JP2009027768A - Permanent magnet synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet synchronous motor which reduces cogging torque without increasing the number of components. <P>SOLUTION: In the permanent magnet synchronous motor, the rotor 20 comprises: a rotor core 21 made of a magnetic material; a permanent magnet 25 provided on the rotor core 21; and a rotor cover 27 abutting against the end face 21a collar 30 of the rotor core 21. Since the rotor cover 27 is formed of a magnetic material, leakage flux of each permanent magnet 25 is guided by the rotor cover 27 and cogging torque of the rotor 20 is reduced by reducing the density of flux of the permanent magnet 25 guided by the stator 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement for reducing the cogging torque of a permanent magnet synchronous motor.

  In the permanent magnet synchronous motor, the attractive force and the repulsive force between the permanent magnet and the stator increase or decrease in accordance with the rotational position of the rotor, so that cogging torque that periodically varies the rotational torque of the rotor is generated.

Conventionally, as a permanent magnet synchronous motor for reducing cogging torque, the one disclosed in Patent Document 1 is a reinforcement configured by alternately arranging an arc-shaped magnetic plate material and a non-magnetic material in the circumferential direction on the outer periphery of a rotor. A magnetic leakage ring made of a magnetic material is detachably disposed at the end of the reinforcing member, and the cogging torque is generated by moving the magnetic leakage ring to and from the reinforcing member according to the rotational speed of the rotor. It comes to reduce.
JP 2006-6023 A

  However, in such a conventional permanent magnet synchronous motor, it is necessary to provide a magnetic leakage ring and a drive mechanism for moving the magnetic leakage ring, which increases the number of parts constituting the motor, There was a problem of causing an increase in size.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a permanent magnet synchronous motor that reduces cogging torque without increasing the number of parts.

  The present invention is a permanent magnet synchronous motor that includes a stator provided with a plurality of coils and a rotor provided with a plurality of permanent magnets, and in which energization of each coil is controlled according to the rotational position of the rotor. Comprises a rotor core made of a magnetic material, a permanent magnet provided on the rotor core, and a rotor cover in contact with an end surface of the rotor core, and the rotor cover is formed of a magnetic material.

  According to the present invention, since the rotor cover is formed of a magnetic material, the leakage magnetic flux of each permanent magnet is guided by the rotor cover, and the magnetic flux density of the permanent magnet guided by the stator is reduced. Thereby, the cogging torque of the rotor is reduced, and the rotation operation of the motor is smoothly performed.

  Since this is realized by changing the material of the rotor cover from a non-magnetic material to a magnetic material, an increase in the size of the motor can be avoided without increasing the number of parts.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, a permanent magnet synchronous motor includes a motor case (housing) 1, a cover 2, and a shaft that is rotatably supported by the motor case 1 and the cover 2 via a pair of bearings 4 and 5. (Rotary shaft) 3, a rotor (rotor) 20 fixed to the shaft 3, and a stator (stator) 10 fixed to the motor case 1 so as to surround the rotor 20.

  The stator 10 includes a stator core 15 that constitutes a magnetic circuit, and a coil 13 that generates electromagnetic force.

  The stator core 15 is made of a magnetic material and is formed by stacking steel plates.

  As shown in FIG. 2, the stator core 15 includes a yoke 17 that extends in a cylindrical shape and is divided into nine pieces, and a tooth 16 that protrudes inward from the yoke 17.

  The tip surface of each tooth 16 is formed in a cylindrical shape, and faces each other with a gap 9 on the outer periphery of the rotor 20.

  The coil 13 is formed by winding a wire around each tooth 16. Each tooth 16 and each coil 13 constitutes nine magnetic poles. The number of magnetic poles is not limited to this and is arbitrarily set.

  As shown in FIG. 3, the rotor 20 corresponds to a rotor core 21 constituting a magnetic circuit, six permanent magnets 25 that generate magnetic force, both end faces 21a of the rotor core 21, and both end faces 25a of the permanent magnet 25, respectively. A pair of rotor covers 27 in contact with each other.

  The rotor core 21 is made of a magnetic material and is formed by stacking steel plates.

