Electric driving device for aircraft

Abstract

To provide an electric driving device for an aircraft that can make both suppression of electric power consumption and securement of cooling performance compatible, while suppressing a system from increasing in weight.SOLUTION: A driving device 16 for an aircraft comprises an electric motor 31 that drives a rotary vane (18) that generates lifting force or driving force, and a fan 33 that is driven by the electric motor 31 to generates cooling air for cooling the electric motor 31. The driving device 16 further comprises a clutch device 230 that connects and disconnects driving force that is transmitted from the electric motor 31 to the fan 33, in accordance with an external environment.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an electric drive system for an aircraft. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and research and development into electrification technologies is being actively carried out in order to reduce CO2 emissions and improve energy efficiency in vehicles.

[0003] Patent Document 1 discloses an electric drive system for an aircraft. The electric drive system includes multiple redundant motors, and power generated by the multiple motors is used to drive a rotor system including a rotor shaft having multiple rotor blades. The electric drive system further includes a cooling fan for drawing air into the unit to cool electronic components. The cooling fan is mechanically powered by the rotor shaft. Alternatively, the cooling fan is electrically powered. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 11,565,802 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the electric drive system described in Patent Document 1, the cooling fan is directly connected to the end of the rotor shaft opposite the end where the rotor blades are attached. Therefore, the fan always rotates in conjunction with the rotation of the motor. However, there are situations during aircraft flight where there is little need to cool the motor, such as when flying at high altitudes in low temperatures or during cruising flight. Driving the fan under such conditions results in unnecessary power consumption and worsens the aircraft's power consumption. If the fan is electrically powered, it can be stopped when there is little need to cool the motor. However, the need for a motor to drive the fan increases the weight of the system.

[0006] In view of the above background, an object of the present invention is to provide an electric drive unit for an aircraft that can reduce power consumption and ensure cooling performance while suppressing an increase in the weight of the system. [Means for solving the problem]

[0007] In order to solve the above problems, one aspect of the present invention is an electric drive unit (16) for an aircraft, which comprises a rotating electric machine (31) that drives a rotor that generates lift or thrust, and a fan (33) that is driven by the rotating electric machine and generates cooling air for cooling the rotating electric machine, and further comprises a clutch device (230) that connects and disconnects the driving force transmitted from the rotating electric machine to the fan depending on the external environment.

[0008] According to this aspect, a clutch device is provided that connects and disconnects the driving force to the fan in response to the external environment, so that the fan can be switched on and off depending on the external environment, which changes depending on the flight environment of the aircraft. Therefore, when cooling of the rotating electric machine is not required, the clutch device disconnects the driving force and stops the fan, thereby reducing unnecessary power consumption. In addition, a decrease in output of the rotating electric machine due to overcooling is also suppressed.

[0009] In the above aspect, the clutch device may include a clutch mechanism (231) that is provided in a power transmission path from the rotating electric machine to the fan and is configured to be able to connect and disconnect the driving force, and an air pressure difference actuation mechanism (232) that switches the connection and disconnection of the clutch mechanism depending on the pressure difference between a reference air pressure that is kept constant and the outside air pressure.

[0010] When an electronic control device that measures the external environment and switches the clutch mechanism on and off is used in a clutch device, high-altitude countermeasures such as electrical discharge countermeasures and radiation countermeasures are required. According to this aspect, the clutch mechanism is switched on and off by a pressure difference actuation mechanism that mechanically operates in response to the pressure difference between the external air pressure and the reference air pressure, so high-altitude countermeasures are not required. This simplifies the configuration of the aircraft electric drive device. Furthermore, because the clutch mechanism is switched on and off in response to the external air pressure that changes with flight altitude, the operation of the fan can be switched depending on the flight altitude.

[0011] In the above aspect, the air pressure difference actuation mechanism may be configured to disconnect the clutch mechanism when the differential pressure obtained by subtracting the external air pressure from the reference air pressure is greater than a predetermined threshold value, and to connect the clutch mechanism when the differential pressure is smaller than the threshold value.

[0012] According to this aspect, the fan is stopped at high altitudes where cooling of the rotating electric machine is not required, and is operated at low altitudes such as on the ground, thereby ensuring that the fan operates when cooling of the rotating electric machine is required and can be stopped at high altitudes where cooling is not required.

[0013] In the above aspect, the clutch mechanism may be provided to connect and disconnect the driving force between the shaft (38) of the rotating electric machine and the hub (223) of the fan.

[0014] According to this aspect, there is no need to provide an additional member such as an extension shaft in order to provide a clutch mechanism, and therefore the configuration of the propulsion drive device can be simplified.

[0015] In the above aspect, the clutch mechanism preferably includes a piston (237) that is actuated by the pressure difference between the external atmospheric pressure and the reference atmospheric pressure, an inner ring member (233) that is connected to the shaft and slidably supports the piston, an oscillating member (240) journaled to the inner ring member, and an outer ring member (234) that is connected to the hub of the fan and has an engaging portion (244) with which the oscillating member engages when the piston is actuated.

[0016] According to this aspect, by configuring the clutch mechanism with a piston and oscillating member that are actuated by differential pressure, an inner ring member that supports these, and an outer ring member that engages with the oscillating member to enable the fan to rotate, the clutch mechanism can be realized with a small number of parts, thereby improving the reliability of the mechanism.

[0017] In the above aspect, the air pressure difference actuation mechanism may include an air pressure chamber (238) formed inside the shaft and holding the reference air pressure to be applied to the piston, and a connecting pipe (239) connecting the shaft to the fuselage (2) of the aircraft to introduce cabin pressure in the aircraft (1) in which the electric drive unit is installed to the air pressure chamber.

[0018] According to this aspect, by using the cabin internal air pressure as the reference air pressure, it is possible to realize a pressure difference actuated mechanism with a simple configuration.

[0019] In the above aspect, the clutch device may include an electromagnetic clutch (260) provided in a power transmission path from the rotating electric machine to the fan, and a control device (270) that acquires the external environment and controls the engagement and disengagement of the electromagnetic clutch.

