Battery cooling device and 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

Battery cooling device, battery cooling system CROSS-REFERENCE TO RELATED APPLICATIONS

[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.

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

[0003] A battery thermal management system applied to an electric flying vehicle has been proposed in, for example, Patent Document 1. The battery thermal management system includes a battery pack that combines a plurality of battery cells, a plurality of cooling plates, and a plurality of insulators.

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

[0005] The working fluid circulates inside the cooling plates, whereby each battery cell is cooled by the cooling plates, and heat from each battery cell is stored in the working fluid via the cooling plates.

[0006] Special Publication No. 2022-530619

[0007] However, in the conventional technology, the interfaces between the battery cells and the cooling plate and between the inner wall of the cooling plate and the working fluid make it difficult for heat to transfer from the battery cells to the working fluid, which reduces the cooling (heat storage) performance of each battery cell and the temperature uniformity performance of each battery cell in the battery pack.

[0008] In particular, when a battery pack is applied to an electric aircraft, the temperature of each battery cell rises rapidly in a short period of time due to the large current flowing through each battery cell during takeoff and landing. Since the battery cells disclosed in Patent Document 1 are arranged in large numbers in two dimensions, temperature distribution is likely to occur among the battery cells depending on their location. As a result, battery cells with high temperatures deteriorate more rapidly than other battery cells.

[0009] Therefore, it is desirable to lower the temperature of the high-temperature battery cells to the same temperature as the other battery cells. It is also desirable to equalize the temperature of each battery cell to reduce the difference in output and deterioration among the battery cells. Furthermore, it is desirable to rapidly cool each battery cell on the ground after landing.

[0010] In view of the above, the present disclosure aims to provide a structure for a battery cooling device or battery cooling system applied to an electric flying vehicle that can lower the temperature of a high-temperature battery cell below the temperature of other battery cells while achieving uniform temperature distribution among multiple battery cells.

[0011] In order to achieve the above object, according to a first aspect of the present disclosure, a battery cooling device applicable to an electric flying vehicle includes: a cooling tank; a plurality of battery cells contained in the cooling tank; an insulating liquid that is flowably contained in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; and a valve fitting that is provided in the cooling tank and to which a low-temperature cooling device that can flow in and out of the insulating liquid inside the cooling tank is detachably attached.

[0012] According to a second aspect of the present disclosure, there is provided a battery cooling system applicable to an electric flying vehicle, the battery cooling system including: a cooling tank; a plurality of battery cells contained in the cooling tank; an insulating liquid that is flowably contained in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve fitting that is provided in the cooling tank and to which a low-temperature cooling device that can flow in and out of the insulating liquid inside the cooling tank is detachably attached; a low-temperature cooling device that cools and stores the insulating liquid; and a control device that controls the low-temperature cooling device, wherein the battery cooling device and the low-temperature cooling device are connected via the valve fitting to form a cooling circulation circuit that can circulate the insulating liquid between the battery cooling device and the low-temperature cooling device, and the control device circulates the insulating liquid that has been previously cooled in the low-temperature cooling device through the cooling circulation circuit.

[0013] According to a third aspect of the present disclosure, there is provided a battery cooling system applicable to an electric flying vehicle, comprising: a cooling tank; a plurality of battery cells contained in the cooling tank; an insulating liquid that is flowably contained in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve fitting that is provided in the cooling tank and to which a low-temperature cooling device that can flow in and out of the insulating liquid inside the cooling tank is detachably attached; a low-temperature cooling device that cools and stores the insulating liquid; and a control device that controls the low-temperature cooling device, wherein the battery cooling device and the low-temperature cooling device are connected via the valve fitting to form a cooling circulation circuit that can circulate the insulating liquid between the battery cooling device and the low-temperature cooling device, and the control device discharges the insulating liquid inside the cooling tank via the cooling circulation circuit, and then fills the insulating liquid that has been pre-cooled in the low-temperature cooling device from the low-temperature cooling device into the battery cooling device.

[0014] With this, the heat of each battery cell is absorbed by the insulating liquid, so that the temperature of the high-temperature battery cell can be lowered below the temperature of the other battery cells, while suppressing the temperature rise of each battery cell.

[0015] Furthermore, by immersing multiple battery cells in the insulating liquid inside the cooling tank, the insulating liquid flows (convects), which reduces temperature variations among the battery cells and makes the temperature uniform.

[0016] Furthermore, after the electric aircraft lands, a low-temperature cooling device can be connected to the valve joint to forcibly cool the insulating liquid and each battery cell, thereby rapidly lowering the temperature of each battery cell and insulating liquid inside the cooling tank.

[0017] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a diagram showing a schematic configuration of an eVTOL according to a first embodiment, Fig. 2 is a diagram showing a battery cooling system, Fig. 3 is a diagram showing a battery cooling device and a low-temperature cooling device after takeoff, Fig. 4 is a diagram showing changes in battery output and battery temperature from takeoff to landing of an eVTOL, Fig. 5 is a cross-sectional view of a battery cooling device according to a second embodiment, Fig. 6 is a cross-sectional view of a modified example, Fig. 7 is a cross-sectional view of a modified example, Fig. 8 is a cross-sectional view of a modified example, and Fig. 9 is a cross-sectional view of a battery cooling device according to a third embodiment. 10 is a cross-sectional view showing a modified example, FIG. 11 is a cross-sectional view showing a modified example, FIG. 12 is a cross-sectional view showing a battery cooling device according to a fourth embodiment, FIG. 13 is a cross-sectional view showing a modified example, FIG. 14 is a cross-sectional view showing a modified example, FIG. 15 is a cross-sectional view showing a modified example, FIG. 16 is a top view of a battery cooling device according to a fifth embodiment, FIG. 17 is a cross-sectional view taken along XVII-XVII in FIG. 16, FIG. 18 is a perspective view of an offset fin which is an example of a spacer member, and FIG. 19 is a perspective view of a corrugated fin which is an example of a spacer member. 20 is a perspective view of a wave fin, which is an example of a spacer member; FIG. 21 is a perspective view of a louver fin, which is an example of a spacer member; FIG. 22 is a top view of a battery cell including an extruded tube, which is an example of a spacer member; FIG. 23 is a top view of a battery cell including an inner fin tube, which is an example of a spacer member; FIG. 24 is a cross-sectional view showing a battery cooling device according to a sixth embodiment; FIG. 25 is a top view showing a modified example; FIG. 26 is a cross-sectional view taken along line XXVI-XXVI of FIG. 25; FIG. 28 is a cross-sectional view showing a battery cooling device according to the seventh embodiment, FIG. 29 is a diagram showing a battery cooling system on the ground (charging), FIG. 30 is a cross-sectional view showing a battery cooling device applied to another cooling method, FIG. 31 is a diagram showing a battery cooling system including the battery cooling device of FIG. 30, FIG. 32 is a cross-sectional view showing a battery cooling device applied to another cooling method, FIG. 33 is a diagram showing a battery cooling system including the battery cooling device of FIG. 32, and FIG. 34 is a cross-sectional view showing a battery cooling device according to the eighth embodiment,FIG. 35 is a cross-sectional view showing a battery cooling device according to an eighth embodiment, and FIG. 36 is a cross-sectional view showing a battery cooling device according to the eighth embodiment.

[0018] Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to matters described in the preceding embodiment will be assigned the same reference numerals, and duplicated explanations may be omitted. In each embodiment, when only a part of the configuration is described, the other previously described embodiments may be applied to the other parts of the configuration.

[0019] In each embodiment, it is possible to combine parts that are specifically expressly possible to combine with each other. Furthermore, even if it is not expressly expressly possible to combine, it is also possible to partially combine embodiments with each other, embodiments with modified examples, and modified examples with each other, as long as there are no particular problems with the combination.

[0020] First Embodiment A battery cooling device according to this embodiment is mounted on an electric flying object. The electric flying object is capable of flying by being driven by a rotating electric machine.

