JP2008295207A - Ring magnet, motor, and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ring magnet capable of reducing a cogging torque and a torque ripple, and to provide a motor and an electric power steering device. <P>SOLUTION: The ring magnet 20 includes a first magnetic pole region 21 magnetized to an N-pole and a second magnetic pole region 22 magnetized to an S-pole which are alternately formed in a circumferential direction. In the first magnetic pole region 21, a first reverse magnetic pole region 24 magnetized to the S-pole and the first magnetic pole region 21 are provided on a line along the center axis of the ring magnet 20 near boundary lines 23 with the second magnetic pole regions 22 on both sides. In the second magnetic pole region 22, a second reverse magnetic pole region 25 magnetized to the N-pole and the second magnetic pole region 22 are provided on a line along the center axis of the ring magnet 20 near the boundary lines 23 with the first magnetic pole regions 21 on both sides. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ring magnet, a motor, and an electric power steering device.

  In recent years, electric power steering devices (EPS) using a motor as a drive source have been widely adopted as vehicle power steering devices. By the way, the output torque of the motor varies due to cogging torque or torque ripple caused by distortion of the induced voltage waveform generated in the winding coil. Moreover, in EPS, such fluctuations in output torque are directly reflected in the steering feeling. For this reason, many countermeasures for reducing cogging torque and torque ripple have been proposed for motors used in EPS in order to improve the steering feeling.

For example, Patent Document 1 discloses a motor that uses a ring magnet having a substantially trapezoidal magnetic flux distribution in the circumferential direction by making the waveform of the magnetizing current trapezoidal, and reducing cogging torque and torque ripple. . Furthermore, in the ring magnet of Patent Document 1, each magnetic pole is inclined with respect to the central axis of the ring magnet, that is, skewed in the axial direction, thereby reducing a rapid change in magnetic flux between the rotor and the stator. Cogging torque and torque ripple are reduced.
JP 2004-242489 A

  By the way, in order to suppress the cogging torque and the torque ripple, it is desirable to magnetize the magnetic flux distribution in the circumferential direction of the ring magnet as a sine wave as shown by the broken line in FIG. However, it is difficult to control the magnetic flux distribution. In the conventional ring magnet, the magnetic flux distribution is limited to a trapezoid as shown by the solid line in FIG. Therefore, particularly in the vicinity of the boundary of the magnetic pole where the polarity is reversed, there is still a problem that the fluctuation in the output torque of the motor due to the cogging torque and the torque ripple cannot be suppressed, and the steering feeling during the low-speed steering of the EPS cannot be improved. It was.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a ring magnet, a motor, and an electric power steering device that can reduce cogging torque and torque ripple.

  In order to achieve the above object, the invention according to claim 1 is characterized in that the first magnetic pole region magnetized to the first polarity and the second polarity opposite to the first polarity are magnetized. A cylindrical ring magnet provided with a plurality of second magnetic pole regions alternately along the circumferential direction, in the first magnetic pole region, on at least one of the vicinity of the boundary with the second magnetic pole region. The first reverse magnetic pole region magnetized to the second polarity and the first magnetic pole region are provided on a line along the center axis of the ring magnet, and in the second magnetic pole region, In at least one of the vicinity of the boundary with the first magnetic pole region, the second reverse magnetic pole region magnetized to the first polarity and the second magnetic pole region are on a line along the central axis of the ring magnet. The gist of this is

  According to the above configuration, at least one of the first magnetic pole region in the vicinity of the boundary with the second magnetic pole region has the first reverse magnetic pole region and the first magnetic pole region magnetized to the second polarity. It is provided on a line along the center axis of the ring magnet, that is, a part of the region along the axial direction of the first magnetic pole region is provided as the first reverse magnetic pole region. Similarly, at least one of the second magnetic pole region in the vicinity of the boundary with the first magnetic pole region is provided with a second reverse magnetic pole region and a second magnetic pole region magnetized to the first polarity. It is provided on a line along the central axis, that is, a part of the region along the axial direction of the second magnetic pole region is provided as the second reverse magnetic pole region. Then, a magnetic flux in the direction opposite to the first magnetic pole region is generated in the range of the first reverse magnetic pole region provided in the first magnetic pole region, and the range of the second reverse magnetic pole region provided in the second magnetic pole region. , A magnetic flux in the direction opposite to that of the second magnetic pole region is generated. For this reason, when the magnetic flux of the ring magnet is integrated along the axial direction, the magnetic flux generated from the first and second reverse magnetic pole regions causes the circumferential position at which the first and second reverse magnetic pole regions are provided. The absolute value of the integral value decreases. That is, the integral value of the magnetic flux along the axial direction of the ring magnet 20 is controlled by changing the ratio of the first and second reverse magnetic pole regions in the first and second magnetic pole regions in the axial direction. . Therefore, by setting the ratio of the first and second reverse magnetic pole regions in the first and second magnetic pole regions in the axial direction to a suitable value in the vicinity of the boundary, the field magnetic flux formed by the ring magnet is reduced. A pseudo sine wave can be obtained.

