated value is used as the initial target value for controlling the electric coolant heater. If the desired heating output is not achieved, the heat absorption by the chiller is too low, or if the maximum compressor speed is not reached, the heat absorption by the chiller is too high, the initial target value is adjusted in a second control loop.

[0032] Further details, features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention. Fig. 1 shows a first embodiment with the structure of the heat pump arrangement, which is an essential part of a thermal management system for electric vehicles in heating mode, wherein the chiller, the compressor and the electric coolant heater are used as a heat source for heating the cabin; Fig. 2 shows the active components in heating mode after Fig. 1 in the pH diagram; Fig. 3 shows a Fig. 1 analog representation of a second embodiment in heating mode, wherein the chiller, the external heat exchanger, the compressor and the electric coolant heater are used as a heat source for heating the cabin; Fig. 4 shows the active components in heating mode after Fig. 3 in the pH diagram; Fig. 5 shows in combination with Fig. 1 shows a third embodiment of the invention, namely a dehumidification mode without heat emission to the environment; Fig. 6 shows a Fig. 1 analog representation of a fourth embodiment in dehumidification mode with heat dissipation to the environment via the external heat exchanger, wherein the chiller, the cabin evaporator, the compressor and the electric coolant heater are used as a heat source for heating the cabin; Fig. 7 shows in combination with Fig. 6 the active components of the fourth embodiment of the invention; Fig. Figure 8 shows schematically the switching from series dehumidification to parallel dehumidification via intermediate modes; Fig. 9 shows the decoupling of the large thermal mass of the battery through the coolant bypass; and Fig. 10 the structure of a thermal management system according to the state of the art.

[0033] Fig. 1 and Fig. 2 show a first embodiment of the invention. Fig. Figure 1 shows the structure of the heat pump assembly 1, which is an essential part of a thermal management system for electric vehicles in heating mode, wherein the chiller 80, the compressor 10, and the electric coolant heater 220 are used as a heat source for heating the cabin. The thermal management system according to Fig. 1 differs from the thermal management system according to Fig. 10 only by the absence of the electric cabin heater 300 and by the special design of the controller 400, which enables operation in the first and / or second start-up phase and in the heating phase. Additionally, a condenser air inlet 20-1, a condenser air outlet 20-2, an evaporator air inlet 60-1, and an evaporator air outlet 60-2 are shown in the HVAC duct 64. The duct air inlet 61-1 corresponds to the evaporator air inlet 60-1, while the duct air outlet 64-2 differs from the condenser air outlet 20-2 due to the air mixing flap 2. The valve unit 110 connects the first refrigerant inlet 111 to the second refrigerant outlet 114. The cabin evaporator expansion valve 50 is closed so that the refrigerant from the cabin condenser 20 is supplied to the chiller 80 via the chiller expansion valve 70.

[0034] Fig. 2 shows the active components in heating mode after Fig. 1 in the pH diagram. The electric coolant heater 220 is only activated when the compressor 10 is operating at its maximum speed, i.e., maximum heat output, and yet the heat absorbed in the chiller 80 and the compressor's waste heat are not sufficient for the desired heat output by the cabin condenser 20. The reference variable for controlling the heating output of the electric coolant heater 220 is the refrigerant pressure pD at the compressor outlet 12, and the reference variable for the degree of opening of the chiller expansion valve 70 is the refrigerant superheat SH Cho at the refrigerant-side chiller outlet 82 or the refrigerant superheat SH CPi at the compressor inlet 11. Alternatively, the reference variable is the refrigerant superheat SH Cho at the refrigerant-side chiller outlet 82 or the refrigerant superheat SH CPiat the compressor inlet 11, and the reference variable for the degree of opening of the chiller expansion valve 70 is the refrigerant pressure pD at the compressor outlet 12. The various control strategies ensure that the coolant temperature in the battery coolant circuit 200 remains as low as possible, so that heat losses to the environment remain small.

[0035] Fig. 3 and Fig. 4 show a second embodiment of the invention which differs from the first embodiment only in that, in addition to the chiller, ambient heat is used for cabin heating via the external heat exchanger 40 acting as an evaporator. This additionally provides the refrigerant superheat SH OHXo at the outdoor heat exchanger outlet 42 as a reference variable for the two control strategies.

