Thermal management system for a vehicle

Abstract

Thermal management system for a vehicle with a traction battery (23) and a passenger compartment, comprising: - a refrigeration circuit running entirely outside the passenger compartment, which splits downstream of a refrigerant compressor (1) into a first refrigeration sub-circuit with a first expansion valve (6) and a first chiller (7) and into a second refrigeration sub-circuit with a second expansion valve (8) and a second chiller (9), wherein the refrigeration sub-circuits merge downstream of the chillers (7, 9) and upstream of the refrigerant compressor (1), - a first cooling circuit, the coolant of which transfers heat to the refrigerant in the first chiller (7) and absorbs heat from the airflow cooling the passenger compartment in an air conditioning heat exchanger (17), - a second cooling circuit, the coolant of which transfers heat to the refrigerant in the second chiller (9) and exchanges heat with the traction battery (23), - a coolant-cooled condenser (2) and a third cooling circuit, the coolant of which absorbs heat from the refrigerant in the condenser (2) and, depending on a system mode that either cools or heats the passenger compartment, releases heat into the vehicle environment in an air-to-water heat exchanger (14) or into the passenger compartment in a heating heat exchanger (26), - a coolant valve (21) and a fourth cooling circuit running above it, which runs over a traction motor (31) of the vehicle and which the coolant valve (21) connects either in parallel to or in series with the second cooling circuit, - and a further coolant valve (22), wherein the coolant valves (21, 22) connect several or all cooling circuits either in parallel to each other or in series with each other, characterized in that the coolant valve (21) is a 9-way valve and that the further coolant valve (22) is an 8-way valve.

Description

[0001] The invention relates to a thermal management system for a vehicle with a traction battery and a passenger compartment, comprising: - a refrigeration circuit running entirely outside the passenger compartment, which splits downstream of a refrigerant compressor into a first refrigeration sub-circuit with a first expansion valve and a first chiller and into a second refrigeration sub-circuit with a second expansion valve and a second chiller, wherein the refrigeration sub-circuits merge downstream of the chillers and upstream of the refrigerant compressor, - a first cooling circuit, whose coolant transfers heat to the refrigerant in the first chiller and absorbs heat from the airflow cooling the passenger compartment in an air conditioning heat exchanger, - a second cooling circuit, whose coolant transfers heat to the refrigerant in the second chiller and exchanges heat with the traction battery, - a coolant-cooled condenser and a third cooling circuit, the coolant of which absorbs heat from the refrigerant in the condenser and, depending on a system mode that either cools or heats the passenger compartment, releases heat into the vehicle environment in an air-to-water heat exchanger or into the passenger compartment in a heating heat exchanger, - a coolant valve and a fourth cooling circuit running above it, which runs via a traction motor of the vehicle and which the coolant valve connects either in parallel to or in series with the second cooling circuit, - and another coolant valve, wherein the coolant valves connect several or all cooling circuits either in parallel or in series.

[0002] The thermal management system (WMS) of an electric vehicle typically encompasses the thermal management technologies for the passenger compartment, the traction battery, and the electric traction motor. The main modes that the WMS can currently implement for electric vehicles are passenger compartment cooling / heating, battery cooling / heating, dehumidification / defrosting, traction motor cooling, and waste heat recovery. Existing technical solutions include direct and indirect systems. The direct system exchanges heat with high heat exchange efficiency directly at the heat source / heat sink in a closed loop. The indirect system can make the entire cooling circuit more compact, but its heat exchange efficiency is lower compared to the direct system.

[0003] The air conditioning system consists primarily of refrigerant-side components such as refrigerant compressors, expansion valves, evaporators, and condensers, as well as coolant-side components such as water pumps, water valves, water-side heat exchangers, and coolant tanks. Cooling and heating of the passenger compartment is typically regulated by heat exchangers or PTC heaters in the HVAC (heating, ventilation, and air conditioning) system. The traction battery is cooled by a cold source provided by a battery cooler and heated primarily by a coolant heater connected in series with the battery water circuit. The traction motor usually dissipates heat via a radiator located at the front of the vehicle, or the waste heat may be recovered by a heat recovery system.Separate water pumps are provided for the traction motor and the battery cooling circuits to ensure coolant circulation.