  According to a second aspect of the present invention, in the ring magnet according to the first aspect, the first reverse magnetic pole region and the second reverse magnetic pole region are provided so as to be inclined with respect to a central axis of the ring magnet. The gist is that

  According to the above configuration, the second reverse magnetic pole region that is inclined with respect to the central axis of the ring magnet, that is, is skewed in the axial direction, has a second vicinity in the vicinity of the boundary between the first magnetic pole region and the second magnetic pole region. The first reverse magnetic pole region and the first magnetic pole region that are magnetized with the polarities are provided on a line along the center axis of the ring magnet. Similarly, the second reverse magnetic pole region magnetized to the first polarity in the vicinity of the boundary between the second magnetic pole region and the first magnetic pole region by the second reverse magnetic pole region skewed in the axial direction and the second reverse magnetic pole region Two magnetic pole regions are provided on a line along the center axis of the ring magnet. Therefore, by setting the skew angle and the widths (circumferential lengths) of the first and second reversed magnetic pole regions to suitable values, the field magnetic flux formed by the ring magnet approximates a sine wave shape. Therefore, the first and second reverse magnetic pole regions can be magnetized by a simple-shaped magnetizing yoke.

  The invention according to claim 3 is the ring magnet according to claim 1 or 2, wherein the first magnetic pole region and the second magnetic pole region are provided so as to be inclined with respect to a central axis of the ring magnet. The gist is that

  According to the above configuration, since the first magnetic pole region and the second magnetic pole region are provided by being skewed in the axial direction, the field magnetic flux formed only by the first and second magnetic pole regions is sinusoidal. To be close to. Therefore, even in the first and second reverse magnetic pole regions in a small region, the field magnetic flux formed by the ring magnet approximates a sine wave shape in a pseudo manner.

  The invention according to claim 4 is an armature in which a winding coil is wound around each of a plurality of teeth provided in an armature core, a first magnetic pole region magnetized to a first polarity, A motor including a plurality of second magnetic pole regions magnetized with a second polarity opposite to the first polarity along a circumferential direction and having a field magnet facing the armature; In the first magnetic pole region, at least one in the vicinity of the boundary with the second magnetic pole region, the first reverse magnetic pole region magnetized to the second polarity and the first magnetic pole region Is provided on a line along the central axis of the motor, and at least one of the second magnetic pole region in the vicinity of the boundary with the first magnetic pole region is magnetized with the first polarity. Two reverse magnetic pole regions and the second magnetic pole region are on a line along the central axis of the motor. It provided the gist of.

  According to the above configuration, since the field magnetic flux formed by the field magnet approaches a sine wave shape, an abrupt change in the amount of magnetic flux is suppressed in the vicinity of the boundary where the polarity is reversed, and the cogging torque of the motor is reduced. In addition, the induced voltage waveform generated in the winding coil is also sinusoidal, and torque ripple is reduced.

The invention according to claim 5 is the motor according to claim 4, wherein the field magnet is a cylindrical ring magnet having a plurality of magnetic poles in the circumferential direction.
According to the said structure, the work process and work time at the time of an assembly | attachment are reduced compared with the case where a some segment magnet is used for a field magnet.

The invention according to claim 6 is the motor according to claim 4, wherein the field magnet is a plurality of segment magnets arranged along a circumferential direction.
According to the above configuration, since there is a space between the segment magnets, the field magnetic flux formed only by the first and second magnetic pole regions can be approximated to a sine wave. Therefore, even if the ratio of the first and second reverse magnetic pole regions occupying the first and second magnetic pole regions in the axial direction is reduced, the field magnetic flux formed by the plurality of segment magnets has a pseudo sine wave shape. As a result, the first and second reverse magnetic pole regions can be reduced.

The gist of the seventh aspect of the invention is an electric power steering apparatus including the motor according to any one of the fourth to sixth aspects.
According to the above configuration, since the cogging torque and torque ripple of the motor are reduced, the operational feeling during low-speed steering of the electric power steering device is improved.

