Aircraft propulsion system

Abstract

This aircraft propulsion system comprises: a plurality of electric motors; a propeller having a plurality of blades capable of changing a pitch angle; a gear box for reducing the rotation speed of the plurality of electric motors and transmitting the rotation to the propeller; an actuator that changes a pitch angle of the blades; a pump driven by power transmitted from the gear box and supplying oil to the gear box; a heat exchanger that cools the oil by using a gas and / or a liquid as a refrigerant; and a circulation path for circulating the oil between the gear box and the heat exchanger.

Description

Aircraft Propulsion Systems

[0001] The present disclosure relates to aircraft propulsion systems.

[0002] Patent document 1 discloses a propulsion system for an aircraft, which is driven by an electric motor powered by a battery.

[0003] U.S. Patent Publication No. 11420761

[0004] When an aircraft propulsion system uses an electric motor for propulsion, it is necessary to install auxiliary equipment. In this type of propulsion system, it is desirable to suppress an increase in weight even while installing the auxiliary equipment.

[0005] Therefore, one aspect of the present disclosure aims to provide an aircraft propulsion system that can suppress weight increase even while mounting auxiliary equipment.

[0006] An aircraft propulsion system according to one aspect of the present disclosure includes a plurality of electric motors, a propeller having a plurality of blades whose pitch angle can be changed, a gearbox that reduces the rotation of the plurality of electric motors and transmits the rotation to the propeller, an actuator that changes the pitch angle of the blades, a pump that is driven by power transmitted from the gearbox and supplies oil to the gearbox, a heat exchanger that cools the oil using at least one of a gas or a liquid as a refrigerant, and a circulation path through which oil circulates between the gearbox and the heat exchanger.

[0007] According to one aspect of the present disclosure, it is possible to provide an aircraft propulsion system that can suppress an increase in weight even when an auxiliary device is mounted.

[0008] FIG. 1 is a perspective view of an aircraft equipped with a propulsion system according to a first embodiment. FIG. 2 is a block diagram of the propulsion system of the aircraft of FIG. 1. FIG. 3 is a perspective view of the configuration in the vicinity of the gearbox in the propulsion system of FIG. 2. FIG. 4 is a front view of the configuration in the vicinity of the gearbox in the propulsion system of FIG. 2. FIG. 5 is a rear view of the configuration in the vicinity of the gearbox in the propulsion system of FIG. 2. FIG. 6 is a side view of the configuration in the vicinity of the gearbox in the propulsion system of FIG. 2. FIG. 7 is a side sectional view of the configuration in the vicinity of the gearbox in the propulsion system of FIG. 2. FIG. 8 is a block diagram of a propulsion system of an aircraft according to a second embodiment. FIG. 9 is a block diagram of a propulsion system of an aircraft according to a third embodiment. FIG. 10 is a block diagram of a propulsion system of an aircraft according to a fourth embodiment. FIG. 11 is a block diagram of a propulsion system of an aircraft according to a fifth embodiment.

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the following description, "forward" means the side on which the propeller is disposed in the axial direction of the propeller's rotation shaft of the propeller of the propulsion system, and "rearward" means the side opposite to the side on which the propeller is disposed in the axial direction of the propeller's rotation shaft. The direction perpendicular to the axial direction of the propeller's rotation shaft will be referred to as the "radial direction" and will be assigned the symbol R. "Side" means the radially outward side of the propulsion system.

[0010] First Embodiment FIG. 1 is a perspective view of an aircraft 1 equipped with a propulsion system 10A according to a first embodiment. The aircraft 1 is a propeller aircraft equipped with multiple propellers 11. The aircraft 1 has a fuselage 2, a pair of left and right main wings 3, and a tail 4. The fuselage 2 extends in the longitudinal direction. The pair of left and right main wings 3 are attached near the center of the fuselage 2 in the longitudinal direction. The tail 4 is attached to the rear end of the fuselage 2. The pair of left and right main wings 3 extend to the left and right, respectively. Two nacelles 5 are attached to the bottom of each main wing 3. The two nacelles 5 are arranged with a gap between them in the lateral direction. A propulsion system 10A that generates thrust for the aircraft 1 is arranged in each nacelle 5.

[0011] The propulsion system 10A includes a propeller 11 and a drive unit 20 that drives the propeller 11. The propeller 11 has a hub 11a and a plurality of blades 11b supported by the hub 11a. The plurality of blades 11b extend from the hub 11a in the radial direction R. The propeller 11 is disposed in front of the nacelle 5. The drive unit 20 is disposed behind the propeller 11. The drive unit 20 is disposed within the nacelle 5.

[0012] (Overall Configuration of Propulsion System) Figure 2 is a block diagram of the propulsion system 10A of the aircraft 1 in Figure 1. The drive unit 20 includes a plurality of electric motors 22 and a gearbox 23. The plurality of electric motors 22 are driven by power supplied from a battery 21 via a power line 25. The number of the plurality of electric motors 22 is, for example, four, but is not limited to this. The battery 21 is, for example, a fuel cell or a storage battery. The fuel cell generates power through an electrochemical reaction between hydrogen as fuel and oxygen.

[0013] The gearbox 23 is disposed in a power transmission path between the plurality of electric motors 22 and the propeller 11. The gearbox 23 constitutes a reducer and reduces the rotation of the plurality of electric motors 22 before transmitting the rotation to the propeller 11. A clutch 24 is interposed between the gearbox 23 and the electric motor 22. The gearbox 23 has a plurality of input shafts 71 corresponding to the plurality of electric motors 22, respectively, and the input shafts 71 are connected to the clutch 24. The clutch 24 is also connected to the output shaft 22a of the electric motor 22.

[0014] The clutch 24 is, for example, a sprag-type one-way clutch, but may be another type of clutch. The clutch 24 is configured to permit torque transmission from the output shaft 22 a of the electric motor 22 to the input shaft 71 of the gearbox 23, and to prohibit torque transmission from the input shaft 71 of the gearbox 23 to the output shaft 22 a of the electric motor 22. Therefore, when one of the multiple electric motors 22 is stopped, power is prevented from being transmitted from the gearbox 23 to the stopped electric motor 22. Note that examples of when one of the multiple electric motors 22 is stopped include when some of the multiple electric motors 22 are powered off to reduce propeller output, or when a malfunction occurs in one of the multiple electric motors 22.

[0015] The gearbox 23 has an output shaft 72. The propeller 11 is connected to the output shaft 72. The hub 11a may be directly connected to the front end of the output shaft 72, or may be indirectly connected via another shaft member. The detailed configuration of the gearbox 23 will be described later.

