WO2018180037A1

WO2018180037A1 - Motor and electric power steering device

Info

Publication number: WO2018180037A1
Application number: PCT/JP2018/006222
Authority: WO
Inventors: 俊輔村上; 拓也金子; 明一円; 秀幸金城
Original assignee: 日本電産株式会社
Priority date: 2017-03-31
Filing date: 2018-02-21
Publication date: 2018-10-04
Also published as: CN110476322B; CN110476322A

Abstract

This motor (1) is provided with a rotor (40) and a stator (100). The rotor (40) includes a rotor core (41) and a plurality of segmented magnets (43). The outer surfaces of the plurality of segmented magnets (43) constitute arcs of a single circle. The stator (100) includes: an annular core back (104); a plurality of teeth (105) extending radially inward from the core back (104); and a plurality of umbrellas (106) which face the rotor, are each connected to the radially inner end of a corresponding one of the teeth (105), and each extend to both circumferential sides. Each of the umbrellas (106) at least has: a first curved section (110) curved radially inward; and second and third curved sections (120, 130) located at the opposite circumferentially outer ends of the first curved section (110) and curved radially outward.

Description

Motor and electric power steering device

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

A motor having an SPM (Surface Permanent Magnet) type rotor 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. 2016-63728 (Patent Document 1), a segment type magnet having an axial cross section formed in a D shape is used as a magnet. The inner peripheral part.

Japanese Unexamined Patent Publication No. 2016-63728

In Patent Document 1, magnetic flux is generated radially from the magnet. This causes vibration due to pulsation. For this reason, the motor of Patent Document 1 has a problem that the magnetic characteristics are poor.

Also, since the outer periphery of each segment type magnet of Patent Document 1 is arc-shaped, the amount of material used to form each segment type magnet increases. For this reason, there exists a problem that the cost required in order to manufacture a 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 can reduce manufacturing costs while maintaining magnetic characteristics.

One aspect of the motor of the present invention includes a rotor and a stator that surrounds the outer side in the radial direction of the rotor. The rotor has a shaft that extends in the axial direction, a rotor core that is attached to the shaft, and a circumferential surface on the outer surface of the rotor core. A plurality of segment magnets attached in the direction, the outer surface of the plurality of segment magnets forms a circular arc of the circle, and the stator includes an annular core back and a plurality of teeth extending radially inward from the core back And a plurality of umbrellas that face the rotor and are connected to respective radially inner ends of the teeth and extend on both sides in the circumferential direction, and the umbrella bends radially inward. And second and third curved portions that are located at both ends of the first curved portion in the circumferential direction and are curved toward the radially outer side.

According to one aspect of the present invention, it is possible to provide a motor and an electric power steering device that reduce the manufacturing cost while maintaining the magnetic characteristics.

FIG. 1 is a cross-sectional view of a motor in the embodiment. FIG. 2 is a plan view of the rotor and the stator in the embodiment. FIG. 3 is a plan view of the segment magnet in the embodiment. FIG. 4 is an enlarged view of a part of FIG. FIG. 5 is an enlarged view of a part of FIG. FIG. 6 is a perspective view of a part of the stator in the embodiment. FIG. 7 is a schematic diagram of the electric power steering apparatus according to the embodiment.

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

In the following description, as shown in FIG. 1, the central axis A of the rotor, that is, the axial direction in which the shaft extends is the vertical direction, the opening side of the housing is the upper side, and the bottom side of the housing is the lower side. However, the vertical direction in this specification is for use in specifying the positional relationship, and does not limit the actual direction. That is, the downward direction does not necessarily mean the direction of gravity.

Also, the direction orthogonal to the central axis A of the rotor is the radial direction, and the radial direction is centered on the central axis A. The circumference of the center axis A of the rotor is the circumferential direction.

Further, in this specification, “extending in the axial direction” includes a state extending in the axial direction strictly and a state extending in a direction tilted within a range of less than 45 degrees with respect to the axial direction. Similarly, “extending in the radial direction” in the present specification includes a state extending in the radial direction strictly and a state extending in a direction tilted within 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 FIGS. 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 housing 10 has a bottomed cylindrical shape. That is, the housing 10 has a bottom portion 11. The upper part of the housing 10 opens. The housing 10 accommodates the rotor 40 and the stator 100 therein.

