Battery cooling device, battery cooling system

Abstract

A battery cooling device (200) is applied to an electric flight vehicle (100). The battery cooling device comprises: a cooling tank (210); a plurality of battery cells (220) which are housed in the cooling tank; an insulating liquid (230) which is housed in the cooling tank in a flowable manner, and in which the plurality of battery cells are immersed so that the insulating liquid absorbs heat of the plurality of battery cells; and valve joints (240, 250, 272) which are provided on the cooling tank, and to / from which a low-temperature cooling device (400), where the insulating liquid within the cooling tank can be flowed in and out, is attached and detached. Consequently, the temperature of a battery cell at a high temperature is decreased further than the temperature of the other battery cells, and the temperatures of the plurality of battery cells can be equalized.

Description

Cross-reference to Related Applications

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[0001] This application is based on Japanese Patent Application No. 2023-98350 filed on June 15, 2023, the contents of which are incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to a battery cooling device and a battery cooling system.

Background Art

[0003] Conventionally, a battery thermal management system applied to an electric aircraft has been proposed in, for example, Patent Document 1. The battery thermal management system includes a battery pack in which a plurality of battery cells, a plurality of cooling plates, and a plurality of insulators are combined.

[0004] [[ID=,22]]Each battery cell is arranged along the outer wall surface of the cooling plate. Also, each battery cell, each cooling plate, and each insulator are arranged in the order of battery cell, cooling plate, battery cell, insulator, battery cell.

[0005] And a working fluid circulates inside the cooling plate. Thereby, each battery cell is cooled by each cooling plate. That is, the heat of each battery cell is stored in the working fluid via the cooling plate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] However, in the conventional technology described above, there is an interface between the battery cell and the cooling plate, and an interface between the inner wall of the cooling plate and the working fluid, which makes it difficult for heat to transfer from the battery cell to the working fluid. As a result, the cooling (heat storage) performance for each battery cell and the uniform temperature distribution performance of each battery cell are reduced in the battery pack.

[0008] In particular, when battery packs are applied to electric aircraft, the large currents flowing through each battery cell during takeoff and landing cause the temperature of each battery cell to rise rapidly in a short time. Since the battery cells described in Patent Document 1 are arranged in a large number in two dimensions, temperature distributions tend to occur among the battery cells depending on their location. As a result, high-temperature battery cells degrade more rapidly than other battery cells.

[0009] Therefore, it is desirable to lower the temperature of high-temperature battery cells to the same level as the other battery cells. Furthermore, it is desirable to equalize the temperature of each battery cell to minimize differences in output and degradation. Additionally, it is desirable to rapidly cool each battery cell on the ground after landing.

[0010] In view of the above, this disclosure aims to provide a battery cooling device and battery cooling system applicable to electric aircraft that can lower the temperature of a high-temperature battery cell to a lower temperature than other battery cells while simultaneously achieving uniform temperature distribution among multiple battery cells.

[0011] To achieve the above objective, according to a first aspect of this disclosure, a battery cooling device applicable to an electric aircraft, Cooling tank and Multiple battery cells housed in a cooling tank, An insulating liquid is contained in a cooling tank in a fluid manner, immersing multiple battery cells and absorbing heat from the multiple battery cells, A valve fitting is provided in the cooling tank, and a low-temperature cooling device capable of inflowing and outflowing the insulating liquid inside the cooling tank is attached to and detached from the valve fitting, Includes, The valve fitting allows insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. Multiple battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, making contact with the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is, The insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cell. This is based on the premise of the flow of insulating liquid circulating between the low-temperature cooling device and the device. Passageway section (291) and A support portion (292) that maintains the spacing between adjacent battery cells by contacting the opposing surfaces of the battery cells, Includes, Spacer components include offset fins, corrugated fins, wave fins, louver fins, extruded tubes, and inner fin tubes. , or a member having a passage portion and a support portion, wherein the spacer member may be formed from a metal material or a resin material. .

[0012] According to a second aspect of this disclosure, a battery cooling system applied to an electric aircraft, Cooling tank and Multiple battery cells housed in a cooling tank, An insulating liquid is contained in a cooling tank in a fluid manner, immersing multiple battery cells and absorbing heat from the multiple battery cells, A valve fitting is provided in the cooling tank, and a low-temperature cooling device capable of inflowing and outflowing the insulating liquid inside the cooling tank is attached to and detached from the valve fitting, Includes, The valve fitting allows insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. Multiple battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, making contact with the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is, The insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cell. This is based on the premise of the flow of insulating liquid circulating between the low-temperature cooling device and the device. Passageway section (291) and A support portion (292) that maintains the spacing between adjacent battery cells by contacting the opposing surfaces of the battery cells, including The spacer member is an offset fin, a corrugated fin, a wavy fin, a louver fin, an extruded tube, an inner fin tube , or a member having a passage portion and a support portion, wherein the spacer member may be formed from a metal material or a resin material. , a battery cooling device, and a cryogenic cooling device for cooling and storing an insulating liquid, and a control device for controlling the cryogenic cooling device, and including By connecting the battery cooling device and the cryogenic cooling device via a valve joint, a cooling circulation circuit in which the insulating liquid can circulate between the battery cooling device and the cryogenic cooling device is configured. The control device circulates the insulating liquid pre-cooled by the cryogenic cooling device through the cooling circulation circuit.

[0013] According to a third aspect of the present disclosure, a battery cooling system applied to an electric aircraft, comprising: a cooling tank, and a plurality of battery cells housed in the cooling tank, and an insulating liquid that is fluidly housed in the cooling tank, immerses the plurality of battery cells, and absorbs the heat of the plurality of battery cells, and a valve joint provided in the cooling tank and to which a cryogenic cooling device capable of flowing in and out the insulating liquid inside the cooling tank is detachably attached, and including The valve fitting allows insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. The plurality of battery cells are arranged with a gap (221) between adjacent ones, and each has an opposing surface (227) facing an adjacent battery cell. including a spacer member (290) that is sandwiched between adjacent battery cells to contact the opposing surfaces of the adjacent battery cells and transfer the heat of the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member has a passage portion (291) through which the insulating liquid can flow in one direction among the directions parallel to the opposing surfaces of the battery cells, and This is based on the premise of the flow of insulating liquid circulating between the low-temperature cooling device and the device. a support portion (292) that contacts the opposing surfaces of the battery cells to maintain the gap between adjacent battery cells, and including and Spacer components include offset fins, corrugated fins, wave fins, louver fins, extruded tubes, and inner fin tubes. , or a member having a passage portion and a support portion, wherein the spacer member may be formed from a metal material or a resin material. , battery cooling device and A cryogenic cooling device for cooling and storing insulating liquid, A control device for controlling the low-temperature cooling device, Includes, The battery cooling device and the low-temperature cooling device are connected via a valve joint, thereby forming a cooling circulation circuit in which insulating liquid can circulate between the battery cooling device and the low-temperature cooling device. The control device discharges the insulating liquid from inside the cooling tank via a cooling circulation circuit, and then fills the battery cooling device with insulating liquid that has been pre-cooled by a low-temperature cooling device.

[0014] According to this method, the heat from each battery cell is absorbed by the insulating liquid, so the temperature of high-temperature battery cells can be lowered compared to the temperatures of other battery cells, while suppressing the temperature rise of each battery cell.

[0015] Furthermore, when multiple battery cells are immersed in the insulating liquid inside the cooling tank, the insulating liquid flows (convection). Therefore, temperature variations among the battery cells can be suppressed and the temperature can be made uniform.

[0016] Furthermore, after the electric aircraft lands, a cryogenic cooling system is connected to the valve joint, allowing for forced cooling of the insulating liquid and each battery cell. This enables a rapid decrease in the temperature of each battery cell and insulating liquid inside the cooling tank. [Brief explanation of the drawing]

[0017] The above and other purposes, features and benefits of this disclosure will become clearer from the following detailed description with reference to the attached drawings. In the attached drawings, [Figure 1] Figure 1 is a diagram showing the schematic configuration of the eVTOL according to the first embodiment. [Figure 2] Figure 2 shows the battery cooling system. [Figure 3]Figure 3 shows the battery cooling system and cryogenic cooling system after takeoff. [Figure 4] Figure 4 shows the changes in battery output and battery temperature from takeoff to landing of an eVTOL. [Figure 5] Figure 5 is a cross-sectional view showing a battery cooling device according to the second embodiment. [Figure 6] Figure 6 is a cross-sectional view showing a modified example. [Figure 7] Figure 7 is a cross-sectional view showing a modified example. [Figure 8] Figure 8 is a cross-sectional view showing a modified example. [Figure 9] Figure 9 is a cross-sectional view showing a battery cooling device according to the third embodiment. [Figure 10] Figure 10 is a cross-sectional view showing a modified example. [Figure 11] Figure 11 is a cross-sectional view showing a modified example. [Figure 12] Figure 12 is a cross-sectional view showing a battery cooling device according to the fourth embodiment. [Figure 13] Figure 13 is a cross-sectional view showing a modified example. [Figure 14] Figure 14 is a cross-sectional view showing a modified example. [Figure 15] Figure 15 is a cross-sectional view showing a modified example. [Figure 16] Figure 16 is a top view of the battery cooling device according to the fifth embodiment. [Figure 17] Figure 17 is a cross-sectional view of the line XVII-XVII in Figure 16. [Figure 18] Figure 18 is a perspective view of an offset fin, which is an example of a spacer member. [Figure 19] Figure 19 is a perspective view of a corrugated fin, which is an example of a spacer member. [Figure 20] Figure 20 is a perspective view of a wave fin, which is an example of a spacer member. [Figure 21] Figure 21 is a perspective view of a louver fin, which is an example of a spacer member. [Figure 22]Figure 22 is a top view of a battery cell including an extruded tube, which is an example of a spacer member. [Figure 23] Figure 23 is a top view of a battery cell including an inner fin tube, which is an example of a spacer member. [Figure 24] Figure 24 is a cross-sectional view showing a battery cooling device according to the sixth embodiment. [Figure 25] Figure 25 is a top view showing a modified example. [Figure 26] Figure 26 is a cross-sectional view of Figure 25 from XXVI-XXVI. [Figure 27] Figure 27 is a cross-sectional view of Figure 25 from XXVII-XXVII. [Figure 28] Figure 28 is a cross-sectional view showing a battery cooling device according to the seventh embodiment. [Figure 29] Figure 29 shows the battery cooling system during ground (charging) operation. [Figure 30] Figure 30 is a cross-sectional view showing a battery cooling device applied to a different cooling method. [Figure 31] Figure 31 is a diagram showing a battery cooling system including the battery cooling device shown in Figure 30. [Figure 32] Figure 32 is a cross-sectional view showing a battery cooling device applied to a different cooling method. [Figure 33] Figure 33 is a diagram showing a battery cooling system including the battery cooling device shown in Figure 32. [Figure 34] Figure 34 is a cross-sectional view showing a battery cooling device according to the eighth embodiment. [Figure 35] Figure 35 is a cross-sectional view showing a battery cooling device according to the eighth embodiment. [Figure 36] Figure 36 is a cross-sectional view showing a battery cooling device according to the eighth embodiment. [Modes for carrying out the invention]

[0018] The following describes several embodiments for implementing this disclosure with reference to the drawings. In each embodiment, parts corresponding to matters described in a preceding embodiment may be denoted by the same reference numerals, and redundant explanations may be omitted. If only a part of the configuration is described in each embodiment, other embodiments described in a preceding embodiment may be applied to the remaining parts of the configuration.

