Cooling system for a component of an electric vehicle

Abstract

Cooling system (10, 200, 300) for a component (22) of an electric vehicle, wherein the cooling system (10, 200, 300) comprises: a housing (20) configured to enclose a component (22) of an electric vehicle immersed in a cooling fluid and to define an initial volume, an element with variable volume (34, 218) that defines a second volume which changes in response to a first signal, wherein the first volume and the second volume define a combined volume, wherein the heat from the operation of component (22) of the electric vehicle causes the cooling fluid in the combined volume to transition between a liquid state and a vapor state; a pressure sensor (44) configured to sample pressure in the combined volume during operation; a condenser (30) which is arranged in the housing (20) and is configured to cause the cooling fluid to transition from the vapor state back to the liquid state; and a controller (60, 220, 310) which includes a volume adjustment module (64) configured to generate the first signal to change the second volume of the variable volume element (34, 218) to adjust the combined volume in response to the pressure and a first temperature of the component (22) of an electric vehicle.

Description

INTRODUCTION

[0001] The present invention relates to components of electric vehicles and in particular to a cooling system for a component of an electric vehicle.

[0002] For general background information, reference is made in advance to the publications US 2018 / 0 006 346 A1, US 2010 / 0 009 244 A1, EP 3 018 728 A1 and EP 2 290 729 A1.

[0003] Electric vehicles (EVs) contain a battery system with one or more battery cells, modules, and / or assemblies. The EV can be a battery electric vehicle (BEV), a fuel cell vehicle, or a hybrid vehicle. A power control system is used to manage the charging and / or discharging of the battery system during charging, regeneration, and / or driving. While driving, one or more electric motors of the EV receive power from the battery system to provide propulsion for the vehicle and / or to feed power back into the battery system during regeneration and / or charging from a utility company.

[0004] During operation, power is supplied to the motor(s) via the battery system and returned to the battery system by one or more EV components, such as power inverters, DC-DC converters, and / or other EV components. The battery system is designed to supply high power when required, to quickly absorb high power during charging from the utility company, and / or to absorb high power during regeneration. The power density of battery systems is expected to continue increasing, and they are expected to operate at higher voltage levels. Operating under these conditions can result in significant heating of the battery cells, battery modules, battery assembly, power inverters, DC-DC converters, and / or other EV components.

[0005] The invention is therefore based on the objective of providing a cooling system for a component of an electric vehicle with which the described heating problem can be reliably controlled. SUMMARY

[0006] This problem is solved with a cooling system characterized by the features of claim 1.

[0007] A cooling system for an electric vehicle component includes a housing configured to enclose a component immersed in a cooling fluid and to define a first volume. A variable-volume element defines a second volume that changes in response to a first signal. The first and second volumes together define a combined volume. Heat generated by the operation of the electric vehicle component causes the cooling fluid in the combined volume to transition between a liquid and a vapor state. A pressure sensor is configured to monitor the pressure in the combined volume during operation. A condenser is located within the housing and is configured to cause the cooling fluid to transition back from the vapor state to the liquid state.A controller contains a volume adjustment module that is configured to generate the first signal to vary the second volume of the variable volume element in order to adjust the combined volume in response to the pressure and a first temperature of the component of an electric vehicle.

[0008] According to other features, a temperature sensor is configured to measure the initial temperature of an electric vehicle component. The variable-volume element includes a bellows that is movable between two positions. The first position corresponds to the lowest value of the second volume, while the second position corresponds to the highest value of the second volume. An actuator, connected to the controller, causes the bellows to move between the first and second positions.

[0009] According to other features, the controller also includes a first operating lookup table. The controller indexes the first operating lookup table using pressure to identify a saturation temperature. The controller generates a pressure differential between the saturation temperature and the first temperature. The controller determines whether the pressure differential is within a predefined temperature range. In response to the determination that the pressure differential is not within the predefined temperature range, the controller sets the first signal to change the pressure in the combined volume.

[0010] According to other features, a pressure wave generator is connected to the controller and is configured to selectively generate pressure waves in the cooling fluid to reduce bubbles that accumulate on the component of an electric vehicle. The variable volume element comprises a bellows having an open end connected to the first volume of fluid and a closed end, a rod having a first end connected to the bellows, and an actuator connected to a second end of the rod.

[0011] A system comprises the cooling system and the component of an electric vehicle. The electric vehicle component is selected from a group that includes a battery cell, a battery module, a battery assembly, a power inverter, and a DC-DC converter.

