Motor and rotor blade device

Abstract

To provide a motor and rotor blade device that can improve dustproof and waterproof performance. [Solution] The motor (1) comprises an annular rotor (20) and a stator (10) facing the rotor (20). The rotor (20) has a magnet (23) and a housing (21) covering the magnet (23). The stator (10) has a coil (15) and a holder (11) holding the coil (15). The housing (21) has first protrusions (212g, 212h) projecting toward the holder (11). The holder (11) has a second protrusion (113) projecting toward the housing (21). The second protrusion (113) faces the first protrusions (212g, 212h) in the radial direction with a gap between them.

Description

Technical Field

[0001] The present invention relates to a motor and a rotor blade apparatus having the motor.

Background Art

[0002] Conventionally, as disclosed in Patent Document 1, a motor having rotor hole portions partitioned by rotor rib portions constituting a part of a rotor is known. The rotor hole portions form air paths for a stator such as a stator core and coils accommodated in the rotor. When the motor is driven, the air circulates through the air paths to cool the stator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The air paths expose the stator to the outside. When the motor is used in a rotor blade apparatus incorporated into, for example, an unmanned aerial vehicle (UAV) or the like, there is a risk that not only air but also water and dust may enter the motor through the air paths. Accordingly, it is required to improve the dustproof and waterproof performance of the motor.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a motor and a rotor blade apparatus capable of improving dustproof and waterproof performance.

Means for Solving the Problems

[0006] To achieve the above object, a motor according to the present invention comprises: an annular rotor, and a stator facing the rotor. The rotor comprises a magnet and a housing that covers the magnet. The stator comprises a coil and a holder for holding the coil, The housing has a first projection that protrudes toward the holder, The holder has a second projection that protrudes toward the housing, The second projection has a second projection that faces the first projection in the radial direction, separated by a gap. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic perspective view showing the appearance of motor 1 according to one embodiment of the present invention. [Figure 2] This is a perspective cross-sectional view along line 2-2 in Figure 1. [Figure 3] This is a perspective view of the holder 11 alone, illustrating its configuration in general terms. [Figure 4] This is a perspective cross-sectional view along line 4-4 in Figure 1. [Figure 5] This is a schematic plan view showing the configuration of motor 1 according to one embodiment of the present invention. [Figure 6] This is a schematic perspective view of the motor 1 with the housing 21 removed, according to one embodiment of the present invention. [Figure 7] This is a partial cross-sectional view along line 7-7 in Figure 1. [Figure 8] This is a perspective view of the housing 21 alone, illustrating its configuration in general terms. [Figure 9] This is a schematic cross-sectional view showing the structure of a rotor blade device 2 according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1 is a schematic perspective view showing the external appearance of a motor 1 according to one embodiment of the present invention. Figure 2 is a perspective cross-sectional view along line 2-2 in Figure 1. The motor 1 is, for example, an outer rotor type brushless motor mounted on an unmanned aerial vehicle (UAV), and as shown in Figures 1 and 2, has, for example, a generally flat cylindrical contour. The motor 1 includes a stator 10 and an annular rotor 20 that is rotatably supported by the stator 10 around axis X and faces the stator 10.

[0009] In the following description of this embodiment, the direction in which the axis X extends is defined as the axis X direction. Furthermore, in the axis X direction, one direction is defined as the upper side, and the other direction is defined as the lower side. For example, in Figures 1 and 2, the side on which the stator 10 is located is defined as the lower side, and the side on which the rotor 20 is located is defined as the upper side. Furthermore, the direction perpendicular to the axis X is defined as the radial direction, and in this radial direction, the side facing the axis X is defined as the inner circumference side, or the inside in the radial direction, and the side moving away from the axis X is defined as the outer circumference side, or the outside in the radial direction. Also, the direction around the axis X is defined as the circumferential direction.