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 the bearing holder 30. The bearing 22 disposed on the lower side in the axial direction is held on the bottom 11 of the housing 10.

<Rotor>
As shown in FIGS. 1 and 2, the rotor 40 includes a rotor core 41, a shaft 42, and a plurality of segment magnets 43.

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

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

The rotor core 41 has a shaft through hole 41b in the center. The shaft 42 shown in FIG. 1 is passed through the shaft through hole 41b. The rotor core 41 is attached to the shaft 42. Specifically, the shaft 42 is fixed directly or indirectly to the rotor core 41. The fixing means is not particularly limited, and may be fixed, for example, by press-fitting or adhesion. The rotor core 41 rotates with the shaft 42.

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

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

The plurality of segment magnets 43 extend in the axial direction and are arranged in a ring around the central axis A. The outer surfaces of the plurality of segment magnets 43 form one circular arc. In the present embodiment, the outer surfaces of the plurality of segment magnets 43 form part of a circle centered on the central axis A. As a result, the amount of discarded material to be scraped from the base material can be reduced. For this reason, the manufacturing cost of the motor 1 can be reduced. Since such a segment magnet 43 is used, pulsation is suppressed not on the rotor 40 side but on the stator 100 side.

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

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

The edge part of the circumferential direction both sides of the outer surface part 43c is connected to the side part 43b. In the present embodiment, the outer surface portion 43c has a curved shape that is convex outward in the radial direction. When viewed from the upper side in the axial direction, the outer shape of the outer surface portion 43c is a curve.

Adjacent segment magnets 43 face each other in the circumferential direction. The side surface portion 43b on the other side in the circumferential direction of the segment magnet 43 located on one side in the circumferential direction faces the side surface portion 43b on the one side in the circumferential direction in the magnet located on the other side in the circumferential direction with a gap in the circumferential direction. In the circumferential direction, the rotor core groove 41 a is located between the adjacent segment magnets 43.

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

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

<Stator>
[Structure of stator]
As shown in FIGS. 1 and 2, the stator 100 surrounds the outer side of the rotor 40 in the radial direction. 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 part of the stator core 101. The insulator 102 is formed of an insulator such as an insulating resin and is attached to each tooth 105.

The coil 103 is configured by being wound around the teeth 105 of the stator core 101 via the insulator 102.

The stator core 101 has a plurality of electromagnetic steel plates laminated in the axial direction. The plurality of electromagnetic steel plates are fixed by caulking or the like. Note that the stator core may be composed of a single member. Further, the stator core 101 of the present embodiment is composed of a plurality of divided cores that can be divided in the circumferential direction. The stator core is not particularly limited, and may be constituted by a straight core, a round core, or the like.

As shown in FIGS. 2 and 4 to 6, the stator core 101 includes a core back 104, a tooth 105, and an umbrella 106. In the present embodiment, as shown in FIG. 6, the dimensions of the core back 104, the teeth 105, and the umbrella 106 are the same in the axial direction. The upper surface of the core back 104, the upper surface of the teeth 105, and the upper surface of the umbrella 106 are flush with each other. The lower surface of the core back 104, the lower surface of the teeth 105, and the lower surface of the umbrella 106 are flush with each other. The axial dimensions of the core back 104, the teeth 105, and the umbrella 106 may be different.

The core back 104 is annular. The core back 104 has a core back groove 104a that is recessed radially inward on the outer surface on the radially outer side. Each core back groove 104 a is located on the radially outer side 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. Note that the circumferential width of the teeth 105 of the present embodiment is constant, but may not be constant.

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

As shown in FIG. 4, the circumferential distance L <b> 1 between the adjacent teeth 105 (slot 107) at the radially inner end of the teeth 105 is larger than the circumferential width L <b> 2 of the teeth 105. Thereby, since the amount of interlinkage magnetic flux can be increased, the magnetic characteristics can be improved.