  According to the present invention, it is possible to provide a ring magnet, a motor, and an electric power steering device that can reduce cogging torque and torque ripple.

Hereinafter, an embodiment in which the present invention is embodied in a coaxial rack assist type electric power steering device will be described with reference to the drawings.
As shown in FIG. 1, the housing 2 of the EPS 1 is formed in a substantially cylindrical shape. In the housing 2, a pinion shaft 3 that is rotated by a steering operation, a rack shaft 4 that is meshed with the pinion shaft 3 and supported so as to reciprocate along the axial direction, and the rack shaft 4 are arranged coaxially. The motor 10 is provided. The rack shaft 4 is penetrated along the axial direction of the housing 2. One end of the pinion shaft 3 is connected to a steering wheel (not shown) via a steering shaft (not shown) or the like. Then, the pinion shaft 3 rotates in accordance with the steering operation, and the rotation is converted into the reciprocating motion of the rack shaft 4, whereby the steering angle of the steered wheels (not shown) is changed.

  Next, the configuration of the motor 10 will be described. In the present embodiment, the motor 10 is a rotating field motor (brushless motor) in which a field permanent magnet is provided on the rotor side.

  As shown in FIG. 2, the motor 10 includes a stator 11 fixed to the inner peripheral surface of the housing 2 and a hollow cylindrical motor shaft 12. A winding coil 15 is wound around each tooth 13 of the stator 11 via an insulator 14. A ring magnet 20 as a field magnet having a plurality of magnetic poles (10 poles in the present embodiment) in the circumferential direction is externally fitted on the outer peripheral surface of the motor shaft 12 so as to face the stator 11. As shown in FIG. 1, the motor shaft 12 is rotatably supported by the housing 2 by virtue of the shafts 16a and 16b that support both ends. A rotating magnetic field is formed around the motor shaft 12 (ring magnet 20) by the three-phase alternating current supplied to the winding coil 15. The motor shaft 12 rotates due to the relationship between the field magnetic flux formed by the ring magnet 20 and the rotating magnetic field of the stator 11.

  The EPS 1 includes a screw portion 17a formed on the outer periphery of the rack shaft 4, a nut portion 17b formed on the inner periphery of the motor shaft 12, and a plurality of steel balls 17c inserted between the screw portion 17a and the nut portion 17b. The ball screw mechanism 18 comprised by these is provided. Then, the ball screw mechanism 18 converts the rotation of the motor shaft 12 into the reciprocating motion of the rack shaft 4 and applies assist force to the steering system.

  Next, the ring magnet 20 will be described in detail. FIG. 3A is a development view of the outer peripheral surface of the ring magnet 20. For the sake of convenience, the polarity that appears on the outer peripheral surface of the ring magnet 20 is shown by hatching, and the same polarity appears in the region that is given the same hatching. Further, for convenience of explanation, the ring magnet 20 in which N poles and S poles are alternately provided will be described.

  The ring magnet 20 includes a first magnetic pole region 21 magnetized at the N pole as the first polarity and a second magnetic pole region 22 magnetized at the S pole as the second polarity in the circumferential direction. It is formed alternately along. In the first magnetic pole region 21, in the vicinity of the boundary line 23 with the second magnetic pole region 22 on both sides, the first reverse magnetic pole region 24 and the first magnetic pole magnetized to the S pole (second polarity). The region 21 is provided on a line along the central axis of the ring magnet 20. That is, the first magnetic pole region 21 is provided so that a part of the region along the axial direction becomes the first reverse magnetic pole region 24. Further, in the second magnetic pole region 22, in the vicinity of the boundary line 23 with the first magnetic pole region 21 on both sides, the second reverse magnetic pole region 25 and the second magnetic pole magnetized to the N pole (first polarity) are provided. Are provided on a line along the center axis of the ring magnet 20. That is, the second magnetic pole region 22 is provided so that a part of the region along the axial direction becomes the second reverse magnetic pole region 25.

  In the present embodiment, the ring magnet 20 is provided with a first magnetic pole region 21 and a second magnetic pole region 22 that are inclined with respect to the central axis of the ring magnet 20, that is, skewed in the axial direction. The first and second reverse magnetic pole regions 24 and 25 have a skew angle different from that of the first and second magnetic pole regions 21 and 22 and are linearly provided with the same width.