[0004] Currently, the WMS uses a direct circuit to implement thermal management control of components (e.g., traction battery, traction motor, passenger compartment), which is not feasible for highly flammable refrigerants like propane. The current secondary circuit, typically consisting of a compressor, expansion valve, condenser, and evaporator, lacks sufficient capacity and efficiency due to heat losses to achieve the heating and cooling capacities and efficiencies of the direct circuit.

[0005] WMS for electric vehicles are known, among others, from CN 1 16 729 050 A, CN 1 16 787 991 A, CN 1 17 183 653 A and CN 1 17 584 687 A. DE 10 2020 206 728 A1 and DE 10 2022 210 903 A1 each disclose a vehicle WMS with propane (R-290) or with propane or butane (R-600) as the refrigerant.

[0006] DE 10 2009 060 860 A1 discloses an air conditioning system for a vehicle.

[0007] WMS of the type mentioned above are known from US 2024 / 0351394A1 and US 2024 / 0100909A1.

[0008] The present invention is based on the objective of providing an improved vehicle WMS that is particularly suitable for the low-risk use of highly flammable refrigerants.

[0009] The solution to this problem is provided by the features of independent claims 1 and 6. Accordingly, in a thermal management system according to the invention for a vehicle with a traction battery and a passenger compartment or a vehicle with such a WMS, the coolant valve is a 9-way valve and the other coolant valve is an 8-way valve.

[0010] The following proposes a WMS (Water Management System) using a hydrocarbon refrigerant (e.g., propane) for improved usability. By employing two chillers—one for the passenger compartment and one for the traction battery in the secondary circuit—cabin climate control and battery temperature regulation can be achieved simultaneously at different temperature levels.

[0011] Due to the fact that the refrigerant charge quantity is still under discussion by legislative authorities, there is no definitive statement regarding the value that can be used in the automotive sector. The systems proposed herein can be used with different charge quantities, e.g., 150 g, 300 g, 500 g.

[0012] The concept of energy cascade utilization is reflected in all the proposals mentioned here, which makes the system more efficient and powerful through the use of heat of different qualities.

[0013] Preferred further developments and embodiments of the invention are the subject of the dependent claims.

[0014] Further features of the invention will become apparent from the following description and from the drawing, which shows three exemplary WMS configurations, each depicted as a topology in different operating modes. Solid lines represent refrigerant or coolant lines currently flowing through them, and dashed lines represent lines currently not flowing through them. Unless otherwise stated, identical or functionally equivalent features or components are designated with the same reference numerals. The drawing shows: Fig. 1a the first WMS in dual climate control mode: passenger compartment and traction battery; Fig. 1b the first WMS in the first simple air conditioning mode: passenger compartment only; Fig. 1c the first WMS in the second simple air conditioning mode: traction battery only; Fig. 1d the first WMS in a first heating mode: passenger compartment and traction battery; Fig. 1e the first WMS in a second heating mode: passenger compartment and traction battery; Fig. 1f the first WMS in a third heating mode: passenger compartment and traction battery; Fig. 1g the first WMS in dehumidification mode; Fig. 2 the second WMS; Fig. 3a the third WMS in dual climate control mode: passenger compartment and traction battery; Fig. 3b the third WMS in simple air conditioning mode: passenger compartment only; Fig. 3c the third WMS in simple air conditioning mode: traction battery only; Fig. 3d the third WMS in a first dual heating mode: passenger compartment and traction battery; Fig. 3e the third WMS in a second double heating mode: passenger compartment and traction battery; Fig. 3f the third WMS in dehumidification mode; Fig. 3g, the third WMS in defrost mode.