[0020] According to this aspect, an electromagnetic clutch is used as the clutch, and the control device acquires information about the external environment and electrically controls the engagement and disengagement of the clutch. This allows for more precise control of the engagement and disengagement of the clutch in accordance with various conditions in the external environment, thereby enabling more appropriate control of the operation of the fan.

[0021] In the above aspect, the electromagnetic clutch may be provided to connect and disconnect the driving force between the shaft (38) of the rotary electric machine and the hub (223) of the fan.

[0022] According to this aspect, there is no need to provide an additional member such as an extension shaft in order to provide an electromagnetic clutch, and therefore the configuration can be simplified. [Effects of the Invention]

[0023] According to the above aspects, it is possible to provide an electric drive device for an aircraft that can reduce power consumption and ensure cooling performance while suppressing an increase in the weight of the system. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view showing an aircraft according to an embodiment; [Figure 2] FIG. 1 is a partial cross-sectional view schematically illustrating a propulsion unit according to a first embodiment. [Figure 3] FIG. 1 is a perspective view showing a propulsion drive device according to a first embodiment; [Figure 4] FIG. 1 is an exploded perspective view showing a propulsion drive device according to a first embodiment; [Figure 5] FIG. 1 is a cross-sectional view showing a propulsion drive device according to a first embodiment; [Figure 6] FIG. 1 is a cross-sectional view of a clutch mechanism according to a first embodiment; [Figure 7] An explanatory diagram of the operation of the air pressure difference actuation mechanism according to the first embodiment. [Figure 8] 1 is a diagram illustrating the operation of the clutch mechanism according to the first embodiment; [Figure 9] FIG. 10 is a cross-sectional view of a clutch mechanism according to a modified example; [Figure 10] FIG. 10 is a partial cross-sectional view schematically showing a propulsion unit according to a second embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing a propulsion drive device according to a second embodiment. [Figure 12] 10 is an explanatory diagram of the operation of the electromagnetic clutch according to the second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0025] <Aircraft 1> An aircraft 1 (an example of a moving object) according to an embodiment of the present invention will now be described with reference to the drawings.

[0026] First Embodiment 1, aircraft 1 is an electric vertical take-off and landing (eVTOL) aircraft that can take off and land vertically. Aircraft 1 has a fuselage 2 extending in the longitudinal direction, front wings 3 extending in the left-right direction and connected to the front portion of fuselage 2, rear wings 4 extending in the left-right direction and connected to the rear portion of fuselage 2, a left arm 5L extending in the longitudinal direction and connecting the left end of front wing 3 to the left side of rear wing 4, and a right arm 5R extending in the longitudinal direction and connecting the right end of front wing 3 to the right side of rear wing 4.

[0027] A cabin (not shown) for passengers is provided at the front of the fuselage 2. Left and right propulsion units 7 (described in detail below) for generating forward thrust for the aircraft 1 are provided at the rear end of the fuselage 2.

[0028] The left arm 5L and the right arm 5R each have a plurality of (for example, four) lifting units 10 spaced apart in the front-to-rear direction to generate ascending and descending forces for the aircraft 1. Each lifting unit 10 has a lifting drive device 12 and a lifting propeller 13 attached to the lifting drive device 12. The lifting drive device 12 has an electric motor (not shown) and is configured to rotate the lifting propeller 13 by the driving force of this electric motor.

[0029] <Propulsion Unit 7> Referring to Figure 2, each propulsion unit 7 has a support body 15, front and rear propulsion drive units 16 (an example of an aircraft electric drive unit) supported by the support body 15, a rotating shaft 17 extending in the fore-and-aft direction and rotatably supported by the front and rear propulsion drive units 16, and a propulsion propeller 18 (an example of a rotor) fixed to the rear of the rotating shaft 17.

[0030] The support body 15 is fixed to the rear end of the fuselage 2 (see FIG. 1). The support body 15 has a cylindrical nacelle 20 extending in the fore-and-aft direction, and front and rear mount frames 21 fixed to the inner circumferential surface of the nacelle 20. Each mount frame 21 has an annular hub 23 provided concentrically with the nacelle 20, and a plurality of spokes 24 extending radially from the outer circumferential surface of the hub 23 and connected to the inner circumferential surface of the nacelle 20.

[0031] The front and rear propulsion drive units 16 are housed in nacelles 20. The front and rear propulsion drive units 16 are fixed to the front surfaces of hubs 23 of front and rear mount frames 21, respectively. Details of each propulsion drive unit 16 will be described later.

[0032] The rotating shaft 17 is housed in the nacelle 20. The rotating shaft 17 passes through the hubs 23 of each mount frame 21. A conical front cover 26, whose diameter increases toward the rear, is fixed to the front end of the rotating shaft 17. The front cover 26 is disposed in front of the front propulsion drive unit 16. A conical rear cover 27, whose diameter increases toward the front, is fixed to the rear end of the rotating shaft 17. The rear cover 27 is disposed behind the center of the propulsion propeller 18.

[0033] The propulsion propeller 18 is housed in the nacelle 20. The propulsion propeller 18 is configured to rotate integrally with the rotation shaft 17 as the rotation shaft 17 rotates, thereby generating a forward thrust for the aircraft 1.

[0034] <Propulsion Drive Unit 16> 2 and 3, each propulsion drive unit 16 includes an electric motor 31 (an example of a rotating electric machine), a control device 32 disposed behind the electric motor 31, a fan 33 disposed in front of the electric motor 31, and a duct cover 34 that covers the outer periphery of the electric motor 31, the control device 32, and the fan 33. Note that the duct cover 34 is not shown in FIG.

[0035] <Electric Motor 31> 4 and 5, electric motor 31 is sandwiched between control device 32 and fan 33. For example, electric motor 31 is an inner rotor type three-phase AC motor. Electric motor 31 has a housing 36, a cover 37, a shaft 38, a rotor 39, and a stator 40.