[0012] A cooling system for an electric vehicle component includes a housing configured to enclose the component, which is immersed in a cooling fluid. The heat generated by the component's operation causes the cooling fluid to transition between a liquid and a vapor state. A condenser is located within the housing and configured to cause the cooling fluid to return from the vapor state to a liquid state. A pressure wave generator is configured to selectively generate pressure waves within the cooling fluid. A controller is configured to adjust the operation of the pressure wave generator in response to an initial temperature of the electric vehicle component.

[0013] According to other features, a temperature sensor is configured to detect the initial temperature of an electric vehicle component. The controller adjusts the operation of the pressure wave generator in response to a difference between this initial temperature and a preset temperature.

[0014] A system comprises the cooling system and the component of an electric vehicle. The component of an electric vehicle is selected from a group that includes a battery cell, a battery module, a battery assembly, a power inverter, and a DC-DC converter.

[0015] A cooling system for an electric vehicle component comprises a housing that encloses the component immersed in a cooling fluid and defines a first volume. Heat generated by the component's operation causes the cooling fluid to transition between a liquid and a vapor state. A condenser is located within the housing and configured to cause the cooling fluid to return to a liquid state from the vapor state. A variable-volume element defines a second volume that is in fluid communication with the first volume. This second volume varies in response to pressure changes within the housing.

[0016] In other features, the variable volume element includes a bellows containing an open end that is in fluid communication with the first volume and a closed end.

[0017] A system comprises the cooling system and the component of an electric vehicle. The component of an electric vehicle is selected from a group that includes a battery cell, a battery module, a battery assembly, a power inverter, and a DC-DC converter.

[0018] Further applications of the present invention will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of protection of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be more fully understood from the detailed description and the accompanying drawings; these show: Fig. 1 a functional block diagram of an example of a cooling system comprising an active variable volume element for a component of an electric vehicle (EV) according to the present invention; Fig. 2 a diagram illustrating an example of the phase changes for the cooling fluid as a function of the saturation temperature and pressure; Fig. 3 a diagram illustrating an example of heat flux density as a function of a difference between a temperature of the EV component and a saturation temperature; Fig. 4 a flow chart of an example of a method for controlling an actuator to change a volume with a housing surrounding an EV component immersed in a cooling fluid, according to the present invention; Fig. 5-6 functional block diagrams of an example of a passive cooling system for an EV component, which includes a passive element with variable volume, according to the present invention; Fig. 7 a functional block diagram of an example of a further active cooling system for the EV component according to the present invention; and Fig. 8 a flow chart of an example of a method for controlling one or more pressure wave generators to eliminate bubbles forming on the EV component in order to adjust the temperature of the EV component according to the present invention.

[0020] Reference symbols can be used multiple times in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0021] As described above, the power density and operating voltage of battery systems for EVs have increased significantly. This can lead to heating of EV components, such as the battery cells, battery module(s), battery assembly(s), power inverter(s), DC-DC converter(s), and / or other EV components. Cooling systems are used to maintain the EV components within a temperature range to ensure optimal performance and / or prevent premature damage / wear due to excessive operating temperatures.

[0022] Single-phase cooling systems have been used to cool EV components. The cooling fluid can be supplied by a cooling fluid source and a pump through a cooling circuit that includes a housing for the EV component. The cooling fluid exchanges heat with the surfaces of the EV component. Cooling is performed without a phase change of the cooling fluid. After the cooling fluid has been heated by the EV component, it is cooled using a cooler and / or fan and then returned to the cooling fluid source. While single-phase cooling systems can operate in some applications, higher power density applications require greater cooling capacity. The cooling systems and methods according to the present invention relate to two-phase cooling, which involves a phase change of the cooling fluid from a liquid state to a vapor state.Two-phase cooling systems provide approximately ten times the cooling capacity of single-phase cooling systems.

[0023] In Fig. 1 contains an active cooling system 10 and a housing 20 for a component 22 of an electric vehicle (EV). During use, the EV component 22 is immersed in a cooling fluid 24. The heat from the EV component is absorbed by the cooling fluid, causing the cooling fluid 24 to change from a liquid state to a vapor state. The vapor is cooled back to a liquid state by a condenser 30, and the process repeats.

[0024] As further described below, the active cooling system 10 varies the volume of a variable-volume element 34 to establish a combined volume of the housing 20 and the variable-volume element 34. In other words, the housing 20 defines a first volume, while the variable-volume element 34 defines a second volume that is in fluid communication with the first volume. The first and second volumes together define the combined volume. In some examples, the second volume has a maximum volume in the range of 5% to 25% of the first volume, although larger or smaller volume values ​​can be used.

