JPH0556617A - Stator for synchronous motor - Google Patents

Abstract

PURPOSE:To provide a stator for a synchronous motor in which a cogging torque can be reduced by extremely easy means irrespective of the number of slots and the winding shape of the stator. CONSTITUTION:This stator 20 has six slots 18 for mounting windings 22 to surround a rotor 16 for constituting eight poles of a yoke 14 between permanent magnets 12 which are radially disposed. Upper and lower layer windings 22 are contained in the slots 18. The stator 20 has radially engraved cutouts at positions deviated by 1/4 of an angle of a slot pitch from the centers of the ends of teeth in the same direction at the end faces of the thirty-six protruding teeth 24 formed of the slots 18. The cutouts act similarly to the openings of the slots for a magnetic flux generated from the rotor 16 to generate a disorder in a sine waveform of a magnetic flux distribution in the air gap between the rotor 16 and the stator 20, thereby dispersing the energy of a cogging torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved stator structure for improving the smoothness of rotation of a synchronous motor, and more particularly,
In order to reduce the cogging torque that is inevitably generated from the disturbance of the magnetic flux distribution due to the slot opening that is essential for winding installation on the stator peripheral surface facing the rotor, the tooth tip surface of the stator peripheral surface is reduced. The present invention relates to a stator of a synchronous motor provided with a notch for compensating for disturbance of magnetic flux distribution.

[0002]

2. Description of the Related Art During the rotation of a synchronous motor (hereinafter, simply referred to as a synchronous motor), the torque is usually proportional to the number of teeth of the stator core, that is, the number of slots essentially provided in the stator core for installing windings. , The so-called cogging torque is generated. This cogging torque has a slot opening on the circumferential surface of the stator facing the rotor, so that the magnetic path of the field magnetic flux generated from the magnetic pole of the rotor when the rotor and the stator move relative to each other is This is due to the fact that the magnetic pole periodically changes every time it crosses, and the magnetic flux distribution in the air gap between the rotor and the stator is disturbed.

Therefore, the period and magnitude of this cogging torque depend on the number of slots provided in the stator core. It is generally known that the smaller the cycle, the smaller the size. Therefore, it is considered that the cogging torque can be reduced by increasing the number of slots. However, the number of slots of the stator core is necessarily determined by the number of magnetic poles of the rotor, the number of phases of the motor, the winding form, etc., and increasing the number of slots inevitably complicates the stator structure. ..

For example, in a three-phase AC drive synchronous motor, in order to provide a single-layer winding on the stator for an M pole motor having M rotor permanent magnets, at least three windings are required.
M slots, or a natural number multiple of 3 nM slots are required. When the stator core is provided with 3M slots, each phase (U phase, V
Phase, W phase) three slots containing the windings face each other,
The winding is configured to make one turn for two poles (that is, one pole pair of N pole and S pole). At this time, the polarities of the currents flowing in the windings of one coil are opposite in polarity to the adjacent N and S poles of the rotor one pole pair, and therefore the torque exerted on these one pole pairs is in the same direction. To work. The same applies to the cogging torque generated by the existence of the slot opening. In the case of the above configuration, since the cogging torque is generated in synchronization between the N pole and the S pole in the rotor one pole pair, the magnitude thereof is twice as large as one cogging torque, which is extremely large as a whole. In this case, simply set the number of slots to 3
The synchronism of the cogging torque cannot be eliminated only by increasing the number to nM.

Therefore, by making the winding form of the stator multi-layered and making the number of slots corresponding to one pole of the rotor non-integer, the generation of cogging torque is synchronized between the N pole and the S pole in one pole pair of the rotor. A stator that is not used is generally adopted. FIG. 6 shows an example of a synchronous motor equipped with this type of stator. The synchronous motor shown in FIG. 6 includes a rotor 4 having eight magnetic poles composed of eight permanent magnets 2 arranged radially around the output shaft 1 and yokes 3 arranged between the permanent magnets 2. , A stator 6 having 36 slots 5 surrounding the rotor 4. Therefore, in this motor, 4.5 slots 5 correspond to one pole of the rotor 4. The upper and lower two layers of windings 7 are accommodated in each slot 5, and the windings 7 are arranged at a total of 18 positions within the nine slots 5 for the two poles (one pole pair) of the rotor 4. .. Therefore, each of the three-phase windings 7 makes one round with two poles (one pole pair) of the rotor 4 to form three coils, respectively. The outer peripheral surface of the yoke 3 of the rotor 4 is shaped so that the magnetic flux generated from the rotor 4 exhibits a substantially sinusoidal waveform if the inner peripheral surface of the stator 6 has no opening by the slot 5.