[0036] The heating output of the electric coolant heater 220 is limited if the coolant temperature T CHiat the refrigerant-side chiller inlet 81 and thus the suction pressure at the compressor inlet 11 would be too high to allow heat absorption from the environment via the external heat exchanger 40. This also increases efficiency and limits the use of electrical energy from the battery.

[0037] Fig. 5 shows in combination with Fig. 1 shows a third embodiment of the invention, namely a dehumidification mode without heat loss to the environment. The compressor 10 is operated at maximum speed. The air temperature T is controlled by the degree of opening of the chiller expansion valve 70. aEo at the evaporator air outlet 60-2. The degree of opening of the cabin evaporator expansion valve 50 determines the refrigerant superheat SH Eoat the evaporator outlet 62. The electric coolant heater 220 is activated when the compressor 10 has reached its maximum speed or when the refrigerant superheat SHCho at the chiller outlet 82 or the refrigerant superheat SHCPi at the compressor inlet 11 falls below a predetermined minimum value. The heating output of the electric coolant heater 220 is controlled via the coolant pressure pD at the compressor outlet 12.

[0038] Fig. 6 and Fig. 7 shows a fourth embodiment of the invention, namely a dehumidification mode with heat dissipation to the environment. The air temperature T aEoThe speed of the compressor 10 is controlled at the evaporator air outlet 60-2. The distribution of the heat output between the cabin condenser 20 and the external heat exchanger 40, which operates as a condenser, is controlled via the external heat exchanger expansion valve 30. The refrigerant superheat SH is controlled via the opening degree of the cabin evaporator expansion valve 50. Eo at the evaporator outlet 62 and the degree of opening of the chiller expansion valve 70, the refrigerant superheat SH CHo at the refrigerant-side chiller outlet 82. The electric coolant heater 220 is switched on when the desired heating output for the cabin is insufficient and when the outdoor heat exchanger expansion valve 30 reaches a predetermined minimum opening value.

[0039] In the heating modes according to the Fig. 1 to 4 without and with heat absorption via the outdoor heat exchanger 40 and in dehumidification mode after Fig. 5 and Fig. 1. For dehumidification without heat dissipation via the external heat exchanger 40, the compressor 10 is operated at maximum speed. If the desired heating output for the cabin is not achieved, the electric coolant heater is switched on.

[0040] In the dehumidification modes - Fig. 5 and Fig. 7 - the required heating power of the electric coolant heater can be estimated mathematically on the basis of the following energy balance: Heating output of the electric coolant heater 220 = desired heating output for the cabin - heating output of the external heat exchanger 40 (not applicable in Fig. 6) - Waste heat output of the compressor 10 - latent part of the cabin evaporator output + heat loss to the environment

[0041] The waste heat of the compressor 10 can be further increased by dividing the air flow in the HVAC duct 64 from the evaporator air outlet 60-2 through or past the cabin condenser 20 in heating mode by means of the air mixing flap 2, thereby influencing the pressure pD at the compressor outlet 12 and thus the heat dissipation of the compressor 10 to the refrigerant. This allows the waste heat of the compressor 10 to be increased at a constant speed, thus reducing the need for the electric coolant heater 220.