  The rotor core 21 is formed in a columnar shape having an outer peripheral surface 21 b that faces the stator 10, and has a fitting hole 21 c that fits in the shaft 3 and six insertion holes 21 d in which the permanent magnets 25 are interposed.

  Each permanent magnet 25 is interposed in the rotor core 21 and arranged so that each magnetic flux extends in the radial direction of the rotor core 21.

  The permanent magnet 25 is formed in a flat plate shape and is inserted into the insertion hole 21 d of the rotor core 21. Thereby, the six permanent magnets 25 are arranged so as to constitute each side of the hexagon.

  The permanent magnet 25 is fixed to the rotor core 21 by having both end surfaces 25 a abut against the rotor covers 27. However, the present invention is not limited to this, and a spacer may be interposed between the end surface 25 a of the rotor core 21 and the rotor cover 27 and fixed.

  A pair of collars 30 are attached to the shaft 3 adjacent to the rotor covers 27, and the rotor covers 27 and the rotor core 21 are fixed to the shaft 3 via the collars 30.

  When the permanent magnet synchronous motor rotates, the energization of each coil 13 is controlled according to the rotational position of the rotor 20, and the stator 10 attracts and repels each permanent magnet 25 to rotate the rotor 20.

  In FIG. 4, the path of the magnetic flux generated from the permanent magnet 25 is indicated by arrows m and n. A magnetic field is generated in the rotational radius direction and the circumferential direction of the motor, and the permanent magnet 25 → the rotor core 21 → the gap 9 → the teeth 16. → York 17 → Teeth 16 → Gap 9 → Rotor core 21 → Permanent magnet 25 is guided in a loop shape.

  A cogging torque that periodically varies the rotational torque of the rotor 20 is generated by increasing or decreasing the attractive force and the repulsive force between the permanent magnets 25 and the stator 10 according to the rotational position of the rotor 20 during the rotation operation when no power is supplied. To do.

  In the conventional apparatus, since the rotor cover is formed of a nonmagnetic material, the attractive force between the rotor and the stator is increased, and the cogging torque of the rotor is increased.

  In response to this, in the present invention, each rotor cover 27 is formed of a magnetic material, and each rotor cover 27 guides the magnetic flux of each permanent magnet 25 leaking from the gap 9 between the rotor 20 and the stator 10 in the rotational radius direction of the motor. The cogging torque is reduced.

  FIG. 5 shows the leakage magnetic flux guided by each rotor cover 27 by arrows s and t. By forming the rotor cover 27 with a magnetic material, a part of the magnetic flux generated from the permanent magnet 25 is guided by the magnetic path of the permanent magnet 25 → the rotor core 21 → the gap 9 → the rotor cover 27 → the rotor core 21 → the permanent magnet 25. .

  Thus, the leakage flux (indicated by arrows s and t) of the permanent magnet 25 is guided by the rotor covers 27 arranged at both ends of the rotor 20, whereby the magnetic flux (indicated by arrows m and n) of the permanent magnet 25 guided by the stator 10. The density of the permanent magnet 25 and the stator 10 decreases. Thereby, the cogging torque of the rotor 20 is reduced, and the rotation operation of the motor is smoothly performed.

  Each rotor cover 27 is formed in a disc shape, and comes into contact with a fitting hole 27 c that fits into the shaft 3, a cylindrical outer peripheral surface 27 b, an end surface 21 a of the rotor core 21, and an end surface 25 a of the permanent magnet 25. Surface 27a.

  The outer shape of each rotor cover 27 is formed substantially equal to the outer shape of the rotor core 21, and the outer peripheral surface 27 b of the rotor cover 27 is continuous with the outer peripheral surface of the rotor core 21 without a step. As a result, the magnetic flux emitted from the outer peripheral surface of the rotor core 21 is encouraged to enter the outer peripheral surface 27b of the rotor cover 27, and the cogging torque of the rotor 20 is effectively suppressed.

  Not limited to this, the shape of the rotor cover 27 may be different from the outer shape of the rotor 20 according to the characteristics of the cogging torque required for the motor.

