Motor

Abstract

A motor according to the present invention comprises: a rotor that can rotate about the central axis; a stator that faces the rotor with an interval therebetween; and a housing that accommodates each of the rotor and the stator. The housing has a housing body portion surrounding the stator and a plurality of heat dissipation portions protruding from the outer surface of the housing body portion to the outside of the housing body portion. The inner surface of the housing body portion is provided with a plurality of protrusions protruding to the inside of the housing body portion. At least a part of each of the plurality of protrusions faces the stator. When viewed from the direction in which the heat dissipation portion protrudes, the plurality of heat dissipation portions overlap the protrusions, respectively.

Description

Motor

[0001] This application claims priority to Japanese Patent Application No. 2024-104129, filed on June 27, 2024, the contents of which are incorporated herein by reference.

[0002] A rotating electric machine is known that includes a motor having a stator and a device casing that houses the motor, and that increases the amount of heat dissipated from the motor to the outside of the device casing by heat dissipation fins provided on the outer surface of the device casing (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-137178

[0004] In the rotating electrical machine described in Patent Document 1, the amount of heat dissipated from the stator to the outside of the device casing can be increased by increasing the heat dissipation area of ​​the heat dissipation fins. Specifically, the amount of heat dissipated from the stator to the outside of the device casing can be increased by increasing the number of heat dissipation fins and increasing the size of the heat dissipation fins. However, in this case, the weight of the device casing increases, making it difficult to reduce the weight of the rotating electrical machine.

[0005] In view of the above circumstances, one aspect of the present invention aims to provide a motor that can reduce the weight of the housing and prevent the temperature of the stator from becoming too high.

[0006] One aspect of the motor of the present invention includes a rotor rotatable about a central axis, a stator facing the rotor at a distance, and a housing accommodating the rotor and the stator. The housing has a housing main body surrounding the stator and a plurality of heat dissipation portions protruding from the outer surface of the housing main body to the outside of the housing main body. The inner surface of the housing main body is provided with a plurality of protrusions protruding inward of the housing main body. At least a portion of each of the plurality of protrusions faces the stator. When viewed from the direction in which the heat dissipation portions protrude, each of the plurality of heat dissipation portions overlaps with the protrusion.

[0007] According to one aspect of the present invention, in a motor, it is possible to reduce the weight of the housing while preventing the temperature of the stator from becoming too high.

[0008] FIG. 1 is a perspective view showing a motor of the first embodiment. FIG. 2 is a cross-sectional view showing the motor of the first embodiment. FIG. 3 is an enlarged cross-sectional view showing a portion of the motor of the first embodiment. FIG. 4 is an enlarged cross-sectional view showing another portion of the motor of the first embodiment. FIG. 5 is a cross-sectional view showing the motor of the first embodiment, taken along line VV of FIG. 2. FIG. 6 is a perspective view showing a motor of the second embodiment. FIG. 7 is a cross-sectional view showing the motor of the second embodiment. FIG. 8 is an enlarged cross-sectional view showing a portion of the motor of the second embodiment. FIG. 9 is an enlarged cross-sectional view showing another portion of the motor of the second embodiment. FIG. 10 is a cross-sectional view showing the motor of the second embodiment, taken along line XX of FIG. 7. FIG. 11 is a cross-sectional view showing the motor of the second embodiment, taken along line XI-XI of FIG. 7.

[0009] Hereinafter, motors according to embodiments of the present invention will be described with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiments, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of components may differ from the actual structure in order to make each component easier to understand.

[0010] In the following description, the Z axis is indicated in the figures as appropriate. The Z axis is the direction in which the central axis J of the embodiment described below extends. The central axis J shown in each figure is a virtual axis. In the following description, the direction in which the central axis J extends, i.e., the direction parallel to the Z axis, is referred to as the "axial direction." The radial direction centered on the central axis J is simply referred to as the "radial direction." The circumferential direction centered on the central axis J is simply referred to as the "circumferential direction." The circumferential direction is indicated by an arrow θ in each figure. The side of the axial direction toward which the Z axis arrow points (+Z side) is referred to as the "upper side." The side of the axial direction opposite to the side toward which the Z axis arrow points (-Z side) is referred to as the "lower side." Note that the terms "upper side" and "lower side" are simply names used to describe the relative positional relationships of the various components, and the actual positional relationships may be other than those indicated by these names.

[0011] First Embodiment As shown in FIG. 1 , a motor 10 of this embodiment is a disk-shaped motor centered on a central axis J. The motor 10 of this embodiment is mounted on, for example, an unmanned aerial vehicle and used as a drive device for rotating the rotors of the unmanned aerial vehicle about the central axis J. The motor 10 is a thin motor whose axial dimension is smaller than its radial dimension. As shown in FIG. 2 , the motor 10 is an axial gap motor in which a stator 50 faces a rotor 40 at an axial distance. The motor 10 includes a housing 11, a rotor 40, a shaft 44, a stator 50, a resin part 60, and a busbar unit 70. The motor 10 includes a stator 50 on each axial side of the rotor 40.

[0012] The housing 11 has a substantially cylindrical shape centered on the central axis J. The housing 11 accommodates the rotor 40, the stator 50, the resin part 60, and the busbar unit 70 therein. The housing 11 is made of metal. In this embodiment, the housing 11 is made of aluminum. The housing 11 may be made of a material other than aluminum. The housing 11 has a first housing 13, a second housing 16, a housing main body 12, and a heat dissipation part 27.

[0013] The first housing 13 is the lower portion of the housing 11. The first housing 13 is generally cylindrical and protrudes in the axial direction about a central axis J. The first housing 13 is open at the top. The first housing 13 has a first peripheral wall portion 14 and a bottom plate portion 15.

[0014] The first peripheral wall portion 14 has a generally cylindrical shape that protrudes in the axial direction about the central axis J. The first peripheral wall portion 14 surrounds one of the stators 50, which is disposed below the rotor 40, and a lower portion of the rotor 40 from the radially outer side. As shown in FIG. 1 , the first peripheral wall portion 14 is provided with a first fixing portion 14a.

[0015] The first fixing portion 14a has a generally rectangular cylindrical shape extending in the axial direction. The first fixing portion 14a is connected to the outer surface of the first circumferential wall portion 14. In this embodiment, a plurality of first fixing portions 14a are provided on the first circumferential wall portion 14. The first fixing portions 14a are arranged at intervals in the circumferential direction.

[0016] As shown in Fig. 2, the bottom plate portion 15 has a generally annular plate shape centered on the central axis J. The plate surface of the bottom plate portion 15 faces the axial direction. The radial outer edge of the bottom plate portion 15 is connected to the lower end of the first peripheral wall portion 14. The bottom plate portion 15 is disposed below the rotor 40 and the stator 50. The bottom plate portion 15 is provided with a bottom plate hole portion 15a and a first stator holding portion 15c.

[0017] The bottom plate hole 15a is a hole that penetrates the bottom plate 15 in the axial direction. When viewed in the axial direction, the bottom plate hole 15a has a substantially circular shape centered on the central axis J. A second bearing 76 is attached to the inner circumferential surface of the bottom plate hole 15a. The second bearing 76 has a substantially annular shape centered on the central axis J. In this embodiment, the second bearing 76 is a sliding bearing. The second bearing 76 may also be a ball bearing.

[0018] The first stator holding portion 15c protrudes upward from the bottom plate portion 15. The first stator holding portion 15c has a generally cylindrical shape centered on the central axis J. The first stator holding portion 15c is provided radially outward of the bottom plate hole portion 15a.

[0019] The second housing 16 is the upper portion of the housing 11. The second housing 16 is generally cylindrical and protrudes axially about the central axis J. The second housing 16 is open downward. The second housing 16 is fixed to the upper end of the first housing 13. The second housing 16 has a second peripheral wall portion 17 and a top plate portion 18.

[0020] The second circumferential wall portion 17 has a generally cylindrical shape that protrudes in the axial direction about the central axis J. The second circumferential wall portion 17 surrounds the other stator 50, which is disposed above the rotor 40, and an upper portion of the rotor 40 from the radially outer side. The lower end of the second circumferential wall portion 17 contacts the upper end of the first circumferential wall portion 14 in the axial direction. As shown in FIG. 1 , the second circumferential wall portion 17 is provided with a second fixing portion 17a.

[0021] The second fixing portion 17a has a generally rectangular cylindrical shape extending in the axial direction. The second fixing portion 17a is connected to the outer surface of the second peripheral wall portion 17. In this embodiment, the second peripheral wall portion 17 is provided with a plurality of second fixing portions 17a. The second fixing portions 17a are spaced apart in the circumferential direction. When viewed in the axial direction, the second fixing portions 17a overlap with different first fixing portions 14a. An internal thread (not shown) is provided on the inner peripheral surface of each second fixing portion 17a. When a bolt 81 is passed axially through the interior of each first fixing portion 14a and tightened into the internal thread of each second fixing portion 17a, the second housing 16 is fixed to the first housing 13. The second housing 16 may be adhesively fixed to the first housing 13 using an adhesive.

