JPH0634566B2 - Brushless motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a brushless motor.

[Prior Art 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 the Problems] The brushless motor of the present invention uses a rotor magnetized at equal pitches on the circumference so that N poles and S poles are alternately adjacent to each other, and a toroidal core. And a stator around which a coil is wound, and when the number of magnetic poles of the rotor is P and the number of phases of the coil is A, the winding direction of each coil is sequentially reversed in the stator. P coil pitches of 2π / (A × P) radians are formed at a pitch between the coils of 2π / P radians, and the phases of the coils are displaced from each other by 2π / (A × P) radians. ing.

[Action]

In the brushless motor of the present invention configured as described above, the toroidal core is used for the stator, and the coils of a plurality of phases are sequentially wound around the coil at the coil pitch α. By sequentially switching the energizing current according to the magnetic poles of the rotor, there is no magnetic pole-like portion such as a slotted core on the stator side for each magnetic pole of the rotor, that is, there is a position where torque does not appear during rotation. Without this, 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 brushless motor. In FIG. 1, reference numeral 1 denotes a rotor having four magnetic poles, which has N poles and S poles.
The poles are magnetized at equal pitches so that the poles are alternately adjacent to each other. That is, the rotor 1 has N
The poles, S poles, N poles, and S poles are sequentially magnetized. Reference numeral 2 denotes a stator which is fitted onto the rotor 1 and uses a toroidal core. The coils 3 for three phases are wound around the stator 2, but only the first phase is shown and the second and third phases are omitted in the illustrated example.

Thus, the coil 3 has a winding direction of 2π / (A × P) radians which is sequentially opposite when the number of magnetic poles of the rotor 1 is P and the number of phases wound around the stator 2 is A. P coils are formed at a coil pitch α of 2π / P radians and a pitch β between the coils. And each phase of the coil 3 is 2π / (A ×
P) Radian offset.

Therefore, in the illustrated example, since the number of magnetic poles of the rotor 1 is 4 and the number of phases of the coil 3 is 3, the coil pitch α is 2π / 3 × 4 radians = π / 6 radians, and the inter-coil pitch β is
Are formed at a pitch of 2π / 4 radians = π / 2 radians, and each phase is shifted by 2π / 3 × 4 radians = π / 6 radians. That is, the coil 3 of the first phase is wound counterclockwise from the part X to the part Y, and the coil pitch α of four π / 6 radians whose winding directions are sequentially reversed at every π / 2 radian. Form. Also, the second phase (not shown) is 1
The coils are wound in the same manner as the first phase, but this second-phase coil is π / 6 clockwise from the first-phase coil 3.
Radian shift. Further, the third phase is also wound in the same winding manner as the first phase, but this third phase coil is shifted from the second phase coil in the clockwise direction by π / 6 radians.
(That is, the coils of the third phase deviate from the coils 3 of the first phase by π / 3 radians.) Then, the motor is rotated by sequentially energizing them according to the rotational position of the rotor 1.

In addition, the rotor position detector for each phase by a hall element or the like (not shown) is sequentially set to a fixed portion near the rotor 1 by π /
The rotor 1 is attached to each rotor position detector with three offsets.
The position of each coil 3 is detected according to the rotor position.
The motor rotates by controlling the power supply to the motor.

With the above-mentioned configuration, the output waveforms of the three rotor position detectors are I, II, and
In addition to III, the back electromotive force waveforms generated in each coil are the waveforms I, II, and III in FIG. 3, respectively. The combined torque waveform generated in the rotor by the three-phase coils has a straight-line waveform as shown in FIG. In the figure, there is a step in the waveform of the combined torque, but this step is shown to make the switching point of each phase easier to understand. Actually, this step (that is,
Very little ripple). Note that the angle is shown as a mechanical angle, and the number of turns of each coil 3 is actually many, although it is simplified in the illustrated example.

The present invention is not limited to the embodiments shown in the drawings, and design changes can be freely made without departing from the gist of the present invention.
Although a polar unipolar is shown, the number of phases and the number of poles are free, and the bipolar type is also free, and the inner rotor type and the outer rotor type are also free. Furthermore, the stator and the magnet may be of an axial facing type, a radial facing type, or the like.

〔The invention's effect〕

In the brushless motor of the present invention, magnetic poles (N poles, S poles) having a number of magnetic poles P are arranged adjacent to each other in the rotor, while a toroidal core is used in the stator, and coils of a plurality of phases are respectively attached to the toroidal core. Since the coil is continuously wound at the coil pitch α, the combined current with very small ripple can be obtained by sequentially switching the current to each coil according to the magnetic poles of the rotor. Since the rotor is extremely small and the rotor always rotates smoothly, 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), (II) and (III) of FIG. 2 are output waveform diagrams of three rotor position detectors respectively, and FIG. I), (II), (II
I) is a back electromotive force waveform diagram generated in each of the three-phase coils, and FIG. 4 is a combined torque waveform diagram. 1 ... Rotor, 2 ... Stator, 3 ... Coil, α ...
Coil pitch, β ... Pitch between coils.

Claims (1)

[Claims] Claim: What is claimed is: 1. A rotor 1 magnetized at equal circumferential pitches so that N poles and S poles are alternately adjacent to each other, and a stator 2 in which a toroidal core is used and coils 3 are wound.
When the number of magnetic poles of the rotor 1 is P and the number of phases of the coils 3 is A, the winding directions of the respective coils 3 on the stator 2 are sequentially reversed. 2π / (A
× P) radian coil pitch α is formed with a coil pitch β of 2π / P radians, and the phases of the coils 3 ... Are mutually shifted by 2π / (A × P) radians. Brushless motor characterized by.