Driving system for drone

Abstract

To provide a driving system for a drone that can obtain large lift force, while lowering noise.SOLUTION: A driving system for a drone is constituted of a propeller 100 and a motor 1. In the propeller 100, a center part and at least four blades are integrally formed. The motor 1 is an outer rotor-type motor in which a rotor 10 is arranged outside a stator 21. A heat sink 30 is arranged on an inner peripheral surface of a stator core main body 22a. The heat sink 30 is constituted to include a columnar heat sink main body 30a and a protruding part 30b formed to protrude from an inner peripheral surface of the heat sink main body 30. An outer peripheral surface of the heat sink main body 30a is directly or indirectly contacted with the inner peripheral surface of the stator core main body 22a. Permanent magnets 16, which are more than coils 24 and are more than twice of the number of blades 102, are fixed at equal intervals in a circumferential direction, on the inner peripheral surface of the rotor 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drive system for a drone that is composed of a propeller and a motor. [Background technology]

[0002] Conventionally, the noise generated by drones (unmanned aerial vehicles, also called unmanned aircraft), which fly by obtaining lift through the rotation of propellers, has been a problem. In response to this, for example, technology has been proposed to reduce the noise by using a different sound (canceling sound) (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-71292 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned technologies generate cancellation sounds only when certain conditions are met (e.g., when a human is nearby). However, they require the drone to be equipped with a sensor for detecting the specified conditions and a sound generator for generating the cancellation sounds. Therefore, even if these technologies are limited to the case where certain conditions are met, the drone itself becomes heavier, resulting in increased power consumption for flight. Furthermore, the flow of sound waves changes depending on the atmospheric temperature and humidity. Furthermore, since drones generate noise during flight, the flow of sound waves is complexly affected by flight direction and wind, making noise reduction through cancellation sounds highly uncertain. Therefore, in practice, technologies that reduce the noise level themselves rather than cancel it are being used. For example, low-noise propellers that generate less noise are commercially available, and they attempt to achieve quieter operation by increasing the propeller's angle of attack (the angle between the propeller's rotation plane and the blades) and reducing the propeller's rotation speed. However, while increasing the angle of attack and reducing the propeller's rotation speed reduces noise, it becomes difficult to obtain sufficient propulsive force (lift) for applications such as cargo transportation.

[0005] The present invention attempts to solve such problems, and aims to provide a drive system for a drone that can obtain large lift while reducing noise. [Means for solving the problem]

[0006] The first invention is a drone drive system consisting of a propeller and a motor, wherein the propeller has a center portion and at least four blades integrally formed therewith, the motor is an outer rotor type motor in which a rotor is disposed outside a stator, the center portion of the propeller is fixed to the upper surface of the rotor, the stator includes a stator core and a plurality of coils, and the stator core includes a cylindrical stator core body and a plurality of teeth formed to protrude at equal intervals in the circumferential direction from the outer circumferential surface of the stator core body. a rotor having a rotor teeth fixed to the teeth, a heat sink disposed on the inner peripheral surface of the stator core body, the heat sink including a cylindrical heat sink body and a protrusion formed to protrude from the inner peripheral surface of the heat sink body, the outer peripheral surface of the heat sink body being in direct or indirect contact with the inner peripheral surface of the stator core body, and a number of permanent magnets greater than the number of the coils and at least twice the number of the blades being fixed at equal intervals in the circumferential direction to the inner peripheral surface of the rotor.

[0007] In the drone drive system of the present invention, the propeller has four or more blades (e.g., six), which allows it to generate greater lift even at low rotation speeds than propellers with fewer blades. This means that high lift can be generated despite relatively low noise. The rotation of such a multi-blade propeller is made possible by the motor of the drone drive system of the present invention being configured to generate high torque (the force with which the motor tries to rotate the rotating shaft). In the motor of the present invention, permanent magnets are fixed to the inner surface of the rotor in a number at least twice the number of blades (e.g., seven times the number of blades), which contributes to the generation of high torque. Furthermore, because the number of permanent magnets is relatively large, the least common multiple of the number of slots and the number of poles is relatively large. This reduces cogging torque, improving motor output efficiency and reducing noise and vibration. Furthermore, the motor is equipped with a heat sink that is in direct or indirect contact with the inner surface of the stator core body, thereby effectively dissipating heat generated by the coils. This suppresses an increase in the coil's electrical resistance, thereby maintaining torque and the rotational speed of the rotating shaft while suppressing an increase in power consumption. Furthermore, in the case of a multi-blade propeller with four or more blades, each blade is generally connected by a hub located in the center, and friction occurs between the hub and the blades during propeller rotation, which is one cause of noise. In this regard, in the present invention, the propeller does not have a hub, and the center and the blades are formed integrally, thereby avoiding the noise caused by having a hub. As described above, the drone drive system according to the configuration of the first invention can obtain high propulsive force while reducing noise.

