CN110476322B

CN110476322B - Motor and electric power steering device

Info

Publication number: CN110476322B
Application number: CN201880022338.3A
Authority: CN
Inventors: 村上俊辅; 金子拓也; 一圆明; 金城秀幸
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2017-03-31
Filing date: 2018-02-21
Publication date: 2021-10-29
Anticipated expiration: 2038-02-21
Also published as: WO2018180037A1; CN110476322A

Abstract

The motor (1) comprises a rotor (40) and a stator (100), wherein the rotor (40) comprises a rotor core (41) and a plurality of sector magnets (43), the outer surfaces of the sector magnets (43) are in a circular arc, the stator (100) comprises an annular core back part (104), a plurality of teeth (105) extending from the core back part (104) to the radial inner side and a plurality of umbrella-shaped parts (106), the umbrella-shaped parts (106) are opposite to the rotor, the umbrella-shaped parts (106) are connected with the radial inner end parts of the teeth (105) and extend to the two circumferential sides, and the umbrella-shaped parts (106) at least comprise: a 1 st bent part (110) bent toward the radial inner side; and 2 nd and 3 rd bent portions (120, 130) located at both ends of the 1 st bent portion (110) on the circumferential outer side and bent outward in the radial direction.

Description

Motor and electric power steering device

Technical Field

The present invention relates to a motor and an electric power steering apparatus.

Background

A motor having a rotor of an SPM (Surface Magnet) type in which a Magnet is fixed to an outer Surface of a rotor core is known. For example, in the motor disclosed in japanese patent application laid-open No. 2016 and 63728 (patent document 1), a fan-shaped magnet having an arc-shaped outer peripheral portion and a planar inner peripheral portion and having a D-shaped axial cross section is used as the magnet.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2016-63728

Disclosure of Invention

Problems to be solved by the invention

In patent document 1, magnetic flux is radially generated from a magnet. Thus, vibration caused by pulsation is generated. Therefore, the motor of patent document 1 has a problem of poor magnetic characteristics.

Further, since the outer peripheral portion of each of the sector-shaped magnets of patent document 1 has an arc shape, the amount of material used for molding each of the sector-shaped magnets increases. Therefore, there is a problem that the cost required for manufacturing the motor is high.

In view of the above problems, an object of the present invention is to provide a motor and an electric power steering apparatus that maintain magnetic characteristics and reduce manufacturing costs.

Means for solving the problems

One embodiment of a motor of the present invention includes: a rotor; and a stator surrounding a radially outer side of the rotor, the rotor comprising: a shaft extending in an axial direction; a rotor core mounted to a shaft; and sector magnet, it is a plurality of sector magnet is installed in rotor core's surface along circumference, and is a plurality of sector magnet's surface is the circular arc of a circle, and the stator contains: an annular iron core back; a plurality of teeth extending radially inward from the core back; and a plurality of umbrella parts facing the rotor, the plurality of umbrella parts being connected to respective radially inner end portions of the teeth and extending to both circumferential sides, the umbrella parts including at least: a 1 st bend portion, the 1 st bend portion being bent toward a radially inner side; and 2 nd bend portions and 3 rd bend portions, the 2 nd bend portions and the 3 rd bend portions being located at both ends of the 1 st bend portion on the outer side in the circumferential direction and being bent outward in the radial direction.

Effects of the invention

According to one embodiment of the present invention, a motor and an electric power steering apparatus can be provided that maintain magnetic characteristics and reduce manufacturing costs.

Drawings

Fig. 1 is a sectional view of a motor in an embodiment.

Fig. 2 is a plan view of the rotor and the stator in the embodiment.

Fig. 3 is a plan view of a sector magnet in the embodiment.

Fig. 4 is an enlarged view of a part of fig. 2.

Fig. 5 is an enlarged view of a part of fig. 4.

Fig. 6 is a perspective view of a part of a stator in the embodiment.

