Electric propulsion device

Abstract

To provide an electric propulsion device that enhances motor efficiency by air-cooling a motor and can ensure high reliability and safety for an aircraft.SOLUTION: An electric propulsion device 106 includes a propeller 131 and a motor 121 that rotates the propeller. The propeller includes: a rotating boss 132 which is fixed to a rotational shaft 123 of the motor; and a blade 133 that protrudes to the outer side in the radial direction from the rotating boss. The blade has a base end part in which the profile continuously changes such that the trailing edge approaches parallel to a rotational shaft of a motor from the outer side in the radial direction toward the rotating boss in the vicinity of the rotating boss.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an electric propulsion device. [Background technology]

[0002] In recent years, expectations are growing for the social implementation of electric vertical take-off and landing aircraft, also known as small drones or flying cars. Patent Document 1 describes the configuration of an electric vertical take-off and landing aircraft that uses a motor to rotate propellers and can take off and land vertically from an airport. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-30384 A Summary of the Invention [Problem to be solved by the invention]

[0004] An electric vertical take-off and landing aircraft is characterized by its high responsiveness to attitude changes and rapid stabilization of the flight attitude. However, the motor generates heat by rotating and driving the propeller. In particular, an electric vertical take-off and landing aircraft tends to increase the load on the propeller in order to obtain the thrust for lifting and flying as an aircraft, and the motor is prone to becoming hot. When the motor generates heat and becomes hot, the motor efficiency decreases, making it difficult to achieve the desired performance, which may affect the reliability and safety of the aircraft.

[0005] Therefore, the motor needs to be cooled appropriately. For example, if an oil-cooling or water-cooling mechanism is installed to cool the motor, the weight of the aircraft increases, which is undesirable for the aircraft. Therefore, to cool the motor of such an aircraft, a highly efficient air-cooling mechanism that effectively utilizes the airflow blown by the propeller is required.

[0006] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide an electric propulsion device that can air-cool the motor to increase motor efficiency and ensure high reliability and safety of the aircraft. [Means for solving the problem]

[0007] The electric propulsion device of the present invention that solves the above problems is: An electric propulsion device including a propeller and a motor that rotates the propeller, The propeller has a rotation boss fixed to a rotation shaft of the motor and a blade protruding radially outward from the rotation boss, The blade is characterized in that it has a base end portion in the vicinity of the rotation boss, the airfoil shape of which changes continuously from the radially outer side toward the rotation boss, so that the trailing edge approaches parallel to the rotation shaft of the motor. Effect of the Invention

[0008] According to the present invention, it is possible to provide an electric propulsion device that can air-cool the motor to increase motor efficiency and ensure high reliability and safety of the aircraft.

[0009] Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. In addition, the problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] 1 is a plan view showing a schematic configuration of an aircraft equipped with an electric propulsion device according to a first embodiment. [Diagram 2] 1 is a plan view showing a schematic configuration of an electric propulsion device according to a first embodiment. [Diagram 3] 1 is a front view showing a schematic configuration of an electric propulsion device according to a first embodiment. [Figure 4] 4(A) is a cross-sectional view taken along line AA in FIG. 2, and FIG. 4(B) is a cross-sectional view taken along line BB in FIG. [Diagram 5]FIG. 4 is a diagram showing the flow velocity distribution of an airflow generated by the electric propulsion device of the first embodiment. [Figure 6] FIG. 2 is a plan view showing a schematic configuration of an electric propulsion device according to a comparative example. [Figure 7] FIG. 2 is a front view showing a schematic configuration of an electric propulsion device of a comparative example. [Figure 8] 8(A) is a cross-sectional view taken along line CC in FIG. 6, and FIG. 8(B) is a cross-sectional view taken along line DD in FIG. [Figure 9] FIG. 13 is a diagram showing the flow velocity distribution of airflow generated by an electric propulsion device of a comparative example. [Figure 10] FIG. 11 is a front view showing a schematic configuration of an electric propulsion device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] [First embodiment] FIG. 1 is a plan view showing a schematic configuration of an aircraft equipped with an electric propulsion device according to a first embodiment. The aircraft 100 comprises a fuselage 101, wings 102, a vertical stabilizer 103, a horizontal stabilizer 104, a cabin 105, and a number of electric propulsion units 106.

