motor

Abstract

To provide a motor that further improves the stability of the support force of a stator.SOLUTION: A motor (1) includes a rotor (15), a stator (13) having a coil (139) arranged by opposing the rotor (15), and a holder (11) holding the stator (13). The stator (13) has an annular portion (132) and magnetic pole portions (133, 134) protruding toward the outer circumferential side from the annular portion (132) around which the coil (139) is wound. The holder (11) is in contact with the outer circumferential side in the radial direction of the annular portion (132) and the inner circumferential side in the radial direction of the annular portion (132).SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present invention relates to a motor.

Background Art

[0002] Conventionally, a support structure has been proposed in which a stator is fixed to the outer peripheral surface of a stator support cylinder portion on the outer peripheral side of a base portion to which a bearing portion is fixed, for example, by adhesion (see, for example, Patent Document 1). [[ID=十三]]

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the motor of Patent Document 1, there is a risk that the supporting force for supporting the stator may be reduced due to factors such as heat and vibration, and there has been a desire to stabilize the supporting force of the stator as compared with the conventional one.

[0005] The present invention has been made in view of the above background, and an example of the problem is to provide a motor with improved stability of the supporting force of the stator.

Means for Solving the Problems

[0006] The above problems are solved by the following present invention. That is, the motor of the present invention includes a rotor, a stator having a coil disposed opposite to the rotor, and a holder for holding the stator, the stator having an annular portion and a magnetic pole portion protruding from the annular portion toward the outer peripheral side around which the coil is wound, and the holder contacting the outer peripheral side in the radial direction of the annular portion and the inner peripheral side in the radial direction of the annular portion.

Brief Description of the Drawings

[0007] [Figure 1] This is a perspective view showing the overall configuration of an outer rotor type motor according to one embodiment of the present invention. [Figure 2] This is a perspective cross-sectional view showing the configuration of a motor according to one embodiment of the present invention. [Figure 3] This is a perspective cross-sectional view showing a motor according to one embodiment of the present invention, with the rotor, bearings, and rotor housing removed. [Figure 4] This is a perspective view showing the configuration of the stator holder of a motor according to one embodiment of the present invention, as viewed from above. [Figure 5] This is a perspective view showing the configuration of the stator core of a motor according to one embodiment of the present invention. [Figure 6] This is a perspective cross-sectional view showing the configuration of a stator holder according to one embodiment of the present invention. [Figure 7] This is a perspective cross-sectional view from above of a motor according to one embodiment of the present invention, showing the stator core being held in the stator holder. [Figure 8] This is a perspective cross-sectional view from below of a motor according to one embodiment of the present invention, showing the stator core being held in the stator holder. [Figure 9] This is a cross-sectional perspective view showing a state in which a stator core is attached to a stator holder of a motor according to one embodiment of the present invention. [Figure 10] This is a perspective cross-sectional view showing the configuration of a stator holder according to another embodiment of the present invention. [Modes for carrying out the invention]

[0008] <Embodiments of the present invention> Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a perspective view showing the overall configuration of an outer rotor type motor according to one embodiment of the present invention. Figure 2 is a perspective cross-sectional view showing the configuration of a motor according to one embodiment of the present invention. Figure 3 is a perspective cross-sectional view showing the configuration of a motor according to one embodiment of the present invention with the rotor, bearings, and rotor housing removed. Figure 4 is a perspective view showing the configuration of the stator holder of a motor according to one embodiment of the present invention when viewed from above. Figure 5 is a perspective view showing the configuration of the stator core of a motor according to one embodiment of the present invention. Figure 6 is a perspective cross-sectional view showing the configuration of the stator holder according to one embodiment of the present invention. Figure 7 is a perspective cross-sectional view from above showing the state in which the stator core is held in the stator holder of a motor according to one embodiment of the present invention. Figure 8 is a perspective cross-sectional view from below showing the state in which the stator core is held in the stator holder of a motor according to one embodiment of the present invention. Figure 9 is a cross-sectional perspective view showing the state in which the stator core is attached to the stator holder of a motor according to one embodiment of the present invention.

