JP2005278268A - Permanent magnet type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet type motor which reduces a cogging torque as a cause of a vibration or a noise. <P>SOLUTION: In the permanent magnet type motor, the circumferential length of a permanent magnet 22 and the circumferential length of the tip end of teeth 12 are configured to be regulated so that θm+θt=160-190° is satisfied, when an angle formed between both ends of the permanent magnet 22 and a rotating center O of a rotor 20 and an angle formed between both ends of the tip end of the tees 12 and a rotating center O are the θm, the θt by electrical angles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a permanent magnet motor.

  Conventionally, a stator having a plurality of teeth provided with windings and a rotor having a plurality of permanent magnets opposed to the teeth with a predetermined gap therebetween. Thus, in the permanent magnet motor that drives the rotor to rotate, vibration and noise at no load caused by cogging torque (torque pulsation caused by magnetic attraction force between the permanent magnet and the teeth) have been problems. .

In addition, as a prior art which solves the said subject, it is wider than the circumferential direction length of a slot opening part (part which opposes a rotor in the space where a winding is given between adjacent teeth), and teeth front-end | tip part ( Permanent magnet motors are disclosed and proposed in which cogging torque is reduced by disposing permanent magnets at an interval narrower than the circumferential length of the portion of the teeth facing the rotor. Reference 1).
JP 2000-333391 A

  It is true that the permanent magnet motor having the above configuration can reduce the cogging torque as compared with the case where no countermeasure is taken.

  However, in the permanent magnet motor configured as described above, no consideration is given to the relationship between the circumferential length of the permanent magnet and the circumferential length of the tip of the teeth, and depending on the application, the cogging torque may not be sufficiently reduced. there were.

  In addition, as another conventional technique for solving the above problem, a method of narrowing the circumferential length of the slot opening portion as much as possible can be considered, but with such a configuration, it is difficult to perform winding work on the teeth. This is not a realistic solution because another problem arises that magnetic flux leakage between adjacent tooth tip portions increases.

  In view of the above problems, an object of the present invention is to provide a permanent magnet motor capable of reducing cogging torque that causes vibration and noise.

  In order to achieve the above object, a permanent magnet motor according to the present invention includes a stator having a plurality of teeth with windings and a plurality of permanent magnets facing the teeth with a predetermined gap therebetween. A permanent magnet motor configured to rotate the rotor by energizing the winding, and facing the rotor in the circumferential length of the permanent magnet and the teeth. The circumferential length of the tip portion is an angle formed by both ends of the permanent magnet and the rotation center of the rotor, and an angle formed by both ends of the tooth tip portion and the rotation center of the rotor. Are adjusted so that θm + θt = 160 to 190 °, where θm and θt are electrical angles.

  In the permanent magnet motor having the above-described configuration, the circumferential length of the permanent magnet and the circumferential length of the tooth tip are θm = 70 to 90 ° and θt = 80 to 100 °. Adjust it.

  The permanent magnet motor having the above-described configuration may be configured such that the ratio of the number of permanent magnets to the number of teeth is 2: 3.

  In the case of the permanent magnet type motor having the above configuration, the stress near the end of the permanent magnet where the magnetic flux changes rapidly with the rotation of the rotor cancels each other between adjacent permanent magnets, thereby reducing the cogging torque. Is possible.

  FIG. 1 is a cross-sectional view of a permanent magnet motor according to the present invention as viewed from the direction of the rotation axis. As shown in the figure, the permanent magnet type motor according to the present invention includes an inner rotation type motor having a stator 10 and a rotor 20 rotatably disposed inside the stator 10. It is.

  The stator 10 includes a stator core 11 formed by laminating electromagnetic steel plates, 18 teeth 12 disposed at equal intervals on the inner peripheral surface of the stator core 11, and windings applied to the teeth 12. Line 13. Note that the tip portion of the tooth 12 that faces the rotor 20 (hereinafter referred to as the teeth tip portion 12a) has a curvature larger than the outer diameter of the rotor 20 (for example, the tooth tip portion has a linear shape). To be formed. By adopting such a configuration, the gap separating the teeth 12 and the rotor 20 can be made non-uniform, so that the change in the magnetic attractive force acting between them can be smoothed to reduce the cogging torque. Is possible. Further, the stator core 11 and the teeth 12 may be integrally formed, or may be configured by combining divided parts in order to increase the space factor of the winding 13.

  The rotor 20 is disposed at equal intervals along the outer peripheral surface of the rotor core 21 so as to face the rotor core 21 formed by laminating electromagnetic steel plates and the tooth tip portion 12a with a predetermined gap therebetween. And 12 permanent magnets 22 embedded therein. The polarities of the permanent magnets 22 are N and S alternately adjacent to each other, and the magnetization strengths are substantially the same. In addition, although the structure which provided one permanent magnet 22 for every pole in this figure was illustrated, the structure of this invention is not limited to this, A plurality of permanent magnets 22 are provided for each pole. It doesn't matter.

  In the 12-pole 18-slot permanent magnet motor having the above-described configuration, a three-phase alternating current is applied to the winding 13 applied to the tooth 12, and an attractive force and a repulsive force generated between the permanent magnet 22 and the winding 13 ( Magnet torque) and the force that attracts the winding 13 to a portion of the rotor core 21 sandwiched between adjacent permanent magnets 22 and having a magnetic saliency (hereinafter referred to as a magnetic salient pole portion 21a). The rotor 20 is rotationally driven using both (reluctance torque).