[0008] A second invention is a drone drive system according to the first invention, wherein the inside of the propeller is formed into a honeycomb structure, and the honeycomb structure is covered with carbon fiber reinforced plastic (CFRP).

[0009] According to the configuration of the second invention, the propeller has relatively high strength and is lightweight, so it does not deform during rotation and the angle of attack is maintained, making it possible to maintain a predetermined lift.

[0010] A third invention is a drone drive system according to the first invention, wherein the blades of the propeller are coated with an antistatic agent.

[0011] According to the configuration of the third invention, the blades are prevented from being charged with static electricity, so that turbulence of the airflow can be reduced, and noise caused by turbulence of the airflow can be avoided.

[0012] A fourth invention is a drive system for a drone, in which, in the configuration of the first invention, the wire constituting the coil has a rectangular cross section.

[0013] According to the fourth aspect of the present invention, the wire has a rectangular cross section, which results in a high space factor when coiled. This allows for a relatively small space to generate magnetic field lines of the same strength, which allows for the placement of a heat sink with a relatively large surface area. This allows for more effective dissipation of heat generated by the coil, which effectively suppresses increases in the coil's electrical resistance, thereby maintaining torque and the rotational speed of the rotating shaft while suppressing increases in power consumption.

[0014] A fifth invention is a drive system for a drone, in which, in the configuration of the first invention, the protrusion of the heat sink is composed of a first protrusion having a relatively large protrusion length and a second protrusion having a relatively short protrusion length, and the first protrusion and the second protrusion are arranged alternately.

[0015] According to the fifth aspect of the invention, the distance between the vicinity of the tip of each protrusion is greater than when all the protrusions are the same length, creating a relatively large space, which allows for efficient heat dissipation.

[0016] A sixth invention is a drive system for a drone, in which, in the configuration of the first invention, the stator is fixed to a base member, the base member has an outer ring portion, the inner peripheral surface of the stator core body is fixed in contact with the outer peripheral surface of the outer ring portion, the outer peripheral surface of the heat sink body is fixed in contact with the inner peripheral surface of the outer ring portion, the thermal conductivity of the base member is greater than or equal to the thermal conductivity of the stator core body, and the thermal conductivity of the heat sink is greater than or equal to the thermal conductivity of the base member.

[0017] According to the sixth aspect of the present invention, heat is efficiently conducted from the stator core body to the base member, and then to the heat sink. This allows the stator core and heat sink to be securely fixed to the base member, and furthermore, heat is dissipated from the base member itself, so that heat generated by the coil can be dissipated even more effectively.

[0018] A seventh invention is a drive system for a drone, in which, in the configuration of the first invention, the rotor is composed of an upper rotor to which the propeller is connected and a lower rotor to which the permanent magnets are fixed, and a plurality of feet are formed protruding downward from the outer wall of the upper rotor, and the feet are configured to strengthen the connection between the upper rotor and the lower rotor and to strengthen the holding of the plurality of permanent magnets.