[0015] The Fig. Figures 1a to 1g show the first embodiment of a WMS for a purely battery-electric vehicle in various operating modes. The WMS includes a refrigeration circuit using R-290 (propane) as the refrigerant. Due to the high flammability of propane and the associated risk of injury to passengers, the refrigeration circuit is located entirely outside the passenger compartment.

[0016] The refrigeration cycle runs – in the direction of flow – first through an electrically driven refrigerant compressor 1, a refrigerant-cooled condenser 2, a dryer 3, and a refrigerant-cooled subcooler 4 to a T-junction 5, where the refrigeration cycle splits downstream of the refrigerant compressor 1 into a first refrigeration sub-circuit and a second refrigeration sub-circuit. The first refrigeration sub-circuit runs through a first expansion valve 6 and a first chiller 7, and the second refrigeration sub-circuit runs through a second expansion valve 8 and a second chiller 9. The refrigeration sub-circuits rejoin at another T-junction 10 downstream of chillers 7 and 9 and upstream of the refrigerant compressor 1. The pressure and temperature of the refrigerant are measured by sensors 11 upstream and downstream of the refrigerant compressor 1.

[0017] The WMS comprises a first cooling circuit, in which the coolant transfers heat to the refrigerant in the first chiller 7. Depending on the system mode of the WMS, the first cooling circuit runs – in the direction of flow – via an electrically driven coolant pump 12, a coolant valve 13 designed as a 3-way valve, an air-to-water heat exchanger 14, a T-piece 15 branching off to the coolant valve 13, the first chiller 7, another coolant valve 16 also designed as a 3-way valve, an air conditioning heat exchanger 17, and a T-piece 18 branching off to the second coolant valve 16. The air conditioning heat exchanger 17 is part of an HVAC system 19 located in the passenger compartment, which is integrated into the Fig. 1 is framed with a dotted line, and cools the airflow entering the passenger compartment.

[0018] The WMS includes a second cooling circuit. This runs – also in the direction of flow and depending on the system mode of the WMS – via an electrically driven coolant pump 20, a coolant valve 21 designed as a 5-way valve, the second chiller 9, another coolant valve 22 also designed as a 5-way valve, a traction battery 23 and a PTC heating element 24.

[0019] The WMS includes a third cooling circuit. This circuit runs – also in the direction of flow and depending on the system mode of the WMS – via an electrically driven coolant pump 25, the additional coolant valve 22, a heating heat exchanger 26, a T-piece 27 branching off to the additional coolant valve 22, the subcooler 4 cooling the refrigerant, the condenser 2 cooling the refrigerant, a coolant valve 28 designed as a 3-way valve, the air-to-water heat exchanger 14, and another T-piece 29 branching off to the coolant valve 28. The heating heat exchanger 26 is also part of the HVAC system 19 and heats the airflow entering the passenger compartment.

[0020] The WMS includes a fourth cooling circuit. This circuit runs – also in the direction of flow and depending on the system mode of the WMS – via an electrically driven coolant pump 30, an electric traction motor 31 that drives the vehicle, a T-piece 32, another air-to-water heat exchanger 33, and the coolant valve 21, which branches off to the T-piece 32. The coolant valve 21 connects the second and fourth cooling circuits either in parallel (see, for example, the diagram below). Fig. 1a) or in a row with each other (see e.g. Fig. 1e).

[0021] Fig. 1a / Dual air conditioning mode: In this mode, the passenger compartment and the traction battery 23 are cooled simultaneously, requiring maximum cooling capacity. The refrigerant compressed by the refrigerant compressor 1 flows through both chillers 7 and 9. The heat in the refrigeration circuit is transferred to the third cooling circuit in the condenser 2 and dissipated to the environment via the air-to-water heat exchanger 14. The passenger compartment is cooled with refrigerant from the first chiller 7, and the traction battery 23 is cooled with refrigerant from the second chiller 9. The traction motor 31 is cooled as needed by means of the additional air-to-water heat exchanger 33.