[0021] Examples of electric flying vehicles include electric vertical take-off and landing aircraft (eVTOL), electric short take-off and landing aircraft (eSTOL), drones, etc. 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. In the following, an example in which a battery cooling device is installed in an eVTOL will be described.

[0022] <eVTOL> As shown in FIG. 1 , an eVTOL 100 according to the present embodiment includes, as an example, an aircraft body 110 , fixed wings 120 , rotary wings 130 , a lift control mechanism 140 , a battery cooling device 200 , an EPU 150 , a BMS 160 , and an ECU 170 .

[0023] The aircraft main body 110 is the fuselage of the aircraft. The aircraft main body 110 has a shape that extends in the front-to-rear direction. The aircraft main body 110 has a passenger compartment for passengers and / or a luggage compartment for carrying luggage.

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

[0025] A plurality of rotors 130 are provided on the airframe. At least some of the plurality of rotors 130 may be provided on the fixed wing 120. At least some of the plurality of rotors 130 may be provided on the airframe main body 110. The number of rotors 130 provided on the eVTOL 100 is not particularly limited. As an example, a plurality of rotors 130 are provided on each of the airframe main body 110 and the main wing 121. The eVTOL 100 is provided with six rotors 130.

[0026] The rotor 130 may be referred to as a rotor, a propeller, a fan, etc. The rotor 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. A plurality of blades 131 extend radially around the axis of the shaft 132. The shaft 132 is the rotation axis of the rotor 130, and is driven to rotate by the motor of the EPU 150.

[0027] Rotor 130 generates thrust by rotation. The thrust acts on eVTOL 100 primarily as rotational lift during takeoff and landing. Rotor 130 primarily provides rotational lift during takeoff and landing. Rotational lift is lift generated by the rotation of rotor 130. During takeoff and landing, rotor 130 may provide only rotational lift, or may provide forward thrust in addition to rotational lift. Rotor 130 provides rotational lift during eVTOL 100 hovering.

[0028] The propulsive force acts primarily as thrust on eVTOL 100 during cruising of eVTOL 100. Rotor 130 primarily provides thrust during cruising. During cruising, rotor 130 may provide thrust alone or may provide lift in addition to thrust.

[0029] The lift adjustment mechanism 140 adjusts the gliding lift of the fixed wing 120. The lift adjustment mechanism 140 increases or decreases the gliding lift generated by the fixed wing 120. The lift adjustment mechanism 140 adjusts the gliding lift by adjusting at least one of the surface area, angle of attack (AOA), camber (wing curvature), stall AOA, and wing speed of the fixed wing 120, for example. 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 130. The tilt mechanism 141, together with a motor, an inverter, and the like 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 each rotor 130. The tilt mechanism 141 adjusts the tilt angle of the rotor 130 by adjusting the relative inclination of the rotor 130 with respect to the airframe.

[0031] During takeoff and landing, 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 generated by the rotation of each rotor 130 acts on eVTOL 100 primarily as rotational lift. This allows eVTOL 100 to take off and land in a short distance or in a vertical direction. In FIG. 1 , the vertical direction is perpendicular to the plane of the page.

[0032] During cruising, 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 propulsive force generated by the rotation of each rotor 130 acts primarily as thrust on eVTOL 100. Therefore, eVTOL 100 can move forward using the forward thrust generated by the rotation of each rotor 130 while obtaining gliding lift from fixed wing 120. Furthermore, gliding lift can be adjusted by changing the wing speed using thrust.

[0033] Although the example in which the tilt mechanisms 141 are provided individually for the rotors 130 has been described, the present invention is not limited to this. For example, the tilt angles of multiple rotors 130 arranged side by side may be controlled by a common tilt mechanism. Alternatively, the rotors 130 may be integrated with a portion of the wing section, and the portion of the wing section and the rotors 130 may be displaced integrally by the tilt mechanism.

[0034] The flap 142 is a movable wing piece and is provided on the fixed wing 120. The flap 142, together with a motor, an inverter, and the like that drive the flap 142, constitutes a flap adjustment device. The flap 142 is sometimes referred to as a high-lift device. As an example, a plurality of flaps 142 are provided on the trailing edge of the main wing 121. Each of the plurality of flaps 142 is provided with a motor and an inverter. The flap 142 may be provided on the tail 122 in addition to the main wing 121. The flap 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 lower position, the gliding lift acting on the main wing 121 increases. In addition, by moving the flaps 142 in a direction that protrudes from the main wing 121, it is possible to further increase the gliding lift.

[0036] The lift adjustment mechanism 140 is not limited to the tilt mechanism 141 and the flap 142 described above. A tilt mechanism that adjusts the relative inclination of the fixed wing 120 with respect to the aircraft body 110 may be employed as the lift adjustment mechanism 140. In this case, the angle of attack of the fixed wing 120 can be adjusted. A rotor for thrust provided separately from the rotor 130 may be employed as the lift adjustment mechanism 140. In this case, the wing speed can be adjusted. Furthermore, by providing a rotor for thrust, it is possible to dedicate the rotor 130 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, angle of attachment, etc. of the fixed wing 120. A high-lift device other than the flap 142, such as a slat, may 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. This allows for increased lift without stalling up to a higher angle of attack. In other words, the stall AOA can be delayed.

[0038] The battery cooling device 200 has a plurality of battery cells (described later) and is 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, the ECU 170, the tilt adjustment device, and the flap adjustment device. Each battery cell also supplies power to auxiliary equipment (not shown), such as an air conditioner.

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

[0040] Here, the multiple battery cells may include, for example, tens or hundreds of cells, and therefore the battery cooling device 200 is heavy. Therefore, by arranging each battery cooling device 200 at two locations on each side of the main wing 121, the balance of the airframe main body 110 can be maintained. Of course, the battery cooling device 200 may also be arranged in the airframe main body 110.

[0041] The EPU 150 has a motor and an inverter, and rotates the rotors 130 that provide propulsive force to the eVTOL 100. EPU is an abbreviation for Electric Propulsion Unit. As an example, the number of EPUs 150 provided is the same as the number of rotors 130. In other words, the eVTOL 100 includes six EPUs 150. The EPUs 150 and the rotors 130 are connected one-to-one. Alternatively, two or more rotors 130 may be connected to one EPU 150 via a gearbox.

[0042] The BMS 160 monitors the state of each battery pack of the battery cooling device 200. BMS is an abbreviation for Battery Management System. For example, one BMS 160 is provided for each battery cooling device 200. By monitoring the state of each battery pack of each of the multiple battery cooling devices 200, the BMS 160 may, for example, predict an abnormality in each battery cooling device 200 or may detect an abnormality in each battery cooling device 200.

[0043] ECU 170 controls the flight of eVTOL 100. ECU is an abbreviation for Electronic Control Unit. ECU 170 controls the flight of eVTOL 100 in a flight state according to operation by a pilot as an operator, remote operation by an operator, or control by a control system. ECU 170 executes flight control based on detection results from BMS 160 and various sensors. ECU 170 controls the drive of, for example, the motor of EPU 150, the motor of the tilt adjustment device, and the motor of the flap adjustment device. ECU 170 may also execute control of auxiliary equipment.

[0044] 2, the battery cooling system 300 includes a battery cooling device 200, a low-temperature cooling device 400, and a control device 500. The up-and-down direction when the eVTOL 100 is stationary on the ground is referred to as the vertical direction. In the vertical direction, the top side refers to the sky and the bottom side refers to the ground.

[0045] The battery cooling device 200 includes a cooling tank 210 , a plurality of battery cells 220 , an insulating liquid 230 , and valve joints 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, and also has 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 a lid, for example, on the upper side in the vertical direction. The lid can be attached and detached to the other parts. This allows multiple battery cells 220 to be placed in and removed from the space 213 of the cooling tank 210. The interior of the cooling tank 210 may be sealed, or it may not be completely sealed.