[0019] According to the seventh aspect of the present invention, the multiple legs strengthen the fixation of the upper rotor and the lower rotor and also strengthen the retention of the permanent magnets. Furthermore, even if the distance between adjacent permanent magnets is shortened, the legs reliably prevent adjacent permanent magnets from coming into contact with each other. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a drone drive system that can obtain large lift while reducing noise. [Brief explanation of the drawings]

[0021] [Figure 1]1 is a schematic perspective view of a motor according to an embodiment of the present invention, viewed from above; [Figure 2] 1 is a schematic perspective view of a propeller according to an embodiment of the present invention, viewed from above. FIG. [Figure 3] FIG. 2 is a schematic plan view of a propeller. [Figure 4] FIG. 2 is a schematic side view of a propeller. [Figure 5] FIG. 2 is a schematic diagram showing the configuration of a blade. [Figure 6] FIG. 2 is a schematic perspective view of the motor (excluding the lower cover) as viewed from above. [Figure 7] FIG. 2 is a schematic perspective view of the motor (excluding the lower cover) as viewed from below. [Figure 8] FIG. 2 is a schematic plan view of the motor (excluding the lower cover). [Figure 9] FIG. 2 is a schematic bottom view of the motor (excluding the lower cover). [Figure 10] 1 is a schematic side view of the motor (excluding the lower cover). [Figure 11] FIG. 2 is a schematic perspective view of the rotor as viewed from above. [Figure 12] FIG. 2 is a schematic perspective view of the rotor as viewed from below. [Figure 13] FIG. 2 is a schematic perspective view of the upper rotor as viewed from above. [Figure 14] FIG. 2 is a schematic perspective view of the upper rotor as viewed from below. [Figure 15] FIG. 2 is a schematic side view of the upper rotor. [Figure 16] FIG. 2 is a schematic plan view of an upper rotor. [Figure 17] FIG. 2 is a schematic bottom view of the upper rotor. [Figure 18] FIG. 2 is a schematic perspective view of the lower rotor as viewed from above. [Figure 19] FIG. 2 is a schematic perspective view of the lower rotor as viewed from below. [Figure 20] FIG. 2 is a schematic perspective view of the lower rotor body as viewed from above. [Figure 21] FIG. 2 is a schematic perspective view of the permanent magnets arranged in the lower rotor, viewed from above. [Figure 22]FIG. 2 is a schematic perspective view of the stator as viewed from above. [Figure 23] FIG. 2 is a schematic perspective view of the stator as viewed from below. [Figure 24] FIG. 2 is a schematic perspective view of a stator core viewed from above. [Figure 25] FIG. 2 is a schematic plan view of a stator core. [Figure 26] FIG. 2 is a schematic perspective view of the coil as viewed from above. [Figure 27] FIG. 2 is a schematic front view of the coil as seen from inside the motor. [Figure 28] FIG. 2 is a schematic perspective view of an insulating member as viewed from above. [Figure 29] FIG. 2 is a schematic perspective view of the heat sink as viewed from above. [Figure 30] FIG. 2 is a schematic plan view of a heat sink. [Figure 31] FIG. 2 is a schematic perspective view of the base member as viewed from above. [Figure 32] FIG. 2 is a schematic perspective view of the base member as viewed from below. [Figure 33] FIG. 2 is a schematic perspective view of the central structure as viewed from above. [Figure 34] FIG. 2 is a schematic perspective view of components constituting the central structure as viewed from above. [Figure 35] FIG. 2 is a schematic perspective view of components constituting the motor (excluding the lower cover) as viewed from above. [Figure 36] FIG. 2 is a schematic perspective view of components constituting the motor (excluding the lower cover) as viewed from below. [Figure 37] FIG. 2 is a schematic cross-sectional view of the motor (excluding the lower cover) viewed from above. [Figure 38] FIG. 2 is a schematic cross-sectional view of the motor (excluding the lower cover) as viewed from below. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a detailed description will be given of a mode for carrying out the present invention (hereinafter, referred to as an embodiment). In the following description, the same components are denoted by the same reference numerals, and their description will be omitted or simplified. Note that a description of components that can be appropriately implemented by a person skilled in the art will be omitted, and only the basic components of the present invention will be described.

[0023] <Appearance of the motor 1 and propeller 100> As shown in FIG. 1, the motor 1 is an outer rotor motor in which the rotor 10 is disposed outside the stator 21. The rotor 10 is formed by integrating an upper rotor 12 and a lower rotor 14. The stator 21 includes a stator core 22 and a plurality of coils 24. A heat sink 30 is disposed on the inner peripheral surface of the stator core 22. The stator core 22 and the heat sink 30 are fixed to a base member 32. The lower part of the motor 1 is covered with a lower cover 40. The tip of the heat sink 30 does not contact the base member 32.