[0022] As shown in FIG. 2 , the top plate portion 18 has a generally annular plate shape centered on the central axis J. The plate surface of the top plate portion 18 faces the axial direction. The top plate portion 18 extends in a direction perpendicular to the axial direction. The top plate portion 18 is disposed above the stator 50 and the rotor 40. The top plate portion 18 faces the other stator 50, which is disposed above the rotor 40, in the axial direction. The top plate portion 18 is provided with a top plate recess 18a, a top plate hole 18c, and a second stator holding portion 18e.

[0023] The top plate recess 18a is a recess recessed downward from the surface facing upward of the top plate portion 18. When viewed in the axial direction, the top plate recess 18a has a substantially circular shape centered on the central axis J. A first bearing 75 is attached to the inner peripheral surface of the top plate recess 18a. The first bearing 75 has a substantially annular shape centered on the central axis J. In this embodiment, the first bearing 75 is a sliding bearing. The first bearing 75 may also be a ball bearing.

[0024] The top plate hole 18c is a hole that axially penetrates the top plate 18. When viewed from the axial direction, the top plate hole 18c has a substantially circular shape centered on the central axis J. The top plate hole 18c is provided radially inward of the top plate recess 18a.

[0025] The second stator holding portion 18e protrudes downward from the top plate portion 18. The second stator holding portion 18e has a generally cylindrical shape centered on the central axis J. The second stator holding portion 18e is located radially outward of the top plate recess 18a. When viewed in the axial direction, the second stator holding portion 18e overlaps with the first stator holding portion 15c.

[0026] The housing main body 12 is a portion of the housing 11 that surrounds the stator 50. In this embodiment, the housing main body 12 is composed of a first peripheral wall 14, a second peripheral wall 17, a top plate 18, and a bottom plate 15. That is, the housing main body 12 has the first peripheral wall 14, the second peripheral wall 17, the top plate 18, and the bottom plate 15. The housing main body 12 also has a cylindrical portion 12a. In this embodiment, the cylindrical portion 12a is composed of the first peripheral wall 14 and the second peripheral wall 17. The cylindrical portion 12a has a substantially cylindrical shape extending in the axial direction about the central axis J. The cylindrical portion 12a surrounds the two stators 50 from the radial outside. The cylindrical portion 12a faces each stator 50 in the radial direction. As shown in FIGS. 3 and 4 , a protrusion 21 is provided on the inner surface of the housing main body 12.

[0027] The protrusions 21 protrude from the inner surface of the housing body 12 toward the inside of the housing body 12. In the present embodiment, the housing body 12 is provided with a plurality of protrusions 21. As shown in Fig. 3, the plurality of protrusions 21 include a plurality of first protrusions 21a. As shown in Fig. 4, the plurality of protrusions 21 include a plurality of second protrusions 21e.

[0028] As shown in FIG. 3 , each of the multiple first protrusions 21a is a rib-like member protruding radially inward from the radially inward surface of the cylindrical portion 12a. When viewed axially, each first protrusion 21a is generally trapezoidal, with its short side positioned radially inward and its long side positioned radially outward. Therefore, the circumferential dimension of each first protrusion 21a increases radially outward. Therefore, the circumferential dimension Ltc of the portion of each first protrusion 21a connected to the housing main body 12 is greater than the circumferential dimension Lti of the tip of each first protrusion 21a, i.e., the circumferential dimension of the radially inner end of each first protrusion 21a. Each first protrusion 21a is spaced apart from one another along the circumferential direction. Although not shown, each first protrusion 21a extends axially. In the axial direction, the upper end of each first protrusion 21a is located at the upper end of the cylindrical portion 12a, and the lower end of each first protrusion 21a is located at the lower end of the cylindrical portion 12a. Therefore, each first protrusion 21a faces radially one of the stators 50, which is disposed below the rotor 40. Although not shown in the drawings, each first protrusion 21a faces radially the other of the stators 50, which is disposed above the rotor 40. As a result, at least a portion of the multiple protrusions 21 faces the stator 50. In addition, the multiple protrusions 21 also face radially the rotor 40, which is disposed between the pair of stators 50. This increases the amount of heat transferred from the rotor 40 to the housing 11 via the multiple protrusions 21, thereby preventing the temperature of the rotor 40 from becoming too high.

[0029] In this embodiment, the dimension of the cylindrical portion 12a, i.e., the dimension Lh of the housing main body 12, in the direction in which the first protrusion 21a protrudes, i.e., the radial direction, is larger than the dimension Ltr of the first protrusion 21a. The dimension Lh of the housing main body 12 in the direction in which the first protrusion 21a protrudes is the thickness of the cylindrical portion 12a in an area in which the first protrusion 21a is not provided.

[0030] The circumferential dimension Ltc of each first protrusion 21a is greater than the distance Lmc between adjacent first protrusions 21a in the circumferential direction. In this embodiment, the circumferential dimension Ltc of each first protrusion 21a is the maximum circumferential dimension of the first protrusion 21a. As described above, the circumferential dimension of each first protrusion 21a increases radially outward. Therefore, in this embodiment, the circumferential dimension Ltc of each first protrusion 21a is the circumferential dimension Ltc of the portion of each first protrusion 21a that connects to the housing main body 12.

[0031] In this embodiment, each first protrusion 21a is composed of a first portion 21b and a second portion (not shown). Each first portion 21b protrudes radially inward from the inner circumferential surface of the first peripheral wall portion 14 of the first housing 13. Each first portion 21b is a lower portion of the first protrusion 21a. Each first portion 21b is arranged at intervals from one another along the circumferential direction. Although not shown, each second portion protrudes radially inward from the inner circumferential surface of the second peripheral wall portion 17 of the second housing 16. Each second portion is an upper portion of the first protrusion 21a. Each second portion is arranged at intervals from one another along the circumferential direction. When viewed in the axial direction, each second portion overlaps with a different first portion 21b. In this embodiment, the lower end of each second portion contacts the upper end of the first portion 21b. Each second portion does not have to contact the first portion 21b.

[0032] As shown in FIG. 4 , each of the second protrusions 21e is a rib-like member that protrudes downward, i.e., in the axial direction, from the downward-facing surface of the top plate 18, i.e., the surface facing the axial direction. When viewed radially, each second protrusion 21e is generally trapezoidal, with its short side positioned downward and its long side positioned upward. Therefore, the circumferential dimension of each second protrusion 21e increases upward. Therefore, the circumferential dimension Ltc of the portion of each second protrusion 21e that connects to the housing main body 12 is greater than the circumferential dimension Lti of the tip of each second protrusion 21e, i.e., the circumferential dimension of the lower end of each second protrusion 21e. As described above, the circumferential dimension Ltc of the portion of each first protrusion 21a that connects to the housing main body 12 is greater than the circumferential dimension Lti of the tip of each first protrusion 21a. Therefore, the circumferential dimension Ltc of the portion of each protrusion 21 that connects to the housing main body 12 is greater than the circumferential dimension Lti of the tip of each protrusion 21. In this embodiment, the end of the protrusion 21 in the direction in which it protrudes from the housing main body 12 is referred to as the tip of the protrusion 21. The tip of the protrusion 21 includes the radially inner end of the first protrusion 21a and the lower end of the second protrusion 21e.

[0033] The second protrusions 21e are spaced apart from one another in the circumferential direction. Although not shown, the second protrusions 21e extend radially. In this embodiment, the radially outer ends of the second protrusions 21e are connected to the upper ends of different first protrusions 21a. The second protrusions 21e do not have to be connected to the first protrusions 21a. The second protrusions 21e face the other stator 50, which is disposed above the rotor 40, in the axial direction. As a result, at least some of the multiple protrusions 21 face the stator 50.

[0034] In this embodiment, the dimension Lh of the housing main body 12, i.e., the top plate 18, is greater than the dimension Ltr of the second protrusion 21e in the protruding direction, i.e., the axial direction. The dimension Lh of the housing main body 12 in the protruding direction of the second protrusion 21e is the thickness of the top plate 18 in an area where the second protrusion 21e is not provided. As described above, the dimension Lh of the housing main body 12 is greater than the dimension Ltr of the first protrusion 21a provided on the tubular portion 12a in the protruding direction of the first protrusion 21a. As a result, the dimension Lh of the housing main body 12 is greater than the dimension Ltr of the first protrusion 21a in the protruding direction of the protrusion 21 in both the tubular portion 12a and the top plate 18.

[0035] The circumferential dimension Ltc of each second protrusion 21e is greater than the distance Lmc between adjacent second protrusions 21e in the circumferential direction. In this embodiment, the circumferential dimension Ltc of each second protrusion 21e is the maximum circumferential dimension of the second protrusion 21e. As described above, the circumferential dimension of each second protrusion 21e increases upward. Therefore, in this embodiment, the circumferential dimension Ltc of each second protrusion 21e is the circumferential dimension Ltc of the portion of the second protrusion 21e that connects to the housing main body 12. As described above, the circumferential dimension Ltc of each first protrusion 21a is greater than the distance Lmc between adjacent first protrusions 21a in the circumferential direction. Therefore, the circumferential dimension Ltc of each protrusion 21 is greater than the distance Lmc between adjacent protrusions 21 in the circumferential direction.