[0016] (Lubrication Device) The propulsion system 10A includes a lubrication device 40. The lubrication device 40 supplies lubricating oil to a plurality of gears included in the gear box 23. The lubrication device 40 includes an oil tank 41, a first pump 42, a heat exchanger 43, and a circulation path 44. The oil tank 41 stores oil. The oil stored in the oil tank 41 is, for example, lubricating oil supplied to the gear box 23.

[0017] The first pump 42 supplies lubricating oil stored in an oil tank 41 to the gearbox 23, for example. The first pump 42 is driven by power transmitted from the gearbox 23. The first pump 42 supplies oil to the gearbox 23 at a pressure different from the pressure of oil supplied to the actuator 34 by a second pump 32 (described later). The first pump 42 supplies oil to the gearbox 23 at a pressure lower than the pressure of oil supplied to the actuator 34 by the second pump 32, for example. The second pump 32 and the first pump 42 may also be referred to as a high-pressure pump and a low-pressure pump, respectively. The lubrication device 40 is, for example, a dry sump type, and the oil tank 41 and the first pump 42 are disposed outside the gearbox 23.

[0018] The heat exchanger 43 cools the oil flowing through the circulation path 44. The heat exchanger 43 is, for example, an air-cooled type. An air intake 5a is arranged in the nacelle 5 of the aircraft 1 (see FIG. 1 ). The heat exchanger 43 cools the oil using air that flows in from the air intake 5a as a refrigerant. The air intake 5a is arranged, for example, on the outer wall of the nacelle 5, but may also be arranged in the center of the propeller 11 or in the periphery of the propeller 11.

[0019] The oil tank 41, the first pump 42, the heat exchanger 43, and the gear box 23 are arranged in a circulation path 44. Oil circulates between the gear box 23 and the heat exchanger 43 through the circulation path 44. That is, when the first pump 42 is driven, the lubricating oil stored in the oil tank 41 is supplied to the gear box 23. The lubricating oil is heated as it passes through the gear box 23, flows out of the gear box 23, and is sent to the heat exchanger 43 where it is cooled, and then returned to the oil tank 41.

[0020] (Pitch Change Device) The propulsion system 10A includes a pitch change device 30 that changes the pitch of the blades 11b. That is, the propeller 11 is a variable pitch propeller that can change the pitch angle of the blades 11b.

[0021] The pitch change device 30 has an oil tank 31, a second pump 32, a control valve 33, an actuator 34, and a pitch change mechanism 35. In this embodiment, the actuator 34 is a hydraulic actuator, but is not limited to this. The oil tank 31 stores oil. The oil stored in the oil tank 31 is, for example, hydraulic oil used as a power transmission medium in the actuator 34. It is sufficient that the pitch change device 30 includes at least either the actuator 34 or the control valve 33.

[0022] The second pump 32 is disposed in a circulation path 36 between the oil tank 31 and the actuator 34. The second pump 32 supplies, for example, hydraulic oil stored in the oil tank 31 to the actuator 34 via the circulation path 36. The second pump 32 is driven by power transmitted from the gear box 23. The oil tank 31 and the second pump 32 are disposed outside the gear box 23.

[0023] The control valve 33 controls the operation of the actuator 34. The control valve 33 is disposed in an oil passage between the discharge port of the second pump 32 and the actuator 34. The control valve 33 changes its opening degree and adjusts the pressure of the hydraulic oil supplied to the actuator 34, based on a control command received from a controller disposed on the aircraft 2, for example.

[0024] The actuator 34 changes the pitch angle of the blades 11b. The actuator 34 is, for example, a hydraulic cylinder. When the actuator 34 is a hydraulic cylinder, the actuator 34 has at least one hydraulic chamber, a piston that is displaced along the rotation axis of the propeller 11 by the pressure of the hydraulic chamber, and a rod that is displaced together with the piston. The movement of the rod is transmitted to a pitch change mechanism 35 in the hub 11a of the propeller 11 via a rod-shaped body that extends inside the gearbox 23 along the rotation axis of the propeller 11. The control valve 33 is, for example, a directional control valve that can switch the supply destination of hydraulic oil between a rod-side hydraulic chamber and a head-side hydraulic chamber included in the actuator 34 based on a control command received from a controller disposed on the aircraft 2.

[0025] The pitch change mechanism 35 is disposed within the hub 11a of the propeller 11 and converts the movement of the rod of the actuator 34 into rotational movement of the blades 11b about the longitudinal axis. The pitch change mechanism 35 may be disposed outside the hub 11a of the propeller 11. The actuator 34 drives the plurality of blades 11b via the pitch change mechanism 35 so as to achieve a pitch that corresponds to the pressure of the supplied hydraulic oil.

[0026] (Cooling Device) The propulsion system 10A includes cooling devices 50 and 60.

[0027] The cooling device 50 cools the multiple electric motors 22. The cooling device 50 has a water tank 51, a water pump 52, a heat exchanger 53, and a circulation path 54. The water tank 51 stores water to be used as cooling water. Note that the cooling device 50 can use liquids other than water. The water tank 51 can store liquids other than water.

[0028] The water pump 52 supplies water stored in the water tank 51 to the plurality of electric motors 22. The water pump 52 may be an electric or mechanical pump.

[0029] The heat exchanger 53 cools the water flowing through the circulation path 54. The heat exchanger 53 is, for example, an air-cooled type. An air intake 5a is arranged in the nacelle 5 of the aircraft 1. The air intake 5a is arranged, for example, on the outer wall of the nacelle 5, but may also be arranged in the center of the propeller 11 or in the periphery of the propeller 11. The heat exchanger 53 cools the water that has flowed into the heat exchanger 53 using the air that has flowed in from the air intake 5a as a refrigerant.

[0030] The water tank 51, the water pump 52, the heat exchanger 53, and the electric motors 22 are arranged in a circulation path 54. Cooling water circulates between the electric motors 22 and the heat exchanger 53 through the circulation path 54. That is, when the water pump 52 is driven, water stored in the water tank 51 is supplied to the electric motors 22. In FIG. 2 , the circulation path 54 includes a series of flow paths that supply water to the electric motors 22, but the circulation path 54 is not limited to this. For example, the circulation path 54 may include a plurality of parallel branch paths that branch off from a water path extending from the water pump 52 and connect to the electric motors 22. The cooling water is heated by passing through the electric motors 22, and after passing through the electric motors 22, is sent to the heat exchanger 53 where it is cooled and then returned to the water tank 51.

[0031] The cooling device 60 cools the battery 21. The cooling device 60 has a water tank 61, a water pump 62, a heat exchanger 63, and a circulation path 64. The water tank 61 stores water to be used as cooling water.

[0032] The water pump 62 supplies water stored in the water tank 61 to the battery 21. The water pump 62 may be, for example, an electric or mechanical type.

