Motor

Abstract

To provide a thin and light motor that can be assembled with high accuracy.SOLUTION: A motor (1) according to the present invention includes a rotor (15) including a magnet (153), an annular yoke (151) having an inner surface (151n) surrounding the magnet (153), and a holder (17) that holds the yoke (151), and the yoke (151) has an end (152) on the holder side in the direction of a rotation axis (X) of the rotor (15), and the outer surface (173mg) of the holder (17) and the inner surface (151n) of the yoke (151) are fitted, and the end (152) of the holder side of the yoke (151) and the outer surface (173mu) of the holder (17) are engaged.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a motor.

Background Art

[0002] Conventionally, a disk drive motor has been proposed that prevents thermal deformation of a disk mounting surface while fixing a yoke to a rotor hub with good balance (see, for example, Patent Document 1).

[0003] In the disk drive motor of Patent Document 1, a field magnet is held inside a yoke body and an inner flange of a yoke having an L-shaped cross section, and a ridge of a rotor hub is fitted to an end face on the inner peripheral side of the inner flange, whereby the rotor hub and the yoke are integrally attached.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the disk drive motor of Patent Document 1, the ridge of the rotor hub is only fitted to the end face on the inner peripheral side of the inner flange, and it cannot be said that it can be attached with high precision, and there has also been a demand for further thinning and weight reduction.

[0006] The present invention has been made in view of the above background, and an example of the problem is to provide a motor that is thinned and lightened.

Means for Solving the Problems

[0007] The above problems are solved by the following present invention. That is, the motor of the present invention includes a rotor having a magnet, an annular yoke having an inner surface surrounding the magnet, and a holder for holding the yoke. The yoke has an end on the holder side in the rotational axis direction of the rotor, the outer surface of the holder and the inner surface of the yoke are fitted, and the end of the yoke on the holder side and the outer surface of the holder are engaged.

[0008] It is preferable that an outer peripheral end of the holder has a protruding portion extending in the radial direction, and the yoke has a surface facing an end surface of the protruding portion in the rotational axis direction of the rotor.

[0009] It is preferable that the outer surface of the holder has a concave stepped portion, and an end of the yoke is engaged with the stepped portion of the holder.

[0010] A part of the end of the yoke on the holder side that engages with the outer surface of the holder is deformed toward the holder, and it is preferable that a predetermined gap is formed between a part of the end of the yoke on the holder side and an end of the magnet on the holder side in the rotational axis direction of the rotor.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0012] Outline of the Embodiment First, an outline of a typical embodiment of the invention disclosed in the present application will be described. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are described with parentheses.

[0013] 〔1〕A motor (1) according to a typical embodiment of the present invention includes a rotor (15) having a magnet (153), an annular yoke (151) having an inner surface (151n) surrounding the magnet (153), and a holder (17) for holding the yoke (151). The yoke (151) has an end portion (152) on the holder side in the direction of the rotation axis (X) of the rotor (15). The outer surface (173mg) of the holder (17) and the inner surface (151n) of the yoke (151) are fitted, and the end portion (152) of the yoke (151) on the holder side and the outer surface (173mu) of the holder (17) are engaged.

[0014] 〔2〕The outer peripheral end portion (173) of the holder has a radially extending protrusion (177), and the yoke (151) has a surface (151kb) facing the end surface (177b) of the protrusion (177) in the direction of the rotation axis (X) of the rotor (15).

[0015] 〔3〕The outer surfaces (173mu, 173mg) of the holder (17) have concave stepped portions (174), and the end portion (152) of the yoke (151) is engaged with the stepped portion (174) of the holder (17).

[0016] 〔4〕A part (152s) of the end portion (152) of the yoke (151) on the holder (17) side that engages with the outer surface (173mu) of the holder (17) is deformed toward the holder (17), and a predetermined gap is formed between a part (152s) of the end portion (152) of the yoke (151) on the holder side and the end portion of the magnet (153) on the holder (17) side in the direction of the rotation axis (X) of the rotor (15).