[0036] The housing 36 is cylindrical and extends in the front-to-rear direction around the outer periphery of the shaft 38. The housing 36 is disposed around the outer periphery of the rotor 39 and the stator 40, and houses the rotor 39 and the stator 40 (examples of components of the electric motor 31).

[0037] A plurality of first cooling fins 42 protrude from the outer peripheral surface of the housing 36 at intervals in the circumferential direction of the housing 36. The plurality of first cooling fins 42 are formed integrally with the housing 36. Each first cooling fin 42 has a flat plate shape and extends in the front-to-rear direction. Each first cooling fin 42 extends continuously from the front end (one end in the front-to-rear direction) to the rear end (the other end in the front-to-rear direction) of the housing 36.

[0038] A plurality of fastening protrusions 43 protrude from the outer peripheral surface of the housing 36 at intervals in the circumferential direction of the housing 36. The multiple fastening protrusions 43 are provided between adjacent first cooling fins 42. A flow path P for cooling air is formed between adjacent first cooling fins 42 and each fastening protrusion 43, continuing from the front end to the rear end of the housing 36. The multiple fastening protrusions 43 are formed integrally with the housing 36.

[0039] Each fastening protrusion 43 is rod-shaped with a rectangular cross section and extends in the front-rear direction. That is, each fastening protrusion 43 extends parallel to each first cooling fin 42. Each fastening protrusion 43 extends continuously from the front end (one end in the front-rear direction) to the rear end (the other end in the front-rear direction) of the housing 36. Each fastening protrusion 43 is integrally formed from the same material from the front end (one end in the front-rear direction) to the rear end (the other end in the front-rear direction).

[0040] A first bolt hole 44 is provided at the front end of each fastening projection 43 for fastening the cover 37 to the housing 36. A second bolt hole 45 is provided at the rear end of each fastening projection 43 for fastening a casing 74 of the control device 32 (described later) to the housing 36. The first bolt hole 44 and the second bolt hole 45 extend in the front-to-rear direction.

[0041] The lid 37 is adjacent to the housing 36 and closes the opening on the front side of the housing 36 (the side opposite the control device 32). The lid 37 is disk-shaped and extends along a plane perpendicular to the front-to-rear direction. The lid 37 is formed separately from the housing 36. In other embodiments, the lid 37 may be formed integrally with the housing 36.

[0042] A plurality of first fastening pieces 47 protrude from the outer periphery of the cover 37 at intervals in the circumferential direction of the cover 37. A first fastening hole 48 is formed in each of the first fastening pieces 47 in the front-to-rear direction, and a first fastening bolt 49 passing through the first fastening hole 48 engages with the first bolt hole 44 of each fastening protrusion 43 of the housing 36, thereby fastening the cover 37 to the housing 36. A circular first through hole 51 is formed in the center of the cover 37 in the front-to-rear direction. A first bearing 52 is attached to the first through hole 51.

[0043] Referring to Figure 2, the shaft 38 extends in the front-rear direction (an example of a predetermined axial direction). The shaft 38 constitutes part of the rotary shaft 17 of the propulsion unit 7. Therefore, when the shaft 38 rotates, the entire rotary shaft 17 rotates, and the propulsion propeller 18 rotates integrally with the rotary shaft 17. This generates a forward thrust force in the aircraft 1, and the aircraft 1 propels forward. The shaft 38 extends along the propulsion direction of the aircraft 1 (see arrow X in Figure 2).

[0044] 5, the shaft 38 is hollow. The shaft 38 has a main body 55 accommodated in the housing 36, an extension 56 extending from the main body 55 toward the rear (toward the control device 32), and a protrusion 57 protruding from the main body 55 toward the front (the opposite side to the control device 32). The protrusion 57 passes through the first through-hole 51 of the cover 37 and extends to the space in front of the electric motor 31. The protrusion 57 is rotatably supported by the cover 37 via a first bearing 52.

[0045] 4 and 5, the rotor 39 is hollow. The rotor 39 is disposed on the outer periphery of the main body 55 of the shaft 38. The rotor 39 has a cylindrical rotor core 61 extending in the front-to-rear direction, a rotor plate 62 extending in the radial direction and connecting the main body 55 of the shaft 38 and the rotor core 61, and a plurality of permanent magnets 63 fixed to the outer periphery surface of the rotor core 61. The rotor core 61 and the rotor plate 62 are formed integrally with the shaft 38. The rotor plate 62 is provided with a plurality of communication holes 65 that penetrate in the front-to-rear direction.

[0046] The stator 40 is disposed on the outer periphery of the rotor 39 and faces the rotor 39 at a distance. The stator 40 includes a cylindrical stator core 67 extending in the front-rear direction, a plurality of teeth 68 protruding from the inner circumferential surface of the stator core 67, a plurality of coils 69 wound around the plurality of teeth 68, and three motor-side terminals 70 (an example of terminals on the rotating electric machine side) connected to the plurality of coils 69. The stator core 67 is fixed to the inner circumferential surface of the housing 36. The plurality of coils 69 generate the largest amount of heat among the components of the electric motor 31 and the control device 32. Therefore, the amount of heat generated by the electric motor 31 is greater than the amount of heat generated by the control device 32. The three motor-side terminals 70 correspond to the U-phase, V-phase, and W-phase of the three-phase AC, respectively.

[0047] <Control device 32> 3 and 4, the control device 32 is integrated with the electric motor 31 and controls the driving of the electric motor 31. In other words, the propulsion drive device 16 of this embodiment is an electromechanical integrated drive device.

[0048] 4 and 5, the control device 32 has a casing 74, a DC input connector 76, electronic components E, and a partition member 89. The electronic components E have, for example, three power modules, a smoothing capacitor, three current sensors, a communication connector 86 (see FIG. 3), a circuit board, a control board, etc.

[0049] 5, the casing 74 is adjacent to the housing 36 of the electric motor 31. The casing 74 is made of metal and has a cylindrical shape with a bottom. The casing 74 houses the electronic components E of the control device 32.