[0033] The heat exchanger 63 cools the water flowing through the circulation path 64. The heat exchanger 63 is, for example, an air-cooled type. An air intake 5a is arranged in the nacelle 5 of the aircraft 1. The air intake 5a is arranged, for example, on the outer wall of the nacelle 5, but may also be arranged in the center of the propeller 11 or in the periphery of the propeller 11. The heat exchanger 63 cools the water that has flowed into the heat exchanger 63 using the air that has flowed in from the air intake 5a as a refrigerant.

[0034] The water tank 61, water pump 62, heat exchanger 63, and battery 21 are arranged in a circulation path 64. Cooling water circulates between the battery 21 and the heat exchanger 63 through the circulation path 64. That is, when the water pump 62 is driven, water stored in the water tank 61 is supplied to the battery 21. The cooling water is heated as it passes through the battery 21, and after passing through the battery 21, it is sent to the heat exchanger 63 where it is cooled, and then returned to the water tank 61.

[0035] Next, details of the gearbox 23 will be described with reference to Figures 3 to 7. Figure 3 is a perspective view of the configuration in the vicinity of the gearbox 23 in the propulsion system 10A of Figure 2. Figure 4 is a front view of the configuration in the vicinity of the gearbox 23 in the propulsion system 10A of Figure 2. Figure 5 is a rear view of the configuration in the vicinity of the gearbox 23 in the propulsion system 10A of Figure 2. Figure 6 is a side view of the configuration in the vicinity of the gearbox 23 in the propulsion system 10A of Figure 2. Figure 7 is a side cross-sectional view of the configuration in the vicinity of the gearbox 23 in the propulsion system 10A of Figure 2.

[0036] The gearbox 23 includes a housing 73 that houses a plurality of gears. As shown in Fig. 3, the housing 73 has a generally truncated cone shape that decreases in diameter toward the front along the rotation axis X1 of the propeller 11. The housing 73 includes, for example, a first cylindrical portion 73a, a second cylindrical portion 73b, a rear surface portion 73c, and two semi-cylindrical portions 73d. The first cylindrical portion 73a, the second cylindrical portion 73b, the rear surface portion 73c, and the two semi-cylindrical portions 73d define a gear housing space S.

[0037] As shown in Figure 7, the first cylindrical portion 73a is open in the front-rear direction. The first cylindrical portion 73a is a generally hollow truncated cone whose center line coincides with the rotational axis X1 of the propeller 11. The output shaft 72 of the gearbox 23 protrudes forward so as to pass through the front opening of the first cylindrical portion 73a. The diameter of the first cylindrical portion 73a increases as it extends rearward.

[0038] The second cylindrical portion 73b is open in the front-rear direction and has a generally cylindrical shape whose center line coincides with the rotation axis X1 of the propeller 11. The front opening edge of the second cylindrical portion 73b is connected to the rear opening edge of the first cylindrical portion 73a.

[0039] The rear surface portion 73c is connected to the edge of the rear opening of the second cylindrical portion 73b so as to close the rear opening of the second cylindrical portion 73b. The rear surface portion 73c has a disk shape and has a plurality of openings.

[0040] As shown in FIG. 4 , two semi-cylindrical portions 73d are connected to the second cylindrical portion 73b. Each semi-cylindrical portion 73d has a generally semi-cylindrical shape with its center line parallel to the rotation axis X1 of the propeller 11. The semi-cylindrical portions 73d are hollow and open to the second cylindrical portion 73b. The two semi-cylindrical portions 73d form a space for accommodating at least a portion of pump drive gears 91 and 92 (described below). The space enclosed by the semi-cylindrical portions 73d communicates with the interior space of the second cylindrical portion 73b. The second cylindrical portion 73b has two openings on its sides, which are closed by the two semi-cylindrical portions 73d.

[0041] A mount frame 26 for supporting the gearbox 23 within the nacelle 5 is fixed to the housing 73. The mount frame 26 includes an annular fixed frame 26a and a plurality of support frames 26b that connect the fixed frame 26a to the housing 73. The fixed frame 26a is located rearward of the gearbox 23, and the plurality of support frames 26b extend forward from the fixed frame 26a toward the housing 73 of the gearbox 23. A front end of the support frame 26b is fixed to a mount support portion 73e that protrudes outward in the radial direction R from the second cylindrical portion 73b.

[0042] As shown in FIG. 5 , the electric motors 22 are arranged at equal intervals in the circumferential direction around the rotational axis X1 of the propeller 11, aft of the gearbox 23. As shown in FIG. 5 , the electric motors 22 are equidistant from the rotational axis X1 of the propeller 11. Note that the circumferential intervals and distances of the electric motors 22 around the rotational axis X1 of the propeller 11 do not have to be equal. As shown in FIG. 6 , the rotational axis X2 of each electric motor 22 is parallel to the rotational axis X1 of the propeller 11. Note that the rotational axis X2 of each electric motor 22 does not have to be parallel to the rotational axis X1 of the propeller 11. When the propulsion system 10A is viewed from the front in a direction along the rotational axis X1 of the propeller 11, the electric motors 22 overlap all or part of the gearbox 23. At least a portion of the electric motor 22 is disposed radially inward from the outermost end of the housing 73 in the radial direction R. In this embodiment, the rotation axis X2 of the electric motor 22 is disposed radially inward of the outermost end of the housing 73 in the radial direction R. The outermost end of the housing 73 in the radial direction R is the part of the housing 73 that is located farthest from the rotation axis X1 of the propeller 11 when viewed in the direction along the rotation axis X1 of the propeller 11. In this embodiment, the outermost end of the housing 73 in the radial direction R is part of the side surface of the semi-cylindrical portion 73d.

[0043] 5 , at least one electric motor 22 of the multiple motors is disposed within the nacelle 5 such that a gap between the at least one electric motor 22 and the nacelle 5 is equal to or greater than a predetermined value when viewed in a direction along the rotational axis X1 of the propeller 11. The predetermined value is, for example, 50 cm, and preferably equal to or greater than 40 cm. By ensuring a predetermined gap between the electric motor 22 and the nacelle 5, repair or replacement of the electric motor 22 within the nacelle 5 becomes easier.

[0044] For example, in the present embodiment, the gap between the at least one electric motor 22 and the nacelle 5 may be equal to or greater than the predetermined value in a cross section perpendicular to the rotation axis X1 of the propeller 11. The cross section perpendicular to the rotation axis X1 of the propeller 11 may be a cross section passing through the at least one electric motor 22 or a cross section passing through the support frame 26b.