Fig. 7 is a schematic diagram of an electric power steering apparatus according to an embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding portions are denoted by the same reference characters, and description thereof will not be repeated.

In the following description, as shown in fig. 1, the central axis a of the rotor, i.e., the axial direction in which the shaft extends, is defined as the vertical direction, the opening portion side of the housing is defined as the upper side, and the bottom portion side of the housing is defined as the lower side. However, the vertical direction in the present specification is used for specifying the positional relationship, and therefore, the actual direction is not limited. That is, the lower direction does not necessarily mean the gravity direction.

The direction perpendicular to the center axis a of the rotor is a radial direction, and the radial direction is centered on the center axis a. The axial direction around the central axis a of the rotor is defined as the circumferential direction.

In the present specification, "extend in the axial direction" includes a state of strictly extending in the axial direction and a state of extending in a direction inclined in a range of less than 45 degrees with respect to the axial direction. Also, in this specification, "extend in the radial direction" includes a state of extending strictly in the radial direction and a state of extending in a direction inclined in a range of less than 45 degrees with respect to the radial direction.

(Motor)

A motor according to an embodiment of the present invention will be described with reference to fig. 1 to 6. As shown in fig. 1, the motor 1 mainly includes a housing 10,

bearings

21 and 22, a bearing holder 30, a rotor 40, and a stator 100.

The case 10 has a bottomed cylindrical shape. Namely, the housing 10 has a bottom 11. The upper portion of the housing 10 is open. The housing 10 internally houses the rotor 40 and the stator 100.

The

bearings

21 and 22 rotatably support the shaft 42 of the rotor 40. The bearing 21 disposed on the upper side in the axial direction is held by a bearing holder 30. The bearing 22 disposed axially downward is held by the bottom 11 of the housing 10.

< rotor >

As shown in fig. 1 and 2, the rotor 40 includes a rotor core 41, a shaft 42, and a plurality of sector magnets 43.

The rotor core 41 has a cylindrical shape. In the present embodiment, as shown in fig. 2, the rotor core 41 has an octagonal outer shape when viewed from the axial upper side. The outer shape of the rotor core 41 is not particularly limited. The rotor core 41 is formed by laminating a plurality of electromagnetic steel plates in the axial direction.

A plurality of rotor core grooves 41a are formed in the outer surface of the rotor core 41 on the radially outer side, and the rotor core grooves 41a extend in the axial direction and are recessed inward in the radial direction. The rotor core slots 41a are arranged at equal intervals in the circumferential direction.

The rotor core 41 has a shaft through hole 41b at the center. The shaft 42 shown in fig. 1 passes through the shaft through hole 41 b. The rotor core 41 is attached to a shaft 42. Specifically, the shaft 42 is directly or indirectly fixed to the rotor core 41. The fixing method is not particularly limited, and the fixing may be performed by press-fitting, adhesion, or the like. The rotor core 41 rotates together with the shaft 42.

The shaft 42 has a substantially cylindrical shape extending in the axial direction and centered on the central axis a. The shaft 42 may be a solid or hollow member.

A magnet is fixed to the outer surface of the rotor core 41. That is, the rotor 40 is an SPM (Surface-magnet) type. In the present embodiment, a plurality of sector magnets 43 are attached to the outer surface of the rotor core 41 in the circumferential direction. The magnet of the present embodiment includes 8 sector magnets 43.

The plurality of sector magnets 43 extend in the axial direction and are arranged in a ring around the center axis a. The outer surfaces of the plurality of sector magnets 43 form a circular arc. In the present embodiment, the outer surfaces of the plurality of sector magnets 43 form a part of a circle centered on the central axis a. This can reduce the amount of the waste material cut out from the base material. Therefore, the manufacturing cost of the motor 1 can be reduced. Since such sector magnets 43 are used, pulsation is suppressed on the stator 100 side, not on the rotor 40 side.