[0050] The casing 74 has a cylindrical circumferential wall portion 93 that extends in the front-to-rear direction around the outer periphery of the extension portion 56 of the shaft 38, and a bottom wall portion 94 that closes an opening on the rear side (the side opposite the electric motor 31) of the circumferential wall portion 93. Hereinafter, when the term "circumferential direction" is used in describing the components of the control device 32, it refers to the circumferential direction of the circumferential wall portion 93 of the casing 74 (in other words, the circumferential direction centered on the extension portion 56 of the shaft 38), and when the term "radial direction" is used in describing the components of the control device 32, it refers to the radial direction of the circumferential wall portion 93 of the casing 74 (in other words, the radial direction centered on the extension portion 56 of the shaft 38).

[0051] 3 and 4, a plurality of second cooling fins 96 protrude from the outer peripheral surface of the peripheral wall portion 93 of the casing 74 at intervals in the circumferential direction. The plurality of second cooling fins 96 are formed integrally with the peripheral wall portion 93. Each second cooling fin 96 has a flat plate shape and extends in the front-to-rear direction. Each second cooling fin 96 extends continuously from the front end (one end in the front-to-rear direction) of the peripheral wall portion 93 to the rear end (the other end in the front-to-rear direction).

[0052] 3 and 5, a plurality of second fastening pieces 97 protrude at intervals in the circumferential direction from the front end (the end on the electric motor 31 side) of the outer circumferential surface of the peripheral wall portion 93 of the casing 74. A second fastening hole 98 is provided in the front-rear direction in each second fastening piece 97, and second fastening bolts 99 passing through the second fastening holes 98 engage with the second bolt holes 45 of each fastening protrusion 43 of the housing 36, thereby fastening the casing 74 to the housing 36.

[0053] A plurality of third fastening pieces 101 protrude at intervals in the circumferential direction from the rear end (the end opposite the electric motor 31) of the outer peripheral surface of the peripheral wall portion 93 of the casing 74. Each third fastening piece 101 has a third fastening hole 102 formed in the front-rear direction.

[0054] The bottom wall 94 of the casing 74 is disk-shaped and extends along a plane perpendicular to the front-rear direction. The bottom wall 94 is formed separately from the peripheral wall 93. In other embodiments, the bottom wall 94 may be formed integrally with the peripheral wall 93.

[0055] A plurality of fourth fastening pieces 109 protrude at intervals in the circumferential direction from the outer periphery of the bottom wall portion 94 of the casing 74. Each fourth fastening piece 109 has a fourth fastening hole 110 formed in the front-to-rear direction, and third fastening bolts 111 passing through the fourth fastening holes 110 engage with third fastening holes 102 of each third fastening piece 101 of the peripheral wall portion 93, thereby fastening the bottom wall portion 94 to the peripheral wall portion 93.

[0056] A circular second through hole 113 is provided in the front-rear direction in the center of the bottom wall portion 94 of the casing 74. A second bearing 114 is attached to the second through hole 113. The extension portion 56 of the shaft 38 passes through the second through hole 113. The extension portion 56 of the shaft 38 is rotatably supported in the second through hole 113 via the second bearing 114. A first fitting hole 116 and a second fitting hole 117 are provided in the lower part of the bottom wall portion 94 at intervals in the circumferential direction.

[0057] The DC input connector 76 is connected to a DC power supply provided external to the propulsion drive unit 16. For example, the DC power supply may be a battery or a generator.

[0058] 3, the DC input connector 76 is fitted into a first fitting hole 116 in the bottom wall portion 94 of the casing 74, and passes through the bottom wall portion 94 of the casing 74. The communication connector 86 is fitted into a second fitting hole 117.

[0059] 5, the partitioning member 89 separates the internal space of the housing 36 from the internal space of the casing 74. The partitioning member 89 separates the rotor 39 and stator 40 of the electric motor 31 from the electronic components E of the control device 32. The partitioning member 89 is housed in the casing 74. In other embodiments, the partitioning member 89 may be housed in the housing 36 of the electric motor 31. The partitioning member 89 has a flat plate shape along a plane perpendicular to the front-to-rear direction. A shaft hole 216 is provided in the center of the partitioning member 89. The extension portion 56 of the shaft 38 passes through the shaft hole 216.

[0060] <Fan 33> 3 to 5, the fan 33 is disposed in front of the electric motor 31 (on one side in the front-rear direction). The fan 33 is disposed on the opposite side of the electric motor 31 from the control device 32. The fan 33 has a cylindrical hub portion 223 extending in the front-rear direction, a cylindrical rim portion 224 extending in the front-rear direction on the outer periphery of the hub portion 223, and a plurality of spokes 225 extending in the radial direction and connecting the hub portion 223 and the rim portion 224. A plurality of air blowing ribs 226 are provided on the outer circumferential surface of the rim portion 224 at intervals in the circumferential direction of the rim portion 224. Each air blowing rib 226 is inclined forward (on one side in the front-rear direction) toward the downstream side in the rotation direction R of the fan 33.

[0061] 4 and 5, the fan 33 is driven by the electric motor 31. Each propulsion drive unit 16 is provided with a clutch device 230 that connects or disconnects the driving force (rotational force of the shaft 38) transmitted from the electric motor 31 to the fan 33 in accordance with the external environment. The clutch device 230 is provided in a power transmission path from the electric motor 31 to the fan 33 and includes a clutch mechanism 231 configured to connect or disconnect the driving force. Specifically, the clutch mechanism 231 is provided between the hub portion 223 of the fan 33 and the protruding portion 57 of the shaft 38 of the electric motor 31, and selectively connects or disconnects the driving force of the electric motor 31 to the fan 33. When the clutch mechanism 231 is connected, the fan 33 rotates integrally with the shaft 38. On the other hand, when the clutch mechanism 231 is disconnected, the fan 33 does not rotate regardless of the rotation of the shaft 38. The configuration and operation of the clutch device 230 will be described in detail later.