[0017] Subsequently, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the overall configuration of an outer rotor type motor according to an embodiment of the present invention. FIG. 2 is a cross-sectional perspective view of the motor according to an embodiment of the present invention. FIG. 3 is a perspective view showing the overall configuration of a stator core according to an embodiment of the present invention. FIG. 4 is a perspective view showing a state before the holder of the motor according to an embodiment of the present invention is attached. FIG. 5 is a partial perspective view showing a state where the holder of the motor according to an embodiment of the present invention is attached to the yoke. FIG. 6 is a perspective view showing a state before the holder of the motor according to an embodiment of the present invention is attached to the yoke. FIG. 7 is a perspective view showing the overall configuration of the yoke of the motor according to an embodiment of the present invention. FIG. 8 is a partial perspective view showing the configuration of the outer peripheral end portion of the holder of the motor according to an embodiment of the present invention. FIG. 9 is a partial cross-sectional perspective view showing a state where the holder and the yoke of the motor according to an embodiment of the present invention are integrally attached.

[0018] In the description of the present embodiment, for convenience, in the following description, the direction in which the axis X extends when the motor 1 rotates is referred to as the rotation axis X direction or the axis X direction. Also, for convenience, in the following description, in the rotation axis X direction, the arrow a direction is the upper side and the arrow b direction is the lower side. In the radial direction perpendicular to the axis X, the arrow c direction away from the axis X is the outer peripheral side, and the arrow d direction approaching the axis X is the inner peripheral side. In the circumferential direction of the motor 1, the arrow e direction is the clockwise direction, and the arrow f direction is the counterclockwise direction. In the following description, the upper side (arrow a direction) and the lower side (arrow b direction) mean the vertical relationship of the motor 1 on the drawing, and do not necessarily coincide with the vertical relationship in the gravitational direction.

[0019] As shown in FIGS. 1 to 10, the motor 1 is an outer rotor type brushless motor mounted on a floating moving body such as a drone (not shown). In a drone, it is known that the impact on the airframe during landing or falling can damage the motor 1 for driving the blades. Therefore, the motor 1 in the present embodiment is devised to be lightweight in order to reduce the impact during landing or falling of the drone.

[0020] A propeller (not shown) of the drone is attached to the upper holder 17 (FIG. 1) (arrow a direction) of the motor 1, and the airframe of the drone is attached to the lower stator housing 11 (FIG. 2) (arrow b direction). As shown in FIG. 2, the motor 1 mainly includes a stator housing 11, a stator 13, a rotor 15, a holder 17, and a bearing 19.

[0021] The stator housing 11 has a cylindrical inner peripheral portion 111, a cylindrical outer peripheral portion 112, and a connecting portion 115. The inner peripheral portion 111 of the stator housing 11 is formed in a cylindrical shape or a substantially cylindrical shape extending in the rotation axis X direction. The two bearings 19 are held on the inner peripheral side (arrow d direction) surface (hereinafter referred to as the "inner peripheral surface").

[0022] Specifically, the inner peripheral portion 111 holds the bearings 19 on the upper side (in the direction of arrow a) and the lower side (in the direction of arrow b) in the rotation axis X direction, respectively. In this case, the outer ring 19a of the bearing 19 is fixed to the inner peripheral surface of the inner peripheral portion 111 of the stator housing 11 using an adhesive. Note that the fixing means is not limited to this, and the outer ring 19a of the bearing 19 may be press-fitted and fixed to the inner peripheral surface of the inner peripheral portion 111 of the stator housing 11.

[0023] That is, the inner peripheral portion 111 of the stator housing 11 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 various other bearings such as a sleeve bearing may be used.

[0024] The outer peripheral portion 112 of the stator housing 11 is formed in a cylindrical shape or a substantially cylindrical shape extending in the rotation axis X direction, similar to the inner peripheral portion 111. Both the inner peripheral portion 111 and the outer peripheral portion 112 have the axis X as the central axis. The length of the outer peripheral portion 112 in the rotation axis X direction may be shorter than the length of the inner peripheral portion 111 in the rotation axis X direction.

[0025] A connecting portion 115 is integrally formed with the inner peripheral portion 111 and the outer peripheral portion 112 between the inner peripheral portion 111 and the outer peripheral portion 112 of the stator housing 11. The connecting portion 115 connects the inner peripheral portion 111 and the outer peripheral portion 112 to each other. The connecting portion 115 extends from the outer peripheral side end portion of the inner peripheral portion 111 toward the outer peripheral side (in the direction of arrow c) and is connected to the inner peripheral side end portion of the outer peripheral portion 112.