[0010] First, let's describe the stator 10. The stator 10 has a holder 11 that constitutes the base of the motor 1. Figure 3 is a schematic perspective view of the holder 11 alone, showing the configuration of the holder 11. Referring to Figures 2 and 3 together, the holder 11 has an inner wall portion 111 defined on the inner circumference side, a mounting portion 112 that is continuous with the lower side of the inner wall portion 111, an outer wall portion (second projection) 113 defined on the outer circumference side, a connecting portion 114 that connects the mounting portion 112 and the outer wall portion 113, and an annular portion 115 that extends outward from the outer wall portion 113. The inner wall portion 111, the mounting portion 112, the outer wall portion 113, the connecting portion 114, and the annular portion 115 are integrally formed from a non-magnetic material including, for example, a metal material such as aluminum or a resin material.

[0011] The inner wall portion 111 is formed in a cylindrical shape with axis X as its central axis. The upper and lower ends of the inner wall portion 111 are open. As shown in Figure 2, the outer rings of two bearings 30, 30, which are arranged in the direction of axis X, are held on the inner circumferential surface of the inner wall portion 111. The bearings 30 are fitted into the inner wall portion 111 and fixed to the inner circumferential surface of the inner wall portion 111 with adhesive. However, the bearings 30 may be fixed to the inner circumferential surface of the inner wall portion 111 by any method such as press-fitting, intermediate fitting, or clearance fitting. The inner wall portion 111 functions as a bearing holder (bearing holding portion) for the two bearings 30, 30. The bearings 30 are, for example, ball bearings. However, other bearings such as sleeve bearings may be used for the bearings 30.

[0012] A pusher 12, formed in the shape of a thin, plate-like disc, is fixed to the opening at the lower end of the inner wall portion 111. The pusher 12 has the function of applying preload to the bearing 30. For example, a male thread 12a is formed on the outer circumferential surface of the pusher 12. On the other hand, a female thread 111a is formed on the inner circumferential surface of the opening at the lower end of the inner wall portion 111. In this way, the pusher 12 is fixed to the opening at the lower end of the inner wall portion 111 by being screwed into the opening at the lower end of the inner wall portion 111. The pusher 12 is formed from a metal material such as aluminum or a resin material. Note that the bearing 30 is preloaded by fixed-position preload using the pusher 12, but is not limited to this. For example, an elastic member such as a spring or leaf spring may be placed between the bearing 30 and the pusher 12, and preload may be applied to the bearing 30 by constant-pressure preload.

[0013] As shown in Figure 3, the mounting portion 112 is a portion for attaching the motor 1 to the airframe of the UAV (external equipment, not shown). The mounting portion 112 is formed in a flat, annular shape that extends outward from the lower end of the inner wall portion 111. The mounting portion 112 has a plurality (e.g., eight) of openings (second openings) 112a arranged in the circumferential direction. Each opening 112a penetrates the mounting portion 112 in the axial X direction. The openings 112a allow wiring to extend to the airframe and allow air to flow from inside the motor 1 to the outside space. The mounting portion 112 also has a plurality of screw holes 112b for attaching the motor 1 to the airframe.

[0014] The outer wall portion 113 is formed in a cylindrical shape with the axis line X as the central axis. The inner peripheral surface of the outer wall portion 113 faces, for example, the outer peripheral surface of the inner wall portion 111. The upper end of the mounting portion 112 and the lower end of the outer wall portion 113 are connected by the connection portion 114. The connection portion 114 is inclined so as to face upward as it goes from the mounting portion 112 toward the outer wall portion 113. The connection portion 114 is formed with a plurality (for example, 8) of openings (second openings) 114a arranged in the circumferential direction. The openings 114a penetrate the connection portion 114 in the axis line X direction. The openings 114a allow air to flow from the inside of the motor 1 to the external space.

[0015] The annular portion 115 extends annularly from the lower end of the outer wall portion 113 to the outer peripheral side. The annular portion 115 has an inclined portion 115a that is connected to the lower end of the outer wall portion 113 and is inclined so as to face downward as it goes toward the outer peripheral side, a flat portion 115b that extends from the outer peripheral end of the inclined portion 115a along, for example, a virtual plane orthogonal to the axis line X, a protruding portion (third protruding portion; hereinafter referred to as "axial protruding portion") 115c that protrudes downward in the axis line X direction from the outer peripheral end of the flat portion 115b, and a protruding portion (fourth protruding portion; hereinafter referred to as "radial protruding portion") 115d that protrudes radially outward to the outer peripheral side from the lower end of the axial protruding portion 115c.