[0024] The lower cover 40 has through holes (not shown) for passing lead wires (not shown) for supplying power from an external power source to the stator 21. A rotating magnetic field is generated by controlling the current flowing through each coil 24 of the stator 21, and the coils 24 and the permanent magnets 16 (see, for example, FIG. 7) repeatedly attract and repel each other, causing the rotor 10 to rotate.

[0025] As shown in Figures 2, 3, and 4, the propeller 100 has a center portion 110 and six blades 102A to 102F integrally formed therewith. The blades 102A to 102F are collectively referred to as blades 102. Unlike this embodiment, the number of blades 102 is not limited to six, but may be four or more. For example, the number of blades 102 may be four, five, seven, or eight. However, it is preferable that the number of blades 102 is an even number.

[0026] The interior of the propeller 100 is formed from a honeycomb structure material, which is coated with carbon fiber reinforced plastic (CFRP). In other words, the structure of the propeller 100 is a honeycomb sandwich structure. The honeycomb structure material is, for example, aramid (fiber reinforced) honeycomb. This makes the propeller 100 lightweight and strong despite having six blades 102A and the like. Note that the honeycomb structure material is not limited to aramid honeycomb, and may be, for example, aluminum honeycomb.

[0027] An antistatic agent is applied to the surface of the blade 102. Specifically, a paint containing the antistatic agent is applied to the surface of the blade 102. The antistatic agent is, for example, a conductive polymer type, and one example is PPY-12 manufactured by Marubishi Yuka Kogyo Co., Ltd. This prevents the blade 102 from becoming charged with static electricity, which in turn smooths the flow of gas on the surface of the blade 102 and prevents separation of the airflow, preventing a decrease in lift.

[0028] The center portion 110 of the propeller 100 is fixed to the upper surface portion 12a of the rotor 10. The center portion 100 is fixed to the upper surface portion 12a by screws that pass through four through holes 110a formed in the center portion 110 and four holes formed in the central upper surface portion 12a.

[0029] The drone drive system of this embodiment includes a propeller 100 and a motor 1. This system uses a multi-blade propeller (a propeller with four or more blades) that is compact yet provides high thrust, and achieves high efficiency by optimizing cooperation with the motor. This system can achieve high thrust (lift for lifting the drone), high efficiency (obtaining the required thrust with a small amount of power), and quiet operation (reducing noise generated by air vortices, separation, etc.).

[0030] <About the structure of Propeller 100> The structure of the blade 102 will be described below with reference to Figure 5. The length of the blade 102 is the length from the center position P0 of the propeller 100 to the end P12. In this embodiment, the length from the center position P0 to the end P12 is 192 millimeters (mm).

[0031] In FIG. 5, P1 is a position 30 millimeters (mm) from the center position P0, and positions P2 to P11 are defined at 15-mm intervals from P1. The region from the center position P0 to P1 is referred to as the center vicinity portion 102a. The center vicinity portion 102a is 20% or less of the length of the blade 102, and in this embodiment, the length of the center vicinity portion 102a is approximately 15.6% of the length of the blade 102. The region from position P1 to position P11 is referred to as the blade main body portion 102b. The blade main body portion 102b is the main portion that generates lift through the rotation of the propeller 100, and is 70% or more of the length of the blade 102. In this embodiment, the length of the blade main body portion 102b is approximately 78.14% of the length of the blade 102. In this embodiment, the region from position P11 to end portion P12 is referred to as the blade end portion 102c. Furthermore, an area between adjacent positions, such as an area between position P1 and position P2, is called an "inter-position area."

[0032] The widest portion of the blade body 102b is not at position P6, which is the center of the blade body 102b in the longitudinal direction, but is shifted toward position P1. In this embodiment, the blade 102 has a maximum width W1 at position P3. The portion of the blade 102 having the maximum angle of attack is shifted toward position P1 from position P3, where the maximum width W1 is located. In this embodiment, the maximum angle of attack of 18.90° is at position P2.

