JP2002300740A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in an electric motor, the cogging torque of the motor becomes large due to the occurrence of the variation of flux density synchronized by a simultaneous reach of a pair of opposing teeth 2a to pole ends of permanent magnets 3, 4 in the case that the permanent magnets 3, 4 are two-pole magnets and the number of the armature teeth 2a is an even number such as ten. SOLUTION: Notches 3a, 4a are formed at internal peripheral faces of end parts in peripheral directions of the permanent magnets 3, 4 so as to be linearly symmetric with a reference of a symmetrical line A relative to each permanent magnet 3, 4, and non-linearly symmetric relative to an orthogonal line B that intersects the symmetrical line A, thus eliminating the variation of the flux density synchronized as above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an electric motor used as a drive source in various fields such as electric components.

[0002]

2. Description of the Related Art In general, an electric motor is constituted by fixing a permanent magnet to an inner peripheral surface of a yoke and rotatably bearing an armature core (rotor core) in which an exciting coil (rotor coil) is wound. The number of teeth is set to an even number and an odd number as an armature core of this kind, but the odd number has an even number slot due to difficulty in winding the excitation coil and poor productivity. Often do.

[0003]

As shown in FIG. 7, at the magnetic pole tip of the permanent magnet 11, a large change occurs in the magnetic flux density of the teeth 12a formed on the armature core 12, which causes cogging torque and torque unevenness. Thus, there is a problem that smooth rotation is impaired. Particularly, when the teeth are even-numbered, the opposing teeth 12a,
Since the 12a members simultaneously reach the magnetic poles of the permanent magnet 11 and the torque generated between the opposed teeth has the same phase, there is a problem that the cogging torque and the torque unevenness are large, and the present invention There are issues to be solved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems in view of the above-mentioned circumstances, and a first invention is a permanent invention arranged inside a yoke. In an electric motor including a magnet and an armature core rotatably provided inside the permanent magnet, the same number of pole pairs as the number of pole pairs are continuously formed on the inner circumferential surface of the end of the permanent magnet in the circumferential direction. An electric motor characterized in that the same notch is formed in the electric motor. According to a second aspect of the present invention, there is provided an electric motor including a permanent magnet disposed inside the yoke, and an armature core rotatably provided inside the permanent magnet. The electric motor is characterized in that notches are formed on the inner peripheral surface of the end portion so as to be alternately arranged in the circumferential direction. With such a configuration, the torque generated between the opposing teeth when the magnetic pole of the permanent magnet is reached can be made out of phase, so that cogging torque and torque unevenness can be reduced. In these, the notch is characterized in that it is formed on one of the inner circumferential surfaces at both ends in the circumferential direction of the permanent magnet, or has a different shape on the inner circumferential surface at both ends in the circumferential direction of the permanent magnet. It can be characterized by being formed in a state. In these, the number of slots formed in the armature core can be characterized by an even number, and thus, the productivity is improved.

[0005]

Next, a first embodiment of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 denotes an electric motor for electric power steering. The electric motor 1 has a yoke 2 formed on a bottomed cylinder, and a pair (two) fixed symmetrically to the inner peripheral surface of the yoke 2. The permanent magnets 3 and 4 each having 1 and 2 poles and the number of pole pairs are 1), an armature core 5 rotatably supported inside the permanent magnets 3 and 4, a core shaft 5a thereof, and a commutator fixed to the core shaft 5a. As is conventionally the case, it is constituted by various member devices such as a brush 7 slidingly contacting the commutator 6, an elastic device 8 for pressing the brush 7, an end case 9 covering the opening of the yoke 2, and the like.

The armature core 5 includes a tooth 5b
Are formed (even number of slots is 10). On the other hand, each of the pair of permanent magnets 3 and 4 has an inner peripheral surface at one end of adjacent ends opposed to each other in the circumferential direction, and the inner peripheral surface is notched.
a, 4a are cut out by the same angle θ from the respective circumferential end faces 3b, 4b of the permanent magnets 3, 4 which are opposed to each other. The permanent magnets 3 and 4 are symmetrical with respect to the radial line (center line) A passing through the center of the yoke between the opposing surfaces, while the permanent magnets 3 and 4 have end faces 3b and 3c. , 4b and 4c are non-linearly symmetric with respect to the center line B in the circumferential direction of each of the permanent magnets 3 and 4, that is, a line orthogonal to the diameter line A.
The pair of permanent magnets 3 and 4 have notches 3a and 4a formed alternately in the circumferential direction. In the present embodiment, the polar arc angle of the permanent magnet is set at 112 degrees, and the notch angle θ is set at 15 degrees.

