JPH05103453A - Salient-pole brushless dc motor - Google Patents

Abstract

PURPOSE:To reduce the vibration during rotation and the noise accompanying the vibration by making a hole, which partially weakens the magnetic flux at the gap part between a stator and a salient pole, in the position equivalent to the specific angle in terms of the electric angle of the salient pole of a rotor. CONSTITUTION:Holes 5a and 5b are bored in the positions equivalent to 60 deg. and 120 deg. (mechanically 30 deg. and 60 deg.) in terms of the electric angles of the salient pole 5 of a rotor 2. Moreover, similarly holes 6a and 6b, 7a and 7b, and 8a and 8b are bored in the salient poles 6, 7, and 8, respectively. Hereupon, these holes 5a and 5b, 6a and 6b, 7a and 7b, and 8a and 8b partially decrease the magnetic flux in the gap part between the stator 1 and the salient poles 5-8. Hereby, the magnetic flux at the section, which were the peak position of torque ripple in the past, can be lessened, so nearly fixed composite torque can be gotten, and the vibration at rotation of the rotor and the noise accompanying the vibration can be reduced.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a salient pole type brushless DC motor used for a compressor driving motor of a refrigerator or an air conditioner.

[0002]

2. Description of the Related Art In recent years, salient-pole brushless DC motors whose rotation speed can be easily controlled are generally used as drive motors for compressors of refrigerators and air conditioners. Hereinafter, a salient pole type brushless DC motor which is generally used at present will be described with reference to FIGS. 6 to 9.

Reference numeral 21 in FIG. 6 denotes a stator, and this stator 2
In FIG. 1, twelve semi-closed slots 21a having openings 21b on the inner peripheral surface side are formed on the circumference at equal intervals, and these semi-closed slots 21a are formed with 6 slots as shown in the figure. Stator coils 23u, 23v, 23w, 24
u, 24v, 24w are stored. The six stator coils 23u to 24w are configured to be supplied with a three-phase DC exciting current, and the stator coils 23u and 24u are U-phase and the stator coils 23v and 2w.
The V phase corresponds to 4v, and the W phase corresponds to the stator coils 23w and 24w.

Reference numeral 22 denotes a rotor, which has a rotating shaft 33 at the central position as shown in FIG. And the rotating shaft 33
Peripheral magnets 29, 30, 31, 32 for field magnets are arranged so as to surround the rotating shaft 33 in a substantially square shape. Of the field permanent magnets 29 to 32, the field permanent magnets 29 and 31 facing each other are magnetized to the N pole, and the other field permanent magnets 30 and 32 facing each other are S.
It is magnetized to the pole. The salient pole portions 25, 26, 27, 28 are arranged so as to be orthogonal to each other on the outer side in the radial direction of each of the field permanent magnets 29 to 32. The salient pole portions 25 and 27 are magnetized to the N pole and the salient pole portions 26 and 28 are magnetized to the S pole in correspondence with the field magnets 29 to 32.

In the salient pole type brushless DC motor having the above-mentioned structure, the drive unit (not shown) supplies two phases to U-phase, V-phase and W-phase corresponding to each stator coil 23u to 24w of the stator 21. 120 electrical phase in the prescribed order phase by phase
The rotor 22 is rotationally driven by the magnetic attractive force and repulsive force generated by energizing the rotor 22.

Next, the magnetic flux distribution in the air gap between the stator 21 and the salient pole portions 25 to 28 of the rotor 22 has a sinusoidal shape with respect to the electrical angle, as indicated by the solid line 1 in FIG. is doing. On the other hand, a DC exciting current is applied to each of the stator coils 23u to 24w, and each phase generates a substantially constant magnetic flux. Therefore, the torque generated corresponding to each of the three phases becomes proportional to the intensity of the magnetic flux distribution in the void portion, and the solid line 1 is equivalently equivalent to each of the U phase, V phase, and W phase. , Two-dot chain line m and broken line n. As a result, when the stator coils 23u to 24w are energized by two phases each having an electrical angle of 120 degrees, the combined torque generated in the rotor 5 has a wavy torque ripple as shown in FIG. ..