The sector magnet 43 is a plate-like member extending in the axial direction. As shown in fig. 3, the sector magnet 43 has an inner surface portion 43a, an outer surface portion 43c, and a pair of side surface portions 43 b.

The inner surface portion 43a is linear when viewed from the axially upper side. The inner surface portion 43a is in contact with the outer surface of the rotor core 41. The pair of side surface portions 43b extend radially outward from the circumferential one and other end portions of the inner surface portion 43 a. The pair of side surface portions 43b are located on opposite sides in the circumferential direction. The outer surface portion 43c is an outer surface of the sector magnet 43 on the radially outer side.

The circumferential ends of the outer surface portion 43c are connected to the side surface portion 43 b. In the present embodiment, the outer surface portion 43c has a curved shape that protrudes outward in the radial direction. The outer surface portion 43c has a curved shape when viewed from the axially upper side.

The adjacent sector magnets 43 are circumferentially opposed to each other. The circumferential side surface portion 43b of the circumferential sector magnet 43 is opposed to the circumferential side surface portion 43b of the circumferential magnet with a gap therebetween in the circumferential direction. The rotor core slots 41a are located between adjacent segment magnets 43 in the circumferential direction.

In the present embodiment, the size of the rotor core 41 is the same as the size of the sector magnet 43 in the axial direction. The upper surface of the rotor core 41 is flush with the upper surface of the sector magnets 43. The lower surface of the rotor core 41 is flush with the lower surface of the sector magnet 43.

The axial dimension of the sector magnet 43 is the same as the axial dimension of the stator core 101 described later. The axial dimension of the sector magnet 43 may be different from the axial dimension of the stator core 101.

< stator >

[ Structure of stator ]

As shown in fig. 1 and 2, the stator 100 surrounds the rotor 40 on the radially outer side. As shown in fig. 1, the stator 100 includes a stator core 101, an insulator 102, and a coil 103.

The insulator 102 covers at least a portion of the stator core 101. The insulator 102 is made of an insulator such as an insulating resin, and is attached to each tooth 105.

The coil 103 is formed by winding around a tooth 105 of the stator core 101 via an insulator 102.

Stator core 101 is formed by laminating a plurality of electromagnetic steel plates in the axial direction. The plurality of electromagnetic steel sheets are fixed by caulking or the like. The stator core may be formed of one member. The stator core 101 of the present embodiment is configured by a plurality of split cores that can be split in the circumferential direction. The stator core is not particularly limited, and may be formed of a straight core, a circular core, or the like.

As shown in fig. 2 and 4 to 6, stator core 101 includes a core back portion 104, teeth 105, and an umbrella portion 106. In the present embodiment, as shown in fig. 6, the core back portion 104, the teeth 105, and the umbrella portion 106 have the same size in the axial direction. The upper surface of the core back 104, the upper surfaces of the teeth 105, and the upper surfaces of the umbrellas 106 are flush. The lower surface of the core back 104, the lower surfaces of the teeth 105, and the lower surfaces of the umbrella portions 106 are flush. The axial dimensions of the core back 104, the teeth 105, and the umbrella portion 106 may be different.

Core back 104 is annular. The core back 104 has a core back groove 104a recessed radially inward in the outer surface on the radially outer side. Each core back slot 104a is located radially outward of each tooth 105.

The plurality of teeth 105 extend radially inward from the core back 104. The teeth 105 are arranged at equal intervals in the circumferential direction on the radially inner surface of the core back 104. The circumferential width of the teeth 105 in the present embodiment is fixed, but may not be fixed.

Between adjacent teeth 105, a groove 107 is provided as a circumferential gap. The stator 100 of the present embodiment has 12 slots 107. That is, the motor 1 of the present embodiment has 12 slots and 8 poles.

As shown in fig. 4, at the radially inner end of the teeth 105, the circumferential distance L1 between adjacent teeth 105 (groove 107) is greater than the circumferential width L2 of the teeth 105. This can increase the amount of interlinkage magnetic flux, and thus can improve magnetic characteristics.