[0036] As shown in FIG. 1 , the heat dissipation portion 27 protrudes from the outer surface of the housing main body 12 to the outside of the housing main body 12. The heat dissipation portion 27 is plate-shaped with its plate surface facing the circumferential direction. In this embodiment, the housing 11 has multiple heat dissipation portions 27. The heat dissipation portions 27 are spaced apart from one another in the circumferential direction. This increases the surface area of ​​the outer surface of the housing 11, thereby increasing the amount of heat dissipated from the housing 11 to the outside of the motor 10. In this embodiment, the multiple heat dissipation portions 27 include multiple first heat dissipation portions 27 a and multiple second heat dissipation portions 27 e. Note that the multiple heat dissipation portions 27 may be configured to include only one of the multiple first heat dissipation portions 27 a and the multiple second heat dissipation portions 27 e. In this case, the multiple heat dissipation portions 27 preferably include multiple first heat dissipation portions 27 a.

[0037] As shown in FIG. 5, each of the multiple first heat dissipation portions 27a is a plate-like member that protrudes radially outward from the radially outward surface of the cylindrical portion 12a. As shown in FIG. 1, each first heat dissipation portion 27a extends in the axial direction. As shown in FIG. 2, in the axial direction, the upper end of each first heat dissipation portion 27a is located at the upper end of the cylindrical portion 12a, and the lower end of each first heat dissipation portion 27a is located at the lower end of the cylindrical portion 12a. As shown in FIG. 1, each first heat dissipation portion 27a is spaced apart from one another in the circumferential direction. In this embodiment, each first heat dissipation portion 27a is composed of a first portion 27b and a second portion 27c.

[0038] As shown in FIG. 2 , each first portion 27b protrudes radially outward from the outer circumferential surface of the first circumferential wall portion 14 of the first housing 13. Each first portion 27b is a lower portion of the first heat dissipation portion 27a. As shown in FIG. 1 , each first portion 27b is spaced apart from one another in the circumferential direction. As shown in FIG. 2 , each second portion 27c protrudes radially outward from the outer circumferential surface of the second circumferential wall portion 17 of the second housing 16. Each second portion 27c is an upper portion of the first heat dissipation portion 27a. As shown in FIG. 1 , the second portions 27c are spaced apart from one another in the circumferential direction. When viewed in the axial direction, each second portion 27c overlaps with a different first portion 27b. In this embodiment, the lower end of each second portion 27c contacts the upper end of the first portion 27b. Each second portion 27c does not necessarily have to contact the first portion 27b.

[0039] 3, when viewed in the radial direction, i.e., the direction in which each first heat dissipation portion 27a protrudes, each first heat dissipation portion 27a overlaps with a different first protrusion 21a. This allows each first heat dissipation portion 27a to be disposed close to the first protrusion 21a. This reduces the thermal resistance between the first protrusion 21a and the first heat dissipation portion 27a.

[0040] As shown in FIG. 4 , each of the multiple second heat dissipation portions 27e is a plate-like member that protrudes upward, i.e., in the axial direction, from the surface of the top plate portion 18 that faces upward, i.e., the surface that faces the axial direction. As shown in FIG. 1 , each second heat dissipation portion 27e extends radially. The radial inner end of each second heat dissipation portion 27e is located radially outward from the first bearing 75. As shown in FIG. 2 , the radial outer end of each second heat dissipation portion 27e is located radially outward from the radial outer end of the top plate portion 18. As shown in FIG. 1 , each second heat dissipation portion 27e is arranged at intervals from one another along the circumferential direction. The radial outer ends of each second heat dissipation portion 27e are connected to the upper ends of different first heat dissipation portions 27a.

[0041] As shown in FIG. 4 , when viewed in the axial direction, i.e., the direction in which each second heat dissipation portion 27e protrudes, each second heat dissipation portion 27e overlaps with a different second protrusion 21e. This allows each second heat dissipation portion 27e to be positioned close to the second protrusion 21e. Therefore, the thermal resistance between the second protrusion 21e and the second heat dissipation portion 27e can be reduced. As described above, when viewed in the direction in which the first heat dissipation portion 27a protrudes, each first heat dissipation portion 27a overlaps with a different first protrusion 21a. Therefore, when viewed in the direction in which the heat dissipation portion 27 protrudes, each heat dissipation portion 27 overlaps with the protrusion 21a.

[0042] In this embodiment, the first peripheral wall 14, the first portion 21b of the first protrusion 21a, and the first portion 27b of the first heat dissipation portion 27a are each part of the first housing 13. That is, the first peripheral wall 14, the first portion 21b, and the first portion 27b are each part of a single member. In this embodiment, the second peripheral wall 17, the top plate 18, the second portion (not shown) of the first protrusion 21a, the second protrusion 21e, the second portion 27c of the first heat dissipation portion 27a, and the second heat dissipation portion 27e are each part of the second housing 16. That is, the second peripheral wall 17, the top plate 18, the second portion (not shown), the second protrusion 21e, the second portion 27c, and the second heat dissipation portion 27e are each part of a single member. As a result, the housing main body 12, the multiple protrusions 21, and the multiple heat dissipation portions 27 are each part of a single member.

[0043] As shown in Fig. 2, the rotor 40 has a substantially circular ring shape centered on a central axis J. The rotor 40 is rotatable about the central axis J. The rotor 40 faces the stator 50 with a gap therebetween in the axial direction. In the axial direction, the rotor 40 is disposed between one stator 50 and the other stator 50. The rotor 40 has a magnet holder 41 and a magnet 42.

[0044] The magnet holder 41 has a substantially annular shape centered on the central axis J. In this embodiment, the magnet holder 41 is made of, for example, aluminum. The magnet holder 41 may be made of other materials. The magnet holder 41 has a first holder 41a and a second holder 41b. The first holder 41a has a substantially annular shape centered on the central axis J. The first holder 41a is the radially inner portion of the magnet holder 41. The second holder 41b has a substantially annular shape centered on the central axis J. The second holder 41b protrudes radially outward from the first holder 41a. The axial dimension of the second holder 41b is smaller than the axial dimension of the first holder 41a. The magnet 42 has a substantially annular shape centered on the central axis J. The magnet 42 is fixed to the outer peripheral surface of the second holder 41b. The magnet 42 has a magnetic pole facing in the axial direction. The magnet 42 faces the stator 50 with a gap in the axial direction.

[0045] The shaft 44 has a generally cylindrical shape extending in the axial direction around the central axis J. The shaft 44 is disposed radially inward of the rotor 40 and the stator 50. The shaft 44 passes axially through the magnet holder 41. The outer peripheral surface of the shaft 44 is fixed to the inner peripheral surface of the magnet holder 41. This allows the shaft 44 to rotate together with the rotor 40 around the central axis J. The upper end of the shaft 44 protrudes outside the housing 11 through the top plate hole 18c. The upper portion of the shaft 44 is supported by the first bearing 75 so as to be rotatable around the central axis J. The lower end of the shaft 44 protrudes outside the housing 11 through the bottom plate hole 15a. The lower portion of the shaft 44 is supported by the second bearing 76 so as to be rotatable around the central axis J.

[0046] Rotating blades (not shown) are fixed to the shaft 44. As a result, when the shaft 44 rotates around the central axis J, the rotating blades also rotate around the central axis J. When the rotating blades rotate around the central axis J, the unmanned aerial vehicle can fly. When the rotating blades rotate around the central axis J, an air flow is generated from the rotating blades toward the housing 11. This allows air to be supplied to the housing 11, particularly to each heat dissipation section 27, thereby increasing the amount of heat dissipated from the housing 11 to the outside of the motor 10.

[0047] The stator 50 faces the rotor 40 with a gap in the axial direction. In this embodiment, the motor 10 includes two stators 50. The two stators 50 include a first stator 51 and a second stator 56. In this embodiment, the motor 10 is a double-stator, single-rotor axial gap motor. Note that the motor 10 may have only one stator 50. In this case, the stator 50 may be disposed above the rotor 40 or below the rotor 40.

[0048] The first stator 51 is disposed below the rotor 40. The first stator 51 faces the rotor 40 with a gap therebetween in the axial direction. The first stator 51 includes a stator core 52, an insulator 53, a coil portion 54, and a lid portion 55.

[0049] The stator core 52 has a back yoke 52a and teeth 52c. The back yoke 52a is a generally annular plate centered on the central axis J. The plate surface of the back yoke 52a faces the axial direction. The back yoke 52a is disposed between the first peripheral wall 14 and the first stator holding portion 15c. In this embodiment, the back yoke 52a is fixed to the inner peripheral surface of the first peripheral wall 14, the outer peripheral surface of the first stator holding portion 15c, and the bottom plate 15 with an adhesive. This fixes the first stator 51 to the first housing 13.

[0050] The teeth 52c are columnar and protrude upward from the back yoke 52a. The teeth 52c face the magnets 42 of the rotor 40 at an axial distance. This causes the stator core 52 to face the rotor 40 in the axial direction. As shown in FIG. 5 , the teeth 52c are generally rectangular with long sides extending radially. The stator core 52 has a plurality of teeth 52c. In this embodiment, the stator core 52 has 48 teeth 52c. The number of teeth 52c included in the stator core 52 may be 47 or less, or may be 49 or more. The teeth 52c are arranged at generally equal intervals along the circumferential direction.