[0009] In this embodiment, for convenience, the direction in which the axis X extends when the motor 1 rotates will be referred to as the axial direction or rotational direction. Also, for convenience, in the axial direction, arrow a will be referred to as the upper side or upward, and arrow b will be referred to as the lower side or downward. In the radial direction perpendicular to axis X, arrow c, which moves away from axis X, will be referred to as the outer circumference or outside, and arrow d, which moves towards axis X, will be referred to as the inner circumference or inside. In the circumferential direction of the motor 1, arrow e will be referred to as the clockwise direction, and arrow f will be referred to as the counterclockwise direction. In the following description, the upper side (arrow a direction) and lower side (arrow b direction) refer to the vertical relationship of the motor 1 on the drawing, and do not necessarily coincide with the vertical relationship in the direction of gravity.

[0010] As shown in Figures 1 to 9, motor 1 is an outer rotor type brushless motor mounted on a floating mobile body such as a drone (not shown). In drones, the various components are attached to each other by fasteners or adhesives during assembly, but it is known that impacts to the aircraft during landing or falling can lead to damage to motor 1. For this reason, motor 1 in this embodiment simplifies assembly and significantly improves the stability of the support force that supports each component compared to conventional designs.

[0011] As shown in Figures 1 to 3, the motor 1 has a rotor housing 17 on the upper side (direction of arrow a) to which the drone's propeller (not shown) is attached, and the drone's body is attached to a stator holder 11 (Figure 2) on the lower side (direction of arrow b). As shown in Figure 2, the motor 1 mainly consists of a stator holder 11 (Figure 2), a stator 13 (Figure 3), a rotor 15 (Figure 2), a rotor housing 17 (Figures 1 and 2), and a bearing 19 (Figure 2).

[0012] The stator holder 11 is made of a metal such as an aluminum alloy and is a component that holds the bearing 19 and the stator 13 (Figure 3). The stator holder 11 has a cylindrical portion (hereinafter referred to as the "inner circumferential cylindrical portion") 111 provided on the inner circumference side (direction of arrow d) in the radial direction.

[0013] The inner cylindrical portion 111 of the stator holder 11 is formed in an overall cylindrical or substantially cylindrical shape that extends in the direction of the rotation axis. This inner cylindrical portion 111 holds two bearings 19 (19a, 19b) on its inner surface (direction of arrow d) 111n (hereinafter referred to as the "inner surface").

[0014] The two bearings 19 (19a, 19b) are integrally fixed with adhesive or the like by being fitted against the inner surface 111n of the inner cylindrical portion 111. However, the means of fixing are not limited to this, and the outer rings of the bearings 19 may also be pressed into the inner surface 111n of the inner cylindrical portion 111 of the stator holder 11 to fix them.

[0015] That is, the inner peripheral cylindrical portion 111 of the stator holder 11 also functions as a bearing holder for the two bearings 19. The bearing 19 is, for example, a ball bearing. However, the bearing 19 is not limited to this, and other various bearings such as a sleeve bearing may be used.

[0016] A plate 12 having a thin plate-like disc shape is fixed to the end of the inner peripheral cylindrical portion 111 of the stator holder 11 on the side opposite to the rotor housing 17 (lower side (in the direction of arrow b)).

[0017] The plate 12 is integrally fixed by an adhesive or the like in a state where the outer peripheral surface (hereinafter referred to as the "outer peripheral surface") 12g in the radial direction (in the direction of arrow c) is fitted to the inner peripheral surface 111n of the inner peripheral cylindrical portion 111. Further, the plate 12 has a stepped portion 12a at the outer peripheral end in the radial direction, and the bearing 19b is supported from the lower side (in the direction of arrow d) against the stepped portion 12a...

[0018] As shown in FIGS. 2 to 4, the stator holder 11 has a disc-shaped connecting portion 113 that extends from the lower end (in the direction of arrow b) of the inner peripheral cylindrical portion 111 toward the outer peripheral side in the radial direction (in the direction of arrow c).

[0019] The connecting portion 113 is formed integrally with the inner peripheral cylindrical portion 111 and connects the inner peripheral cylindrical portion 111 and a slant surface portion 115 described later. The connecting portion 113 is a thin plate-like annular portion centered on the axis X and is connected to the inner peripheral end (in the direction of arrow d) of the slant surface portion 115.

[0020] The stator holder 11 has a slant surface portion 115 that extends obliquely upward (in the direction of arrow a) from the outer peripheral end in the radial direction of the connecting portion 113 toward the stator 13. The slant surface portion 115 is formed integrally with the outer peripheral end (in the direction of arrow c) of the connecting portion 113. The slant surface portion 115 extends from the outer peripheral end along the rotational axis direction toward the rotor housing 17 and is formed integrally with an arm portion 120 having a substantially inverted U-shaped cross section.