[0016] As shown in Figure 2, the stator 10 has a heat sink (heat dissipation portion) 13 disposed between the outer peripheral surface of the inner wall portion 111 and the inner peripheral surface of the outer wall portion 113. Figure 4 is a perspective cross-sectional view taken along line 4-4 in Figure 1. With combined reference to Figure 2 and Figure 4, the heat sink 13 has a cylindrical main body 131 fixed at its outer peripheral surface to the inner peripheral surface of the outer wall portion 113 of the holder 11, and a plurality (for example, 36) of fins 132 extending from the inner peripheral surface of the main body 131 toward the axis line X to the inner peripheral side. The main body 131 and the fins 132 are integrally formed from a metal material such as an aluminum alloy having high thermal conductivity. The main body 131 is fixed to the inner peripheral surface of the outer wall portion 113 using, for example, an adhesive with high thermal conductivity.

[0017] The plurality of fins 132 are arranged at equal intervals in the circumferential direction, for example. In the present embodiment, the inner peripheral side end of each fin 132 faces the outer peripheral surface of the inner wall portion 111 of the holder 11 with a gap interposed therebetween. As shown in FIG. 2, the heat sink 13 comes into contact with the inner peripheral surface of the outer wall portion 113, the upper surfaces of the mounting portion 112 and the connecting portion 114 via the outer peripheral surface and lower surface of the main body 131 and the lower surfaces of the fins 132, so that heat from the coil and magnet to be described later is transmitted through the holder 11. The main body 131 and the plurality of fins 132 are arranged at positions corresponding to the opening 112a and the opening 114a of the holder 11 in the axis X direction.

[0018] The stator 10 includes a stator core 14 fixed to the outer peripheral surface of the outer wall portion 113 of the holder 11, a plurality of coils 15 wound around the stator core 14, and a plurality of insulators 16 disposed between the stator core 14 and each of the coils 15. The stator core 14 is formed of a laminate such as a silicon steel sheet which is a magnetic material, and functions as a yoke of the stator 10.

[0019] As shown in FIG. 4, the stator core 14 has a cylindrical base end portion 141, a plurality of (for example, 36) teeth 142 extending from the base end portion 141 to the outer peripheral side, and a tip portion 143 defined at the outer peripheral end of each tooth 142. The inner peripheral surface of the base end portion 141 is held on the outer peripheral surface of the outer wall portion 113 of the holder 11 using an adhesive, for example. The teeth 142 are arranged at equal intervals in the circumferential direction. The size of each tip portion 143 defined in the circumferential direction is set to be larger than the size of each tooth 132 similarly defined in the circumferential direction.

[0020] The coil 15 is held by the stator core 14, that is, the holder 11 by being wound around each tooth 142. An insulator 16 made of an insulating material is disposed between the stator core 14 and the coil 15. In this way, electrical insulation is established between the stator core 14 and the coil 15. Instead of disposing the insulator 16, electrical insulation may be established by applying or forming an insulating resin film on the surface of the stator core 14.

[0021] Next, the rotor 20 will be described. Referring together to Figures 1 and 2, the rotor 20 has a generally disc-shaped housing 21 that is rotatably supported on the inner wall portion 111 of the holder 11 of the stator 10 via bearings 30, 30, a cylindrical yoke 22 attached to the outer peripheral end of the housing 21, and a cylindrical magnet (permanent magnet) 23 attached to the inner peripheral surface of the yoke 22. The inner peripheral surface of the magnet 23 faces the outer peripheral surface of the tip portion 143 of the stator core 14 of the stator 10 with an air gap between them. Although the magnet 23 has a cylindrical shape, it may be formed as a single cylindrical magnet, or multiple magnets may be connected to form a cylindrical shape.

[0022] The housing 21 has a cylindrical inner circumference portion 211 defined on the inner side, an annular outer circumference portion 212 defined on the outer side, a plurality of connecting members (e.g., 8) or spokes 213 that connect the inner circumference portion 211 and the outer circumference portion 212 to each other, and a plurality of openings (e.g., 8) (first openings) 214 defined between adjacent spokes 213, 213. The inner circumference portion 211, the outer circumference portion 212 and the spokes 213 are integrally formed from a metal material such as aluminum or a resin material.