[0013] The electric propulsion device 106 has an electric propulsion device 106A for flight and an electric propulsion device 106B for lift-off. The electric propulsion device 106A for flight is attached to the main wing 102, and the electric propulsion device 106B for lift-off is attached to an attachment arm 107 protruding from the fuselage 101.

[0014] The electric propulsion unit 106A for flight is mounted horizontally so as to face the front of the aircraft 100. The electric propulsion unit 106B for lift is mounted vertically so as to face above the aircraft 100.

[0015] The electric propulsion device 106 has a motor 121 and a propeller 131. The motor 121 rotates the propeller 131, and thrust is obtained as a reaction force when the propeller 131 rotates and accelerates and discharges air. The electric propulsion device 106A for flight and the electric propulsion device 160B for levitation are symmetrical in their mounting positions and rotation directions in order to cancel out the torque caused by the rotation of the propeller 131. The orientation of the propeller 131 is also opposite to that of the rotation direction. The number of electric propulsion devices 106 is an even number in consideration of balance, and in this embodiment, there are four electric propulsion devices 106A for flight and four electric propulsion devices 106B for levitation. The electric propulsion devices 106A for flight and the electric propulsion devices 106B for levitation have similar configurations, except for their mounting positions and orientations.

[0016] FIG. 2 is a plan view showing the schematic configuration of the electric propulsion device of the first embodiment, FIG. 3 is a front view showing the schematic configuration of the electric propulsion device of the first embodiment, FIG. 4(A) is a cross-sectional view taken along line AA in FIG. 2, and FIG. 4(B) is a cross-sectional view taken along line BB in FIG. 2.

[0017] The electric propulsion device 106 has a motor 121 and a propeller 131. The motor 121 has a cylindrical housing 122 and a rotating shaft 123 protruding from an end face (opposing face) 122a on one axial side of the housing 122. The housing 122 rotatably supports the rotating shaft 123, and the rotating shaft 123 is rotated by the supply of power from a motor driver (not shown) to the motor 121. Figures 2 to 4(B) show a configuration example in which the electric propulsion device 106 rotates in the counterclockwise direction F.

[0018] The propeller 131 has a rotation boss 132 fixed to the rotation shaft 123 of the motor 121, and a number of blades 133 that protrude radially outward from the rotation boss 132. In this embodiment, the blades 133 are made up of three blades of the same shape, which are arranged at equal angular intervals from each other. The electric propulsion device 106 of this embodiment is characterized by the shape of the base end of the blades 133.

[0019] Here, the configuration of a comparative example will be described. In the description of the comparative example, the same components as those in this embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0020] FIG. 6 is a plan view showing the schematic configuration of an electric propulsion device in a comparative example, FIG. 7 is a front view showing the schematic configuration of an electric propulsion device in a comparative example, FIG. 8(A) is a cross-sectional view taken along line CC in FIG. 6, and FIG. 8(B) is a cross-sectional view taken along line DD in FIG. 6.

[0021] The electric propulsion device 206 of the comparative example has a rotation boss 232 fixed to the rotation shaft 123 of the motor 121, and a plurality of blades 233 that protrude radially outward from the rotation boss 232.

[0022] The blade 233 has a shape in which a chord, which is the length of a straight line connecting a leading edge 251 and a trailing edge 252 of the blade cross section, gradually widens from the root of the blade 233 to the tip, becomes maximum at approximately the same position as the outer circumferential surface 122b of the housing 122 of the motor 121, and then narrows again toward the tip. The blade 233 has a base end 241 that protrudes from the rotation boss 232, and a tip end 243 that protrudes continuously from the base end 241.

[0023] The base end 241 and the tip end 243 of the blade 233 form an obtuse angle wider than 90 degrees (deg) with respect to an imaginary plane Sv perpendicular to the rotation shaft 123 of the motor 121. The discharge angle θb of the blade 233 is defined as the angle formed between a tangent 254 at a trailing edge 252 of a center line 253 of the blade cross section and the imaginary plane Sv.