[0026] The stator core 131 of the stator 13 is fixed to the outer peripheral side surface (hereinafter referred to as the "outer peripheral surface") of the outer peripheral portion 112. As shown in FIG. 9, the stator 13 has a stator core 131, an insulator 135, and a coil 139.

[0027] The stator core 131 (Figs. 3 and 4) is a laminate such as a silicon steel sheet as a magnetic material, and includes an annular portion 132, a plurality of connecting portions 133 extending from the annular portion 132 toward the outer peripheral side (the side in the direction of arrow d), and magnetic pole portions 134 connected to the respective connecting portions 133. That is, between the annular portion 132 and the magnetic pole portions 134, there are connecting portions 133 that form a part of the stator core extending in the radial direction. These annular portion 132, magnetic pole portions 134, and connecting portions 133 function as a yoke.

[0028] The inner peripheral surface of the annular portion 132 of the stator core 131 is fixed to the outer peripheral surface of the outer peripheral portion 112 of the stator housing 11. Further, the magnetic pole portions 134 of the stator core 131 project in the clockwise direction (the direction of arrow e) and the counterclockwise direction (the direction of arrow f) in the circumferential direction, and the gap between adjacent magnetic pole portions 134 is narrower than the gap (slot) between adjacent connecting portions 133.

[0029] An insulator 135 (Fig. 9) formed of an insulating member is attached to the connecting portion 133 of the stator core 131. A coil 139 is wound around the connecting portion 133 via the insulator 135. The connecting portion 133 of the stator core 131 and the coil 139 are electrically insulated from each other via the insulator 135. Note that a resin film having insulating properties may be formed on the surface of the stator core 131 and used as an insulator.

[0030] The rotor 15 (Fig. 2) has a yoke 151 and magnets 153. The yoke 151 is an iron core having an annular and cylindrical shape extending in the rotation axis X direction. The yoke 151 integrally holds the magnets 153 in a state of surrounding the magnets 153. The yoke 151 prevents leakage of the magnetic field of the magnets 153 and is formed of a magnetic material such as iron.

[0031] A plurality (in this case, for example, six) of recesses 151K (Fig. 7) are formed at regular intervals in the circumferential direction at the upper end (the direction of arrow a) of the yoke 151 in the rotation axis X direction.

[0032] The plurality of recesses 151K have a shape that is recessed in a rectangular or U-shaped form from the end face (hereinafter referred to as the "upper end face") 151t on the holder 17 side (in the direction of arrow a) of the yoke 151.

[0033] The recess 151K is composed of a bottom surface 151kb that forms the recess 151K and two side surfaces 151Ks that face each other in the circumferential direction. Further, the yoke 151 has two end portions (also referred to as protruding portions) 152 that extend in the longitudinal direction, which is the direction from the bottom surface 151kb of the recess 151K toward the upper-side (in the direction of arrow a) holder 17. That is, the yoke 151 has two end portions 152 provided on the holder 17 side of the yoke 151 in the recess 151K. Note that the number of end portions 152 is not limited to two, and a plurality of end portions 152 may be formed in the recess 151K.

[0034] The two end portions 152 formed in the recess 151K are formed at positions separated from each other by a predetermined distance on the bottom surface 151kb of the recess 151K. The length (height) of the two end portions 152 in the direction of the rotation axis X is substantially the same as the distance H from the bottom surface 151kb of the recess 151K to the upper end face 151t of the yoke 151, that is, the height (depth) of the recess 151K.

[0035] Note that the length (height) L of the end portion 152 may be the same as, larger than, or smaller than the height (depth) of the recess 151K. The circumferential width d1 (FIG. 5) of the two end portions 152 can be arbitrarily set from the viewpoint of strength. The thickness of the two end portions 152 in the radial direction is the same as the thickness of the yoke 151 in the radial direction.

[0036] The end portion 152 includes a main body portion 152p that extends upward (in the direction of arrow a) from the bottom surface 151kb of the recess 151K, and a tip portion 152s in which a part of the main body portion 152p on the holder 17 side, that is, the upper side (in the direction of arrow a), is bent and deformed toward the inner circumferential side of the yoke 151.

[0037] The tip portion 152s of the end portion 152 is bent so that the narrow-side angle α between the tip portion 152s and the body portion 152p is an acute angle (for example, 50 degrees to 70 degrees), and it has a bent portion. Thereby, the end portion 152 can be engaged with the outer surface 173m (FIGS. 6 and 8) of the outer peripheral end portion 173 of the holder 17 described later.

