Thermal management system of an electric vehicle and method for operating it

Abstract

Thermal management system (10) of an electric vehicle, comprising a cooling circuit (11) for temperature control of at least one high-voltage assembly (12) of the electric vehicle, comprising a heat pump circuit (13) for temperature control of a passenger compartment (14) of the electric vehicle, wherein the heat pump circuit (13) comprises a first heat exchanger (15) integrated into the cooling circuit (11), which is configured to heat a heat pump process medium by utilizing the thermal energy of a coolant of the cooling circuit, wherein the heat pump circuit (13) comprises a compressor (16) which is configured to compress the heat pump process medium downstream of the first heat exchanger (15), wherein the heat pump circuit (13) comprises a second heat exchanger (17) which is configured to transfer thermal energy of the compressed heat pump process medium to a sink medium for temperature control of the passenger compartment (14),wherein the heat pump circuit (13) has an expansion device (18) which is configured to expand the heat pump process medium downstream of the second heat exchanger (17), with a control unit (23) which is configured to control or regulate a volume flow or mass flow of the coolant through the first heat exchanger (15) depending on a setpoint output of the second heat exchanger (17) and depending on a temperature difference between an actual inlet temperature of the coolant in the first heat exchanger (15) and a setpoint outlet temperature of the sink medium from the second heat exchanger (17).

Description

[0001] The invention relates to a thermal management system of an electric vehicle. Furthermore, the invention relates to a method for operating a thermal management system of an electric vehicle.

[0002] An electric vehicle has at least one electric motor that provides drive power to an output of the electric vehicle. The electrical energy for driving the at least one electric motor is stored in at least one so-called traction battery of the electric vehicle. The at least one electric motor and the at least one traction battery are among the so-called high-voltage components of the electric vehicle. The high-voltage components also include so-called power electronics. It is known that an electric vehicle has a cooling circuit for controlling the temperature, in particular for cooling, of at least one high-voltage component of the electric vehicle.

[0003] It is known that an electric vehicle has a heat pump circuit for controlling the temperature of a passenger compartment. Such a heat pump circuit has a first heat exchanger configured to heat a heat pump process medium, a compressor configured to compress the heat pump process medium downstream of the first heat exchanger, a second heat exchanger configured to transfer thermal energy from the heat pump process medium compressed by the compressor to a sink medium for controlling the temperature of the passenger compartment, and an expansion device configured to expand the heat pump process medium downstream of the second heat exchanger.The first heat exchanger of the heat pump circuit can be integrated into the cooling circuit, which serves to control the temperature of at least one high-voltage module, in order to heat the heat pump process medium by utilizing the thermal energy of the coolant of the cooling circuit.

[0004] If, in a thermal management system of an electric vehicle with such a cooling circuit and such a heat pump circuit, little thermal energy is transferred from the heat pump process medium to the sink medium in the area of ​​the second heat exchanger, this can lead to the heat pump circuit compressor operating in intermittent mode, in which the compressor is running for a time and shutting down for a time. Such intermittent operation of the heat pump circuit compressor is disadvantageous for acoustic reasons, and it also reduces the compressor's service life.

[0005] WO 2017 / 061 972 A1 discloses a heat pump system for an electric vehicle.

[0006] DE 10 2022 203 667 A1 discloses a thermal management circuit for an electric vehicle.

[0007] DE 10 2019 131 480 A1 discloses a thermal management module of an electric vehicle.

[0008] There is a need for a thermal management system for an electric vehicle in which cycling, which is acoustically detrimental and reduces the compressor's service life, is avoided as far as possible or, ideally, completely.

[0009] The object of the invention is to create a novel thermal management system for an electric vehicle and a method for operating the same. This object is achieved by a thermal management system for an electric vehicle according to claim 1 and by a method according to claim 6.

[0010] The thermal management system of an electric vehicle according to the invention has a cooling circuit for controlling the temperature of at least one high-voltage module of the electric vehicle.

[0011] The thermal management system of an electric vehicle according to the invention further comprises a heat pump circuit for controlling the temperature of a passenger compartment of the electric vehicle.

[0012] The heat pump circuit has a first heat exchanger integrated into the cooling circuit, which is configured to heat a heat pump process medium by utilizing the thermal energy of the coolant of the cooling circuit, wherein the heat pump circuit further has a compressor configured to compress the heat pump process medium downstream of the first heat exchanger, wherein the heat pump circuit further has a second heat exchanger configured to transfer thermal energy of the heat pump process medium compressed by the compressor to a sink medium for tempering the passenger compartment of the electric vehicle, and wherein the heat pump circuit further has an expansion device configured to expand the heat pump process medium downstream of the second heat exchanger and upstream of the first heat exchanger.