[0051] 3 insulates the stator core 52 from the coil portion 54. The insulators 53 are attached to the stator core 52. In this embodiment, the first stator 51 has 48 insulators 53. Each insulator 53 is attached to a different tooth portion 52c.

[0052] The coil portions 54 are attached to the tooth portions 52c via insulators 53. As a result, the coil portions 54 are attached to the stator core 52. The coil portions 54 are configured by coils wound around the outer circumferential surfaces of the tooth portions 52c. The first stator 51 has a plurality of coil portions 54. As shown in FIG. 5 , in this embodiment, the first stator 51 has 48 coil portions 54. Each coil portion 54 is attached to a different tooth portion 52c. The coil portions 54 are arranged at approximately equal intervals along the circumferential direction. Each coil portion 54 is electrically connected to a power supply device of the unmanned aerial vehicle via a busbar unit 70. When current is supplied to each coil portion 54 from the power supply device, each coil portion 54 forms an electromagnet with its magnetic poles facing the axial direction. When current is supplied to the coil portions 54, Joule heat is generated in the coil portions 54. As a result, the temperature of the coil portions 54 increases when the motor 10 is driven. That is, when the motor 10 is driven, the temperature of the first stator 51 increases.

[0053] As shown in Fig. 2, the lid portion 55 is annular and has a plate shape that surrounds the upper portion of the tooth portion 52c. The plate surface of the lid portion 55 faces the axial direction. Although not shown, the lid portion 55 is fixed to the insulator 53. The lid portion 55 supports the coil portion 54 from above in the axial direction. This prevents the coil portion 54 from moving upward.

[0054] The second stator 56 is disposed above the rotor 40. The second stator 56 faces the rotor 40 with an axial gap between them. The second stator 56 includes a stator core 57, an insulator 53, a coil portion 58, and a cover portion 55. In the present embodiment, the shape and arrangement of each component of the second stator 56 are plane-symmetrical to the shape and arrangement of each component of the first stator 51, with respect to a plane perpendicular to the axial direction. Therefore, in the following description of the second stator 56, description of the same shape, arrangement, and the like as those of the first stator 51 may be omitted.

[0055] The stator core 57 has a back yoke 57a and teeth 57c. The back yoke 57a is disposed between the second peripheral wall 17 and the second stator holding portion 18e. In the present embodiment, the back yoke 57a is fixed to the inner peripheral surface of the second peripheral wall 17, the outer peripheral surface of the second stator holding portion 18e, and the top plate 18 with an adhesive. In this way, the second stator 56 is fixed to the second housing 16.

[0056] The teeth 57c are columnar and protrude downward from the back yoke 57a. The teeth 57c face the magnets 42 of the rotor 40 at intervals in the axial direction. This causes the stator core 57 to face the rotor 40 in the axial direction. Although not shown, the stator core 57 has 48 teeth 57c. The teeth 57c are arranged at approximately equal intervals in the circumferential direction.

[0057] Although not shown, the insulators 53 insulate the stator core 57 from the coil portion 58. The insulators 53 are attached to the stator core 57. The insulators 53 are attached to different tooth portions 57c.

[0058] The coil portions 58 are attached to the tooth portions 57c via the insulators 53. As a result, the coil portions 58 are attached to the stator core 57. In this embodiment, the second stator 56 has 48 coil portions 58. Each coil portion 58 is attached to a different tooth portion 57c. Each coil portion 58 is electrically connected to a power supply device of the unmanned air vehicle via a busbar unit 70. When current is supplied to each coil portion 58 from the power supply device, each coil portion 58 forms an electromagnet with its magnetic poles facing the axial direction. When current is supplied to the coil portions 58, Joule heat is generated in the coil portions 58. As a result, the temperature of the coil portions 58 increases when the motor 10 is driven. That is, when the motor 10 is driven, the temperature of the second stator 56 increases.

[0059] The cover 55 is an annular plate that surrounds the lower portion of the tooth 57c. The cover 55 supports the coil 58 from below in the axial direction, thereby preventing the coil 58 from moving downward.

[0060] The busbar unit 70 electrically connects the stator 50 and the power supply device. The busbar unit 70 has a substantially circular ring shape centered on the central axis J. The busbar unit 70 has a busbar holder 71 and a plurality of busbars 72. The busbar holder 71 has a substantially circular ring shape centered on the central axis J. The busbar holder 71 is made of resin. The busbar holder 71 holds each busbar 72. The busbar holder 71 insulates each busbar 72 from one another.

[0061] Each bus bar 72 extends in the circumferential direction. In this embodiment, currents of different phases are supplied to each bus bar 72. Each bus bar 72 is electrically connected to a power supply device. In this embodiment, the motor 10 has two bus bar units 70.

[0062] One busbar unit 70a is disposed radially inside the first stator 51. The bus bars 72 of the busbar unit 70a are electrically connected to the coil portions 54 of the first stator 51. This allows current to be supplied from the power supply to the coil portions 54. The other busbar unit 70b is disposed radially inside the second stator 56. The bus bars 72 of the other busbar unit 70b are electrically connected to the coil portions 58 of the second stator 56. This allows current to be supplied from the power supply to the coil portions 58.

[0063] When current is sequentially supplied from a power supply (not shown) to each of the multiple coil portions 54 of the first stator 51 and the multiple coil portions 58 of the second stator 56, the coil portions 54, 58 sequentially form electromagnets with their magnetic poles facing the axial direction. This creates a rotating magnetic field between the magnet 42 of the rotor 40 and each of the teeth 52c, 57c of the stator 50, causing the rotor 40 and the shaft 44 to rotate about the central axis J. This causes the rotor blades (not shown) fixed to the shaft 44 to rotate about the central axis J.

[0064] The resin portion 60 shown in FIG. 2 surrounds the stator 50. The resin portion 60 contacts both the stator 50 and the housing main body 12. The resin portion 60 is made of resin. Thermosetting resins such as epoxy resin and silicone resin can be used as the material for the resin portion 60. In this embodiment, the resin portion 60 has a first resin portion 61 and a second resin portion 62. The first resin portion 61 surrounds the first stator 51. The second resin portion 62 surrounds the second stator 56.

[0065] As shown in FIG. 3 , the first resin portion 61 is filled between the housing body 12 and the first stator holding portion 15c and the first stator 51. More specifically, the first resin portion 61 is filled between the housing body 12 and the first stator holding portion 15c and the coil portions 54. As a result, the first resin portion 61 contacts the first stator 51 and the housing body 12. The first resin portion 61 contacts the first protrusion 21a and the coil portions 54. As a result, the resin portion 60 contacts at least a portion of the protrusion 21 and at least a portion of the coil portions 54. The first resin portion 61 enters between the circumferentially adjacent first protrusions 21a and contacts the inner circumferential surface of the tubular portion 12a. In the following description, the space between the circumferentially adjacent first protrusions 21a may be referred to as a recess of the housing 11.

[0066] Although not shown, similar to the first resin portion 61 described above, the second resin portion 62 is filled between the housing main body 12 and the second stator holding portion 18e and each of the coil portions 58. As a result, the second resin portion 62 contacts each of the second stator 56 and the housing main body 12. The second resin portion 62 contacts the first protrusion 21a and each of the coil portions 58. As a result, the resin portion 60 contacts each of at least a portion of the protrusion 21 and at least a portion of the coil portions 58. The second resin portion 62 enters the recessed portion of the housing 11 and contacts the inner circumferential surface of the tubular portion 12a.

[0067] According to this embodiment, the motor 10 includes a rotor 40 rotatable about a central axis J, a stator 50 facing the rotor 40 at a distance, and a housing 11 accommodating the rotor 40 and the stator 50. The housing 11 includes a housing main body 12 surrounding the stator 50 and a plurality of heat dissipation portions 27 protruding from the outer surface of the housing main body 12 to the outside of the housing main body 12. The inner surface of the housing main body 12 is provided with a plurality of protrusions 21 protruding to the inside of the housing main body 12, at least a portion of each of the plurality of protrusions 21 facing the stator 50, and each of the plurality of heat dissipation portions 27 overlaps with the protrusion 21 when viewed from the protruding direction of the heat dissipation portions 27. Therefore, as shown in FIGS. 3 and 4 , the distance between the tip of the protrusion 21 and the stator 50 can be shorter than the distance between the inner surface of the housing main body 12 and the stator 50. This reduces the thermal resistance between the stator 50 and the housing 11 compared to when the housing main body 12 does not have the protrusions 21, thereby increasing the amount of heat transferred from the stator 50 to the housing 11. Furthermore, as described above, because each heat dissipation portion 27 overlaps with each protrusion 21 when viewed from the direction in which the heat dissipation portion 27 protrudes, it is easy to position each heat dissipation portion 27 close to the protrusions 21. This reduces the thermal resistance between each heat dissipation portion 27 and each protrusion 21. This increases the amount of heat transferred from each protrusion 21 to each heat dissipation portion 27. This increases the amount of heat transferred from the stator 50 to the outside of the motor 10 via the housing 11. This prevents the temperature of the stator 50 from becoming too high. Furthermore, by increasing the thickness of the housing main body 12 without providing the protrusions 21, the volume of the housing main body 12 can be reduced compared to when the entire inner surface of the housing main body 12 is brought closer to the stator 50. This reduces the weight of the housing 11. Therefore, while reducing the weight of the housing 11, it is possible to prevent the temperature of the stator 50 from becoming too high.

