JPH08256461A - Permanent magnet motor - Google Patents

Abstract

PURPOSE: To suppress variation in torque and prevent degradation in the efficiency of motor. CONSTITUTION: A rotor 19 formed by bonding four permanent magnets 21 on the inside surface of a cylindrical container-like rotor yoke 20, is installed on a shaft supported in a cylindrical housing 13 in such a manner that it can be freely rotated. A stator core 14 having three teeth 15 radially extended and containing winding 16 in their slots, is bonded to the circumference of the housing 13. The magnetic pole portion 15a at the tip of each of the teeth 15 is opposed to the permanent magnets 21 with a small air gap 22 inbetween. Holes 23 for limiting the magnetic paths, through which magnetic flux runs, are formed on the magnetic pole portions 15a in a position slightly backed away from their outer edge. The holes 23 are so formed that they will be positioned on the same circumference and equally divide each magnetic pole portion 15a, and that they will go through in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet type motor in which the magnetic poles at the tips of a plurality of teeth of a stator core having polyphase windings are arranged to face a rotor having permanent magnets via an air gap. .

[0002]

2. Description of the Related Art As an example of this type of permanent magnet type motor, a conventional general structure of an outer rotor type motor is shown in FIG. That is, the stator core 1 has, for example, three tooth portions 2 that extend radially, and each tip portion thereof has
The magnetic pole portion 2a is provided so as to spread in the circumferential direction. Further, the slots of the stator core 1 (between the teeth portions 2)
A winding 3 is provided on the.

On the other hand, on the outer peripheral side of the stator core 1, for example, four permanent magnets 4 having N poles and S poles alternately in the circumferential direction are provided.
Is disposed so as to face the magnetic pole portion 2a with a slight air gap therebetween. In this case, as indicated by an arrow a in a part of FIG. 6, the magnetic flux from the permanent magnet 4 passes toward the facing magnetic pole portion 2a.

However, in such a conventional general structure, the permanent magnet 4 is opposed between the state where the permanent magnet 4 faces directly to the magnetic pole portions 2a and the state where it faces the space between the magnetic pole portions 2a. The fluctuation of the amount of magnetic flux passing through the stator core 1 becomes large and the fluctuation of the rotational torque (torque ripple) becomes large, which causes vibration and noise of the motor.

[0005]

Therefore, in order to eliminate such a drawback, in recent years, as shown in FIG. 7, the recesses 6 are provided at, for example, two places on the outer peripheral surface of each magnetic pole portion 2a ( A concave pole structure) is considered. According to this, since the magnetic resistance increases due to the recessed portion 6, as shown by an arrow b in FIG. 7, the magnetic flux amount is increased at a position where the permanent magnet 4 faces the magnetic pole portion 2a and has the maximum rotational torque. The maximum torque is suppressed and the maximum torque is reduced, and the torque fluctuation width is reduced as a whole. At the same time, the concave portion 6 exhibits the same action as the space portion and becomes a high frequency state in which the cycle of torque fluctuation is shorter, and the periodic fluctuation with respect to the rotation of the motor occurs. The torque fluctuation is improved as compared with the above-described general structure because the above effect is less likely to occur.

However, in the concave pole structure shown in FIG. 7, the air gap is substantially increased by providing the concave portion 6, which causes a decrease in magnetic efficiency, that is, motor efficiency. Will end up.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a permanent magnet type motor capable of suppressing torque fluctuations to a small extent and suppressing a decrease in motor efficiency. is there.

[0008]

According to another aspect of the present invention, there is provided a permanent magnet type motor, wherein the magnetic pole portions at the tips of a plurality of teeth portions provided on a stator core having a plurality of windings are provided on a rotor having a permanent magnet. It is characterized in that it is arranged so as to face each other through an air gap, and a hole extending in the axial direction is provided at a position that is reserved from the peripheral edge of the magnetic pole portion of the stator core facing the rotor.

In this case, the holes can be provided on the same circumference with the rotation axis as the center and arranged substantially evenly on each of the magnetic pole portions (invention of claim 2), and a plurality of holes can be provided. Of the teeth portions, the teeth portions having holes and the teeth portions having no holes can be arranged at a predetermined pitch (the invention of claim 3).

Further, the hole may be formed in a bottomed hole state that does not penetrate in the axial direction of the stator core (the invention of claim 4). Furthermore, the hole can be formed to have an elongated hole cross section (the invention of claim 5).