[0021] The arm portion 120 of the stator holder 11 has a plurality of inner circumferential cylindrical pieces (hereinafter referred to as "inner circumferential cylindrical pieces") 117 that extend toward the rotor housing 17 along the axis of rotation. Each of the plurality of inner circumferential cylindrical pieces 117 is integrally formed with the outer circumferential end of the inclined surface portion 115 and is concentric with the inner circumferential cylindrical portion 111 of the stator holder 11.

[0022] Here, the number of inner cylindrical pieces 117 is the same as the number of teeth 133 of the stator core 131, which will be described later. That is, the number of inner cylindrical pieces 117 in the arm portion 120 matches the number of spaces between the teeth 133. However, it is not limited to this, and the number may be reduced to fewer than the number of spaces between the teeth 133. However, from the viewpoint of firmly holding the stator core 131, it is preferable that the number of inner cylindrical pieces 117 matches the number of spaces between the teeth 133.

[0023] In this state, when multiple inner circumferential cylindrical pieces 177 are gathered in the circumferential direction, the multiple inner circumferential cylindrical pieces 177 form a cylindrical shape as a whole.

[0024] The arm portion 120 has a connecting piece 118 that extends from the upper end (direction of arrow a) of the inner circumferential cylindrical piece 117 toward the outer circumferential side (direction of arrow c) and is integrally connected to a plurality of outer circumferential cylindrical pieces (hereinafter referred to as "outer circumferential cylindrical pieces") 119.

[0025] The connecting piece 118 has a radial width that allows it to cover the annular portion 132 of the stator core 131, which will be described later, from above (in the direction of arrow a). The lower surface (in the direction of arrow b) of the connecting piece 118 (hereinafter referred to as the "lower surface") 118b (Figure 4) is either a flat surface or a curved surface that curves concavely toward the upper side (in the direction of arrow a).

[0026] The lower surface 118b of the connecting piece 118 is in contact with the upper surface (hereinafter referred to as the "upper surface") 132a of the annular portion 132 of the stator core 131. The upper surface (in the direction of arrow a) of the connecting piece 118 (hereinafter referred to as the "upper surface") 118a is a flat or curved surface and has a certain space between it and the rotor housing 17.

[0027] The arm portion 120 has a plurality of outer circumferential cylindrical pieces 119 that extend downward (in the direction of arrow b) along the rotation axis from the outer circumferential end of the connecting piece 118. The plurality of outer circumferential cylindrical pieces 119 are positioned further outward (in the direction of arrow c) than the plurality of inner circumferential cylindrical pieces 117 in the arm portion 120 and are concentric with the inner circumferential cylindrical pieces 117.

[0028] The inner cylindrical piece 117, connecting piece 118, and outer cylindrical piece 119 of the arm portion 120 all have the same thickness. However, this is not limited to this, and the connecting piece 118 and outer cylindrical piece 119 may be formed to be thinner than the inner cylindrical piece 117, and the thickness of each can be set arbitrarily.

[0029] The arm portion 120 is formed in an inverted U-shape in cross-section so as to contact the inner circumferential surface 132n (Figure 5) and the outer circumferential surface 132g (Figure 5) of the annular portion 132 of the stator core 131. In this case, the outer circumferential surfaces 117g of the multiple inner cylindrical pieces 117 of the arm portion 120 are in contact with the inner circumferential surface 132n of the annular portion 132, and the inner circumferential surfaces 119n of the multiple outer cylindrical pieces 119 are in contact with the outer circumferential surface 132g of the annular portion 132.

[0030] In the arm portion 120, a plurality of inner cylindrical pieces 117, a plurality of connecting pieces 118, and a plurality of outer cylindrical pieces 119 are formed to hold the annular portion 132 of the stator core 131 from above (in the direction of arrow a).

[0031] In practice, the arm portion 120 is formed when the connecting piece 118 engages with the annular portion 132 while the multiple outer cylindrical pieces 119 are not bent, and then the outer cylindrical pieces 119 are bent (crimped) toward the outer surface 132g of the annular portion 132.

[0032] The outer circumferential surfaces 117g of the multiple inner cylindrical pieces 117 are formed as flat surfaces to facilitate close contact with the inner circumferential surface 132n of the annular portion 132 of the stator core 131. Similarly, the inner circumferential surfaces 119n of the multiple outer cylindrical pieces 119 are formed as flat surfaces to facilitate close contact with the outer circumferential surface 132g of the annular portion 132 of the stator core 131. However, the outer circumferential surfaces 117g of the inner cylindrical pieces 117 and the inner circumferential surfaces 119n of the outer cylindrical pieces 119 may be any shape that allows for surface contact with the inner circumferential surface 132n and outer circumferential surface 132g of the annular portion 132 of the stator core 131.