[0045] 5, in this embodiment, the inner peripheral surface of the nacelle 5 coincides with the outer peripheral surface of the fixed frame 26a when viewed in the direction along the rotation axis X1 of the propeller 11. The gap between the at least one electric motor 22 and the abutting portion of the nacelle 5 with the mount frame 26 when viewed in the direction along the rotation axis X1 of the propeller 11 may be equal to or greater than the predetermined value.

[0046] It is preferable that the distance t1 between the rotation axis X2 of the electric motor 22 and the outer end of the mount frame 26 in the radial direction R is greater than the distance t2 between the rotation axis X1 of the propeller 11 and the rotation axis X2 of the electric motor 22. Making the distance t1 greater than the distance t2 makes it easier to repair or replace the electric motor 22 inside the nacelle 5.

[0047] As shown in Fig. 3, the first pump 42 and the oil tank 41 are disposed outside the housing 73 of the gearbox 23. Furthermore, the second pump 32 and the oil tank 31 are disposed outside the housing 73 of the gearbox 23. As shown in Fig. 4, the first pump 42 and the second pump 32 overlap with the gearbox 23 when viewed in the direction along the rotational axis X1 of the propeller 11. Furthermore, the first pump 42 and the second pump 32 overlap with the gearbox 23 when viewed in the radial direction R.

[0048] 6 , the first pump 42 and the second pump 32 are disposed outward from the gearbox 23 in the radial direction R. The first pump 42, the second pump 32, and the gearbox 23 are disposed so as to intersect with an imaginary plane perpendicular to the rotational axis X1 of the propeller 11. The first pump 42 overlaps with the first cylindrical portion 73a of the housing 73 when viewed in the radial direction R. Although not shown, the second pump 32 overlaps with the first cylindrical portion 73a of the housing 73 when viewed in the radial direction R.

[0049] At least a portion of the pitch change device 30 is disposed rearward of the gearbox 23. At least a portion of the pitch change device 30 is disposed on the rotational axis X1 of the propeller 11. At least a portion of the pitch change device 30 is disposed inward in the radial direction R from the multiple electric motors 22. Specifically, as shown in FIG. 6 , the control valve 33 and the actuator 34 in the pitch change device 30 are configured as a single unit, and this unit is connected to a back surface portion 73c of the housing 73. The control valve 33 and the actuator 34 are disposed inward in the radial direction R from the multiple electric motors 22. The control valve 33 and the actuator 34 are disposed on the rotational axis X1 of the propeller 11.

[0050] A portion of the actuator 34 may extend into the gearbox housing 73. For example, the hydraulic chamber and piston of the actuator 34 may be located rearward of the rearmost end of the housing 73, and the rod of the actuator 34 may pass through an opening in the rear portion 73 c, with the rod partially extending into the housing 73.

[0051] The actuator 34 may be disposed radially inward of the rotational axis X2 of the electric motors 22. The rearmost end of the actuator 34 may be located forward of the rearmost ends of the electric motors 22. The rearmost end of the control valve 33 may be located forward of the rearmost ends of the electric motors 22.

[0052] Either or both of the control valve 33 and the actuator 34 do not have to be located inside the plurality of electric motors 22 in the radial direction R. Furthermore, either or both of the control valve 33 and the actuator 34 do not have to be located on the rotation axis X1 of the propeller 11.

[0053] (Details of the Gearbox) As shown in FIG. 7 , the housing 73 of the gearbox 23 accommodates a plurality of pinion gears 81 , a first sun gear 82 , a second sun gear 83 , a transmission shaft 84 , a plurality of planetary gears 85 , a ring gear 86 , and a planetary carrier 87 .

[0054] The number of the pinion gears 81 is the same as the number of the electric motors 22. The pinion gears 81 are fixed to the input shaft 71 that is driven by the electric motor 22. The pinion gears 81 are positioned equidistant from the rotation axis X1 of the propeller 11.

[0055] The first sun gear 82 is disposed radially inward of the multiple pinion gears 81 in the radial direction R, which is perpendicular to the rotation axis X1 of the propeller 11. The center of the first sun gear 82 is located on the rotation axis X1 of the propeller 11. The multiple pinion gears 81 engage with the first sun gear 82. The diameter of the first sun gear 82 is relatively large so that it can engage with the multiple pinion gears 81. For example, the diameter of the first sun gear 82 is 50% or more of the diameter of the second cylindrical portion 73b of the housing 73.

[0056] The second sun gear 83 is disposed in front of the first sun gear 82. The center of the second sun gear 83 is located on the rotational axis X1 of the propeller 11. The transmission shaft 84 extends along the rotational axis X1 of the propeller 11. The transmission shaft 84 has a first end which is the rear end and a second end which is the front end, with the first sun gear 82 fixed to the first end and the second sun gear 83 fixed to the second end. In this manner, the first sun gear 82 and the second sun gear 83 are connected by the transmission shaft 84. The transmission shaft 84 is, for example, cylindrical and open in the front-rear direction, and a portion of the pitch change device 30 can pass inside the transmission shaft 84.

[0057] The planetary gear 85 is disposed radially outward of the second sun gear 83 in the radial direction R that is perpendicular to the rotation axis X1 of the propeller 11. The planetary gear 85 engages with the second sun gear 83.

[0058] The ring gear 86 is disposed radially outward of the planetary gears 85 in a radial direction R that is perpendicular to the rotation axis X1 of the propeller 11. The ring gear 86 is engaged with the planetary gears 85.

[0059] The planetary carrier 87 has a generally hollow truncated cone shape that decreases in diameter as it moves forward along the rotational axis X1 of the propeller 11. The planetary carrier 87 is connected to the plurality of planetary gears 85. The planetary carrier 87 rotates together with the plurality of planetary gears 85 about the rotational axis X1 of the propeller 11.

[0060] Specifically, planetary gear 85 has bearings 85a that support a carrier shaft, and the carrier shaft supported by each bearing 89a is fixed to the rear end of planetary carrier 87. Therefore, planetary gear 85 rotates on its axis due to the rotation of second sun gear 83, while revolving around second sun gear 83 along ring gear 86. As planetary gear 85 revolves around rotation axis X1 of propeller 11, planetary carrier 87, which is connected to planetary gear 85 via a carrier shaft, rotates around rotation axis X1.

[0061] The front end of the planetary carrier 87 is connected to the rear end of the output shaft 72, which extends in the front-to-rear direction. The output shaft 72 is supported by a bearing fixed to the housing 73. The output shaft 72 protrudes forward from the housing 73. The propeller 11 is connected to the front end of the output shaft 72.

[0062] With the above configuration, in the gearbox 23 of this embodiment, two stages of speed reduction are performed in the process of power transmission from the input shaft 71 to the output shaft 72. That is, the first stage of speed reduction is performed by power transmission from the pinion gear 81 to the first sun gear 82, and the second stage of speed reduction is performed by power transmission from the second sun gear 83 to the planetary carrier 87.