[0011]

According to the permanent magnet type motor of claim 1 of the present invention, since the hole formed in the magnetic pole portion serves as a magnetic resistance,
When the magnetic path becomes narrower by that amount and the magnetic flux passing through the stator core exceeds a certain level, magnetic saturation occurs. Therefore, the amount of magnetic flux is suppressed and the maximum torque is reduced as compared with the case where there is no hole, the torque fluctuation width is reduced as a whole, and at the same time, the cycle of torque fluctuation is shortened by the hole. And
Since the hole is formed at a position away from the peripheral edge of the magnetic pole portion, the peripheral edge portion of the magnetic pole portion is in a connected state, and the air gap becomes large like a concave pole structure in which a concave portion is formed in the peripheral edge portion of the magnetic pole portion. There is no such thing. Therefore, as compared with the concave pole structure, the magnetic efficiency is improved at a position where magnetic saturation does not occur.

In this case, the holes are located on the same circumference around the rotation axis and are evenly arranged on each magnetic pole portion (permanent magnet type motor according to claim 2) to balance the magnetic flux distribution. Can be good. In addition, the balance of the magnetic flux distribution is similarly adjusted by disposing a tooth portion having no hole between the tooth portions having holes among the plurality of tooth portions (a permanent magnet type motor according to claim 3). You can

Further, it goes without saying that the holes can be formed so as to penetrate in the axial direction of the stator core.
By forming a bottomed hole that does not penetrate the stator core in the axial direction (permanent magnet type motor of claim 4), the magnetic resistance can be adjusted according to the depth thereof. Furthermore, it goes without saying that the hole may have a circular cross section, but by forming the hole to have a long hole cross section (the permanent magnet motor of claim 5), the shape of the magnetic path depending on the shape, It is possible to adjust the state of the magnetic resistance.

[0014]

EXAMPLES Some examples of the present invention will be described below. (1) First Embodiment First, the first embodiment in which the present invention is applied to an outer rotor type motor.
The embodiment (corresponding to claims 1 and 2) will be described with reference to FIGS. 1 and 2.

FIG. 2 shows the overall construction of a permanent magnet type motor 11 according to this embodiment, in which a cylindrical housing 1 is provided in the center of a base 12 made of aluminum, for example.
3 is integrally provided so as to stand up. The stator core 1 is attached to the outer peripheral portion of the housing 13.
4 is fixed by adhesion, for example. As will be described later, the stator core 14 has three teeth portions 15 in this case, and the slots between the teeth portions 15 have three-phase three windings formed by winding, for example, a polyurethane insulated magnet wire. 16 are to be accommodated. A current having a predetermined waveform is supplied to the windings 16 by a control circuit (not shown).

On the other hand, bearings 17, 17 are press-fitted and fixed to the upper and lower ends of the housing 13, respectively.
A shaft 18 made of, for example, stainless steel and extending in the vertical direction is rotatably supported by 17. A rotor 19 is fixed to the shaft 18. This rotor 19
Is, for example, a ferrite magnet having N-poles and S-poles alternately arranged in the circumferential direction on the inner peripheral surface of a rotor yoke 20 formed in a cylindrical container shape whose lower surface is opened from an iron plate, as shown in FIG. The four permanent magnets 21 are fixed to each other by adhesion or the like. The rotor 19 is fixed to the shaft 18 so that the shaft 18 penetrates the center portion of the upper surface of the rotor yoke 20, and the permanent magnet 21 is positioned so as to surround the outer peripheral portion of the stator core 14.

Now, the stator core 14 will be described. The stator core 14 is composed of a laminated iron core made of, for example, a silicon steel plate, and as shown in FIG. 1, is arranged on the outer peripheral portion of the yoke portion 14a fixed to the outer peripheral portion of the housing 13, in this case, at an interval of 120 degrees in the radial direction. It is configured to have three extending teeth portions 15. A magnetic pole portion 15a is provided at the tip end portion (outer peripheral end portion) of each tooth portion 15 so as to expand in the circumferential direction. Each magnetic pole part 15
The outer peripheral edge portion of a has an arc shape so as to come on the same circumference as a whole, and a slight air gap 2 is formed in the permanent magnet 21.
They are facing each other through 2.