[0068] Furthermore, in this embodiment, the multiple protrusions 21 can increase the surface area of ​​the inner surface of the housing 11. This can more effectively increase the amount of heat transferred from the stator 50 to the housing 11. Therefore, the amount of heat dissipated from the stator 50 to the outside of the motor 10 via the housing 11 can be more effectively increased, and the temperature of the stator 50 can be more effectively prevented from becoming too high.

[0069] According to this embodiment, the housing main body 12 has a cylindrical portion 12a that radially faces the stator 50 and extends in the axial direction. The heat dissipation portions 27 include a plurality of first heat dissipation portions 27a that protrude radially outward from a radially outward surface of the cylindrical portion 12a. The protrusions 21 include a plurality of first protrusions 21a that protrude radially inward from a radially inward surface of the cylindrical portion 12a. As viewed from the radial direction, each of the first heat dissipation portions 27a overlaps with a different first protrusion 21a. Therefore, the first protrusions 21a can increase the amount of heat transferred from the stator 50 to the housing 11. Furthermore, the thermal resistance between each of the first heat dissipation portions 27a and each of the first protrusions 21a can be reduced, thereby increasing the amount of heat transferred from each of the first protrusions 21a to each of the first heat dissipation portions 27a. These configurations increase the amount of heat dissipated from the stator 50 to the outside in the radial direction of the motor 10 via the housing 11. This prevents the temperature of the stator 50 from becoming too high.

[0070] According to this embodiment, the housing main body 12 has a top plate 18 that faces the stator 50 in the axial direction and extends perpendicular to the axial direction. The heat dissipation portions 27 include a plurality of second heat dissipation portions 27e that protrude in the axial direction from the axial surface of the top plate 18. The protrusions 21 include a plurality of second protrusions 21e that protrude in the axial direction from the axial surface of the top plate 18. When viewed from the axial direction, each of the second heat dissipation portions 27e overlaps with a different second protrusion 21e. Therefore, the second protrusions 21e can increase the amount of heat transferred from the stator 50 to the housing 11. Furthermore, the thermal resistance between each second heat dissipation portion 27e and each second protrusion 21e can be reduced, thereby increasing the amount of heat transferred from each second protrusion 21e to each second heat dissipation portion 27e. This increases the amount of heat dissipated from the stator 50 to the outside of the motor 10 in the axial direction via the housing 11. Therefore, the temperature of the stator 50 can be more effectively prevented from becoming too high.

[0071] According to this embodiment, the housing body 12, the plurality of protrusions 21, and the plurality of heat dissipation portions 27 are each part of a single member. Therefore, it is easier to reduce the thermal resistance between each protrusion 21 and each heat dissipation portion 27 compared to when the housing body 12, each protrusion 21, and each heat dissipation portion 27 are separate members. This more effectively increases the amount of heat that can be dissipated from the stator 50 to the outside of the housing 11 via the housing 11. Therefore, it is more effectively possible to prevent the temperature of the stator 50 from becoming too high.

[0072] Furthermore, in this embodiment, the rigidity of the housing 11 can be increased compared to when the housing main body 12, the plurality of protrusions 21, and the plurality of heat dissipation portions 27 are each made of separate members. This reduces the amount of elastic deformation of the housing 11 while the motor 10 is running, thereby suppressing fluctuations in the position of the rotor 40 relative to the stator 50. This suppresses fluctuations in the magnetic force applied to the magnets 42 of the rotor 40, thereby stabilizing the output torque of the motor 10.

[0073] According to this embodiment, the dimension Lh of the housing main body 12 in the direction in which the protrusion 21 protrudes is greater than the dimension Ltr of the protrusion 21. This increases the rigidity of the housing 11 compared to when the dimension Lh of the housing main body 12 in the direction in which the protrusion 21 protrudes is smaller than the dimension Ltr of the protrusion 21. This more effectively suppresses fluctuations in the magnetic force applied to the magnet 42 of the rotor 40 while the motor 10 is running, thereby more effectively stabilizing the output torque of the motor 10.

[0074] According to this embodiment, the multiple protrusions 21 are spaced apart from one another in the circumferential direction, and the circumferential dimension Ltc of each protrusion 21 is greater than the distance Lmc between adjacent protrusions 21 in the circumferential direction. Therefore, the cross-sectional area of ​​each protrusion 21 as viewed from the direction in which it protrudes can be increased compared to when the circumferential dimension Ltc of each protrusion 21 is smaller than the distance Lmc between the adjacent protrusions 21. This reduces the thermal resistance between the stator 50 and the protrusions 21 and the thermal resistance between the protrusions 21 and the housing main body 12. This effectively increases the amount of heat dissipated from the stator 50 to the outside of the motor 10 via the housing 11, thereby effectively preventing the temperature of the stator 50 from becoming too high.

[0075] According to this embodiment, the plurality of protrusions 21 are spaced apart from one another in the circumferential direction, and the circumferential dimension Ltc of the portion of each of the plurality of protrusions 21 connected to the housing main body 12 is greater than the circumferential dimension Lti of the tip end of each of the plurality of protrusions 21. Therefore, the thermal resistance between each protrusion 21 and the housing main body 12 can be reduced compared to when the circumferential dimension Ltc of the portion of each protrusion 21 connected to the housing main body 12 is smaller than the circumferential dimension Lti of the tip end of each protrusion 21. Therefore, the amount of heat dissipated from the stator 50 to the outside of the motor 10 via the housing 11 can be more suitably increased, and the temperature of the stator 50 can be more suitably prevented from becoming too high.

[0076] According to this embodiment, motor 10 includes resin portion 60 that contacts both stator 50 and housing main body 12. This reduces the thermal resistance between stator 50 and housing 11 compared to a motor 10 that does not include resin portion 60. This more effectively increases the amount of heat dissipated from stator 50 to the outside of motor 10 via resin portion 60 and housing 11, thereby more effectively preventing the temperature of stator 50 from becoming too high.

[0077] According to this embodiment, the stator 50 faces the rotor 40 with an axial gap therebetween, and the stator 50 has stator cores 52, 57 that face the rotor 40 in the axial direction, and coil portions 54, 58 attached to the stator cores 52, 57, and the resin portion 60 contacts at least a portion of the plurality of protrusions 21 and at least a portion of the coil portions 54, 58. Therefore, Joule heat generated in the coil portions 54, 58 can be more effectively dissipated to the outside of the motor 10 via the resin portion 60 and the housing 11. Therefore, the temperature of the coil portions 54, 58 can be prevented from becoming too high, and therefore the temperature of the stator 50 can be more effectively prevented from becoming too high.

[0078] 6, a motor 210 of this embodiment is a disk-shaped motor centered on a central axis J. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

[0079] The motor 210 of this embodiment is mounted on, for example, an unmanned aerial vehicle and used as a drive device for rotating the rotors of the unmanned aerial vehicle about a central axis J. The motor 210 is a thin motor whose axial dimension is smaller than its radial dimension. As shown in FIG. 7 , the motor 210 is a radial gap motor in which the stator 250 is disposed radially outward of the rotor 240 and faces the rotor 240 with a radial gap therebetween. The motor 210 includes a housing 211, the rotor 240, a shaft 244, the stator 250, a resin part 260, and a busbar unit 270.

[0080] The housing 211 has a substantially cylindrical shape centered on the central axis J. The housing 211 accommodates the rotor 240, the stator 250, the resin portion 260, and the bus bar unit 270 therein. The housing 211 is made of metal. In this embodiment, the housing 211 is made of aluminum. The housing 211 may be made of a material other than aluminum. The housing 211 has a first housing 214, a top plate portion 230, a housing main body portion 212, and a heat dissipation portion 227.

[0081] The first housing 214 has a generally cylindrical shape and extends axially about the central axis J. The first housing 214 has an opening 214a that opens to the upper side. The rotor 240, the stator 250, the resin part 260, and the busbar unit 270 are accommodated inside the first housing 214. The first housing 214 has a tubular part 216 and a bottom plate part 225.

[0082] The cylindrical portion 216 has a generally cylindrical shape extending in the axial direction around the central axis J. The cylindrical portion 216 surrounds each of the rotor 240, the stator 250, the resin portion 260, and the busbar unit 270 from the radially outer side. The cylindrical portion 216 faces the stator 250 in the radial direction. In this embodiment, the housing main body 212 is the cylindrical portion 216. That is, the housing main body 212 has the cylindrical portion 216. The cylindrical portion 216 has a first cylindrical portion 217 and a second cylindrical portion 220.