[0042] Fig. Figure 8 schematically shows the switching from serial dehumidification, in which the outdoor heat exchanger 40 is used as a condenser, to parallel dehumidification, in which the outdoor heat exchanger 40 is used as an evaporator, via transition modes. Without an air-side electric cabin heater 300, it is necessary to keep the compressor 10 running continuously. The switching logic must maintain cabin comfort (heating capacity, dehumidification, low air temperature fluctuations) and prevent damage to the compressor 10 due to displacement of liquid refrigerant stored in the outdoor heat exchanger. This can occur especially when switching from a mode in which the outdoor heat exchanger 40 is used as a condenser and a large amount of liquid refrigerant is stored therein, to a mode in which the outdoor heat exchanger 40 is used as an evaporator.To prevent damage to the compressor 10 due to liquid surge, the refrigerant is slowly recovered by controlling the opening degree of an adjustable bypass shutoff valve 90 in the bypass line 100. The outdoor heat exchanger can then be used as an evaporator. To determine whether most of the refrigerant has been recovered and the risk of liquid refrigerant backflow reduced, the refrigerant superheat at the outdoor heat exchanger outlet 42 can be used as a criterion. Once the refrigerant superheat at the outdoor heat exchanger outlet 42 has stabilized, it can be assumed that most of the liquid refrigerant has been shifted from the outdoor heat exchanger 40 to the active part of the refrigeration circuit. The adjustable bypass shutoff valve 90 can be an expansion device or a valve with an intermediate stage and a small opening.To ensure the heating performance of the cabin during switching, the electric coolant heater 220 in the battery coolant circuit 200 is activated and the released heat is coupled into the coolant circuit via the chiller 80 and released to the cabin via the cabin condenser 20.

[0043] First, the chiller expansion valve 70, if closed, is opened and the electric coolant heater 220 is activated, or vice versa—first transition mode. Next, the outdoor heat exchanger expansion valve 30 is closed, and the adjustable bypass shutoff valve 90 is opened to a certain opening degree less than the maximum opening degree—second transition mode. After a certain duration or upon reaching a stable superheat at the compressor inlet 11, the outdoor heat exchanger expansion valve 30 is opened, and the adjustable bypass shutoff valve 90 is fully opened. Finally, in the target mode, the chiller expansion valve 70 is closed, and the outdoor heat exchanger 40 is used as an evaporator.

[0044] The electric coolant heater 220 is switched on during the described dehumidification modes Fig. 5 and Fig. 7 is also used to prevent icing of the cabin evaporator 60. The heat from the electric coolant heater 220 increases the coolant temperature TcCHi at the chiller coolant inlet and thus the suction pressure at the compressor inlet 11. This causes the evaporation temperature in the cabin evaporator 60 to rise, preventing icing.

[0045] Fig. 9 shows the battery coolant circuit 200 with a coolant bypass 250 and a valve device 260 in the form of a 3-way valve between the chiller coolant outlet and a point in the battery coolant circuit 200 between the electric coolant heater 220 and the battery 210. By controlling the 3-way valve 260, the large thermal mass of the battery 210 can be more or less decoupled from the battery coolant circuit 200 by the coolant bypass 250. If a very high heating output is required for the cabin when starting the electric vehicle at low ambient temperatures, heat from the electric coolant heater 220 can be used more or less completely for cabin heating, avoiding unnecessary heating of the large thermal mass of the battery. This allows the desired temperature in the cabin to be reached more quickly.

[0046] In the circuit diagrams according to Fig. 1, Fig. 3, and Fig. 6, a refrigerant collector is provided on the high-pressure side of the heat pump assembly 1 as part of the valve unit. Alternatively, the refrigerant collector can also be arranged on the low-pressure side of the heat pump assembly 1, directly upstream of the compressor 10. List of reference symbols 1 Heat pump arrangement 2 air mixing flap 10 compressors 11 Compressor inlet 12 Compressor outlet 20 Cabin condenser 20-1 Condenser air inlet 20-2 Condenser air outlet 21 Refrigerant-side condenser inlet 22 refrigerant-side condenser outlet 30 Outdoor heat exchanger expansion valve 40 outdoor heat exchangers 41 Refrigerant-side outdoor heat exchanger inlet 42 refrigerant-side outdoor heat exchanger outlet 50 Cabin evaporator expansion valve 60 cabin evaporators 60-1 Evaporator air inlet 60-2 Evaporator air outlet 61 refrigerant-side evaporator inlet 62 refrigerant-side evaporator outlet 64 HVAC duct 64-1 Duct air inlet 64-2 Duct air outlet 70 Chiller expansion valve 80 chillers 81 Refrigerant-side chiller inlet 82 Refrigerant-side chiller outlet 90 adjustable bypass shut-off valve 100 Bypass line for refrigerant between outdoor heat exchanger outlet and compressor inlet 110 Valve unit 111 first refrigerant inlet of 110 112 first refrigerant outlet of 110 113 second refrigerant inlet from 110 114 second refrigerant outlet from 110 200 Battery coolant circuit 210 high-voltage storage / battery 220 Electric coolant heater 230 waste heat absorption device 240 coolant pump 250 coolant bypass 260 valve device in 250 300 Electric cabin heater 400 Control pD refrigerant pressure at compressor outlet 12 p s Suction pressure at compressor inlet 11 SH Cho Refrigerant superheat at the refrigerant-side chiller outlet 82 SH CPi Refrigerant superheat at the compressor inlet 11 T alCo Air temperature at the condenser air outlet 20-2 T vent Air temperature at duct air outlet 64-2. T Chi Coolant temperature at the chiller coolant inlet 80-1 T aEo Air temperature at the evaporator air outlet 60-2