[0038] Here, when the holder 17 is attached to the yoke 151, the tip portion 152s of the end portion 152 is separated from the upper end (in the direction of arrow a) of the magnet 153 held on the inner surface 151n of the yoke 151 by a predetermined distance. That is, the height of the body portion 152p is set so that the tip portion 152s of the end portion 152 and the magnet 153 of the yoke 151 are separated by a predetermined distance.

[0039] In this way, by separating the end portion 152 and the upper end (in the direction of arrow a) of the magnet 153 by a predetermined distance, when the tip portion 152s is bent, the residual stress remaining in the end portion 152 can be prevented from affecting the magnetic characteristics of the yoke 151 and thus affecting the performance of the magnetic circuit composed of the coil 39, the magnet 153, and the yoke 151 (stator core 131). Thereby, the motor 1 can prevent the performance degradation of the motor itself due to the influence of the magnetic characteristics at the end portion 152 of the yoke 151.

[0040] On the inner surface 151n of the yoke 151 (hereinafter, this is referred to as the "inner surface"), the magnet 153 (FIG. 7) is fixed using an adhesive, and the magnet 153 is held on the yoke 151. The inner surface 151n of the yoke 151 is formed with high precision by cutting. However, not limited to this, the inner surface 151n of the yoke 151 may be formed with high precision by roll forming or the like. Also, for example, the magnet 153 may be held in contact with the inner surface 151n of the yoke 151 by press-fitting or the like.

[0041] The magnet 153 has a cylindrical shape extending in the direction of the rotation axis X, similar to the yoke 151. The magnet 153 is held on the inner surface 151n of the yoke 151 formed with high precision using an adhesive or the like.

[0042] The magnet 153 is an integrally molded product of a magnetic material. The inner peripheral surface of the magnet 153 facing the magnetic pole portion 134 of the stator core 131 is divided into a region magnetized to the S pole and a region magnetized to the N pole, and they are arranged alternately along the circumferential direction. The height of the magnet 153 in the direction of the rotation axis X is formed lower than the height of the yoke 151 in the direction of the rotation axis X.

[0043] Here, the upper end surface (hereinafter referred to as the "upper end face") 153t of the upper end portion of the magnet 153 in the direction of the rotation axis X is flush with the bottom surface 151kb of the recess 151K. Note that the upper end surface 153t of the magnet 153 may be at a position lower than the bottom surface 151kb of the recess 151K.

[0044] That is, the magnet 153 may be held in a state where the upper end portion (hereinafter referred to as the "upper end") and the lower end portion (hereinafter referred to as the "lower end") in the direction of the rotation axis X are covered by the yoke 151.

[0045] The holder 17 is formed of a relatively light metal such as an aluminum alloy and has a generally disc shape. However, it is not limited to this, and the holder 17 may be formed of other materials such as resin or plastic. Note that the holder 17 is also formed with high precision by cutting. However, it is not limited to this, and the holder 17 may be formed by press molding or the like.

[0046] As shown in FIGS. 1 and 2, the holder 17 has an inner peripheral portion 171 provided on the inner peripheral side (in the direction of arrow c), an outer peripheral end portion 173 provided at the end portion on the outer peripheral side (in the direction of arrow d), and spokes 175.

[0047] The inner peripheral portion 171 of the holder 17 has a columnar convex portion 171d provided with a through hole 171h centered on the axis X, and a flange portion 171f extending radially from the outer peripheral side end of the convex portion 171d. The flange portion 171f has a size capable of covering the inner peripheral portion 111 of the stator housing 11 from above (in the direction of arrow a).

[0048] The convex portion 171d of the inner peripheral portion 171 has a cylindrical inner cylinder portion 172 extending in the vertical direction (in the direction of arrows a and b) centered on the axis X. The inner ring 19b of the bearing 19 is held on the outer peripheral surface of the inner cylinder portion 172. That is, the inner cylinder portion 172 of the holder 17 functions as a rotating shaft in the motor 1. Note that the cylindrical portion 172 may have a cylindrical shape with an internal filling.

[0049] A plurality (for example, six) of spokes 175 are connected to the outer peripheral side (in the direction of arrow c) end of the flange portion 171f, and an annular outer peripheral end portion 173 is connected to the radially distal end portion of the spoke 175. That is, the spoke 175 connects the flange portion 171f of the inner peripheral portion 171 and the outer peripheral end portion 173.