[0023] The inner circumference portion 211 is formed in a cylindrical shape with axis X as its central axis. The inner circumference portion 211 has a through hole 211a that penetrates the inner circumference portion 211 from its upper end to its lower end. The inner rings of the bearings 30, 30 are held on the outer circumferential surface of the inner circumference portion 211. Although adhesive is used for holding, the bearings 30, 30 may be fixed to the inner circumference portion 211 by any method other than adhesive, such as press-fitting, intermediate fitting, or clearance fitting onto the outer circumferential surface of the inner circumference portion 211. Note that the through hole 211a does not have to be formed; in other words, the inner circumference portion 211 may have a solid cylindrical shape. Multiple screw holes 211b for attaching a propeller of a UAV or the like are formed on the upper surface of the inner circumference portion 211.

[0024] Each spoke 213 extends radially between the inner circumference 211 and the outer circumference 212. Figure 5 is a schematic plan view showing the configuration of a motor 1 according to one embodiment of the present invention. As is clear from Figure 5, the opening 214 is arranged in the axial X direction at positions corresponding to the openings 112a and 114a of the holder 11 of the stator 10. In this way, an airflow path is established between the opening 214 and the openings 112a and 114a in the axial X direction. The fins 132 of the heat sink 13 are arranged in this airflow path. Alternatively, the opening 214 may be arranged at a position corresponding to the opening 112a, and an airflow path may be established between the opening 214 and the opening 112a.

[0025] As shown in Figure 2, the outer peripheral portion 212 has a covering portion 212a that extends radially in an annular shape to cover the upper surface of the outer wall portion 113 of the holder 11 of the stator 10, and a projection portion 212b that protrudes downward in an annular shape in the axial X direction from the outer peripheral end of the covering portion 212a. The lower end of the projection portion 212b is in contact with and received by the upper end of the magnet 23. At least a portion of the outer peripheral surface of the projection portion 212b faces the inner peripheral surface of the yoke 22.

[0026] Figure 6 is a schematic perspective view of the motor 1 with the housing 21 removed, according to one embodiment of the present invention. Referring to Figures 1, 2, and 6 together, the yoke 22 is formed in a cylindrical shape with axis X as its central axis. A magnet 23, also formed in a cylindrical shape with axis X as its central axis, is attached to the inner circumferential surface of the yoke 22. For example, adhesive is used to fix the magnet 23. The yoke 22 is formed from a magnetic material such as iron.

[0027] The yoke 22 has a cylindrical body 221. The body 221 has a plurality (e.g., six) of notches 222 formed at regular intervals in the circumferential direction at its upper end. In this embodiment, each notch 222 is formed by, for example, a pair of sides 222a, 222a defined along a virtual plane containing axis X, and a bottom surface 222b defined along a virtual plane perpendicular to axis X. Thus the notch 222 is formed in a rectangular shape, for example. The bottom surface 222b extends along a plane that is substantially the same as the upper surface of the magnet 23, for example.

[0028] The yoke 22 has, for example, two locking portions 222c that project upward in the direction of axis X from the bottom surface 222b within each notch 222. On the other hand, corresponding to these locking portions 222c, a plurality (e.g., 12) recesses 212c are formed on the outer peripheral end of the upper surface of the covering portion 212a of the outer peripheral portion 212 of the housing 21. The bottom surface 212d of the recesses 212c spreads out along, for example, a virtual plane perpendicular to axis X. The upper ends of the locking portions 222c of the yoke 22 are bent toward axis X and lock into the recesses 212c of the housing 21. In this way, the yoke 22 is attached to the housing 21.

[0029] Referring together to Figures 1 and 2, each notch 222 of the yoke 22 receives a protrusion 212e that projects outward from the outer circumferential surface of the projection 212b of the outer circumferential portion 212 of the housing 21 of the rotor 20. The protrusion 212e extends for a predetermined length in the circumferential direction. The outer diameter of the outer circumferential end of the protrusion 212e, defined radially with respect to the axis X, may be set to be larger than the outer diameter of the outer circumferential surface of the main body 221 of the yoke 22, which is similarly defined. In addition, the bottom surface 212f of the protrusion 212e contacts and is received by the bottom surface 222b of the notch 222 of the yoke 22.