[0048] The battery cell 220 is a secondary battery that generates an electromotive force through a chemical reaction. The battery cell 220 is, for example, a lithium-ion secondary battery, a nickel-metal hydride secondary battery, an organic radical battery, etc. 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] The multiple battery cells 220 have a common structure. There are no particular limitations on the number or arrangement of the multiple battery cells 220. The 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 electrically connected structure of the multiple battery cells 220 is sometimes called an assembled battery. An assembled battery is what is known as a battery pack. The multiple battery cells 220 are housed in a space 213 in the cooling tank 210.

[0050] The battery cell 220 has a power generating element and a battery case that houses the power generating element. The battery case provides the outer shell of the battery cell 220. The battery case is formed using, for example, a metal material. The shape of the battery cell 220, i.e., the battery case, is not particularly limited. For example, a cylindrical shape, a rectangular shape, or the like can be adopted. As an example, the battery cell 220 of this embodiment has a rectangular shape, specifically a thin, flat 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 side surfaces. The top surface is the surface facing upward in the vertical direction. The bottom surface is the surface opposite the top surface in the vertical direction and faces the ground. The side surface is a surface connecting the top surface and the bottom surface and running along the vertical direction.

[0052] The plurality of battery cells 220 are arranged side by side in a direction perpendicular to the top-bottom direction, with adjacent battery cells 220 arranged with a gap 221 therebetween. Each of the battery cells 220 has two electrode terminals.

[0053] One electrode terminal is electrically connected to the positive electrode of the battery cell 220. This electrode terminal may be referred to as a positive electrode terminal, a P terminal, etc. The other electrode terminal is electrically connected to the negative electrode of the battery cell 220. This other electrode terminal may be referred to as a negative electrode terminal, an N terminal, etc. The electrode terminal may be referred to as a current collecting tab.

[0054] The battery cells 220 are arranged so that their upper surfaces are positioned at approximately the same height in the vertical direction. The battery cells 220 are fixed in their relative positions by a fixing member (not shown). The fixing member may be, for example, a case or a restraining member such as a belt-like band.

[0055] In the above-described arrangement, the electrode terminals of adjacent battery cells 220 are electrically connected to each other by a bus bar 222, which is a wiring member. In other words, the bus bar 222 connects the plurality of battery cells 220 in series.

[0056] Two bus bars 222, one for the positive electrode and one for the negative electrode, protrude from a space 213 of the cooling tank 210 to the outside of the cooling tank 210. If the cooling tank 210 is made of a metal material, an insulating part such as an insulating seal material is disposed in the portion of the cooling tank 210 through which the bus bar 222 passes, thereby achieving electrical insulation between the cooling tank 210 and the bus bar 222. Note that one of the two bus bars is visible in FIG. 2 . The insulating part is also omitted from FIG. 2 .

[0057] The insulating liquid 230 is a heat transfer medium that is flowably accommodated 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 provided in the space 213 of the cooling tank 210 so that at least a portion of the bus bar 222 is in direct contact with the insulating liquid 230.

[0058] The insulating liquid 230 is provided in the cooling tank 210 so that air remains in the upper part of the space 213 of the cooling tank 210. This makes it possible to prevent 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] For example, a non-flammable fluorine-based liquid can be used as the insulating liquid 230. Non-flammable means that the substance or object does not burn and is not likely to spread due to sparks or heat, and also means that it is non-flammable. The non-flammable fluorine-based insulating liquid 230 can suppress thermal chain reactions when the battery cell 220 experiences thermal runaway, or can even prevent thermal chain reactions altogether. In other words, the fluorine-based insulating liquid 230 has the advantage of being highly safe.

[0060] The boiling point of the non-flammable fluorine-based insulating liquid 230 is, 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, thereby suppressing the temperature rise of the battery cell 220 that has gone into thermal runaway. Furthermore, thermal chain reaction of the battery cell 220 can be suppressed and prevented.

[0061] If the boiling point of the insulating liquid 230 is low, for example, 100°C, the abnormally heated battery cells 220 can be boiled and cooled at a low temperature, and the 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, 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, Asahiklin (registered trademark) manufactured by AGC, Opteon (registered trademark) manufactured by Chemours, etc. can be used.

[0063] Oil can be used as another example of the insulating liquid 230. Oil has low volatility, so there is less leakage from the cooling tank 210 to the outside, and it is also inexpensive.

[0064] As the oil, for example, SPECTRASYN (registered trademark) from ExxonMobil Corporation, SYNFLUID (registered trademark) from Chevron Phillips Chemical Company, and MIVOLT (registered trademark) from M&I Materials, Inc. Also, as other oil, for example, AmpCool from Engineered Fluids, Inc. and silicone oil from Shin-Etsu Chemical Co., Ltd. can be used.

[0065] The valve joints 240 and 250 are connection parts for connecting and disconnecting the cryogenic cooling device 400. That is, the cooling tank 210 is connected and disconnected to the cryogenic cooling device 400 via the valve joints 240 and 250. The valve joints 240 and 250 allow the insulating liquid 230 to pass through when connected to the cryogenic cooling device 400, but block the passage of the insulating liquid 230 when not connected to the cryogenic cooling device 400.

[0066] For example, the valve fittings 240, 250 may be manually switched to an open state after the cryogenic cooling device 400 is connected, or may be manually switched to a closed state before the cryogenic cooling device 400 is disconnected, or may be mechanically switched to an open state when the cryogenic cooling device 400 is connected to the valve fittings 240, 250, or may be mechanically switched to a closed state when the cryogenic cooling device 400 is disconnected from the valve fittings 240, 250.

[0067] Here, the center position of the cooling tank 210 in the vertical direction is defined as the reference position. In this embodiment, one valve joint 240 is connected to a pipe 241 provided in the cooling tank 210 above the reference position. The other valve joint 250 is connected to a pipe 251 provided in the cooling tank 210 below the reference position. As a result, for example, when the insulating liquid 230 inside the cooling tank 210 is discharged to the outside via the valve joint 250 provided 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, the insulating liquid 230 located above the valve joint 250 in the vertical direction can be discharged to the outside.

[0068] Both valve joints 240, 250 may be provided below the reference position in the cooling tank 210 in the vertical direction. Alternatively, both valve joints 240, 250 may be provided above the reference position in the cooling tank 210 in the vertical direction. In other words, it is sufficient that the valve joints 240, 250 are provided at positions in the cooling tank 210 where the insulating liquid 230 is present. By displacing the valve joints 240, 250 vertically or horizontally, it is possible to discharge more insulating liquid 230 from the cooling layer 210 and circulate with less stagnation (portions that do not flow). Furthermore, each valve joint 240, 250 may be installed directly in the cooling tank 210 without using each pipe 241, 251.

[0069] The low-temperature cooling device 400 is a device that cools and stores the insulating liquid 230. The low-temperature cooling device 400 is also a device that is connected to the valve joints 240 and 250 of the cooling tank 210, thereby allowing the insulating liquid 230 inside the cooling tank 210 to flow in and out.

[0070] The low-temperature cooling device 400 includes a tank 410 that stores the insulating liquid 230, pipes 420 and 430 connected to the tank 410, and a pump 440 that pressure-feeds the insulating liquid 230 in the tank 410 to the pipe 430. Although not shown, the low-temperature cooling device 400 also includes cooling equipment that cools and keeps the insulating liquid 230 in the tank 410 warm.

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

[0072] The other pipe 430 may be provided with a discharge valve 450 for discharging the high-temperature insulating liquid 230 in the cooling tank 210. This allows the high-temperature insulating liquid 230 inside the cooling tank 210 to be quickly discharged. Of course, the discharge valve 450 does not have to be provided on the other pipe 430. If the insulating liquid 230 is simply circulated through the cooling circulation circuit 460, the discharge valve 450 is not necessary.

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

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

[0075] Cryogenic cooling device 400 may be connected to cooling tank 210 simultaneously with the landing of eVTOL 100. Cryogenic cooling device 400 may be detached from cooling tank 210 simultaneously with the takeoff of 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 rotation speed (pumping capacity) of the pump 440 and the cooling temperature of the cooling unit. The control device 500 is composed 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 a control program stored in the ROM.

[0077] When 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 be used to control multiple battery cooling devices 200.