[0033] The angle of attack gradually decreases from position P2 to position P11. However, the change in the angle of attack in the region between position P2 and position P3, which has the maximum width W1, is smaller than the change in the angle of attack in any of the regions between position P3 and position P11. In this embodiment, by configuring the blade 102 in this manner, maximum lift is obtained.

[0034] Generally, increasing the number of propeller blades (3, 7, 13, etc.) increases lift. However, the torque required of the motor increases, and so does power consumption. Therefore, if the battery capacity used is small, sufficient flight time may not be ensured. Furthermore, an even number of blades is more likely to cause vibration due to balance issues, but this is advantageous in terms of balance adjustment and manufacturing costs. For this reason, the number of blades in this embodiment is six. A balancing machine is used for balance adjustment to suppress vibration and maximize the propeller's performance.

[0035] <Outline of the structure of the motor 1 (excluding the lower cover 40)> The structure of the motor 1 will be outlined below with reference to Figures 6 to 10. The dimensions (external and internal shapes) of the motor 1 in the direction along the longitudinal direction of the rotation shaft (the direction of the arrow z in Figure 6, hereinafter referred to as the "rotation shaft direction") and in the horizontal direction (the direction of the arrow y in Figure 6, a direction perpendicular to the rotation shaft direction) are specified as dimensions necessary and sufficient to accommodate the components described below.

[0036] 6, the motor 1 has a stator 21 and a rotor 10. The rotor 10 is made up of an upper rotor 12 and a lower rotor 14.

[0037] As described above, the stator 21 includes the stator core 22 and the plurality of coils 24 (see FIG. 6). As shown in FIG. 8 as coils 24A to 24R, the motor 1 of this embodiment has 18 coils such as the coil 24A. In this specification, the coils 24A and the like are collectively referred to as coils 24. That is, the number of coils 24 in this embodiment is three times the number of blades 102 of the propeller 100, which is six. Unlike this embodiment, the number of coils 24 is between two and five times the number of blades 102, and preferably between three and four times.

[0038] As shown in FIGS. 7 and 10, the coil 24 is composed of a coil main body 24a and coil terminals 24b and 24c.

[0039] As described above, the rotor 10 is made up of the upper rotor 12 and the lower rotor 14 and is disposed outside the stator 21.

[0040] As shown in FIGS. 8 and 9, the heat sink 30 is in contact with the outer ring portion 32c of the base member 32, and the outer ring portion 32c is in contact with the stator core 22.

[0041] <Configuration of rotor 10> The configuration of the rotor 10 will be described with reference to Figures 11 to 21. As described above, the rotor 10 is made up of the upper rotor 12 and the lower rotor 14 (see Figures 11 and 12).

[0042] 13 to 17, the upper rotor 12 is integrally formed with a central portion 12a, multiple connecting beams 12b, an outer periphery 12c, and a rotating shaft 12d. The connecting beams 12b connect the central portion 12a and the outer periphery 12c. Openings 12bs are formed between adjacent connecting beams 12b. The openings 12bs allow heat radiated from the heat sink 30 and the base member 32 to be efficiently released to the outside.

[0043] Four holes 12aa are formed in the central portion 12a of the upper rotor 12 for connection to the propeller 100. A plurality of through holes 12cs are formed in the peripheral wall portion 12ca of the outer circumferential portion 12c.

[0044] The outer periphery 12c is formed with a plurality of legs 12e that protrude downward from an annular bottom 12cb. The legs 12e protrude from the inner periphery of the bottom 12cb.

[0045] 18 to 21, the lower rotor 14 is composed of a lower rotor body 15 (see FIG. 20) and a plurality of permanent magnets 16 (see FIG. 21). The lower rotor body 15 will be described by distinguishing between an outer peripheral surface 15a, an inner peripheral surface 15b, and an annular upper portion 15c.

[0046] As shown in Figure 20, the lower rotor body 15 is formed into a cylindrical shape as a whole. As shown in Figures 18 and 19, a plurality of permanent magnets 16 are fixed to the inner circumferential surface 15b. The number of permanent magnets 16 is greater than the number of coils 24 and is at least twice the number of blades 102 of the propeller 100 (see Figures 2 and 3), and is fixed to the inner circumferential surface 15b at equal intervals in the circumferential direction. In this embodiment, there are 42 permanent magnets 16.