[0019] It is possible to combine parts that are explicitly shown as being combinable in each embodiment. Furthermore, as long as there are no particular problems with the combination, it is also possible to partially combine embodiments with each other, embodiments with modifications, and modifications with each other, even if it is not explicitly shown that they are combinable.

[0020] (First Embodiment) The battery cooling device according to this embodiment is mounted on an electric aircraft. The electric aircraft is capable of flight by the drive of a rotating electric machine.

[0021] Electric aircraft include, for example, electric vertical take-off and landing aircraft (eVTOLs), electric short take-off and landing aircraft (eSTOLs), and drones. eVTOL is an abbreviation for electronic Vertical Take-Off and Landing aircraft. eSTOL is an abbreviation for electronic Short distance Take-Off and Landing aircraft. The following describes an example in which a battery cooling system is installed on an eVTOL.

[0022] <evtol> As shown in Figure 1, the eVTOL 100 of this embodiment, as an example, includes an airframe 110, fixed wings 120, rotor blades 130, a lift adjustment mechanism 140, a battery cooling device 200, an EPU 150, a BMS 160, and an ECU 170.

[0023] The aircraft body 110 is the fuselage section of the aircraft. The aircraft body 110 has a shape that extends from front to back. The aircraft body 110 has a crew compartment for the crew and / or a cargo compartment for carrying luggage.

[0024] The fixed wing 120 is the wing section of the aircraft and is connected to the main body 110. The fixed wing 120 provides gliding lift. Gliding lift is the lift generated by the fixed wing 120. As an example, the fixed wing 120 has a main wing 121 and a tail wing 122. The main wing 121 extends from near the center in the longitudinal direction of the main body 110 to the left and right. The tail wing 122 extends from the rear of the main body 110 to the left and right. The shape of the fixed wing 120 is not particularly limited. For example, a swept wing, delta wing, straight wing, etc., can be used.

[0025] Multiple rotors 130 are provided on the aircraft. At least some of the multiple rotors 130 may be provided on the fixed wings 120. At least some of the multiple rotors 130 may be provided on the aircraft body 110. The number of rotors 130 provided on the eVTOL 100 is not particularly limited. As an example, multiple rotors 130 are provided on both the aircraft body 110 and the main wings 121. The eVTOL 100 has six rotors 130.

[0026] The rotor blade 130 is sometimes referred to as a rotor, propeller, or fan. The rotor blade 130 has blades 131 and a shaft 132. The blades 131 are attached to the shaft 132. The blades 131 are vanes that rotate together with the shaft 132. Multiple blades 131 extend radially around the axis of the shaft 132. The shaft 132 is the axis of rotation of the rotor blade 130 and is rotationally driven by the motor of the EPU 150.

[0027] The rotor 130 generates thrust through rotation. This thrust acts on the eVTOL 100 primarily as rotational lift during takeoff and landing. The rotor 130 primarily provides rotational lift during takeoff and landing. Rotational lift is the lift generated by the rotation of the rotor 130. During takeoff and landing, the rotor 130 may provide only rotational lift, or it may provide forward thrust along with rotational lift. The rotor 130 provides rotational lift when the eVTOL 100 is hovering.

[0028] The propulsion force acts on the eVTOL 100 primarily as thrust during cruising. The rotor blades 130 primarily provide thrust during cruising. During cruising, the rotor blades 130 may provide only thrust, or they may provide both thrust and lift.

[0029] The lift adjustment mechanism 140 adjusts the glide lift of the fixed wing 120. The lift adjustment mechanism 140 increases or decreases the glide lift generated by the fixed wing 120. The lift adjustment mechanism 140 adjusts the glide lift by adjusting, for example, the surface area of ​​the fixed wing 120, angle of attack (AOA), camber (wing curvature), stall AOA, and wing velocity. AOA is an abbreviation for Angle of Attack. As an example, the lift adjustment mechanism 140 has a tilt mechanism 141 and a flap 142.

[0030] The tilt mechanism 141 is driven to adjust the tilt angle of the rotor blade 130. The tilt mechanism 141, together with a motor, inverter, etc. that drive the tilt mechanism 141, constitutes a tilt adjustment device. The tilt adjustment device, including the tilt mechanism 141, is provided, for example, individually for the rotor blade 130. The tilt mechanism 141 adjusts the tilt angle of the rotor blade 130 by adjusting the relative inclination of the rotor blade 130 with respect to the aircraft body.

[0031] During takeoff and landing, the tilt mechanism 141 controls the tilt angle so that the axis of each rotor 130 approaches a position parallel to the vertical direction. As a result, the thrust from the rotation of each rotor 130 acts on the eVTOL 100 mainly as rotational lift. Therefore, the eVTOL 100 can perform short-distance takeoffs and landings and vertical takeoffs and landings. Note that in Figure 1, the vertical direction is perpendicular to the plane of the paper.

[0032] During cruising, the tilt mechanism 141 controls the tilt angle so that the axis of each rotor 130 approaches a position parallel to the horizontal. As a result, the thrust generated by the rotation of each rotor 130 acts on the eVTOL 100 primarily as thrust. Therefore, the eVTOL 100 can move forward by obtaining gliding lift from the fixed wings 120 and by the forward thrust generated by the rotation of each rotor 130. Furthermore, the gliding lift can be adjusted by changing the wing velocity through the thrust.

[0033] Although an example of providing the tilt mechanism 141 individually for each rotor blade 130 has been shown, the invention is not limited to this. For example, the tilt angles of multiple rotor blades 130 arranged side by side may be controlled by a common tilt mechanism. Alternatively, the rotor blade 130 may be integrated with a part of the blade section, and the part of the blade section and the rotor blade 130 may be displaced together by the tilt mechanism.

[0034] The flaps 142 are movable wing segments and are mounted on the fixed wings 120. The flaps 142, together with the motor and inverter that drive them, constitute a flap adjustment device. The flaps 142 are sometimes referred to as high-lift devices. As an example, multiple flaps 142 are provided on the trailing edge of the main wing 121. Each of the multiple flaps 142 is provided with a motor and inverter. In addition to the main wing 121, the flaps 142 may also be provided on the tail wing 122. The flaps 142 may also be provided on the leading edge of the fixed wing 120.

[0035] The flaps 142 adjust the surface area and camber of the fixed wing 120. For example, by controlling the flaps 142 provided on the main wing 121 to a downward position, the gliding lift acting on the main wing 121 increases. In addition, it is possible to further increase the gliding lift by moving the flaps 142 in a direction that protrudes from the main wing 121.

[0036] The lift adjustment mechanism 140 is not limited to the tilt mechanism 141 and flap 142 described above. The lift adjustment mechanism 140 may also employ a tilt mechanism that adjusts the relative inclination of the fixed wing 120 with respect to the aircraft body 110. In this case, the angle of attack of the fixed wing 120 can be adjusted. The lift adjustment mechanism 140 may also employ a thrust rotor separate from the rotor 130. In this case, the wing speed can be adjusted. Furthermore, by providing a thrust rotor, the rotor 130 can be dedicated solely to lift (rotational lift).

[0037] A variable wing may be used as the lift adjustment mechanism 140. Lift can be adjusted by changing the surface area, camber, and angle of attack of the fixed wing 120. A high-lift device other than the flap 142, such as a slat, may also be used as the lift adjustment mechanism 140. The slat is provided on the leading edge of the main wing 121. By moving the slat forward relative to the main wing 121, a gap is created between the slat and the main wing 121, delaying separation. Therefore, lift can be increased without stalling up to higher angles of attack. In other words, the stall angle of attack (AOA) can be delayed.

[0038] The battery cooling device 200 has multiple battery cells, which will be described later, and is a device capable of cooling each battery cell. Each battery cell is a rechargeable secondary battery capable of storing DC power. Each battery cell supplies power to the EPU 150, ECU 170, tilt adjustment device, and flap adjustment device. In addition, each battery cell supplies power to auxiliary equipment not shown, such as an air conditioning system.

[0039] As an example, the eVTOL 100 of this embodiment is equipped with a plurality of battery cooling devices 200. The plurality of battery cooling devices 200 may be connected to each other in series and / or in parallel, or they may be arranged independently without being connected to each other. The battery cooling devices 200 may be provided individually for each EPU 150, or they may be provided redundantly for each EPU 150.

[0040] Here, since multiple battery cells include, for example, tens or hundreds of them, the battery cooling device 200 is heavy. Therefore, the balance of the aircraft body 110 can be maintained by placing each battery cooling device 200 in two locations on the left and right sides of the main wing 121. Of course, the battery cooling devices 200 may also be placed on the aircraft body 110.

[0041] The EPU150 has a motor and inverter and rotates the rotor blades 130 that provide thrust to the eVTOL100. EPU is an abbreviation for Electric Propulsion Unit. As an example, the same number of EPU150s are provided as the number of rotor blades 130. In other words, the eVTOL100 is equipped with six EPU150s. The EPU150s and rotor blades 130s are connected one-to-one. Alternatively, a configuration in which two or more rotor blades 130s are connected to one EPU150 via a gearbox is also possible.

[0042] The BMS160 monitors the status of each battery pack in the battery cooling device 200. BMS stands for Battery Management System. For example, one BMS160 is provided for each battery cooling device 200. By monitoring the status of each battery pack in multiple battery cooling devices 200, the BMS160 may, for example, predict or detect abnormalities in each battery cooling device 200.

[0043] The ECU170 controls the flight of the eVTOL100. ECU stands for Electronic Control Unit. The ECU170 controls the flight of the eVTOL100 according to the flight state controlled by the pilot, the pilot remotely, or the control system. The ECU170 performs flight control based on the detection results of the BMS160 and various sensors. For example, the ECU170 controls the drive of the motors of the EPU150, the tilt adjustment device motor, and the flap adjustment device motor. The ECU170 may also perform control of auxiliary equipment.

[0044] <Battery cooling system> As shown in Figure 2, the battery cooling system 300 includes a battery cooling device 200, a low-temperature cooling device 400, and a control device 500. The vertical direction when the eVTOL 100 is stationary on the ground is referred to as the up-down direction. In the up-down direction, the upper side points to the sky and the lower side points to the ground.

[0045] The battery cooling device 200 includes a cooling tank 210, multiple battery cells 220, insulating liquid 230, and valve fittings 240 and 250.