  In the present embodiment, the ring magnet 20 is formed by performing magnetization in two steps. Specifically, by the first magnetization, the first and second magnetic pole regions 21 and 22 are magnetized while being skewed in the axial direction as shown in FIG. Thereafter, by the second magnetization, as shown in FIG. 3A, the first and second reverse magnetic pole regions 24 and 25 are respectively formed in the vicinity of the boundary line 23 of the first and second magnetic pole regions 21 and 22. It is formed by being skewed in the axial direction and magnetized.

  In the magnetized ring magnet 20, the magnetic flux distribution along the circumferential direction changes as shown in FIG. 4A at the base end (lower side in FIG. 3A) of the ring magnet 20. . Specifically, in the first magnetic pole region 21, the first reverse magnetic pole region 24 is provided in the vicinity of the boundary line 23 with the second magnetic pole region 22. In this range, a magnetic flux in the direction opposite to that of the first magnetic pole region 21 is generated. Similarly, in the second magnetic pole region 22, since the second reverse magnetic pole region 25 is provided in the vicinity of the boundary line 23 with the first magnetic pole region 21, the range of each second reverse magnetic pole region 25. , A magnetic flux in the direction opposite to that of the second magnetic pole region 22 is generated.

  Further, at the tip of the ring magnet 20 (upper side in FIG. 3B), the magnetic flux distribution changes along the circumferential direction as shown in FIG. 4B. Specifically, similarly to the magnetic flux distribution at the proximal end of the ring magnet 20, the magnetic flux in the direction opposite to the first magnetic pole region 21 in the range of the first reverse magnetic pole region 24 provided in the first magnetic pole region 21. Will occur. In addition, a magnetic flux in the direction opposite to that of the second magnetic pole region 22 is generated in the range of the second reverse magnetic pole region 25 provided in the second magnetic pole region 22.

  Therefore, when the magnetic flux of the ring magnet 20 is integrated along the axial direction, the first and second reverse magnetic fluxes are generated by the magnetic flux generated from the first and second reverse magnetic pole regions 24 and 25 provided in the vicinity of the boundary line 23. The absolute value of the integrated value decreases at the circumferential position where the magnetic pole regions 24 and 25 are provided.

  The first and second reverse magnetic pole regions 24 and 25 have a skew angle different from that of the first and second magnetic pole regions 21 and 22 and are linearly provided with the same width. A part of the region along the axial direction of the two magnetic pole regions 21 and 22 is provided to be the first and second reverse magnetic pole regions 24 and 25. That is, by changing the skew angle and the widths (circumferential lengths) of the first and second reverse magnetic pole regions 24 and 25, the first and second magnetic pole regions 21 and 22 in the axial direction occupy the first. And the ratio of the 2nd reverse magnetic pole area | regions 24 and 25 is changed, and the integral value of the magnetic flux along the axial direction of the ring magnet 20 is controlled. Therefore, by setting the skew angle and the widths of the first and second reverse magnetic pole regions 24 and 25 to suitable values, the magnetic flux distribution shown by the broken line from the magnetic flux distribution shown by the solid line in FIG. The formed field magnetic flux is approximated to a sine wave shape.

As described above, according to the present embodiment, the following operations and effects are achieved.
(1) In the ring magnet 20, the first magnetic pole regions 21 magnetized to the N pole and the second magnetic pole regions 22 magnetized to the S pole are alternately formed along the circumferential direction. In the first magnetic pole region 21, in the vicinity of the boundary line 23 with the second magnetic pole region 22 on both sides, the first reverse magnetic pole region 24 and the first magnetic pole region 21 magnetized to the S pole are provided with the ring magnet 20. It was provided on a line along the central axis. Further, in the second magnetic pole region 22, in the vicinity of the boundary line 23 with the first magnetic pole region 21 on both sides, the second reverse magnetic pole region 25 and the second magnetic pole region 22 magnetized to the N pole are ringed. It was provided on a line along the center line of the magnet 20. Therefore, a magnetic flux in the direction opposite to that of the first magnetic pole region 21 is generated in the range of the first reverse magnetic pole region 24 provided in the first magnetic pole region 21, and the second magnetic pole region 22 provided in the second magnetic pole region 22 A magnetic flux in the direction opposite to that of the second magnetic pole region 22 is generated in the range of the reverse magnetic pole region 25. When the magnetic flux of the ring magnet 20 is integrated along the axial direction, the first and second reverse magnetic poles are generated by the magnetic flux generated from the first and second reverse magnetic pole regions 24 and 25 provided in the vicinity of the boundary line 23. At the circumferential position where the regions 24 and 25 are provided, the absolute value of the integral value is decreased. That is, the magnetic flux along the axial direction of the ring magnet 20 is changed by changing the ratio of the first and second reverse magnetic pole regions 24 and 25 in the first and second magnetic pole regions 21 and 22 in the axial direction. The integral value can be controlled. Therefore, by setting the ratio of the first and second reverse magnetic pole regions 24 and 25 in the first and second magnetic pole regions 21 and 22 to a suitable value, the magnetic flux distribution indicated by the solid line in FIG. The magnetic flux distribution as shown, that is, the field magnetic flux formed by the ring magnet 20 can be approximated to a sinusoidal shape.