[0078] <Cooling Method> Next, a description will be given of a cooling method for each battery cell 220. As shown in Fig. 3, when eVTOL 100 takes off, cruises, and lands, heat from each battery cell 220 is stored in insulating liquid 230 in cooling tank 210. This cools each battery cell 220.

[0079] On the other hand, after the eVTOL 100 lands, each battery cooling device 200 mounted on the eVTOL 100 is connected to a low-temperature cooling device 400 as shown in Figure 2. This forms a cooling circulation circuit 460 between the battery cooling device 200 and the low-temperature cooling device 400.

[0080] The control device 500 causes the pump 440 to circulate the insulating liquid 230, which has been pre-cooled in the low-temperature cooling device 400, through the cooling circulation circuit 460. For example, the low-temperature insulating liquid 230 is caused to flow into the cooling tank 210 through a valve joint 250 provided 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 through a valve joint 240 provided at the top of the cooling tank 210. In this case, the pump 440 is controlled to pump the low-temperature insulating liquid 230 through the piping 430. By circulating the insulating liquid 230 through the cooling circulation circuit 460 in this way, the battery cells 220 inside the cooling tank 210 are rapidly cooled.

[0081] Alternatively, the low-temperature insulating liquid 230 may be introduced into the cooling tank 210 via a valve joint 240 provided 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 joint 250 provided 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 pipe 420.

[0082] 4 shows an example of the simplest flight pattern from takeoff to landing for the eVTOL 100. Note that the flight patterns of electric flying vehicles other than the eVTOL 100 are similar to those of the eVTOL 100.

[0083] The period from time T10 to time T11 is referred to as the takeoff period, takeoff time, departure period, departure time, etc. Hereinafter, the period from time T10 to time T11 is referred to as takeoff time. Takeoff time refers to the ascent of eVTOL 100 from a landed state to a cruising altitude. 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. Hereinafter, the period from time T12 to time T13 is referred to as landing time. Landing time refers to the operation of eVTOL 100 from a cruising altitude at the destination to landing on the ground. For convenience, in FIG. 4, the required power, i.e., output, is assumed to be constant throughout almost the entire range of each period.

[0084] The eVTOL 100 ascends from the takeoff point to the altitude of the cruise start point during the period from time T10 to time T11. The eVTOL 100 cruises at a predetermined altitude during the period from time T11 to time T12. The eVTOL 100 descends from the altitude of the end point of time T12 to the landing point during the period from time T12 to time T13.

[0085] The movement of eVTOL 100 includes a primarily horizontal component during cruising, and a primarily vertical component during takeoff and landing. During takeoff and landing, when movement occurs in the vertical direction, high power is required to drive rotor 130 of eVTOL 100 for a predetermined continuous period of time.

[0086] This high output places a heavy load on the battery cells 220 and EPU 150, which are driving devices for driving the rotor 130. For example, each battery cell 220 generates heat, and its temperature rises. This is because the heat generated by each battery cell 220 is proportional to the output.

[0087] After the eVTOL 100 lands, each battery cell 220 is charged on the ground. When charging of each battery cell 220 is complete, the eVTOL 100 takes off again and begins cruising.

[0088] The battery temperature of each battery cell 220 changes as follows when the eVTOL 100 is in flight (discharging) and on the ground (charging). First, at takeoff, the battery temperature of each battery cell 220 rises rapidly. During cruising, the battery output required is not as high as during takeoff, so the battery temperature of each battery cell 220 rises gradually. During landing, the battery output required is similar to that required during takeoff, so the battery temperature of each battery cell 220 rises rapidly.

[0089] During the flight (discharge) period from time T10 to time T13, when the eVTOL 100 takes off and lands, the insulating liquid 230 in the battery cooling device 200 stores and cools the heat of each battery cell 220. This suppresses the temperature rise of the high-power battery cells 220 (heat storage and cooling), while transferring heat to the other low-power (low-temperature) battery cells 220 via the insulating liquid 230, further reducing the temperature of the high-temperature battery cells 220 and increasing 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, it is possible to prevent each battery cell 220 from exceeding the 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 becoming too hot, i.e., causing safety concerns, and thus affecting the performance (safety) of the entire battery pack. For example, even if many other battery cells 220 still have a margin up to their upper temperature limit, if a specific battery cell 220 is too hot, the remaining flight time of the entire battery pack may be limited, and an emergency response such as transitioning to an emergency landing pattern may become necessary. However, by being able to lower the temperature of the hot battery cell 220, it becomes possible to avoid emergency response during flight.

[0091] The period from time T13 to time T16 is a ground (charging) period during which each battery cell 220 is charged on the ground and subjected to high-performance cooling of 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 through the cooling circulation circuit 460, causing the battery temperature to drop rapidly.

[0092] Furthermore, between time T13 and time T14, the bus bar 222 of the battery cooling device 200 is connected to the charging device. When the battery cooling device 200 is connected to the low-temperature cooling device 400, the bus bar 222 of the battery cooling device 200 may 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 from 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, and the battery temperature decreases gradually. When charging of each battery cell 220 is completed at time T15, each battery cell 220 and bus bar 222 no longer generates heat, and the battery temperature decreases 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. After time T16, the flight (discharging) and ground (charging) from time T10 to time T16 are 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 the insulating liquid 230. Furthermore, the cooling tank 210 is provided with valve joints 240, 250 that allow the insulating liquid 230 to flow inside the cooling tank 210 and that allow the low-temperature cooling device 400 outside the cooling tank 210 to be attached and detached.

[0095] As a result, during takeoff, cruising, and landing of the eVTOL 100, 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 temperature rise and temperature distribution in each battery cell 220. Furthermore, by immersing multiple battery cells 220 in the insulating liquid 230 in one cooling tank 210, the insulating liquid 230 flows (convects), thereby making it possible to uniformly temperature the multiple battery cells 220. Therefore, it is possible to lower the temperature of the battery cell 220 with the highest temperature among all the battery cells 220, and ultimately to uniformly temperature all the battery cells 220 (uniform temperature).

[0096] Furthermore, when the eVTOL 100 is on the ground, particularly 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 joints 240, 250 of the cooling tank 210 to circulate the insulating liquid 230 through the cooling circulation circuit 460. This allows for forced cooling of each battery cell 220 in the cooling tank 210. Therefore, the temperature of each battery cell 220 can be lowered while the battery cell 220 is being charged.

[0097] Furthermore, instead of having a cooler for each of the plurality of battery cells 220, i.e., instead of having a plurality of coolers for all of the battery cells 220, all of the battery cells 220 can be cooled by one cooling tank 210. Therefore, the weight of the battery cooling device 200 does not increase, and it is possible to avoid an increase in size.

[0098] In the battery cooling device 200 of this embodiment, at least a portion of the bus bar 222 is immersed in the insulating liquid 230. This allows the temperature of the bus bar 222 to be lowered. Furthermore, heat can be absorbed from the inside of each battery cell 220 into the insulating liquid 230 via the bus bar 222. This allows the temperature distribution within each battery cell 220 to be reduced.

[0099] Second Embodiment In this embodiment, differences from the first embodiment will be mainly described. As shown in Fig. 5, the cooling tank 210 has fins 260. The fins 260 have the function of radiating heat from inside the cooling tank 210 to the outside. The fins 260 not only radiate heat but 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. Note that, as shown in Figures 7 and 8 described below, 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 portions of the outer wall surface 211 and the inner wall surface 212 of the cooling tank 210 that correspond to the range where the insulating liquid 230 is present.

[0101] The fins 260 may be provided in an area 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 formed integrally with the cooling bath 210. The fins 260 may be prepared separately from the cooling bath 210 and then joined to the cooling bath 210 to be integrated therewith.

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

[0104] Alternatively, when the cooling tank 210 is made of a resin such as CFRP, the fins 260 are formed integrally with the cooling tank 210 by a method such as injection molding or extrusion. When the resin cooling tank 210 and the resin fins 260 are prepared as separate bodies, the fins 260 are joined to the cooling tank 210 by a method such as adhesion or welding. When the fins 260 are made of a 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 an integrated structure, or the metal fins 260 may be joined to the resin cooling tank 210 to form an integrated structure.