[0046] The cooling tank 210 constitutes the housing of the battery cooling device 200. The cooling tank 210 has an outer wall surface 211 and an inner wall surface 212, as well as an internal space 213. The cooling tank 210 is made of a resin such as CFRP or a metal such as Al.

[0047] The cooling tank 210 has, for example, a lid portion on the upper side in the vertical direction. The lid portion can be attached to and removed from the other parts. This allows multiple battery cells 220 to be inserted into and removed from the space 213 of the cooling tank 210. Furthermore, the inside of the cooling tank 210 may or may not be completely sealed.

[0048] The battery cell 220 is a secondary battery that generates an electromotive force through a chemical reaction. Examples of battery cells 220 include lithium-ion secondary batteries, nickel-metal hydride secondary batteries, and organic radical batteries. The battery cell 220 may be a secondary battery with a liquid electrolyte, or a so-called all-solid-state battery with a solid electrolyte.

[0049] Multiple battery cells 220 have a common structure to each other. The number and arrangement of the multiple battery cells 220 are not particularly limited. Multiple battery cells 220 may be connected in series, or in parallel and series. As an example, the battery cells 220 in this embodiment are connected in series. An electrical connection structure of multiple battery cells 220 is sometimes called a battery pack. A battery pack is a so-called battery pack. Multiple battery cells 220 are housed in the space 213 of the cooling tank 210.

[0050] The battery cell 220 comprises a power generation element and a battery case that houses the power generation element. The battery case provides the outer casing of the battery cell 220. The battery case is formed using, for example, a metal material. The shape of the battery cell 220, and thus the battery case, is not particularly limited. For example, a cylindrical shape, a rectangular shape, etc., can be adopted. As an example, the battery cell 220 of this embodiment has a rectangular shape, specifically a thin, flattened shape.

[0051] The battery cell 220 is, for example, a laminated battery. The battery cell 220 has a top surface, a bottom surface, and four sides. The top surface is the surface facing upwards in the vertical direction. The bottom surface is the surface opposite to the top surface in the vertical direction and is the surface facing the ground. The sides are surfaces that connect the top surface and the bottom surface and are surfaces that are aligned in the vertical direction.

[0052] Multiple battery cells 220 are arranged in a direction perpendicular to the vertical direction. Furthermore, the battery cells 220 are spaced apart from each other by a gap 221. Each battery cell 220 has two electrode terminals.

[0053] One electrode terminal is electrically connected to the positive electrode of the battery cell 220. This electrode terminal is sometimes referred to as the positive terminal, P terminal, etc. The other electrode terminal is electrically connected to the negative electrode of the battery cell 220. This electrode terminal is sometimes referred to as the negative terminal, N terminal, etc. The electrode terminals are sometimes referred to as current collection tabs.

[0054] Multiple battery cells 220 are arranged such that their upper surfaces are approximately equal in position in the vertical direction. The relative positions of the multiple battery cells 220 are fixed by a fixing member (not shown). The fixing member may be, for example, a case or a restraining member such as a band.

[0055] In the above-described arrangement, the electrode terminals of adjacent battery cells 220 are electrically connected to each other by busbars 222, which are wiring components. In other words, multiple battery cells 220 are connected in series by busbars 222.

[0056] Two busbars, one for the positive electrode and one for the negative electrode, protrude from the space 213 of the cooling tank 210 to the outside of the cooling tank 210. If the cooling tank 210 is made of metal, insulating components such as insulating sealant are placed in the part of the cooling tank 210 through which the busbars 222 penetrate, thereby providing electrical insulation between the cooling tank 210 and the busbars 222. Note that in Figure 2, only one of the two busbars is visible. Also, insulating components are omitted in Figure 2.

[0057] The insulating liquid 230 is a heat transfer medium that is fluidly contained in the space 213 of the cooling tank 210. The insulating liquid 230 immerses each battery cell 220 and absorbs heat from each battery cell. The insulating liquid 230 is also provided in the space 213 of the cooling tank 210 such that at least a portion of the busbars 222 are in direct contact with the insulating liquid 230.

[0058] The insulating liquid 230 is provided in the cooling tank 210 such that air remains above the space 213 of the cooling tank 210. This prevents the pressure in the space 213 from becoming excessively high due to thermal expansion or evaporation of the insulating liquid 230 as the temperature rises.

[0059] As the insulating liquid 230, for example, a non-flammable fluorine-based liquid can be used. Non-flammable means that the substance or object does not burn and is not easily ignited by sparks or heat, and is also non-flammable. A non-flammable fluorine-based insulating liquid 230 can suppress or prevent heat chain reactions when the battery cell 220 experiences thermal runaway. In other words, a fluorine-based insulating liquid 230 has the advantage of being highly safe.

[0060] The non-flammable fluorine-based insulating liquid 230 has a boiling point of, for example, 100°C to 250°C. In contrast, the normal operating temperature of the battery cell 220 is, for example, 10°C to 60°C. Therefore, the non-flammable fluorine-based insulating liquid 230 does not boil during normal use of the battery cell 220. However, if the temperature of the battery cell 220 rises, the non-flammable fluorine-based insulating liquid 230 will boil, which can suppress the temperature rise of the battery cell 220 that has experienced thermal runaway. Furthermore, it can suppress and prevent the heat chain reaction in the battery cell 220.

[0061] If the boiling point of the insulating liquid 230 is low, for example, 100°C, then the abnormally overheating battery cell 220 can be boiled and cooled at a low temperature, while other normal battery cells 220 can be used at a relatively low temperature. If the boiling point of the insulating liquid 230 is high, for example, 250°C, then the insulating liquid 230 is less likely to evaporate during normal use. In other words, the insulating liquid 230 has a low vapor pressure. This has the advantage of reducing leakage of the insulating liquid 230 from the cooling tank 210 to the outside.

[0062] As the non-flammable fluorine-based insulating liquid 230, for example, Galden (registered trademark) manufactured by Solvay, Asahiclean (registered trademark) manufactured by AGC, Opteon (registered trademark) manufactured by Chemours, etc. can be used.

[0063] Another example of an insulating liquid 230 is oil. Because oil has low volatility, there is less leakage from the cooling tank 210 to the outside. It is also inexpensive.

[0064] As oils, for example, ExxonMobil's SPECTRASYN®, Chevron Phillips Chemicals' SYNFLUID®, and M&I Materials' MIVOLT® can be used. In addition, other oils such as Engineered Fluids' AmpCool and Shin-Etsu Chemical's silicone oil can be used.

[0065] The valve joints 240 and 250 are connection points to which the low-temperature cooling device 400 is attached and detached. That is, the cooling tank 210 is attached to and detached from the low-temperature cooling device 400 via the valve joints 240 and 250. When the valve joints 240 and 250 are connected to the low-temperature cooling device 400, they allow the passage of the insulating liquid 230, while when they are not connected to the low-temperature cooling device 400, they block the passage of the insulating liquid 230.

[0066] For example, valve fittings 240 and 250 can be manually switched to the open position after the cryogenic cooler 400 is connected. Alternatively, valve fittings 240 and 250 can be manually switched to the closed position before the cryogenic cooler 400 is disconnected. Or, they may be mechanically switched to the open position when the cryogenic cooler 400 is connected to valve fittings 240 and 250. Alternatively, they may be mechanically switched to the closed position when the cryogenic cooler 400 is disconnected from valve fittings 240 and 250.

[0067] Here, the central position of the cooling tank 210 in the vertical direction is defined as the reference position. In this embodiment, one valve fitting 240 is connected to a pipe 241 located above the reference position in the cooling tank 210. The other valve fitting 250 is connected to a pipe 251 located below the reference position in the cooling tank 210. This allows, for example, when discharging the insulating liquid 230 inside the cooling tank 210 to the outside via the valve fitting 250 located at the bottom of the cooling tank 210, the insulating liquid 230 can be discharged from the cooling tank 210 to the outside by gravity. In this case, insulating liquid 230 located above the valve fitting 250 in the vertical direction can be discharged to the outside.

[0068] Furthermore, both valve fittings 240 and 250 may be located below the reference position in the cooling tank 210 in the vertical direction. Alternatively, both valve fittings 240 and 250 may be located above the reference position in the cooling tank 210 in the vertical direction. In other words, the valve fittings 240 and 250 only need to be located in the cooling tank 210 where the insulating liquid 230 exists. By offsetting the valve fittings 240 and 250 in the vertical or horizontal direction, it is possible to discharge more of the insulating liquid 230 from the cooling tank 210 or circulate less stagnant (non-flowing) areas. In addition, each valve fitting 240 and 250 may be installed directly in the cooling tank 210 without going through the respective pipes 241 and 251.

[0069] The low-temperature cooling device 400 is a device for cooling and storing the insulating liquid 230. The low-temperature cooling device 400 is also connected to the valve fittings 240 and 250 of the cooling tank 210, thereby enabling the flow of the insulating liquid 230 inside the cooling tank 210 into and out of the tank.

[0070] The cryogenic cooling device 400 includes a tank 410 for storing insulating liquid 230, pipes 420 and 430 connected to the tank 410, and a pump 440 for pumping the insulating liquid 230 from the tank 410 into the pipes 430. Although not shown, the cryogenic cooling device 400 also includes cooling equipment for cooling and maintaining the temperature of the insulating liquid 230 in the tank 410.

[0071] The pipes 420 and 430 are, for example, hoses. One pipe 420 is connected to one valve fitting 240. The other pipe 430 is connected to the other valve fitting 250. In this way, the battery cooling device 200 and the low-temperature cooling device 400 are connected via valve fittings 240 and 250 and pipes 420 and 430, thereby forming a cooling circulation circuit 460 in which insulating liquid 230 can circulate between the battery cooling device 200 and the low-temperature cooling device 400.

[0072] Furthermore, the other pipe 430 may be equipped with a discharge valve 450 for discharging the high-temperature insulating liquid 230 from the cooling tank 210. This allows for faster discharge of the high-temperature insulating liquid 230 from inside the cooling tank 210. Of course, the discharge valve 450 does not have to be provided on the other pipe 430. If the only purpose is to circulate the insulating liquid 230 in the cooling circulation circuit 460, the discharge valve 450 is unnecessary.

[0073] A low-temperature cooling device 400 is provided for each battery cooling device 200, for example. Alternatively, multiple sets of pipes 420 and 430 may be provided in parallel to a single low-temperature cooling device 400. In this case, each pipe 420 and 430 is connected to each battery cooling device 200.

[0074] The cryogenic cooling unit 400 is connected to the cooling tank 210 after the eVTOL 100 has landed. As shown in Figure 3, during takeoff, cruising, and landing of the eVTOL 100, the battery cooling unit 200 is detached from the cryogenic cooling unit 400 and is located inside the eVTOL 100. The cryogenic cooling unit 400 is located outside the eVTOL 100.

[0075] Furthermore, the cryogenic cooling device 400 may be connected to the cooling tank 210 simultaneously with the landing of the eVTOL 100. Conversely, the cryogenic cooling device 400 may be detached from the cooling tank 210 simultaneously with the takeoff of the eVTOL 100.

