JP2018143079A - IPM motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an IPM motor capable of maintaining motor characteristics by improving a cogging torque without increasing costs and reducing assembly workability.SOLUTION: In a rotational core 5, a plurality of curve surface parts 5a projecting in a radial direction which serve as a magnetic flux action surface and concave surface parts 5b that separate the curve surface parts 5a from one another are alternately formed. The concave grooves 5d are provided in the curve surface parts 5a, respectively.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an IPM (Interior Permanent Magnet) motor used for, for example, an in-vehicle sensorless motor.

  For example, a 4-pole 6-slot IPM motor shown in FIG. 5 includes a stator 51 and a rotor 52. The stator 51 includes a stator core 53 including a tooth 53a and a core back 53b, and a concentrated winding coil winding 55 (three-phase winding of a three-phase winding) wound around the tooth 53a in a slot 54 between the teeth 53a. (U phase, V phase, W phase).

  Since the IPM motor shown in FIG. 5 has 4 poles and 6 slots, the slot pitch is 120 degrees in electrical angle. The rotor 52 includes a shaft hole 56 b for fitting a permanent magnet 57 into a single-letter permanent magnet insertion hole 56 a formed in the rotor core 56, and fitting with the rotor shaft 58. On the rotor core 56, magnetic poles 56c serving as magnetic pole action surfaces (curved surface portions) are projected at four locations. A concave portion 56d is formed between the magnetic poles 56c.

  Since the IPM motor has a high magnetic flux density, the cogging torque also increases. However, in order to reduce the cogging torque, it is proposed that the magnetic pole 56c is formed asymmetrically with respect to the radial axis with respect to the radial axis. Patent Document 1).

JP 2004-48912 A

  In general, in order to smoothly rotate an IPM motor, a technical idea intended to reduce cogging torque is proposed as in Patent Document 1, but a technical idea intended to increase cogging torque. Has not been proposed. On the other hand, when there is a need to stop the rotor without moving due to vibration or the like at the rotation stop position, it is necessary to improve the cogging torque (holding torque). In order to realize this, it is conceivable to use a material having a high magnetic grade of the rotor magnet (for example, neodymium) or to increase the interval between the open slots of the stator core. However, the higher grade of magnet material increases the manufacturing cost, and if the interval between the open slots of the stator core is increased, the space for winding the magnet wire is reduced and the motor characteristics are deteriorated.

  The present invention has been made to solve these problems, and an object of the present invention is to provide an IPM motor capable of maintaining the motor characteristics by improving the cogging torque without increasing the cost and reducing the assembly workability. There is.

In order to achieve the above object, the present invention comprises the following arrangement.
A radial gap type IPM motor in which a rotor magnetic pole in which a plurality of permanent magnets are embedded in a rotor core is arranged to face a stator pole tooth, and a magnetic flux action is applied to the rotor magnetic pole or the stator pole tooth. A plurality of curved surface portions projecting in a radial direction to be a surface and concave surface portions partitioning each curved surface portion are alternately formed, and each curved surface portion is provided with a concave groove. .
As a result, the cogging torque increases because the change in the magnetic field between the opposing magnetic pole surfaces increases due to the concave grooves provided in the curved surface portions of the rotor magnetic poles or the stator pole teeth.
Therefore, the rotor does not rotate due to vibration or the like when stationary, and the number of turns of the coil does not decrease, so that the motor characteristics can be maintained.

Ζ = 2i * π, where ζ is the center angle formed by the centers of adjacent concave grooves provided on the rotor magnetic pole or the stator pole teeth, i is an integer, T is the cogging period, and p is the number of rotor pole pairs. It is desirable that the concave grooves are alternately provided through the convex surface portions for the curved surface portions at intervals of the central angle ζ calculated by / T * p.
As a result, the convex surface portions and the concave grooves are alternately formed at predetermined intervals at the optimal positions of the respective curved surface portions of the rotor magnetic pole or the stator pole teeth, and the cogging torque can be increased between the opposing magnetic poles. .