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

4 to 6, the umbrella 106 has at least a first bending portion 110, a second bending portion 120, and a third bending portion 130. In the present embodiment, the radially inner surface of the umbrella 106 includes only the first to third curved portions 110 to 130.

The first bending portion 110 is bent toward the inside in the radial direction. The 2nd bending part 120 and the 3rd bending part 130 are located in the both ends of the circumferential direction outer side of the 1st bending part 110, and curve toward the radial direction outer side. The inventor has focused on adjusting the shape of the magnetic flux according to the shape of the stator 100 using the segment magnet 43 that can reduce the manufacturing cost. As a result, the present inventor has found that the shape of the magnetic flux can be adjusted to a sine wave shape by the stator 100 including the umbrella 106 having the first to third curved portions 110 to 130. That is, since the magnetic flux distribution from the segment magnet 43 can be adjusted to a sine wave by the first to third curved portions 110 to 130 of the umbrella 106, the magnetic characteristics can be maintained.

Specifically, the first bending portion 110 is located at the center of the umbrella 106 in the circumferential direction. The first curved portion 110 is a curved surface that protrudes radially inward on the radially inner surface of the umbrella 106. The first bending portion 110 is a surface defined by the curvature R1. The first bending portion 110 extends in the axial direction on the radially inner surface of the umbrella 106. When viewed from the axial direction, the outer shape of the first bending portion 110 is a curve.

The second bending portion 120 is located on one side in the circumferential direction of the first bending portion 110. The third bending portion 130 is located on the other circumferential side of the first bending portion 110. The first to third bending portions 110 to 130 are continuous.

The second and third

curved portions

120 and 130 are located at the end of the umbrella 106. The second and third

curved portions

120 and 130 are curved surfaces that are convex toward the radially outer side on the radially inner surface of the umbrella 106. The second and third

curved portions

120 and 130 are surfaces defined by the curvatures R2 and R3. The second and third

curved portions

120 and 130 extend in the axial direction on the radially inner surface of the umbrella 106. When viewed from the axial direction, the outer shapes of the second and

third bending portions

120 and 130 are curved.

As shown in FIG. 5, the curvature R1 of the first bending portion 110 is different from the curvatures R2 and R3 of the second and

third bending portions

120 and 130. Thereby, since magnetic flux distribution can be easily adjusted to a sine wave shape, magnetic characteristics can be maintained more. The curvature R1 of the first bending portion 110 is larger than the curvatures R2, R3 of the second and

third bending portions

120, 130. Thereby, since magnetic flux distribution can be adjusted more easily by a sine wave shape, a magnetic characteristic can be maintained further. Note that the curvature R2 of the second bending portion 120 and the curvature R3 of the third bending portion 130 may be the same or different.

Further, the curvature R4 of the outer surface portion 43c of the segment magnet 43 shown in FIG. 3 is larger than the curvature R1 of the first bending portion 110 shown in FIG.

As shown in FIGS. 4 to 6, the second and

third bending portions

120 and 130 are different from the teeth 105 in the circumferential direction, and thus do not overlap in the circumferential direction. Specifically, the second and

third bending portions

120 and 130 are positioned on the outer side in the circumferential direction than the teeth 105. That is, the inflection point between the first bending portion 110 and the second bending portion 120 and the inflection point between the first bending portion 110 and the third bending portion 130 are located on the outer side in the circumferential direction than the teeth 105. Thereby, since magnetic flux distribution can be adjusted easily with a sine wave shape, magnetic characteristics can be maintained more.

As shown in FIG. 4, the circumferential distance L110 at the radially inner end of the first bending portion 110 is greater than the circumferential distances L120 and L130 at the radially inner ends of the second and

third bending portions

120, 130. ,large.

The circumferential distances L120 and L130 of the second and third

curved portions

120 and 130 are larger or the same as the circumferential gap between the adjacent umbrellas 106. Stator 100 of the present embodiment is a so-called slot open.