[0076] The control device 500 is a device that controls the low-temperature cooling device 400. The control device 500 controls, for example, the rotational speed (pumping capacity) of the pump 440 and the cooling temperature of the cooling section. The control device 500 consists of a well-known microcomputer including a processor, ROM, RAM, etc., and its peripheral circuits. The control device 500 performs various calculations and processes based on the control program stored in the ROM.

[0077] If multiple low-temperature cooling devices 400 are provided, a control device 500 may be provided for each battery cooling device 200, or one control device 500 may control multiple battery cooling devices 200.

[0078] <Cooling method> Next, the cooling method for each battery cell 220 will be described. As shown in Figure 3, during takeoff, cruising, and landing of the eVTOL 100, the heat from each battery cell 220 is stored in the insulating liquid 230 in the cooling tank 210. This cools each battery cell 220.

[0079] On the other hand, after the eVTOL100 lands, each battery cooling device 200 mounted on the eVTOL100 is connected to a cryogenic cooling device 400, as shown in Figure 2. This creates a cooling circulation circuit 460 between the battery cooling devices 200 and the cryogenic cooling device 400.

[0080] The control device 500 circulates the insulating liquid 230, which has been pre-cooled in the low-temperature cooling device 400, into the cooling circulation circuit 460 using the pump 440. For example, the low-temperature insulating liquid 230 is introduced into the cooling tank 210 via a valve fitting 250 located at the bottom of the cooling tank 210, and the high-temperature insulating liquid 230 is returned to the tank 410 of the low-temperature cooling device 400 via a valve fitting 240 located at the top of the cooling tank 210. In this case, the pump 440 is controlled to pressurize the low-temperature insulating liquid 230 into the piping 430. By circulating the insulating liquid 230 into the cooling circulation circuit 460 in this way, each battery cell 220 inside the cooling tank 210 is rapidly cooled.

[0081] Alternatively, the low-temperature insulating liquid 230 may be introduced into the cooling tank 210 via a valve fitting 240 located at the top of the cooling tank 210, and the high-temperature insulating liquid 230 may be returned to the tank 410 of the low-temperature cooling device 400 via a valve fitting 250 located at the bottom of the cooling tank 210. In this case, the pump 440 is controlled to pump the low-temperature insulating liquid 230 into the piping 420.

[0082] <Flight Pattern> Figure 4 shows an example of the simplest flight pattern for the eVTOL100, from takeoff to landing. The flight patterns for other electric aircraft are similar to those of the eVTOL100.

[0083] The period from time T10 to time T11 is referred to as the takeoff period, takeoff time, departure period, departure time, etc. Hereafter, the period from time T10 to time T11 will be referred to as the takeoff time. The takeoff time refers to the climb from the landing state to the cruising altitude of the eVTOL100. The period from time T11 to time T12 is referred to as the cruising period, cruising time, etc. The period from time T12 to time T13 is referred to as the landing period, landing time, arrival period, arrival time, etc. Hereafter, the period from time T12 to time T13 will be referred to as the landing time. The landing time refers to the operation of the eVTOL100 from the cruising altitude of the destination to the ground when it lands. For convenience, in Figure 4, the required power, i.e., the output, is kept constant for almost the entire duration of each period.

[0084] During the period from time T10 to time T11, eVTOL100 climbs from the takeoff point to the cruising start altitude. During the period from time T11 to time T12, eVTOL100 cruises at a predetermined altitude. During the period from time T12 to time T13, eVTOL100 descends from the altitude at the end of time T12 to the landing point.

[0085] The movement of the eVTOL 100 mainly includes a horizontal component during cruising and mainly includes a vertical component during takeoff and landing. During takeoff and landing, when moving vertically, the drive of the rotor blades 130 of the eVTOL 100 requires high power output continuously for a predetermined period of time.

[0086] This high output places a significant load on the drive equipment for propelling the rotor blades 130, such as the battery cells 220 and the EPU 150. For example, each battery cell 220 generates heat, causing its temperature to rise. This is because the heat generated by each battery cell 220 is proportional to the output.

[0087] After the eVTOL100 lands, each battery cell 220 is charged on the ground. Once each battery cell 220 is fully charged, the eVTOL100 takes off again and begins cruising.

[0088] During flight (discharge) and on the ground (charge) of the eVTOL100, the battery temperature of each battery cell 220 changes as follows: First, during takeoff, the battery temperature of each battery cell 220 rises rapidly. During cruising, since less battery output is required than during takeoff, the battery temperature of each battery cell 220 rises gradually. During landing, since the same battery output as during takeoff is required, the battery temperature of each battery cell 220 rises rapidly.

[0089] During the flight period (discharge) from time T10 to time T13, from takeoff to landing, the insulating liquid 230 in the battery cooling device 200 stores heat and cools the heat of each battery cell 220. This suppresses the temperature rise of the high-power battery cells 220 (heat storage cooling), while transferring heat to the other low-power (low-temperature) battery cells 220 via the insulating liquid 230, further lowering the temperature of the high-temperature battery cells 220 and raising the temperature of the low-temperature battery cells 220. In other words, the temperature of each battery cell 220 can be made uniform. Therefore, at time T13, when the eVTOL 100 has completed landing, each battery cell 220 can be kept below its allowable temperature.

[0090] One of the purposes of equalizing the temperature of each battery cell 220 is to prevent a specific battery cell 220 from overheating, thus avoiding a safety concern that could affect the overall performance (safety) of the battery pack. For example, while many other battery cells 220 still have plenty of headroom before reaching their temperature limit, if a specific battery cell 220 is overheating, it could limit the remaining flight time of the entire battery pack, potentially requiring emergency measures such as switching to an emergency landing pattern. However, by lowering the temperature of the overheating battery cell 220, it becomes possible to avoid emergency measures during flight.

[0091] The period from time T13 to time T16 is the ground (charging) period during which each battery cell 220 is charged on the ground and high-performance cooling is performed on each battery cell 220. First, at time T13, each battery cooling device 200 of the eVTOL 100 is connected to the low-temperature cooling device 400. As a result, as described above, the low-temperature insulating liquid 230 circulates in the cooling circulation circuit 460, causing the battery temperature to drop rapidly.

[0092] Furthermore, between time point T13 and time point T14, the busbar 222 of the battery cooling device 200 is connected to the charging device. Note that when the battery cooling device 200 is connected to the low-temperature cooling device 400, the busbar 222 of the battery cooling device 200 may also be connected to the charging device at the same time. The charging device may be included in the low-temperature cooling device 400 or may be independent of the low-temperature cooling device 400.

[0093] Charging of each battery cell 220 begins at time T14. As a result, each battery cell 220 generates heat, so the decrease in battery temperature is gradual. When charging of each battery cell 220 is complete at time T15, each battery cell 220 and the busbar 222 no longer generate heat, and the battery temperature drops rapidly due to cooling by the low-temperature insulating liquid 230. Thus, high-performance cooling of each battery cell 220 is completed at time T16. From time T16 onward, the flight (discharge) and ground (charge) cycle described above from time T10 to time T16 is repeated.

[0094] As described above, in the battery cooling device 200 of this embodiment, a plurality of battery cells 220 are housed inside the cooling tank 210, and each battery cell 220 is immersed in an insulating liquid 230. Furthermore, the insulating liquid 230 is made flowable inside the cooling tank 210, and valve fittings 240 and 250 are provided on the cooling tank 210 to allow the attachment and detachment of the low-temperature cooling device 400 located outside the cooling tank 210.

[0095] As a result, during takeoff, cruising, and landing of the eVTOL100, the heat generated by each battery cell 220 can be absorbed by the flowable insulating liquid 230 in which each battery cell 220 is directly immersed, thereby suppressing the temperature rise and temperature distribution of each battery cell 220. Furthermore, by immersing multiple battery cells 220 in the insulating liquid 230 in a single cooling tank 210, the insulating liquid 230 flows (convection), allowing the temperature of multiple battery cells 220 to be equalized. Therefore, the temperature of the battery cell 220 with the highest temperature among all the battery cells 220 can be lowered, and consequently, the temperature of all battery cells 220 can be equalized.

[0096] Furthermore, when the eVTOL100 is on the ground, especially when each battery cell 220 is being charged, a low-temperature cooling device 400 capable of circulating and cooling the insulating liquid 230 is connected to the valve fittings 240 and 250 of the cooling tank 210, and the insulating liquid 230 is circulated in the cooling circulation circuit 460. This allows each battery cell 220 in the cooling tank 210 to be forcibly cooled. Thus, the temperature of each battery cell 220 can be lowered while each battery cell 220 is being charged.

[0097] Furthermore, instead of having a separate cooler for each of the battery cells 220, that is, instead of having multiple coolers for every single battery cell 220, all the battery cells 220 can be cooled by a single cooling tank 210. Therefore, the weight of the battery cooling device 200 can not be increased, and its size can be avoided.

[0098] In the battery cooling device 200 of this embodiment, at least a portion of the busbar 222 is immersed in the insulating liquid 230. Therefore, the temperature of the busbar 222 can be lowered. In addition, heat can be absorbed from inside each battery cell 220 through the busbar 222 to the insulating liquid 230. Therefore, the temperature distribution within each battery cell 220 can be reduced.

[0099] (Second Embodiment) This embodiment will primarily describe the differences from the first embodiment. As shown in Figure 5, the cooling tank 210 has fins 260. The fins 260 have the function of dissipating heat from inside the cooling tank 210 to the outside. In addition to heat dissipation, the fins 260 also function as ribs. The ribs are reinforcing ribs that reinforce the strength of the cooling tank 210.

[0100] The fins 260 are provided on both the outer wall surface 211 and the inner wall surface 212 that constitute the cooling tank 210. However, as shown in Figures 7 and 8 later, the fins 260 may be provided on either the outer wall surface 211 or the inner wall surface 212. The fins 260 are provided on the portion of the outer wall surface 211 and the inner wall surface 212 of the cooling tank 210 corresponding to the area where the insulating liquid 230 is present.

[0101] The fins 260 may be provided in areas where the insulating liquid 230 is not present. For example, the fins 260 may be provided on the outer wall surface 211 and the inner wall surface 212 of the lid portion of the cooling tank 210.

[0102] The fins 260 are integrally formed with the cooling tank 210. The fins 260 may be provided separately from the cooling tank 210, or they may be integrated by being joined to the cooling tank 210.

[0103] If the cooling tank 210 is made of a metal such as Al, the fins 260 are integrally formed with the cooling tank 210 by methods such as die casting, extrusion, or forging. If the metal cooling tank 210 and the metal fins 260 are prepared separately, the fins 260 are joined to the cooling tank 210 by methods such as welding, brazing, or bonding. If the fins 260 are made of metal, it is preferable that the fins 260 are made of the same material as the cooling tank 210.