[0024] The discharge angle θb at the base end 241 of the blade 233 is an angle θb1 as shown in Fig. 8(A). The discharge angle θb at the boundary 242 between the base end 241 and the tip end 243, which is the maximum chord of the blade 233, is an angle θb2 as shown in Fig. 8(B).

[0025] The discharge angle θb1 of the base end 241 of the blade 233 and the discharge angle θb2 of the boundary portion 242 are approximately the same angle. In this embodiment, the discharge angle θb at the tip end 243 is also the same angle as the discharge angle θb2 of the boundary portion 242. In other words, the blade 233 has a substantially constant discharge angle θb from the base end 241 to the tip end 243. The blade 233 rotates counterclockwise CCW to discharge an airflow in the direction of the arrow Z and obtains propulsive force.

[0026] Returning to the description of the electric propulsion device 106 of this embodiment, The electric propulsion device 106 of this embodiment differs from the configuration of the comparative example described above in the shapes of the base end portion 141 and the intermediate portion 142 of the blade 133 of the propeller 131.

[0027] The base end 141 of the blade 133 has a configuration in which the airfoil shape changes continuously from the radial outside to the rotation boss 132 so that the trailing edge 152 approaches parallelism with the rotation shaft 123 of the motor 121 .

[0028] The base end 141 of the blade 133 has a curved shape (curved surface) in which the surface facing the housing of the motor 121 is curved concavely, and the discharge angle θa of the blade 133 with respect to an imaginary plane Sv perpendicular to the rotation shaft 123 of the motor 121 is nearly a right angle, that is, approximately 90 degrees (deg.). The discharge angle θa of the blade 133 is defined as the angle formed between a tangent 154 at a trailing edge 152 of a center line 153 of the blade cross section and the imaginary plane Sv.

[0029] The length of the chord of the base end 141 of the blade 133 , which is a straight line connecting the leading edge 151 and the trailing edge 152 , is the same as the maximum chord length of the tip end 143 of the blade 133 .

[0030] The tip end 143 of the blade 133 has a discharge angle θa that is an obtuse angle wider than 90 degrees (deg.). The blade 133 has an intermediate portion 142 that connects the base end 141 and the tip end 143 of the blade 133. The intermediate portion 142 constitutes the boundary portion between the base end 141 and the tip end 143, and has a three-dimensional curved shape in which the blade discharge angle θa with respect to the imaginary plane Sv changes continuously from the base end 141 to the tip end 143.

[0031] When the propeller 131 is rotated, the base end 141 and the middle portion 142 of the blade 133 generate an air flow toward the end face (opposing face) 122a of the housing 122 of the motor 121 due to the discharge angle θa1, forming a motor cooling area that generates motor cooling air to cool the housing 122 of the motor 121.

[0032] When the propeller 131 is rotated, the tip 143 of the blade 133 generates a flow of air that passes along the axial direction of the rotating shaft 123 of the motor 121 at a position radially outside the housing 122 of the motor 121 due to its discharge angle θa2, thereby forming a thrust securing region that generates thrust.

[0033] Next, the effects of the electric propulsion device 106 of this embodiment will be described in comparison with a comparative example.

[0034] 8(A), when propeller 231 rotates, an air flow is formed by blade 233, and the air flow becomes flow 261 with a strong rotational component directly below blade 233 on the motor 121 side. A flow 262 with only the rotational direction is generated along end face 122a of motor 121 due to the shear force of air flow 261 with a strong rotational component.

[0035] Fig. 9 shows a flow velocity distribution Vh of the air flow in the direction of the rotation axis at the end face 122a of the motor 121 in the comparative example. In Fig. 9, light-colored areas indicate slow flow velocities, while dark-colored areas indicate fast flow velocities. The darkest area has the same value as the circumferential velocity Vt, and the discharge direction is negative. As shown in Fig. 9, in area 932 directly below where the tip 243 of the blade 233 rotates, the flow velocity is fast, and it can be seen that thrust is being generated.

[0036] On the other hand, it can be seen that the flow velocity is almost zero in the region 931 directly below where the base end 241 of the blade 233 rotates. Therefore, there is almost no air flow toward the end face 122a of the motor 121, and there is a risk that the motor 121 will become hot due to insufficient cooling. Thus, it can be seen that cooling the motor 121 requires air flow in the direction of the rotation axis toward the end face 122a of the motor 121.