[0063] 4 , a plurality of pump drive gears 91, 92 are housed in housing 73. The plurality of pump drive gears 91 includes at least one first pump drive gear 92 that transmits power from gear box 23 to first pump 42, and at least one second pump drive gear 91 that transmits power from gear box 23 to second pump 32. The first pump drive gear 92 and the second pump drive gear 91 are disposed radially outward of first sun gear 82 in the radial direction R, and rotate together with first sun gear 82.

[0064] As indicated by the two-dot chain line in Figure 4, a first pump drive gear 92 is engaged with the first sun gear 82. The center of the first pump drive gear 92 is located on the pump axis of the first pump 42. The pump shaft of the first pump 42 passes through the housing 73 and is connected to the first pump drive gear 92. In this way, power is transmitted to the first pump 42 from the electric motor 22 via the gearbox 23.

[0065] A second pump drive gear 91a is engaged with the first sun gear 82, and another second pump drive gear 91b is engaged with the second pump drive gear 91a. The center of the second pump drive gear 91b is located on the pump axis of the second pump 32. The pump shaft of the second pump 32 passes through the housing 73 and is connected to the second pump drive gear 91b. In this way, power is transmitted to the second pump 32 from the electric motor 22 via the gearbox 23.

[0066] The number of first pump drive gears 92 does not have to be one, and the number of second pump drive gears 91 does not have to be two. Furthermore, the ratio of the diameters of the first pump drive gear 92 and the second pump drive gear 91 is not particularly limited. For example, the number and diameters of the first pump drive gears 92 and the second pump drive gears 91 can be determined so that the rotation speed of the first pump 42 is higher than the rotation speed of the second pump 32. While FIG. 4 shows the pump shafts of the first pump 42 and the second pump 32 as being equidistant from the rotation axis X1, the positions of the first pump 42 and the second pump 32 can also be changed as appropriate.

[0067] (Operation and Effect) As described above, in the propulsion system 10A according to this embodiment, the first pump 42, which is a low-pressure pump that supplies lubricating oil for cooling the gearbox 23, and the second pump 32, which is a high-pressure pump that supplies hydraulic oil for driving the actuator 34, are both driven by power transmitted from the gearbox 23. Therefore, it is possible to change the pitch angle of the blades 11b and supply lubricating oil to the gearbox 23 without requiring an electric motor or other components for driving the pumps. Therefore, it is possible to suppress an increase in the weight of the propulsion system 10A of the aircraft 1.

[0068] Furthermore, according to this embodiment, the first pump 42, the second pump 32, and the gearbox 23 are arranged so as to intersect with an imaginary plane perpendicular to the rotational axis X1 of the propeller 11. In this way, by arranging the first pump 42 and the second pump 32 around the gearbox 23, it is possible to achieve a compact overall propulsion system 10A. In particular, in this embodiment, the housing 73 of the gearbox 23 is substantially frustum-shaped, and the first pump 42 and the second pump 32 are arranged around the first cylindrical portion 73a, so that the space around the first cylindrical portion 73a can be effectively utilized.

[0069] Furthermore, according to this embodiment, the first pump 42 and the second pump 32 are disposed outside the gear box 23, so that the first pump 42 and the second pump 32 can be easily repaired or replaced.

[0070] According to this embodiment, the heat exchanger 43 cools the oil using, as a refrigerant, air that flows in from the air intake 5a located around the propeller 11 of the aircraft 1. In this way, the refrigerant gas can be easily taken in by taking in air from around the propeller 11. The air intake 5a may be located on the outer wall of the nacelle 5 or around the propeller 11.

[0071] Furthermore, according to this embodiment, first sun gear 82 is engaged with multiple pinion gears 81 and has a relatively large diameter. This makes it easy to arrange pump drive gear 91 so that it engages with first sun gear 82, and makes it easy to extract power for driving the pump from first sun gear 82.

[0072] Second Embodiment Figure 8 is a block diagram of an aircraft propulsion system 10B according to a second embodiment. The propulsion system 10B includes a cooling system 100 instead of the cooling systems 50 and 60 of the first embodiment. The cooling system 100 combines the functions of both the cooling systems 50 and 60 of the first embodiment. In this embodiment and in third, fourth, and fifth embodiments described below, elements that are the same as or similar to those of the first embodiment are designated by the same reference numerals in the drawings, and detailed description thereof will be omitted.

[0073] The cooling device 100 cools the battery 21 and the multiple electric motors 22. The cooling device 100 has a water tank 101, a water pump 102, a heat exchanger 103, and a circulation path 104. The water tank 101 stores water to be used as cooling water. The water pump 102 supplies the water stored in the water tank 101 to the battery 21 and the multiple electric motors 22. The water pump 102 may be, for example, an electric or mechanical type.

[0074] The heat exchanger 103 cools the water flowing through the circulation path 104. The heat exchanger 103 is, for example, an air-cooled type. An air intake 5 a is arranged in the nacelle 5 of the aircraft 1, and the heat exchanger 103 cools the water that flows into the heat exchanger 103 using the air that flows in from the air intake 5 a as a refrigerant.

[0075] The water tank 101, water pump 102, heat exchanger 103, battery 21, and multiple electric motors 22 are arranged in a circulation path 104. Cooling water circulates through the circulation path 104 between the battery 21 and multiple electric motors 22 and the heat exchanger 103. That is, when the water pump 102 is driven, water stored in the water tank 101 is supplied to the battery 21 and multiple electric motors 22. The cooling water is heated by passing through the battery 21 and multiple electric motors 22, and after passing through the battery 21 and multiple electric motors 22, is sent to the heat exchanger 103 where it is cooled and then returned to the water tank 101.

[0076] Although the circulation path 104 in FIG. 8 includes a series of flow paths that sequentially supply water to the multiple electric motors 22, the circulation path 104 is not limited thereto. For example, the circulation path 104 may include a plurality of parallel branch paths that branch off from a water path extending from the water pump 102 and connect to the multiple electric motors 22. Furthermore, while the circulation path 104 in FIG. 8 guides the cooling water discharged from the water pump 102 to the multiple electric motors 22 and guides the cooling water that has passed through the multiple electric motors 22 to the battery 21, the circulation path 104 may also guide the cooling water discharged from the water pump 102 to the battery 21 and guide the cooling water that has passed through the battery 21 to the multiple electric motors 22. Furthermore, although the circulation path 104 in FIG. 8 includes a series of flow paths that supply water to the battery 21 and the electric motors 22, the circulation path 104 is not limited thereto. For example, the circulation path 104 may include a plurality of parallel branch paths that branch off from a water path extending from the water pump 102 and connect to the battery 21 and the electric motors 22.