[0104] Alternatively, if the cooling tank 210 is made of a resin such as CFRP, the fins 260 are integrally formed with the cooling tank 210 by methods such as injection molding or extrusion. If the resin cooling tank 210 and the resin fins 260 are prepared separately, the fins 260 are joined to the cooling tank 210 by methods such as bonding or welding. If the fins 260 are made of resin, it is preferable that the fins 260 are made of the same material as the cooling tank 210.

[0105] Of course, the resin fins 260 may be joined to the metal cooling tank 210 to form a single unit, or the metal fins 260 may be joined to the resin cooling tank 210 to form a single unit.

[0106] With the above configuration, the fins 260 reduce the thermal resistance from each battery cell 220 to the outside of the cooling tank 210, making it easier to dissipate heat from inside the cooling tank 210 to the outside. Therefore, the temperature rise of each battery cell 220 can be suppressed. In addition, the fins 260 also function as ribs in the cooling tank 210, improving the strength of the cooling tank 210. Consequently, the weight of the cooling tank 210 can be reduced.

[0107] Here, to promote heat dissipation from the cooling tank 210, the airflow from the aircraft may be used. In this case, the cooling tank 210 is mounted on the main wing 121 of the eVTOL 100 so that it is exposed from the main wing 121. Alternatively, the cooling tank 210 is mounted on the main wing 121 so that the airflow from the aircraft, guided from the outer wall of the main wing 121 into the interior of the main wing 121, directly hits the cooling tank 210. This promotes heat dissipation, thereby improving the heat dissipation performance of the cooling tank 210 by the fins 260.

[0108] As a variation, as shown in Figure 6, a fan 261 may be installed next to the cooling tank 210 to promote heat dissipation from the cooling tank 210. The fan 261 may be fixed to the cooling tank 210 via a separate component, or it may be fixed to the internal structure of the main wing 121 of the eVTOL 100. This will further promote heat dissipation from the cooling tank 210 by forcing air onto the fins 260 of the cooling tank 210.

[0109] Fan 261 is controlled, for example, by BMS160. Of course, fan 261 may be controlled by a control device other than BMS160. For example, it may be controlled by a dedicated device for fan 261. Alternatively, it may be controlled by another control device installed on the eVTOL100.

[0110] The fan 261 is positioned, for example, in front of the cooling tank 210 in the direction of travel of the eVTOL 100. The number of fans 261 is not limited to one; multiple fans 261 may be positioned outside the cooling tank 210. For example, one fan 261 may be positioned on one outer wall surface 211 of the cooling tank 210, or multiple fans 261 may be positioned on one outer wall surface 211.

[0111] As a variation, as shown in Figure 7, the fins 260 may be provided only on the outer wall surface 211 of the cooling tank 210. Alternatively, as shown in Figure 8, the fins 260 may be provided only on the inner wall surface 212 of the cooling tank 210.

[0112] Alternatively, the fins 260 may be provided only on a specific outer wall surface 211, only on a specific inner wall surface 212, or on both a specific outer wall surface 211 and an inner wall surface 212. In other words, within a single cooling tank 210, the locations where the fins 260 are provided may be a mixture of areas where they are provided only on the outer wall surface 211, areas where they are provided only on the inner wall surface 212, and areas where they are provided on both the outer wall surface 211 and an inner wall surface 212.

[0113] (Third embodiment) This embodiment will mainly describe the differences from the first and second embodiments. As shown in Figure 9, the cooling tank 210 is equipped with a fluidizing device 270 for fluidizing the insulating liquid 230. In this embodiment, the fluidizing device 270 is an agitator 271.

[0114] The agitator 271 includes, for example, an agitator blade, a shaft fixed to the agitator blade, and a drive device for rotating the shaft. The agitator 271 is located, for example, at the bottom of the inside of the cooling tank 210. The agitator blade rotates to move the insulating liquid 230 from the bottom to the top of the cooling tank 210.

[0115] The drive unit for the agitator 271 is controlled, for example, by the BMS 160. Of course, the drive unit for the agitator 271 may be controlled by a control device other than the BMS 160. For example, it may be controlled by a dedicated device for the drive unit of the agitator 271. Alternatively, it may be controlled by another control device mounted on the eVTOL 100.

[0116] With the above configuration, the stirring device 271 moves a portion of the insulating liquid 230 from the bottom to the top of the cooling tank 210, while the insulating liquid 230 located away from the stirring device 271 moves from the top to the bottom of the cooling tank 210. In other words, the insulating liquid 230 is stirred inside the cooling tank 210. Therefore, the cooling performance of the cooling tank 210 can be improved, and the uniform temperature of each battery cell 220 can be promoted.

[0117] As shown in Figure 9, the cooling performance and temperature equalization performance can be improved by combining the fins 260 and fan 261 with the agitator 271. Of course, the cooling tank 210 may be equipped only with the agitator 271 without the fins 260 and fan 261. Furthermore, the agitator 271 is not limited to being located at the bottom of the cooling tank 210, but may be placed anywhere as long as it can generate flow in the insulating liquid 230. Moreover, there may be more than one agitator 271, and multiple agitators 271 may be provided in the cooling tank 210.

[0118] As a modified example, as shown in Figure 10, the fluidizing device 270 may consist of piping 241, piping 251, a three-way valve 272, a pump 273, and piping 274. The three-way valve 272 and the pump 273 are connected to piping 251 located at the bottom of the cooling tank 210, and piping 241 located at the top of the cooling tank 210 is connected to the three-way valve 272 via piping 274. This creates a path through which the insulating liquid 230 circulates through the cooling tank 210, piping 241, piping 251, the three-way valve 272, the pump 273, and piping 241.

[0119] The three-way valve 272 is a solenoid valve that switches between a state in which the insulating liquid 230 at the top of the cooling tank 210 flows into the bottom of the cooling tank 210 and a state in which it does not flow. The pump 273 pumps the insulating liquid 230 flowing from the piping 241 through the three-way valve 272 to the bottom of the cooling tank 210.

[0120] The three-way valve 272 and pump 273 are controlled, for example, by the BMS 160. Of course, the three-way valve 272 and pump 273 may be controlled by a control device other than the BMS 160. For example, they may be controlled by a dedicated device for the three-way valve 272 and pump 273. Alternatively, they may be controlled by other control devices mounted on the eVTOL 100.

[0121] During flight (discharge) of the eVTOL100, the three-way valve 272 connects piping 274 and piping 251. In addition, the pump 273 pumps insulating liquid 230 to the bottom of the cooling tank 210. As a result, the insulating liquid 230 circulates through the cooling tank 210, piping 241, piping 274, and piping 251, allowing each battery cell 220 to be cooled efficiently and its temperature to be uniform.

[0122] When the eVTOL100 is on the ground (during charging), the three-way valve 272 shuts off piping 274 and piping 251. The three-way valve 272 is also connected to piping 430 of the cryogenic cooling device 400. In other words, the three-way valve 272 functions as a valve joint. As a result, the low-temperature insulating liquid 230 is pumped from the cryogenic cooling device 400 to the cooling tank 210.

[0123] Furthermore, when the eVTOL 100 is on the ground (during charging), the insulating liquid 230 may be pumped from the cryogenic cooling device 400 to the cooling device 210 by operating the pump 273 externally attached to the cooling tank 210. Of course, both the pump 440 of the cryogenic cooling device 400 and the pump 273 of the cooling tank 210 may be operated to pump the insulating liquid 230 to the cooling tank 210. When the eVTOL 100 is on the ground (during charging), the control device 500 may also control the three-way valve 272 and the pump 273.

[0124] As a modified example, as shown in Figure 11, the fluidizing device 270 may consist of piping 241, piping 251, a three-way valve 272, a pump 273, piping 274, and a heat exchanger 275. The heat exchanger 275 is connected to the external piping 274 of the cooling tank 210. The heat exchanger 275 is, for example, a dedicated part for the cooling tank 210. The heat exchanger 275 may be replaced with one mounted on the eVTOL 100.

[0125] The heat exchanger 275 is, for example, a radiator or a chiller. The radiator exchanges heat between the insulating liquid 230 and air. The chiller exchanges heat between the insulating liquid and the refrigerant of the refrigeration cycle.

[0126] As described above, the heat exchanger 275 is provided in the piping 274, which allows the insulating liquid 230 to be cooled even during flight (discharge) of the eVTOL 100. Therefore, a low-temperature insulating liquid 230 can be supplied to each battery cell 220 at all times, further improving the cooling performance of the insulating liquid 230 and the uniform temperature performance of each battery cell 220.

[0127] In this embodiment, the three-way valve 272 corresponds to the valve joint.

[0128] (Fourth Embodiment) This embodiment will mainly describe the differences from the first to third embodiments. As shown in Figure 12, the cooling tank 210 has a latent heat storage material 280 that provides a cooling effect.

[0129] The latent heat storage material 280 is sometimes referred to as PCM. PCM is an abbreviation for Phase change material. The latent heat storage material 280 stores or releases heat by utilizing the inflow and outflow of latent heat associated with phase change. In this embodiment, a resin heat storage material containing microcapsule latent heat storage material is used as the latent heat storage material 280. Microcapsule latent heat storage material is a heat storage material in which latent heat storage material is sealed inside microcapsules.

[0130] As the latent heat storage material 280, a latent heat storage material with a phase change temperature (melting point) of 60°C or lower can be used. Specifically, as the latent heat storage material 280, for example, paraffinic hydrocarbons, hydrate-based materials, metallic materials, and aqueous materials can be used.

[0131] The latent heat storage material 280 is added to the insulating liquid 230. A certain amount of the latent heat storage material 280 is included in the insulating liquid 230, and it is also dispersed in the insulating liquid 230. As a result, the heat capacity of the insulating liquid 230 containing the latent heat storage material 280 increases.

[0132] During flight (discharge) of the eVTOL100, heat from each battery cell 220 is absorbed by both the insulating liquid 230 and the latent heat storage material 280. Therefore, the temperature rise of each battery cell 220 can be effectively suppressed.

[0133] As a variation, as shown in Figure 13, a filter 214 may be installed inside the cooling tank 210 to block the passage of the latent heat storage material 280 so that the latent heat storage material 280 does not flow out of the cooling tank 210. Of course, the insulating liquid 230 can pass through the filter 214.

[0134] The filter 214 is provided at the connection point between the piping 241 and the cooling tank 210. The filter 214 may also be provided at the connection point between the piping 251 and the cooling tank 210. This allows the latent heat storage material 280 to be kept inside the cooling tank 210.

[0135] As a modified example, as shown in Figure 14, the latent heat storage material 280 may be placed between adjacent battery cells 220, and filters 223 may be installed between the upper and lower surfaces of adjacent battery cells 220. This allows the latent heat storage material 280 to be kept between adjacent battery cells 220.

[0136] In this process, a predetermined amount of latent heat storage material 280 is placed in each predetermined location. Specifically, a large amount of latent heat storage material 280 is placed in the high-heat-generating section of each battery cell 220, and a small amount of latent heat storage material 280 is placed in the low-heat-generating section. In other words, the placement location and amount of microcapsule latent heat storage material can be controlled.

