JPH10285848A - Permanent magnet type motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient, low cost permanent magnet type motor by preventing the generation of circulating current. SOLUTION: In a permanent magnet type motor equipped with a field magnet 2 comprising a ring magnet provided with a slit 21 parallel to an axial direction at one place on the circumference and an armature 3 having three-phase armature windings 4 oppositely through an air gap in the field magnet 2, the field magnet 2 is a divisor of the number of poles and is formed by a plurality of ring magnets 2a, 2b, 2c, 2d divided in an axial direction of the field magnet 2 by multiple of the number of slit positions as the multiple of the number of parallel circuits of each phase of armature winding 4, and the position of 21 slit is located at a position shifted uniformly by the number of slit positions in circumferential direction with the unmagnetized portion of the field magnet 2 as reference. Therefore, the same amount of distortion occurs in respective coils at the same time, the amount of magnetic flux interlinking with each coil becomes always equal, induced voltage occurred in every coil is all equal, and the circulating current is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor using a ring-shaped permanent magnet as a field.

[0002]

2. Description of the Related Art Conventionally, when a permanent magnet is formed into a ring shape by sintering ferrite or the like, the shrinkage in the circumferential direction differs from that in the radial direction during sintering. Easy to crack. Also, Nd-Fe
Since the -B ring magnet has a negative coefficient of thermal expansion with respect to the temperature rise in the circumferential direction, the permanent magnet may be cracked due to the temperature rise during operation of the motor. Therefore, in order to prevent the ring-shaped permanent magnet from cracking, there has been disclosed an electric motor in which a slit is provided in the permanent magnet in advance (for example, JP-A-6-86483). That is, for example, as shown in FIG. 7A, the rotor 1 fixed to the rotating shaft 11 uses a ring magnet 2A as the field magnet 2 on the outer periphery. The ring magnet 2A is made of a radially anisotropic cylindrical ferrite magnet, and a slit 21 is provided beforehand at one place on the circumference, and the other parts are integrated. Further, the ring magnet 2A is magnetized so that the polarity is alternately changed in the circumferential direction. An armature core 31 constituting the armature 3 is provided on the outer periphery of the ring magnet 2A via a gap, and the unit coils of each phase are connected to the armature core 31 in parallel as shown in FIG. A three-phase (U-phase, V-phase, W-phase) armature winding 4 (coil 4
a, 4b, 4c, 4d). In this case, if the slit 21 is provided on the magnetic pole, the gap 21 reduces the gap magnetic flux density and causes a distortion in the induced voltage waveform. Therefore, the slit position is arranged in a non-magnetized portion between the magnetic poles to reduce adverse effects. ing.

[0003]

However, in the above-mentioned prior art, the adverse effect on the induced voltage due to the slit 21 cannot be completely eliminated.
When skew magnetizing is performed, as shown in FIG. 7B, the non-magnetized portion between the magnetic poles is oblique, and it is difficult to completely dispose the entire slit 21 in the non-magnetized portion. Therefore, as shown in FIG. 9 (represented only for the U-phase among the three phases), the induced voltage waveform is distorted as shown by the dotted line. The coils a, c, and d have non-uniform induced voltage waveforms, such as no distortion. Therefore, there is a problem that a circulating current is generated due to a voltage difference between the parallel circuits of the armature windings 4 and the motor efficiency is reduced. It is also possible to provide the slit 21 in parallel to the skewed unmagnetized portion, but the ring magnet 2A
There is a problem that the cost increases. The present invention
It is an object of the present invention to provide an efficient, low-cost permanent magnet type electric motor that prevents generation of a circulating current.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a field magnet comprising a ring magnet provided with a slit parallel to the axial direction at one location on the circumference, and the field magnet described above. And an armature having three-phase armature windings facing each other with an air gap therebetween, wherein the field magnet is a divisor of the number of poles of the field magnet, and The field magnet is formed by a plurality of ring magnets divided in the axial direction of the field magnet by a multiple of the number of slit positions, which is a multiple of the number of parallel circuits of each phase of the winding, and the position of the slit is not magnetized by the field magnet. It is arranged at a position shifted evenly in the circumferential direction by the number of slit positions with reference to the portion.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, 1 is a rotor, 11 is a rotating shaft, 2 is a field magnet provided on the outer periphery of the rotor 1, and a radially anisotropic cylinder divided into four parts in the axial direction as shown in FIG. Ring magnets 2a, 2b, 2c, and 2d composed of Nd-Fe-B-based magnets.
1 is provided, and the others are integrated. The ring magnets 2a, 2b, 2c, 2d are magnetized so as to have different polarities alternately in the circumferential direction. A stator core 31 constituting the armature 3 is provided on the outer periphery of the field magnet 2 through a gap.
And a three-phase (U, V, W phase) armature winding 4 is wound around the stator core 31.