The plurality of umbrellas 106 are opposed to the rotor 40. The plurality of umbrella portions 106 are connected to the radially inner end portions of the teeth 105 and extend to both circumferential sides. That is, the circumferential width of the umbrella portion 106 is larger than the circumferential width of the radially inner end portion of the tooth 105. The plurality of umbrella-shaped portions 106 are arranged at equal intervals in the circumferential direction.

As shown in fig. 4 to 6, the umbrella portion 106 includes at least the 1 st bend 110, the 2 nd bend 120, and the 3 rd bend 130. In the present embodiment, the radially inner surface of the umbrella portion 106 is formed only by the 1 st to 3 rd bent portions 110 to 130.

The 1 st bent portion 110 is bent toward the radially inner side. The 2 nd bend 120 and the 3 rd bend 130 are located at both ends of the 1 st bend 110 on the outer side in the circumferential direction and are bent outward in the radial direction. The present inventors have focused on using the sector magnet 43 that can reduce the manufacturing cost and adjusting the shape of the magnetic flux according to the shape of the stator 100. The present inventors have found that the shape of the magnetic flux can be adjusted to a sinusoidal shape by the stator 100 including the umbrella-shaped portion 106 having the 1 st to 3 rd bent portions 110 to 130. That is, the distribution of the magnetic flux generated from the sector magnet 43 can be adjusted to a sine wave shape by the 1 st to 3 rd bent portions 110 to 130 of the umbrella portion 106, and thus the magnetic characteristics can be maintained.

Specifically, the 1 st bend 110 is located at the center of the umbrella portion 106 in the circumferential direction. The 1 st bend 110 is a curved surface that protrudes radially inward on the radially inner surface of the umbrella portion 106. The 1 st bend 110 is a surface defined by a curvature R1. The 1 st bend 110 extends in the axial direction on the radially inner surface of the umbrella portion 106. The 1 st bend 110 has a curved outer shape when viewed in the axial direction.

A 2 nd bend 120 is present at one side of the 1 st bend 110 in the circumferential direction. There is a 3 rd bent portion 130 at the other side of the 1 st bent portion 110 in the circumferential direction. The 1 st to 3 rd bent parts 110 to 130 are connected.

The 2 nd and 3 rd bent

portions

120 and 130 are located at the end of the umbrella portion 106. The 2 nd and 3 rd bent

portions

120 and 130 are curved surfaces that are convex radially outward on the radially inner surface of the umbrella portion 106. The 2 nd and 3 rd bent

portions

120 and 130 are surfaces defined by curvatures R2 and R3. The 2 nd and 3 rd bent

portions

120 and 130 extend in the axial direction on the radially inner surface of the umbrella portion 106. The profiles of the 2 nd and 3 rd bent

portions

120 and 130 are curved when viewed from the axial direction.

As shown in fig. 5, the curvature R1 of the 1 st bend 110 is different from the curvatures R2, R3 of the 2 nd and 3 rd bends 120, 130. This makes it possible to easily adjust the magnetic flux distribution to a sinusoidal form, and thus to maintain the magnetic properties more. The curvature R1 of the 1 st bend 110 is greater than the curvatures R2, R3 of the 2 nd and 3 rd bends 120, 130. This makes it possible to further easily adjust the magnetic flux distribution to a sinusoidal form, and thus further maintain the magnetic characteristics. The curvature R2 of the 2 nd bend 120 may be the same as or different from the curvature R3 of the 3 rd bend 130.

The curvature R4 of the outer surface portion 43c of the sector magnet 43 shown in fig. 3 is larger than the curvature R1 of the 1 st bend 110 shown in fig. 5.