[0037] In the configuration of this embodiment, as shown in Fig. 4(A), when the blade 133 rotates, an air flow is formed by the blade 133, but the air flow is gently redirected because the chord of the base end 141 is longer than that of the comparative example. And, since the base end 141 of the blade 133 has a discharge angle θa of approximately 90 degrees (deg), the air flow 161 not only flows in the rotation direction as in the comparative example, but also in an inclined direction toward the end face 122a of the motor 121. Therefore, an oblique air flow 162 hits the end face 122a of the motor 121.

[0038] Fig. 5 shows a flow velocity distribution Vh of the air flow in the rotational axis direction at end face 122a of motor 121 of this embodiment. In Fig. 5, similar to Fig. 9, light-colored areas indicate slow flow velocities, and dark-colored areas indicate fast flow velocities.

[0039] 5, it can be seen that, as in the comparative example, in region 532 directly below where tip end 143 of blade 133 rotates, the flow velocity is high and thrust is generated. On the other hand, unlike the comparative example, in region 531 directly below where base end 141 of blade 133 rotates, the flow velocity is high on the rear side in the rotation axis direction of motor 121, and air flow 533 is generated that flows in the rotation axis direction of motor 121 toward end face 122a of motor 121, forming a motor cooling region. Therefore, cooling air can be applied to end face (opposing face) 122a of motor 121, and motor 121 can be air-cooled.

[0040] In this embodiment, a plurality of opening holes 124 are provided in the housing 122 of the motor 121. The opening holes 124 are opened in an end surface 122a of the housing 122 of the motor 121, which the base end 141 of the blade 133 faces. These plurality of opening holes 124 extend in a direction perpendicular to the curved surface of the blade 133 within the housing 122 so as to be inclined with respect to the axial direction of the rotation shaft 123 of the motor 121 and along the direction of the air flow 162. Therefore, the air flow 162 generated by the base end 141 can be actively caused to flow into the housing 122 of the motor 121 as cooling air, and the motor can be more effectively air-cooled.

[0041] 4(A), the electric propulsion device 106 of this embodiment has a configuration in which the discharge angle θa at the base end 141 of the blade 133 is approximately 90 degrees (deg.) If such an airfoil shape is formed, there is a concern that it will be difficult to obtain thrust as the propeller 131, but in the case of this embodiment, the reduction in thrust is approximately 4%, a sufficiently small value.

[0042] In this embodiment, the base end 141 of the blade 133 is disposed at a position facing the end face 122a of the motor 121, and this position is where the motor 121 would originally be an obstacle to the airflow, and it is considered that the influence on the propulsive force is suppressed because the motor 121 is only in the vicinity of the rotating boss 132 where the peripheral speed is low. Therefore, the trade-off between the propulsive force and ensuring the cooling performance is resolved. Furthermore, since the motor 121 is cooled, a strong torque can be generated, and therefore the propulsive force is more easily generated.

[0043] In this embodiment, the chord length of the base end 141 is set to the maximum chord length of the blade 133, but it may be shorter than that. If the chord length of the base end 141 is shortened, the distance between the trailing edge 152 of the base end 141 and the end face 122a of the motor 121 can be increased, collision with the motor 121 can be avoided, and safety during rotation can be better guaranteed.

[0044] However, since the air flow direction at the base end 141 is weakened and its effectiveness as cooling air is reduced, the minimum chord length of the base end 141 is set to be equal to the chord length at the tip end 143.

[0045] The discharge angle θa1 of the base end 141 is preferably between 100 degrees (deg) and 90 degrees (deg), and is particularly preferably 90 degrees (deg). Conventionally, the discharge angle of the base end has sometimes been changed from the rotation boss toward the outer periphery to match the high peripheral speed of the tip portion on the outer periphery side, and is, for example, an obtuse angle of 130 degrees (deg) or more. The electric propulsion device 106 of this embodiment is characterized in that the airfoil shape of the blades 133 changes discontinuously in the radial direction, making it possible to effectively generate cooling air that cools the motor.