[0033] The multiple outer cylindrical pieces 119 on the arm portion 120 are formed to be longer than the length of the annular portion 132 of the stator core 131 along the rotation axis. That is, the outer cylindrical pieces 119 have a protruding portion 119c at the lower end (in the direction of arrow b) that protrudes lower (in the direction of arrow b) than the lower end (in the direction of arrow b) of the annular portion 132 of the stator core 131.

[0034] Thus, the stator holder 11 is composed of the inner cylindrical portion 111, the connecting portion 113, the inclined portion 115, and the arm portion 120.

[0035] The stator 13 is fixed to the arm portion 120 of the stator holder 11. As shown in Figure 3, the stator 13 has a stator core 131 and a coil 139.

[0036] As shown in Figure 5, the stator core 131 is a laminate of silicon steel sheets or the like as a magnetic material. The stator core 131 comprises an annular portion 132, a plurality of teeth portions 133 extending from the annular portion 132 toward the outer circumference (the direction of arrow d), and tip portions 134 connected to each of the teeth portions 133. The teeth portions 133 and tip portions 134 together are referred to as the magnetic pole portion.

[0037] The annular portion 132 of the stator core 131 is a cylindrical portion having an inner circumferential surface 132n and an outer circumferential surface 13g, and also having an upper surface 132a as one surface and a lower surface 132b as the other surface.

[0038] The inner circumferential surface 132n and outer circumferential surface 132g of the annular portion 132 are smooth curved surfaces corresponding to the outer circumferential surface 117g of the inner cylindrical piece 117 and the inner circumferential surface 119n of the outer cylindrical piece 119 in the arm portion 120 of the stator holder 11. The upper surface 132a and lower surface 132b of the annular portion 132 are flat surfaces.

[0039] The inner circumferential surface 132n of the annular portion 132 of the stator core 131 is in contact with the outer circumferential surfaces 117g of the multiple inner cylindrical pieces 117 on the arm portion 120 of the stator holder 11. The outer circumferential surface 132g of the annular portion 132 of the stator core 131 is in contact with the inner circumferential surfaces 119g of the multiple outer cylindrical pieces 119 on the arm portion 120 of the stator housing 11.

[0040] The teeth portion 133 is the part that connects the annular portion 132 and the tip portion 134, extending from the annular portion 132 toward the outer circumference (direction of arrow c) to the tip portion 134.

[0041] The tip portion 134 has convex portions that protrude in the clockwise direction (direction of arrow e) and the counterclockwise direction (direction of arrow f) in the circumferential direction, and the gap between adjacent convex portions is narrower than the gap (slot) between adjacent teeth portions 133.

[0042] As shown in Figures 2 and 3, an insulator 18 made of an insulating material is attached to the teeth portion 133 of the stator core 131, and a coil 139 is wound around the insulator 18.

[0043] The insulator 18 is composed of an upper insulator portion 18a that covers the annular portion 132, the teeth portion 133, and the tip portion 134 from above (direction of arrow a), and a lower insulator portion 18b that covers the annular portion 132, the teeth portion 133, and the tip portion 134 from below (direction of arrow b), which engage with each other.

[0044] In other words, the stator core 131 and the coil 139 are electrically insulated from each other via the insulator 18. Note that the insulator 18 does not need to be divided into an upper insulator portion 18a and a lower insulator portion 18b as described above; it may be formed as a single unit. Furthermore, instead of using the insulator 18, an insulating resin film may be formed on the surface of the stator core 131, and this resin film may be used as the insulator.

[0045] The rotor 15 (Figure 2) has a yoke 151 and a magnet 153. The yoke 151 is an annular and cylindrical iron core that extends along the axis X. The yoke 151 surrounds the magnet 153 and holds it integrally. The magnet 153 has a cylindrical shape that extends along the axis X, similar to the yoke 151.

[0046] Specifically, the magnet 153 is fixed to the inner circumferential surface 151n of the yoke 151 using adhesive. However, this is not the only option; for example, the magnet 153 may be held in contact with the inner circumferential surface 151n of the yoke 151 by press-fitting or the like.