[0047] The upper rotor 12 and the lower rotor 14 are made of a material with a thermal conductivity higher than that of iron. Specifically, the upper rotor 12 and the lower rotor 14 are made of an aluminum alloy. The aluminum alloy used to make the upper rotor 12 and the lower rotor 14 is, for example, a 2000 series aluminum alloy, more specifically, A2017(T4). Unlike this embodiment, the upper rotor 12 and the lower rotor 14 may be made of a magnesium alloy. Examples of magnesium alloys include, but are not limited to, ASTM AZ31, AZ61, AZ91, and ZK60. The lower cover 40 shown in FIG. 1 is also made of the same material as the upper rotor 12 and the lower rotor 14.

[0048] The permanent magnets 16 are rare earth magnets. Rare earth magnets are sintered magnets made of magnetic materials such as neodymium, iron, and boron. Adjacent permanent magnets 16 are magnetized so that the magnetic poles appearing on one side in the direction of the rotation axis alternate in the circumferential direction. In other words, adjacent permanent magnets 16 are made up of alternating magnetic poles, such as an N-pole portion, an S-pole portion, and an N-pole portion, on one side in the direction of the rotation axis.

[0049] <Configuration of stator 21> The configuration of the stator 21 will be described with reference to Figures 22 to 28. The stator 21 is made up of a stator core 22 (see Figures 24 and 25), a plurality of coils 24 (see Figures 26 and 27), and an insulator 25 (see Figure 28).

[0050] As shown in Figures 24 and 25, the stator core 22 is composed of a cylindrical stator core body 22a and a plurality of teeth 22b formed to protrude at equal intervals in the circumferential direction from the outer peripheral surface 22aa of the stator core body 22a.

[0051] A coil 24 (see Figures 26 and 27) is disposed on each tooth 22b. More specifically, an insulating member 25 (see Figure 28) is disposed in contact with each tooth 22b, and the coil 24 is disposed in contact with the insulating member 25. As can be seen from Figures 26 and 27, the wire constituting the coil 24 has a rectangular cross section in a direction perpendicular to the longitudinal direction. The rectangular cross section of the wire results in a larger space factor for the coil 24 than a wire with a circular cross section. This allows for effective use of the space within the motor 1, and in particular makes it possible to arrange a heat sink 30 with a sufficient surface area.

[0052] The material of the stator core 22 is, for example, an electromagnetic steel plate. The wires constituting the coils 24 are made of aluminum. The aluminum is, for example, A1100. Unlike this embodiment, the wires may be made of copper.

[0053] <Configuration of the heat sink 30> The configuration of the heat sink 30 will be described with reference to Figures 29 and 30. The heat sink 30 includes a cylindrical heat sink body 30a and a plurality of protrusions 30b formed to protrude toward the center from an inner peripheral surface 30ab of the heat sink body 30a.

[0054] 29 and 30, the protrusion 30b is composed of a first protrusion 30b1 having a relatively long protrusion length and a second protrusion 30b2 having a relatively short protrusion length. The first protrusion 30b1 and the second protrusion 30b2 are alternately arranged at equal intervals in the circumferential direction.

[0055] The heat sink 30 is made of a non-magnetic metal with a thermal conductivity higher than that of iron. Furthermore, the heat sink 30 is made of a material with a thermal conductivity equal to or higher than that of the base member 32. In this embodiment, the heat sink 30 is made of, for example, an aluminum alloy. The aluminum alloy is, for example, a 2000 series aluminum alloy, and more specifically, A2618(T6). Unlike this embodiment, the heat sink 30 may be made of a magnesium alloy. The magnesium alloy is, for example, K1A.

[0056] Because the first protrusion 30b1 and the second protrusion 30b2 are formed to protrude toward the center, a space is formed between the first protrusion 30b1 and the second protrusion 30b2. As a result, the air containing heat escapes in the vertical direction (the direction of arrow T1 in FIG. 29) and toward the center (the direction of arrow T2 in FIG. 30). This allows heat to be dissipated.