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

Also, the radial thickness L4 of the umbrella 106 is greater than or equal to the radial thickness L5 of the segment magnet 43. By increasing the thickness L4 of the umbrella 106, the magnetic flux can be effectively utilized, so that the magnetic characteristics can be improved. By reducing the thickness L5 of the segment magnet 43, the amount of material used for forming the magnet can be reduced, and thus the manufacturing cost can be reduced.

The maximum width in the circumferential direction of the umbrella 106 and the maximum width in the circumferential direction of the segment magnet 43 are the same.

Further, the width of the gap 108 is smaller than the minimum radial width between the umbrella 106 and the segment magnet 43.

Here, in the present embodiment, the umbrella 106 having the first to third curved portions 110 to 130 on the radially inner surface has been described as an example. The umbrella of the present invention may have another curved portion, a straight portion, etc. in addition to the first to third curved portions 110 to 130. In this case, another bending portion, a straight portion, or the like is disposed between the first bending portion 110 and the second and

third bending portions

120 and 130. Further, the first to third bending portions 110 to 130 may be provided with protrusions, grooves, and the like.

(Electric power steering device)
With reference to FIG. 7, the example which mounted the motor 1 mentioned above in the electric power steering apparatus 500 is demonstrated.

Vehicles such as automobiles are generally equipped with an electric power steering device. The electric power steering apparatus generates an auxiliary torque for assisting a steering torque of a steering system that is generated when a driver operates a steering handle. The auxiliary torque is generated by the auxiliary torque mechanism, and the burden on the operation of the driver can be reduced. For example, the auxiliary torque mechanism includes a steering torque sensor, an ECU, a motor, a speed reduction mechanism, and the like. The steering torque sensor detects steering torque in the steering system. The ECU generates a drive signal based on the detection signal of the steering torque sensor. The motor generates auxiliary torque corresponding to the steering torque based on the drive signal, and transmits the auxiliary torque to the steering system via the speed reduction mechanism.

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

The steering system 520 is, for example, a steering handle 521, a steering shaft 522 (also referred to as “steering column”),

universal shaft joints

523A, 523B, and a rotating shaft 524 (also referred to as “pinion shaft” or “input shaft”). ), A rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B,

tie rods

527A and 527B,

knuckle

528A and 528B, and left and right steering wheels (for example, left and right front wheels) 529A and 529B. The steering handle 521 is connected to the rotating shaft 524 via a steering shaft 522 and

universal shaft joints

523A and 523B. A rack shaft 526 is connected to the rotation shaft 524 via a rack and pinion mechanism 525. The rack and pinion mechanism 525 includes a pinion 531 provided on the rotation shaft 524 and a rack 532 provided on the rack shaft 526. The right steering wheel 529A is connected to the 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, the left steering wheel 529B is connected to the left end of the rack shaft 526 via 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 as viewed from the driver sitting on the seat, respectively.

According to the steering system 520, a steering torque is generated when the driver operates the steering handle 521, and is transmitted to the left and

right steering wheels

529A and 529B via the rack and pinion mechanism 525. Accordingly, the driver can operate the left and

right steering wheels

529A and 529B.

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU 542, a motor 543, a speed reduction mechanism 544, and a power conversion device 545. The motor 543 corresponds to the motor 1 described above.

The auxiliary torque mechanism 540 gives auxiliary torque to the steering system 520 from the steering handle 521 to the left and

right steering wheels

529A and 529B. The auxiliary torque may be referred to as “additional torque”.

The steering torque sensor 541 detects the steering torque of the steering system 520 applied by the steering handle 521. The ECU 542 generates a drive signal for driving the motor 543 based on a detection signal from the steering torque sensor 541 (hereinafter referred to as “torque signal”). The motor 543 generates an auxiliary torque corresponding to the steering torque based on the drive signal. The auxiliary torque is transmitted to the rotating shaft 524 of the steering system 520 via the speed reduction mechanism 544. The speed reduction mechanism 544 is, for example, a worm gear mechanism. The auxiliary 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 depending on a location where the 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 ECU 542 can receive not only a torque signal but also a vehicle speed signal, for example. The external device 560 is a vehicle speed sensor, for example. Alternatively, the external device 560 may be another ECU that can communicate through an in-vehicle network such as CAN (Controller AreaＡNetwork). The microcontroller of the ECU 542 can perform vector control or PWM control of the motor 543 based on a torque signal, a vehicle speed signal, or the like.