[0083] The first cylindrical portion 217 is a lower portion of the cylindrical portion 216. The first cylindrical portion 217 has a generally cylindrical shape extending in the axial direction centered on the central axis J. The first cylindrical portion 217 is provided with a stepped surface 217a and a protruding portion 218. The stepped surface 217a is an upward-facing surface provided on the inner surface of the first cylindrical portion 217. When viewed in the axial direction, the stepped surface 217a has a generally annular shape centered on the central axis J. The inner diameter of the portion of the first cylindrical portion 217 above the stepped surface 217a is smaller than the inner diameter of the portion of the first cylindrical portion 217 below the stepped surface 217a.

[0084] The protruding portion 218 protrudes radially inward from the inner surface of the first cylindrical portion 217. The protruding portion 218 has a generally annular plate shape centered on the central axis J. The plate surface of the protruding portion 218 faces the axial direction. The protruding portion 218 is arranged below the stator 250. The protruding portion 218 faces the stator 250 with a gap therebetween in the axial direction. The protruding portion 218 is arranged above the busbar unit 270.

[0085] The second cylindrical portion 220 is the upper portion of the cylindrical portion 216. The second cylindrical portion 220 has a substantially cylindrical shape extending in the axial direction around the central axis J. The lower end of the second cylindrical portion 220 is axially connected to the first cylindrical portion 217. The upper end of the second cylindrical portion 220 is the upper end of the cylindrical portion 216. As shown in FIG. 8 , the inner diameter of the second cylindrical portion 220 is smaller than the inner diameter of the first cylindrical portion 217. The outer diameter of the second cylindrical portion 220 is the same as the outer diameter of the first cylindrical portion 217.

[0086] 7, the bottom plate portion 225 has a generally annular plate shape centered on the central axis J. The plate surface of the bottom plate portion 225 faces the axial direction. The radial outer edge of the bottom plate portion 225 is connected to the lower end of the cylindrical portion 216. The bottom plate portion 225 is provided with a second bearing holder 225a.

[0087] The second bearing holder 225a protrudes upward from the bottom plate portion 225. The second bearing holder 225a is generally cylindrical and centered on the central axis J. The second bearing holder 225a opens upward. A second bearing 276 is attached to the inner circumferential surface of the second bearing holder 225a. The second bearing 276 is generally annular and centered on the central axis J. In this embodiment, the second bearing 276 is a sliding bearing. The second bearing 276 may also be a ball bearing.

[0088] The top plate portion 230 has a substantially annular plate shape centered on the central axis J. The top plate portion 230 is fixed to the upper end of the cylindrical portion 216. As a result, the top plate portion 230 closes the opening 214a of the first housing 214 from above. The top plate portion 230 is provided with a hole portion 230a and a first bearing holder 230c. The hole portion 230a is a hole that penetrates the top plate portion 230 in the axial direction. When viewed in the axial direction, the hole portion 230a has a circular shape centered on the central axis J.

[0089] The first bearing holder 230c protrudes downward from the top plate portion 230. The first bearing holder 230c is generally cylindrical and centered on the central axis J. The first bearing holder 230c opens downward. A first bearing 275 is attached to the inner peripheral surface of the first bearing holder 230c. The first bearing 275 is generally annular and centered on the central axis J. In this embodiment, the first bearing 275 is a sliding bearing. The first bearing 275 may also be a ball bearing.

[0090] As described above, in this embodiment, the housing body 212 is the cylindrical portion 216. The housing body 212 surrounds the stator 250 from the radial outside. As shown in Fig. 9 , a protrusion 221 is provided on the inner surface of the housing body 212.

[0091] The protrusions 221 protrude from the inner surface of the housing main body 212 toward the inside of the housing main body 212. In the present embodiment, the housing main body 212 is provided with a plurality of protrusions 221. The plurality of protrusions 221 include a plurality of first protrusions 221a. The plurality of protrusions 221 may include other protrusions in addition to the plurality of first protrusions 221a.

[0092] Each of the multiple first protrusions 221a is rib-shaped and protrudes radially inward from the radially inward surface of the housing main body 212, i.e., the cylindrical portion 216. The plate surface of the first protrusion 221a faces the circumferential direction. Each of the multiple first protrusions 221a is spaced apart from one another in the circumferential direction. That is, each of the multiple protrusions 221a is spaced apart from one another in the circumferential direction. When viewed from the axial direction, each first protrusion 221a has a generally trapezoidal shape with its short side positioned radially inward and its long side positioned radially outward. Therefore, the circumferential dimension of each first protrusion 221a increases radially outward. Therefore, the circumferential dimension Ltc of the portion of the first protrusion 221a connected to the housing main body 212 is greater than the circumferential dimension Lti of the tip of the first protrusion 221a. As shown in Fig. 8 , each first protrusion 221a protrudes radially inward from the surface of the second cylindrical portion 220 facing radially inward. Each first protrusion 221a extends in the axial direction. In the axial direction, the upper end of each first protrusion 221a is located above the stator 250. In the axial direction, the lower end of each first protrusion 221a is located at the same position as the lower end of the second cylindrical portion 220. At least some of the multiple protrusions 221 face the stator 250. In the radial direction, the radially inner end of each first protrusion 221a is located at the same position as the inner circumferential surface of the first cylindrical portion 217.

[0093] 9 , in the present embodiment, the dimension Lh of the cylindrical portion 216, i.e., the dimension of the housing main body 212, in the direction in which the first protrusions 221a protrude, i.e., the radial direction, is greater than the dimension Ltr of the first protrusions 221a. The circumferential dimension Ltc of the first protrusions 221a is greater than the distance Lmc between adjacent first protrusions 221a in the circumferential direction.

[0094] As shown in FIG. 10 , the heat dissipation portion 227 protrudes from the outer surface of the housing main body 212 to the outside of the housing main body 212. The heat dissipation portion 227 is plate-shaped with its plate surface facing the circumferential direction. In this embodiment, the housing 211 has multiple heat dissipation portions 227. The heat dissipation portions 227 are spaced apart from one another in the circumferential direction. This increases the surface area of ​​the outer surface of the housing 211, thereby increasing the amount of heat dissipated from the housing 211 to the outside of the motor 210. In this embodiment, the multiple heat dissipation portions 227 include multiple first heat dissipation portions 227a. Note that the multiple heat dissipation portions 227 may include heat dissipation portions other than the multiple first heat dissipation portions 227a.

[0095] Each of the multiple first heat dissipation portions 227a is a plate-like member that protrudes radially outward from the surface of the housing main body 212, i.e., the cylindrical portion 216, that faces radially outward. As shown in Fig. 6, each first heat dissipation portion 227a extends in the axial direction. As shown in Fig. 7, the upper end of each first heat dissipation portion 227a is located at the same position as the upper end of the cylindrical portion 216 in the axial direction. The lower end of each first heat dissipation portion 227a is located at the same position as the lower end of the cylindrical portion 216 in the axial direction.

[0096] 9 , when viewed from the radial direction, each first heat dissipation portion 227a overlaps with a different first protrusion 221a. That is, when viewed from the radial direction, i.e., the direction in which the heat dissipation portion 227 protrudes, each heat dissipation portion 227 overlaps with the protrusion 221. This allows each heat dissipation portion 227 to be disposed close to the protrusion 221. Therefore, the thermal resistance between the protrusion 221 and the heat dissipation portion 227 can be reduced.

[0097] In this embodiment, the housing main body 212, the plurality of heat dissipation portions 227, and the plurality of protrusions 221 are each part of the first housing 214. Therefore, the housing main body 212, the plurality of heat dissipation portions 227, and the plurality of protrusions 221 are each part of a single member.

[0098] 7 , the rotor 240 is substantially annular and has a central axis J as its center. The rotor 240 is rotatable about the central axis J. The rotor 240 faces the stator 250 with a gap therebetween in the radial direction. The rotor 240 has a magnet holder 241 and a magnet 242.

[0099] The magnet holder 241 has a substantially circular ring shape centered on the central axis J. The magnet 242 has a substantially circular ring shape centered on the central axis J. The magnet 242 is fixed to a surface of the magnet holder 241 that faces radially outward. The magnet 242 has magnetic poles that face radially. The magnet 242 faces the stator 250 with a gap therebetween in the radial direction.

[0100] The shaft 244 has a generally cylindrical shape extending axially around the central axis J. The shaft 244 is disposed radially inward of the rotor 240 and the stator 250. The shaft 244 passes axially through the magnet holder 241. The outer circumferential surface of the shaft 244 is fixed to the inner circumferential surface of the magnet holder 241. This allows the shaft 244 to rotate together with the rotor 240 around the central axis J. The upper end of the shaft 244 protrudes outside the housing 211 through the hole 230a. The upper portion of the shaft 244 is supported by a first bearing 275 so as to be rotatable around the central axis J. The lower portion of the shaft 244 is supported by a second bearing 276 so as to be rotatable around the central axis J. A rotor (not shown) of the unmanned aerial vehicle is fixed to the shaft 244. This allows the rotor to rotate around the central axis J when the shaft 244 rotates around the central axis J. When the rotor rotates around the central axis J, the unmanned aerial vehicle can fly.

[0101] The stator 250 faces the rotor 240 with a gap therebetween in the radial direction. The stator 250 includes a stator core 252, an insulator 253, and a coil portion 254.