Each of the magnetic pole portions 15a is provided with a hole 23 having a circular cross section for limiting the magnetic path through which the magnetic flux passes, at a position slightly away from the outer peripheral edge. In this case,
As shown in FIG. 2, two holes 23 are provided in each magnetic pole part 15a, but on the same circumference with the rotation axis as the center, the radial center line symmetry of each tooth part 15 is shown. In addition, the magnetic pole portions 15a are evenly formed at positions apart from each other by a mechanical angle of 30 degrees (electrical angle of 90 degrees). Also,
In this embodiment, as shown in FIG. 2, the hole 23 is formed so as to penetrate the stator core 14 in the axial direction.

Next, the operation of the above configuration will be described. Like the magnetic pole portion 15a located at the upper left of FIG.
When 1 is directly opposite to the magnetic pole portion 15a, the amount of magnetic flux passing through the magnetic pole portion 15a is maximum.
At this time, as shown by the arrow c, the hole 23 becomes a magnetic resistance and the magnetic path is narrowed accordingly, so that the stator core 1
When the magnetic flux passing through 4 exceeds a certain level, magnetic saturation occurs and the hole 2
The effective amount of magnetic flux is suppressed as compared with the case where 3 does not exist.

Therefore, the rotational torque at the rotational position of the rotor 19 where the maximum magnetic flux is obtained, that is, the maximum rotational torque is suppressed, and as a result, as a whole, compared with the conventional example shown in FIG. The torque fluctuation range can be reduced. Along with this, the hole 23 becomes a magnetic resistance, so that one magnetic pole portion 15a acts as if divided into three parts, a high-frequency state in which the cycle of torque fluctuation is shorter and the rotation of the rotor 19 is cyclic. Less likely to be affected. As a result, it is possible to improve the torque fluctuation and suppress the generation of vibration and noise.

In the present embodiment, unlike the concave portion 6 such as the conventional concave pole structure shown in FIG. 7, the hole 23 has the magnetic pole portion 1.
Since the outer peripheral edge of the magnetic pole portion 15a is connected to the magnetic pole portion 15a, the air gap 22 does not become large. In this case, the rotor 1
Due to the position change of the permanent magnet 21 due to the rotation of 9, magnetic flux passing through the magnetic pole portion 15a is reduced to less than a certain amount and magnetic saturation is eliminated. At this time, the magnetic resistance of the air gap 22 is a concave pole structure. The magnetic efficiency can be improved because it is smaller than

As described above, according to this embodiment, the magnetic pole portion 15
By providing the hole 23 in “a”, unlike the conventional one shown in FIG. 6, it is possible to suppress the torque fluctuation to a small level, and thus suppress the generation of vibration and noise. Moreover, unlike the conventional concave pole structure shown in FIG. 7, it is possible to obtain an excellent effect of suppressing a decrease in motor efficiency.

Further, particularly in this embodiment, the holes 23 are located on the same circumference centered on the rotation axis, and each magnetic pole portion 15a is formed.
Therefore, the magnetic flux distribution can be well balanced. Further, since the holes 23 are provided in a penetrating state, it is possible to obtain an advantage that the holes 23 are easily formed, for example, it is only necessary to stack the same type of silicon steel plates having holes formed therein. It is easy to create and change the working die, for example, by only adding a portion for forming the hole 23 to the press die. Of course, the mechanical strength of the magnetic pole portion 15a is higher than that of the concave pole structure.

(2) Second and Third Embodiments FIG. 3 shows a second embodiment of the present invention. This embodiment differs from the first embodiment in that the magnetic pole portion 1
The point is that the hole 24 formed in 5a is not a circular cross section but an elongated hole having a substantially semicircular cross section. As described above, the cross-sectional shape of the hole can be variously changed, and the form of the magnetic path, that is, the magnetic resistance can be adjusted according to the shape.

FIG. 4 shows a third embodiment of the present invention. In this embodiment, four holes 25 are formed in each magnetic pole portion 15a. In this case, the hole 25
It is provided at a mechanical angle of 15 to 20 degrees and an electrical angle of 45 to 60 degrees. As described above, various modifications can be considered regarding the number and positions of the holes, and the magnetic resistance (balance of magnetic flux distribution) can be adjusted depending on the number and positions of the holes to be formed.

In the above-mentioned first to third embodiments, the number of holes is two and four, but the number of holes may be three, and the influence of passing magnetic flux is too great. Any number is acceptable as long as it does not give.

(3) Fourth Embodiment FIG. 5 shows a fourth embodiment of the present invention. Here, the present invention is applied to an inner rotor type permanent magnet type motor 31 in place of the outer rotor type motor as in the first to third embodiments.

