JP2000116039A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor in which rattling of a bearing can be absorbed through a simple structure at low cost while increasing the counter electromotive force. SOLUTION: The motor comprises a housing 2, a rotor 4 supported rotatably on the housing 2 through bearings 10, 12, a rotor magnet 40 fixed to the rotor 4 through a yoke 38, and a stator 41 disposed oppositely to the rotor magnet 40 on the radial inside. The yoke 38 has an annular yoke body 62 and a yoke flange 64 extending radially from one end of the yoke body 62 and projecting farther inward than the inner circumferential surface of the rotor magnet 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor used in a disk drive for rotating a recording disk.

[0002]

2. Description of the Related Art A motor used in a disk drive or the like includes a housing, a rotor rotatably supported on the housing via a pair of ball bearings, and a rotor magnet mounted on the rotor via a yoke. And a stator disposed to face the rotor magnet. Such motors generally include an outer rotor type motor and an inner rotor type motor. In the outer rotor type motor, a stator is disposed radially outside a rotor magnet. A stator is disposed radially inside the magnet.

In this type of motor, an axial load (referred to as "preload") is applied to the ball bearings in order to absorb backlash of the pair of ball bearings and to rotate the ball bearings stably. A method of position preload or constant pressure preload is generally adopted. For example, a disc spring or a coil spring is provided to apply a predetermined preload. Also, a method of applying a preload (referred to as "magnetic preload") by a biasing force due to the magnetic attraction force utilizing a magnetic attraction effect acting between the rotor magnet and the stator without using a spring such as a disc spring. There is also.

[0004] In the motor, it is desirable to generate a large driving torque in order to stably rotate the rotor. The generated driving torque is closely related to the back electromotive force, and the generated driving torque increases as the back electromotive force increases.

[0005]

However, due to the recent demand for smaller and thinner disk drive devices, motors have been made smaller and thinner, and a single pair of ball bearings has been used instead of a conventional pair of ball bearings. Although a structure or a support structure using one ball bearing and one sleeve bearing (oil-impregnated bearing) is adopted, a preloading structure using a spring member such as a disc spring increases the dimension in the axial direction. However, there are problems such as an increase in

[0006] Further, in response to recent demands for reduction in manufacturing costs, cost reduction of motors has been progressing. In order to reduce the cost, for example, when a ferrite-based material is used as a material for the rotor magnet, the holding force of the rotor magnet is weakened, and a sufficient back electromotive force cannot be obtained. The rotation torque of the motor becomes weak, and desired rotation characteristics cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor capable of absorbing a backlash of a bearing and stably rotating the bearing with a simple structure and at a low cost without increasing an axial dimension. It is. Another object of the present invention is to provide a motor that can increase the back electromotive force with a simple configuration and thereby improve the rotational torque.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a housing, a rotor rotatably supported by the housing via a bearing, a rotor magnet mounted on the rotor via a yoke, and a rotor magnet. In a motor including a stator disposed radially inward or outward in opposition, the yoke includes an annular yoke body that covers an outer peripheral surface or an inner peripheral surface of the rotor magnet, and an upper end surface and a lower end of the rotor magnet. A yoke flange that covers one or both of the end faces, wherein the yoke flange extends radially inward or outward from one or both of the upper end and the lower end of the yoke main body, and And protrudes inward or outward beyond the inner or outer peripheral surface.

According to the present invention, the yoke has an annular yoke main body that covers the outer peripheral surface (or the inner peripheral surface) of the rotor magnet, and a yoke flange that covers one or both of the upper end surface and the lower end surface of the rotor magnet. Therefore, the yoke main body and the yoke flange function as a back yoke of the rotor magnet. The yoke flange extends inward (or outward) in the radial direction and projects inward (or outward) beyond the inner peripheral surface (or outer peripheral surface) of the rotor magnet. Since the leakage of the magnetic flux flowing from the motor to the stator and the magnetic flux flowing from the stator to the rotor magnet is reduced, the loss of the magnetic flux is reduced, and the back electromotive force generated thereby is increased, and the rotational torque of the motor can be increased. Further, since the yoke flange covers one or both of the upper end surface and the lower end surface of the rotor magnet, the yoke flange is magnetized by the rotor magnet. Therefore, the tip of the yoke flange magnetically attracts the stator. Therefore, even when a single ball bearing or a combination of a single ball bearing and a sliding bearing is used as a bearing, a preload is applied to the bearing by this magnetic attraction, and a dedicated spring means is added or the magnetic force is increased. The bearing can be rotated stably without any structural restrictions such as a structure that is deviated by the suction action. When a combination of a sleeve bearing and a slide bearing for thrust is used as the bearing, the magnetic attraction can prevent the rotor from coming off.

