JPH0345982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless motor, and more particularly to a brushless motor equipped with a stator having large teeth and small teeth.

[Problems to be solved by conventional technology and invention]

A conventional brushless motor has a structure as shown in FIG. 6, for example. Referring to Figure 6,
The illustrated motor has a rotor a and a stator b disposed inside the rotor a. Rotor a
As shown in the figure, the inner circumference of
The magnets are alternately magnetized in order of N pole, S pole, N pole, and S pole. Further, the stator b has six slots c arranged at substantially equal pitches in the circumferential direction, and a coil d is wound between these slots c. That is, the coil d is wound around six teeth e defined by the slot c. Furthermore, this motor has 3
It is a phase motor and has three coils d, but the sixth
In the figure, only the coil for one phase is shown.

In this type of motor, the current shown in Fig. 9 is applied to the first phase coil d, the current shown in Fig. 9 is applied to the second phase coil d, and the current shown in Fig. 9 is applied to the third phase coil d. d. FIG. 7 shows the back electromotive force waveform of each coil d, the solid line waveform is the back electromotive force waveform of the first phase coil d, and the waveform of the two-dot chain line is the back electromotive force waveform of the second phase coil d. The broken line waveform is the back electromotive force waveform of the third phase coil d. Therefore, each coil d in the motor of FIG.
When the current shown in FIG. 9 is supplied to the rotor, the combined torque waveform of the three phases becomes as shown in FIG. 8, and the rotor a is rotationally driven in a predetermined direction by this combined torque.

In this type of motor, in order to make the rotation smooth and increase the rotational force per unit current and unit number of turns, it is important to increase the back electromotive force. However, in the motor shown in Fig. 6, the pitch angle of the coil wound around the tooth e exceeds π radians in effective electrical angle, and therefore unnecessary magnetic flux flows into the tooth e, resulting in an inefficient decreases,
It is not possible to obtain a large back electromotive force.

An object of the present invention is to provide a brushless motor that can increase the back electromotive force generated in the motor to obtain a large rotational driving force.

[Means to solve the problem]

The brushless motor according to the present invention includes a stator that has large teeth arranged at equal pitches in the circumferential direction and small teeth arranged between the large teeth, and a stator that is arranged opposite to the stator and rotates in a predetermined direction. a rotor to be driven; a coil winding block in which a large-tooth winding coil portion and a small-tooth winding coil portion are arranged at point-symmetrical positions;
and the number of magnetic poles of the rotor is set to be larger than the number of the large teeth; the effective pitch angle of the large tooth wound coil portion wound around the large teeth is It is π radian in electrical angle; the pitch angle of the small tooth wound coil portion wound around the small teeth is as follows: N is the total number of teeth of the large teeth and small teeth, and the number of magnetic pole pairs of the rotor is When P, the effective electrical angle is (2P−
N/2)×2π/N radians.

[Effect]

In a brushless motor with such a configuration, the pitch angle α of the coil wound around the large teeth is determined by the effective electrical angle π.
Since the diameter is radian, the efficiency can be substantially maximized by preventing unnecessary magnetic flux from flowing into such large teeth. In addition, small teeth are provided between the large teeth, and the pitch angle β of the coil wound around the small teeth is set to (2P-N/2) x 2π/N radians in effective electrical angle. Space also greatly contributes to the generation of back electromotive force due to small teeth. Therefore, the back electromotive force generated by the motor as a whole becomes much larger than before, and a large rotational torque can be obtained, and the electromotive force at the switching point of each phase also becomes larger than before.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brushless motor according to the present invention will be described below with reference to FIGS. 1 to 5.

In FIG. 1, a brushless motor, generally designated by the number 1, includes a rotor 2 and a stator 3 disposed within the rotor 2. As shown in FIG. The rotor 2 has N poles, S poles, N poles, S poles, and
The poles are sequentially and alternately magnetized, making a total of 8 poles. Therefore, in the embodiment, the number N of magnetic pole pairs of the rotor 2 is four.