[0137] As described above, by confining the latent heat storage material 280 between adjacent battery cells 220, the temperature distribution due to the heat generation distribution of each battery cell 220 can be suppressed. Furthermore, since the high heat generation parts of each battery cell 220 can be cooled intensively, there is no need to distribute a large amount of the latent heat storage material 280 throughout the insulating liquid 230. Therefore, the amount of latent heat storage material 280 used can be reduced.

[0138] As a modified example, as shown in Figure 15, a fixed heat storage tube may be used as the latent heat storage material 280. When the latent heat storage material 280 is a fixed heat storage tube, more fixed heat storage tubes can be placed in the high-heat-generating parts of each battery cell 220, and fewer fixed heat storage tubes can be placed in the low-heat-generating parts. In other words, the location and size of the fixed heat storage tubes can be controlled.

[0139] The fixed heat storage tube is sandwiched between adjacent battery cells 220 so that the insulating liquid 230 between adjacent battery cells 220 can move in the vertical direction.

[0140] As described above, even when using fixed heat storage tubes, the temperature distribution due to the heat generation distribution of each battery cell 220 can be suppressed. In addition, the amount of fixed heat storage tubes can be reduced.

[0141] Furthermore, both microcapsule latent heat storage material and fixed heat storage tubes may be used as the latent heat storage material 280.

[0142] (Fifth embodiment) This embodiment will mainly describe the differences from the first to fourth embodiments. Figure 16 is a top view of the cooling tank 210 with the lid removed. Figure 17 is a cross-sectional view taken along line XVII-XVII of Figure 16. As shown in Figures 16 and 17, each battery cell 220 has a facing surface 227 that faces the adjacent battery cell 220.

[0143] Furthermore, the battery cooling device 200 has a spacer member 290. The spacer member 290 is sandwiched between adjacent battery cells 220 and is in contact with the opposing surfaces 227 of the adjacent battery cells 220. The spacer member 290 can transfer heat from the battery cells 220 transmitted through the opposing surfaces 227 of the adjacent battery cells 220 to the insulating liquid 230.

[0144] The battery cooling device 200 has a pair of plates 224, 225 and a restraining screw 226 for fixing spacer members 290 between the battery cells 220 to the battery cells 220. The pair of plates 224, 225 are positioned at one end and the other end in the stacking direction of the laminate of each battery cell 220 and spacer member 290, and sandwich the laminate. The restraining screw 226 tightens the laminate so that the pair of plates 224, 225 are brought relatively closer together. In this way, the spacer members 290 and each battery cell 220 are restrained.

[0145] In this embodiment, spacer members 290 are also placed between the battery cells 220 located at both ends of each battery cell 220 and the plate materials 224 and 225. However, the spacer members 290 do not necessarily have to be placed between the battery cells 220 located at both ends of each battery cell 220 and the plate materials 224 and 225. In other words, the battery cells 220 located at both ends of each battery cell 220 and the plate materials 224 and 225 may be in direct contact. In this case, through holes may be provided in the plate materials 224 and 225 so that the insulating liquid 230 can come into direct contact with the battery cells 220 through the through holes.

[0146] As shown in Figure 18, in this embodiment, an offset fin is used as the spacer member 290. The offset fin is a fin in which a partially cut-up portion is formed by cutting up the wave portion of a corrugated cross-sectional shape. The offset fin is made of a metal with excellent thermal conductivity, such as Al.

[0147] The spacer member 290 has a passage portion 291 and a support portion 292. The passage portion 291 is a portion through which the insulating liquid 230 can flow in one direction parallel to the opposing surface 227 of the battery cell 220. The support portion 292 is sandwiched between adjacent battery cells 220 and supports them, thereby maintaining the distance 221 between adjacent battery cells 220. The support portion 292 has sufficient strength to withstand the restraining load when the spacer member 290 and each battery cell 220 are restrained by the restraining screw 226.

[0148] In this embodiment, one direction of the spacer member 290 is substantially aligned with the vertical direction. Therefore, the insulating liquid 230 located between adjacent battery cells 220 can move vertically through the passage portion 291 of the spacer member 290.

[0149] In addition to offset fins, the spacer member 290 may also be a corrugated fin as shown in Figure 19, a wave fin as shown in Figure 20, or a louver fin as shown in Figure 21.

[0150] A corrugated fin is a fin formed by repeatedly folding a metal plate-like member in alternating mountain and valley folds to create a wave-like shape, with alternating peaks and valleys forming a continuous pattern. A wave fin is a fin whose cross-sectional shape is formed in a rectangular or trapezoidal wave pattern, and which is also formed to meander along one direction. A louver fin is a fin in which multiple louvers are formed on the wave portion that constitutes the corrugated cross-section.

[0151] With the above configuration, heat from each battery cell 220 can be transferred to the insulating liquid 230 without disrupting the natural flow of the insulating liquid 230 in one direction. In addition, since the support portion 292 of the spacer member 290 maintains the spacing 221 between adjacent battery cells 220, it becomes possible to restrain both the spacer member 290 and each battery cell 220 while keeping them in contact.

[0152] For example, the microcapsule latent heat storage material shown in the fourth embodiment is very small compared to the width of the passage portion 291 of the spacer member 290, so it can pass through the passage portion 291. Also, when a fixed heat storage tube is used as the latent heat storage material 280, both the spacer member 290 and the fixed heat storage tube are sandwiched between adjacent battery cells 220.

[0153] As a modified example, as shown in Figure 22, an extruded tube may be used as the spacer member 290. The extruded tube is a flattened tube formed from a metal material by extrusion molding. The internal space of the extruded tube corresponds to the passage portion 291. The wall portion that constitutes the space of the extruded tube corresponds to the support portion 292.

[0154] As a modified example, as shown in Figure 23, an inner fin tube may be used as the spacer member 290. The inner fin tube is a tube with a flattened cross-section formed by bending a metal strip, having a bent portion at one end and a crimped portion at the other end, inside which inner fins formed from a metal strip are disposed. The crimped portion at the other end is crimped while the inner fins are in contact with the inner wall of the tube. The internal space of the inner fin tube corresponds to the passage portion 291. Also, the fins inside the inner fin tube correspond to the support portion 292.

[0155] Furthermore, for example, the microcapsule latent heat storage material shown in the fourth embodiment is very small compared to the width of the passage portion 291 of the extruded tube and the inner fin tube, so it can pass through the passage portion 291. Also, when a fixed heat storage tube is used as the latent heat storage material 280, both the extruded tube and the fixed heat storage tube are sandwiched between adjacent battery cells 220. Alternatively, both the inner fin tube and the fixed heat storage tube are sandwiched between adjacent battery cells 220.

[0156] Furthermore, the spacer member 290 is not limited to using one of the following individually: an offset fin, corrugated fin, wave fin, louver fin, extruded tube, or inner fin tube; any combination of these is also acceptable. Of course, three or more types may be combined.

[0157] Furthermore, the spacer member 290 may also be used when the battery cell 220 is can-shaped, i.e., cylindrical. The can-shaped battery cell 220 and the spacer member 290 can be restrained by the aforementioned pair of plate materials 224, 225 and restraining devices such as restraining screws 226.

[0158] In this case, the outer surface of the can-shaped battery cell 220 corresponds to the opposing surface 227. One direction can be set parallel to the axial direction of the battery cell 220. Alternatively, one direction can be set perpendicular to the axial direction of the battery cell 220, i.e., the radial direction.

[0159] The spacer member 290 is not limited to a metal part, as long as it is made of a material that can transfer heat from the battery cells 220 to the insulating liquid 230 while maintaining the distance 221 between adjacent battery cells 220. The spacer member 290 may be made of, for example, a resin material, or it may be made by combining a metal part and a resin part.

[0160] (Sixth Embodiment) This embodiment will primarily describe the differences from the first to fifth embodiments. As shown in Figure 24, the electrode terminals of each battery cell 220 are oriented towards the ground in the vertical direction, so that each busbar 222 is located at the bottom of the cooling tank 210. The busbars 222 are routed from the bottom to the top of the cooling tank 210. In other words, the busbars 222 connecting each battery cell 220 are submerged in the insulating liquid 230.

[0161] According to this, the insulating liquid 230, which has become hot after absorbing heat from the busbar 222 at the bottom of the cooling tank 210, moves to the top of the cooling tank 210. Therefore, convection of the insulating liquid 230 in the vertical direction is promoted, which can improve the cooling performance of the insulating liquid 230 for each battery cell 220.

[0162] As a variation, as shown in Figures 25 to 27, the electrode terminals of each battery cell 220 may be oriented perpendicular to the vertical direction, so that the busbars 222 connecting adjacent battery cells 220 are located at an intermediate depth in the cooling tank 210. Figure 25 is a top view of the cooling tank 210 with the lid removed.

[0163] (Seventh Embodiment) This embodiment will mainly describe the differences from the first to sixth embodiments. As shown in Figure 28, the battery cooling device 200 according to this embodiment has fins 260 provided on both the outer wall surface 211 and the inner wall surface 212 of the cooling tank 210, and a fan 261 is provided outside the cooling tank 210. In addition, microcapsule latent heat storage material is mixed into the insulating liquid 230 as a latent heat storage material 280. In this embodiment, filters 214 and 223 that restrict the movement of the latent heat storage material 280 are not provided in the cooling tank 210.

[0164] According to the above configuration, during flight (discharge) of the eVTOL100, each battery cell 220 and busbar 222 are cooled by heat storage by the insulating liquid 230 and latent heat storage material 280. In addition, forced air cooling from the outside of the cooling tank 210 by the fan 261 promotes heat dissipation from the inside to the outside of the cooling tank 210.

[0165] When the eVTOL100 is on the ground (during charging), as shown in Figure 29, the cooling tank 210 of the battery cooling device 200 is connected to the ground-based cryogenic cooling device 400. The insulating liquid 230 in the tank 410 of the cryogenic cooling device 400 is pre-cooled, and microcapsule latent heat storage material is mixed into the insulating liquid 230 as a latent heat storage material 280. Note that the control device 500 is omitted in Figure 29.

[0166] Then, the battery cooling device 200 and the low-temperature cooling device 400 are connected via valve fittings 240 and 250 to form a cooling circulation circuit 460. After this, the pre-cooled low-temperature insulating liquid 230 circulates through the cooling circulation circuit 460. This allows for rapid cooling of each battery cell 220 inside the cooling tank 210. When circulating the insulating liquid 230 through the cooling circulation circuit 460, the fan 261 of the battery cooling device 200 may be rotated to forcibly air-cool the cooling tank 210.

[0167] As an alternative cooling method, when the eVTOL 100 is on the ground (during charging), the battery cooling device 200 and the low-temperature cooling device 400 may be connected via valve fittings 240 and 250, and then the insulating liquid 230 inside the cooling tank 210 may be discharged via the discharge valve 450 of the piping 430 that constitutes the cooling circulation circuit 460. After this, the insulating liquid 230, which has been pre-cooled in the low-temperature cooling device 400, is filled from the low-temperature cooling device 400 into the battery cooling device 200. In this way, the insulating liquid 230 does not need to circulate through the cooling circulation circuit 460.