[0102] The stator core 252 has a generally circular ring shape centered on the central axis J. The stator core 252 surrounds the rotor 240 from the radially outer side. The stator core 252 faces the rotor 240 with a gap therebetween in the radial direction. As shown in FIG. 11 , the stator core 252 has a core back portion 252 a and teeth portions 252 c.

[0103] The core back portion 252a has a substantially circular ring shape centered on the central axis J. The outer peripheral surface of the core back portion 252a is fixed to the inner peripheral surface of the cylindrical portion 216. This fixes the stator 250 to the housing 211. As shown in FIG. 7 , the radially outer portion of the surface of the core back portion 252a facing downward comes into axial contact with the stepped surface 217a. This determines the axial position of the stator 250 relative to the housing 211.

[0104] As shown in Fig. 11 , the teeth 252c protrude radially inward from the core back portion 252a. The teeth 252c face the magnets 242 of the rotor 240 at intervals in the radial direction. The stator core 252 has a plurality of teeth 252c. In this embodiment, the stator core 252 has 72 teeth 252c. The number of teeth 252c that the stator core 252 has may be 71 or less, or 73 or more. The teeth 252c are arranged at approximately equal intervals in the circumferential direction.

[0105] 7 insulates the stator core 252 from the coil portion 254. The insulator 253 is attached to the stator core 252. In this embodiment, the insulator 253 is attached to each tooth portion 252c.

[0106] The coil portions 254 are attached to the tooth portions 252c via insulators 253. As a result, the coil portions 254 are attached to the stator core 252. The coil portions 254 are configured by coils wound around the tooth portions 252c. The stator 250 has a plurality of coil portions 254. As shown in FIG. 11 , in this embodiment, the stator 250 has 72 coil portions 254. Each coil portion 254 is attached to a different tooth portion 252c. The coil portions 254 are arranged at approximately equal intervals along the circumferential direction. Each coil portion 254 is electrically connected to a power supply device of the unmanned air vehicle via a busbar unit 270. When current is supplied to each coil portion 254 from the power supply device, each coil portion 254 forms an electromagnet with its magnetic poles facing radially. When current is supplied to the coil portions 254, Joule heat is generated in the coil portions 254. As a result, the temperature of the coil portion 254 increases when the motor 210 is driven. That is, the temperature of the stator 250 increases when the motor 210 is driven. As shown in Fig. 7, the coil portion 254 has coil end portions 254a and 254b.

[0107] The coil end portions 254a, 254b are portions of the coil portion 254 that protrude axially from the stator core 252. The coil end portion 254a does not contact the stator core 252. As described above, when a current is supplied to the coil portion 254, Joule heat is generated in the coil portion 254. Therefore, Joule heat generated in the portion of the coil portion 254 that contacts the stator core 252 is easily transferred to the housing 211 via the stator core 252. In contrast, Joule heat generated in the coil end portion 254a is less likely to be transferred to the housing 211 via the stator core 252, so the temperature of the coil end portion 254a is likely to increase. Each coil portion 254 has two coil end portions 254a, 254b. One coil end portion 254a protrudes upward from the stator core 252. The other coil end portion 254b protrudes downward from the stator core 252.

[0108] The busbar unit 270 electrically connects the stator 250 and the power supply device. The busbar unit 270 has a substantially circular ring shape centered on the central axis J. The busbar unit 270 is disposed below the protrusion 218. The busbar unit 270 has a busbar holder 271 and a plurality of busbars 272. The busbar holder 271 has a substantially circular ring shape centered on the central axis J. Although not shown, each busbar 272 is electrically connected to the power supply device. Each busbar 272 is electrically connected to each coil portion 254 of the stator 250. This allows current to be supplied from the power supply device to each coil portion 254.

[0109] When current is sequentially supplied to each of the multiple coil portions 254 of the stator 250 from a power supply device (not shown), the coil portions 254 sequentially form electromagnets with magnetic poles facing radially. As a result, a rotating magnetic field is formed between the magnet 242 of the rotor 240 and each of the teeth 252c of the stator 250, and the rotor 240 and the shaft 244 each rotate about the central axis J. As a result, the rotor blades fixed to the shaft 244 rotate about the central axis J.

[0110] The resin portion 260 is in contact with both the stator 250 and the housing main body 212. In this embodiment, the resin portion 260 has a first resin portion 261 and a second resin portion 262.

[0111] As shown in Fig. 8 , the first resin portion 261 is filled between one of the coil end portions 254a and the housing main body 212. The first resin portion 261 contacts both the one of the coil end portions 254a and the housing main body 212. As a result, the resin portion 260 contacts both the stator 250 and the housing main body 212. As shown in Fig. 9 , the first resin portion 261 contacts the protruding portion 221. Therefore, the resin portion 260 contacts at least a portion of each of the protruding portions 221 and at least a portion of the coil end portion 254a. The first resin portion 261 enters the recessed portion of the housing 211 and contacts the inner circumferential surface of the tubular portion 216.

[0112] As shown in FIG. 7 , the second resin portion 262 fills the gap between the other coil end portion 254b and the housing main body 212. The second resin portion 262 contacts both the other coil end portion 254b and the housing main body 212. This allows the resin portion 260 to contact both the stator 250 and the housing main body 212. The second resin portion 262 reduces the thermal resistance between the other coil end portion 254b and the housing 211, thereby increasing the amount of heat dissipated from the other coil end portion 254b to the outside of the motor 210 via the second resin portion 262 and the housing 211. This prevents the temperature of the other coil end portion 254b from becoming too high, thereby preventing deterioration of the other coil end portion 254b. Other configurations of the resin portion 260 of this embodiment are similar to those of the resin portion 60 of the first embodiment described above.

[0113] According to this embodiment, the housing 211 has a housing main body 212 that surrounds the stator 250 and a plurality of heat dissipation portions 227 that protrude from the outer surface of the housing main body 212 to the outside of the housing main body 212. The inner surface of the housing main body 212 is provided with a plurality of protrusions 221 that protrude inward of the housing main body 212, and at least a portion of each of the plurality of protrusions 221 faces the stator 250. When viewed from the protruding direction of the heat dissipation portions 227, each of the plurality of heat dissipation portions 227 overlaps with the protrusion 221. Therefore, as in the first embodiment described above, as shown in FIG. 9 , the distance between the tip of the protrusion 221 and the stator 250 can be made shorter than the distance between the inner surface of the housing main body 212 and the stator 250. This reduces the thermal resistance between the stator 250 and the housing 211, thereby increasing the amount of heat transferred from the stator 250 to the housing 211. Furthermore, as described above, when viewed from the direction in which the heat dissipation portions 227 protrude, each heat dissipation portion 227 overlaps with each protrusion 221, thereby reducing the thermal resistance between each heat dissipation portion 227 and each protrusion 221. This increases the amount of heat dissipated from the stator 250 to the outside of the motor 210 via the housing 211. This prevents the temperature of the stator 250 from becoming too high. Furthermore, by increasing the thickness of the housing main body 212 without providing the protrusions 221, the volume of the housing main body 212 can be reduced compared to a configuration in which the entire inner surface of the housing main body 212 is brought closer to the stator 250. This allows the weight of the housing 211 to be reduced. Therefore, the weight of the housing 211 can be reduced while preventing the temperature of the stator 250 from becoming too high.

[0114] According to this embodiment, the heat dissipation portions 227 include a plurality of first heat dissipation portions 227a that protrude radially outward from the radially outward surface of the cylindrical portion 216, and the protrusions 221 include a plurality of first protrusions 221a that protrude radially inward from the radially inward surface of the cylindrical portion 216. When viewed from the radial direction, each of the first heat dissipation portions 227a overlaps with a different first protrusion 221a. Therefore, the first protrusions 221a can increase the amount of heat transferred from the stator 250 to the housing 211 and reduce the thermal resistance between each first heat dissipation portion 227a and each first protrusion 221a. This increases the amount of heat dissipated from the stator 250 to the outside of the motor 210 in the radial direction via the housing 211. This prevents the temperature of the stator 250 from becoming too high.

[0115] According to this embodiment, the housing main body 212, the plurality of protrusions 221, and the plurality of heat dissipation portions 227 are each part of a single member. Therefore, it is easier to reduce the thermal resistance between each protrusion 221 and each heat dissipation portion 227 compared to when the housing main body 212, each protrusion 221, and each heat dissipation portion 227 are separate members. This makes it possible to more effectively increase the amount of heat that can be dissipated from the stator 250 to the outside of the housing 211 via the housing 211. Therefore, it is possible to more effectively prevent the temperature of the stator 250 from becoming too high.

[0116] According to the present embodiment, motor 210 includes resin portion 260 that contacts both stator 250 and housing main body 212. This reduces the thermal resistance between stator 250 and housing 211 compared to a case in which motor 210 does not include resin portion 260. This more effectively increases the amount of heat dissipated from stator 250 to the outside of motor 210 via resin portion 260 and housing 211, thereby more effectively preventing the temperature of stator 250 from becoming too high.