[0062] <Duct Cover 34> 3 and 4, the duct cover 34 has a cylindrical shape extending in the front-rear direction. A cooling air passage 229 is formed between the duct cover 34 and the peripheral wall portion 93 of the housing 36 of the electric motor 31 and the casing 74 of the control device 32. That is, the cooling air passage 229 is formed on the outer periphery of the housing 36 of the electric motor 31 and the casing 74 of the control device 32. The cooling air passage 229 has a cylindrical shape and extends in the front-rear direction.

[0063] <Cooling of the electric motor 31 and the control device 32> 3 and 5, when the electric motor 31 is driven and the shaft 38 rotates while the clutch mechanism 231 is engaged, the fan 33 fixed to the protruding portion 57 of the shaft 38 rotates integrally with the shaft 38. As a result, the plurality of air-blowing ribs 226 of the fan 33 blow cooling air toward the outer peripheral surface of the housing 36 and the outer peripheral surface of the peripheral wall portion 93 of the casing 74. That is, the plurality of air-blowing ribs 226 of the fan 33 introduce cooling air into the cooling air passage 229.

[0064] The cooling air introduced into the cooling air passage 229 flows from the front side to the rear side along the outer periphery of the housing 36 and between the multiple first cooling fins 42. This allows the electric motor 31 to be cooled by the cooling air. Next, the cooling air flows from the front side to the rear side along the outer periphery of the peripheral wall portion 93 of the casing 74 and between the multiple second cooling fins 96. This allows the cooling air to cool the housing 36 of the control device 32. The cooling air that has passed through the outer periphery of the peripheral wall portion 93 of the casing 74 is discharged from the rear end of the cooling air passage 229 into the space behind the control device 32.

[0065] <Clutch device 230> Referring to FIG. 6, clutch device 230 has clutch mechanism 231 and air pressure difference operating mechanism 232 that switches between connection and disconnection of clutch mechanism 231 depending on the pressure difference between a reference air pressure that is kept substantially constant and the outside air pressure.

[0066] The clutch mechanism 231 has an inner ring member 233 coupled to the shaft 38 of the electric motor 31, and an outer ring member 234 disposed outside the inner ring member 233 and coupled to the hub portion 223 of the fan 33. The outer ring member 234 is supported by the inner ring member 233 by a third bearing 235 so as to be coaxial with the inner ring member 233 and rotatable relative to the inner ring member 233.

[0067] The inner ring member 233 is provided with a plurality of third through holes 236 (see FIG. 7 ) that extend generally radially and penetrate the inner ring member 233. A piston 237 is slidably disposed in each third through hole 236. In this embodiment, two pairs of third through holes 236, one pair on the upper side and one pair on the lower side, are formed in the inner ring member 233, and four pistons 237 are slidably supported in the inner ring member 233. The third through holes 236 in each pair are arranged parallel to each other. Each third through hole 236 functions as a guide hole that supports the corresponding piston 237 slidably in the radial direction. The shaft 38 has a hollow structure and defines an air pressure chamber 238 therein. The air pressure chamber 238 is in communication with the air pressure chamber 238 of the inner ring member 233 via the through holes formed in the shaft 38, and the pressure in the air pressure chamber 238 acts on the piston 237.

[0068] 1 and 2, one end of a connecting pipe 239 is connected to the shaft 38 to introduce the pressure inside the cabin of the aircraft 1 to the pressure chamber 238. One end of the connecting pipe 239 is connected to the shaft 38 via a known connector capable of introducing air pressure into the pressure chamber 238. The connector may be provided at the tip of the shaft 38 or at a longitudinal intermediate portion of the shaft 38. The other end of the connecting pipe 239 is connected to the fuselage 2 of the aircraft 1. The cabin of the aircraft 1 is maintained at approximately standard air pressure (1013.25 hPa), and this pressure is kept approximately constant even during flight of the aircraft 1. As a result, even when the aircraft 1 is flying at a high altitude, the pressure in the pressure chamber 238 inside the shaft 38 is kept approximately constant and can be used as a reference air pressure.

[0069] 6, the inner ring member 233 is provided with oscillating members 240, the number of which is the same as the number of pistons 237, so as to be oscillating about an axis parallel to the axis of the shaft 38. The oscillating members 240 have one end 240a located outward in the sliding direction of the pistons 237, and extend in the circumferential direction. The upper and lower pairs of oscillating members 240 are arranged so that the one ends 240a are close to each other, and have the other ends 240b facing in opposite circumferential directions (clockwise and counterclockwise in the figure). The inner ring member 233 is provided with first compression coil springs 242, the number of which is the same as the number of oscillating members 240, as biasing members that bias the other ends 240b of the oscillating members 240 radially outward. As a result, the other end 240b of the oscillating member 240 is constantly biased radially outward by the first compression coil spring 242, and under normal circumstances when the piston 237 is not driven by the pressure in the air pressure chamber 238, the other end 240b is brought into contact with the inner surface of the outer ring member 234.

[0070] The inner surface of the outer ring member 234 is formed with the same number of engagement recesses 244 (an example of engagement portions) as the number of the oscillating members 240. Each engagement recess 244 has an engagement surface that can engage with the other end 240b of the oscillating member 240. The engagement recesses 244 in this embodiment are circumferentially symmetrical in shape, with engagement surfaces on both circumferential sides. The four engagement recesses 244 have the same shape and are arranged rotationally symmetrical. Each engagement recess 244 can engage with either the upper or lower pair of oscillating members 240, and the four engagement recesses 244 simultaneously engage all four oscillating members 240. With this configuration, the clutch mechanism 231 can engage the hub portion 223 of the fan 33 with the shaft 38 at 90° intervals.

[0071] The configuration and operation of the air pressure difference actuation mechanism 232 will be described with reference to Figures 7 and 8. As shown in Figures 7(A) and 8(A), the piston 237 has a head 248 located radially outward of the third through-hole 236, a shaft portion 250 extending radially inward from the head 248, a flange 252 formed to protrude from the outer surface of the shaft portion 250, and a seal member 254 provided on the outer surface of the shaft portion 250. The seal member 254 is located radially inward (lower in the figure) than the flange 252 of the shaft portion 250. The seal member 254 is in close contact with the outer surface of the piston 237 and the inner surface of the third through-hole 236, sealing the air pressure chamber 238 from the external environment.