Further, according to the present invention, a notch is formed in the yoke flange of the yoke corresponding to a magnetic pole boundary area of the rotor magnet, and the notch is directed from a tip of the yoke flange toward the yoke main body. And extending radially outward or inward.

According to the present invention, the yoke flange is provided with a notch corresponding to the magnetic pole boundary region of the rotor magnet, so that the notch forms a flange projection. It corresponds to each magnetic pole. Therefore, the flange protrusions of the yoke flange are magnetized by the corresponding magnetic poles of the rotor magnet, and there is little magnetic mutual interference between adjacent flange protrusions, so that the effect of the yoke flange can be further enhanced.

Further, the present invention is characterized in that a tip end of the yoke flange extends radially inward or outward above the stator. According to the invention, the tip of the yoke flange extends above the stator, so that the tip is located close to the stator. Therefore, this makes it possible to increase the back electromotive force and increase the biasing force acting on the rotor. This biasing force refers to a suction force having an axial component acting between the yoke flange, which is a part of the rotor, and the stator.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. First Embodiment FIG. 1 is a sectional view showing one half of a first embodiment of a motor according to the present invention, which is applied to an outer rotor type motor for driving a recording disk. FIG.
FIG. 2 is a plan view showing a part of a yoke and a configuration related thereto in the motor of FIG. 1.

Referring to FIG. 1, the illustrated motor includes a housing 2 and a rotor 4 rotatable relative to the housing 2. The housing 2 has a plate-shaped housing body 6.
A bearing support member 8 is fixed to the center of the. Although not shown, the housing body 6 is attached to, for example, a base member of a disk drive. Note that the bearing support member 8 can be formed integrally with the housing body 6.

The bearing support member 8 includes a pair of bearings 10 and 12.
, The rotor 4 is rotatably supported. The rotor 4 includes a rotor body 18 having a circular end wall 14 and a peripheral side wall 16 extending in the axial direction (vertical direction in FIG. 1) from the outer peripheral portion of the end wall 14. The member 20 is mounted, and one end (upper end) of the shaft member 22 is fixed to the annular mounting support member 20. The pair of bearings 10 and 12 are interposed between the bearing support member 8 of the housing 2 and the shaft member 22 of the rotor 4. In this embodiment, the bearings 10 and 12 are constituted by ball bearings, and the outer rings 24 and 26 of the bearings 10 and 12 are connected to the bearing support member 8.
The outer races 28 and 30 are fixed to the inner peripheral surface of the shaft member 22 by, for example, an adhesive, and a plurality of balls are fixed between the outer races 24 and 26 and the inner races 28 and 30. 32 and 34 are provided. The inner peripheral surface of the bearing support member 8 is provided with the outer races 2 of the bearings 10 and 12.
An annular protrusion 36 is provided for keeping the 4, 26 at a predetermined interval. Note that, as in this embodiment, the bearing support member 8
Instead of the annular projection 36 integrated with the outer ring 24, an annular spacer separate from the bearing support member 8 may be interposed between the outer rings 24 and 26.

A yoke 38 is mounted on the inner peripheral surface of the peripheral side wall 16 of the rotor body 18, and an annular rotor magnet 40 is mounted via the yoke 38. A stator 41 is disposed radially inward facing the rotor magnet 40. The stator 41 includes a stator core 42 formed by stacking core plates formed of, for example, a silicon steel plate, and a coil 44 wound around the stator core 42. It is mounted on the outer peripheral surface. In this embodiment, a rectangular opening 46 is formed in the housing body 6 corresponding to each coil 44 wound around the stator core 42, and a part of each coil 44 is accommodated in the corresponding opening 46. A sheet-like member 48 for covering the opening 46 is attached to the outer surface of the housing body 6.
Incidentally, the yoke 38 and the configuration related thereto will be described later.

