JPH087800Y2 - Permanent magnet type rotating electric machine - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a permanent magnet type rotary electric machine, and is devised so as to easily obtain a permanent magnet having a shape that reduces the generation of cogging torque.

B. Outline of the Invention The present invention makes it possible to easily manufacture this permanent magnet by linearly approximating a curve that gives the shape of the permanent magnet that reduces the cogging torque.

C. Conventional Technology A three-phase brushless DC motor is used as a spindle motor for a floppy disk driver motor, VTR cylinder motor and hard disk driver. In a three-phase brushless DC motor, a current switched by an inverter is passed through an armature winding of a stator, and a rotor is provided with a permanent magnet as a field source.

By the way, in this type of three-phase brushless DC motor, the magnetic flux density of the permanent magnet, which is the field source, and the reluctance of the armature slot cause the armature current to flow depending on the position of the armature. Torque is generated. This torque is called cogging torque. The cogging torque causes uneven rotation and reduces the starting torque.

A rotary electric machine disclosed in Japanese Patent Application No. 62-125696 has been proposed as a permanent magnet type rotary electric machine that can reduce such cogging torque as much as possible.

This is because the field is formed by multiple permanent magnets, and a pair of permanent magnets that form one pole pair face the 3m (m is a positive integer) slot of the armature core. The magnetic flux density B (θ) at each angle θ (the angle is an electrical angle) of each permanent magnet is (I) −90 ° ≦ θ ≦ θ ₂ In the section (II) In the section of θ ₂ <θ <θ ₁ B (θ) = B _m (III) In the section of θ ₁ ≤ θ ≤ 90 ° However n is a positive integer 3/2 m ≧ n B _m is characterized by using a permanent magnet having a shape or a magnetization orientation such that it becomes a constant.

D. Problems to be Solved by the Invention In the rotary electric machine disclosed in Japanese Patent Application No. 62-125696, the cogging torque is certainly remarkably reduced, but both ends of the permanent magnet are connected to those of the above (I) and (III). It is necessary to process it into a curve that meets the requirements. Therefore, it has been found that this process causes a problem that it is time-consuming and costly.

In view of the above-mentioned problems of the prior art, the present invention provides a permanent magnet type rotating electric machine that can reduce the cogging torque as much as possible and can easily process a permanent magnet that is a field source into a predetermined shape. To aim.

E. Means for Solving Problems The configuration of the present invention for achieving the above object is as follows: (I) The magnetic flux density B (θ) at each angle θ (the angle is an electrical angle) of each permanent magnet is θ ₂ B (θ) = B _{m in} the section of <θ <θ ₁ and (II) radially extends from the center of the rotary electric machine in the section of −90 ° ≦ θ ≦ θ ₂ and θ ₁ ≦ θ ≦ 90 °. A _first point that is an intersection of a permanent magnet and a straight line that gives the angles θ ₁ and θ ₂ , and a first point that is perpendicular to the magnet center axis that is a straight line that passes through the center of the rotating electric machine and the center position of the permanent magnet. A straight line passing through the point as well as The second point that is the intersection with the curve such that and the third point that gives the end of the permanent magnet n is a positive integer 3/2 m ≧ n B _m is characterized by having a permanent magnet having a shape defined by a first straight line and a second straight line passing through a constant respectively.

F. Action According to the present invention having the above configuration, the curve defined by the constituent requirements (I) and (III) of the permanent magnet of the permanent magnet type rotating electric machine according to Japanese Patent Application No. 62-125696 is the first straight line. And a second straight line. Therefore, although the permanent magnet is easily processed, the generation of the cogging torque can be suppressed to the minimum.

G. Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view showing a rotary electric machine according to an embodiment of the present invention. The rotating electric machine shown in the figure is an outer rotor type permanent magnet type rotating electric machine, in which the field of the stator is 12 permanent magnets 1.
And a pair of permanent magnets 1 that form a pair of poles face the three slots of the armature core 2 that is the rotor.

At this time, the permanent magnets 1 are fixed by fixing the wedge-shaped pressing metal fittings 3 straddling between the permanent magnets 1 adjacent to each other in the circumferential direction and abutting the respective end portions to the frame 5 of the stator with bolts 4. There is.

Since it is difficult to form a hole in the permanent magnet 1, it is impossible to fix the permanent magnet 1 directly to the frame 5 with bolts. In the conventional technique, as shown in FIG. The permanent magnet 1 was attached to the inner peripheral surface of the frame 5 with the agent 6. However, the conventional technique has the following drawbacks.