[0077] This embodiment also provides the same effects as those of Embodiment 1. Furthermore, this embodiment requires only one heat exchanger to cool the battery 21 and the multiple electric motors 22, making it possible to make the entire propulsion system compact.

[0078] 9 is a block diagram of an aircraft propulsion system 10C according to a third embodiment. In the propulsion system 10C, the cooling device 100 of the second embodiment cools the lubricating oil flowing through the circulation path 44. That is, in this embodiment, the heat exchanger 103 of the cooling device 100 also functions as a heat exchanger for the lubrication device 40.

[0079] The lubrication device 110 supplies lubricating oil to multiple gears in the gearbox 23. The lubrication device 110 has an oil tank 41, a first pump 42, a heat exchanger 103, and a circulation path 111. The oil tank 41, the first pump 42, the heat exchanger 103, and the gearbox 23 are arranged in the circulation path 111. The circulation path 111 is an example of a first circulation path. The water tank 101, the water pump 102, the multiple motors 22, and the battery 21 are arranged in a circulation path 104. The circulation path 104 is an example of a second circulation path, and the water pump 102 is an example of a third pump.

[0080] Oil circulates between the gearbox 23 and the heat exchanger 103 through the circulation path 111. That is, when the first pump 42 is driven, the lubricating oil stored in the oil tank 41 is supplied to the gearbox 23. The lubricating oil is heated as it passes through the gearbox 23, flows out of the gearbox 23, and is sent to the heat exchanger 103 where it is cooled, and then is returned to the oil tank 41.

[0081] In this way, heat exchanger 103 is arranged so that circulation paths 111 and 104 pass through it, and the air flowing in from air intake 5a cools the oil flowing in circulation path 111 and the water flowing in circulation path 104.

[0082] This embodiment also provides the same effects as those of Embodiment 1. Furthermore, in this embodiment, the cooling of the liquid heated by the electric motor 22 and the battery 21 and the cooling of the oil supplied to the gearbox 23 can be performed using the same heat exchanger 103, making it possible to make the entire propulsion system more compact.

[0083] 10 is a block diagram of an aircraft propulsion system 10D according to a fourth embodiment. In the propulsion system 10D, lubricating oil for a gearbox 23 is cooled by water cooled by a heat exchanger 103 of a cooling device 100.

[0084] The lubrication device 120 supplies lubricating oil to a plurality of gears included in the gear box 23. The lubrication device 120 has an oil tank 41, a first pump 42, a heat exchanger 121, and a circulation path 122. The oil tank 41, the first pump 42, the heat exchanger 121, and the gear box 23 are arranged in the circulation path 122.

[0085] The heat exchanger 121 is, for example, water-cooled. The heat exchanger 121 is arranged so that the circulation path 122 and the circulation path 104 pass through it. The heat exchanger 121 cools the oil flowing through the circulation path 122 with water flowing through the circulation path 104. The circulation path 111 and the heat exchanger 121 are examples of a first circulation path and a first heat exchanger, respectively. The water pump 102, the circulation path 104, and the heat exchanger 103 are examples of a third pump, a second circulation path, and a second heat exchanger, respectively.

[0086] This embodiment also provides the same effects as the first embodiment. Furthermore, in this embodiment, the liquid for cooling the electric motor 22 and the battery 21 is used to cool the oil supplied to the gearbox 23. Therefore, even if it is difficult to arrange the heat exchanger 121 in a position where it can be cooled by air, the liquid for cooling the electric motor 22 and the battery 21 can be used to cool the heat exchanger 121, thereby increasing the degree of freedom in the arrangement of the heat exchanger 121.

[0087] Fifth Embodiment Fig. 11 is a block diagram of a propulsion system 10E for an aircraft according to a fifth embodiment. The propulsion system 10E includes a gas turbine 131 in addition to an electric motor 22 as a drive source for driving the propeller 11. Fig. 11 does not include a cooling device for cooling the battery 21 and the plurality of electric motors 22, or a lubrication device for supplying lubricating oil to the plurality of gears in a gearbox 23.

[0088] The propulsion system 10E includes a plurality of electric motors 22 and a gas turbine 131. A clutch 132 is interposed between the gearbox 23 and the gas turbine 131. The gearbox 23 has an input shaft 171. Similar to the input shaft 71, a pinion gear that engages with the first sun gear 82 is fixed to the input shaft 171 of the gearbox 23. The input shaft 171 is connected to the clutch 132. The clutch 132 is, for example, a one-way clutch. The clutch 132 is configured to permit torque transmission from the output shaft 131 a of the gas turbine 131 to the input shaft 171 of the gearbox 23 and to prohibit torque transmission from the input shaft 171 of the gearbox 23 to the output shaft 131 a of the gas turbine 131. The clutch 24 and the clutch 132 are examples of a first clutch and a second clutch, respectively.

[0089] This embodiment also provides the same effects as those of the first embodiment. Furthermore, in this embodiment, power can be transmitted to the propeller 11 not only from the plurality of electric motors 22 but also from the gas turbine 131.

[0090] Other Embodiments Although the embodiments have been described above, the above configurations can be modified, deleted, or added within the scope of the present disclosure.

[0091] The configurations of the propulsion systems described in the first to fifth embodiments are examples and are not limited to the above. For example, the first, second, third, fourth, and fifth embodiments can be combined as appropriate. The position, structure, shape, number, and other aspects of the elements of the propulsion system are not limited to those of the above embodiments.

[0092] For example, although the first to fifth embodiments have described an aircraft having four propellers, the aircraft is not limited to this. For example, the aircraft may be a single-engine aircraft having one propeller located at the front end of the fuselage, a twin-engine aircraft having one propeller on each of the left and right main wings, or a three-engine aircraft having one propeller on the front end of the fuselage and one on each of the left and right main wings.

[0093] In the first to fifth embodiments, the propulsion system is disposed in the nacelle 5 attached to the lower part of the main wing 3, but the propulsion system may be disposed in another location on the aircraft, in which case the aircraft does not need to include a nacelle. For example, the propulsion system may be disposed on the fuselage of the aircraft or within the main wing.

[0094] For example, the number of electric motors included in the propulsion system does not have to be four, but may be two, three, five or more.

[0095] In the first to fifth embodiments, the multiple electric motors 22 are arranged at equal intervals in the circumferential direction around the rotation axis X1 of the propeller 11 behind the gearbox 23, but the arrangement of the multiple electric motors 22 is not limited to this. Note that the configuration of the gearbox may also change depending on the arrangement of the multiple electric motors 22.