[0047] The yoke 151 is made of a magnetic material such as iron. The yoke 151 is formed to be higher than the magnet 153 in the direction of rotation axis.

[0048] The magnet 153 is a single molded magnetic material. The inner circumferential surface of the magnet 153, facing the tip 134 of the stator core 131, is divided into a region magnetized to the south pole and a region magnetized to the north pole, which are arranged alternately along the circumferential direction. The height of the magnet 153 in the direction of rotation axis is formed to be lower than the height of the yoke 151 in the direction of rotation axis.

[0049] In other words, the magnet 153 only needs to be held in a state where its outer circumferential surface 153g is covered by the yoke 151 from the outer circumferential side (direction of arrow c). The outer circumferential portion 173 (described later) of the rotor housing 17 is held by the inner circumferential surface 151n of the yoke 151 and the upper end face 153a of the magnet 153 (direction of arrow c).

[0050] The rotor housing 17 is made of a relatively light metal such as an aluminum alloy and has an overall disc shape. However, it is not limited to this, and the rotor housing 17 may be made of other materials such as resin or plastic.

[0051] As shown in Figures 1 and 2, the rotor housing 17 has an inner circumferential portion 171 provided on the inner circumference side (direction of arrow c), an outer circumferential portion 173 provided at the end on the outer circumference side (direction of arrow d), and a spoke portion 175.

[0052] As shown in Figure 2, the inner circumference 171 of the rotor housing 17 has a cylindrical protrusion 171d with a through hole 171h centered on axis X, and a flange portion 171f extending radially from the outer circumference end of the protrusion 171d. The flange portion 171f has an outer diameter that can cover the inner cylindrical portion 111 of the stator holder 11 from above (direction of arrow a).

[0053] The protrusion 171d of the inner circumference 171 of the rotor housing 17 has a cylindrical rotating shaft 172 that extends vertically (in the direction of arrow ab) with respect to the axis X. The inner ring of the bearing 19 (19a, 19b) is held on the outer circumference 172g of the rotating shaft 172. In other words, the rotating shaft 172 of the rotor housing 17 rotates together with the rotor 15 in the motor 1. Note that the rotating shaft 172 may also be cylindrical in shape without space on the inner circumference side.

[0054] Multiple (for example, six) spoke sections 175 are connected to the outer circumference end (in the direction of arrow c) of the flange section 171f, and an annular outer circumference section 173 is connected to the outer circumference tip of each spoke section 175. In other words, the spoke section 175 connects the flange section 171f of the inner circumference section 171 to the outer circumference section 173.

[0055] The outer circumference 173 is the part that covers the magnet 153, which is fixed to the inner circumferential surface 151n of the yoke 151, from above (in the direction of arrow a) by its outer circumference end in the radial direction (direction of arrow c). The outer circumference 173 of the rotor housing 17 is integrally attached by press-fitting it onto the inner circumferential surface 151n of the yoke 151, and the circumferential surface 173m of the outer circumference 173 and the inner circumferential surface 151n of the yoke 151 are in close contact.

[0056] In the above configuration, as shown in Figure 6, when the outer cylindrical piece 119 of the arm portion 120 of the stator holder 11 is not bent (shown by the dashed line), the upper surface surface 132a of the annular portion 132 of the stator core 131 engages with the multiple connecting pieces 118 of the arm portion 120.

[0057] In this case, the outer circumferential surfaces 117g of the multiple inner cylindrical pieces 117 in the arm portion 120 are in contact with the inner circumferential surface 132n of the annular portion 132 of the stator core 131, and the multiple connecting pieces 118 in the arm portion 120 are in contact with the upper surface 132a of the annular portion 132.

[0058] Subsequently, when the multiple outer cylindrical pieces 119 on the arm portion 120 are bent and crimped so that they move closer to the outer surface 132g of the annular portion 132 of the stator core 131, the inner surface 119n of the outer cylindrical pieces 119 and the outer surface 132g of the annular portion 132 come into contact.

[0059] As a result, the stator holder 11 can firmly hold the multiple inner cylindrical pieces 117, connecting pieces 118, and outer cylindrical pieces 119 of the arm portion 120, and the annular portion 132 of the stator core 131 in surface contact from three directions.

[0060] At this time, since each of the multiple outer cylindrical pieces 119 on the arm portion 120 has a protrusion 119c, the inner circumferential surface 119n (Figure 6) of the outer cylindrical piece 119 contacts the entire outer surface 132g of the annular portion 132 of the stator core 131, completely covering it from the outer side (direction of arrow c). Thus, the degree of contact between the arm portion 120 and the annular portion 132 of the stator core 131 is increased, and the stator holder 11 can firmly hold the stator core 131 without using adhesive.