That is, the rotor 3 fixed to the shaft 32
On the outer circumference of 3, the north pole and the south pole are alternately arranged in the circumferential direction.
Individual permanent magnets 34 are provided. On the other hand, the stator core 35 fixed to the inner peripheral surface of the motor frame (not shown)
Is configured to have a large number of teeth portions 36 extending from the inner peripheral portion of the ring-shaped yoke portion toward the center, and the multiphase winding 37 is housed in the slot portion between the teeth portions 36. ing.

A magnetic pole portion 36a is provided at the tip of each tooth portion 36 so as to face the permanent magnet 34 of the rotor 33 through a slight air gap 38. And
In this case, among the magnetic pole portions 36a, every other magnetic pole portion 3
A hole 39 for limiting the magnetic path through which the magnetic flux passes is also provided at a position away from the inner peripheral edge of the central portion of the stator core 35.
Is formed so as to penetrate in the axial direction. Therefore, the tooth portions 36 having no holes 39 are arranged between the tooth portions 36 having the holes 39.

Also in this embodiment, similarly to the first embodiment, the torque fluctuation can be suppressed to a small level, and vibration and noise can be suppressed, and further, the reduction of the motor efficiency can be suppressed. It is possible to obtain excellent effects such as being able to do so. Further, as in the present embodiment, between the teeth portions 36 having the holes 39,
By arranging the teeth portion 36 having no holes 39, the balance of the magnetic flux distribution can be adjusted.

The present invention is not limited to the embodiments described above and shown in the drawings. For example, the holes may have a bottomed hole state which does not penetrate in the axial direction of the stator core. For example, the magnetic resistance can be adjusted according to the depth of the hole, and thus the magnetic resistance can be appropriately changed and implemented within a range not departing from the gist.

[0032]

As is apparent from the above description, according to the permanent magnet type motor of the first aspect of the present invention, the magnetic pole portion of the stator core extends in the axial direction at a position reserved from the peripheral edge facing the rotor. Since the holes are provided, the torque fluctuation can be suppressed to a small level, and further, the deterioration of the efficiency of the motor can be suppressed, which is an excellent practical effect.

In this case, the holes are located on the same circumference with the rotation axis as the center and are arranged substantially evenly on each magnetic pole portion (permanent magnet type motor according to claim 2), whereby the magnetic flux distribution is improved. Good balance can be achieved. Further, among the plurality of tooth portions, the tooth portions having holes and the tooth portions having no holes are arranged at a predetermined pitch (permanent magnet type motor of claim 3) to similarly adjust the balance of the magnetic flux distribution. be able to. Further, it goes without saying that the hole can be formed so as to penetrate in the axial direction of the stator core, but by forming a bottomed hole that does not penetrate in the axial direction of the stator core (a permanent magnet motor according to claim 4). The magnetic resistance can be adjusted according to the depth. Further, it goes without saying that the hole may have a circular cross section, but by forming the hole to have an elongated hole shape (the permanent magnet motor of claim 5), the state of magnetic resistance can be changed according to the shape. It can be adjusted.

[Brief description of drawings]

FIG. 1 is a cross-sectional plan view of a motor showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a motor

FIG. 3 is a diagram corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 4 is a diagram corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 5 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 7 is a view corresponding to FIG. 1 showing another conventional example.

[Explanation of symbols]

In the drawing, 11 and 31 are permanent magnet type motors, 14 and 35 are stator cores, 15 and 36 are tooth portions, and 15a and 36 are shown.
a is a magnetic pole portion, 16 and 37 are windings, 19 and 33 are rotors,
21, 34 are permanent magnets, 22, 38 are air gaps, 2
3, 24, 25 and 39 show holes.

Claims (5)

[Claims] 1. A magnetic pole part of a stator core having a plurality of phase windings, wherein magnetic pole parts at tips of a plurality of teeth are arranged to face a rotor having a permanent magnet via an air gap. A permanent magnet type motor, characterized in that a hole extending in the axial direction is provided at a position confined from the peripheral edge facing the rotor. 2. The hole is located on the same circumference centered on the rotation axis, and is provided so as to be substantially evenly arranged on each of the magnetic pole portions. Permanent magnet type motor. 3. The permanent magnet type motor according to claim 1, wherein among the plurality of tooth portions, the tooth portions having the holes and the tooth portions having no holes are arranged at a predetermined pitch. 4. The permanent magnet motor according to claim 1, wherein the hole is formed in a bottomed hole state that does not penetrate in the axial direction of the stator core. 5. The permanent magnet motor according to claim 1, wherein the hole is formed in a long hole shape in cross section.