In such a structure, the rotor 4 is actually
The magnetic flux generated from the sine wave is disturbed in the sine waveform due to the opening 8 of the slot 5, and this causes the cogging torque. The magnetic flux distribution at this time is conceptually shown in FIG. Figure 7
Is predicted when the magnetic pole, that is, the outer peripheral surface of the yoke 3 is scanned to measure the magnetic flux distribution when the rotor 4 is stationary, and the corrugated concave portion 9 that causes cogging torque is characteristically shown. There is. If the corrugated concave portion 9, that is, cogging torque is generated when the left edge of each magnetic pole crosses the slot opening, one magnetic pole corresponds to 9 slots (2 poles, that is, electrical angle 360 °, mechanical angle 90 °). Nine cogging torques occur regularly (one for every 40 ° electrical angle) during rotation. In this motor, as shown,
The cogging torque is not generated synchronously between the north pole and the south pole of the one pole pair of the rotor 4, and the cogging torque is generated with a shift of 1/2 pitch of the slot 5. Therefore, the number of times the cogging torque is generated is 18 times while rotating for one pole pair, and is twice the number of slots per one rotation of the rotor, that is, 72 times (1 per 20 ° electrical angle).
Therefore, the magnitude of the cogging torque per turn is smaller than that of the above-described single layer winding structure.

[0007]

As described above, by making the number of slots facing one pole of the rotor non-integer, it is possible to prevent the cogging torque from synchronizing with one pole pair and reduce its size as a whole. Can be made However, the number of slots formed in the stator is inevitably limited by the number of poles of the rotor as described above, and it is clear that this method alone has a limit in reducing the cogging torque.

The present invention has been devised and devised to solve such problems, and its purpose is extremely easy regardless of the number of slots of the stator and the form of winding. Another object of the present invention is to provide a stator of a synchronous motor capable of reducing the magnitude of cogging torque by various means.

[0009]

In order to achieve the above object, the present invention is directed to a plurality of substantially identically-shaped protruding teeth facing each other with a gap in a magnetic pole of a rotor and having substantially the same width between these protruding teeth. And a plurality of slots for installing windings formed on each of the plurality of toothed teeth, the notch having a predetermined width extending in the radial direction with respect to the center of rotation of the motor is provided at the same position on each tooth tip surface of the plurality of toothed teeth. Provided is a stator for a synchronous motor, which is configured to disperse and compensate for the disturbance of the magnetic flux distribution in the air gap.

According to a preferred embodiment of the present invention, the notch is formed on the tooth crests of the plurality of protruding teeth in the same direction from the center position of the tooth crests by 1/4 of the pitch angle of the slot. A synchronous motor stator is provided that is formed at offset positions. Alternatively, the notch can be formed at the center position of the tooth crest surface. The width of the notch may be smaller than the width of the opening of the slot.

[0011]

The notch formed in each tooth tip surface of the plurality of projecting teeth of the stator acts on the field magnetic flux generated from the magnetic pole of the rotor in the same manner as the opening of the slot when the rotor rotates.
The sinusoidal waveform of the magnetic flux is disturbed, that is, a corrugated concave portion is generated. This corrugated concave portion occurs before and after the corrugated concave portion generated by the slot opening, whereby the cogging torque caused by the corrugated concave portion is compensated from the local concentration characteristic to the multipoint dispersion characteristic, and therefore, per one time. The magnitude (peak value) of the cogging torque is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 are sectional views showing a synchronous motor having a stator according to an embodiment of the present invention. The synchronous motor of FIG. 1 has 8 poles and 3 poles like the motor of FIG.
It has 6 slots. Therefore, in this synchronous motor, eight permanent magnets 12 are arranged radially around the output shaft 10 and a yoke 16 disposed between the permanent magnets 12 forms eight magnetic poles. And a stator 20 according to an embodiment of the invention having 36 slots 18 surrounding the. Each slot 18 also accommodates windings 22 in the upper and lower layers, and for two poles (one pole pair) of the rotor 16, a total of 18 slots are provided in the nine slots 18.
The winding wire 22 is arranged at the location.