Claims

[1] Method for controlling a thermal management system for electric vehicles in different operating modes, which comprise heating, cooling and dehumidification of a cabin air of a vehicle cabin, wherein the thermal management system comprises a battery (210), an electric coolant heater (220), a heat pump arrangement (1) and a controller (400), the heat pump arrangement (1) comprising - a compressor (10) with a compressor inlet (11) and a compressor outlet (12), - a cabin condenser (20) with a refrigerant-side condenser inlet (21) and a refrigerant-side condenser outlet (22), - an outdoor heat exchanger expansion valve (30), - an outdoor heat exchanger (40) with a refrigerant-side outdoor heat exchanger inlet (41) and a refrigerant-side outdoor heat exchanger outlet (42), wherein the outdoor heat exchanger expansion valve (30) is connected to the outdoor heat exchanger inlet (41), - a chiller expansion valve (70) and a chiller (80) having a refrigerant-side chiller inlet (81) and a refrigerant-side chiller outlet (82), wherein the chiller expansion valve (70) is connected to the refrigerant-side chiller inlet (81), and - a cabin evaporator expansion valve (50) and a cabin evaporator (60) with a refrigerant-side evaporator inlet (61) and a refrigerant-side evaporator outlet (62), wherein the cabin evaporator expansion valve (50) is connected to the evaporator inlet (61), - wherein the cabin condenser (20) and the cabin evaporator (60) are arranged in an HVAC duct (64) for air as a coolant, - wherein the HVAC duct (64) has a duct air inlet (64-1) and a duct air outlet (64-2) opening into the vehicle cabin, - wherein the cabin condenser (20) has a condenser air inlet (20-1) and a condenser air outlet (20-2), and - wherein the cabin evaporator (60) has an evaporator air inlet (60-1) and an evaporator air outlet (60-2), - wherein the chiller (80) comprises a chiller coolant inlet and a chiller coolant outlet, and - wherein the electric coolant heater (220) is connected in series to a battery coolant circuit (200) with the battery (210), a waste heat absorption device (230) for coupling waste heat from the electric vehicle into the battery coolant circuit (200) and the chiller (80), characterized by , that the electric coolant heater (220) is only activated when predetermined operating parameters of the thermal management system are met, which are determined depending on the respective operating mode, and that in a heating mode the electric coolant heater (220) is only activated when the compressor (10) has reached a maximum speed and that the maximum speed of the compressor (10) is determined by reaching a minimum suction pressure at the compressor inlet (11), a speed limit for component protection of the compressor (10) and / or a noise / vibration behavior of the compressor (10). [2] Method according to claim 1, characterized bythat in heating mode, an air flow in the HVAC duct (64) from the cabin evaporator (60) through the cabin condenser (20) or past it is divided by means of an air mixing flap (2), whereby a pressure (pD) at the compressor outlet (12) and thus a heat release of the compressor (10) to the refrigerant is influenced. [3] Method according to claim 1 or 2, characterized by that a control of a heating output of the electric coolant heater (220) is carried out with at least one of the following operating parameters of the heat pump arrangement (1) as a reference variable: - Refrigerant pressure (pD) at the compressor outlet (12), - Refrigerant superheat (SH Cho ) at the refrigerant-side chiller outlet (82), - Refrigerant superheat (SH CPi ) at the compressor inlet (11), - Refrigerant superheat (SH OHXo ) at the outdoor heat exchanger outlet (42), - Air temperature (T alCo) at the condenser air outlet (20-2) and / or - Air temperature (T vent ) at the duct air outlet (64-2). [4] Method according to claim 3, characterized by that in heating mode the heating output of the electric coolant heater (220) is limited if the coolant temperature (T Chi ) at the refrigerant-side chiller inlet (81) and thus the suction pressure (p s ) at the compressor inlet (11) would be too large to allow heat absorption from the environment via the external heat exchanger (40). [5] Method according to claim 3 or 4, characterized by that in heating mode, the