[0007]

In the salient pole type brushless DC motor having the above-mentioned structure, the combined torque is accompanied by the wavy torque ripple as shown in FIG. As a result, vibrations and noises due to the vibrations are generated, which causes problems when used in a compressor of a refrigerator or an air conditioner. [Constitution of Invention]

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problems, and a stator having a stator coil having a plurality of phases and a permanent magnet continuously and alternately provide N. And a rotor having salient poles magnetized so as to have S poles, and the salient pole type brushless DC motor is rotationally driven by sequentially energizing two adjacent stator coils. Holes for partially weakening the magnetic flux in the void portion between the stator and the salient pole portion are formed at positions corresponding to 60 and 120 degrees in electrical angle of each salient pole portion. And a salient pole type brushless DC motor.

[0009]

According to the present invention, the magnetic flux in the gap between the stator and the salient pole portion of the rotor is provided at a position corresponding to an electrical angle of each salient pole portion of 60 degrees and 120 degrees. Since the holes are partially weakened, the torque ripple part, which had peaked in the past, was weakened in the three-phase combined torque, resulting in vibration during rotation and noise accompanying vibration. Is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention applied to a three-phase four-pole salient-pole brushless DC motor is shown in FIG.
It will be described with reference to FIGS.

First of all, as shown in FIG. 1, the entire structure has an annular stator 1, and the stator 1 has a semi-closed slot 1a having an opening 1b on the inner peripheral surface side. For example, 12 pieces are formed at equal intervals. Then, as shown in the figure, the six stator coils 3u, 3v, 3w, 4
u, 4v and 4w are housed and arranged in a predetermined semi-closed slot 1a. Then, these stator coils 3u to 4
w is configured so as to be supplied with a three-phase DC exciting current. U-phase is applied to the stator coils 3u and 4u, V-phase is applied to the stator coils 3v and 4v, and stator coils 3w and 4w are applied to the stator coils 3w and 4w. Corresponds to the W phase.

A rotor 2 is arranged inside the concentric circle of the stator 1, and the rotor 2 is fitted to a rotary shaft 13 at a center position as shown in FIG. Field permanent magnets 9, 10, 11, 12 are fixed to the rotor 2 so as to surround the rotating shaft 13 in a substantially square shape. Of these field permanent magnets 9 to 12, the field permanent magnets 9 and 11 arranged at positions facing each other are magnetized to, for example, N poles, and the other field permanent magnets facing each other. 10 and 12 are magnetized to the S pole. Salient pole portions 5, 6, 7 and 8 are formed on the outer sides of the field permanent magnets 9 to 12 in the radial direction. Of these salient pole portions 5 to 8, the salient pole portions 5, 7 and salient pole portions are formed. Nos. 6 and 8 face each other and are in a direct state. The salient poles 5 and 8 are magnetized to the N pole by the corresponding field permanent magnets 9 to 12, and the salient poles 6 and 8 are magnetized to the S pole. Has been done.

Two holes 5a and 5b are bored in the salient pole portion 5, and these holes 5a and 5b are provided at positions corresponding to electrical angles of 60 degrees and 120 degrees. In this embodiment, since a four-pole brushless DC motor is described, mechanically, each salient pole portion has a degree of 30 degrees and 60 degrees.
Holes 5a and 5b are drilled at positions corresponding to degrees. These holes 5a and 5b are formed by the salient pole portions 5 of the stator 1 and the rotor 2.
This has the effect of partially reducing the magnetic flux of the magnetic flux distribution in the gap portion between and. Further, in the salient pole portions 6, 7 and 8 as well as the holes 5a and 5b formed in the salient pole portion 5 described above, the electrical angle is 60 degrees and 120 degrees.
Holes 6a, 6b, 7a, 7b and 8a, 8b are drilled at positions corresponding to degrees (mechanically 30 degrees and 60 degrees).

Next, the electrical construction of the salient pole type brushless DC motor in this embodiment will be described with reference to FIG. Reference numeral 15 is a DC power supply, and a switching main circuit 16 is connected to the DC power supply 15. The switching main circuit 16 has six pairs of transistors 17 and diodes 18, and these six pairs of transistors 17 and diodes 18 are three-phase bridge-connected and have three-phase arm portions 16u and 16v. The common connection point of the transistor 17 included in each of 16 and 16w is connected to the output line corresponding to the U phase, the V phase, and the W phase, respectively. The output lines corresponding to the U-phase, V-phase, and W-phase are connected to the respective terminals in which the stator coils 3u and 4u and 3v and 4v and 3w and 4w are Y-connected. Reference numeral 19 is a control circuit for giving a control signal to each transistor 17 arranged in the switching main circuit 16, and includes stator coils 3u, 4u and 3u.
Corresponding to the stator coils for two adjacent phases of v, 4v and 3w, 4w, the phases are shifted by 120 degrees in terms of electrical angle and the current is supplied. In addition, this control circuit 19
Is also connected to each output line corresponding to U-phase, V-phase and W-phase, and the stator coils 3u to 4w are rotated by the rotation of the rotor 2.
By detecting the induced voltage, a motor drive signal corresponding to the rotational position of the rotor 2 can be obtained.