[0025] In some examples, the variable-volume element 34 includes a bellows with flexible sides to allow the variable-volume element 34 to contract and expand, thus changing the second volume of the variable-volume element 34. An actuator 38 moves the bellows between a first and a second position (and / or one or more positions in between). In some examples, the actuator 38 includes a motor, a threaded element, and a threaded rod 42, although other types of actuators may be used. The motor rotates the threaded element to change the linear position of the threaded rod 42. In other examples, a housing is divided into several sub-chambers, and valves are used to selectively connect (or block) successive sub-chambers to increase (or decrease) the second volume.

[0026] A controller 60 is connected to a pressure sensor 44 to sense the pressure inside the housing 20. The controller 60 is also connected to a temperature sensor 46, which senses the temperature of the EV component 22. In some examples, the EV component 22 comprises a power inverter containing one or more integrated circuits (ICs) mounted on a copper plate, which is mounted on insulating legs made of ceramic or another insulating material, with the temperature sensor 46 sensing the surface temperature of the copper plate.

[0027] In some examples, the controller 60 also generates control signals to control the components of the EV component 22, such as circuit breakers, although this function can also be performed by another vehicle controller. The controller 60 includes a volume setting module 64, which is configured to determine a setpoint volume for the variable volume element 34 and adjust the second volume accordingly. The controller 60 also includes a first operating lookup table (LUT) 66, which defines the phases of the cooling fluid with respect to pressure P and saturation temperature T. sat defined.

[0028] In Fig. 2 are the phase changes of the cooling fluid as a function of the saturation temperature T. sat and the pressure P is shown. Because the pressure P inside the housing is known, the phase change relation can be used to determine the saturation temperature T. satto identify for a given pressure P during the transition between a liquid state and a vapor state.

[0029] In Fig. 3 is the heat flux density (q'') as a function of a difference between a temperature (T) of the EV component and a saturation temperature (T). sat ). In some examples, a Novec™ cooling fluid is used, although other types of cooling fluid can be used. The cooling system operates in different phase ranges depending on the temperature difference ΔT. The different phase ranges include a single-phase convection range 110, a nucleate boiling range 114 with isolated bubbles, a range 118 with jets and columns, a transition boiling range 122, and a film boiling range 124.

[0030] Optimal cooling performance occurs in the range corresponding to range 118 of the nucleus boiling process using jet and columns. As described below, the controller 60 adjusts the combined volume (and indirectly the pressure) in the housing using the variable volume element 34. The controller attempts to maintain the temperature difference (ΔT) within a predetermined temperature range corresponding to range 118 of the nucleus boiling process using jet and columns. In other words, the controller 60 compares the temperature difference with the predetermined temperature range and adjusts the second volume accordingly.

[0031] In particular, the combined volume is reduced if the temperature difference (ΔT) is greater than the specified temperature range in order to reduce the pressure P (and ultimately T). satto increase the combined volume. The combined volume is increased when the temperature difference (ΔT) is smaller than the specified temperature range, in order to increase the pressure P (and ultimately T). sat to reduce).

[0032] In Fig. Figure 4 shows a method 150 for controlling the variable volume element to change the pressure within a housing for the EV component. Figure 160 shows the pressure P in the housing 20 and the temperature T of the EV component 22 being measured. Figure 164 shows the first operational LUT being indexed using P to determine T sat to determine a gas-liquid transition point. At 166, a difference ΔT between T and T is determined. sat determined. At 168, the temperature difference ΔT is compared with a predetermined temperature range, which corresponds to range 118 of nucleate boiling with jets and columns.

[0033] If the temperature difference is within the specified temperature range, the procedure returns to 110. If the temperature difference is not within the specified temperature range, as determined at 170, the pressure is adjusted at 172 by changing the volume of the combined chambers using the variable volume element 34, after which the control returns to 110.

[0034] In the Fig. Figures 5-6 show a passive cooling system 200 for the EV component 22. The housing 20 is attached to a variable volume element 218. In this example, the controller 220 controls the operation of the EV component, but it is not involved in the control of the variable volume element 218. The housing 20 and the variable volume element 218 provide a combined volume that changes adaptively depending on the vapor pressure or the load.

[0035] Under conditions of high load with high vapor pressure, the variable volume element 218 adapts (e.g., expands), with the combined volume having a maximum volume, as in Fig. Figure 5 shows that under low load conditions with lower vapor pressure, the variable volume element 218 adapts (e.g., contracts), with the combined volume having a minimum volume, as shown in Figure 5. Fig. Figure 6 shows that in some examples, a pressure relief valve 214 is arranged in fluid communication with the housing 20. The pressure relief valve 214 opens to release the pressure when the pressure in the housing is greater than a predetermined pressure threshold.

[0036] In Fig. Figure 7 shows an active cooling system 300 for the EV component. The active cooling system 300 includes a controller 310 and one or more pressure wave generators (WG) 322, which selectively generate pressure waves in the cooling fluid with one or more amplitudes, one or more frequencies and / or one or more patterns (in phase or out of phase).