[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. This makes it possible to suppress temperature increases in each battery cell 220. Furthermore, the fins 260 also function as ribs in the cooling tank 210, improving the strength of the cooling tank 210. As a result, the weight of the cooling tank 210 can be reduced.

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

[0108] 6 , a fan 261 for promoting heat dissipation from the cooling tank 210 may be installed next to the cooling tank 210. The fan 261 may be fixed to the cooling tank 210 via a separate part, or may be fixed to the internal structure of the main wing 121 of the eVTOL 100. This allows for forced airflow to be directed at the fins 260 of the cooling tank 210, further promoting heat dissipation from the cooling tank 210.

[0109] The fan 261 is controlled by, for example, the BMS 160. Of course, the fan 261 may be controlled by a control device different from the BMS 160. For example, the fan 261 may be controlled by a device dedicated to the fan 261. Alternatively, the fan 261 may be controlled by another control device mounted on the eVTOL 100.

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

[0111] As a modified example, as shown in Fig. 7, the fins 260 may be provided only on the outer wall surface 211 of the cooling tank 210. Also, as shown in Fig. 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 among the surfaces constituting the cooling tank 210, or may be provided only on a specific inner wall surface 212, or may be provided on both specific outer wall surface 211 and inner wall surface 212. In other words, in one cooling tank 210, the fins 260 may be provided only on the outer wall surface 211, only on the inner wall surface 212, or on both the outer wall surface 211 and the inner wall surface 212, all of which may be mixed together.

[0113] Third Embodiment In this embodiment, differences from the first and second embodiments will be mainly described. As shown in Fig. 9, the cooling tank 210 includes a flow device 270 for flowing the insulating liquid 230. In this embodiment, the flow device 270 is a stirring device 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 disposed, for example, at the bottom inside the cooling tank 210. The agitator blade rotates so as to send the insulating liquid 230 from the bottom to the top of the cooling tank 210.

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

[0116] According to the above configuration, the agitator 271 moves a portion of the insulating liquid 230 from the bottom to the top of the cooling tank 210, and the insulating liquid 230 located away from the agitator 271 moves from the top to the bottom of the cooling tank 210. That is, the insulating liquid 230 is agitated inside the cooling tank 210. This improves the cooling performance of the cooling tank 210 and promotes uniform temperature distribution of each battery cell 220.

[0117] 9, the cooling performance and temperature uniformity performance can be improved by combining the fins 260 and the fan 261 with the agitator 271. Of course, the cooling tank 210 may be provided with only the agitator 271 without the fins 260 and the fan 261. Furthermore, the agitator 271 is not limited to being located at the bottom of the cooling tank 210, and may be located anywhere as long as it can generate a flow in the insulating liquid 230. Furthermore, the number of agitators 271 is not limited to one, and multiple agitators 271 may be provided in the cooling tank 210.

[0118] 10 , the flow device 270 may be configured by a pipe 241, a pipe 251, a three-way valve 272, a pump 273, and a pipe 274. The three-way valve 272 and the pump 273 are connected to a pipe 251 provided at the bottom of the cooling tank 210, and the pipe 241 provided at the top of the cooling tank 210 is connected to the three-way valve 272 via a pipe 274. This forms a path for circulating the insulating liquid 230 through the cooling tank 210, the pipe 241, the pipe 251, the three-way valve 272, the pump 273, and the pipe 241.

[0119] The three-way valve 272 is an electromagnetic valve that switches between a state in which the insulating liquid 230 in the upper part of the cooling tank 210 flows into the lower part of the cooling tank 210 and a state in which the insulating liquid 230 does not flow into the lower part of the cooling tank 210. The pump 273 pressure-feeds the insulating liquid 230 that flows from the pipe 241 through the three-way valve 272 to the lower part of the cooling tank 210.

[0120] Three-way valve 272 and pump 273 are controlled by, for example, BMS 160. Of course, three-way valve 272 and pump 273 may be controlled by a control device different from BMS 160. For example, three-way valve 272 and pump 273 may be controlled by a device dedicated to three-way valve 272 and pump 273. Alternatively, they may be controlled by another control device mounted on eVTOL 100.

[0121] When eVTOL 100 is flying (discharging), three-way valve 272 connects pipe 274 to pipe 251. Furthermore, pump 273 pressure-feeds insulating liquid 230 to the bottom of cooling tank 210. As a result, insulating liquid 230 circulates through cooling tank 210, pipe 241, pipe 274, and pipe 251, thereby efficiently cooling each battery cell 220 and maintaining a uniform temperature for each battery cell 220.

[0122] When eVTOL 100 is on the ground (charging), three-way valve 272 shuts off pipe 274 from pipe 251. Three-way valve 272 is also connected to pipe 430 of cryogenic cooling device 400. In other words, three-way valve 272 functions as a valve joint. This allows cryogenic insulating liquid 230 to be pressure-fed from cryogenic cooling device 400 to cooling tank 210.

[0123] Note that when eVTOL 100 is on the ground (charging), pump 273 externally attached to cooling tank 210 may be operated to pressure-feed insulating liquid 230 from low-temperature cooling device 400 to cooling tank 210. Of course, both pump 440 of low-temperature cooling device 400 and pump 273 of cooling tank 210 may be operated to pressure-feed insulating liquid 230 to cooling tank 210. When eVTOL 100 is on the ground (charging), control device 500 may control three-way valve 272 and pump 273.

[0124] 11 , flow device 270 may be configured with piping 241, piping 251, a three-way valve 272, a pump 273, piping 274, and a heat exchanger 275. Heat exchanger 275 is connected to piping 274 attached externally to cooling tank 210. Heat exchanger 275 is, for example, a dedicated component for cooling tank 210. Heat exchanger 275 may be substituted by one installed in 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, by providing the heat exchanger 275 in the piping 274, the insulating liquid 230 can be cooled even during flight (discharge) of the eVTOL 100. Therefore, low-temperature insulating liquid 230 can be constantly supplied to each battery cell 220, which further improves the cooling performance of the insulating liquid 230 and the temperature uniformity performance of each battery cell 220.

[0127] The three-way valve 272 in this embodiment corresponds to the valve joint.

[0128] Fourth Embodiment In this embodiment, the differences from the first to third embodiments will be mainly described. As shown in Fig. 12, a cooling tank 210 has a latent heat storage material 280 that has a cold storage 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 that accompanies a phase change. In this embodiment, a resin heat storage material containing a microencapsulated latent heat storage material is used as the latent heat storage material 280. The microencapsulated latent heat storage material is a heat storage material in which the latent heat storage material is encapsulated in microcapsules.

[0130] A latent heat storage material having a phase change temperature (melting point) of 60° C. or less can be used as the latent heat storage material 280. Specifically, for example, a paraffin-based hydrocarbon, a hydrate-based, a metal-based, or a water-based latent heat storage material can be used as the latent heat storage material 280.

[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 contained in the insulating liquid 230, and the latent heat storage material 280 is dispersed in the insulating liquid 230. This increases the heat capacity of the insulating liquid 230 containing the latent heat storage material 280.

[0132] During flight (discharge) of eVTOL 100, heat from each battery cell 220 is absorbed by both insulating liquid 230 and latent heat storage material 280. Therefore, the temperature rise of each battery cell 220 can be effectively suppressed.

[0133] 13 , a filter 214 for blocking the passage of the latent heat storage material 280 may be installed inside the cooling tank 210 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 a connection between the pipe 241 and the cooling tank 210. The filter 214 may be provided at a connection between the pipe 251 and the cooling tank 210. This allows the latent heat storage material 280 to be kept inside the cooling tank 210.

[0135] 14 , the latent heat storage material 280 may be disposed between adjacent battery cells 220, and filters 223 may be provided between the upper surfaces and the lower surfaces of adjacent battery cells 220. This allows the latent heat storage material 280 to be retained between the adjacent battery cells 220.

