Thermal management system for a motor vehicle with a loop heat pipe

Abstract

The invention relates to a thermal management system for a motor vehicle, comprising: - a first vehicle component (F1) with a cooling unit (12), - a second vehicle component (F2) arranged at a distance from the first vehicle component (F1), wherein the first vehicle component (F1) and the second vehicle component (F2) have different cooling requirement periods, - a cooling circuit carrying a cooling fluid, to which the cooling unit (12) of the first vehicle component (F1) is connected, wherein the cooling unit (12) is capable of being actively cooled by a cooling fluid (11) of the cooling circuit during initial cooling requirement periods of the first vehicle component (F1), and - a loop heat pipe (LHP) thermally coupled to the two vehicle components (F1, F2), which is designed for passive cooling of the second vehicle component (F2) to transfer waste heat (19) of the second vehicle component (F2) to the cooling unit (12) of the first vehicle component (F1), wherein the cooling unit (12) is permeable to the cooling fluid (11) of the cooling circuit for the removal of the waste heat (19) of the second vehicle component (F2) during the second cooling requirement periods of the second vehicle component (F2).

Description

[0001] The invention relates to a thermal management system for a motor vehicle. The invention also relates to a motor vehicle with a thermal management system.

[0002] This paper focuses on thermal management systems for electrified vehicles, i.e., hybrid or electric vehicles. Electrified vehicles have various components, such as at least one electric traction motor or drive motor, a rechargeable traction battery (e.g., a high-voltage energy storage device) to power the electric drive motor, an on-board charger for charging the traction battery, power electronics, etc. The thermal management system performs various temperature control tasks within the vehicle, including the dissipation of waste heat, i.e., the cooling of these vehicle components. For this purpose, the thermal management system can, for example, include at least one cooling circuit with a coolant flow, to which coolant-filled cooling units of the vehicle components, such as cooling plates or housings, are connected.

[0003] To circulate the coolant, at least one pump is installed in the cooling circuit. This pump is activated by a control unit whenever at least one of the vehicle components in this cooling circuit requires cooling. The more vehicle components connected to the same cooling circuit, the more powerful the pump must be, as it must be able to circulate the coolant even if the connected components have different cooling requirements due to varying operating times. Furthermore, connecting a large number of vehicle components, distributed and spaced apart within the vehicle, to the same cooling circuit can result in complex piping with very long and undesirably convoluted sections.

[0004] The object of the present invention is to provide an efficient, cost-effective and simple cooling system for at least two vehicle components of a motor vehicle.

[0005] This problem is solved according to the invention by a thermal management system and a motor vehicle with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description, and the figures.

[0006] A thermal management system according to the invention for a motor vehicle comprises a first vehicle component with a cooling unit and a second vehicle component arranged at a distance from the first vehicle component, wherein the first and the second vehicle components have different cooling requirement periods. Furthermore, the thermal management system comprises a cooling circuit carrying a coolant fluid, to which the cooling unit of the first vehicle component is connected, wherein the cooling unit is permeable to the coolant fluid of the cooling circuit for the active cooling of the first vehicle component during the first cooling requirement periods of the first vehicle component.Furthermore, the thermal management system features a loop heat pipe thermally coupled to the two vehicle components, which is designed for passive cooling of the second vehicle component by transferring waste heat from the second vehicle component to the cooling unit of the first vehicle component, whereby the cooling unit is permeable to the cooling fluid of the cooling circuit for the purpose of removing the waste heat from the second vehicle component during periods when the second vehicle component is required for cooling.

[0007] A motor vehicle according to the invention comprises a thermal management system according to the invention. The motor vehicle is, in particular, designed as an electrified motor vehicle. The motor vehicle comprises a plurality of vehicle components, for example, an electric drive motor, a traction battery, and an on-board charger. The first vehicle component is, in particular, the electric drive motor that can be supplied from the traction battery, and the second vehicle component is, in particular, the on-board charger for rectifying an alternating current, supplied, for example, by an external charging station, for charging the traction battery.