[0030] The magnet 23 is a permanent magnet integrally formed from, for example, a magnetic material. The magnet 23 has a south pole region magnetized to the south pole and a north pole region magnetized to the north pole. The south pole region and the north pole region are arranged alternately in the circumferential direction. As described above, the upper surface of the magnet 23 extends along a plane that is almost identical to the bottom surface 222b of the notch 222 of the yoke 22, so in the axial X direction, the upper surface of the magnet 23 is defined to be below the upper surface of the main body 221 of the yoke 22.

[0031] Figure 7 is a partial cross-sectional view along line 7-7 in Figure 1. Figure 8 is a perspective view of the housing 21 alone, schematically showing the configuration of the housing 21. Referring together to Figures 2, 7, and 8, the inner circumference 211 of the housing 21 has an annular projection (hereinafter referred to as the "inner circumference projection") 211c on the lower surface of the inner circumference 211 facing the internal space of the motor 1, projecting downward in the axial X direction toward the holder 11 along the inner circumference end of the opening 214. On the other hand, the outer circumference 212 has a pair of annular projections (hereinafter referred to as the "outer circumference projection") 212g and 212h on the lower surface of the outer circumference 212, projecting downward in the axial X direction toward the holder 11 along the outer circumference end of the opening 214.

[0032] The lower end of the inner circumferential projection 211c is positioned below the upper end of the inner wall portion 111 of the holder 11. The inner surface of the inner circumferential projection 211c faces at least the outer surface of the inner wall portion 111 of the holder 11 with a gap in between. As a result, as is clear from Figures 2 and 7, the inner circumferential projection 211c covers the gap formed between the upper surface of the inner wall portion 111 of the holder 11 and the lower surface of the inner circumferential portion 211 of the housing 21 from the outer side. The holder 11 also has a flange portion 111b that protrudes inward on the inside of the inner wall portion 111. The flange portion 111b is in contact with the outer ring of the bearing 30. The lower end of the inner circumferential projection 211c is positioned below the upper end of the flange portion 111b. This prevents water and dust from entering the bearing 30, thus improving dustproof and waterproof performance.

[0033] On the other hand, the lower ends of the outer peripheral protrusions 212g and 212h are positioned below the upper end of the outer wall portion 113 of the holder 11. Furthermore, the outer peripheral surface of the inner peripheral peripheral protrusion 211g faces the inner peripheral surface of the outer wall portion 113 with a gap between them, while the inner peripheral surface of the outer peripheral peripheral protrusion 211h faces the outer peripheral surface of the outer wall portion 113 with a gap between them. As a result, as is clear from Figures 2 and 7, the two outer peripheral protrusions 212g and 212h cover the gap formed between the upper surface of the outer wall portion 113 and the lower surface of the outer peripheral portion 212 of the housing 21 from the inner and outer peripheral sides, respectively.

[0034] As is clear from Figure 7, the outer circumferential surface of the axial projection 115c of the annular portion 115 of the holder 11 faces the inner circumferential surface of the lower end of the yoke 22 with a gap in the radial direction. Furthermore, the upper surface of the radial projection 115d extending outward from the lower end of the axial projection 115c faces the lower surface of the yoke 22 with a gap in the axial X direction. In this embodiment, the outer diameter of the yoke 22 may coincide with the outer diameter of the radial projection 115d. However, the outer diameter of the radial projection 115d may be larger than the outer diameter of the yoke 22.

[0035] The outer wall portion 113 and annular portion 115 of the holder 11 of the stator 10, as well as the yoke 22, and the outer peripheral portion 212 of the housing 21 of the rotor 20 form a space for housing the stator core 14, coil 15, and magnet 23. Furthermore, in the motor 1 according to this embodiment, the air gaps formed between the stator 10 and the rotor 20 (for example, the air gap between the upper end of the inner wall portion 111 and the lower surface of the inner peripheral portion 211, the air gap between the upper end of the outer wall portion 113 and the inner surface of the outer peripheral portion 212, and the air gap between the outer peripheral end of the annular portion 115 and the lower end of the yoke 22) face the inner peripheral projection 211c, outer peripheral projections 212g, 212h, axial projection 115c, and radial projection 115d.