[0136] In this case, predetermined amounts of the latent heat storage material 280 are placed in predetermined locations. That is, a large amount of the latent heat storage material 280 is placed in the high heat generating portion of each battery cell 220, and a small amount of the latent heat storage material 280 is placed in the low heat generating portion. In other words, the placement location and amount of the microcapsule latent heat storage material can be managed.

[0137] As described above, by confining the phase change material 280 between adjacent battery cells 220, it is possible to suppress the temperature distribution due to the heat generation distribution of each battery cell 220. Furthermore, since it is possible to intensively cool the high heat generation parts of each battery cell 220, it is not necessary to disperse a large amount of the phase change material 280 throughout the insulating liquid 230. Therefore, it is possible to reduce the amount of phase change material 280 used.

[0138] 15, fixed heat storage tubes 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 arranged in high heat generation parts of each battery cell 220, and fewer fixed heat storage tubes can be arranged in low heat generation parts. In other words, the location and size of the fixed heat storage tubes can be managed.

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

[0140] As described above, even when fixed heat storage tubes are used, it is possible to suppress the temperature distribution due to the heat generation distribution of the battery cells 220. Furthermore, it is possible to reduce the amount of fixed heat storage tubes.

[0141] Furthermore, the latent heat storage material 280 may be both a microcapsule latent heat storage material and a fixed type heat storage tube.

[0142] Fifth Embodiment In this embodiment, differences from the first to fourth embodiments will be mainly described. 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 in Figure 16. As shown in Figures 16 and 17, each battery cell 220 has an opposing surface 227 that faces the adjacent battery cell 220.

[0143] The battery cooling device 200 also 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, which is transferred via 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 plate members 224, 225 and a captive screw 226 for fixing the spacer member 290 between the battery cells 220 to the battery cells 220. The pair of plate members 224, 225 are arranged at one end and the other end in the stacking direction of the stack of each battery cell 220 and spacer member 290, and sandwich the stack. The captive screw 226 tightens the stack so that the pair of plate members 224, 225 come relatively close to each other. This restrains the spacer member 290 and each battery cell 220.

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

[0146] 18, in this embodiment, offset fins are used as the spacer members 290. The offset fins have a corrugated cross section with partially cut-and-raised portions formed on the corrugated portions. The offset fins are 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 surfaces 227 of the battery cells 220. The support portion 292 is sandwiched between adjacent battery cells 220 and supports the adjacent battery cells 220, thereby maintaining the distance 221 between the adjacent battery cells 220. The support portion 292 has enough strength to withstand the restraint load when the spacer member 290 and each battery cell 220 are restrained by the restraint screws 226.

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

[0149] As the spacer member 290, in addition to the offset fins, the corrugated fins shown in FIG. 19, the wave fins shown in FIG. 20, and the louver fins shown in FIG. 21 may be used.

[0150] A corrugated fin is a fin made by repeatedly and alternately folding a metal plate into a wave-like shape, forming alternating peaks and valleys. A wave fin is a fin whose cross section is formed into a rectangular or trapezoidal wave shape and meanders in one direction. A louver fin is a fin with multiple louvers formed in the waves that make up the wave-shaped cross section.

[0151] With the above configuration, heat from each battery cell 220 can be transferred to the insulating liquid 230 without impairing the natural unidirectional flow of the insulating liquid 230. Furthermore, because the support portions 292 of the spacer members 290 maintain the spacing 221 between adjacent battery cells 220, it is possible to restrain both the battery cells 220 while keeping the spacer members 290 in contact with them.

[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, and is therefore able to pass through the passage portion 291. Furthermore, when a fixed type heat storage tube is used as the latent heat storage material 280, both the spacer member 290 and the fixed type 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 flat tube formed by extruding a metal material. The internal space of the extruded tube corresponds to the passage portion 291. The wall portion that forms the space of the extruded tube corresponds to the support portion 292.

[0154] As a modification, as shown in Figure 23, an inner fin tube may be used as the spacer member 290. The inner fin tube is a tube formed by bending a metal strip-shaped plate material, with a bent portion at one end of the tube and a crimped portion at the other end, and an inner fin formed from a metal strip-shaped plate material is disposed inside the tube. The crimped portion at the other end is crimped with the inner fin in contact with the inner wall of the tube. The internal space of the inner fin tube corresponds to the passage portion 291. The fin inside the inner fin tube corresponds to the support portion 292.

[0155] 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, and is therefore able to pass through the passage portion 291. Furthermore, when a fixed type heat storage tube is used as the latent heat storage material 280, both the extruded tube and the fixed type heat storage tube are sandwiched between adjacent battery cells 220. Alternatively, both the inner fin tube and the fixed type heat storage tube are sandwiched between adjacent battery cells 220.

[0156] Furthermore, the spacer member 290 is not limited to a single one of offset fins, corrugated fins, wave fins, louver fins, extruded tubes, and inner fin tubes, but may be a combination of any of them. Of course, three or more types may also 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 above-described pair of plate members 224, 225, the restraining screw 226, or other restraining devices.

[0158] In this case, the outer peripheral surface of the can-shaped battery cell 220 corresponds to the facing surface 227. A direction parallel to the axial direction of the battery cell 220 can be set as one direction. A direction perpendicular to the axial direction of the battery cell 220, i.e., the radial direction, can also be set as one direction.

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

[0160] Sixth Embodiment In this embodiment, differences from the first to fifth embodiments will be mainly described. As shown in Fig. 24, the electrode terminals of each battery cell 220 are oriented toward the ground, and each bus bar 222 is located at the bottom of the cooling tank 210. The bus bars 222 are routed from the bottom to the top of the cooling tank 210. In other words, the bus bars 222 connecting each battery cell 220 are submerged in the insulating liquid 230.

[0161] As a result, the insulating liquid 230, which has absorbed heat from the bus bars 222 in the lower part of the cooling tank 210 and become hot, moves to the upper part of the cooling tank 210. This promotes convection of the insulating liquid 230 in the vertical direction, thereby improving the cooling performance of the insulating liquid 230 for each battery cell 220.

[0162] 25 to 27, the electrode terminals of each battery cell 220 may be oriented in a direction perpendicular to the top-to-bottom direction, so that the bus bars 222 connecting adjacent battery cells 220 are positioned at an intermediate depth in the cooling tank 210. Note that Fig. 25 is a top view of the cooling tank 210 with the lid removed.

[0163] Seventh Embodiment In this embodiment, differences from the first to sixth embodiments will be mainly described. As shown in Fig. 28 , a battery cooling device 200 according to this embodiment has fins 260 provided on both an outer wall surface 211 and an inner wall surface 212 of a cooling tank 210, and a fan 261 provided outside the cooling tank 210. Furthermore, a microcapsule latent heat storage material is mixed into the insulating liquid 230 as the latent heat storage material 280. In this embodiment, filters 214, 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, when eVTOL 100 is flying (discharging), each battery cell 220 and bus bar 222 stores heat and is cooled by insulating liquid 230 and latent heat storage material 280. In addition, forced air cooling from the outside of cooling tank 210 by fan 261 promotes heat dissipation from the inside of cooling tank 210 to the outside.

[0165] When eVTOL 100 is on the ground (charging), as shown in Fig. 29 , cooling tank 210 of battery cooling device 200 is connected to a low-temperature cooling device 400 on the ground. Insulating liquid 230 in tank 410 of low-temperature cooling device 400 is pre-cooled, and microcapsule latent heat storage material is mixed into insulating liquid 230 as latent heat storage material 280. Note that control device 500 is omitted from Fig. 29 .

[0166] The battery cooling device 200 and the low-temperature cooling device 400 are then connected via valve joints 240 and 250 to form a cooling circulation circuit 460. Thereafter, pre-cooled low-temperature insulating liquid 230 circulates through the cooling circulation circuit 460. This allows each battery cell 220 inside the cooling tank 210 to be rapidly cooled. Note that 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 another cooling method, when eVTOL 100 is on the ground (charging), battery cooling device 200 and low-temperature cooling device 400 may be connected via valve joints 240 and 250, and then insulating liquid 230 may be discharged from cooling tank 210 via discharge valve 450 of piping 430 that constitutes cooling circulation circuit 460. After this, insulating liquid 230 that has been pre-cooled in low-temperature cooling device 400 is filled from low-temperature cooling device 400 into battery cooling device 200. In this way, insulating liquid 230 does not need to circulate through cooling circulation circuit 460.