[0057] Since the protruding lengths of the first protruding portion 30b1 and the second protruding portion 30b2 are different, a space 30s (see FIGS. 29 and 30) is generated between the vicinity of the tips of the first protruding portion 30b1. This prevents the heat-laden air from accumulating between the protruding portions 30b, enabling more efficient heat dissipation.

[0058] <Configuration of base member 32> 31 and 32, the configuration of the base member 32 will be described. The stator 21, the heat sink 30, and the central structure 34 are fixed to the base member 32. The base member 32 is fixed to the lower cover 40.

[0059] The base member 32 is integrally formed with an outer ring portion 32a, an inner ring portion 32b, and multiple connecting beam portions 32c that connect the outer ring portion 32a and the inner ring portion 32b. Spaces 32s are formed between the multiple connecting beam portions 32c, allowing air to pass through. The spaces 32s allow air from the heat sink 30 to pass downward without being blocked.

[0060] The base member 32 is formed of a material having a thermal conductivity equal to or greater than that of the stator core 22. In this embodiment, the base member 32 is formed of, for example, an aluminum alloy. The aluminum alloy is preferably a material with a high thermal conductivity, such as a 2000 series aluminum alloy, and more specifically, such as A2014(T4). Unlike this embodiment, the base member 32 may be formed of a magnesium alloy. Such a magnesium alloy is, for example, ZK60A.

[0061] <Configuration of central structure 34> The configuration of the central structure 34 will be described with reference to Figures 33 and 34. The central structure 34 is made up of a bearing cover 34a, an upper bearing 34b1, a lower bearing 34b2, and a shaft fixing member 34c. The bearing cover 34a, the upper bearing 34b1, and the lower bearing 34b2 are each a flat cylindrical shape with a through hole in the center. In the motor 1, the components that make up the central structure 34 are not actually in contact with each other, but are arranged on the motor 1 at a predetermined distance apart.

[0062] <Connection of parts> The component connection structure will be described with reference to FIGS.

[0063] To construct the rotor 10, the upper rotor 12 and the lower rotor 14 are fixed together. The upper rotor 12 and the lower rotor 14 are fixed together (see FIGS. 11 and 12) in such a manner that the outer portion of the annular bottom portion 12cb of the outer periphery 12c of the upper rotor 12 (see FIG. 14) contacts the upper surface portion 15c of the lower rotor body 15 (see FIGS. 18 and 20), and the feet 12e (see FIGS. 13 to 15) fit between adjacent magnets 16. The feet 12e are configured to strengthen the connection between the upper rotor 12 and the lower rotor 14 and to strengthen the retention of the multiple permanent magnets 16 in predetermined positions.

[0064] An inner peripheral surface 22ab (see FIGS. 24 and 25) of the stator core body 22a is in contact with and fixed to an outer peripheral surface 32a2 (see FIGS. 31 and 32) of the outer ring portion 32a of the base member 32 (see FIGS. 37 and 38).

[0065] The outer peripheral surface 30aa (see FIGS. 29 and 30) of the heat sink 30 is in contact with and fixed to the inner peripheral surface 32a1 (see FIGS. 31 and 32) of the outer ring portion 32a of the base member 32 (see FIGS. 37 and 38). The protrusions 30b1 and 30b2 of the heat sink 30 do not contact the outer peripheral surface 32b2 of the inner ring portion 32b of the base member 32.

[0066] The bearing cover 34a, upper bearing 34b1, and lower bearing 34b2 of the central structure 34 are fixed to the inner peripheral surface 32b1 of the inner ring portion 32b of the base member 32 (see Figures 37 and 38). The upper bearing 34b1 and the lower bearing 34b2 are fixed with a predetermined gap between them (same as above).

[0067] The rotating shaft portion 12d of the rotor 10 is inserted into and fixed to the through holes in the center of the bearing cover 34a, the upper bearing 34b1, and the lower bearing 34b2. A bottom surface 12da (see FIGS. 12 and 14) of the rotating shaft portion 12d is fixed to the shaft fixing member 34c.

[0068] The base member 32 is fixed to the lower cover 40 (see FIG. 1). A space (not shown) is formed in the bottom of the lower cover 40 at a position and in a shape corresponding to the space 32s formed in the base member 32. This allows the heat radiated from the heat sink 30 and the base member 32 to be efficiently released to the outside.