[0061] With the above configuration, the motor 1 can firmly hold the annular portion 132 of the stator core 131 by the arm portion 120 of the stator holder 11, so that the stator holder 11 and the stator core 131 can be integrated without using adhesives or fixing members. Thus, the motor 1 can further improve the stability of the support force when the stator 13 is supported by the stator holder 11 compared to conventional designs.

[0062] <Other Embodiments> Although the motor 1 in this embodiment is configured as an outer rotor type brushless motor, the present invention is applicable to motors other than brushless motors. Furthermore, the present invention is also applicable to inner rotor type motors.

[0063] Although preferred embodiments of the motor of the present invention have been described above, the motor of the present invention is not limited to the configuration of the above embodiments. Figure 10 is a perspective cross-sectional view showing the mounting state of a stator holder and a stator core according to another embodiment of the present invention.

[0064] For example, in this embodiment, the case described was that the protruding portions 119c of the multiple outer cylindrical pieces 119 on the arm portion 120 protrude downward (in the direction of arrow b) from the annular portion 132 of the stator core 131. However, the present invention is not limited to this, and the protruding portions 119c may be further bent toward the lower surface 132b of the annular portion 132 so that the protruding portions 119c and the lower surface 132b of the annular portion 132 come into contact. In this case, the arm portion 120 of the stator holder 11 can firmly hold the annular portion 132 of the stator core 131 by wrapping around it from four directions, so that the stator core 131 does not fall out even if the stator holder 11 is subjected to an impact from the outside.

[0065] Furthermore, although this embodiment describes the case in which a rotor housing 17 having spokes 175 is used, the present invention is not limited to this, and a disc-shaped rotor housing without spokes may also be used.

[0066] Furthermore, those skilled in the art can modify the motor of the present invention as appropriate in accordance with conventionally known knowledge. Such modifications, insofar as they still possess the configuration of the present invention, are of course included within the scope of the present invention. [Explanation of Symbols]

[0067] 1...Motor, 11...Stator holder, 13...Stator, 15...Rotor, 17...Rotor housing, 19 (19a, 19b)...Bearing, 111...Inner cylindrical part, 113...Connecting part, 115...Inclined surface, 117...Inner cylindrical piece, 118...Connecting piece, 119...Outer cylindrical piece, 120...Arm part, 131...Stator core, 132...Ring part, 133...Teeth, 134...Tip part, 139...Coil, 151...Yoke, 153...Magnet, 171...Inner part, 171d...Convex part, 171f...Flange part, 171h...Through hole, 173...Outer part, 175...Spoke part.

Claims

1. Rotor and, bearings and A stator facing the rotor, The system comprises a holder that holds the bearing and the stator, The stator comprises a magnetic material, an insulator, and a coil wound around the magnetic material via the insulator. The magnetic material of the stator has an annular portion and a plurality of magnetic pole portions that protrude outward from the annular portion. The holder contacts the outer circumference of the annular portion in the radial direction and the inner circumference of the annular portion in the radial direction. The holder comprises a bearing holder for holding the bearing, an arm portion, and a connecting portion for connecting the bearing holder and the arm portion. The arm portion comprises an inner cylindrical piece and an outer cylindrical piece. The cylindrical piece on the outer circumference is positioned between the plurality of magnetic pole portions in the circumferential direction. Motor.

2. The holder contacts one of the surfaces of the annular portion in the axial direction. The motor according to claim 1.

3. The holder has a protrusion that protrudes more than the other surface in the axial direction of the annular portion. The motor according to claim 1 or 2.

4. The holder contacts the other surface of the annular portion in the axial direction. The motor according to claim 2.

5. The holder is formed of a magnetic material. The motor according to any one of claims 1 to 4.

6. The motor according to any one of claims 1 to 5, wherein the arm portion is in contact with the outer peripheral surface on the outer peripheral side in the radial direction of the annular portion and the inner peripheral surface on the inner peripheral side in the radial direction of the annular portion.

7. The outer circumferential surface of the inner cylindrical piece on the inner side contacts the inner circumferential surface of the annular portion in the radial direction. The inner surface of the cylindrical piece on the outer circumference contacts the outer surface of the annular portion in the radial direction. The motor according to claim 6.

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