[0050] The outer peripheral end portion 173 has an outer surface 173m at the outer peripheral side (in the direction of arrow c) end in the radial direction. The outer surface 173m of the outer peripheral end portion 173 includes an annular first outer side surface portion 173mu (FIG. 6) that covers the magnet 153 fixed to the inner side surface 151n of the yoke 151 from above (in the direction of arrow a), and a second outer side surface portion 173mg (FIG. 6) that extends downward (in the direction of arrow b) along the rotation axis X direction from the outer peripheral side edge of the first outer side surface portion 173mu.

[0051] In particular, among the outer surface 173m of the outer peripheral end portion 173, the second outer side surface portion 173mg is also formed with high precision by cutting and shaving as described above. Therefore, when the holder 17 is press-fitted into the yoke 151, the second outer side surface portion 173mg of the outer peripheral end portion 173 of the holder 17 and the inner side surface 151n of the yoke 151 are attached with high precision in a state of being in close contact.

[0052] The outer peripheral end portion 173 of the holder 17 has two or more stepped portions 174. In the plurality of stepped portions 174, a concave step is formed at the end of the portion of the outer surface 173m that faces the spoke 175. The plurality of stepped portions 174 are concave spaces that are recessed in a substantially rectangular parallelepiped shape so as to straddle both the first outer surface portion 173mu and the second outer surface portion 173mg on the outer surface 173m.

[0053] The two stepped portions 174 are provided at positions separated from each other by a predetermined interval. The interval between one stepped portion 174 and the other stepped portion 174 is substantially the same as the interval between the two end portions 152 in the yoke 151. That is, the two stepped portions 174 and the two end portions 152 can be arranged to face each other.

[0054] The stepped portion 174 (FIG. 8) is engaged with the tip portions 152s of the two end portions 152 of the yoke 151. The stepped portion 174 is composed of a bottom surface 174b and two side surfaces 174s facing each other, and the bottom surface 174b and the two side surfaces 174s form a concave space. The bottom surface 174b of the stepped portion 174 is a surface facing the tip portion 152s of the yoke 151 that engages with the stepped portion 174. In the example of FIG. 9, a predetermined gap S is formed between the bottom surface 174b and the tip portion 152s, and they are non-contact with each other. Note that the bottom surface 174b and the tip portion 152s may be brought into contact with each other to engage the stepped portion 174 of the holder 17 with the end portion 152 of the yoke 151, and the holder 17 and the yoke 151 may be fixed.

[0055] The two side surfaces 174s (FIG. 9) that form the concave space of the stepped portion 174 are vertical surfaces that extend toward the holder 17 with respect to the bottom surface 174b, and are surfaces facing the circumferential side surface 152sc of the tip portion 152s of the end portion 152 described above. The distance d2 (FIG. 8) between the two side surfaces 174s in the stepped portion 174 may be substantially the same as the width d1 of the end portion 152, or may be larger.

[0056] In addition, when the motor 1 rotates in the circumferential direction (the direction of arrow ef) with the holder 17 attached to the yoke 151, the side surface 174s of the stepped portion 174 in the holder 17 may contact the side surface 152sc of the tip portion 152s of the end portion 152 formed in the concave portion 151K of the yoke 151, and circumferential displacement of the holder 17 with respect to the yoke 151 may be prevented.

[0057] The outer peripheral end portion 173 has a protruding portion 177 that extends in the radially outer peripheral direction (the direction of arrow d) from the edge on the lower side (the direction of arrow b) of the second outer side surface portion 173mg between the two stepped portions 174. The protruding portion 177 has a length such that it does not protrude from the outer peripheral side surface of the yoke 151 when the holder 17 is attached to the yoke 151.

[0058] This protruding portion 177 serves as a part for receiving the impact that the yoke 151 of the motor 1 receives when the drone lands or falls. Note that a convex portion 176 (FIG. 9) for improving the strength of the protruding portion 177 is provided on the surface of the outer peripheral end portion 173 that faces the side opposite to the first outer side surface portion 173mu, that is, the surface facing the stator core 131 side. The protruding portion 177 may function as a buffer portion that can receive the impact without damaging the protruding portion 177 due to the presence of the convex portion 176.