[0036] Figure 9 is a schematic cross-sectional view showing the structure of a rotor-wing device 2 according to one embodiment of the present invention. As shown in Figure 9, the rotor-wing device 2 comprises the aforementioned motor 1 and a propeller 3 that is rotatably mounted on the motor 1 around an axis X. The propeller 3 is composed of, for example, a pair of blades 3a, 3a that extend in opposite directions to each other in a direction perpendicular to the axis X. The propeller 3 is attached to the motor 1 by, for example, a screw 4 being screwed into a screw hole 211b in the housing 21 of the rotor 20. On the other hand, the rotor-wing device 2 is attached to, for example, the airframe of a UAV (external equipment, not shown) by a screw (not shown) being screwed into a screw hole 112b in the holder 11 of the stator 10.

[0037] For example, when the UAV is levitating, if current flows through the coil 15 of the stator 10, the rotor 20 rotates around axis X relative to the stator 10 due to interaction with the magnetic field generated by the magnet 23. In this way, the propeller 3 attached to the rotor 20 rotates around axis X. At this time, the coil 15 generates heat. The heat from the coil 15 is transferred to the body 131 and each fin 132 of the heat sink 13 via the stator core 14 and holder 11. The heat is then released into the air from the body 131 and each fin 132.

[0038] On the other hand, the airflow F generated by the rotation of the propeller 3 flows from the propeller 3 along the axis X towards the motor 1. The airflow F flows into the motor 1 through the opening 214 formed in the housing 21 of the rotor 20. Subsequently, the airflow F flows between the multiple fins 132 of the heat sink 13 and receives heat released from the heat sink 13. The heated airflow F is discharged into the space outside the motor 1 through the openings 112a and 114a of the holder 11. In this way, the rotation of the propeller 3 forces an airflow F into the motor 1, so that the heat generated by the motor 1 can be efficiently suppressed.

[0039] With the motor 1 described above, as shown in Figure 7, the upper end of the outer wall portion 113 of the holder 11 faces the outer peripheral protrusions 212g and 212h in the radial direction via an air gap. That is, the air gap between the outer wall portion 113 of the holder 11, which communicates with the housing space of the stator core 14 and coil 15, and the outer peripheral portion 212 of the housing 21 faces the outer peripheral protrusions 212g and 212h in the radial direction, so the airflow path formed between the outer wall portion 113 and the outer peripheral portion 212 is bent. As a result, for example, water and dust that have flowed into the motor 1 from the opening 214 by the airflow F can be prevented from entering the housing space of the stator core 14 and coil 15, thus improving dustproof and waterproof performance. Note that since the outer wall portion 113 and the outer peripheral protrusions 212g and 212h face each other via an air gap, an air inlet is formed between the outer wall portion 113 and the outer peripheral protrusions 212g and 212h. This effectively suppresses the heat generated by motor 1.

[0040] Furthermore, the upper end of the inner wall portion 111 of the holder 11 faces the inner circumferential projection 211c in the radial direction, with a gap in between. That is, the gap between the inner wall portion 111 of the holder 11, which communicates with the housing space of the bearings 30, 30, and the inner circumferential portion 211 of the housing 21 faces the inner circumferential projection 211c in the radial direction, so the airflow path formed between the inner wall portion 111 and the inner circumferential portion 211 is bent. As a result, for example, water and dust that have flowed into the motor 1 from the opening 214 by the airflow F can be prevented from entering the housing space of the bearings 30, 30, thus improving dustproof and waterproof performance.

[0041] Furthermore, the lower end of the yoke 22 faces the axial projection 115c of the annular portion 115 of the holder 11 via a gap in the radial direction, and also faces the radial projection 115d of the annular portion 115 via a gap in the axial X direction. As a result, the airflow path formed between the yoke 22 and the annular portion 115 is bent. Consequently, water and dust from the external space of the motor 1 can be prevented from entering the housing space of the stator core 14 and coil 15, thus improving dustproof and waterproof performance.