[0022] Fig. 1b / first simple air conditioning mode: In this mode, the refrigeration circuit only cools the passenger compartment and the second chiller 9 is out of operation.

[0023] Fig. 1c / second simple air conditioning mode: In this mode, the refrigeration circuit only cools the traction battery 23 and the first chiller 7 is out of operation.

[0024] The in the Fig. The system modes shown in 1d to 1f are primarily used for heating the passenger compartment and the traction battery 23. In operating modes not shown, alternatively either only the passenger compartment or only the traction battery 23 can be heated.

[0025] Fig. 1d / First heating mode: This heat pump mode is one possible implementation for preheating the traction battery 23 and the passenger compartment, using the vehicle environment as a heat source. The first cooling circuit runs through the air-to-water heat exchanger 14, whose coolant absorbs heat from the vehicle environment. If necessary, in addition to heat pump operation, the PTC heating element 24 can also be switched on to provide additional heat for the passenger compartment. The fourth cooling circuit, operated by the coolant pump 30, is self-circulating to quickly heat the coolant in this circuit.

[0026] Fig. 1e / Second heating mode: Once the temperature has reached the desired value, the system can be switched to this mode. In this mode, the heat generated by the lossy traction motor 31 can be used to continuously heat the traction battery 23.

[0027] Fig. 1f / Third heating mode: If the temperature in the second and fourth cooling circuits of the traction battery 23 and the traction motor 31, respectively, is constant and sufficiently high, the system can switch to this mode. The cooling circuit also passes through the second chiller 9, which absorbs heat from the stationary circuit and supplies the heat pump to make the entire system more efficient. The ambient heat source can be switched off, depending on the amount of heat required in the actual situation.

[0028] Fig. 1g / Dehumidification mode: Dehumidification normally occurs at high humidity, regardless of the vehicle's heating or cooling requirements. When cooling is required, dehumidification can easily be achieved through the cooling function. For heating, heating and cooling must be implemented simultaneously in the HVAC system 19. In this case, heat is transferred from the condenser 2 to the heating heat exchanger 26, and cooling is supplied by the first chiller 7. Additionally, waste heat from the traction motor 31 and traction battery 23 is used as a heat source to make the heat pump more efficient and extend the vehicle's operating range in cold weather.

[0029] The in Fig. The second embodiment of a WMS shown in Figure 2 differs from the first WMS in that the dryer 3 and subcooler 4 are replaced by an internal heat exchanger 34 with an integrated accumulator. This makes the system more robust and compact. The subcooler 4 must be connected to the cooling circuit to provide subcooling. In contrast, the internal heat exchanger 34 can be implemented independently to achieve the same subcooling effect. Furthermore, the internal heat exchanger 34 and accumulator can be integrated into a single unit, which can make the overall package more compact.

[0030] The Fig. Figures 3a to 3g show the third embodiment of a WMS. With an increasing refrigerant charge – for example, 300g or 500g instead of just 150g – the refrigeration circuit is supplemented by an external heat exchanger 35, which is connected in series with the refrigerant-cooled condenser 2 via a third expansion valve 36. This increases the system performance when cooling demand is higher, e.g., at high ambient temperatures. Furthermore, the first chiller 7, which is primarily intended for cooling the passenger compartment, can also be used for cooling the traction battery 23, particularly in fast-charging scenarios.

[0031] In contrast to the preceding embodiments, the coolant valve 21 and the further coolant valve 22 are designed as 9-way valves with ports P1 to P9 and as 8-way valves with ports P1 to P8, respectively, in order to achieve more functions and make the system more efficient. The coolant valves 21 and 22 can connect several or all cooling circuits either in parallel or in series.

[0032] The refrigeration cycle runs upstream of the refrigerant compressor 1 via an internal heat exchanger 37, which transfers heat from the refrigerant from the high-pressure section running upstream of the expansion valves 6 and 8 to the low-pressure section of the refrigeration cycle running downstream of the chillers 7 and 9.