reference variable for controlling the heating output of the electric coolant heater (220) is the refrigerant pressure (pD) at the compressor outlet (12) and that the reference variable for the degree of opening of the chiller expansion valve (70) is the refrigerant superheat (SH Cho ) at the refrigerant-side chiller outlet (82) or the refrigerant superheat (SH CPi) at the compressor inlet (11). [6] Method according to claim 3 or 4, characterized by that in heating mode, the reference variable for controlling the heating output of the electric coolant heater (220) is the refrigerant superheat (SH Cho ) at the refrigerant-side chiller outlet (82) or the refrigerant superheat (SH CPi ) at the compressor inlet (11) and that the reference variable for the degree of opening of the chiller expansion valve (70) is the refrigerant pressure (pD) at the compressor outlet (12). [7] Method according to claim 1, characterized by that in dehumidification mode, the reference variable for controlling the heating output of the electric coolant heater (220) the refrigerant pressure (pD) at the compressor outlet (12), the air temperature (T alCo ) at the condenser air outlet (20-1), the air temperature (T vent ) at the duct air outlet (64-2), the refrigerant superheat (SH Cho) at the refrigerant-side chiller outlet (82), the refrigerant superheat (SH CPi ) at the compressor inlet (11) and the air temperature (TaEo) at the evaporator air outlet (60-2). [8] Method according to claim 7, characterized by that the outdoor heat exchanger (40) is deactivated and that the electric coolant heater (220) is activated when the compressor (10) has reached a maximum speed or when the refrigerant superheat (SH Cho , SH CPi ) at the refrigerant-side chiller outlet (82) or compressor inlet (11) falls below a predetermined minimum value. [9] Method according to claim 8, characterized by that the air temperature (TaEo) at the evaporator air outlet (60-2) is controlled via the degree of opening of the chiller expansion valve (70). [10] Method according to claim 7, characterized bythat the outdoor heat exchanger (40) is activated and that the electric coolant heater (220) is activated when the outdoor heat exchanger expansion valve (30) reaches a predetermined minimum opening value. [11] Method according to one of the preceding claims, characterized by that icing of the cabin evaporator (60) is prevented by controlling the heating output of the electric coolant heater (220). [12] Method according to one of the preceding claims, characterized by that when switching from an operating mode with the external heat exchanger (40) used as a condenser to an operating mode with the external heat exchanger (40) used as an evaporator, the electric coolant heater (220) is used to keep the heating power of the cabin and the air temperature at the duct air outlet (64-2) leading into the cabin constant and to ensure the superheating of the refrigerant at the compressor inlet (11). [13] Method according to claim 12, characterized by following procedural steps: a) opening the chiller expansion valve (70) and activating the electric coolant heater (220); b) closing the outdoor heat exchanger expansion valve (30); c) connecting the refrigerant-side external heat exchanger outlet (42) to the compressor inlet (11) via a bypass line (100) with a controllable bypass shut-off valve (90) by partially opening the controllable bypass shut-off valve (90) to a predetermined degree of opening; d) Fully opening the outdoor heat exchanger expansion valve (30) and full opening of the adjustable bypass shut-off valve (90) when a stable superheat of the refrigerant at the compressor inlet (11) is reached or the pressure in the outdoor heat exchanger (40) has equalised to the suction pressure at the compressor inlet (11) and e) Close the chiller expansion valve (70). [14] Method according to one of the preceding claims, characterized by that the required heating output of the electric coolant heater (220) is estimated mathematically and this mathematically determined value is used as an initial target value for controlling the electric coolant heater (220) and that the initial target value is adjusted if the heat absorption in the chiller (80) is too low or too high.

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