[0059] The protruding portion 177 of the outer peripheral end portion 173 has a flat surface (hereinafter referred to as the "lower end surface") 177b on the yoke 151 side (the direction of arrow b). The lower end surface 177b of this protruding portion 177 is a surface that faces the bottom surface 151Kb forming the concave portion 151K of the yoke 151 and the end surface (hereinafter referred to as the "upper end surface") 153t on the upper side (the direction of arrow a) of the magnet 153.

[0060] Therefore, when the holder 17 is attached to the yoke 151, the lower end surface 177b of the protruding portion 177 of the outer peripheral end portion 173 contacts and is fixed to the bottom surface 151Kb forming the concave portion 151K of the yoke 151.

[0061] Since the bottom surface 177b of the protrusion 177 faces the bottom surface 151Kb of the recess 151K and the upper end surface 153t of the magnet 153 in the direction of the rotation axis, the bottom surface 151Kb may also serve as a positioning portion so that the magnet 153 is positioned below the bottom surface 151Kb of the recess 151K of the yoke 151.

[0062] When the magnet 153 is held on the inner surface 151n of the yoke 151, the upper end surface 153t of the magnet 153 may be arranged below (in the direction of arrow b) the bottom surface 151Kb of the recess 151K. That is, the bottom end surface 177b of the protrusion 177 of the outer peripheral end portion 173 contacts the bottom surface 151Kb forming the recess 151, and the magnet 153 may be positioned below (in the direction of arrow a) the bottom surface 151Kb of the recess 151K.

[0063] In the above configuration, when the holder 17 is attached to the yoke 151, the motor 1 arranges the second outer surface portion 173mg at the outer peripheral end portion 173 of the holder 17 with respect to the inner surface 151n of the yoke 151, deforms a part of the end portion 152 of the yoke 151, and engages and fixes it to the outer peripheral end portion 173 of the holder 17. Therefore, the holder 17 can be assembled to the yoke 151 with a simple configuration.

[0064] In the motor 1, when the holder 17 is inserted into the yoke 151, the step portion 174 of the outer peripheral end portion 173 of the holder 17 is arranged below (in the direction of arrow b) the upper end surface 151t of the yoke 151, and the step portion 174 of the outer peripheral end portion 173 is engaged with the end portion 152 provided in the recess 151K. As a result, the motor 1 can reduce the height in the direction of the rotation axis X compared to the conventional one, and thus can be made thinner as a whole.

[0065] For example, among the outer surfaces 173m of the outer peripheral end portion 173 of the holder 17, the second outer surface portion 173mg can be formed with high precision by milling in cutting, the inner surface 151n of the yoke 151 can be formed with high precision by milling in cutting, and the outer peripheral end portion 173 of the holder 17 can be fitted to the inner surface 151n of the yoke 151 by press-fitting. In the motor 1, the assembling accuracy between the holder 17 and the yoke 151 can be improved.

[0066] Further, when the holder 17 is inserted into the yoke 151 in the motor 1, two end portions 152 provided in the recess 151K of the yoke 151 engage with a stepped portion 174 provided in the outer peripheral end portion 173 of the holder 17. Thereby, the holder 17 and the yoke 151 can be firmly fixed.

[0067] In the motor 1, the lower end surface 177b of the protruding portion 177 of the holder 17, the bottom surface 151Kb of the recess 151K of the yoke 151, and the upper end surface 153t of the magnet 153 may face or contact each other. In this case, the protruding portion 177 of the holder 17 can be used as a positioning portion in the rotational axis X direction of the yoke 151 and the magnet 153.

[0068] The holder 17 and the yoke 151 can be formed of different members, and the weight reduction of the motor 1 can be achieved. For example, the holder 17 can be formed of a relatively light metal member, and the yoke 151 can be formed of a magnetic member heavier than the holder 17, so that the weight reduction of the motor 1 can be achieved while ensuring the magnetic characteristics of the yoke 151 constituting the magnetic circuit.

[0069] Furthermore, when the motor 1 is used for applications of floating moving bodies such as drones, due to the presence of the protruding portion 177 provided on the outer peripheral end portion 173 of the holder 17, the impact transmitted through the yoke 151 during landing or falling can be absorbed by the protruding portion 177. Thereby, compared with a holder not provided with the protruding portion 177, the impact resistance can be improved and the risk of breakage can be reduced.