As shown in fig. 4 to 6, the 2 nd and 3 rd bent

portions

120 and 130 and the teeth 105 do not overlap each other in the circumferential direction because of their different circumferential positions. Specifically, the 2 nd and 3 rd bent

portions

120 and 130 are located on the outer side in the circumferential direction than the teeth 105. That is, the inflection point of the 1 st bend 110 and the 2 nd bend 120 and the inflection point of the 1 st bend 110 and the 3 rd bend 130 are located on the outer side in the circumferential direction than the teeth 105. This makes it possible to further easily adjust the magnetic flux distribution to a sinusoidal form, and thus further maintain the magnetic characteristics.

As shown in fig. 4, the circumferential distance L110 of the radially inner end of the 1 st bent portion 110 is greater than the circumferential distances L120, L130 of the radially inner ends of the 2 nd and 3 rd bent

portions

120, 130.

Circumferential distances L120 and L130 of the 2 nd and 3 rd bent

portions

120 and 130 are larger than a circumferential gap between adjacent umbrella-shaped portions 106 or are the same as the circumferential gap between adjacent umbrella-shaped portions 106. The stator 100 of the present embodiment is a so-called slot.

In the radially outer end region of the umbrella portion 106, the circumferential width L3 of the umbrella portion 106 becomes narrower toward the radially outer side. That is, the umbrella portion 106 is inclined so as to expand radially inward. Since both sides of the umbrella-shaped portion 106 in the circumferential direction are inclined surfaces, magnetic characteristics such as cogging, torque ripple, and output can be improved.

The radial thickness L4 of the umbrella 106 is larger than the radial thickness L5 of the fan-shaped magnet 43 or is the same as the radial thickness L5 of the fan-shaped magnet 43. By increasing the thickness L4 of the umbrella part 106, the magnetic flux can be efficiently moved, and thus the magnetic characteristics can be improved. By reducing the thickness L5 of the sector magnet 43, the amount of material used for molding the magnet can be reduced, and thus the manufacturing cost can be reduced.

The maximum circumferential width of the umbrella portion 106 is the same as the maximum circumferential width of the sector magnet 43.

The width of the gap 108 is smaller than the minimum width in the radial direction between the umbrella portion 106 and the sector magnet 43.

In the present embodiment, the umbrella-shaped portion 106 having the radially inner surface formed by the 1 st to 3 rd bent portions 110 to 130 is described as an example. The umbrella-shaped part of the present invention may have other bent parts, linear parts, etc. in addition to the 1 st to 3 rd bent parts 110 to 130. In this case, other curved portions, straight portions, and the like are disposed between the 1 st curved portion 110 and the 2 nd and 3 rd curved

portions

120 and 130. Furthermore, the 1 st to 3 rd bent portions 110 to 130 may be provided with projections, grooves, and the like.

(electric power steering apparatus)

An example in which the motor 1 is mounted on the electric power steering apparatus 500 will be described with reference to fig. 7.

Vehicles such as automobiles generally have an electric power steering apparatus. The electric power steering apparatus generates an assist torque for assisting a steering torque of a steering system generated by a driver operating a steering wheel. The assist torque is generated by the assist torque mechanism, and the operation load of the driver can be reduced. The assist torque mechanism includes, for example, a steering torque sensor, an ECU, a motor, a speed reduction mechanism, and the like. The steering torque sensor detects a steering torque in the steering system. The ECU generates a drive signal based on a detection signal of a steering torque sensor. The motor generates an assist torque corresponding to the steering torque in accordance with the drive signal, and transmits the assist torque to the steering system via the speed reduction mechanism.

The electric power steering apparatus 500 includes a steering system 520 and an assist torque mechanism 540.