[0008] The thermal management system also includes a cooling circuit that carries a cooling fluid. This cooling circuit may have lines that carry a cooling fluid, such as a coolant. Furthermore, at least one pump for circulating the cooling fluid may be connected to the cooling circuit. Additionally, valves for controlling the flow of the cooling fluid, as well as cooling devices, such as a heat exchanger for dissipating heat to the vehicle's surroundings, may be connected to the cooling circuit. The first vehicle component is also connected to the cooling circuit by means of lines within the cooling circuit, allowing the cooling fluid to flow through it. The cooling unit may, for example, be formed by a housing of the first vehicle component, the housing of which has at least one flow-through cooling channel.In the case of an electric drive machine, the housing can, for example, be a cooling jacket surrounding the stator of the drive machine with a meandering cooling channel, which directs the cooling fluid along an outer side of the stator and can thus absorb waste heat from the electric drive machine during operation and transport it away via the cooling fluid.

[0009] The two vehicle components have different, non-overlapping cooling requirement periods, particularly due to differing operating times. For example, one vehicle component is always idle or out of operation when the other vehicle component is in operation and therefore requires cooling. Specifically, both vehicle components may have shared, overlapping idle times, but not shared, overlapping operating times, and therefore non-overlapping cooling requirement periods. For example, the first cooling requirement periods of the drive motor correspond to the discharge cycles of the traction battery to supply the electric drive motor, and the second cooling requirement periods of the on-board charger correspond to the charging cycles of the traction battery via an external charging station.

[0010] Due to the different cooling requirements, only the first vehicle component is directly connected to the cooling circuit via its cooling unit. The first vehicle component thus transfers its waste heat directly to the cooling fluid of the unit, which is supplied with cooling fluid during the first cooling requirement period. The second vehicle component is positioned at a distance from the first vehicle component and is only indirectly connected to the cooling circuit via a heat transfer device. The second vehicle component thus transfers its waste heat indirectly to the cooling fluid of the unit, which is supplied with cooling fluid during the second cooling requirement period as well.Preferably, the thermal management system includes a control device designed to activate the pump of the cooling circuit during the cooling requirement periods of the first and second vehicle components to provide a flow through the cooling unit of the first vehicle component.

[0011] The heat transfer system consists of a loop heat pipe (LHP), which thermally couples the second vehicle component to the cooling unit of the first vehicle component. The loop heat pipe is a two-phase heat exchanger that utilizes capillary action to remove heat from the second vehicle component and passively transport it to the cooling unit of the first vehicle component. For this purpose, the loop heat pipe can comprise a ring-shaped, closed pipe filled with a working fluid, an evaporation unit, and a condensation unit, with the evaporation unit being thermally coupled to the second vehicle component and the condensation unit being thermally coupled to the cooling unit of the first vehicle component.The pipeline has a supply section from the evaporator to the condenser, in which the working fluid is converted from a liquid to a gaseous phase by absorbing waste heat from the second vehicle component. The pipeline also has a return section from the condenser to the evaporator, in which the working fluid is converted back from the gaseous to the liquid phase by transferring waste heat to the cooling unit. The working fluid is transported passively by capillary action and a pressure gradient within the pipeline.

[0012] Within the loop heat pipe, the working fluid exists in two phases. In the inlet section, the working fluid is gaseous, and in the outlet section, it is liquid. The phase transition to the other phase occurs at the evaporation unit and the condensation unit. The waste heat is transferred to the working fluid via the evaporation unit, which is thermally coupled to the second vehicle component. The working fluid then transitions from the liquid to the gaseous phase, absorbing the waste heat. For this purpose, the evaporation unit can incorporate a highly thermally conductive plate, such as a copper plate, which is located on or within a housing of the second vehicle component. A capillary structure within the evaporation unit creates the spatial separation between the liquid and gaseous phases of the working fluid. During evaporation from the capillary structure, a pressure difference arises due to phase expansion.Here, the capillary structure saturated with liquid working fluid acts as a check valve, allowing the gaseous working fluid to flow with minimal pressure loss along the inlet section of the pipe towards the condenser. The condenser can be located on or inside a housing of the first vehicle component, which also forms the cooling unit. The waste heat is transferred to the cooling unit of the first vehicle component via the condenser, and the working fluid thus transitions back from the gaseous to the liquid phase. The liquid working fluid then flows back to the evaporator in the return section. The working fluid therefore flows throughout the entire loop heat pipe system due to a temperature and consequently a pressure gradient, as well as due to the capillary effect. The loop heat pipe thus requires no pumps or controls to activate the heat transfer.Furthermore, the loop heatpipe has the advantage that its pipe has a significantly smaller flow diameter than the cooling fluid-carrying lines of the cooling circuit and can therefore be installed in the vehicle in a particularly space- and weight-saving manner, even over larger distances between the vehicle components.