[0013] The thermal management system of an electric vehicle according to the invention further comprises a control unit which is configured to control or regulate a volume flow or mass flow of the coolant of the cooling circuit via the first heat exchanger depending on a desired output of the second heat exchanger and depending on a temperature difference between an actual inlet temperature of the coolant of the cooling circuit in the first heat exchanger or a temperature corresponding to this actual inlet temperature and a desired outlet temperature of the sink medium from the second heat exchanger.

[0014] The method according to the invention makes it possible to reduce or even completely avoid cyclic operation of the compressor in the heat pump circuit, which is acoustically disadvantageous and reduces the compressor's service life. For this purpose, the control unit controls or regulates the volume flow or mass flow of the coolant in the cooling circuit via the first heat exchanger of the heat pump circuit. This control or regulation of the volume flow or mass flow of the coolant in the cooling circuit via the first heat exchanger takes place depending on the target output of the second heat exchanger and depending on the temperature difference between the actual inlet temperature of the coolant in the heat exchanger or a temperature corresponding to this actual temperature and the target outlet temperature of the sink medium from the second heat exchanger.

[0015] Preferably, the control unit is configured to control or regulate the volume flow or mass flow of the coolant of the cooling circuit via the first heat exchanger, depending on the target output of the second heat exchanger and depending on the temperature difference between the actual inlet temperature of the coolant into the first heat exchanger or the temperature corresponding to this actual inlet temperature and the target outlet temperature of the sink medium from the second heat exchanger, such that the compressor of the heat pump circuit is operated continuously. This is particularly preferred and enables continuous operation of the compressor of the heat pump circuit, so that acoustically disadvantageous and service life-reducing cyclic operation for the compressor of the heat pump circuit can be completely avoided.

[0016] Preferably, the control unit specifies a speed of a pump of the cooling circuit for conveying a coolant of the cooling circuit and in particular also a position of at least one valve which, depending on its position, guides the coolant flow conveyed by the pump at least partially via the first heat exchanger and / or at least partially via a bypass past the first heat exchanger.

[0017] The heating of the heat pump process medium in the region of the first heat exchanger can be advantageously adjusted via the speed of the cooling circuit pump and the position of the at least one valve, which is positioned upstream of the first heat exchanger in the flow direction of the coolant and, depending on the coolant, is guided at least partially via the first heat exchanger and / or at least partially past the first heat exchanger, in order to enable continuous operation of the compressor of the heat pump circuit even with a low power draw in the region of the second heat exchanger, i.e. when only a small amount of thermal energy is transferred from the heat pump process medium to the sink medium. Even with very low power draws in the region of the second heat exchanger, the compressor of the heat pump circuit can then be operated continuously in the range of its minimum speed.

[0018] Preferably, the control unit determines the volume flow or mass flow of the coolant of the cooling circuit via the first heat exchanger depending on the target output of the second heat exchanger and depending on the temperature difference between the actual inlet temperature of the coolant of the cooling circuit into the first heat exchanger or the temperature corresponding to this actual inlet temperature and the target outlet temperature of the sink medium from the second heat exchanger, in a characteristic-curve-dependent or characteristic-map-dependent manner. The characteristic-map-dependent or characteristic-curve-dependent determination of the target volume flow or mass flow of the coolant via the first heat exchanger and, depending thereon, the specification of the speed for the pump of the cooling circuit and / or the specification of the position of at least one valve of the cooling circuit is particularly simple on the control side and therefore preferred.

[0019] Preferred developments of the invention emerge from the subclaims and the following description.

[0020] Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being limited thereto. Fig. 1 shows a highly schematic section of a thermal management system of an electric vehicle.

[0021] Fig. Figure 1 shows a highly schematic section of a thermal management system 10 of an electric vehicle. The thermal management system 10 has a cooling circuit 11, which Fig. 1 is only partially shown and which serves to control the temperature of at least one high-voltage module 12 of the electric vehicle.

[0022] The at least one high-voltage assembly 12 of the electric vehicle may be, for example, an electric machine, a traction battery, power electronics or the like.

[0023] The thermal management system 10 also has a heat pump circuit 13, which serves to regulate the temperature of a passenger compartment 14 of the electric vehicle. The passenger compartment 14 is also referred to as the passenger cell.