An annular recess 50 is provided in the inner peripheral portion of the rotor body 18.
The annular concave magnet 50 is provided in the annular concave portion 50. For example, when a recording disk such as a floppy disk is removably mounted on the rotor 4,
The disk support 54 of the recording disk is
The recording disk is attracted and held by the rotor 4 while being supported by the shaft member 22 and magnetically attracted by the attracting magnet 52.

Next, the yoke 38 and its related structure will be described with reference to FIG. 2 together with FIG. The yoke 38 is formed of a magnetic material such as iron, and has a substantially L-shaped cross section. The yoke 38 has an annular yoke main body 62 and a yoke flange extending radially inward from one end (upper end) of the yoke main body 62. 64. In this embodiment, the yoke main body 62 and the yoke flange 64 are formed integrally, the yoke main body 62 contacts and covers the outer peripheral surface of the rotor magnet 40, and the yoke flange 64 is connected to one end surface of the rotor magnet 40 (in FIG. The yoke main body 62 and the yoke flange 64 function as a back yoke of the rotor magnet 40. The back yoke has an effect of forming a magnetic path of a magnet (in this embodiment, the rotor magnet 40) to increase the magnetic action of the magnet.

The rotor magnet 40 is radially magnetized since the stator 41 is disposed radially inside the rotor magnet 40, and has an N-pole region 66 on its inner periphery as shown in FIG.
(A region magnetized to the N pole) and an S pole region 68 (a region magnetized to the S pole) are alternately arranged, and the N pole region 66 and the S pole region 6 are arranged.
8, a magnetic pole boundary area exists. What is the magnetic pole boundary area?
This is a region where the pole is switched from the S pole to the S pole or from the S pole to the N pole. The region is substantially not magnetized, or has a small magnetic force even when magnetized, and hardly acts on the stator 41. .

The distal end of the yoke flange 64 of the yoke 38 extends radially inward, protrudes inward beyond the inner peripheral surface of the rotor magnet 46, and extends above the outer peripheral portion of the stator core 42. By,
The distal end of the yoke flange 64 can be brought closer to one side (the upper end face in FIG. 1) of the stator core 42 (see FIG. 1). A notch 70 is formed in the yoke flange 64 corresponding to the magnetic pole boundary area, and each notch 70 linearly extends radially outward from the tip of the yoke flange 64 toward the yoke main body 62. , Such a notch 70
Is formed on the yoke flange 64 so that the N pole region 66 of the rotor magnet 46 is spaced apart in the circumferential direction.
And flange projections 72a, 72b corresponding to S pole region 68
Is provided.

In order to configure the rotor magnet 40 and the yoke 38 in this manner, it is desirable to mount the non-magnetized rotor magnet 40 on the yoke 38 and magnetize the rotor magnet 40 in this mounted state.
After the rotor magnet 40 is mounted on the rotor magnet 40, the magnetic pole boundary area of the rotor magnet 40 is
Can easily correspond to the notch 70.

In the motor having such a yoke 38, the yoke flange 64 extends above the outer peripheral portion of the stator 41 beyond the rotor magnet 40, so that one side of the rotor magnet 40 (the upper side in FIG. 1) The magnetic flux from the rotor magnet 40 flows to the stator core 42 via the yoke flange 64, and the magnetic flux from the stator core 42 flows to the rotor magnet 40 via the yoke flange 64, thereby reducing the leakage of the magnetic flux on one side of the rotor magnet 40. Thus, the back electromotive force is increased, and the rotational torque of the motor can be improved.

The yoke flange 64 is provided with flange projections 72a and 72b corresponding to the N-pole area 66 and the S-pole area 68 of the rotor magnet 40, so that these flange projections 72a and 72b correspond. Strongly magnetized by the N pole region 66 and the S pole region 68, the yoke flange 64
By increasing the effect of (1), a large back electromotive force can be obtained, and the biasing force acting on the rotor 4 can be increased. These effects can be further enhanced by bringing the tip of the yoke flange 64 closer to the stator core 42.

Further, since the notch 70 exists between the flange projections 72a and 72b of the yoke flange 64, the magnetic interference of the magnetized flange projections 72a and 72b is reduced, and the flange projection 72a has the N pole. And the flange protrusion 72b can act as a magnetic pole of the S pole, and the effect of the yoke flange 64 can be enhanced.