Permanent magnets are inserted into the magnet insertion holes provided on the radially inner side of the curved surface portions protruding from the outer peripheral surface of the rotor core of the inner rotor type motor, and the curved surface portions are partitioned by the concave grooves. The convex surface portions may be formed at a predetermined interval.
As a result, in the inner rotor type motor, the change in the magnetic field between the curved surface portion of the rotor magnetic pole and the stator pole teeth facing it increases, so that the cogging torque increases.

  If the IPM motor described above is used, the cogging torque can be improved without increasing the cost and the assembling workability, and the motor characteristics can be maintained.

It is a top view in the axial direction of a 4-pole 6-slot inner rotor type DC brushless motor. It is the top view and axial sectional view which abbreviate | omitted the coil of FIG. It is explanatory drawing which shows an example of the ditch | groove provided in a rotor magnetic pole, and explanatory drawing which shows the rotation state of a rotor. It is the graph which compared the detent torque magnitude | size according to the presence or absence of a ditch | groove (auxiliary groove) in a rotor. FIG. 6 is a layout diagram of a rotor and a stator when the cogging torque of a conventional 4-pole 6-slot motor is reduced.

  Embodiments of an IPM motor according to the present invention will be described below with reference to the accompanying drawings. In the present embodiment, an inner rotor type three-phase DC brushless motor having four poles and six slots will be described as an example. Of the motor configuration, the configuration of the stator and the rotor will be mainly described.

With reference to FIG.1 and FIG.2, schematic structure of an IPM motor is demonstrated.
The structure of the stator 1 will be described. The stator core 2 is a laminated core formed by laminating and pressing electromagnetic steel plates, and pole teeth projecting radially toward the inner peripheral side in a plan view with respect to the annularly formed core back portion 2b. 2a (2a1, 2a2, 2a3: U-phase, V-phase, W-phase) is provided with 6 poles. Since the stator core 2 has 6 poles and 6 slots, the slot pitch is 120 ° in electrical angle (60 ° in mechanical angle). A coil 3 is wound around each of the pole teeth 2a1, 2a2, 2a3. The stator core 2 is assembled to the inner periphery of a bearing housing (not shown). An insulator 8 is mounted from the axial end surface of the stator core 2 (see FIG. 2B). A magnet wire is wound around the stator pole teeth 2a via an insulator 8 to form a coil 3 (see FIG. 1).

  Next, the structure of the rotor 4 will be described. As the rotor core 5, a laminated core formed by laminating and pressing electromagnetic steel sheets is used. On the outer peripheral surface of the rotor core 5, a plurality of curved surface portions 5 a that are opposed to the stator pole teeth 2 a and project outward in the radial direction serving as magnetic flux acting surfaces and concave surface portions 5 b that partition the curved surface portions 5 a are alternately arranged. Is formed. In this embodiment, since there are four poles, the curved surface portion 5a and the concave surface portion 5b are provided at four positions with a phase difference of 90 ° (mechanical angle).

  In each curved surface portion 5a, permanent magnets 6 are inserted into magnet insertion holes 5c provided on the radially inner side. As the permanent magnet 6, a rare earth magnet (neodymium magnet, samarium cobalt magnet or the like) is preferably used. The permanent magnet 6 is formed by inserting a magnetic body into the magnet insertion hole 5c of the rotor core 5 by insert molding and then magnetizing it.

  Further, the rotor shaft 7 is inserted into the central portion of the rotor core 5 and assembled integrally. The rotor shaft 7 is a metal shaft made of a magnetic material (SUS or the like). The rotor shaft 7 is rotatably supported by a bearing housing (not shown).