[0024] The heat pump circuit 13 has a first heat exchanger 15 integrated into the cooling circuit 11, which is configured to heat a heat pump process medium by utilizing the thermal energy of the coolant of the cooling circuit 11.

[0025] The first heat exchanger 15 is also called a chiller.

[0026] The heat pump circuit 13 further comprises a compressor 16 which is configured to compress the heat pump process medium downstream of the first heat exchanger 15.

[0027] Furthermore, the heat pump circuit 13 has a second heat exchanger 17 which is configured to transfer thermal energy of the heat pump process medium compressed by the compressor 16 to a sink medium for tempering, preferably for heating, the passenger compartment 14 of the electric vehicle.

[0028] This sink medium is, in particular, air to be supplied to the passenger compartment 14. However, the sink medium can also be a liquid, such as water.

[0029] Furthermore, the heat pump circuit 13 has an expansion device 18 configured to expand the heat pump process medium downstream of the second heat exchanger 17 and upstream of the first heat exchanger 15. In the illustrated embodiment, this expansion device 18 is a throttle or, alternatively, a valve whose opening position can be changed.

[0030] When the heat pump circuit 13 is active for controlling the temperature of the passenger compartment 14 of the electric vehicle, the expansion device 18 is integrated into the heat pump circuit 13 and closes it. If, however, the heat pump circuit 13 is inactive, Fig. 1 the expansion device 18 is moved out of the heat pump circuit 13 and a separation point 19 interrupts the heat pump circuit 13.

[0031] According to Fig. 1, the cooling circuit 11, which serves to control the temperature of at least one high-voltage module 12 of the electric vehicle, has a pump 20 upstream of the first heat exchanger 15, the speed of which pump determines the coolant flow through the cooling circuit 11.

[0032] In Fig. 1, a valve 21 is arranged downstream of the pump 20 and upstream of the first heat exchanger 15, which is integrated into both the cooling circuit 11 and the heat pump circuit 13.

[0033] The position of valve 21 can be used to adjust the flow of coolant through the first heat exchanger 15 and through a bypass 22 extending parallel to the first heat exchanger 15. This makes it possible to direct all of the coolant through the first heat exchanger 15 or all of the coolant through the bypass 22 past the first heat exchanger 15. The valve 21 can also be used to variably divide the coolant flow downstream of the pump 20, so that a first portion of the coolant flow flows through the first heat exchanger 15 and a second portion of the coolant flow flows through the bypass 22 past the first heat exchanger 15.

[0034] The thermal management system 10 further comprises a control unit 23. This control unit 23 is configured to control or regulate a volume flow or mass flow of the coolant via the first heat exchanger 15 as a function of a target output, in particular a target heating output, of the second heat exchanger 17 and as a function of a temperature difference between an actual inlet temperature of the coolant of the cooling circuit 11 into the first heat exchanger 15 and a target outlet temperature of the sink medium from the second heat exchanger 17, or as a function of a temperature difference between a temperature corresponding to the actual inlet temperature of the coolant of the cooling circuit 11 into the first heat exchanger 15 and the target outlet temperature of the sink medium from the second heat exchanger 17. The target output orThe target heating output of the second heat exchanger 17 depends in particular on a difference between the target temperature of the passenger compartment 14 and the actual temperature of the passenger compartment 14. Likewise, the target outlet temperature of the sink medium from the second heat exchanger 17 depends in particular on this temperature difference between the target temperature and the actual temperature of the passenger compartment 14. In . Fig. 1, a temperature sensor 24 provides the control unit with the actual temperature of the coolant downstream of the pump 20 and thus a temperature corresponding to the actual inlet temperature of the coolant into the first heat exchanger 15.

[0035] Depending on the target output, in particular the target heating output, of the second heat exchanger 17 and depending on the above-mentioned temperature difference between the actual inlet temperature of the coolant in the first heat exchanger 15 or the temperature corresponding to this actual temperature and the target outlet temperature of the sink medium from the second heat exchanger 17, the volume flow or mass flow of the coolant via the first heat exchanger 15 is controlled or regulated by the control unit 23 in such a way that the compressor 16 of the heat pump circuit 13 is operated continuously, thus avoiding cyclic operation of the same in which it is switched on and off.