The results of measuring the cogging torque and the torque unevenness (when a current of 8 amperes is passed) of the conventional device having the notches and the device having the notches 3a and 4a in the device configured as described above. In FIG. 3 (A)
It is shown in (B). In these, the solid line is the conventional product without a notch, and the broken line is the present embodiment. When these were compared, it was observed that the product of the present invention improved both the cogging torque and the torque unevenness by about 33% as compared with the conventional product. Although it is high, the torque generated between the opposed teeth 2a when the magnetic poles of the permanent magnets 3 and 4 reach the magnetic poles can be brought into an out-of-phase state, so that cogging torque and torque unevenness can be reduced.

Next, the second embodiment shown in FIG. 4 is a four-pole electric motor, which has four permanent magnets 13, 14, 15, 16 (in the circumferential direction). N
Poles, S poles, N poles, and S poles) are provided at 90-degree pitches. And these permanent magnets 13, 14, 15, 1
On the inner circumferential surface of the circumferential end portion of 6, one of a pair of symmetry lines X and Y drawn through the center of the yoke 2 so as to pass between adjacent permanent magnets. The notches 13a, 14a, and 15 are axisymmetric with respect to X and asymmetric with respect to the other symmetric line Y.
a and 16a are formed. And in this one,
When the symmetrical line X is used as a partitioning line, two continuous (the number of pole pairs) permanent magnet groups 13 and 16 and 14 and 15 are cut out 13a and 16a on the same surface, respectively.
14a and 15a are formed, and the two permanent magnet groups 13 and 14, and 15 and 16 that are separated when the symmetrical line Y is used as a partition line, are cut into alternate planes in the circumferential direction. Notches 13a and 14a, 15a and 16a will be formed, and in this way, the pole tips of the permanent magnets 13, 14, 15, 16 will be formed while increasing productivity as a 4-pole even slot. The torque generated in each tooth 2a that has reached the above-mentioned condition can be brought into an out-of-phase state, so that cogging torque and torque unevenness can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and the form of the notch is not limited to being formed only at one end in the circumferential direction of the permanent magnet.
As in the third and fourth embodiments shown in FIGS. 5A and 5B, they may be formed at both ends of the permanent magnets 17, 18, 19, 20, 21, 22, and 23. Chip 17a, 1
7b, 18a, 18b, 19a, 19b, 20a, 20
b, 21a, 21b, 22a, 22b, 23a, 23b
For the shape of, change the notch angles θ ₁ and θ ₂ or
The present invention can be implemented by changing the notch depth.

[0010] Further, the present invention can be implemented as in the fifth and sixth embodiments shown in FIG. This motor is a six-pole electric motor, but the motor shown in FIG. 3A is divided by a partition line X to form three (pole pairs) permanent magnet groups 24, 25 and 26, 27 and 28, respectively. The same cutouts are formed in each of the 29 magnets so that the magnet groups are symmetrical with each other at the partition line X, and the permanent magnets 30, 31, 32, 33, and 34 are shown in FIG. , 35 are formed with notches so as to be alternately arranged in the circumferential direction, so that the present invention can be implemented.

[Brief description of the drawings]

FIG. 1 is an electric motor for electric power steering.

FIG. 2 is a cross-sectional view illustrating a relationship between a permanent magnet and an armature core according to the first embodiment.

3A is a measurement result of cogging torque, and FIG. 3B is a measurement result of torque unevenness.

FIG. 4 is a cross-sectional view illustrating a relationship between a permanent magnet and an armature core according to a second embodiment.

5A is a cross-sectional view illustrating a relationship between a permanent magnet and an armature core according to a third embodiment, and FIG.

FIG. 6A is a cross-sectional view illustrating a relationship between a permanent magnet and an armature core according to a fifth embodiment, and FIG.

FIG. 7 is a cross-sectional view showing a relationship between a conventional permanent magnet and an armature core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric motor 3, 4 Permanent magnet 3a, 4a Notch 5 Armature core 5a Teeth

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H622 AA02 CA02 CA05 CA12 CA13 CB01 CB04 5H623 AA02 BB07 GG13 GG14 GG15 GG16 GG22 GG23 GG28

Claims (5)

[Claims] 1. An electric motor comprising: a permanent magnet disposed inside a yoke; and an armature core rotatably provided inside the permanent magnet, wherein an end of the permanent magnet in a circumferential direction is provided. An electric motor characterized in that the same notch is formed on a peripheral surface of a continuous number of pole pairs. 2. An electric motor comprising: a permanent magnet disposed inside a yoke; and an armature core rotatably provided inside the permanent magnet, wherein an end of each of the permanent magnets in a circumferential direction is provided. An electric motor characterized in that notches are formed on the inner peripheral surface so as to be alternate in the circumferential direction. 3. The electric motor according to claim 1, wherein the notch is formed on one of inner circumferential surfaces of both ends in a circumferential direction of the permanent magnet. 4. The electric motor according to claim 1, wherein the notches are formed in different shapes on inner circumferential surfaces of both ends in a circumferential direction of the permanent magnet. 5. The electric motor according to claim 1, wherein the number of slots formed in the armature core is an even number.