[0046] Moreover, in order to ensure both the propulsive force and the length of the base end portion 141, it is preferable that the length of the base end portion 141 is 1 / 2 to 1 / 20 of the length of the tip portion 143. On the other hand, it is preferable that the length of the intermediate portion 142 is gradually changed to about 1 / 5 of the length of the tip portion 143, or is zero.

[0047] If the length of the intermediate portion 142 is changed gradually as in the former case, the change in the inclination up to the base end portion 141 is gradual, and no separation of the blade occurs, which is good for both improving cooling performance and ensuring propulsive force. If the length of the intermediate portion 142 is zero as in the latter case, the length of the base end portion 141 can be increased accordingly, and a large amount of cooling air can be ensured. Alternatively, the length of the tip end portion 143 can be increased to ensure more propulsive force.

[0048] As described above, according to the electric propulsion device 106 of the present embodiment, the motor 121 is air-cooled to increase motor efficiency, thereby ensuring high reliability and safety of the aircraft.

[0049] [Second embodiment] Next, a second embodiment of the present invention will be described. A characteristic feature of this embodiment is that a cap for blowing air is provided at the tip of the propeller 231. Note that the same components as those in the first embodiment are given the same reference numerals and detailed description thereof will be omitted.

[0050] FIG. 10 is a front view showing a schematic configuration of the electric propulsion device according to the second embodiment. The electric propulsion unit 116 of this embodiment has a blower cap 301 at the tip of the rotation boss 232. The cap 301 has a conical body 302 whose diameter gradually decreases in the direction away from the rotation boss 232 along the rotation axis, and a guide 303 that protrudes in a spiral shape from the outer circumferential surface of the body 302. This cap 301 has a configuration similar to an auxiliary device placed in front of the main engine, which is called an inducer in fluid mechanical terms.

[0051] An inclination angle θc that the guide 303 forms with the imaginary plane Sv is smaller than a discharge angle θb of the blade 233. The body 302 is fixed to a rotation boss 232 of the propeller 231, and rotates integrally with the propeller 231. The guide 303 generates an air flow in the Z direction along the rotation axis toward the end face 122a of the motor 121. This air flow can effectively cool the motor 121.

[0052] Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention described in the claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0053] 100...aircraft, 106, 106A, 106B, 116...electric propulsion unit, 121...motor, 122...housing, 123...rotating shaft, 131...propeller, 132...rotating boss, 133...blade, 141...base end, 142...middle part, 143...tip part, 151...leading edge, 152...trailing edge, 154...tangent, 206...electric propulsion unit, 231...propeller, 232...rotating boss, 233...blade, 241...base end, 243...tip part, 251...leading edge, 252...trailing edge, 254...tangent, Sv...imaginary plane

Claims

1. An electric propulsion device including a propeller and a motor that rotates the propeller, The propeller has a rotation boss fixed to a rotation shaft of the motor and a blade protruding radially outward from the rotation boss, The blade has a base end portion in the vicinity of the rotation boss, the airfoil shape of which changes continuously from the radially outer side to the rotation boss so that the trailing edge approaches parallel to the rotation shaft of the motor. An electric propulsion device characterized by:

2. 2. The electric propulsion device according to claim 1, wherein a base end of the blade has a curved surface that is concavely curved such that a surface facing the housing of the motor faces the housing, and a discharge angle of the blade is a right angle with respect to an imaginary plane perpendicular to a rotation shaft of the motor.

3. 3. The electric propulsion device according to claim 2, wherein the length of a chord of a straight line connecting the leading edge and the trailing edge of the base end of the blade is the same as the maximum chord of the tip end of the blade.

4. the blade has an intermediate portion connecting the proximal end and the distal end, 4. The electric propulsion device according to claim 3, wherein the intermediate portion has a three-dimensional curved shape in which the blade discharge angle with respect to the imaginary plane changes continuously from the base end to the tip end.

5. The motor has a housing having a plurality of openings formed in a surface thereof facing the base end of the blade, The electric propulsion device according to claim 2 , wherein the plurality of openings extend in a direction perpendicular to the curved surface and inclined with respect to the axial direction of the rotation shaft.

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