[0117] According to this embodiment, the stator 250 is disposed radially outward of the rotor 240 and faces the rotor 240 with a radial gap therebetween. The stator 250 includes a stator core 252 that faces the rotor 240 in the radial direction and a coil portion 254 attached to the stator core 252. The coil portion 254 has a coil end portion 254a that protrudes axially from the stator core 252. The resin portion 260 contacts at least a portion of the plurality of protrusions 221 and at least a portion of the coil end portion 254a. Therefore, Joule heat generated in the coil end portion 254a can be more efficiently dissipated to the outside of the motor 210 via the resin portion 260 and the housing 211. This prevents the temperature of the coil end portion 254a from becoming too high, thereby preventing the coil portion 254 from deteriorating.

[0118] Furthermore, in this embodiment, as described above, the first resin portion 261 enters the recessed portion of the housing 211 and comes into contact with the inner circumferential surface of the cylindrical portion 216. As a result, if the first resin portion 261 attempts to peel off from the housing 211 while the motor 210 is running, the first resin portion 261 gets caught on the circumferentially facing surfaces of each protrusion 221. This prevents the first resin portion 261 from peeling off from the housing 211. Furthermore, the contact area between the resin portion 260 and the housing 211 can be increased. As a result, the thermal resistance between the resin portion 260 and the housing 211 can be stably reduced, and the temperature of the coil end portion 254a can be more effectively prevented from becoming too high.

[0119] The present invention is not limited to the above-described embodiment, and other configurations and methods may be adopted within the scope of the technical concept of the present invention. For example, the heat dissipation portion may be a plate-like member extending in the circumferential direction. In this case, it is preferable that the protrusions extend in the circumferential direction, and that each of the plurality of heat dissipation portions overlap with the protrusions when viewed from the direction in which the heat dissipation portion protrudes. This increases the amount of heat dissipated from the stator to the outside of the motor through the housing. Furthermore, each heat dissipation portion may be, for example, a cylindrical pin-like member protruding from the outer surface of the housing main body to the outside of the housing main body.

[0120] The heat dissipation portion may have a third heat dissipation portion protruding in the axial direction from the bottom plate portion. In this case, it is preferable that the protrusion portion has a third protrusion protruding in the axial direction from the bottom plate portion.

[0121] The configuration of the protrusions is not limited to this embodiment. For example, the dimension of the housing main body in the direction in which the protrusions protrude may be smaller than or equal to the dimension of the protrusions. The circumferential dimension of the protrusions may be smaller than or equal to the spacing between adjacent protrusions in the circumferential direction. Furthermore, the circumferential dimension Ltc of the portion of the protrusion connected to the housing main body may be smaller than or equal to the circumferential dimension of the tip of the protrusion.

[0122] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0123] The present technology can be configured as follows: (1) A motor including a rotor rotatable about a central axis, a stator facing the rotor with a gap therebetween, and a housing accommodating the rotor and the stator, wherein the housing has a housing main body surrounding the stator and a plurality of heat dissipation portions protruding from an outer surface of the housing main body to the outside of the housing main body, and a plurality of protrusions protruding to the inside of the housing main body are provided on an inner surface of the housing main body, at least a portion of each of the plurality of protrusions faces the stator, and each of the plurality of heat dissipation portions overlaps with the protrusion when viewed from a direction in which the heat dissipation portion protrudes. (2) The motor according to (1), wherein the housing main body has a cylindrical portion radially opposed to the stator and extending in the axial direction, the plurality of heat dissipation portions include a plurality of first heat dissipation portions protruding radially outward from a surface of the cylindrical portion facing radially outward, the plurality of protrusions include a plurality of first protrusions protruding radially inward from a surface of the cylindrical portion facing radially inward, and each of the plurality of first heat dissipation portions overlaps with a different first protrusion as viewed from the radial direction. (3) The motor according to (2), wherein the housing main body has a top plate portion axially opposed to the stator and extending in a direction perpendicular to the axial direction, the plurality of heat dissipation portions include a plurality of second heat dissipation portions protruding in the axial direction from a surface of the top plate facing in the axial direction, the plurality of protrusions include a plurality of second protrusions protruding in the axial direction from the surface of the top plate facing in the axial direction, and each of the plurality of second heat dissipation portions overlaps with a different second protrusion as viewed from the axial direction. (4) The motor according to any one of (1) to (3), wherein the housing main body, the plurality of protrusions, and the plurality of heat dissipation portions are each part of a single member. (5) The motor according to any one of (1) to (4), wherein a dimension of the housing main body in a direction in which the protrusions protrude is larger than a dimension of the protrusions. (6) The motor according to any one of (1) to (5), wherein the plurality of protrusions are provided at intervals from one another along a circumferential direction, and a dimension of the protrusions in the circumferential direction is larger than a distance between the protrusions arranged adjacent to each other in the circumferential direction.(7) The motor according to any one of (1) to (6), wherein the plurality of protrusions are spaced apart from one another along the circumferential direction, and a circumferential dimension of a portion of each of the plurality of protrusions connected to the housing main body is greater than a circumferential dimension of a tip end of each of the plurality of protrusions. (8) The motor according to any one of (1) to (7), further comprising a resin portion in contact with each of the stator and the housing main body. (9) The motor according to (8), wherein the stator faces the rotor at an interval in the axial direction, the stator has a stator core facing the rotor in the axial direction, and a coil portion attached to the stator core, and the resin portion contacts each of at least a portion of the plurality of protrusions and at least a portion of the coil portion. (10) The motor described in (8), wherein the stator is disposed radially outward of the rotor and faces the rotor with a radial gap therebetween, the stator has a stator core that faces the rotor in the radial direction and a coil portion attached to the stator core, the coil portion has coil end portions that protrude axially from the stator core, and the resin portion contacts at least some of the plurality of protrusions and at least some of the coil end portions.

[0124] DESCRIPTION OF SYMBOLS 10, 210... Motor, 11, 211... Housing, 12, 212... Housing main body, 12a, 216... Cylindrical portion, 18... Top plate portion, 21, 221... Convex portion, 21a, 221a... First convex portion, 27, 227... Heat dissipation portion, 27a, 227a... First heat dissipation portion, 27e... Second heat dissipation portion, 40, 240... Rotor, 50, 250... Stator, 52, 252... Stator core, 54, 254... Coil portion, 60, 260... Resin portion, 254a... Coil end portion, J... Central axis

Claims

1. A motor comprising: a rotor rotatable about a central axis; a stator facing said rotor with a gap between them; and a housing accommodating said rotor and said stator, wherein said housing has a housing main body surrounding said stator and a plurality of heat dissipation portions protruding from the outer surface of said housing main body to the outside of said housing main body, wherein an inner surface of said housing main body is provided with a plurality of protrusions protruding to the inside of said housing main body, at least a portion of each of said plurality of protrusions faces said stator, and when viewed from the direction in which said heat dissipation portions protrude, each of said plurality of heat dissipation portions overlaps with said protrusions.

2. The motor described in claim 1, wherein the housing main body has a cylindrical portion that faces radially opposite the stator and extends in the axial direction, the plurality of heat dissipation portions include a plurality of first heat dissipation portions that protrude radially outward from a surface of the cylindrical portion that faces radially outward, and the plurality of protrusions include a plurality of first protrusions that protrude radially inward from a surface of the cylindrical portion that faces radially inward, and when viewed radially, each of the plurality of first heat dissipation portions overlaps with a different first protrusion.

3. The motor described in claim 2, wherein the housing main body has a top plate portion that faces the stator in the axial direction and extends in a direction perpendicular to the axial direction, the plurality of heat dissipation portions include a plurality of second heat dissipation portions that protrude in the axial direction from the axial surface of the top plate portion, the plurality of protrusions include a plurality of second protrusions that protrude in the axial direction from the axial surface of the top plate portion, and when viewed in the axial direction, each of the plurality of second heat dissipation portions overlaps with a second protrusion that is different from the others.

4. The motor according to claim 1, wherein the housing body, the plurality of protrusions, and the plurality of heat dissipation portions are each part of a single member.

5. The motor according to claim 1, wherein the dimension of the housing body in the direction in which the protrusion projects is greater than the dimension of the protrusion.

6. The motor according to claim 1, wherein the plurality of protrusions are spaced apart from one another along the circumferential direction, and the circumferential dimension of each protrusion is greater than the distance between adjacent protrusions in the circumferential direction.

7. The motor according to claim 1, wherein each of the plurality of protrusions is spaced apart from one another along the circumferential direction, and the circumferential dimension of the portion of each of the plurality of protrusions that connects to the housing main body is greater than the circumferential dimension of the tip of each of the plurality of protrusions.

8. The motor according to any one of claims 1 to 7, further comprising a resin portion in contact with each of the stator and the housing main body.

9. The motor described in claim 8, wherein the stator faces the rotor with an axial gap between them, the stator has a stator core facing the rotor in the axial direction, and a coil portion attached to the stator core, and the resin portion contacts at least a portion of each of the plurality of protrusions and at least a portion of the coil portion.

10. The motor described in claim 8, wherein the stator is positioned radially outward of the rotor and faces the rotor with a radial gap therebetween, the stator has a stator core that faces the rotor in the radial direction and a coil portion attached to the stator core, the coil portion has coil end portions that protrude axially from the stator core, and the resin portion contacts at least a portion of each of the multiple protrusions and at least a portion of the coil end portions.

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