  Next, the correlation between the circumferential length of the permanent magnet 22 and the circumferential length of the tooth tip portion 12a, which is a feature of the present invention, will be described in detail with reference to FIG. FIG. 2 is an enlarged view of a range indicated by a one-dot chain line A in FIG.

  As shown in the figure, in the permanent magnet motor according to the present invention, the circumferential length of the permanent magnet 22 and the circumferential length of the tooth tip portion 12a are both ends of the permanent magnet 22 (using a plurality of permanent magnets). In the case of forming one magnetic pole, the angle formed by both ends of the magnetic pole) and the rotation center O of the rotor 20 and the angle formed by both ends of the tooth tip portion 12a and the rotation center O are respectively set. When the electrical angle (phase angle when one period of the signal sine wave is expressed as 360 [°]) is θm and θt, θm + θt = 160 to 190 ° (near 1/2 period) is adjusted. ing.

  By adopting such a configuration, the interval at which the permanent magnets 22 are disposed is substantially the same as the circumferential length of the tooth tip portion 12a, so that the permanent magnetic flux rapidly changes as the rotor 20 rotates. As shown in FIGS. 3A to 3C, the stress in the vicinity of the end portion of the magnet 22 is canceled out between the adjacent permanent magnets 22, and the cogging torque can be reduced.

  FIG. 4 is a diagram showing the correlation between θm, θt and cogging torque. In addition, the magnitude | size of cogging torque is shown on the vertical axis | shaft of this figure, and the magnitude | size of (theta) m is shown on the horizontal axis. Further, as shown in the legend in the figure, the round marker, triangular marker, and square marker in this figure indicate the magnitude of cogging torque when θt is 100 °, 90 °, and 80 °, respectively. As is clear from this figure, the circumferential length of the permanent magnet 22 and the circumferential length of the tooth tip portion 12a are θm = 70 to 90 among θm and θt satisfying the relationship of θm + θt = 160 to 190 °. It can be seen that it is desirable to adjust the angle θ and θt to be 80 to 100 °.

  In addition, for the above-described 12 pole 18 slot permanent magnet motor, when the above-described conventional technique for determining the arrangement interval of the permanent magnet based on the circumferential lengths of the slot opening portion and the tooth tip portion is applied as it is, For example, when θt is 90 °, θm is limited to 90 to 150 °. That is, in the related art, the cogging torque can be reduced only to a minimum value in the vicinity of θm = 130 °.

  On the other hand, in the case of the permanent magnet motor according to the present invention, the cogging torque is adjusted by adjusting the circumferential lengths of the permanent magnet 22 and the tooth tip portion 12a so that θm = 80 ° and θt = 90 °. Can be reduced to smaller values.

  In addition, as shown in FIG. 2, the permanent magnet motor according to the present invention has a gap 23 where the rotor core 21 does not exist at both ends of the permanent magnet 22 in order to optimize the reluctance torque. Here, the size of the gap 23 is such that θp = 70 to 90 when the angle formed by both ends of the magnetic salient pole portion 21a excluding the gap 23 and the rotation center O is θp in electrical angle. It is desirable to adjust so that it becomes °.

  In the above embodiment, a permanent magnet motor (12 poles and 18 slots) in which the number ratio of the permanent magnets 22 to the teeth 12 is 2: 3 has been described as an example. The present invention is not limited to this, and the present invention can be widely applied to permanent magnet motors in which the number ratio between them is different from that described above.

  The present invention is a technique useful for reducing cogging torque of a permanent magnet motor, and is suitable for, for example, reducing vibration and noise when pushing an electric assist bicycle equipped with a permanent magnet motor as auxiliary drive means. is there.

These are sectional drawings at the time of seeing the permanent magnet type motor concerning the present invention from the direction of a rotation axis. These are the enlarged views of the range shown by the dashed-dotted line A in FIG. These are the schematic diagrams for demonstrating the cogging torque reduction mechanism. These are figures which show the correlation with (theta) m and (theta) t and a cogging torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stator 11 Stator iron core 12 Teeth 12a Teeth tip part 13 Winding 20 Rotor 21 Rotor iron core 22 Permanent magnet 23 Air gap part (magnetic salient pole adjustment part)
O Rotation center of rotor θm Angle formed by both ends and rotation center of permanent magnet θt Angle formed by both ends of tooth tip and rotation center θp Both ends and rotation center of magnetic salient pole part excluding gap And the angle formed by

Claims (3)

A stator having a plurality of teeth provided with windings, and a rotor having a plurality of permanent magnets facing the teeth with a predetermined gap therebetween, and energizing the windings. In the permanent magnet motor that drives the rotor to rotate,
The circumferential length of the permanent magnet and the circumferential length of the tip portion facing the rotor in the teeth are an angle formed by both ends of the permanent magnet and the rotation center of the rotor, and The angle formed between both ends of the tooth tip portion and the rotation center of the rotor is adjusted to be θm + θt = 160 to 190 °, where θm and θt are electrical angles, respectively. Permanent magnet motor.   The circumferential length of the permanent magnet and the circumferential length of the tip end portion of the teeth are adjusted to be θm = 70 to 90 ° and θt = 80 to 100 °. The permanent magnet motor according to 1.   The permanent magnet motor according to claim 1 or 2, wherein a ratio of the number of the permanent magnets to the number of the teeth is 2: 3.

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