In this embodiment, the rotor magnet 4
In order to enhance the radial magnetic action between the stator core 42 and the stator core 42, the tip of the stator core 42 is deformed slightly upward toward the rotor magnet 40, and the tip of the stator core 42 faces the inner peripheral surface of the rotor magnet 40. are doing.

In the above-described embodiment, the yoke flange 64 is provided at one end of the yoke main body 62. However, as shown in FIG. 3, yoke flanges may be provided at both ends of the yoke main body. Referring to FIG. 3 showing a modified form of the yoke, the illustrated yoke 82 includes an annular yoke main body 84, and a yoke flange 8 is provided at both ends of the yoke main body 84.
6,88 are provided. The yoke body 84 contacts and covers the outer peripheral surface of the rotor magnet 40, one yoke flange 86 contacts and covers one end surface (upper end surface) of the rotor magnet 40, and the other yoke flange 88 covers the rotor magnet 40. In contact with and covers the other end surface (lower end surface) of the. The yoke 84 may be divided for assembly.

Notches 90 and 92 are formed in the yoke flanges 86 and 88 corresponding to the magnetic pole boundary areas of the rotor magnet 40, as described above.
2, the yoke flanges 86 and 88 are formed with flange protrusions 94 and 96 corresponding to the N pole region and the S pole region of the rotor magnet 40.

In the motor having the yoke 82 of this modified embodiment, the flange projection 94 of the yoke flange 86 is
Also, as in the embodiment of FIG. 2, since it extends above the inner peripheral surface of the rotor magnet 40 and above the stator core 42 (see FIG. 1), the same operation and effect as described above, that is, the back electromotive force is increased. be able to. In addition, since a similar yoke flange 88 is provided at the other end of the yoke main body 84, the leakage of magnetic flux can be reduced on the other side of the rotor magnet 40, and the efficiency of the magnetic circuit can be further increased. The back electromotive force can be increased.

Second Embodiment FIG. 4 is a sectional view showing one half of a second embodiment of a motor according to the present invention, which is applied to an outer rotor type motor for rotatingly driving a recording disk. . FIG.
FIG. 5 is a plan view showing a part of a ring member and a configuration related thereto in the motor of FIG. 4. In the first embodiment shown in FIGS. 1 and 2, the present invention is applied to an outer rotor type motor in which a rotor magnet is disposed outside the stator in the radial direction. Is applied to an inner rotor type motor in which a rotor magnet is disposed.

Referring to FIG. 4, the illustrated motor includes a housing 102 and a rotor 104 that is rotatable relative to the housing 102. The housing 102 includes a circular housing main body 106, an annular plate-like member 107 provided inside the housing main body 106 in the radial direction, and a bearing support member 108 provided at the center of the plate-like member 107. I have. Although not shown, the housing body 106 is attached to, for example, a base member of a disk drive. Note that the plate-like member 107 and the bearing support member 108 may be formed integrally with the housing body 106.

One bearing 110 is mounted on the bearing support member 108.
, The rotor 104 is rotatably supported. The rotor 4 has a substantially short cylindrical rotor body 112, and one end (upper end) of a shaft member 114 is fixed to the center of the rotor body 112. The bearing 110 is mounted on the housing 10.
2 bearing support member 108 and shaft member 114 of rotor 104
And is interposed between them. In this embodiment, the bearing 110 is formed of a ball bearing, and the outer ring 116 of the bearing 110 is fixed to the inner peripheral surface of the bearing support member 108 by, for example, an adhesive, and the outer ring 118 is fixed to the outer peripheral surface of the shaft member 114 by, for example, an adhesive. And a plurality of balls 120 are disposed between the outer ring 118 and the inner ring 116.

In this embodiment, the rotor body 112 is made of a magnetic material such as iron, and the rotor body 112 forms a part of the yoke. An annular rotor magnet 122 is mounted on the outer peripheral surface of the rotor main body 112. In addition, a stator 124 is disposed radially outward facing the rotor magnet 122. The stator 124 has a stator core 126 and a coil 128 wound around the stator core 126, and the stator core 126 is mounted on the inner peripheral surface of the housing main body 106 of the housing 102. A rectangular opening 130 is formed in the plate-shaped member 107 corresponding to each coil 128 wound on the stator core 126, and a part of each coil 128 corresponds to the opening 130.
Housed within.

