JPH0634567B2 - Brushless motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a brushless motor.

[Conventional technology and its problems]

In a conventional brushless motor, a stator having teeth around which a coil is wound is used (that is,
Since it has a slot having a complicated shape to form the teeth), it is difficult to use when a large cogging torque is generated and a very smooth rotation is required. Further, in applications requiring high efficiency, for example, when it is necessary to lower the starting current, the current becomes small, and the ratio of the cogging torque to the torque generated by the stator magnetic field becomes very large.
Therefore, there is a drawback that the apparent torque ripple increases and the minimum value of the starting torque becomes extremely low.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and provide a brushless motor that smoothly rotates and has an extremely small cogging torque.

[Means for solving problems]

When the number of magnetized magnetic poles is P, the brushless motor of the present invention has a magnetic pole pitch of π / P radian, respectively.
A rotor in which poles and S poles are alternately arranged at a pitch of 2π / P radian, and a stator 2 in which a toroidal core is used and a two-phase coil is wound are provided, and each of the stators has Π / P in which the winding direction is sequentially reversed in the coil
P coil pitches of radians are formed at a pitch between coils of 2π / P radians, and each phase of the coils is
They are offset from each other by π / P radian.

[Action]

In the brushless motor of the present invention configured as described above, the toroidal core is used for the stator, and
Since the coils of each phase are alternately and continuously wound at the coil pitch α, the current supplied to both coils is switched sequentially according to the magnetic poles of the rotor. A magnetic pole-free portion such as a magnetic core does not occur, that is, there is no position where torque does not appear during rotation, and smooth rotation of the rotor with extremely small cogging torque can be obtained.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings illustrating examples.

FIG. 1 shows a simplified diagram of a two-phase bipolar brushless motor according to the present invention. In FIG. 1, reference numeral 1 denotes a rotor in which N poles and S poles are alternately magnetized, and the number of magnetized magnetic poles. Where P is, the N pole and the S pole have π / P radian magnetic pole pitches β and β, respectively, and the N pole and the S pole are alternately arranged at a pitch of 2π / P radian. . That is, in the illustrated example, since the number of magnetic poles is 4, N poles having a magnetic pole pitch β of π / 4 radians and S poles having a magnetic pole pitch β of π / 4 radians are alternately arranged every π / 2 radian. It is set up.

Reference numeral 2 denotes a stator that is fitted onto the rotor 1, and a coil 3 for two phases is wound around the stator 2. In the illustrated example, only the first phase is shown and the second phase is omitted. ing.

Thus, the coil 3 is formed with P coil pitches α of π / P radial in which the winding directions are sequentially reversed, with a pitch γ between coils of 2π / P radians. Then, the respective phases are shifted from each other by π / P radian so that the first phase and the second phase are not polymerized.

Therefore, in the illustrated example, since the number of magnetic poles of the rotor 1 is 4,
The coil pitch α is π / 4 radians, each coil pitch α is formed every π / 2 radians, and the 1-phase and the 2-phase are deviated by π / 4 radian. That is, the coil 3 of the first phase is wound counterclockwise from the part X to the part Y, and four coil pitches α of π / 4 radians whose winding directions are sequentially reversed at intervals of π / 2 radians are formed. To do. Also,
The second phase (not shown) is also wound in the same winding manner as the first phase, but the coil pitch α of the second phase is π / 4 radians clockwise from the coil 3 of the first phase. It shifts.

Then, the rotor position detector (not shown) attached to the fixed portion near the rotor 1 detects the position of the rotor 1, and switches the energization direction to the coils 3 and 3 according to the position of the rotor 1. To rotate the motor.