[0042] Furthermore, according to the motor 1 of this embodiment, the space housing the stator core 14 and coil 15 is covered by the outer wall portion 113 and annular portion 115 of the holder 11 and the outer peripheral portion 212 and yoke 22 of the housing 21. On the other hand, the heat sink 13, which faces the stator core 14 radially via the outer wall portion 113, is positioned within an air circulation path that communicates from the opening 214 to the openings 112a and 114a. As a result, dustproof and waterproof performance can be enhanced while effectively suppressing heat generation of the motor 1.

[0043] As described above, preferred embodiments of the motor 1 have been cited, but the motor 1 is not limited to the embodiments described above. For example, the present invention is applicable to motors other than brushless motors and inner rotor type motors. Also, for example, in the housing 21, one of the pair of outer peripheral protrusions 212h and 212g arranged on the outer circumference may be omitted. That is, only the outer peripheral protrusion 212g or only the outer peripheral protrusion 212h may be formed.

[0044] On the other hand, the radial projection 115d may be omitted in the holder 11. That is, only the axial projection 115c may be formed. Also, the holder 11 may have an axial projection (not shown) that protrudes upward in the axial X direction from the outer peripheral end of the radial projection 115d, and faces, for example, the outer peripheral surface of the main body 221 of the yoke 22 with a gap between them.

[0045] The present invention is not limited to the motor 1 and rotor blade device 2 according to the above embodiment, but includes all embodiments included in the concept and claims of the present invention. Furthermore, each configuration may be selectively combined as appropriate to achieve at least some of the above-described problems and effects. For example, each configuration in the above embodiment may be modified as appropriate depending on the specific use of the present invention. [Explanation of symbols]

[0046] 1…Motor, 2…Rotating blade device, 3…Propeller, 3a…Blade, 4…Screw, 10…Stator, 11…Holder, 12…Pusher, 12a…Male thread, 13…Heat sink, 14…Stator core, 15…Coil, 16…Insulator, 20…Rotor, 21…Housing, 22…Yoke, 23…Magnet, 30…Bearing, 111…Inner wall section, 111a…Female thread, 111b…Flange section, 112…Mounting section, 112a…Opening (second opening), 112b…Screw hole, 113…Outer wall section (second projection), 114…Connecting section, 114a…Opening (second opening), 115…Annular section, 115a…Inclined section, 115b…Flat section, 115c…Axial projection (Third protrusion), 115d...Radial protrusion (Fourth protrusion), 131...Main body, 132...Fin, 141...Base end, 142...Teeth, 143...Tip, 211...Inner circumference, 211a...Through hole, 211b...Screw hole, 211c...Inner circumference protrusion, 212...Outer circumference, 212a...Covering part 212a, 212b...Protrusion 212b, 212c...Recess, 212d...Bottom surface, 212e...Convex part, 212f...Bottom surface, 212g...Outer circumference protrusion (First protrusion), 212h...Outer circumference protrusion (First protrusion), 213...Spoke, 214...Opening (First opening), 221...Main body, 222...Notch, 222a...Side, 222b...Bottom surface, 222c...Locking part, X...Axis

Claims

1. A ring-shaped rotor, The rotor is opposed to a stator, The rotor comprises a magnet and a housing that covers the magnet. The stator comprises a coil and a holder for holding the coil, The housing has a first projection that protrudes toward the holder, The holder has a second projection that protrudes toward the housing, The second projection is a motor that faces the first projection in the radial direction, with an air gap between them.

2. The rotor has a yoke that contacts the magnet, The holder has a third projection that protrudes in the axial direction, The motor according to claim 1, wherein the third projection faces the yoke in the radial direction with a gap between them.

3. The holder has a fourth projection that protrudes radially from the third projection, The motor according to claim 2, wherein the fourth projection faces the yoke in the axial direction with a gap between them.

4. The housing has a first opening that opens in the axial direction, The holder has a second opening that opens in the axial direction, The motor according to any one of claims 1 to 3, wherein the first opening and the second opening are in communication with each other.

5. The stator has a heat dissipation portion that contacts the holder, The motor according to claim 4, wherein the heat dissipation section is arranged between the first opening and the second opening.

6. A motor according to any one of claims 1 to 5, A rotor blade device comprising: a propeller mounted to the motor so as to be rotatable around an axis;

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