  As described above, in the present embodiment, the stator 10 provided with the plurality of coils 13 and the rotor 20 provided with the plurality of permanent magnets 25 are provided, and energization of each coil 13 is controlled according to the rotational position of the rotor 20. The rotor 20 includes a rotor core 21 made of a magnetic material, a permanent magnet 25 provided on the rotor core 21, and a rotor cover 27 that contacts the end surface 21 a collar 30 of the rotor core 21. Since the rotor cover 27 is formed of a magnetic material, the leakage flux of each permanent magnet 25 is guided by the rotor cover 27, thereby reducing the magnetic flux density of the permanent magnet 25 guided by the stator 10 and reducing the cogging torque of the rotor 20. The motor rotates smoothly when no current is applied.

  Since this is realized by changing the material of the rotor cover 27 from a non-magnetic material to a magnetic material, an increase in the size of the motor can be avoided without increasing the number of parts.

  In this embodiment, each permanent magnet 25 is inserted into the insertion hole 21d of the rotor core 21, and each permanent magnet 25 is applied to the IPM motor built in the rotor core 21, so that the cogging torque of the rotor 20 is effectively applied via the rotor cover 27. Can be reduced.

  As another embodiment, as shown in FIG. 6, the present invention may be applied to an SPM motor in which each permanent magnet 25 is attached to the outer periphery of the rotor core 21.

  The rotor core 21 provided in the SPM motor has a hexagonal cross-sectional shape, and six permanent magnets 25 are attached to the outer peripheral surface of the rotor core 21. The permanent magnet 25 has an outer peripheral surface 25e that is curved in an arc shape.

  The outer shape of each rotor cover 27 is formed substantially equal to the outer shape of the permanent magnet 25, and the outer peripheral surface 27 b of the rotor cover 27 is continuous with the outer peripheral surface of the permanent magnet 25 without a step. Thereby, it is promoted that the magnetic flux emitted from the outer peripheral surface of the permanent magnet 25 enters the outer peripheral surface 27b of the rotor cover 27, and the cogging torque of the rotor 20 is effectively suppressed.

  Also in this case, each rotor cover 27 is formed of a magnetic material, and each rotor cover 27 guides the magnetic flux of each permanent magnet 25 leaking from the gap between the rotor 20 and the stator 10 in the rotational radius direction of the motor so as to reduce the cogging torque. It has become.

  Since the present embodiment is applied to the SPM motor in which each permanent magnet 25 is attached to the outer periphery of the rotor core 21, the cogging torque of the rotor 20 can be effectively reduced via the rotor cover 27.

  The permanent magnet synchronous motor of the present invention is not limited to an electric motor that rotationally drives the rotor, but may be used as a generator that generates electric power by rotating the rotor.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

Sectional drawing of the motor which shows embodiment of this invention. The perspective view of a stator core similarly. The exploded perspective view of a rotor similarly. Sectional drawing of a motor similarly. Sectional drawing of a motor similarly. The disassembled perspective view of the rotor which shows other embodiment.

Explanation of symbols

9 Gap 10 Stator 13 Coil 20 Rotor 21 Rotor Core 25 Permanent Magnet 27 Rotor Cover

Claims (5)

A stator provided with a plurality of coils;
A rotor provided with a plurality of permanent magnets,
A permanent magnet synchronous motor in which energization of each coil is controlled according to the rotational position of the rotor,
The rotor is
A rotor core made of magnetic material;
A permanent magnet provided in the rotor core;
A rotor cover that contacts the end face of the rotor core;
A permanent magnet synchronous motor, wherein the rotor cover is formed of a magnetic material. Inserting each permanent magnet into the insertion hole of the rotor core;
The permanent magnet synchronous motor according to claim 1, wherein each permanent magnet is built in the rotor core.   The permanent magnet synchronous motor according to claim 2, wherein an outer shape of the rotor cover is substantially equal to an outer shape of the rotor.   The permanent magnet synchronous motor according to claim 1, wherein each permanent magnet is attached to an outer periphery of the rotor core.   The permanent magnet synchronous motor according to claim 4, wherein an outer shape of the rotor cover is substantially equal to an outer shape of the permanent magnet.

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