  (2) The first reverse magnetic pole region 24 and the first magnetic pole region in the vicinity of the boundary line 23 between the first magnetic pole region 21 and the second magnetic pole region 22 by the first reverse magnetic pole region 24 skewed in the axial direction. The region 21 is provided on a line along the central axis of the ring magnet 20. Similarly, the second reverse magnetic pole region 25 and the second magnetic pole in the vicinity of the boundary line 23 with the first magnetic pole region 21 in the second magnetic pole region 22 by the second reverse magnetic pole region 25 skewed in the axial direction. The region 22 is provided on a line along the center axis of the ring magnet 20. Therefore, by setting the skew angle and the widths (circumferential lengths) of the first and second reverse magnetic pole regions 24 and 25 to suitable values, the field magnetic flux formed by the ring magnet 20 is pseudo-sine-wave shaped. Get closer to. Therefore, the first and second reverse magnetic pole regions can be magnetized by a simple-shaped magnetizing yoke.

  (3) Since the first and second magnetic pole regions 21 and 22 are skewed in the axial direction, the field magnetic flux formed only by the first and second magnetic pole regions 21 and 22 is sinusoidal. Get closer. Therefore, even in the first and second reversed magnetic pole regions 24 and 25 in a small region, the field magnetic flux formed by the ring magnet 20 becomes closer to a sine wave shape in a pseudo manner, and the first and second reversed magnetic poles. The areas 24 and 25 can be reduced.

  (4) Since the field magnetic flux formed by the ring magnet 20 approaches a sine wave shape, a sudden change in the amount of magnetic flux is suppressed in the vicinity of the boundary line 23 where the polarity is reversed, and the cogging torque of the motor 10 can be reduced. Further, the induced voltage waveform generated in the winding coil 15 is also sinusoidal, and torque ripple can be reduced.

(5) Since the ring magnet 20 is used as the field magnet, the work process and work time during assembly can be reduced compared to the case where a plurality of segment magnets are used as the field magnet.
(6) Since the cogging torque and torque ripple of the motor 10 are reduced, the operational feeling during low-speed steering of the EPS 1 can be improved.

In addition, you may implement this Embodiment in the following aspects.
In the present embodiment, the first and second magnetic pole regions 21 and 22 are provided by being skewed in the axial direction. However, the present invention is not limited to this, and as shown in FIG. Two magnetic pole regions 31 and 32 may be provided in parallel to the central axis of the ring magnet 20. That is, even if the first and second reverse magnetic pole regions 24 and 25 are provided in the ring magnet 30 in which the first magnetic pole region 31 and the second magnetic pole region 32 are alternately provided at equal intervals in parallel with the axis. Good. Moreover, although the 1st and 2nd reverse magnetic pole area | regions 24 and 25 were provided in the same width linear form, you may make it curved form, for example, not only this but S shape. Moreover, it does not need to have the same width along the axial direction.

  In the present embodiment, the first and second reverse magnetic pole regions 24 and 25 are continuously provided from the proximal end to the distal end of the ring magnet 20, but the present invention is not limited to this, as shown in FIG. The axial lengths of the first and second reverse magnetic pole regions 44 and 45 may be shorter than the axial length of the ring magnet 40. Further, the first and second reverse magnetic pole regions 44 and 45 are not limited to a rectangular shape, and may be, for example, a circular shape or a triangular shape. Furthermore, the first and second reverse magnetic pole regions 44 and 45 may be provided so as to be discontinuous.