[0072] The head 248 of the piston 237 is exposed to the outside air. Meanwhile, the pressure of the air pressure chamber 238 acts on the radially inner portion of the third through-hole 236 relative to the seal member 254. As described above, the pressure inside the cabin of the aircraft 1 is kept roughly constant, and therefore, when the aircraft 1 is flying at a high altitude, the pressure difference between the cabin pressure used as the reference air pressure and the outside air pressure becomes large.

[0073] 7(B) and 8(B), when this pressure difference exceeds a predetermined threshold value during flight at high altitude, piston 237 slides radially outward, causing swinging member 240 to swing. This causes other end 240b of swinging member 240 to be released from engagement recess 244. The biasing force of first compression coil spring 242 is set so that air pressure difference actuated mechanism 232 can perform this operation. Piston 237, air pressure chamber 238, etc. constitute air pressure difference actuated mechanism 232, which switches between engagement and disengagement of clutch mechanism 231 depending on the pressure difference between a reference air pressure, which is kept approximately constant, and the outside air pressure.

[0074] When the aircraft 1 is flying at low altitude near the ground, the air pressure is close to standard atmospheric pressure and the outside temperature is higher than in the sky. Furthermore, when the aircraft 1 is flying at low altitude near the ground, it is often flying for takeoff and landing, so the propulsion drive device 16 of the propulsion unit 7 is often driven with a higher output than during cruising. Therefore, the electric motor 31 and the control device 32 are likely to reach high temperatures, and there is a strong need to cool them with the fan 33.

[0075] At this time, because the pressure difference between the cabin interior pressure and the outside air pressure is small, the piston 237 is returned radially inward of the inner ring member 233 by the swinging member 240 biased by the first compression coil spring 242, as shown in Figures 7(A) and 8(A). Note that when the electric motor 31 is stopped, the piston 237 may move toward the shaft 38 due to its own weight and separate from the swinging member 240, or may be held in a position in contact with the swinging member 240 by the frictional force of the seal member 254. The swinging member 240 engages with the engaging recess 244 of the outer ring member 234 due to the biasing force of the first compression coil spring 242. This puts the clutch mechanism 231 into an engaged state, and the fan 33 is driven to rotate integrally with the shaft 38 of the electric motor 31.

[0076] On the other hand, when the aircraft 1 is flying at high altitude, the outside air pressure and temperature are low. Furthermore, when the aircraft 1 is flying at high altitude, it often flies horizontally at a constant speed, so the propulsion drive device 16 of the propulsion unit 7 tends to be driven with an output lower than the rated output. Therefore, the electric motor 31 and the control device 32 are likely to be kept at low temperatures, and there is little need to cool them with the fan 33.

[0077] At this time, because the pressure difference between the cabin interior pressure and the outside air pressure is large, the piston 237 is pushed radially outward of the inner ring member 233 by the pressure difference, as shown in Figures 7(B) and 8(B). The swinging member 240 is driven to swing by the piston 237 against the biasing force of the first compression coil spring 242, and is released from the engaging recess 244 of the outer ring member 234. As a result, the clutch mechanism 231 is disengaged, and the fan 33 is stopped without being driven to rotate, regardless of the rotation of the shaft 38 of the electric motor 31.

[0078] In this way, the above differential pressure threshold is set so that the clutch mechanism 231 is disengaged during high-altitude flight when the differential pressure between the cabin pressure and the outside air pressure becomes large, and is engaged during low-altitude flight or ground operation when this differential pressure becomes small.

[0079] The propulsion drive unit 16 is configured as described above. Next, the effects of the propulsion drive unit 16 will be described.

[0080] The propulsion drive unit 16 is equipped with a clutch device 230 that connects and disconnects the driving force transmitted from the electric motor 31 to the fan 33 in response to the external environment. This allows the fan 33 to be switched between driving and stopping in response to the external environment, which changes depending on the flight environment of the aircraft 1. Therefore, under conditions where cooling of the electric motor 31 is not required, the clutch mechanism 231 disconnects the driving force and stops the fan 33, thereby reducing unnecessary power consumption. This also reduces a decrease in output of the electric motor 31 due to overcooling of the electric motor 31.

[0081] If the clutch device 230 uses an electronic control device that measures the external environment and switches the engagement and disengagement of the clutch mechanism 231, high-altitude measures such as countermeasures against electrical discharge and radiation are necessary. The clutch device 230 of this embodiment has an air pressure difference actuation mechanism 232 that switches the engagement and disengagement of the clutch mechanism 231 in accordance with the pressure difference between a reference air pressure, which is maintained substantially constant, and the outside air pressure. As a result, the engagement and disengagement of the clutch mechanism 231 are switched by the air pressure difference actuation mechanism 232, which is mechanically actuated in accordance with the pressure difference between the outside air pressure and the reference air pressure. Therefore, no high-altitude measures are required, and the configuration of the propulsion drive unit 16 is simplified. Furthermore, because the engagement and disengagement of the clutch mechanism 231 are switched in accordance with the outside air pressure, which changes with the flight altitude, the operation of the fan 33 can be switched in accordance with the flight altitude.

[0082] In this embodiment, the air pressure difference actuation mechanism 232 is configured to disengage the clutch mechanism 231 when the differential pressure obtained by subtracting the external air pressure from the reference air pressure is greater than a predetermined threshold, and to engage the clutch mechanism 231 when the differential pressure is less than the threshold. Therefore, the operation of the fan 33 is stopped at high altitudes where cooling of the electric motor 31 is not required, and the fan 33 operates at low altitudes such as on the ground. This ensures that the fan 33 operates when cooling of the electric motor 31 is required, and can be stopped at high altitudes where cooling is not required.