[0096] For example, the propulsion system may include multiple electric motors arranged side by side in a direction parallel to the rotational axis of the propeller. This further reduces the frontal projection area of ​​the entire system. For example, the propulsion system may include two electric motors arranged side by side in the fore-and-aft direction to the right of the rotational axis of the propeller, and two electric motors arranged side by side in the fore-and-aft direction to the left of the rotational axis of the propeller. In this case, the front electric motor may be located forward of the input shaft of the gearbox, and the rear electric motor may be located rearward of the input shaft of the gearbox.

[0097] Furthermore, for example, the multiple electric motors included in the propulsion system may include electric motors arranged in a direction perpendicular to the rotational axis of the propeller. This allows the size of the propulsion system to be reduced in a direction perpendicular to the rotational axis of the propeller (a direction perpendicular to the direction in which the electric motors are arranged). For example, by arranging multiple electric motors in a horizontal direction perpendicular to the rotational axis of the propeller, the vertical dimension of the propulsion system can be reduced, making it easier to store the propulsion system inside the main wing of an aircraft.

[0098] In the first to fifth embodiments, the rotation axes X2 of all the electric motors 22 provided in the propulsion system are disposed inward in the radial direction R from the outer ends of the housing 73 in the radial direction R, in the radial direction R perpendicular to the rotation axis of the propeller. However, this is not limited to this. For example, the rotation axes X2 of some of the electric motors 22 provided in the propulsion system may be disposed inward in the radial direction R from the outer ends of the housing 73 in the radial direction R.

[0099] In the first to fifth embodiments, the first pump 42, the second pump 32, and the gearbox 23 are arranged so as to intersect with an imaginary plane perpendicular to the rotation axis X1 of the propeller 11, but the configuration of the propulsion system is not limited to this. The imaginary plane perpendicular to the rotation axis X1 of the propeller 11 that passes through the gearbox 23 does not have to intersect with one or both of the first pump 42 and the second pump 32.

[0100] In the first to fifth embodiments, the first pump 42 and the second pump 32 are arranged outside the gearbox 23, but one or both of the first pump 42 and the second pump 32 may be arranged inside the gearbox 23. Also, instead of including one or both of the oil tanks 31, 41, the propulsion system may have an oil reservoir that stores oil inside the gearbox.

[0101] Alternatively, the oil tanks 31 and 41 may be a single common tank. That is, an oil tank that stores oil used as both the lubricating oil in the gearbox 23 and the hydraulic oil in the actuator 34 may be disposed in both the circulation path 36 and the circulation path 44.

[0102] The actuator 34 does not have to be a hydraulic actuator. For example, the actuator 34 may be another type of actuator, such as an electric motor. In this case, the propulsion system does not need to include the second pump 32, the control valve 33, etc.

[0103] In the first to fifth embodiments, the first pump 42 and the second pump 32 receive power from the first sun gear 82 of the gearbox 23. However, the method of extracting the pump power from the gearbox is not limited to this. For example, the pump power may be extracted from a gear separately attached to the transmission shaft 84, or from a gear separately attached to the planetary carrier 87 or the output shaft 72. The configuration of the gearbox 23 is not limited to that described in the first to fifth embodiments. In the first to fifth embodiments, the gearbox is configured to perform two-stage reduction, but it may also be configured to perform one-stage reduction, or three or more stages of reduction. The first pump 42 and the second pump 32 may receive power from a mechanism other than the gearbox 23. One or both of the first pump 42 and the second pump 32 may be electrically driven.

[0104] Some or all of the water pumps described in the first to fifth embodiments may be driven by power transmitted from the gearbox 23, similar to the first pump 42 and the second pump 32. In the first to fifth embodiments, the cooling device uses water as a liquid refrigerant, but the refrigerant is not limited to this and may be another liquid such as ethylene glycol. A clutch need not be interposed between the gearbox and the electric motor.

[0105] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, or any combination thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware or processor.

[0106] Disclosed Aspects Each of the following aspects is a disclosure of a preferred embodiment.

[0107] [Aspect 1] An aircraft propulsion system comprising: a plurality of electric motors; a propeller having a plurality of blades whose pitch angle can be changed; a gearbox that reduces the rotation of the plurality of electric motors and transmits the reduced rotation to the propeller; an actuator that changes the pitch angle of the blades; a pump that is driven by power transmitted from the gearbox and supplies oil to the gearbox; a heat exchanger that cools the oil using at least one of a gas and a liquid as a refrigerant; and a circulation path through which oil circulates between the gearbox and the heat exchanger.

[0108] According to the above configuration, the pump that supplies oil as lubricant to the gearbox is driven by power transmitted from the gearbox. This makes it possible to supply lubricant to the gearbox without requiring an electric motor for driving the pump. This reduces the weight of the aircraft propulsion system.

[0109] [Aspect 2] The propulsion system for an aircraft according to Aspect 1, wherein the pump is a first pump, and the propulsion system further includes a second pump, separate from the first pump, that is driven by power transmitted from the gearbox and supplies oil to the actuator at a pressure different from the pressure of oil supplied to the gearbox by the first pump.

[0110] According to the above configuration, the first pump, which supplies oil to the gearbox as lubricating oil, and the second pump, which supplies oil to drive the actuator, are both driven by power transmitted from the gearbox. This makes it possible to supply lubricating oil to the gearbox and change the blade pitch angle without requiring an electric motor or other components for driving the pumps. This therefore makes it possible to suppress an increase in the weight of the aircraft propulsion system.

[0111] [Aspect 3] The aircraft propulsion system according to Aspect 2, wherein the first pump, the second pump, and the gearbox are arranged so as to intersect with an imaginary plane perpendicular to the rotational axis of the propeller.

[0112] According to the above configuration, by arranging the first pump and the second pump around the gearbox, the entire propulsion system can be made compact.

[0113] [Aspect 4] The aircraft propulsion system according to Aspect 2 or 3, wherein the gearbox includes a plurality of gears and a housing that accommodates the plurality of gears, and the first pump and the second pump are disposed outside the housing.

[0114] According to the above configuration, since the first pump and the second pump are located outside the housing of the gearbox, maintenance of the first pump and the second pump can be easily performed.

[0115] [Aspect 5] The aircraft propulsion system according to any one of Aspects 1 to 4, wherein the aircraft has an air intake, the heat exchanger is a heat exchanger that cools oil using air flowing in from the air intake as a refrigerant, and the air intake is located in the periphery of the propeller of the aircraft.

[0116] According to the above configuration, by taking in air from the periphery of the propeller, it is possible to easily take in gas that serves as a refrigerant.