[0033] Fig. 3a / dual air conditioning mode: In this system mode, both cooling circuits running via chillers 7 and 9 are active, with the traction battery 23 and the passenger compartment being cooled simultaneously via the air conditioning heat exchanger 17.

[0034] Fig. 3b / first simple air conditioning mode: In this system mode, only the refrigeration circuit running via the first chiller 7 is active, cooling only the passenger compartment.

[0035] Fig. 3c / second simple air conditioning mode: In this system mode, only the refrigeration circuit running via the second chiller 9 is active, cooling only the traction battery 23.

[0036] Fig. 3D / first heating mode and Fig. 3e / Second heating mode: The passenger compartment and the traction battery 23 are heated. As a first step, the external heat exchanger 35 is used to extract heat directly from the environment, allowing the system to react more quickly. The waste heat is then recovered to form an energy cascade utilization concept that can improve system performance at low ambient temperatures. The second chiller 9 can also be used as a heat source for the heat pump if required. The heat generated by the heat pump can be distributed to the passenger compartment and battery circuits as needed via the coolant valves 21 and 22.

[0037] Fig. 3f / Dehumidification mode and Fig. 3g / Defrost mode: For these system modes, the WMS can be as efficient as possible by using the energy cascade utilization concept while simultaneously implementing the dehumidification and defrosting functions.

Claims

[1] Thermal management system for a vehicle with a traction battery (23) and a passenger compartment, comprising: - a refrigeration circuit running entirely outside the passenger compartment, which splits downstream of a refrigerant compressor (1) into a first refrigeration sub-circuit with a first expansion valve (6) and a first chiller (7) and into a second refrigeration sub-circuit with a second expansion valve (8) and a second chiller (9), wherein the refrigeration sub-circuits merge downstream of the chillers (7, 9) and upstream of the refrigerant compressor (1), - a first cooling circuit, the coolant of which transfers heat to the refrigerant in the first chiller (7) and absorbs heat from the airflow cooling the passenger compartment in an air conditioning heat exchanger (17), - a second cooling circuit, the coolant of which transfers heat to the refrigerant in the second chiller (9) and exchanges heat with the traction battery (23), - a coolant-cooled condenser (2) and a third cooling circuit, the coolant of which absorbs heat from the refrigerant in the condenser (2) and, depending on a system mode that either cools or heats the passenger compartment, releases heat into the vehicle environment in an air-to-water heat exchanger (14) or into the passenger compartment in a heating heat exchanger (26), - a coolant valve (21) and a fourth cooling circuit running above it, which runs over a traction motor (31) of the vehicle and which the coolant valve (21) connects either in parallel to or in series with the second cooling circuit, - and another coolant valve (22), wherein the coolant valves (21, 22) connect several or all cooling circuits either in parallel or in series with each other, characterized by , that the coolant valve (21) is a 9-way valve and that the other coolant valve (22) is an 8-way valve. [2] Thermal management system according to claim 1, characterized by that the refrigerant is propane. [3] Thermal management system according to claim 1 or 2, characterized by , that the first cooling circuit in the heating system mode runs via the air-water heat exchanger (14), whose coolant absorbs heat from the vehicle environment. [4] Thermal management system according to any one of claims 1 to 3, characterized by , that the refrigeration cycle runs via an external heat exchanger (35) which is connected in series with the condenser (2) via a third expansion valve (36). [5] Thermal management system according to claim 4, characterized by, that the refrigeration circuit runs downstream of the external heat exchanger (35) via an internal heat exchanger (37), which transfers heat of the refrigerant from a high-pressure part running upstream of the first expansion valve (6) and the second expansion valve (8) to a low-pressure part of the refrigeration circuit running downstream of the chillers (7, 9). [6] Vehicle with a thermal management system according to any of the preceding claims.

Images