[0168] For example, after draining the insulating liquid 230 from the cooling tank 210, the low-temperature insulating liquid 230 from the low-temperature cooling device 400 is filled. After this, the insulating liquid 230 may be circulated to the cooling circulation circuit 460. Alternatively, the draining and filling of the insulating liquid 230 may be repeated. This allows each battery cell 220 in the cooling tank 210 to be rapidly cooled. The method of repeatedly draining and filling the insulating liquid 230 is particularly effective when the spacing 221 between adjacent battery cells 220 is narrow, that is, when the flow resistance of the insulating liquid 230 is large and the flow rate of insulating liquid 230 between battery cells 220 is small.

[0169] Alternatively, the insulating liquid 230 in the cooling tank 210 may be discharged through the discharge valve 450, while low-temperature insulating liquid 230 is supplied from the top of the cooling tank 210 via the valve fitting 240 at the top of the cooling tank 210. In this case, although it is not a circulation of the insulating liquid 230, low-temperature insulating liquid 230 can be constantly supplied to each battery cell 220, so heat generation during charging can be effectively suppressed. Then, by closing the discharge valve 450 near the end of charging, the inside of the cooling tank 210 can be filled with low-temperature insulating liquid 230. Of course, when circulating the insulating liquid 230 to the cooling circulation circuit 460, the fan 261 of the battery cooling device 200 may be rotated to forcibly air-cool the cooling tank 210.

[0170] When the insulating liquid 230 is discharged from the cooling tank 210 and then refilled with insulating liquid 230, it is sufficient to have at least one valve fitting in the cooling tank 210. In other words, both the discharge and refilling of the insulating liquid 230 can be done with a single valve fitting. Alternatively, multiple valve fittings may be provided in the cooling tank 210, such as two valve fittings for discharge and two valve fittings for refilling. Even when the insulating liquid 230 is circulated in the cooling circulation circuit 460, multiple valve fittings may be provided in the cooling tank 210.

[0171] As an alternative cooling method, as shown in Figure 30, the battery cooling device 200 may be equipped with piping 274, a three-way valve 272, and a pump 273 instead of the valve fitting 250. Oil may also be used as the insulating liquid 230.

[0172] In this case, during flight (discharge) of the eVTOL 100, each battery cell 220 and busbar 222 are cooled by heat storage using an insulating liquid 230 (oil) and a latent heat storage material 280. In addition, the cooling tank 210 is forcibly air-cooled by a fan 261. Furthermore, the oil is circulated inside the cooling tank 210 by a pump 273. This helps to equalize the temperature of each battery cell 220 and promote cooling.

[0173] As shown in Figure 31, when the eVTOL 100 is on the ground (during charging), the connection between piping 274 and piping 251 is disconnected by the three-way valve 272 of the cooling tank 210. In addition, the valve fitting 240 is connected to the piping 420 of the cryogenic cooling device 400, and the three-way valve 272 is connected to the piping 430 of the cryogenic cooling device 400. This constitutes the cooling circulation circuit 460. The insulating liquid 230 can be circulated through the cooling circulation circuit 460 as described above, or it can be discharged from the cooling tank 210 via the discharge valve 450 and then refilled with low-temperature insulating liquid 230 into the cooling tank 210.

[0174] As an alternative cooling method, as shown in Figure 32, a heat exchanger 275 may be connected to the piping 274 in the configuration of Figure 30. This further increases the external heat dissipation by the heat exchanger 275 during flight (discharge) of the eVTOL 100, thereby further improving the cooling performance of the battery cooling device 200.

[0175] As shown in Figure 33, when the eVTOL 100 is on the ground (during charging), the insulating liquid 230 may be circulated in the cooling circulation circuit 460 as described above. Alternatively, the insulating liquid 230 may be discharged from the cooling tank 210 via the discharge valve 450, and then the cooling tank 210 may be filled with low-temperature insulating liquid 230. When circulating the insulating liquid 230 in the cooling circulation circuit 460, the fan 261 of the battery cooling device 200 may be rotated to forcibly air-cool the cooling tank 210.

[0176] (Eighth embodiment) This embodiment will mainly describe the differences from the first to seventh embodiments. In this embodiment, the amount of insulating liquid 230 contained in the cooling tank 210 and its initial temperature are optimized according to the flight conditions of the eVTOL 100. That is, the amount and initial temperature of the insulating liquid 230 are adjusted according to the flight conditions of the eVTOL 100. The initial temperature is the temperature of the insulating liquid 230 when the injection of the insulating liquid 230 into the cooling tank 210 is completed.

[0177] Flight conditions include, for example, flight distance, flight time, flight altitude, flight route, flight speed, number of flights, passenger capacity, payload, weather conditions, weather along the flight route, and aircraft specifications. In other words, flight conditions are related to the load on the battery pack during flight.

[0178] The amount and initial temperature of the insulating liquid 230 are determined comprehensively from known flight conditions such as the flight path and flight conditions that can be obtained before takeoff, such as the weather at the time of flight. The amount and initial temperature of the insulating liquid 230 are determined, for example, by the control device 500 of the battery cooling system 300 before the next flight of the eVTOL 100. The amount and initial temperature of the insulating liquid 230 are determined, for example, before or after the landing of the eVTOL 100.

[0179] The amount of insulating liquid 230 and its initial temperature are calculated from the relationship between the flight conditions and the amount of insulating liquid 230 and its initial temperature. Alternatively, the amount of insulating liquid 230 and its initial temperature can be derived from a map showing the relationship between flight conditions, the amount of insulating liquid 230, and its initial temperature.

[0180] For example, the control device 500 calculates the required output and usage amount of each battery cell 220 from the flight conditions, and calculates the amount of heat generated by each battery cell 220 from the required output and usage amount. The control device 500 calculates the amount of insulating liquid 230 and the initial temperature required to store the heat generated by the battery below the allowable temperature of the battery cell 220. For example, the amount of heat generated by the battery can be calculated as: Heat generated by the battery = (Battery heat capacity + Amount of insulating liquid × Specific heat) × (Allowable temperature - Initial temperature).

[0181] The amount of insulating liquid 230 and its initial temperature may be calculated by a device other than the control device 500. In this case, the control device 500 acquires the data on the amount of insulating liquid 230 and its initial temperature calculated by the device other than the control device 500, and adjusts the amount of insulating liquid 230 and its initial temperature in the cooling tank 210 based on the acquired data.

[0182] The control unit 500 acquires the amount and initial temperature of the insulating liquid 230 in advance of the next flight of the eVTOL 100, based on the flight conditions. Then, when the eVTOL 100 is on the ground (during charging), the control unit 500 rapidly cools each battery cell 220 inside the cooling tank 210, and then optimizes the amount and initial temperature of the insulating liquid 230 contained in the cooling tank 210 according to the flight conditions of the eVTOL 100. Note that during the rapid cooling of the battery cells 220, the inside of the cooling tank 210 may be filled with low-temperature insulating liquid 230.

[0183] Here, the battery cooling device 200 has a liquid level gauge. The liquid level gauge is installed in the cooling tank 210 and detects the height of the liquid level of the insulating liquid 230. The liquid level gauge may employ either a contact method with the insulating liquid 230 or a non-contact method with the insulating liquid 230. The liquid level gauge outputs the measurement result to the control device 500.

[0184] The control device 500 adjusts the amount of insulating liquid 230 in the cooling tank 210 by controlling the pump 440 based on the measurement results of the liquid level gauge. This allows the control device 500 to control the amount of insulating liquid 230 contained in the cooling tank 210 to differ depending on the flight conditions of the eVTOL 100. For example, the control device 500 may set the amount of insulating liquid 230 to be less than the standard amount under the first flight conditions (low-load flight) and to be more than the standard amount under the second flight conditions (high-load flight).

[0185] The amount of insulating liquid 230 in the cooling tank 210 may also be measured by a flow sensor. The flow sensor is installed in the piping used to pump the insulating liquid 230 into the cooling tank 210. For example, the flow sensor is installed in the piping 251 of the battery cooling device 200 or in the piping 430 of the battery cooling system 300. The control device 500 controls the flow rate of the insulating liquid 230 pumped into the cooling tank 210 based on the signal from the flow sensor.

[0186] Figures 34 to 36 show the cases where the amount of insulating liquid 230 is optimized. Figure 34 shows the amount of insulating liquid 230 during low-load flight. Figure 35 shows the amount of insulating liquid 230 during medium-load flight. Figure 36 shows the amount of insulating liquid 230 during high-load flight.

[0187] As shown in Figure 34, when each battery cell 220 is under low load depending on the flight conditions, the liquid level 231 of the insulating liquid 230 is lower than, for example, the reference position in the cooling tank 210. In other words, less insulating liquid 230 is required. Therefore, when each battery cell 220 is under low load, the battery cooling device 200 can be made lighter.

[0188] As shown in Figure 35, when each battery cell 220 is under a moderate load depending on the flight conditions, the liquid level 231 of the insulating liquid 230 is, for example, near the reference position in the cooling tank 210. This makes it possible to reduce the amount of insulating liquid 230 and thus reduce weight while ensuring the cooling performance of the insulating liquid 230. Note that the liquid level 231 of the insulating liquid 230 may be located above or below the reference position in the cooling tank 210.

[0189] As shown in Figure 36, when each battery cell 220 is under high load depending on the flight conditions, the insulating liquid 230 immerses the entire battery case that constitutes the battery cell 220. This ensures that the insulating liquid 230 provides sufficient cooling for the battery cell 220. The position of the liquid level 231 of the insulating liquid 230 may be adjusted so that a portion of the battery case is exposed from the insulating liquid 230. As described above, the amount of insulating liquid 230 contained in the cooling tank 210 varies depending on the flight conditions of the eVTOL 100.

[0190] In the battery cooling device 200, each battery cell 220 is immersed in the insulating liquid 230, making it easy to adjust the amount of insulating liquid 230. Furthermore, when the amount of insulating liquid 230 in the cooling tank 210 is changed, the liquid level 231 of the insulating liquid 230 for the multiple battery cells 220 housed in the cooling tank 210 changes uniformly. That is, each battery cell 220 is uniformly immersed in the insulating liquid 230. Therefore, each battery cell 220 can be cooled uniformly.

[0191] In conventional technology, a cooler is placed in each battery cell. Therefore, even if the amount of coolant is changed, it is difficult to change the amount of coolant evenly for each battery cell 220. Consequently, there is variation in the cooling performance of each battery cell.

[0192] However, as in this embodiment, when the amount of insulating liquid 230 is changed on the ground according to the flight conditions, the liquid level 231 of the insulating liquid 230 for the multiple battery cells 220 housed in the cooling tank 210 changes uniformly, so that each battery cell 220 can be cooled uniformly.

[0193] Furthermore, when optimizing the amount of insulating liquid 230, the above embodiments can be combined as much as possible.