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

[0169] Alternatively, while the insulating liquid 230 in the cooling tank 210 is discharged through the discharge valve 450, low-temperature insulating liquid 230 may be supplied from the top of the cooling tank 210 via the valve joint 240 at the top of the cooling tank 210. In this case, the insulating liquid 230 is not circulated, but low-temperature insulating liquid 230 can be constantly supplied to each battery cell 220, thereby effectively suppressing heat generation during charging. Then, by closing the discharge valve 450 near the end of charging, the cooling tank 210 can be filled with low-temperature insulating liquid 230. Of course, 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.

[0170] When the insulating liquid 230 is filled into the cooling tank 210 after being discharged from the cooling tank 210, it is sufficient that at least one valve joint is provided in the cooling tank 210. In other words, the insulating liquid 230 can be discharged and filled using one valve joint. Alternatively, multiple valve joints may be provided in the cooling tank 210, such as two valve joints for discharge and two valve joints for filling. Even when the insulating liquid 230 is circulated through the cooling circulation circuit 460, multiple valve joints may be provided in the cooling tank 210.

[0171] 30 , the battery cooling device 200 may include a pipe 274, a three-way valve 272, and a pump 273 instead of the valve joint 250. In addition, oil is used as the insulating liquid 230.

[0172] In this case, when eVTOL 100 is flying (discharging), each battery cell 220 and bus bar 222 stores heat and is cooled by oil, which is insulating liquid 230, and latent heat storage material 280. In addition, cooling tank 210 is forcedly air-cooled by fan 261. Furthermore, oil is circulated inside cooling tank 210 by pump 273. This allows for uniform temperature distribution and accelerated cooling of each battery cell 220.

[0173] 31 , when eVTOL 100 is on the ground (charging), three-way valve 272 of cooling tank 210 disconnects pipe 274 from pipe 251. Furthermore, valve joint 240 is connected to pipe 420 of low-temperature cooling device 400, and three-way valve 272 is connected to pipe 430 of low-temperature cooling device 400. This forms cooling circulation circuit 460. The insulating liquid 230 may be circulated through cooling circulation circuit 460 as described above, or may be discharged from cooling tank 210 via discharge valve 450 and then filled with low-temperature insulating liquid 230 into cooling tank 210.

[0174] As another 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 external heat dissipation by the heat exchanger 275 when the eVTOL 100 is flying (discharging), thereby further improving the cooling performance of the battery cooling device 200.

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

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

[0177] The flight conditions include, for example, flight distance, flight time, flight altitude, flight route, flight speed, number of flights, number of passengers on board, payload weight, climatic conditions, weather along the flight route, aircraft specifications, etc. In other words, the flight conditions are related to the magnitude of the load on the battery pack during flight.

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

[0179] The amount and initial temperature of the insulating liquid 230 are calculated from a relational expression between a value indicating the flight condition and the amount and initial temperature of the insulating liquid 230. Alternatively, the amount and initial temperature of the insulating liquid 230 according to the flight condition may be derived from a map indicating the relationship between the flight condition, the amount of the insulating liquid 230, and the initial temperature.

[0180] For example, the control device 500 calculates the required output and usage of each battery cell 220 from the flight conditions, and calculates the battery heat generation amount of 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 battery heat generation amount at or below the allowable temperature of the battery cell 220. For example, the battery heat generation amount can be calculated as battery heat generation amount = (battery heat capacity + amount of insulating liquid × specific heat) × (allowable temperature - initial temperature).

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

[0182] The control device 500 acquires the amount and initial temperature of the insulating liquid 230 in advance based on the flight conditions before the next flight of the eVTOL 100. Then, when the eVTOL 100 is on the ground (charging), the control device 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 to be contained in the cooling tank 210 according to the flight conditions of the eVTOL 100. Note that the inside of the cooling tank 210 may be filled with low-temperature insulating liquid 230 while the battery cells 220 are being rapidly cooled.

[0183] Here, the battery cooling device 200 has a level gauge. The level gauge is installed in the cooling tank 210 and detects the height of the liquid surface of the insulating liquid 230. The level gauge may be either a type that contacts the insulating liquid 230 or a type that does not contact the insulating liquid 230. The 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. In this way, the control device 500 can control the amount of insulating liquid 230 contained in the cooling tank 210 to vary depending on the flight conditions of the eVTOL 100. For example, the control device 500 reduces the amount of insulating liquid 230 below a reference amount under a first flight condition (low-load flight) and increases the amount of insulating liquid 230 above the reference amount under a second flight condition (high-load flight).

[0185] The amount of insulating liquid 230 in cooling tank 210 may be measured by a flow rate sensor. The flow rate sensor is provided on a pipe for pressure-feeding insulating liquid 230 to cooling tank 210. For example, the flow rate sensor is provided on pipe 251 of battery cooling device 200 or pipe 430 of battery cooling system 300. Control device 500 controls the flow rate of insulating liquid 230 pressure-feeding to cooling tank 210 based on a signal from the flow rate sensor.

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

[0187] 34 , when the load on each battery cell 220 is low due to flight conditions, the liquid level 231 of the insulating liquid 230 is at a position lower than the reference position in the cooling tank 210. In other words, a smaller amount of insulating liquid 230 is required. Therefore, when the load on each battery cell 220 is low, the weight of the battery cooling device 200 can be reduced.

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

[0189] 36 , when each battery cell 220 is under high load due to flight conditions, the insulating liquid 230 immerses the entire battery case that constitutes the battery cell 220. This ensures the cooling performance of the insulating liquid 230 for the battery cell 220. Note that the position of the liquid surface 231 of the insulating liquid 230 may be adjusted so that part 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, so it is 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 contained in the cooling tank 210 changes evenly. In other words, each battery cell 220 is evenly immersed in the insulating liquid 230. Therefore, each battery cell 220 can be evenly cooled.

[0191] In the conventional technology, a cooler is provided for each battery cell. Therefore, even if the amount of coolant is changed, it is difficult to uniformly change the amount of coolant for each battery cell 220. This results in variations 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 flight conditions, the liquid level 231 of the insulating liquid 230 for the multiple battery cells 220 contained in the cooling tank 210 changes evenly, so that each battery cell 220 can be cooled evenly.

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

[0194] The present disclosure is not limited to the above-described embodiments, and various modifications can be made as follows within the scope of the present disclosure.

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

[0196] Alternatively, each battery cell 220 may be accommodated in the cooling tank 210 so that the opposing surfaces 227 of each battery cell 220 are aligned in a direction perpendicular to the top-bottom direction. In other words, the opposing surfaces 227 of each battery cell 220 may be arranged so that they are aligned 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, and may be inclined relative to the horizontal direction.

[0197] A phase change material that solidifies at approximately the lower limit of the operating temperature of the battery cells 220 may be used as the insulating liquid 230. The phase change material is liquid within the normal operating temperature range of the battery cells 220 (approximately 10°C to 60°C) and absorbs heat from each battery cell 220. In addition, in special cases where the temperature approaches the lower limit of the normal operating temperature range of the battery cells 220, the liquid phase change material solidifies, i.e., releases latent heat. This allows the temperature of the battery cells 220 to be maintained at the lower limit of the operating temperature range without dropping below it. This prevents the temperature of the battery cells 220 from dropping below the lower limit of the operating temperature range. Furthermore, it is possible to prevent a decrease in the output of the battery cells 220 during landing.