Further, as shown in FIG. 3B, a plurality of concave grooves 5d are provided at predetermined intervals in each curved surface portion 5a of the rotor core 5. The concave groove 5d provided in the rotor magnetic pole (curved surface portion 5a) has a central angle formed by the centers of adjacent concave grooves 5d as ζ (rad), i is an integer, T is a cogging cycle (electrical angle), and p is Assuming that the number of pairs of rotor magnetic poles is set, the concave grooves 5d are alternately provided to the curved surface portions 5a via the convex surface portions 5e at intervals of the central angle ζ calculated by ζ = 2i * π / T * p. Is desirable.
Since i is 2π (i = 1) on the T-order component plane of the cogging torque of the motor and repeats at the same position, it is always an integer. Further, when the order becomes higher and the magnetic attractive force vector interval becomes 2iπ, all the vectors overlap in the same direction and the cogging torque is improved.

In the case of this embodiment, the motor is a 4-pole 6-slot, i = 1, and the cogging torque period T is a value obtained by dividing the least common multiple (12) of the rotor pole number 4 and the stator slot number 6 by 2 periods. T = 12/2 = 6, and the number of pole pairs is counted as one pair by N · S, so that p = 4/2 = 2. Based on this, when the central angle ζ (rad) formed by the centers of the adjacent concave grooves 5d is calculated, ζ = 2 × i × π / {(12/2) × (4/2)} = 0.5233 (rad) It becomes.
When this is converted into a mechanical angle, ζ = (180 / π) × 0.5233 (rad) = 29.998≈30 ° (mechanical angle). From the above, it can be seen that the cogging torque is improved if the concave grooves 5d are alternately provided through the convex surface portions 5e at intervals of ζ = 30 ° with respect to the curved surface portions 5a.

  As shown in FIG. 3B, the angle between the center lines a1 and a2 of the concave groove 5d is ζ = 30 ° (mechanical angle). Since the central angle between the concave portions 5b is 90 ° (mechanical angle), the central angle θ between the central line a1 or the central line a2 and the central line b of the adjacent concave surface portion 5b is 30 ° (mechanical angle). It becomes. That is, in this embodiment, the convex portion 5e and the concave groove are calculated from the switching portion (concave surface portion 5b) of the rotor magnetic pole (curved surface portion 5a) every 15 ° (mechanical angle ζ / 2 between the center lines). 5d may be provided alternately. The cogging torque is generated because the groove vectors (magnetic attraction force vectors) on the sixth harmonic plane are all aligned on a straight line having zero phase. In order to increase the cogging torque, it is necessary to further increase the groove vector by providing an auxiliary concave groove at the 0 phase gap position of the sixth harmonic plane.

  Here, a mechanism for increasing the cogging torque will be described with reference to FIGS. Cogging torque is generated when the magnetic energy generated from a permanent magnet increases or decreases due to a change in permeance of the magnetic path, and the local energy changes. Therefore, when the slits (gap) overlap each other at the position where the rotor 4 and the stator 1 face each other, the magnetic path becomes thin, and the torque decreases.

  FIG. 5 shows a state where only two positions W where the slits (gap) overlap between the rotor 52 and the stator 51 occur. The cogging torque increases at the W position, but the cogging torque is weak at other positions where the rotor 52 and the stator 51 face each other, so that the cogging torque is easy to rotate.

  On the other hand, in FIG. 3A, a concave groove 5d is provided in the convex surface portion 5e of the rotor 4, and there are six positions W where slits (air gaps) overlap between the rotor 4 and the stator 1. is increasing. Because the concave groove 5d provided in the curved surface portion 5a of the rotor core 5 changes the magnetic field between the curved surface portion 5a of the rotor core 5 and the stator pole teeth 2a facing the cogging torque. . As a result, the cogging torque is increased and the rotor 4 is difficult to rotate from the stop position. Note that the rotor 4 stops at a magnetically most stable position with respect to the opposing stator 1.

FIG. 3B shows a state in which the rotor 4 is rotated in the counterclockwise direction, for example. In this state, since the position where the slit (gap) overlaps does not occur between the stator 1 and the rotor 4, the cogging torque is reduced and the rotor 1 is easily rotated.
FIG. 3C shows a state in which the rotor 4 is further rotated counterclockwise. In this state, as in FIG. 3A, the position W where the slit (gap) overlaps between the rotor 4 and the stator 1 has increased to six, so the cogging torque increases and the rotor 4 stops. It becomes difficult to rotate from the position.