A stator 20 according to an embodiment of the present invention, as shown in detail in FIG. 2, has 36 protruding teeth 24 formed by a surface facing the rotor 16, that is, a slot 18.
In each tooth tip surface 26 of No. 28, a notch 28 formed in the radial direction at an intermediate position between the tooth tip center and the slot center, that is, a position deviated from the slot center in the same direction by 1/4 of the slot pitch angle. Have. Cutout 28
Has a width slightly smaller than the slot opening 30,
Slot opening 30 is provided for the magnetic flux generated from rotor 16.
Acts in the same manner as the above, and causes the sine waveform of the magnetic flux to be disturbed. The state of the magnetic flux at this time is conceptually shown in FIG. 3, which is a view similar to FIG. 7. Comparing FIG. 3 with FIG. 7, it can be seen that the slot opening 30 generated during the magnetic flux distribution for one period is 9
It can be seen that nine corrugated recesses 34 due to the notches 28 are formed in the vicinity of each of the corrugated recesses 32 (corresponding to the corrugated recess 9 in FIG. 7). At this time, since the position of the notch 28 is displaced from the center of the slot in one direction by ¼ of the slot pitch angle, a total of 18 corrugated recesses 32 and 34 are formed at the same time for one pole pair of the rotor. It does not occur, and it occurs regularly. As can be seen from the above description, therefore, the number of corrugated recesses 32, 34 per one rotation of the motor, that is, the total number of times of cogging torque is 144 times which is four times the number of slots (once in 10 ° electrical angle), As compared with the conventional synchronous motor shown in FIG. 6, the magnitude of one cogging torque can be further reduced.

The manner in which such a waved concave portion, that is, the cogging torque is generated will be described in more detail with reference to FIG.
FIG. 4 shows the teeth 24 of the stator 20 and the yoke 1 of the rotor 16.
4 shows the relative positional relationship with the rotor 4 according to the rotation of the rotor 16. Pay attention to the left edges of one pole (N pole) 14a of the yoke 14 and the adjacent pole (S pole) 14b, and when these left edges cross the front of the slot opening 30 and the notch 28. , And that cogging torque is generated respectively. In the first state, the left edge of the N pole 14a faces the center of the slot opening 30. At this time, cogging torque due to the slot opening 30 is generated. Next, when the rotor 16 is rotated by a quarter slot pitch angle, that is, by a mechanical angle of 2.5 ° (electrical angle of 10 °),
The left edge of the N pole 14a faces the center of the cutout 28, and at this time, cogging torque due to the cutout 28 is generated. When the rotor 16 further rotates by a quarter slot pitch angle, in this state, the left edge of the S pole 14b now faces the center of the slot opening 30, and again the slot opening 3
Cogging torque due to zero is generated. When the rotor 16 further rotates a quarter slot pitch angle,
In this state, the left edge of the S pole 14b faces the center of the cutout 28, and cogging torque due to the cutout 28 is generated. In this manner, a total of four cogging torques are generated while the rotor 16 rotates by one slot pitch angle (mechanical angle 10 °, electrical angle 40 °).

The size (amplitude) of the corrugated recesses 32 and 34 is such that the width and depth of the notch 28 are the slot openings 3.
Since it is smaller than that of 0, the corrugated recess 34 is actually smaller. However, since the energy of the cogging torque is dispersed by the generation of the corrugated recess 34 to the place where only the corrugated recess 32 is originally generated, that is, the cogging torque is compensated from the local concentration characteristic to the multipoint dispersion characteristic. As described above, the magnitude of the cogging torque per operation is reduced.