In addition, the stator 3 has six slot pairs 4a, 4b, 4 spaced apart in the circumferential direction at every 60 degree central angle.
c, 4d, 4e and 4f are provided, and six large teeth 5 are provided by these slot pairs 4a to 4f.
a, 5b, 5c, 5d, 5e and 5f are defined. The free ends of these large teeth 5a to 5f are
It is located close to and facing the inner peripheral surface of the rotor 2. Further, between each slot pair 4a to 4f, there are small teeth 6a,
6b, 6c, 6d, 6e and 6f are arranged. As is clear from FIG. 1, these small teeth 6a to 6f are arranged substantially in the center in the circumferential direction between adjacent large teeth 5a to 5f, and their free ends also closely face the inner circumferential surface of the rotor 2. It is well located.

The illustrated motor is a three-phase motor, and the coils of each phase are wound around large teeth 5a to 5f and small teeth 6a to 6f as follows. That is, as shown in FIG. 1, the first phase coil 7 is wound around the large teeth 5a, small teeth 6b, large teeth 5d, and small teeth 6e all in the same direction. Further, the second phase coil (not shown) has large teeth 5b and small teeth 6 as in the first phase.
c, the large tooth 5e and the small tooth 6f are all wound in the same direction, and the third phase coil (not shown) is similarly wound around the large tooth 5c, the small tooth 6d, the large tooth 5f, and the small tooth 6a. wrapped in the direction. In other words, the coil winding block includes a plurality of coil winding blocks that are wound around large teeth and small teeth so as to have a point-symmetrical positional relationship. The coils of each phase are sequentially energized in accordance with the rotational position of the rotor 2 as described below, thereby causing the rotor 2 to rotate in a predetermined direction. Incidentally, a rotor position detecting means (not shown) such as a Hall element is disposed near the rotor 2, and a current to the coil 7 is commutated by a signal from the rotor position detecting means.

In the motor of the embodiment, in order to increase the back electromotive force, in the coil 7, the pitch angle α of the large tooth wound coil portion wound around each of the large teeth 5a to 5f and the pitch angle α of the large tooth wound coil portion wound around each of the small teeth 6a to 6f are set. The pitch angle β of the wound coil portion with small teeth is set as follows.

Regarding the large teeth 5a to 5f, the pitch angle α of the coil 7 wound around them is set to substantially π radians in terms of effective electrical angle. When the pitch angle α is made larger than the effective electrical angle π radian, as explained in the prior art, the amount of unnecessary magnetic flux flowing in increases and the efficiency decreases. When the angle is made smaller than π radian, the overlapping area between the magnetic pole and the large tooth becomes smaller,
Effective magnetic flux inflow is reduced and efficiency is reduced. Therefore, for the large teeth 5a to 5f, the efficiency is substantially maximized by setting the pitch angle α to substantially π radians in terms of effective electrical angle.
A large back electromotive force can be obtained.

Further, regarding the small teeth 6a to 6f, the pitch angle β of the coil 7 wound around them is set to approximately π/3 radian in terms of effective electrical angle. This pitch angle β will be explained in detail. If the pitch angle α of the large teeth 5a to 5f is set to substantially π radians in terms of effective electrical angle, the number of magnetic poles of the rotor 2 is greater than the number of large teeth 5a to 5f, as in the embodiment, and the surrounding area of the stator 3 is , the area where the large teeth 5a to 5f do not exist is an effective electrical angle of [2π×(2P-N/2)] radians (P: number of magnetic pole pairs of the rotor 2, N: large teeth 5
a to 5f and small teeth 6a to 6f), and if only large teeth 5a to 5f exist, the back electromotive force of the motor as a whole becomes small due to the existence of the above regions. On the other hand, in the motor of the embodiment, the pitch angle β is set to the effective electrical angle [(2P−
N/2)×2π/N] set in radians,
As in the embodiment, when the number of magnetic pole pairs P=4 and the total number of large and small teeth N=12, the pitch angle β becomes an effective electrical angle of substantially π/3 radian. In the embodiment, when the pitch angle β is made smaller than π/3 in effective electrical angle, the small teeth 6a to 6f
The area where the magnetic flux is present becomes smaller, which reduces the effective inflow of magnetic flux and reduces efficiency. In this way, the small teeth 6a to 6f are provided, and the pitch angle β of these coils is set to an effective electrical angle of π/3 radian,
That is, by setting the general formula to [(2P-N/2) x 2π/N] radians, the efficiency of the small teeth 6a to 6f becomes substantially maximum, and the motor as a whole becomes substantially the most efficient. .