The steering system 520 includes, for example, a steering wheel 521, a steering shaft 522 (also referred to as a "steering column"),

universal joints

523A, 523B, a rotary shaft 524 (also referred to as a "pinion shaft" or an "input shaft"), a rack-and-pinion mechanism 525, a rack shaft 526, left and right ball joints 552A, 552B,

tie rods

527A, 527B,

knuckles

528A, 528B, and left and right steered wheels (e.g., left and right front wheels) 529A, 529B. The steering wheel 521 is connected to the rotating shaft 524 via the steering shaft 522 and the

universal joints

523A and 523B. A rack shaft 526 is connected to the rotating shaft 524 via a rack and pinion mechanism 525. The rack and pinion mechanism 525 includes a pinion 531 provided on the rotating shaft 524 and a rack 532 provided on the rack shaft 526. A right steered wheel 529A is connected to a right end of the rack shaft 526 through a ball joint 552A, a tie rod 527A, and a knuckle 528A in this order. Similarly to the right side, a left steered wheel 529B is connected to the left end of the rack shaft 526 through a ball joint 552B, a tie rod 527B, and a knuckle 528B in this order. Here, the right side and the left side correspond to the right side and the left side, respectively, as viewed from the driver sitting on the driver's seat.

According to the steering system 520, a steering torque is generated by the driver operating the steering wheel 521, and is transmitted to the left and right steered

wheels

529A and 529B via the rack and pinion mechanism 525. This allows the driver to operate the left and right

steerable wheels

529A and 529B.

The assist torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU542, a motor 543, a reduction mechanism 544, and a power conversion device 545. The motor 543 corresponds to the motor 1.

The assist torque mechanism 540 supplies assist torque to the steering system 520 from the steering wheel 521 to the left and right steered

wheels

529A, 529B. The assist torque is also sometimes referred to as "additional torque".

The steering torque sensor 541 detects a steering torque of the steering system 520 applied by the steering wheel 521. The ECU542 generates a drive signal for driving the motor 543 based on a detection signal (hereinafter referred to as "torque signal") from the steering torque sensor 541. The motor 543 generates an assist torque corresponding to the steering torque in accordance with the drive signal. The assist torque is transmitted to the rotary shaft 524 of the steering system 520 via the speed reduction mechanism 544. The reduction mechanism 544 is, for example, a worm gear mechanism. The assist torque is further transmitted from the rotating shaft 524 to the rack and pinion mechanism 525.

The electric power steering apparatus 500 can be classified into a pinion assist type, a rack assist type, a column assist type, and the like according to a portion where assist torque is applied to the steering system 520. Fig. 7 illustrates a pinion assist type electric power steering apparatus 500. However, the electric power steering apparatus 500 may be a rack assist type, a column assist type, or the like.

The ECU542 can be inputted with not only a torque signal but also a vehicle speed signal, for example. The external device 560 is, for example, a vehicle speed sensor. Alternatively, the external device 560 may be another ECU that can communicate with an in-vehicle network such as can (controller a network). The microcontroller of the ECU542 can perform vector control or PWM control on the motor 543 in accordance with a torque signal, a vehicle speed signal, or the like.

ECU542 sets a target current value based on at least the torque signal. The ECU542 preferably sets the target current value in consideration of a vehicle speed signal detected by a vehicle speed sensor, and further, in consideration of a rotation signal of the rotor detected by an angle sensor. The ECU542 can control the drive current, which is a drive signal of the motor 543, so that the actual current value detected by the current sensor matches the target current value.

According to the electric power steering apparatus 500, the left and right steered

wheels

529A and 529B can be operated by the rack shaft 526 using a composite torque obtained by adding the assist torque of the motor 543 to the steering torque of the driver. In particular, by providing the motor 1, the electric power steering apparatus 500 can maintain the magnetic characteristics and reduce the manufacturing cost.

Here, the electric power steering apparatus 500 is described as an example of a method of using the motor 1, but the method of using the motor 1 is not limited. The motor of the present invention can be widely used for various apparatuses having various motors, such as a vacuum cleaner, a blower, a ceiling fan, a washing machine, a refrigerator, and an electric power steering apparatus.