[0070] Furthermore, in the motor 1, with the holder 17 and the yoke 151 integrated, the tip 152s of the end portion 152 formed in the recess 151K of the yoke 151 and the upper end (in the direction of arrow a) of the magnet 153 held on the inner surface 151n of the yoke 151 are separated by a predetermined distance in the direction of the rotation axis X.

[0071] As a result, in the motor 1, it is possible to prevent the performance of the magnetic circuit composed of the coil 39, the magnet 153, and the yoke 151 (stator core 131) from deteriorating due to the residual stress when the end portion 152 is bent affecting the magnetic characteristics of the yoke 151.

[0072] According to the above configuration, the motor 1 can be easily, firmly, or highly precisely attached by engaging the holder 17 and the yoke 151, fixing them by press-fitting, or fitting them together.

[0073] Also, the connecting portion 115 of the stator housing 11 may be used as a heat radiating member that releases the heat of the stator to the outside. By using the connecting portion 115 as a heat radiating member, the heat of the stator can be efficiently released to the outside. Also, the connecting portion 115 can be cooled by the blades attached to the motor 1 to actively perform heat radiation.

[0074] Note that the motor 1 of the present embodiment is configured as an outer rotor type brushless motor, but the present invention is also applicable to motors other than brushless motors. Also, the present invention is applicable to inner rotor type motors.

[0075] As described above, the motor of the present invention has been described with reference to preferred embodiments, but the motor of the present invention is not limited to the configuration of the above embodiments. For example, in the present embodiment, the case where the magnet 153 is formed in an annular shape has been described, but the present invention is not limited to this. As shown in FIG. 10, the magnet 153 may be formed as an assembly in which the inner peripheral surface facing the magnetic pole portion 134 of the stator core 131 is divided into a segment 153a magnetized to the S pole and a segment 153b magnetized to the N pole and arranged alternately along the circumferential direction.

[0076] Also, in this embodiment, the case where the holder 17 having the spokes 175 is used has been described. However, the present invention is not limited to this, and as shown in FIG. 11, a disk-shaped holder 17Z without spokes may be used.

[0077] In this case, the holder 17Z is not provided with the stepped portion 174 (FIGS. 6 and 8) formed of a concave space, and the end portion 152 formed in the concave portion 151K of the yoke 151 may be engaged with the stepped portion 174Z formed in a stepped shape at the outer peripheral end portion 173Z.

[0078] In addition, those skilled in the art can appropriately modify the motor of the present invention in accordance with conventionally known knowledge. As long as the configuration of the present invention is still provided by such modifications, of course, it is included in the scope of the present invention.

Explanation of Reference Numerals

[0079] 1... motor, 11... stator housing, 13... stator, 15... rotor, 17, 17Z... holder, 19(19a, 19b)... bearing, 111... inner peripheral portion, 112... outer peripheral portion, 115... connecting portion, 131... stator core, 132... annular portion, 133... connecting portion, 135... insulator, 139... coil, 151... yoke, 151t... upper end face, 151n... inner side face, 151K... concave portion, 151Kb... bottom face, 151Ks... side face, 152... end portion (protruding portion), 152p... main body portion, 152s... tip portion, 152sc... side face, 153... magnet, 153t... upper end face, 171... inner peripheral portion, 171d... convex portion, 171f... flange portion, 171h... through hole, 172... inner cylinder portion, 173... outer peripheral end portion, 173m... outer side face, 173mu... first outer side face portion, 173mg... second outer side face portion, 174... stepped portion, 174b... bottom face, 174s... side face, 175... spoke, 176... rib portion, 177... protruding portion, 177b... lower end face.

Claims

1. A rotor having a magnet, an annular yoke having an inner surface surrounding the magnet, and a holder holding the yoke, and a stator having a coil, wherein the yoke has an end portion on the holder side in the rotational axis direction of the rotor, the holder includes an outer surface and a stator-side surface, and the stator-side surface is on the opposite side of the outer surface in the rotational axis direction of the rotor, the outer surface includes a first outer surface portion and a second outer surface portion, the first outer surface portion covers the magnet in the rotational axis direction and extends in the radial direction, when viewed with a line of sight in the rotational axis direction, the inner surface of the yoke is outside the first outer surface portion in the radial direction, the second outer surface portion extends in the rotational axis direction of the rotor, the inner surface of the yoke is attached to the second outer surface portion, the end portion of the yoke on the holder side engages with the outer surface, the second outer surface portion has a protruding portion extending in the radial direction, the yoke has a surface facing the end surface of the protruding portion in the rotational axis direction of the rotor, A motor.