[0198] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0199] The technical features of the battery cooling device and battery cooling system disclosed in this specification are as follows: (Item 1) A battery cooling device applicable to an electric flying vehicle (100), comprising: a cooling tank (210); a plurality of battery cells (220) contained in the cooling tank; an insulating liquid (230) flowably contained in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; and a valve fitting (240, 250, 272) provided in the cooling tank, to which a low-temperature cooling device (400) capable of flowing in and out of the insulating liquid inside the cooling tank is attached and detached. (Item 2) The battery cooling device according to item 1, wherein the plurality of battery cells are electrically connected to one another by a bus bar (222), and at least a portion of the bus bar is in direct contact with the insulating liquid. (Item 3) The battery cooling device according to item 1 or 2, wherein the cooling tank includes an outer wall surface (211) and an inner wall surface (212), and further wherein the cooling tank includes fins (260) provided on either the outer wall surface, the inner wall surface, or both the outer wall surface and the inner wall surface, for dissipating heat 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 flow device (270) for flowing the insulating liquid. (Item 5) The battery cooling device according to any one of items 1 to 4, wherein the cooling tank includes a latent heat storage material (280) that is added to the insulating liquid and stores or dissipates heat by utilizing the entry and exit of latent heat associated with a 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 battery cooling device according to any one of items 1 to 7, wherein the plurality of battery cells are arranged with a gap (221) between adjacent battery cells and each have an opposing surface (227) facing the adjacent battery cell, and includes a spacer member (290) that is sandwiched between the adjacent battery cells and comes into contact with the opposing surfaces of the adjacent battery cells to transfer heat from the battery cells via the opposing surfaces to the insulating liquid, the spacer member including: a passage portion (291) through which the insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cells, and a support portion (292) that contacts the opposing surfaces of the battery cells to maintain the gap between the adjacent battery cells. (Item 9) The battery cooling device according to any one of items 1 to 8, wherein, when a center position of the cooling tank in a vertical direction is defined as a reference position, the valve fitting is provided in the cooling tank lower than the reference position 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 position 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 the insulating liquid contained in the cooling tank varies depending on flight conditions of the electric flying vehicle.(Item 12) A battery cooling system applicable to an electric flying body (100), comprising: a cooling tank (210); a plurality of battery cells (220) accommodated in the cooling tank; an insulating liquid (230) flowably accommodated in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve joint (240, 250, 272) provided in the cooling tank and to which a low-temperature cooling device (400) capable of flowing in and out of the insulating liquid inside the cooling tank is detachably attached; the low-temperature cooling device that cools and stores the insulating liquid; and a control device (500) that controls the low-temperature cooling device; wherein the battery cooling device and the low-temperature cooling device are connected via the valve joint to form a cooling circulation circuit (460) that allows the insulating liquid to circulate between the battery cooling device and the low-temperature cooling device, The control device 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 flying body (100), comprising: a cooling tank (210); a plurality of battery cells (220) accommodated in the cooling tank; an insulating liquid (230) flowably accommodated in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve joint (240, 250, 272) provided in the cooling tank and to which a low-temperature cooling device (400) capable of flowing in and out of the insulating liquid inside the cooling tank is detachably attached; the low-temperature cooling device that cools and stores the insulating liquid; and a control device (500) that controls the low-temperature cooling device; wherein the battery cooling device and the low-temperature cooling device are connected via the valve joint to form a cooling circulation circuit (460) that allows the insulating liquid to circulate between the battery cooling device and the low-temperature cooling device, The control device discharges the insulating liquid from inside the cooling tank through the cooling circulation circuit, and then fills the insulating liquid that has been pre-cooled in the low-temperature cooling device from the low-temperature cooling device into the battery cooling device.(Item 14) The battery cooling system according to item 12 or 13, wherein the control device controls the amount of the insulating liquid contained in the cooling tank to vary depending on flight conditions of the electric flying vehicle.

Claims

1. A battery cooling device applied to an electric flying object (100), a cooling tank (210); a plurality of battery cells (220) housed in the cooling tank; an insulating liquid (230) that is flowably accommodated in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve joint (240, 250, 272) provided in the cooling tank and to which a low-temperature cooling device (400) is detachably attached, the low-temperature cooling device (400) being capable of allowing the insulating liquid inside the cooling tank to flow in and out; Including, The plurality of battery cells are arranged with a gap (221) between adjacent battery cells, and each battery cell has an opposing surface (227) facing the adjacent battery cell, a spacer member (290) that is sandwiched between adjacent battery cells and comes into contact with the opposing surfaces of the adjacent battery cells, and that is capable of transferring heat from the battery cells via the opposing surfaces to the insulating liquid; The spacer member is a passage portion (291) through which the insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cell; a support portion (292) that contacts the opposing surfaces of the battery cells to maintain the spacing between adjacent battery cells; Including, The battery cooling device, wherein the spacer member is one of an offset fin, a corrugated fin, a wave fin, a louver fin, an extruded tube, and an inner fin tube.

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

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

4. The battery cooling device according to claim 1 or 2, wherein the cooling tank includes a flow 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) added to the insulating liquid and storing or releasing heat by utilizing the transfer of latent heat accompanying a phase change.

6. 3. The battery cooling device according to claim 1, 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 the center position of the cooling tank in the vertical direction is defined as the reference position, The battery cooling device according to claim 1 or 2, wherein the valve joint is provided in the cooling tank at a position lower than the reference position in the vertical direction.

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

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

11. A battery cooling system applied to an electric flying vehicle (100), a cooling tank (210); a plurality of battery cells (220) housed in the cooling tank; an insulating liquid (230) that is flowably accommodated in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve joint (240, 250, 272) provided in the cooling tank and to which a low-temperature cooling device (400) is detachably attached, the low-temperature cooling device (400) being capable of allowing the insulating liquid inside the cooling tank to flow in and out; Including, The plurality of battery cells are arranged with a gap (221) between adjacent battery cells, and each battery cell has an opposing surface (227) facing the adjacent battery cell, a spacer member (290) that is sandwiched between adjacent battery cells and comes into contact with the opposing surfaces of the adjacent battery cells, and that is capable of transferring heat from the battery cells via the opposing surfaces to the insulating liquid; The spacer member is a passage portion (291) through which the insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cell; a support portion (292) that contacts the opposing surfaces of the battery cells to maintain the spacing between adjacent battery cells; Including, The spacer member is any one of an offset fin, a corrugated fin, a wave fin, a louver fin, an extruded tube, and an inner fin tube. the low-temperature cooling device that cools and stores the insulating liquid; A control device (500) for controlling the low-temperature cooling device; Including, The battery cooling device and the low-temperature cooling device are connected via the valve joint to form 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 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 applied to an electric flying vehicle (100), a cooling tank (210); a plurality of battery cells (220) housed in the cooling tank; an insulating liquid (230) that is flowably accommodated in the cooling tank, immersing the plurality of battery cells and absorbing heat from the plurality of battery cells; a valve joint (240, 250, 272) provided in the cooling tank and to which a low-temperature cooling device (400) is detachably attached, the low-temperature cooling device (400) being capable of allowing the insulating liquid inside the cooling tank to flow in and out; Including, The plurality of battery cells are arranged with a gap (221) between adjacent battery cells, and each battery cell has an opposing surface (227) facing the adjacent battery cell, a spacer member (290) that is sandwiched between adjacent battery cells and comes into contact with the opposing surfaces of the adjacent battery cells, and that is capable of transferring heat from the battery cells via the opposing surfaces to the insulating liquid; The spacer member is a passage portion (291) through which the insulating liquid can flow in one direction parallel to the opposing surfaces of the battery cell; a support portion (292) that contacts the opposing surfaces of the battery cells to maintain the spacing between adjacent battery cells; Including, The spacer member is any one of an offset fin, a corrugated fin, a wave fin, a louver fin, an extruded tube, and an inner fin tube. the low-temperature cooling device that cools and stores the insulating liquid; A control device (500) for controlling the low-temperature cooling device; Including, The battery cooling device and the low-temperature cooling device are connected via the valve joint to form 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 through the cooling circulation circuit, and then fills the insulating liquid that has been pre-cooled in the low-temperature cooling device from the low-temperature cooling device into the battery cooling device.

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