[0013] Passive connection of the second vehicle component to the cooling unit, which acts as a heat exchanger, also has the advantage that the cooling fluid only needs to be circulated through the cooling unit of the first vehicle component to cool both components. This allows the pump to be less powerful and therefore more cost-effective. Furthermore, no additional component, such as a heat exchanger, needs to be integrated into the cooling circuit.

[0014] The embodiments and advantages presented with reference to the thermal management system according to the invention apply accordingly to the motor vehicle according to the invention.

[0015] Further features of the invention will become apparent from the claims, the figure, and the figure description. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the figure description and / or shown in the figure alone, are not only usable in the combinations specified, but also in other combinations or individually.

[0016] The invention will now be explained in more detail with reference to a preferred embodiment and the drawings.

[0017] It shows the only figure Fig.Figure 1 is a schematic representation of an arrangement for a thermal management system of a motor vehicle. The arrangement 1 comprises a first vehicle component F1, which, shown here in a schematic sectional view, is designed as an electric drive motor 2 for propelling the motor vehicle. For this purpose, the electric drive motor 2 is supplied with energy by a traction battery of the motor vehicle (not shown here). The electric drive motor 2 has a stator 3 with a stator body 4 and stator windings 5, as well as a rotor 6 rotatable with respect to the stator 3, the rotor body 7 of which is non-rotatably connected to a rotor shaft 8 of the rotor 6. The rotor body 7 carries a magnetic field-exciting component (not shown here), for example, rotor windings or permanent magnets. Furthermore, the electric drive motor 2 has a housing 9 surrounding the stator 3 with at least one cooling channel 10 for cooling the stator 3 and the rotor 6.The cooling channel 10 is designed to actively cool the first vehicle component F1 and is permeated by a cooling fluid 11. For this purpose, it is connected to a cooling circuit of the thermal management system that carries cooling fluid (not shown here). The housing 9 with the cooling channel 10 thus forms a cooling unit 12 for the first vehicle component F1.

[0018] The second vehicle component F2 is an on-board charger 13, designed to convert alternating current supplied by an external charging station into direct current for charging the traction battery. The second vehicle component F2 does not have its own cooling unit connected to the cooling circuit for actively cooling itself. The two vehicle components F1 and F2 have different operating times that do not overlap. Therefore, they also have different cooling requirement periods. During the cooling requirement periods of the first vehicle component F1, the associated cooling unit 12 is supplied with cooling fluid 11. To also cool the second vehicle component F2, it is thermally, but not fluidically, coupled to the cooling unit 12 of the first vehicle component F1.For this purpose, the first vehicle component F1 is connected to the cooling unit 12 of the first vehicle component via a loop heat pipe LHP.

[0019] The loop heatpipe LHP comprises a pipeline 14 with a supply section 14a, a so-called steam line, and a return section 14b, a so-called liquid line. Between the supply section 14a and the return section 14b, a condensing unit 15, thermally coupled to the first vehicle component F1, and an evaporating unit 16, thermally coupled to the second vehicle component F2, are arranged. The condensing unit 15 is located on the housing 9 of the drive motor 2 and is thus thermally coupled to the cooling unit 12. The evaporating unit 16 is integrated into a housing 17 of the on-board charger 13. For this purpose, the housing 17 has corresponding connections 18 through which the pipeline 14, located outside the housing 17, can be coupled to the evaporating unit 16 inside the housing 17.The Loop Heatpipe (LHP) is a passive heat exchanger in which heat transfer occurs through phase changes. Hydrodynamic transport is ensured by the resulting pressure differences and capillary forces.