[0037] During heating of the cooling fluid, bubbles form within it, which can adhere to the surfaces of the EV component. More efficient cooling occurs when pressure waves are generated, preventing bubbles from adhering to the EV component surfaces and facilitating the formation of new bubbles. Removing bubbles also contributes to lowering the EV component's temperature. Less efficient cooling occurs when the pressure waves are smaller or not used, resulting in bubbles remaining on the EV component's surface and fewer bubbles being generated. An increase in bubbles on the EV component also contributes to raising its temperature. The one or more pressure wave generators 322 generate pressure waves with one or more amplitudes that propagate through the cooling fluid, removing the bubbles that form on the EV component's surfaces.It can be a modulation of the bubbles on and off, or with different amplitudes and / or frequencies, to achieve T. sat to vary.

[0038] A controller 310 contains a pressure wave control module 312, which is configured to selectively adjust the pressure waves in response to the temperature of the EV component. In other words, if the temperature of the EV component is greater than a predefined threshold, the controller 310 causes one or more pressure wave generators 322 to generate pressure waves and / or increase the amplitude or frequency of the pressure waves.

[0039] As can be seen, one or more pressure wave generators 322 can be switched on and off in response to the difference between the temperature of the EV component and the specified temperature threshold and / or modulated between two or more wave amplitudes. In some examples, two or more pressure wave generators are used. In some examples, the two or more pressure wave generators are operated in phase. In other examples, the two or more pressure wave generators are operated out of phase.

[0040] In Fig. Figure 8 shows a method 400 for controlling one or more pressure wave generators 322. Figure 410 measures the temperature T of the EV component. Figure 414 adjusts the operation of one or more wave generators based on the difference between the temperature T and a predetermined temperature threshold.

Claims

[1] Cooling system (10, 200, 300) for a component (22) of an electric vehicle, wherein the cooling system (10, 200, 300) comprises: a housing (20) configured to enclose a component (22) of an electric vehicle immersed in a cooling fluid and to define an initial volume, an element with variable volume (34, 218) that defines a second volume which changes in response to a first signal, wherein the first volume and the second volume define a combined volume, wherein the heat from the operation of component (22) of the electric vehicle causes the cooling fluid in the combined volume to transition between a liquid state and a vapor state; a pressure sensor (44) configured to sample pressure in the combined volume during operation; a condenser (30) which is arranged in the housing (20) and is configured to cause the cooling fluid to transition from the vapor state back to the liquid state; and a controller (60, 220, 310) which includes a volume adjustment module (64) configured to generate the first signal to change the second volume of the variable volume element (34, 218) to adjust the combined volume in response to the pressure and a first temperature of the component (22) of an electric vehicle. [2] Cooling system (10, 200, 300) according to claim 1, further comprising a temperature sensor (46) configured to sample the first temperature of the component (22) of an electric vehicle. [3] Cooling system (10, 200, 300) according to claim 1, wherein the variable volume element (34, 218) comprises: a bellows that is movable between a first position and a second position, where the first position corresponds to the lowest value of the second volume and the second position corresponds to the highest value of the second volume; and an actuator (38) which is connected to the controller (60, 220, 310) to cause the bellows to move between the first position and the second position. [4] Cooling system (10, 200, 300) according to claim 1, wherein: the controller (60, 220, 310) also includes a first operating lookup table, and The controller (60, 220, 310) indexes the first operating lookup table using pressure to identify a saturation temperature. [5] Cooling system (10, 200, 300) according to claim 4, wherein the controller (60, 220, 310) generates a pressure difference between the saturation temperature and the first temperature. [6] Cooling system (10, 200, 300) according to claim 5, wherein the controller (60, 220, 310) determines whether the pressure difference is within a predetermined temperature range. [7] Cooling system (10, 200, 300) according to claim 6, wherein the controller (60, 220, 310) sets the first signal in response to the determination that the pressure difference is not within the specified temperature range, in order to change the pressure in the combined volume. [8] Cooling system (10, 200, 300) according to claim 1, further comprising a pressure wave generator which is connected to the controller (60, 220, 310) and is configured to selectively generate pressure waves in the cooling fluid to reduce the bubbles that accumulate on the component (22) of the electric vehicle. [9] Cooling system (10, 200, 300) according to claim 1, wherein the variable volume element (34, 218) comprises: a bellows comprising an open end in fluid connection with the first volume and a closed end; a rod (42) containing a first end connected to the bellows; and an actuator (38) which is connected to a second end of the rod (42). [10] System that includes: the cooling system (10, 200, 300) according to claim 1; and the component (22) of the electric vehicle.

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