An annular concave portion 1 is provided on the inner peripheral portion of the rotor body 112.
The annular concave portion 132 is provided with an annular attracting magnet 134. For example, when a recording disk such as a floppy disk is detachably mounted on the rotor 104, the disk support 136 of the recording disk is supported by the flange 138 of the shaft member 114, and
It is magnetically attracted by the attraction magnet 52 and is thus attracted and held by the rotor 104.

In this embodiment, the outer peripheral surface of the rotor main body 112 is in contact with and covers the inner peripheral surface of the rotor magnet 122. Therefore, the outer peripheral portion of the rotor main body 112 functions as the yoke main body in the first embodiment. In connection with this, an annular member 140 protruding outward in the radial direction is mounted on the upper end of the outer periphery of the rotor main body 112. The annular member 140 is formed of a magnetic material such as iron, contacts and covers one end face (the upper end face in FIG. 4) of the rotor magnet 122, and functions as a yoke flange in the first embodiment.

Referring also to FIG.
2, the stator 124 is disposed radially outward, so that the stator 124 is magnetized in the radial direction, and the N pole region 142 and the S pole region 144 are alternately formed on the outer periphery thereof, as shown in FIG. The magnetic pole boundary region exists between the N pole region 142 and the S pole region 144.

An annular member 1 functioning as a yoke flange
The tip of the stator core 1 extends radially outward and projects outward beyond the outer peripheral surface of the rotor magnet 122.
The upper end of the annular member 140 can be made closer to one side (the upper end face in FIG. 4) of the stator core 126 (see FIG. 4). In addition, the annular member 140 includes
Notches 146 are formed corresponding to the magnetic pole boundary areas, and each notch 146 is formed from the tip of the annular member 140 to the rotor body 112.
, And extends linearly inward in the radial direction toward the annular member 14 by forming such a notch 146.
0, the rotor magnet 122 is spaced apart in the circumferential direction.
148 corresponding to the N pole region 142 and the S pole region 144
(Functioning as a flange protrusion in the first embodiment) is provided.

In the motor having such a configuration, the annular member 1
Since the leading end of the rotor magnet 40 extends above the inner peripheral portion of the stator 124 beyond the rotor magnet 122, the leakage of magnetic flux on one side (the upper side in FIG. 4) of the rotor magnet 122 is small, thereby increasing the back electromotive force. Become
The rotational torque of the motor can be improved. Also,
The protrusion 148 of the annular member 140 is
, The rotor 104 has the stator 1
A biasing force acts in the direction approaching (downward in FIG. 4), so that a desired preload can be applied to the bearing 110. In addition, since the annular member 140 is provided with a protrusion 148 corresponding to the N pole region 142 and the S pole region 144 of the rotor magnet 122, the protrusion 148 corresponds to the corresponding N pole region 142 and S pole region 144. Is strongly magnetized. Further, since the notch 146 exists between the projections 148 of the annular member 140, magnetic interference of the magnetized projections 148 can be reduced.

In the above-described embodiment, the annular member 140 is attached to one end of the rotor body 112 functioning as a part of the yoke.
However, as shown in FIG. 6, annular members may be provided at both ends of the rotor body. Referring to FIG. 6 showing a part of a modified form of the rotor, the rotor main body 112A
Annular members 162, 162 extending radially outward
166 are provided. The rotor body 112A contacts and covers the inner peripheral surface of the rotor magnet 122, one annular member 162 contacts and covers one end surface (upper end surface) of the rotor magnet 122, and the other annular member 16
Reference numeral 4 is in contact with and covers the other end surface (lower end surface) of the rotor magnet 122. In this variation, the rotor body 112
A functions as a yoke main body, and the annular member 16
2,164 function as a yoke flange.

The annular members 162 and 164 have notches 166 and 1 corresponding to the magnetic pole boundary areas of the rotor magnet 122.
68 are formed, and the annular members 162 and 164 are provided with the rotor magnets 12 by the notches 166 and 168.
Projections 170 and 172 corresponding to the N pole region and the S pole region are formed.