[0036] With a low target heating output of the second heat exchanger 17 and / or a small temperature difference between the actual inlet temperature of the coolant into the first heat exchanger 15 and the target outlet temperature of the sink medium from the second heat exchanger 17, the volume flow or mass flow of the coolant through the first heat exchanger 15 is controlled or regulated to such a low target value that the compressor 16 can be operated continuously at preferably minimum speed.

[0037] In order to control and / or regulate the volume flow or mass flow of the coolant through the first heat exchanger 15, the control unit 23 specifies a speed for the pump 20, depending on which speed the pump 20 pumps coolant through the cooling circuit 11. Preferably, the control unit 23 additionally specifies a position for the valve 21 for regulating or controlling the volume flow or mass flow of the coolant via the first heat exchanger 15, which, depending on its position, guides the coolant flow conveyed by the pump at least partially via the first heat exchanger 15 and / or at least partially past the first heat exchanger 15 via the bypass 22.

[0038] The volume flow or mass flow of the coolant of the cooling circuit 11 through the first heat exchanger 15 is determined by the control unit 23 preferably in a map-dependent or characteristic-dependent manner, specifically depending on the target output of the second heat exchanger 17 and depending on the temperature difference between the actual inlet temperature of the coolant into the first heat exchanger 15 or the temperature corresponding to this actual inlet temperature and the target outlet temperature of the sink medium from the second heat exchanger 17.

[0039] Thus, a characteristic map is preferably stored in the control unit 23, depending on the above-mentioned target output of the second heat exchanger and depending on the above-mentioned temperature difference, on the basis of which the volume flow or mass flow of the coolant through the first heat exchanger 15 is determined. Depending on the thus determined volume flow or mass flow, the speed for the pump 20 and the position for the valve 21 can be determined and specified by the control unit 23 via further characteristic maps or characteristic curves. Such a map-dependent or characteristic-curve-dependent control is simple and therefore particularly preferred.

[0040] The speed of pump 20 can preferably be adjusted continuously or in multiple stages between a maximum speed and a minimum speed. The position of valve 21 can preferably be adjusted continuously or in multiple stages between a position in which the entire coolant flow flows through first heat exchanger 15 and a position in which the entire coolant flow flows through bypass 22.

[0041] With the present invention, it is therefore possible to continuously operate the compressor 16 of the heat pump circuit 13, whose first heat exchanger 15 is also integrated into the cooling circuit 11 for tempering at least one high-voltage module 12, while reducing or even avoiding cyclic operation.

[0042] For this purpose, the volume flow or mass flow of the coolant through the first heat exchanger 15 is controlled or regulated depending on the target output of the second heat exchanger 17 and depending on the temperature difference between the actual inlet temperature of the coolant into the first heat exchanger 15 or the temperature corresponding thereto and the target outlet temperature of the sink medium from the second heat exchanger.

[0043] With a low power consumption in the area of ​​the second heat exchanger 17, the compressor 16 of the heat pump circuit 13 can be operated continuously, in particular at its minimum speed, by reducing the volume flow or mass flow through the first heat exchanger 15.

[0044] The volume flow or mass flow through the first heat exchanger 15 determines the thermal energy that can be transferred from the coolant to the heat pump process medium in the region of the first heat exchanger 15. The lower this volume flow or mass flow, the less thermal energy can be used to heat the heat pump process medium from the coolant of the cooling circuit 11.