Then, the portion X of the first-phase coil 3 configured as described above is set to be positive, the portion Y of the coil 3 is set to be negative, and the energization direction of the first-phase coil 3 is set to the counterclockwise direction. If the energizing direction of the coil 3 of the second phase is also the counterclockwise direction, the rotor 1 rotates by receiving the rotational force in the arrow A direction, that is, the clockwise direction. And the rotor 1
Is rotated by π / 4 radians in the direction of arrow A, the first phase coil causes the rotor 1 to receive a rotational force in a direction opposite to the direction of arrow A, that is, in the counterclockwise direction. Therefore,
In this state, if the energizing direction of the first-phase coil 3 is switched to the opposite direction and the second-phase coil is left in the original energizing direction, the rotor 1 receives the rotational force in the direction of arrow A. It will be. That is, if the energizing directions of the first-phase coil 2 and the second-phase coil 3 are switched every time the rotor 1 rotates by π / 4 radians, the rotor 1 receives a rotational force in a constant direction. The rotor 1 can continue to rotate.
Therefore, in order to rotate the rotor 1 once, the energizing directions of the first-phase coils 3 and the second-phase coils 3 are switched eight times.

Further, in this brushless motor, when two rotor position detectors are arranged in the vicinity of the rotor 1 while being shifted by π / 4 radians, the waveforms detected by the rotor position detectors are I, as shown in FIG. II, the counter electromotive force waveforms generated in the two-phase coils 3 and 3 are as shown by I and II in FIG. 3, respectively.

Thus, the first-phase coils 3 and 2 constructed as described above
If currents such as I and II in FIG. 4 are respectively applied to the coil 3 of the phase, the torque generated in the coil 3 of the first phase and the torque generated in the coil 3 of the second phase are respectively shown in FIG. The waveform is as shown in II. Therefore, the combined torque waveform for the two phases can be made into a linear waveform as shown in FIG.

The magnetic pole pitch of each magnetic pole is set to about π / P radian because the reverse torque acts to reduce the efficiency at a larger magnetic pole pitch.

The present invention is not limited to the illustrated embodiments, and the design can be freely changed without departing from the scope of the present invention. For example, the number of magnetic poles can be freely changed, and the inner rotor type and the outer rotor type can be used. You are free to choose. further,
The magnet and the stator may be of a type that faces the shaft direction or a type that faces the radial direction. Although the number of coil turns wound is simplified in the illustrated example, a large number of turns are actually used. The angles are all mechanical angles.

〔The invention's effect〕

In the two-phase bipolar brushless motor of the present invention, magnetic poles (N poles, S poles) having the number of magnetic poles P are alternately arranged at the rotor at an interval equal to the magnetic pole pitch, while using a toroidal core for the stator. Since the two-phase coils are alternately and continuously wound at the coil pitch α, the combined current with very small ripple can be obtained by sequentially switching the currents to both coils according to the magnetic poles of the rotor. The cogging torque is extremely small, the rotor always rotates smoothly, and a highly efficient motor can be obtained.

[Brief description of drawings]

FIG. 1 is a simplified plan view showing an embodiment of the present invention, (I) and (II) of FIG. 2 are output waveform diagrams of two rotor position detectors for detecting rotor positions, and FIG. (I), (I
(I) is a back electromotive force waveform diagram generated in each of the two-phase coils when the rotor is rotating, and (I) and (II) in FIG.
Waveforms of energizing current supplied to phase coils, (I) and (II) of FIG. 5 are torque waveform diagrams generated by the two-phase coils, and FIG. 6 is a composite torque waveform diagram of two phases. . 1 ... Rotor, 2 ... Stator, 3 ... Coil, α ...
Coil pitch, β ... magnetic pole pitch, γ ... coil pitch.

Claims (1)

[Claims] 1. When the number of magnetic poles to be magnetized is P, magnetic pole pitches β and β of π / P radians are alternately arranged at a pitch of 2π / P radians. Rotor 1 and toroidal core are used and two-phase coils 3, 3
A coil pitch α of π / P radians, in which the winding directions of the coils 3 and 3 are sequentially reversed, in the stator 2 of 2π / P radians. P coils are formed with a pitch γ between the coils, and the phases of the coils 3 and 3 are mutually π /
A two-phase bipolar brushless motor characterized by a shift of P radians.