In the motor having the rotor 112A of this modified embodiment, the protrusion 170 of the annular member 162 extends upward beyond the outer peripheral surface of the rotor magnet 122 and above the stator core 126 (see FIG. 4). A similar effect can be obtained, that is, the back electromotive force can be increased, and a preload can be applied to the bearing 110. In addition, a similar annular member 1 is provided at the other end of the rotor body 112A.
Since the 64 is provided, the leakage of the magnetic flux can be reduced on the other side, and the efficiency of the magnetic circuit can be further increased and the back electromotive force can be increased. The other annular member 164 is configured to be shorter in the radial direction than the one annular member 162. For example, as shown in FIG. 6, the distal end is substantially the same as the outer peripheral surface of the rotor magnet 122. It can be configured to be With this configuration, the other annular member 164 mainly acts to increase the back electromotive force, and the one annular member 162
Thus, a predetermined preload can be applied to the bearing 110.

Although the embodiments of the motor according to the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and corrections can be made without departing from the scope of the present invention. For example, the first embodiment has been described as applied to a motor having a bearing support structure with a pair of ball bearings, and the second embodiment has been described as being applied to a motor having a bearing support structure with one ball bearing. However, without being limited to these, the present invention can also be applied to a motor having a bearing support structure that requires a magnetic preload, such as a sleeve bearing (oil-impregnated bearing) and a contact type thrust sliding bearing. Also in the motor, the magnetic biasing force generated in relation to the yoke flange of the yoke can be used as a preload applied in the thrust direction.

In the illustrated embodiment, the present invention is applied to a motor for rotationally driving a recording disk such as a floppy disk. However, the present invention is not limited to this, and a hard disk, a magneto-optical disk, a CD-RO
The present invention can be similarly applied to a motor for rotationally driving M, DVD, and the like, and a motor such as a general DC main motor.

[0043]

According to the motor of the first aspect of the present invention, the back electromotive force generated by the action of the yoke flange of the yoke increases, and the rotational torque of the motor can be increased. Also, the tip of the yoke flange magnetically attracts the stator, and the magnetic attractive force can apply a biasing force to the rotor.

According to the motor of the second aspect of the present invention, since the magnetic mutual interference between the adjacent flange projections is small, the back electromotive force can be increased and the bias force acting on the rotor can be reduced. Can be bigger. Further, according to the motor of the third aspect of the present invention, the back electromotive force can be further increased, and the biasing force acting on the rotor can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one half of a first embodiment of a motor according to the present invention.

FIG. 2 is a plan view showing a part of a yoke and a configuration related thereto in the motor of FIG. 1;

FIG. 3 is a cross-sectional view showing a modification of a yoke.

FIG. 4 is a sectional view showing one half of a second embodiment of the motor according to the present invention;

FIG. 5 is a plan view showing a part of an annular member and a configuration related to the annular member in the motor of FIG. 4;

FIG. 6 is a sectional view showing a part of a modified form of the rotor body.

[Explanation of symbols]

 2,102 Housing 4,104 Rotor 10,12,110 Bearing 18,112,112A Rotor body 38,82 Yoke 40,122 Rotor magnet 41,124 Stator 42,126 Stator core 62,84 Yoke body 64,86,88 Yoke flange 66, 142 N polar region 68, 144 S polar region 70, 90, 92, 146166, 168 Notch 72a, 72b, 94, 96 Flange projection 140, 162, 164 Ring member 170, 172 Projection

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H02K 21/22 H02K 21/22 M

Claims (3)

[Claims] 1. A housing, a rotor rotatably supported by the housing via a bearing, a rotor magnet mounted on the rotor via a yoke, and a radially inner or outer surface facing the rotor magnet. Wherein the yoke includes an annular yoke main body that covers an outer peripheral surface or an inner peripheral surface of the rotor magnet, and one or both of an upper end surface and a lower end surface of the rotor magnet. A yoke flange for covering, wherein the yoke flange extends radially inward or outward from one or both of an upper end and a lower end of the yoke main body to cover an inner peripheral surface or an outer peripheral surface of the rotor magnet. A motor characterized by projecting inward or outward beyond. 2. The yoke flange of the yoke,
A notch is formed corresponding to a magnetic pole boundary region of the rotor magnet, and the notch extends radially outward or inward from a tip of the yoke flange toward the yoke main body. Item 7. The motor according to Item 1. 3. The motor according to claim 1, wherein a tip portion of the yoke flange extends radially inward or outward above the stator.