The operation and action of this embodiment will be described below with reference to FIGS. 4 and 5. First, the control circuit 1
A control signal is supplied to the six transistors 17 provided in the switching main circuit 16 by means of 9. When a control signal is supplied to the transistor 17, the stator coil 3u
2 to 4w adjacent two-phase stator coils (for example, 3
u, 4u and 3v, 4v) are energized, and hereinafter, stator coils 3v, 4v and 3w, 4w, stator coils 3w, 4
As shown in w and 3u, 4u, ..., the electrical angle is sequentially turned on for 120 degrees. Thus, when the stator coils 3u to 4w are sequentially energized, a rotating magnetic field is generated by the stator 1,
The rotor 2 starts to rotate by a magnetic attraction force and a repulsive force. At this time, the torque generated in the rotor 2 has a small torque ripple as described below. That is, between the stator 1 and the salient pole portions 5 to 8 of the rotor 2 by the holes 5a to 8b drilled at positions corresponding to the electrical angles of the salient pole portions 5 to 8 of 60 degrees and 120 degrees. The magnetic flux of the magnetic flux distribution in the void part is 60 degrees, 120 degrees, 240 degrees, 300 degrees in a sine wave shape as shown in FIG.
Since a portion having a small magnetic flux is generated at a position corresponding to the degree, the torque received from each of the three phases also follows the magnetic flux shown in FIG. In this way, the peak position of the torque ripple in the past was 60 °, 120 °, 2
Since it has become possible to reduce the torque of a portion such as 40 degrees and 300 degrees (electrical angle), the torque as a whole can generate a substantially constant torque as shown by a solid line K in FIG. It is a thing. With the combined torque obtained in this way, it is possible to reduce the vibration generated when the rotor 2 rotates and the generation of noise accompanying the vibration.

In the above embodiment, the case where the present invention is applied to a three-phase four-pole salient pole type brushless DC motor has been described, but the present invention is not limited to this shape, and salient pole type. A brushless DC motor can be variously modified and implemented.

[0017]

According to the salient pole type brushless DC motor of the present invention, it is possible to reduce the magnetic flux at the portion where the peak position of the torque ripple is conventionally, and as a result,
Since it is possible to obtain a substantially constant combined torque, it is possible to reduce vibration during rotation of the rotor and noise accompanying the vibration.

[Brief description of drawings]

FIG. 1 is an overall view of a salient pole type brushless DC motor of the present invention.

FIG. 2 is an enlarged view of the rotor in FIG.

FIG. 3 is an electrical configuration diagram of a salient pole type brushless DC motor.

FIG. 4 is a diagram showing a magnetic flux distribution according to the present invention.

FIG. 5 is a diagram showing a synthetic torque obtained by the present invention.

FIG. 6 is an overall view of a conventional salient pole type brushless DC motor.

FIG. 7 is an enlarged view of the rotor in FIG. 6

FIG. 8 is a diagram showing a conventional magnetic flux distribution.

FIG. 9 is a diagram showing a synthetic torque that has been conventionally obtained.

[Explanation of symbols]

 1 Stator 2 Rotor 3u, 3v, 3w, 4u, 4v, 4w Stator coil 5, 6, 7, 8 Salient pole part 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b Hole 9,10, 11, 12 Permanent magnet for disclosure

Claims (1)

[Claims] 1. A stator having stator coils of a plurality of phases,
A rotor having salient poles magnetized so as to become N poles and S poles continuously and alternately by permanent magnets, and is driven to rotate by sequentially energizing two adjacent stator coils. In the salient pole type brushless DC motor, the magnetic flux in the air gap portion between the stator and the salient pole portion is partially located at positions corresponding to 60 electrical degrees and 120 electrical degrees of the respective salient pole portions. A salient pole type brushless DC motor having a hole for weakening.