1) The adhesive 6 is not reliable because of the following reasons, and the permanent magnet 1 often falls off.

a) Sensitive to heat and moisture b) Adhesive strength is greatly affected by the base treatment and curing method and is not stable.

c) There is a secular change.

2) Since the thickness of the adhesive 6 is not constant, the accuracy of the gap becomes poor.

3) At the time of assembly, due to the magnetic force of the permanent magnet 1, as shown in FIG. 5, the permanent magnets 1 stick to each other, and it is difficult to keep the interval between the adjacent permanent magnets 1 constant.

FIG. 2 is a front view showing one of the permanent magnets 1 extracted and an enlarged right half thereof.

As shown in the figure, the permanent magnet 1 has the following constituent elements.

When the central position of the permanent magnet 1 is set to 0 ° with respect to the rotation direction, (I) the magnetic flux density B (θ) at each angle θ (the angle is an electrical angle) of each permanent magnet 1 is θ ₂ <θ <θ _In the section ₁ B (θ) = B _m (II) In the section θ ₁ ≤ θ ≤ 90 °, it is the intersection of the straight line L ₁ and the permanent magnet that gives the angle of θ ₁ radially extending from the center of the rotating electric machine. A first point A, a straight line l ₀ passing through the first point A at a right angle to a magnet central axis L ₀ which is a straight line passing through the center of the rotating electric machine and the center position of the permanent magnet 1, The second point B which is the intersection with the curve R such that and the third point C which gives the end of the permanent magnet 1 n is a positive integer 3/2 m ≧ n B _m has a shape defined by the first and second straight lines l ₁ and l ₂ that pass constants, respectively.

That is, the permanent magnet 1 according to the present embodiment is the case where m = n = 1, and the curve R (this curve gives the shape of Japanese Patent Application No. 62-125696) is divided into the first and second straight lines l ₁ , L ₂ is approximated. The left half of the permanent magnet 1 has a shape symmetrical with the right half with respect to the magnet central axis L ₀ .

FIG. 3 is a graph showing cogging torque characteristics of the rotating electric machine in various magnet shapes. In the figure, a magnet shape 1 is a rotary electric machine according to the prior art using a permanent magnet of uniform thickness having an outer circumference and an inner circumference part of concentric circles, and a magnet shape 2 is Japanese Patent Application No. 62-125696. The rotating electric machine and the magnet shape 3 according to No. 3 are the rotating machine according to the present embodiment.

Referring to the figure, the rotary electric machine of this embodiment is disclosed in Japanese Patent Application No. 62-125.
It can be seen that it has almost the same cogging torque characteristics as the rotating electrical machine of No. 696.

H. Effect of the Invention As described in detail with the embodiments above, according to the present invention, it is realized by linearly approximating the shape of the permanent magnet for reducing the cogging torque as much as possible.
The permanent magnet can be easily processed into a predetermined shape while the cogging torque is minimized.

[Brief description of drawings]

FIG. 1 is a front view showing a 12-pole permanent magnet type rotating electric machine according to an embodiment of the present invention, FIG. 2 is a front view showing a partial cutaway of a permanent magnet, and FIG. 3 is a cogging torque for each magnet shape. Graphs showing characteristics, FIGS. 4 and 5 are explanatory views for explaining a fixing mode of a permanent magnet according to a conventional technique. In the drawings, 1 is a permanent magnet, 2 is an armature core, A is a first point, B is a second point, C is a third point, l ₁ is a first straight line, l ₂ is a second straight line. Is.

Claims (1)

[Scope of utility model registration request] 1. A rotary electric machine in which a field is formed by a plurality of permanent magnets, and a pair of permanent magnets forming one pole pair is opposed to 3 m (m is a positive integer) slots of an armature core. When the central position of the permanent magnet is set to 0 ° with respect to the rotation direction, (I) the magnetic flux density B (θ) at each angle θ (the angle is an electrical angle) of each permanent magnet is θ ₂ <θ < In the section of θ ₁ , B (θ) = B _m, and (II) in the section of −90 ° ≦ θ ≦ θ ₂ and θ ₁ ≦ θ ≦ 90 °, θ ₁ radially extending from the center of the rotating electric machine, The first point, which is the intersection of the straight line giving the angle of θ ₂ and the permanent magnet, and the first point, which is a straight line passing through the center of the rotating electric machine and the center position of the permanent magnet, is perpendicular to the first point. A straight line passing through, as well as The second point that is the intersection with the curve such that and the third point that gives the end of the permanent magnet n is a positive integer 3/2 m ≧ n B _m is a permanent magnet type rotating electric machine characterized by having a permanent magnet having a shape defined by a first straight line and a second straight line which pass a constant respectively.