FIG. 4 shows a graph in which the magnitude of the detent torque is compared between the case where the rotor 4 is provided with the concave groove 5d and the case where the groove 4d is not provided. FIG. 4 is a graph showing the rotation angle of the rotor 4 and the magnitude of the detent torque. The solid line portion in FIG. 4A is illustrated by contrasting the case where the rotor 4 is provided with the concave groove 5d and the broken line portion where the concave groove 5d is not provided.
Thus, it can be seen that the detent torque (holding torque) is increased when the concave groove 5d is provided compared to the case where the concave groove 5d is not provided.

The motor is not limited to a 4-pole 6-slot motor, and may be another type of motor.
For example, in the case of a 6-pole 9-slot motor, i = 1, the cogging torque period T is a mechanical angle of 360 °, the rotor pole number (6), and the least common multiple (18) of the stator slot number (9) in two periods. The divided value is T = 18/2 = 9, and the number of pole pairs is counted as one pair by N · S, so p = 6/2 = 3. Based on this, when the central angle ζ (rad) formed by the centers of the adjacent concave grooves 5d is calculated, ζ = 2 × 1 × π / {(18/2) × (6/2)} = 0.327 (rad) It becomes. When this is converted into a mechanical angle, ζ = (180 / π) × 0.2327 (rad) = 13.332≈13.3 ° (mechanical angle). As described above, the central angle between the concave surface portions 5b is 60 ° (mechanical angle), and the concave grooves 5d pass through the convex surface portion 5e at intervals of ζ = 13.3 ° (mechanical angle) with respect to the curved surface portions 5a provided therebetween. It can be seen that the cogging torque is improved if they are alternately provided.

  The three-phase DC brushless motor is used as a drive source in an application for holding a rotor at a predetermined position as a vehicle-mounted motor. In addition, in order to perform sensorless driving, energization control is performed by back electromotive force and inductance change. As described above, when the cogging torque (holding torque) is increased, the change in the magnetic field between the rotor magnetic pole and the stator magnetic pole increases, so the back electromotive force and the inductance change increase. Controllability is also improved.

  Moreover, although the embodiment described above is applied to the magnetic poles of the rotor core, it can also be applied to the magnetic poles (pole teeth) of the stator core. In this case, a concave groove is provided in the curved surface portion that is the magnetic flux acting surface of the pole teeth of the stator 1.

  DESCRIPTION OF SYMBOLS 1 Stator 2 Stator core 2a 2a1 2a2 2a3 Pole tooth 2b Core back part 3 Coil 4 Rotor 5 Rotor core 5a Curved surface part 5b Concave part 5c Magnet insertion hole 5d Concave groove 5e Convex part 6 Rotor magnet 7 Rotor shaft 8 Insulator

Claims (3)

A radial gap type IPM motor in which a rotor magnetic pole in which a plurality of permanent magnets are embedded in a rotor core is disposed opposite to a stator pole tooth,
The rotor magnetic poles or the stator pole teeth are formed with a plurality of curved surface portions projecting in a radial direction to serve as magnetic flux acting surfaces and concave surface portions that partition the curved surface portions, and each curved surface portion. The IPM motor is characterized in that each is provided with a concave groove.   Ζ = 2i * π, where ζ is the center angle formed by the centers of adjacent concave grooves provided on the rotor magnetic pole or the stator pole teeth, i is an integer, T is the cogging period, and p is the number of rotor pole pairs. 2. The IPM motor according to claim 1, wherein the concave grooves are alternately provided to the curved surface portions via the convex surface portions at intervals of a central angle ζ calculated by / T * p.   Permanent magnets are inserted into the magnet insertion holes provided on the radially inner side of the curved surface portions protruding from the outer peripheral surface of the rotor core of the inner rotor type motor, and the curved surface portions are partitioned by the concave grooves. The IPM motor according to claim 1, wherein the convex surface portions are formed at a predetermined interval.