[0194] This disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of this disclosure, as follows.

[0195] For example, the opposing surfaces 227 of each battery cell 220 do not need to be parallel to the vertical direction; they may be tilted relative to the vertical direction. Even in this case, the insulating liquid 230 between adjacent battery cells 220 can move towards the ground due to gravity.

[0196] Alternatively, each battery cell 220 may be housed in the cooling tank 210 such that its opposing surface 227 is aligned in a direction perpendicular to the vertical direction. In other words, the opposing surfaces 227 of each battery cell 220 may be arranged to align in the horizontal direction. Of course, the opposing surfaces 227 of each battery cell 220 do not need to be parallel to the horizontal direction; they may be inclined with respect to the horizontal direction.

[0197] As the insulating liquid 230, a phase change material that solidifies at around the lower limit temperature of the battery cell 220 may be used. The phase change material is liquid in the normal operating temperature range of the battery cell 220 (approximately 10°C to 60°C) and absorbs heat from each battery cell 220. In special cases where the temperature approaches the lower limit of the normal operating temperature range of the battery cell 220, the liquid phase change material solidifies, i.e., releases latent heat. As a result, the temperature of the battery cell 220 can be maintained at the lower limit temperature of the operating temperature range without falling below it. Therefore, a temperature drop below the lower limit temperature of the battery cell 220 can be suppressed. In addition, the output of the battery cell 220 during landing can be prevented from decreasing.

[0198] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

[0199] The technical features of the battery cooling device and battery cooling system disclosed herein are as follows: (Item 1) A battery cooling device applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the aforementioned cooling tank, An insulating liquid (230) is provided in the cooling tank in a flowable manner, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, A battery cooling device, including a battery cooling device. (Item 2) The plurality of battery cells are electrically connected to each other by a busbar (222), The battery cooling device according to item 1, wherein at least a portion of the busbar is in direct contact with the insulating liquid. (Item 3) The cooling tank includes an outer wall surface (211) and an inner wall surface (212), Furthermore, the battery cooling device according to item 1 or 2, wherein the cooling tank is provided on either the outer wall surface, the inner wall surface, or both the outer wall surface and the inner wall surface, and includes fins (260) for dissipating heat from inside the cooling tank to the outside. (Item 4) The battery cooling device according to any one of items 1 to 3, wherein the cooling tank includes a fluidizing device (270) for flowing the insulating liquid. (Item 5) A battery cooling device according to any one of items 1 to 4, comprising a latent heat storage material (280) which is added to the insulating liquid and stores or releases heat by utilizing the inflow and outflow of latent heat associated with the phase change. (Item 6) The battery cooling device according to any one of items 1 to 5, wherein the insulating liquid is a non-flammable fluorine-based liquid. (Item 7) The battery cooling device according to any one of items 1 to 5, wherein the insulating liquid is oil. (Item 8) The plurality of battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, thereby contacting the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is The battery cell has a passage portion (291) through which the insulating liquid can flow in one direction parallel to the opposing surface, A support portion (292) that maintains the distance between adjacent battery cells by contacting the opposing surfaces of the battery cells, A battery cooling device as described in any one of items 1 through 7, including the one described in item 1 through 7. (Item 9) If we define the position of the center of the cooling tank in the vertical direction as the reference position, The battery cooling device according to any one of items 1 to 8, wherein the valve joint is located below the reference position in the cooling tank in the vertical direction. (Item 10) The battery cooling device according to any one of items 1 to 8, wherein the valve joint is provided in the cooling tank at a location where the insulating liquid is present. (Item 11) The battery cooling device according to any one of items 1 to 10, wherein the amount of insulating liquid contained in the cooling tank varies depending on the flight conditions of the electric aircraft. (Item 12) A battery cooling system applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the aforementioned cooling tank, An insulating liquid (230) is provided in the cooling tank in a flowable manner, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, A battery cooling device (200) including, The low-temperature cooling device for cooling and storing the insulating liquid, A control device (500) for controlling the low-temperature cooling device, Includes, The battery cooling device and the low-temperature cooling device are connected via the valve joint, thereby forming a cooling circulation circuit (460) in which the insulating liquid can circulate between the battery cooling device and the low-temperature cooling device. The control device is a battery cooling system that circulates the insulating liquid, which has been pre-cooled by the low-temperature cooling device, through the cooling circulation circuit. (Item 13) A battery cooling system applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the aforementioned cooling tank, An insulating liquid (230) is provided in the cooling tank in a flowable manner, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, A battery cooling device (200) including, The low-temperature cooling device for cooling and storing the insulating liquid, A control device (500) for controlling the low-temperature cooling device, Includes, The battery cooling device and the low-temperature cooling device are connected via the valve joint, thereby forming a cooling circulation circuit (460) in which the insulating liquid can circulate between the battery cooling device and the low-temperature cooling device. The control device discharges the insulating liquid from inside the cooling tank via the cooling circulation circuit, and thereafter fills the battery cooling device with the insulating liquid that has been pre-cooled by the low-temperature cooling device from the low-temperature cooling device, in a battery cooling system. (Item 14) The battery cooling system according to item 12 or 13, wherein the control device controls the amount of insulating liquid contained in the cooling tank to vary depending on the flight conditions of the electric aircraft.< / evtol>

Claims

1. A battery cooling device applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the cooling tank, An insulating liquid (230) is contained in the cooling tank in a flowable manner, immersing a plurality of the battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to and detached from a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, Includes, The valve joint allows the insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. The multiple battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, thereby contacting the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is The insulating liquid is flowable in one direction parallel to the opposing surface of the battery cell, and the passage portion (291) extends on the premise of the flow of the insulating liquid circulating between the low-temperature cooling device and the battery cell, A support portion (292) that maintains the distance between adjacent battery cells by contacting the opposing surfaces of the battery cells, Includes, A battery cooling device in which the spacer member is an offset fin, corrugated fin, wave fin, louver fin, extruded tube, inner fin tube, or a member having the passage portion and the support portion, wherein the spacer member may be formed from a metal material or a resin material.

2. The plurality of battery cells are electrically connected to each other by a busbar (222), The battery cooling device according to claim 1, wherein at least a portion of the busbar is in direct contact with the insulating liquid.

3. The cooling tank includes an outer wall surface (211) and an inner wall surface (212), Furthermore, the battery cooling device according to claim 1 or 2, wherein the cooling tank is provided on either the outer wall surface, the inner wall surface, or both the outer wall surface and the inner wall surface, and includes fins (260) for dissipating heat from inside the cooling tank to the outside.

4. The battery cooling apparatus according to claim 1 or 2, wherein the cooling tank includes a fluidizing device (270) for flowing the insulating liquid.

5. The battery cooling device according to claim 1 or 2, further comprising a latent heat storage material (280) which is added to the insulating liquid and stores or releases heat by utilizing the inflow and outflow of latent heat associated with the phase change.

6. The battery cooling device according to claim 1 or 2, wherein the insulating liquid is a non-flammable fluorine-based liquid.

7. The battery cooling device according to claim 1 or 2, wherein the insulating liquid is oil.

8. If we define the position of the center of the cooling tank in the vertical direction as the reference position, The battery cooling device according to claim 1 or 2, wherein the valve joint is located below the reference position in the cooling tank in the vertical direction.

9. The battery cooling device according to claim 1 or 2, wherein the valve joint is provided in the cooling tank at a location where the insulating liquid is present.

10. The battery cooling device according to claim 1 or 2, wherein the amount of insulating liquid contained in the cooling tank varies depending on the flight conditions of the electric aircraft.

11. A battery cooling system applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the cooling tank, An insulating liquid (230) is contained in the cooling tank in a flowable manner, immersing a plurality of the battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to and detached from a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, Includes, The valve joint allows the insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. The multiple battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, thereby contacting the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is The insulating liquid is flowable in one direction parallel to the opposing surface of the battery cell, and the passage portion (291) extends on the premise of the flow of the insulating liquid circulating between the low-temperature cooling device and the battery cell, A support portion (292) that maintains the distance between adjacent battery cells by contacting the opposing surfaces of the battery cells, Includes, The spacer member is an offset fin, corrugated fin, wave fin, louver fin, extruded tube, inner fin tube, or a member having the passage portion and the support portion, and the spacer member may be formed from a metal material or a resin material, in a battery cooling device (200), The low-temperature cooling device for cooling and storing the insulating liquid, A control device (500) for controlling the low-temperature cooling device, Includes, The battery cooling device and the low-temperature cooling device are connected via the valve joint, thereby forming a cooling circulation circuit (460) in which the insulating liquid can circulate between the battery cooling device and the low-temperature cooling device. The control device is a battery cooling system that circulates the insulating liquid, which has been pre-cooled by the low-temperature cooling device, through the cooling circulation circuit.

12. A battery cooling system applicable to an electric aircraft (100), Cooling tank (210), Multiple battery cells (220) housed in the cooling tank, An insulating liquid (230) is contained in the cooling tank in a flowable manner, immersing a plurality of the battery cells and absorbing heat from the plurality of battery cells, A valve joint (240, 250, 272) is provided in the cooling tank and is attached to and detached from a low-temperature cooling device (400) that can allow the insulating liquid inside the cooling tank to flow in and out, Includes, The valve joint allows the insulating liquid to flow in and out between the cooling tank and the low-temperature cooling device when the low-temperature cooling device is connected to the cooling tank. The multiple battery cells are arranged with a gap (221) between them, and each has a facing surface (227) that faces the adjacent battery cell. The device includes a spacer member (290) that is sandwiched between adjacent battery cells, thereby contacting the opposing surfaces of the adjacent battery cells, and capable of transferring heat from the battery cells transmitted through the opposing surfaces to the insulating liquid. The spacer member is The insulating liquid is flowable in one direction parallel to the opposing surface of the battery cell, and the passage portion (291) extends on the premise of the flow of the insulating liquid circulating between the low-temperature cooling device and the battery cell, A support portion (292) that maintains the distance between adjacent battery cells by contacting the opposing surfaces of the battery cells, Includes, The spacer member is an offset fin, corrugated fin, wave fin, louver fin, extruded tube, inner fin tube, or a member having the passage portion and the support portion, and the spacer member may be formed from a metal material or a resin material, in a battery cooling device (200), The low-temperature cooling device for cooling and storing the insulating liquid, A control device (500) for controlling the low-temperature cooling device, Includes, The battery cooling device and the low-temperature cooling device are connected via the valve joint, thereby forming a cooling circulation circuit (460) in which the insulating liquid can circulate between the battery cooling device and the low-temperature cooling device. The control device discharges the insulating liquid from inside the cooling tank via the cooling circulation circuit, and thereafter fills the battery cooling device with the insulating liquid that has been pre-cooled by the low-temperature cooling device from the low-temperature cooling device.

13. The battery cooling system according to claim 11 or 12, wherein the control device controls the amount of insulating liquid contained in the cooling tank to differ according to the flight conditions of the electric aircraft.

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