  -In this embodiment, although the ring magnet 20 was used for the outer peripheral surface of the motor shaft 12, you may use not only this but a segment magnet. Specifically, the magnets are pasted so that the N pole and the S pole are alternately arranged along the circumferential direction of the motor shaft 12, and the respective magnetic poles are attached to both circumferential ends of the magnets (boundary boundaries of the magnetic poles). You may provide the 1st reverse magnetic pole area | region 24 and the 2nd reverse magnetic pole area | region 25 of reverse polarity. By using the segment magnets, the field magnetic flux formed only by the first and second magnetic pole regions can be made closer to a sine wave shape by the space between the segment magnets. Therefore, even if it is the 1st and 2nd reverse magnetic pole area | region of a small area | region, the field magnetic flux formed of a several segment magnet approximates more sinusoidally, and the 1st and 2nd reverse magnetic pole area | region Can be reduced.

  In the present embodiment, in the first magnetic pole region 21, the first reverse magnetic pole region 24 is provided in the vicinity of the boundary line 23 with the second magnetic pole region 22 on both sides, and in the second magnetic pole region 22, Although the second reverse magnetic pole region 25 is provided in the vicinity of the boundary line 23 with the first magnetic pole region 21, it may be provided only in the vicinity of one of the boundary lines 23.

In the present embodiment, the present invention is embodied in a rotary field type motor, but is not limited thereto, and may be embodied in a rotary armature type motor (DC motor).
The present invention may be embodied not only in a motor but also in other rotating electrical machines such as a generator (including a motor having a power generation function), and more specifically in an outer rotor type rotating electrical machine as well as an inner rotor type. May be used.

  In the present embodiment, the present invention is embodied in the coaxial rack assist type EPS 1 in which the motor 10 (motor shaft 12) itself is disposed coaxially with the rack shaft 4, but a so-called rack cross type or the like is provided outside the housing. The motor may be embodied in an EPS that drives a hollow shaft through which a rack shaft is inserted.

Sectional drawing of an electric power steering device. AA sectional view taken on the line AA of FIG. (A) (b) The development view of a ring magnet. (A) (b) The wave form diagram which shows magnetic flux distribution in the circumferential direction of a ring magnet. (A) (b) The development view of another ring magnet. The wave form diagram which shows magnetic flux distribution in the circumferential direction of the conventional ring magnet.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 10 ... Motor, 13 ... Teeth, 15 ... Winding coil, 20, 30, 40 ... Ring magnet, 21, 31 ... 1st magnetic pole area | region, 22, 32 ... 2nd Magnetic pole area, 23 ... boundary line, 24, 44 ... first reverse magnetic pole area, 25, 45 ... second reverse magnetic pole area.

Claims (7)

A plurality of first magnetic pole regions magnetized to the first polarity and second magnetic pole regions magnetized to the second polarity opposite to the first polarity are alternately arranged along the circumferential direction. A cylindrical ring magnet provided,
In the first magnetic pole region, at least one in the vicinity of the boundary with the second magnetic pole region, the first reverse magnetic pole region and the first magnetic pole region magnetized to the second polarity are Provided on a line along the center axis of the ring magnet,
In the second magnetic pole region, at least one in the vicinity of the boundary with the first magnetic pole region, the second reverse magnetic pole region and the second magnetic pole region magnetized to the first polarity are A ring magnet provided on a line along a central axis of the ring magnet.   The ring magnet according to claim 1, wherein the first reverse magnetic pole region and the second reverse magnetic pole region are provided so as to be inclined with respect to a central axis of the ring magnet.   The ring magnet according to claim 1, wherein the first magnetic pole region and the second magnetic pole region are provided so as to be inclined with respect to a central axis of the ring magnet. An armature in which a winding coil is wound around each of a plurality of teeth provided in an armature core;
A plurality of first magnetic pole regions magnetized to the first polarity and second magnetic pole regions magnetized to the second polarity opposite to the first polarity are alternately arranged along the circumferential direction. A motor provided with a field magnet facing the armature,
In the first magnetic pole region, at least one in the vicinity of the boundary with the second magnetic pole region, the first reverse magnetic pole region and the first magnetic pole region magnetized to the second polarity are Provided on a line along the central axis of the motor,
In the second magnetic pole region, at least one in the vicinity of the boundary with the first magnetic pole region, the second reverse magnetic pole region and the second magnetic pole region magnetized to the first polarity are A motor provided on a line along a central axis of the motor.   The motor according to claim 4, wherein the field magnet is a cylindrical ring magnet having a plurality of magnetic poles in the circumferential direction.   The motor according to claim 4, wherein the field magnet is a plurality of segment magnets arranged along a circumferential direction.   An electric power steering apparatus comprising the motor according to any one of claims 4 to 6.

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