According to the motor configured as described above, a back electromotive force as shown in FIG. 2 was obtained through experiments. In FIG. 2, the solid line shows the back electromotive force waveform of the first phase coil 7, the two-dot chain line shows the back electromotive force waveform of the second phase coil (not shown), and the broken line shows the back electromotive force waveform of the third phase coil. (not shown) shows a back electromotive force waveform. FIG. 5 is a diagram comparing the back electromotive force waveform of the conventional motor shown in FIG. 6 and the back electromotive force waveform of the motor of the present embodiment shown in FIG. It is easy to understand that the motor of the embodiment generates a much larger back electromotive force than a conventional motor, and in connection with this, the back electromotive force at the switching point of the motor is also large.

The motor of FIG. 1 is supplied with current as shown in FIG. That is, the current shown in FIG. 4 is supplied to the first phase coil 7, the current shown in FIG. 4 is supplied to the second phase coil (not shown), and the current shown in FIG. A current shown in FIG. 4 is supplied to the coil (not shown). When such current is supplied, a composite torque waveform as shown in FIG. 3 is obtained, as is easily understood.

Although one embodiment of the brushless motor according to the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and changes can be made without departing from the scope of the present invention.

For example, in the example, the number of magnetic pole pairs of the rotor is 4,
Although the description has been made with reference to a motor in which the total number of large teeth and small teeth on the stator is 12, the present invention is not limited to this, but for example, the total number of large teeth and small teeth on the stator is It can be similarly applied to a motor etc. in which is 6. In such a case, the pitch angle α of the coil wound around the large teeth is an effective electrical angle of substantially π radians, and the pitch angle β of the coil wound around the small teeth is an effective electrical angle of substantially π radians. Set to π/3 radians.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

The back electromotive force generated by the motor as a whole is much larger than that of the conventional motor, and a large rotational torque can be obtained, and the electromotive force at the switching point of each phase is also larger than that of the conventional motor. In other words, the motor as a whole becomes substantially the most efficient, rotates smoothly, and has a large rotational force even though it is small. Furthermore, since the large teeth and small teeth are arranged at equal pitches, they can be easily and inexpensively manufactured. Furthermore, in the coil winding block, the large-tooth winding coil parts are arranged in point-symmetrical positions, and the small-tooth winding coil parts are arranged in point-symmetrical positions, so that the stator 3 It is well-balanced, the rotational torque acts substantially equally at point-symmetrical positions, and vibrations are extremely small during rotation.

[Brief explanation of drawings]

FIG. 1 is a simplified diagram showing an embodiment of the present invention;
Figure 2 is a waveform diagram of the generated back electromotive force, Figure 3 is a graph of the resultant torque, Figure 4 is a diagram of the current waveform applied to the coil, and Figure 5 is a waveform of the back electromotive force showing comparison with a conventional example. It is a diagram. Fig. 6 is a simplified diagram showing a conventional example, Fig. 7 is a waveform diagram of the back electromotive force generated, and Fig. 8 is a simplified diagram showing a conventional example.
The figure is a graph of the resultant torque, and FIG. 9 is a current waveform diagram applied to the coil. 2...Rotor, 3...Stator, 5a, 5b,
5c, 5d, 5e, 5f...Large teeth, 6a, 6b,
6c, 6d, 6e, 6f... small teeth, α, β... pitch angle.

Claims (1)

[Claims] 1. A stator having large teeth arranged at equal pitches in the circumferential direction and small teeth arranged between the large teeth, and a stator arranged opposite to the stator and driven to rotate in a predetermined direction. a coil winding block in which a large-tooth winding coil part and a small-tooth winding coil part are arranged at point-symmetrical positions, and the number of magnetic poles of the rotor is set to The pitch angle of the large-tooth-wound coil portion wound around the large teeth is set to be larger than the number of small teeth, and the pitch angle of the large-tooth wound coil portion is set to be larger than the number of coils wound around the small teeth. The pitch angle of the above-mentioned small tooth wound coil part is an effective electrical angle (2P - N/ 2) A brushless motor characterized by: ×2π/N radians.