ECU 542 sets a target current value based on at least the torque signal. The ECU 542 preferably sets the target current value in consideration of the vehicle speed signal detected by the vehicle speed sensor and the rotor rotation signal detected by the angle sensor. The ECU 542 can control the drive signal of the motor 543, that is, the drive current 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 steering wheels

529A and 529B can be operated by the rack shaft 526 using the combined 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 described above, the electric power steering apparatus 500 can reduce the manufacturing cost while maintaining the magnetic characteristics.

In addition, although the electric power steering apparatus 500 was mentioned here as an example of the usage method of the motor 1, the usage method of the motor 1 is not limited. The motor of the present invention can be widely used in various devices including various motors such as a vacuum cleaner, a dryer, a ceiling fan, a washing machine, a refrigerator, and an electric power steering device.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1,543 motor, 10 housing, 11 bottom part, 21, 22 bearing, 30 bearing holder, 40 rotor, 41 rotor core, 41a rotor core groove, 41b shaft through hole, 42 shaft, 43 segment magnet, 43a inner surface part, 43b side part, 43c outer surface portion, 100 stator, 101 stator core, 102 insulator, 103 coil, 104 core back, 104a core back groove, 105 teeth, 106 umbrella, 107 slot, 108 gap, 110 first bending portion, 120 second bending portion, 130 3rd bending part, 500 Electric power steering device, 520 Steering system, 521 Steering handle, 522 Steering shaft, 523A, 523B Shaft coupling, 524 rotation shaft, 525 rack and pinion mechanism, 526 rack shaft, 527A, 527B tie rod, 528A, 528B knuckle, 529A, 529B: steering wheel, 531 pinion, 532 rack, 540 auxiliary torque mechanism, 541 steering torque sensor, 542 ECU, 544 deceleration mechanism, 545 power conversion device, 552A, 552B ball joint, 560 external device, A, central axis, L1, L110, L120, L130 distance, L2, L3 width, LL4, L5 thickness, R1, R2, R3, R4 curvature.

Claims

The rotor,
A stator surrounding a radially outer side of the rotor;
With
The rotor is
An axially extending shaft;
A rotor core attached to the shaft;
A plurality of segment magnets attached in the circumferential direction on the outer surface of the rotor core;
Including
The outer surfaces of the plurality of segment magnets form one circular arc,
The stator is
An annular core back,
A plurality of teeth extending radially inward from the core back;
A plurality of umbrellas facing the rotor and connected to the radially inner ends of the teeth and extending on both sides in the circumferential direction,
Including
The umbrella is
A first bending portion that curves inward in the radial direction;
Second and third curved portions located at both ends of the first curved portion in the circumferential direction and curved toward the radially outer side;
Having at least a motor.
The umbrella is composed only of the first to third curved portions,
2. The motor according to claim 1, wherein a curvature of the first bending portion is different from a curvature of the second and third bending portions.
The motor according to claim 2, wherein the curvature of the first bending portion is larger than the curvatures of the second and third bending portions.
The motor according to any one of claims 1 to 3, wherein a circumferential distance between adjacent teeth at a radially inner end of the teeth is larger than a circumferential width of the teeth.
The motor according to any one of claims 1 to 4, wherein in the radially outer end region of the umbrella, the circumferential width of the umbrella decreases toward the radially outer side.
The motor according to any one of claims 1 to 5, wherein a thickness of the umbrella in a radial direction is greater than or equal to a thickness of the segment magnet in a radial direction.
The stator includes twelve slots between the teeth;
The motor according to any one of claims 1 to 6, wherein the rotor includes eight segment magnets.
The motor according to any one of claims 1 to 7, wherein the second and third curved portions are positioned on the outer side in the circumferential direction than the teeth.
An electric power steering apparatus comprising the motor according to any one of claims 1 to 8.