[0020] During operation, the electronics of the on-board charger 13 release waste heat 19 due to power losses. This heat is absorbed by the working medium via the evaporation unit 16 during a phase change of the working medium located in the pipe 14. The working medium, which is gaseous due to the phase change, transports the waste heat 19 in the gas line 14a to the condensation unit 15. From there, the waste heat 19 is transferred to the cooling unit 12 via another phase change of the working medium. The cooling unit 12 is also supplied with cooling fluid 11 during the cooling requirements of the second vehicle component F2 and carries away the waste heat 19 transported by the loop heat pipe LHP and transferred to the first vehicle component F1.The working medium, which due to the phase change is again present as a liquid, flows back in the liquid line 14b to the evaporation device 16, where it can absorb waste heat 19 again by evaporating.

Claims

[1] Thermal management system for a motor vehicle, comprising: - a first vehicle component (F1) with a cooling unit (12), - a second vehicle component (F2) arranged at a distance from the first vehicle component (F1), wherein the first vehicle component (F1) and the second vehicle component (F2) have different cooling requirement periods, - a cooling circuit carrying a cooling fluid, to which the cooling unit (12) of the first vehicle component (F1) is connected, wherein the cooling unit (12) is capable of being actively cooled by a cooling fluid (11) of the cooling circuit during initial cooling requirement periods of the first vehicle component (F1), and - a loop heat pipe (LHP) thermally coupled to the two vehicle components (F1, F2), which is designed for passive cooling of the second vehicle component (F2) to transfer waste heat (19) of the second vehicle component (F2) to the cooling unit (12) of the first vehicle component (F1), wherein the cooling unit (12) is permeable to the cooling fluid (11) of the cooling circuit for the removal of the waste heat (19) of the second vehicle component (F2) during the second cooling requirement periods of the second vehicle component (F2). [2] Thermal management system according to claim 1, characterized by, that the loop heat pipe (LHP) comprises a ring-shaped closed pipe (14) filled with a working medium, an evaporation device (16) thermally coupled to the second vehicle component (F2), and a condensation device (15) thermally coupled to the cooling unit (12) of the first vehicle component (F1), wherein the pipe (14) has a forward section (14a) from the evaporation device (16) to the condensation device (15), in which the working medium can be converted from a liquid phase to a gas phase by absorbing the waste heat (19) of the second vehicle component (F2), and a return section (14b) from the condensation device (15) to the evaporation device (16), in which the working medium can be converted from the gas phase back to the liquid phase by releasing the waste heat (19) to the cooling unit (12),wherein the working medium is transported passively by capillary action and a pressure gradient within the pipeline (14). [3] Thermal management system according to claim 2, characterized by , that the evaporation device (16) has a highly thermally conductive plate which is arranged on or in a housing (17) of the second vehicle component (F2). [4] Thermal management system according to claim 2 or 3, characterized by , that the condensing device (15) is arranged on or in a housing (9) of the first vehicle component (F1), wherein the housing (9) has at least one cooling channel (10) through which the cooling fluid (11) flows and which is connected to the cooling circuit, and thereby forms the cooling unit (12). [5] Thermal management system according to any one of the preceding claims, characterized by, that the cooling circuit has a pump for circulating the cooling fluid (11) in the cooling circuit and thus in the cooling unit (12) and the thermal management system has a control device designed to activate the pump during the cooling requirement periods of the first vehicle component (F1) and the second vehicle component (F2) to provide a flow through the cooling unit (12) of the first vehicle component (F1). [6] Thermal management system according to any one of the preceding claims, characterized by , that the first vehicle component (F1) is an electric drive motor (2) of the vehicle which can be supplied from a traction battery of the motor vehicle and the second vehicle component (F2) is an on-board charger (13) for rectifying an alternating current for charging the traction battery. [7] Thermal management system according to claim 6, characterized by, that the electric drive motor (2) has the first cooling requirement periods during discharge processes of the traction battery to supply the electric drive motor (2) and the on-board charger (13) has the second cooling requirement periods during charging processes of the traction battery by means of an external charging station. [8] Motor vehicle with a thermal management system according to any of the preceding claims.

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