Here, the number of coils of the armature winding 4 per phase is four (coils 4a, 4b, 4c, 4d), the number of parallel circuits is four, and the number of magnetic poles of the field magnet 2 is eight. In the case, the number of divisions of the field magnet 2 in the axial direction and the ring magnets 2a, 2b, 2c, 2d forming the field magnet 2
The relationship between the magnetized position and the position of the slit 21 will be described with reference to FIG. Note that the relationship between the armature winding 4 and the field magnet 2 is the same for each of the three phases, so the U phase will be representatively described. Ring magnet 2a, 2
b, 2c and 2d are sequentially arranged in the axial direction, and the magnetic poles are magnetized in a skewed state. Each ring magnet 2
a, 2b, 2c, 2d slits 21a, 21b, 21
c and 21d are arranged at positions that are evenly shifted by the number of slit positions that is a divisor of the number of poles and a multiple of the number of parallel circuits of each phase of the armature winding. Therefore, the number of divisions into which the field magnet is divided in the axial direction may be a multiple of the number of slit positions. In this case, since the number of parallel circuits is four and the number of magnetic poles is eight, the number of slit positions is four, and the field magnet 2 is divided into four ring magnets 2a, 2b, 2c, and 4 in the axial direction.
2d, which are sequentially shifted by 90 degrees in the circumferential direction with respect to the non-magnetized portion at the boundary between the magnetic poles. With such a configuration, the induced voltage waveforms of the coils 4a, 4b, 4c, and 4d are simultaneously affected by the slit 21a and the coil 4b is affected by the slit 21b, as shown in FIGS. Influence, the coil 4c is affected by the slit 21c, and the coil 4d is affected by the slit 21d, and is distorted as indicated by a dotted line. However, since the same amount of distortion is simultaneously generated in each coil, the amount of magnetic flux linked to each coil is always equal, and the induced voltages generated in each coil are all equal. Therefore, no circulating current is generated in the parallel circuit of the armature windings 4.

FIG. 5 shows that the number of U-phase coils of the armature winding 4 is four.
(Coil 4a, 4b, 4c, 4d), coil 4A in which coils 4a and 4b are connected in series, and coil 4A
c and 4d are composed of a set coil 4B connected in series. When the set coils 4A and 4B are connected in parallel, the number of parallel circuits is two, and the number of magnetic poles of the field magnet 2 is eight. The magnetization positions of the ring magnets 2a, 2b, 2c, 2d;
FIG. 4 is an explanatory diagram showing a relationship with a position of a slit 21. In this case, since the number of parallel circuits is two and the number of magnetic poles is eight, the number of slit positions is two, and two slits 21a, 21b and a slit are provided for each of the two ring magnets 2a, 2b and 2c, 2d. 21c and 21d are arranged at 180 degrees in the circumferential direction with reference to the unmagnetized portion at the boundary between the same magnetic poles. With such a configuration, a distortion is generated in the combined induced voltage waveform of the grouped coil 4A and the grouped coil 4B as shown by the dotted lines in FIGS. 6 (a) and 6 (b). That is, at the same time, the coil 4a is affected by the slit 21a, the coil 4c is affected by the slit 21c, and after rotating 90 degrees, the coil 4b is simultaneously affected by the slit 21b, and the coil 4d is affected by the slit 21d and distorted. However, since the same amount of distortion is simultaneously generated in each set coil, the amount of magnetic flux linked to each coil is always equal, and the induced voltages generated in each coil are all equal. Therefore, no circulating current is generated in the parallel circuit of the armature windings 4. The condition of the number of slit positions at which the circulating current is not generated is not limited to the number of poles and the number of parallel circuits shown in the embodiment, but is a divisor of the number of poles and the number of parallel circuits of each phase of the armature winding. What is necessary is just to arrange | position at the position shifted equally in the circumferential direction by the number of slit positions which are multiples.

[0008]

As described above, according to the present invention, a field magnet formed by arranging a plurality of ring magnets provided with one slit in the circumferential direction in the axial direction is provided. Since the number of slit positions at which the slits are equally divided in the circumferential direction is set to be a divisor of the number of magnetic poles of the field and a multiple of the number of parallel circuits of each phase of the armature winding, the same distortion The amount is generated simultaneously in each coil, the amount of magnetic flux linked to each coil is always equal, and the induced voltages generated in each coil are all equal. Further, since the shape of the slit can be provided in parallel with the axial direction, processing is easy. Therefore, no circulating current is generated in the parallel circuit of the armature windings, so that an efficient and low-cost permanent magnet motor can be provided.

[Brief description of the drawings]

FIG. 1 is a cutaway view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a state where the rotor of the embodiment of the present invention is disassembled.

FIG. 3 is a development view of an armature winding and a rotor showing the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an induced voltage waveform generated in each coil according to the embodiment of the present invention.

FIG. 5 is a development view of an armature winding and a rotor showing another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an induced voltage waveform generated in each coil according to another embodiment of the present invention.

FIG. 7 is a cutaway view showing a conventional example.

FIG. 8 is a development view of an armature winding and a rotor showing a conventional example.

FIG. 9 is an explanatory diagram showing an induced voltage waveform generated in each coil of the conventional example.

[Explanation of symbols]

1: rotor, 11: rotating shaft, 2: field magnet, 2a, 2
b, 2c, 2d: ring magnet, 21, 21a, 2
1b, 21c, 21d: slit, 3: armature, 31:
Electric private iron core, 4: armature winding, 4a, 4b, 4c, 4
d: coil, 4A, 4B: assembled coil

Claims (1)

[Claims] 1. A field magnet consisting of a ring magnet provided with a slit parallel to the axial direction at one place on the circumference, and a three-phase armature winding opposed to the field magnet via an air gap. Wherein the field magnet has a slit position that is a divisor of the number of poles of the field magnet and a multiple of the number of parallel circuits of each phase of the armature winding. It is formed by a plurality of ring magnets divided in the axial direction of the field magnet by a multiple of the number, and the positions of the slits are evenly distributed in the circumferential direction by the number of the slit positions with respect to the unmagnetized portion of the field magnet. A permanent magnet type electric motor which is arranged at a shifted position.