The improvement result of the cogging torque of the synchronous motor using the stator 20 according to this embodiment will be described below based on the measured data obtained by the experiment. This measured data is displayed by the graph shown in FIG. Figure 5 (a)
FIG. 5 relates to a motor using the conventional stator of FIG.
(B) relates to a motor using the stator 20 according to the present embodiment of FIG. In each of these graphs, the vertical axis represents the difference between the command position and the actual operating position with respect to the output shaft of the motor, that is, the position deviation converted into a predetermined reference value (1 division 1 div). The horizontal axis represents the rotation angle of the rotor, and in this case, the change in position deviation corresponding to the electrical angle of 360 ° (one pole pair). The position deviation described here is synonymous with vibration and indicates a variation in the operation of the motor output shaft due to the cogging torque of the synchronous motor. Therefore, FIG.
One peak in (a) corresponds to the corrugated recess 9 in FIG. 7,
One peak in FIG. 5B corresponds to the corrugated recesses 32 and 34 in FIG. As is apparent from the figure, the amplitude of the position deviation in the motor using the stator 20 according to this embodiment is smaller than that of the conventional one. The maximum deviation between the peak and the valley of the amplitude is 8.7 div in (a), (b)
It is 5.7 div. Further, in FIG. 5 (b), it can be easily understood that the top of the large peak is crushed into a saw shape, but this is due to the small corrugated recess 34 described above.

In the above embodiment, the present invention has 8 poles and 36 poles.
The case where the present invention is applied to a synchronous motor having a slot has been described, but the present invention is not limited to this, and can also be applied to, for example, the M pole 3M slot synchronous motor described at the beginning. In this case, the notches may be formed at the center positions of the tooth crests of the 3M protruding teeth formed on the stator, that is, at the positions displaced by the 1/2 slot pitch angle. Alternatively, three notches can be formed for each 1/4 slot pitch angle for each tooth tip surface, in which case the effect of reducing the cogging torque is further increased.

[0018]

As described above, according to the present invention, a plurality of notches having a predetermined width extending in the radial direction are formed at the same positions on the tooth crest surfaces of a plurality of substantially identical protruding teeth facing the magnetic poles of the rotor. , These notches act on the magnetic field flux generated from the magnetic pole of the rotor in the same manner as the opening of the slot when the rotor rotates, and further disturb the sinusoidal waveform of the magnetic flux, which causes local cogging torque. Since the concentration of the cogging torque per one time is reduced by correcting the concentrated characteristics to the multi-point dispersion characteristics and dispersing the energy into a large number, regardless of the number of slots of the stator or the form of the winding. The magnitude of the cogging torque can be reduced by an extremely easy means, and the operation accuracy of the synchronous motor can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a synchronous motor including a stator according to an exemplary embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the motor shown in FIG.

FIG. 3 is a diagram showing a magnetic flux distribution in a gap between a stator and a rotor of the motor shown in FIG.

4 is a diagram showing the relative positional relationship between the projecting teeth of the stator and the magnetic poles of the rotor of the motor of FIG.

5A and 5B are views showing experimentally the positional deviation of the motor output shaft, and are views relating to (a) a conventional motor and (b) a motor including a stator according to the embodiment of the present invention in FIG. 1.

FIG. 6 is a sectional view of a synchronous motor including a conventional stator.

7 is a diagram showing a magnetic flux distribution in a gap between a stator and a rotor of the motor shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Output shaft 12 ... Permanent magnet 14 ... Yoke 16 ... Rotor 18 ... Slot 20 ... Stator 22 ... Winding 24 ... Cog teeth 26 ... Tooth surface 28 ... Notch 30 ... Slot opening 32, 34 ... Corrugated recess

Claims (4)

[Claims] 1. A rotor magnetic pole is provided with a plurality of protruding teeth of substantially the same shape having a gap and facing each other, and a plurality of slots for winding installation formed between these protruding teeth and having substantially the same width. In the stator of the synchronous motor, cutouts of a predetermined width extending in the radial direction with respect to the center of rotation of the electric motor are provided at the same positions on the tooth crests of the plurality of protruding teeth to disperse and correct the disturbance of the magnetic flux distribution in the air gap. A stator of a synchronous motor having the above-mentioned configuration. 2. The notch is formed on a tooth crest surface of the plurality of protruding teeth at a position displaced from a center position of the tooth crest surface in the same direction by ¼ of a pitch angle of the slot. 1. The stator of the synchronous motor described in 1. 3. The cutout is formed on a tooth top surface of the plurality of protruding teeth at a center position of the tooth top surface.
The stator of the described synchronous motor. 4. The stator for a synchronous motor according to claim 1, wherein the width of the notch is smaller than the width of the opening of the slot.