[0069] In this embodiment, the outer peripheral surface 30aa of the heat sink main body 30a is indirectly in contact with the inner peripheral surface 22ab of the stator core main body 22a, but the outer peripheral surface 30aa of the heat sink main body 30a may also be configured to be in direct contact with the inner peripheral surface 22ab of the stator core main body 22a.

[0070] <Heat dissipation> Here, the relationship between the materials of the heat sink 30 and the base member 32 will be described. Both materials are non-magnetic and made of metals with higher thermal conductivity than iron. These materials are selected based on their thermal conductivity and weight (specific gravity), with particular attention paid to thermal conductivity. In this embodiment, the thermal conductivity of the material forming the heat sink 30 is higher than that of the material forming the base member 32. Heat generated in the coil 24 is first conducted to the stator core 22 and then conducted to the heat sink 30 via the base member 32. To ensure smooth heat conduction, it is preferable that the material of the subsequent component in the heat conduction stage has the same or higher thermal conductivity than the material of the previous component in the heat conduction stage. In this regard, in this embodiment, the stator core 22 is formed of an electromagnetic steel sheet, the base member 32 is made of a material with higher thermal conductivity than the electromagnetic steel sheet, and the heat sink 30 is made of a material with higher thermal conductivity than the base member 32. This allows the heat generated in the coil 24 to be smoothly dissipated to the outside of the motor 1.

[0071] The present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Explanation of symbols]

[0072] 1 motor 10 rotors 12 Upper rotor 14 Lower rotor 16 Permanent Magnets 21 Stator 22 stator core 24 coils 30 Heatsink 32 Base material 34 Central structure 40 Lower cover 100 propellers 102A~102F Blades

Claims

1. A drone drive system consisting of a propeller and a motor, The propeller has a center and at least four blades integrally formed therewith, the motor is an outer rotor type motor in which a rotor is disposed outside a stator, the center of the propeller is fixed to an upper surface of the rotor, the stator includes a stator core and a plurality of coils; The stator core is configured to include a cylindrical stator core body and a plurality of teeth formed to protrude at equal intervals in a circumferential direction from an outer peripheral surface of the stator core body, A coil is fixed to the teeth, A heat sink is disposed on the inner peripheral surface side of the stator core body, The heat sink includes a cylindrical heat sink body and a protrusion formed to protrude from an inner circumferential surface of the heat sink body, an outer peripheral surface of the heat sink body directly or indirectly contacting an inner peripheral surface of the stator core body; The number of permanent magnets is greater than the number of coils and is at least twice the number of blades, and the permanent magnets are fixed at equal intervals in the circumferential direction on the inner circumferential surface of the rotor. Drone drive system.

2. The inside of the propeller is formed into a honeycomb structure, and the honeycomb structure is covered with carbon fiber reinforced plastic (CFRP). The drive system for a drone according to claim 1 .

3. The blades of the propeller are coated with an antistatic agent. The drive system for a drone according to claim 1 .

4. The wire constituting the coil has a rectangular cross section. The drive system for a drone according to claim 1 .

5. The protrusion of the heat sink is composed of a first protrusion having a relatively large protrusion length and a second protrusion having a relatively short protrusion length, The first protrusions and the second protrusions are arranged alternately. The drive system for a drone according to claim 1 .

6. The stator is fixed to a base member, the base member has an outer ring portion; an inner peripheral surface of the stator core body contacting and fixed to an outer peripheral surface of the outer annular portion; an outer peripheral surface of the heat sink body is fixed to an inner peripheral surface of the outer annular portion in contact with the inner peripheral surface of the outer annular portion; the thermal conductivity of the base member is equal to or greater than the thermal conductivity of the stator core body, The thermal conductivity of the heat sink is equal to or greater than the thermal conductivity of the base member. The drive system for a drone according to claim 1 .

7. The rotor is composed of an upper rotor to which the propeller is connected and a lower rotor to which the permanent magnet is fixed, a plurality of legs are formed projecting downward from the outer peripheral wall of the upper rotor; The foot portion is configured to strengthen the connection between the upper rotor and the lower rotor and to strengthen the retention of the plurality of permanent magnets. The drive system for a drone according to claim 1 .

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