Claims

[1] Thermal management system (10) of an electric vehicle, with a cooling circuit (11) for controlling the temperature of at least one high-voltage module (12) of the electric vehicle, with a heat pump circuit (13) for tempering a passenger compartment (14) of the electric vehicle, wherein the heat pump circuit (13) has a first heat exchanger (15) integrated into the cooling circuit (11), which is designed to heat a heat pump process medium by utilizing the thermal energy of a coolant of the cooling circuit (11), wherein the heat pump circuit (13) comprises a compressor (16) which is arranged to compress the heat pump process medium downstream of the first heat exchanger (15), wherein the heat pump circuit (13) has a second heat exchanger (17) which is designed to transfer thermal energy of the heat pump process medium compressed by the compressor (16) to a sink medium for tempering the passenger compartment (14) of the electric vehicle, wherein the heat pump circuit (13) comprises an expansion device (18) which is designed to expand the heat pump process medium downstream of the second heat exchanger (17) and upstream of the first heat exchanger (15), with a control unit (23) which is set up to control or regulate a volume flow or mass flow of the coolant of the cooling circuit (11) via the first heat exchanger (15) depending on a desired output of the second heat exchanger (17) and depending on a temperature difference between an actual inlet temperature of the coolant of the cooling circuit (11) in the first heat exchanger (15) or a temperature corresponding to this actual inlet temperature and a desired outlet temperature of the sink medium from the second heat exchanger (17). [2] Thermal management system (10) according to claim 1, characterized bythat the control unit (23) is set up, depending on the target output of the second heat exchanger (17) and depending on the temperature difference between the actual inlet temperature of the coolant of the cooling circuit (11) in the first heat exchanger (15) or the temperature corresponding to this actual inlet temperature and the target outlet temperature of the sink medium from the second heat exchanger (17), to control or regulate the volume flow or mass flow of the coolant of the cooling circuit (11) via the first heat exchanger (15) in such a way that the compressor (16) of the heat pump circuit (13) is operated continuously. [3] Thermal management system (10) according to claim 1 or 2, characterized by that the control unit (23) specifies a speed of a pump (20) of the cooling circuit (11) for conveying the coolant of the cooling circuit (11). [4] Thermal management system (10) according to claim 3, characterized byin that the control unit (23) specifies a position of at least one valve (21) which, depending on its position, guides the coolant flow conveyed by the pump (20) at least partially via the first heat exchanger (15) and / or at least partially via a bypass (22) past the first heat exchanger (15). [5] Thermal management system (10) according to one of claims 1 to 4, characterized by that the control unit (23) determines the volume flow or mass flow of the coolant via the first heat exchanger (15) depending on the target output of the second heat exchanger (17) and depending on the temperature difference between the actual inlet temperature of the coolant of the cooling circuit (11) in the first heat exchanger (15) or the temperature corresponding to this actual inlet temperature and the target outlet temperature of the sink medium from the second heat exchanger (17) in a characteristic-curve-dependent or characteristic-map-dependent manner. [6] Method for operating a thermal management system (10) of an electric vehicle, which has a cooling circuit (11) for controlling the temperature of at least one high-voltage module (12) of the electric vehicle, and which has a heat pump circuit (13) for tempering a passenger compartment (14) of the electric vehicle, wherein the heat pump circuit (13) has a first heat exchanger (15) integrated into the cooling circuit (11), which is designed to heat a heat pump process medium by utilizing the thermal energy of a coolant of the cooling circuit (11), wherein the heat pump circuit (13) comprises a compressor (16) which is arranged to compress the heat pump process medium downstream of the first heat exchanger (15), wherein the heat pump circuit (13) has a second heat exchanger (17) which is designed to transfer thermal energy of the heat pump process medium compressed by the compressor (16) to a sink medium for tempering the passenger compartment (14) of the electric vehicle, wherein the heat pump circuit (13) comprises an expansion device (18) which is designed to expand the heat pump process medium downstream of the second heat exchanger (17) and upstream of the first heat exchanger (15), wherein a volume flow or mass flow of the coolant of the cooling circuit (11) via the first heat exchanger (15) is controlled or regulated depending on a target output of the second heat exchanger (17) and depending on a temperature difference between an actual inlet temperature of the coolant of the cooling circuit (11) in the first heat exchanger (15) or a temperature corresponding to this actual inlet temperature and a target outlet temperature of the sink medium from the second heat exchanger (17). [7] Method according to claim 6, characterized by that the volume flow or mass flow of the coolant of the cooling circuit (11) is controlled or regulated via the first heat exchanger (15) in such a way that the compressor (16) of the heat pump circuit (13) is operated continuously. [8] Method according to claim 6 or 7, characterized bythat for this purpose a speed of a pump (20) of the cooling circuit (11) for conveying the coolant of the cooling circuit (11) is influenced. [9] Method according to claim 8, characterized by in that for this purpose a position of at least one valve (21) is influenced which, depending on its position, guides the coolant flow conveyed by the pump (20) at least partially via the first heat exchanger (15) and / or at least partially past the first heat exchanger (15). [10] Method according to one of claims 6 to 9, characterized bythat the volume flow or mass flow of the coolant of the cooling circuit (11) via the first heat exchanger (15) is determined depending on the desired output of the second heat exchanger (17) and depending on the temperature difference between the actual inlet temperature of the coolant of the cooling circuit (11) in the first heat exchanger (15) or the temperature corresponding to this actual inlet temperature and the desired outlet temperature of the sink medium from the second heat exchanger (17) in a characteristic curve-dependent or characteristic map-dependent manner.

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