[0083] In this embodiment, the clutch mechanism 231 is provided to connect and disconnect the driving force between the shaft 38 of the electric motor 31 and the hub portion 223 of the fan 33. Therefore, there is no need to provide an additional member such as an extension shaft to provide the clutch mechanism 231. This allows for a simpler configuration of the propulsion drive unit 16.

[0084] Clutch mechanism 231 of this embodiment has piston 237 that is actuated by a pressure difference, oscillating member 240 journaled on inner ring member 233, and outer ring member 234 that has engagement recesses 244 with which oscillating member 240 engages when piston 237 is actuated. In other words, clutch mechanism 231 has piston 237 and oscillating member 240 that are actuated by a pressure difference, inner ring member 233 that supports them, and outer ring member 234 with which oscillating member 240 engages, allowing fan 33 to rotate. This makes it possible to realize clutch mechanism 231 with a small number of parts, thereby improving the reliability of the mechanism.

[0085] In this embodiment, the air pressure difference actuated mechanism 232 includes an air pressure chamber 238 formed inside the shaft 38 and holding a reference air pressure, and a connecting pipe 239 that connects the shaft 38 with the fuselage 2 of the aircraft 1 so as to introduce the cabin internal pressure to the air pressure chamber 238. In this way, by utilizing the cabin internal air pressure, it is possible to realize an air pressure difference actuated mechanism 232 with a simple configuration.

[0086] <<Variations>> The clutch mechanism 231 is not limited to the above-described configuration. Fig. 9 shows a modified example of the clutch mechanism 231. In this clutch mechanism 231, each pair of third through holes 236 is formed substantially radially rather than parallel to each other. With this configuration, the pistons 237 slide radially along the corresponding third through holes 236 and come into contact with the corresponding swinging members 240 substantially perpendicularly. Therefore, the driving force of the pistons 237 is efficiently transmitted to the swinging members 240, and the swinging members 240 are driven more smoothly.

[0087] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Figures 10 to 12. Elements that are the same as or similar to those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted.

[0088] 10 , the clutch device 230 of this embodiment is provided in a power transmission path from the electric motor 31 to the fan 33 and includes an electromagnetic clutch 260 configured to be able to connect and disconnect driving force, and a control device 270 that controls the electromagnetic clutch 260. Specifically, the electromagnetic clutch 260 is provided between the hub portion 223 of the fan 33 and the protruding portion 57 of the shaft 38 of the electric motor 31, and selectively connects and disconnects the driving force of the electric motor 31 to and from the fan 33.

[0089] The control device 270 may be incorporated into the control device 32 disposed behind the electric motor 31 of each propulsion drive unit 16, or may be provided separately from the control device 32. The control device 270 acquires the external air pressure from an external air pressure sensor 271 provided in the aircraft 1 and controls the engagement and disengagement of the electromagnetic clutch 260 based on the external air pressure. Specifically, when the external air pressure is higher than a predetermined pressure threshold, the electromagnetic clutch 260 is engaged, and when the external air pressure is lower than the predetermined pressure threshold, the electromagnetic clutch 260 is disengaged. When the control device 270 engages the electromagnetic clutch 260, the fan 33 rotates integrally with the shaft 38. On the other hand, when the control device 270 disengages the electromagnetic clutch 260, the fan 33 does not rotate regardless of the rotation of the shaft 38.

[0090] 11 shows the electromagnetic clutch 260 in more detail. An annular electromagnet 261 is fixed to the hub portion 223 of the fan 33, and an annular fixed plate 262 is arranged in front of the annular electromagnet 261 with a certain gap between them. In the gap formed between the annular electromagnet 261 and the annular fixed plate 262, an annular movable plate 263 is arranged so as to be movable in the front-rear direction.

[0091] An annular rotating plate 264 is interposed between the annular fixed plate 262 and the annular movable plate 263. The protruding portion 57 of the shaft 38 is inserted through the central openings of the annular electromagnet 261, the annular rotating plate 264, and the annular fixed plate 262. A spline is provided in the central opening of the annular rotating plate 264, and this spline meshes with a spline formed on the outer periphery of a hub member 265 fixed to the shaft 38. Therefore, the annular rotating plate 264 is engaged with the shaft 38 so as to be rotatable together with it and movable in the axial direction.

[0092] A plurality of second compression coil springs 266 are interposed between the annular movable plate 263 and the annular electromagnet 261. When the electromagnet 261 is not energized, the annular rotating plate 264 is sandwiched between the annular movable plate 263 and the annular fixed plate 262. As a result, the fan 33 is held unrotatable relative to the shaft 38, and the rotational output of the electric motor 31 is transmitted to the fan 33. Therefore, the fan 33 is driven when the electric motor 31 is operating.

[0093] When the aircraft 1 is operating at high altitude, the annular electromagnet 261 is energized by the control device 270. Therefore, as shown in Fig. 12, the magnetic attractive force of the annular electromagnet 261 causes the annular movable plate 263 to be pulled away from the annular rotating plate 264 against the biasing force of the second compression coil spring 266. As a result, the annular rotating plate 264 and the shaft 38 become rotatable relative to the electromagnet 261, and the rotational output of the electric motor 31 is not transmitted to the fan 33. Therefore, the fan 33 is not driven even when the electric motor 31 is operating.

[0094] When the aircraft 1 is on the ground or flying at a low altitude near the ground, the external air pressure is higher than a predetermined pressure threshold, so the control device 270 does not energize the electromagnet 261 and keeps the electromagnetic clutch 260 in an engaged state. That is, as shown in FIG. 11 , the annular movable plate 263 receives the biasing force of the second compression coil spring 266 and is pressed against the annular rotating plate 264, thereby holding the annular rotating plate 264. As a result, the fan 33 cannot rotate relative to the shaft 38. In this way, when the aircraft 1 is operating at a low altitude, the fan 33 is driven by the electric motor 31 to cool the electric motor 31.