The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims rather than the embodiments described above, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

Description of the symbols

1. 543 motor, 10 casing, 11 bottom, 21, 22 bearing, 30 bearing holder, 40 rotor, 41 rotor core, 41a rotor core slot, 41B shaft through hole, 42 shaft, 43 sector magnet, 43A inner surface portion, 43B side surface portion, 43c outer surface portion, 100 stator, 101 stator core, 102 insulator, 103 coil, 104 core back, 104a core back slot, 105 teeth, 106 umbrella portion, 107 slot, 108 gap, 110 1 st bending portion, 120 nd bending portion, 130 rd bending portion, 3 rd bending portion, 500 electric power steering device, 520 steering system, 521 steering wheel, 522 steering shaft, 523A, 523B universal joint, 524 rotation shaft, 525 rack and pinion mechanism, 526 rack shaft, 527A, 527B tie rod, 528A, 528B steering knuckle, 529A, 529B: steering wheels, 531 pinions, 532 racks, 540 auxiliary torque mechanisms, 541 steering torque sensors, 542ECU, 544 reduction mechanisms, 545 power conversion devices, 552A, 552B ball joints, 560 external equipment, a, central axis, L1, L110, L120, L130 distance, L2, L3 width, LL4, L5 thickness, R1, R2, R3, R4 curvature.

Claims

1. A motor, comprising:

a rotor; and

a stator surrounding a radially outer side of the rotor,

the rotor includes:

a shaft having a substantially cylindrical shape centered on a central axis extending in an axial direction;

a rotor core mounted to the shaft; and

a plurality of sector magnets circumferentially mounted on an outer surface of the rotor core,

the sector magnet is a plate-shaped member extending in the axial direction, and has an inner surface portion, a pair of side surface portions, and an outer surface portion,

the side surface portion on the other side in the circumferential direction of the sector-shaped magnet on the one side in the circumferential direction and the side surface portion on the one side in the circumferential direction of the magnet on the other side in the circumferential direction are opposed to each other with a gap in the circumferential direction,

the outer surfaces of the plurality of sector magnets form a portion of a circle centered on the central axis,

the stator includes:

an annular iron core back;

a plurality of teeth extending radially inward from the core back; and

a plurality of umbrella-shaped portions that face the rotor, are connected to respective radially inner end portions of the teeth, and extend to both circumferential sides,

the umbrella part at least comprises:

a 1 st bend portion, the 1 st bend portion being bent toward a radially inner side; and

a 2 nd bend portion and a 3 rd bend portion, the 2 nd bend portion and the 3 rd bend portion being located at both ends of the 1 st bend portion on the outer side in the circumferential direction and at an end portion of the umbrella-shaped portion and being bent outward in the radial direction,

the 1 st bent portion, the 2 nd bent portion and the 3 rd bent portion are connected in a circumferential direction,

the curvature of the outer surface portion of the sector magnet is larger than that of the 1 st bent portion,

the radial thickness of the umbrella-shaped part is larger than or equal to that of the fan-shaped magnet.

2. The motor of claim 1,

the umbrella part is composed of only the 1 st to 3 rd bending parts,

the curvature of the 1 st curved portion is different from the curvatures of the 2 nd and 3 rd curved portions.

3. The motor of claim 2,

the curvature of the 1 st curved portion is greater than the curvatures of the 2 nd and 3 rd curved portions.

4. The motor according to any one of claims 1 to 3,

at the radially inner ends of the teeth, the circumferential distance between adjacent teeth is greater than the circumferential width of the teeth.

5. The motor according to any one of claims 1 to 3,

in a radially outer end region of the umbrella portion, a circumferential width of the umbrella portion becomes narrower toward a radially outer side.

6. The motor according to any one of claims 1 to 3,

the stator contains 12 slots between the teeth,

the rotor contains 8 of the sector magnets.

7. The motor according to any one of claims 1 to 3,

the 2 nd bent portion and the 3 rd bent portion are located on the outer side in the circumferential direction than the teeth.

8. An electric power steering apparatus having the motor of any one of claims 1 to 7.