[0117] [Aspect 6] The aircraft propulsion system according to any one of Aspects 1 to 5, wherein the heat exchanger is a first heat exchanger and the circulation path is a first circulation path; the propulsion system further comprises: a battery that supplies power to the plurality of electric motors; a third pump that supplies a liquid that cools the plurality of electric motors or the battery; a second heat exchanger configured to cool the liquid; and a second circulation path through which liquid circulates between the plurality of electric motors or the battery and the second heat exchanger; and the first heat exchanger is a heat exchanger that cools oil flowing through the first circulation path by liquid flowing through the second circulation path.

[0118] According to the above configuration, the liquid for cooling the electric motor or the battery is used to cool the oil supplied to the gearbox, so that the liquid for cooling the electric motor or the battery can be used effectively.

[0119] [Aspect 7] The aircraft propulsion system described in Aspect 5, wherein the circulation path is a first circulation path, and the propulsion system further includes: a battery that supplies power to the plurality of electric motors; a third pump that supplies liquid that cools the plurality of electric motors or the battery; and a second circulation path through which liquid circulates between the plurality of electric motors or the battery and the heat exchanger, and the heat exchanger cools the oil flowing through the first circulation path and the liquid flowing through the second circulation path with air flowing in from the air intake.

[0120] According to the above configuration, the cooling of the liquid heated by the electric motor or the battery and the cooling of the oil supplied to the gearbox can be performed using the same heat exchanger, making it possible to make the entire propulsion system more compact.

[0121] [Aspect 8] The aircraft propulsion system according to any one of Aspects 2 to 4, wherein the gearbox comprises: pinion gears fixed to a plurality of input shafts driven by the plurality of electric motors; a sun gear engaged with the plurality of pinion gears; a transmission shaft fixed to the sun gear and disposed in a power transmission path between the electric motor and the propeller; and a pump drive gear engaged with the sun gear and connected to the first pump or the second pump.

[0122] According to the above configuration, the sun gear is engaged with multiple pinion gears and has a relatively large diameter, which makes it easy to arrange the pump drive gear so that it engages with the sun gear, and makes it easy to extract power for driving the pump from the sun gear.

[0123] [Aspect 9] The propulsion system for an aircraft according to any one of Aspects 1 to 8, further comprising a plurality of clutches connected to the plurality of electric motors, respectively, and interposed between the gearbox and the plurality of electric motors.

[0124] According to the above configuration, if a malfunction occurs in any of the plurality of electric motors, the effect on the propulsion system can be suppressed.

[0125] [Aspect 10] The aircraft propulsion system according to aspect 9, wherein the clutch is a first clutch; and the propulsion system further comprises: a gas turbine engine; and a second clutch interposed between the gearbox and the gas turbine engine.

[0126] According to the above configuration, power can be transmitted to the propeller not only from a plurality of electric motors but also from the gas turbine.

[0127] 1: Aircraft 5: Nacelle 5a: Air intake 10A, 10B, 10C, 10D, 10E: Propulsion system 11: Propeller 11b: Blade 21: Battery 22: Electric motor 23: Gearbox 24: Clutch 31: Oil tank 32: Second pump 33: Control valve 34: Actuator 41: Oil tank 42: First pump 43, 53, 63, 103, 121: Heat exchanger 51, 61, 101: Water tank 52, 62, 102: Water pump 44, 54, 64, 104, 111, 122: Circulation path 73: Housing 81: Pinion gear 82: First sun gear 83: Second sun gear 84: Transmission shaft 85: Planetary gear 86: Ring gear 87: Planetary carrier 91, 92: Pump drive gear 131: Gas turbine 132: Clutch

Claims

1. An aircraft propulsion system comprising: a plurality of electric motors; a propeller having a plurality of blades whose pitch angle can be changed; a gearbox that reduces the rotation of the plurality of electric motors and transmits the rotation to the propeller; an actuator that changes the pitch angle of the blades; a pump that is driven by power transmitted from the gearbox and supplies oil to the gearbox; a heat exchanger that cools the oil using at least one of a gas or liquid as a refrigerant; and a circulation path through which oil circulates between the gearbox and the heat exchanger.

2. An aircraft propulsion system as described in claim 1, wherein the pump is a first pump, and the propulsion system further comprises a second pump, separate from the first pump, that is driven by power transmitted from the gearbox and supplies oil to the actuator at a pressure different from the pressure of the oil supplied to the gearbox by the first pump.

3. An aircraft propulsion system as set forth in claim 2, wherein said first pump, said second pump and said gearbox are arranged so as to intersect with an imaginary plane perpendicular to the rotational axis of said propeller.

4. The aircraft propulsion system according to claim 2 or 3, wherein the gearbox has a plurality of gears and a housing that houses the plurality of gears, and the first pump and the second pump are disposed outside the housing.

5. An aircraft propulsion system as described in claim 1 or 2, wherein the aircraft has an air intake, the heat exchanger is a heat exchanger that cools oil using air flowing in from the air intake as a refrigerant, and the air intake is located in the periphery of the propeller of the aircraft.

6. An aircraft propulsion system as described in claim 1 or 2, wherein the heat exchanger is a first heat exchanger and the circulation path is a first circulation path, the propulsion system further comprises: a battery that supplies power to the plurality of electric motors; a third pump that supplies a liquid for cooling the plurality of electric motors or the battery; a second heat exchanger configured to cool the liquid; and a second circulation path through which liquid circulates between the plurality of electric motors or the battery and the second heat exchanger, and the first heat exchanger is a heat exchanger that cools oil flowing through the first circulation path by liquid flowing through the second circulation path.

7. The propulsion system of an aircraft according to claim 5, wherein said circulation path is a first circulation path, and said propulsion system further comprises: a battery supplying power to said electric motors; a third pump supplying liquid for cooling said electric motors or said battery; and a second circulation path through which liquid circulates between said electric motors or said battery and said heat exchanger, and said heat exchanger cools the oil flowing in said first circulation path and the liquid flowing in said second circulation path by air flowing in from said air intake.

8. An aircraft propulsion system as described in claim 2 or 3, wherein the gearbox comprises: pinion gears fixed to a plurality of input shafts driven by the plurality of electric motors; a sun gear engaging with the plurality of pinion gears; a transmission shaft fixed to the sun gear and disposed in a power transmission path between the electric motor and the propeller; and a pump drive gear engaging with the sun gear and connected to the first pump or the second pump.

9. An aircraft propulsion system as claimed in claim 1 or 2, further comprising a plurality of clutches connected to said plurality of electric motors respectively and interposed between said gearbox and said plurality of electric motors.

10. The aircraft propulsion system according to claim 9, wherein the clutch is a first clutch, and the propulsion system further comprises: a gas turbine engine; and a second clutch interposed between the gearbox and the gas turbine engine.

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