[0095] On the other hand, when the aircraft 1 is flying at a high altitude, the external air pressure becomes lower than a predetermined pressure threshold, so the control device 270 energizes the electromagnet 261 and disengages the electromagnetic clutch 260. That is, as shown in FIG. 12 , the annular movable plate 263 is attracted by the annular electromagnet 261, and the annular rotating plate 264 becomes rotatable. As a result, the fan 33 becomes rotatable relative to the shaft 38. In this way, when the aircraft 1 is flying at a high altitude, the fan 33 is not driven regardless of the operation of the electric motor 31, and does not cool the electric motor 31.

[0096] The clutch device 230 of this embodiment is configured as described above. That is, the clutch device 230 includes an electromagnetic clutch 260 provided in a power transmission path from the electric motor 31 to the fan 33, and a control device 270 that acquires information about the external environment and controls the engagement and disengagement of the electromagnetic clutch 260. In this way, the electromagnetic clutch 260 is used as the clutch, and the control device 270 acquires information about the external environment and electrically controls the engagement and disengagement of the clutch, so that the engagement and disengagement of the clutch can be controlled more precisely in accordance with various conditions of the external environment. This makes it possible to more appropriately control the operation of the fan 33.

[0097] The electromagnetic clutch 260 is provided to connect and disconnect the driving force between the shaft 38 of the electric motor 31 and the hub portion 223 of the fan 33. This eliminates the need to provide an additional member such as an extension shaft in order to provide the electromagnetic clutch 260, thereby simplifying the configuration.

[0098] In the above embodiment, the inner rotor type electric motor 31 is an example of a rotating electric machine. In other embodiments, an outer rotor type electric motor may be an example of a rotating electric machine.

[0099] In the above embodiment, the configuration of the present invention is applied to the propulsion drive device 16. In other embodiments, the configuration of the present invention may be applied to the lift drive device 12.

[0100] In the above embodiment, the configuration of the present invention is applied to an electric vertical take-off and landing aircraft. In other embodiments, the configuration of the present invention may be applied to an aircraft other than an electric vertical take-off and landing aircraft (i.e., a general aircraft that cannot take off and land vertically).

[0101] In the first embodiment, the air pressure chamber 238 is connected to the cabin by the connecting pipe 239. In another embodiment, a pressure sensor may be provided in the air pressure chamber 238, and the air pressure chamber 238 may be connected via the connecting pipe 239 to a compressor that is driven in accordance with the detected value of the pressure sensor.

[0102] In the first embodiment, the clutch mechanism 231 is switched between connected and disconnected states by the air pressure difference actuating mechanism 232. In other embodiments, the clutch mechanism 231 may be switched between connected and disconnected states by a mechanism that operates based on an external environment other than the air pressure difference, such as temperature, sunlight conditions, etc. Also, in the second embodiment, the control device 270 controls the electromagnetic clutch 260 based on the external air pressure. In other embodiments, the control device 270 may control the electromagnetic clutch 260 based on an external environment other than the external air pressure, such as temperature, sunlight conditions, etc.

[0103] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be modified in a wide range of ways. [Explanation of symbols]

[0104] 1 :Aircraft 2: Torso 12: Lifting drive unit 16: Propulsion drive unit (electric drive unit for aircraft) 17: Rotation axis 31: Electric motor (an example of a rotating electrical machine) 32: Control device 33: Fan 38: Shaft 57: Protrusion 223: Hub part 230: Clutch device 231: Clutch mechanism 232: Pressure difference actuation mechanism 233: Inner ring member 234: Outer ring member 237: Piston 238: Pressure chamber 239: Connecting pipe 240: Swinging member 244: Engagement recess (an example of an engagement portion) 260: Electromagnetic clutch 270: Control device

Claims

1. a rotating electric machine that drives a rotor that generates lift or thrust; a fan driven by the rotating electric machine and generating cooling air for cooling the rotating electric machine, The electric drive system for an aircraft further comprises a clutch device that connects and disconnects the driving force transmitted from the rotating electric machine to the fan in accordance with an external environment.

2. The clutch device is a clutch mechanism provided in a power transmission path from the rotary electric machine to the fan, the clutch mechanism being configured to be able to connect and disconnect the driving force; 2. The electric drive system for an aircraft according to claim 1, further comprising: a pressure difference actuation mechanism that switches between connection and disconnection of the clutch mechanism in accordance with a pressure difference between a reference atmospheric pressure that is maintained constant and an external atmospheric pressure.

3. 3. The electric drive device for an aircraft according to claim 2, wherein the air pressure difference actuation mechanism is configured to disengage the clutch mechanism when the differential pressure obtained by subtracting the external air pressure from the reference air pressure is greater than a predetermined threshold, and to engage the clutch mechanism when the differential pressure is smaller than the threshold.

4. 4. The electric drive system for an aircraft according to claim 2, wherein the clutch mechanism is provided to connect and disconnect the driving force between the shaft of the rotating electric machine and a hub of the fan.

5. The clutch mechanism includes: a piston that operates in response to the pressure difference between the external atmospheric pressure and the reference atmospheric pressure; an inner ring member coupled to the shaft and slidably supporting the piston; a swinging member journaled on the inner ring member; 5. The electric drive device for an aircraft according to claim 4, further comprising: an outer ring member coupled to the hub of the fan and having an engagement portion with which the swinging member engages when the piston is actuated.

6. The air pressure difference actuation mechanism is an air pressure chamber formed inside the shaft and holding the reference air pressure to be applied to the piston; 6. The electric drive device for an aircraft according to claim 5, further comprising: a connecting pipe that connects the shaft to a fuselage of the aircraft so as to introduce cabin pressure in the aircraft in which the electric drive device is installed to the air pressure chamber.

7. The clutch device is an electromagnetic clutch provided in a power transmission path from the rotating electric machine to the fan; 2. The electric drive system for an aircraft according to claim 1, further comprising: a control device that acquires the external environment and controls the connection and disconnection of the electromagnetic clutch.

8. 8. The electric drive system for an aircraft according to claim 7, wherein the electromagnetic clutch is provided to connect and disconnect the driving force between the shaft of the rotating electric machine and a hub of the fan.

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