2. The holder includes an inner peripheral portion, an outer peripheral end portion having the outer surface, and a plurality of spokes connecting the inner peripheral portion and the outer peripheral end portion, the outer surface has a plurality of concave stepped portions, the spokes are arranged between the plurality of stepped portions in the circumferential direction, and the plurality of end portions of the yoke on the holder side engage with the plurality of stepped portions of the holder. The motor according to claim 1.

3. A part of the end portion of the yoke on the holder side that engages with the outer surface of the holder is deformed toward the holder, and a predetermined gap is formed between a part of the end portion of the yoke on the holder side and the end portion of the magnet on the holder side in the rotational axis direction of the rotor. The motor according to claim 1 or 2.

4. The motor according to any one of claims 1 to 3, wherein the holder is formed of metal.

5. A rotor having a magnet, an annular yoke having an inner surface surrounding the magnet, and a holder holding the yoke, and a stator having a coil, wherein the yoke has a plurality of end portions on the holder side in the rotational axis direction of the rotor, the holder includes an inner peripheral portion, an outer peripheral end portion having an outer surface, and a plurality of spokes connecting the inner peripheral portion and the outer peripheral end portion, and the outer surface has a plurality of concave stepped portions. The spoke is disposed between the plurality of stepped portions in the circumferential direction. A motor in which a plurality of the holder-side ends of the yoke are engaged with a plurality of stepped portions of the holder. **Claim 6** The outer surface includes a first outer surface portion and a second outer surface portion. The first outer surface portion covers the magnet in the rotation axis direction and extends in the radial direction. The yoke surrounds the first outer surface portion in the radial direction. The second outer surface portion extends in the rotation axis direction of the rotor. The second outer surface portion is attached to the inner surface of the yoke. The motor according to claim 5. **Claim 7** The second outer surface portion includes a protrusion extending in the radial direction. The yoke has a surface facing the end surface of the protrusion in the rotation axis direction of the rotor. The motor according to claim 6. **Claim 8** A part of the holder-side end of the yoke that engages with the outer surface of the holder is deformed toward the holder. A predetermined gap is formed between a part of the holder-side end of the yoke and the holder-side end of the magnet in the rotation axis direction of the rotor. The motor according to any one of claims 5 to 7. **Claim 9** The holder is made of metal. The motor according to any one of claims 5 to 8. **Claim 10** A motor and blades attached to the motor. The motor A rotor having a magnet, an annular yoke having an inner surface surrounding the magnet, and a holder holding the yoke. A stator having a coil. The yoke has a holder-side end in the rotation axis direction of the rotor. The holder includes an outer surface and a stator-side surface, and the stator-side surface is on the opposite side of the outer surface in the rotation axis direction of the rotor. The outer surface includes a first outer surface portion and a second outer surface portion. The first outer surface portion covers the magnet in the rotation axis direction and extends in the radial direction. The second outer surface portion extends in the rotation axis direction of the rotor. When looking in the rotation axis direction, the inner surface of the yoke is outside the first outer surface portion in the radial direction. The second outer surface portion is attached to the inner surface of the yoke. A floating moving body in which the holder-side end of the yoke and the outer surface are engaged. **Claim 11** The second outer surface portion has a protrusion extending in the radial direction. The yoke has a surface facing the end surface of the protruding portion in the rotational axis direction of the rotor. The floating mobile body according to claim 10.

12. The holder includes an inner peripheral portion, an outer peripheral end portion having the outer surface, and a plurality of spokes connecting the inner peripheral portion and the outer peripheral end portion. The outer surface has a plurality of concave stepped portions. The spokes are arranged between the plurality of stepped portions in the circumferential direction. A plurality of holder-side ends of the yoke are engaged with the plurality of stepped portions of the holder. The floating mobile body according to claim 10 or 11.

13. A part of the holder-side end of the yoke that engages with the outer surface of the holder is deformed toward the holder. A predetermined gap is formed between a part of the holder-side end of the yoke and the holder-side end of the magnet in the rotational axis direction of the rotor. The floating mobile body according to any one of claims 10 to 12.

14. The floating mobile body according to any one of claims 10 to 13, wherein the holder is formed of metal.

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