JPS5925564A - Brushless motor - Google Patents

Abstract

PURPOSE:To generate torque extending over the whole circumference of a stator, and to improve efficiency by displacing the center of the distribution of magnetic flux generated in the stator from the center of the magnetic flux of a rotor. CONSTITUTION:The Ns and Ss of permanent magnets are disposed alternately to the cylindrical rotor 11. The stator 12 is arranged to the inside of the rotor 11. The stator 12 is constituted by arms 14 disposed radially from the center 13 and pole teeth 15 formed at the noses of the arms 14, and the noses of the arms 14 are combined where displaced from the center of the pole teeth 15. Exciting coils 16 are wound on the arms 14. That is, clearances among the rotor magnet 11 and the stator pole teeth 15 are kept constant, and the center of the stator pole teeth 15 and the center of the exciting coils 16 is displaced.

Description

[Detailed description of the invention] The present invention relates to brushless motors.

For conventional brushless motors, a structure has been proposed in which the clearance between the rotor and the stator magnetic pole teeth is different, and the center of the magnetic pole when the rotor is stopped is different from the center of the magnetic pole of the stator.

FIG. 1 shows an example of a conventional motor. In the figure, 1 is a rotor, 2 is a stator, and 3 is an excitation coil. When the rotor magnet 1 is stopped, the state is N.

The center of the S pole is the point where the clearance between the rotor and stator is maintained at its smallest size. The excitation coil 3 is arranged slightly shifted in the direction opposite to the rotation of the rotor 1, and the clearance between the rotor and the magnetic poles is C, which is larger than B.

As the angle further shifts, the clearance increases, and B
The torque is the largest at the point or point C, and as the clearance increases, the torque becomes extremely small. The only part that contributes to the overall torque is the clearance B or C, and the rest are just large clearances so that the rotor stops at B.

The brushless motor having the above structure has the disadvantage that the large clearance between the rotor and the stator does not contribute to torque, resulting in very low efficiency. The present invention aims to improve the above-mentioned drawbacks and provide a highly efficient brushless motor.

FIG. 2 shows an embodiment of the brushless motor of the present invention. In the figure, 11 is a cylindrical rotor in which N and S permanent magnets are arranged alternately, and 12 is a rotor arranged inside the rotor. The stator is composed of an arm 14 arranged radially around the center 13 and a magnetic pole tooth 15 provided at the tip of the arm, and the tip of the arm 14 is connected at a position shifted from the center of the magnetic pole tooth. are doing. Note that an excitation coil 16 is wound around each arm. That is, the clearance between the rotor magnet 11 and the stator magnetic pole tooth 15 is constant υ, and the center of the stator magnetic pole tooth 15 and the center of the exciting coil 16 are shifted from each other. This is mainly carried out when the number of magnetic poles of the rotor magnet and the number of magnetic poles of the stator are the same or an integral multiple.

Next, the operation will be explained.

(I) When the rotor is stopped, J9 in the magnetic pole of the rotor 11 is the magnetic pole tooth 1 of the stator, as shown in FIG.
It stops when it aligns with the center of 5. Arrows indicate the flow of magnetic flux.

FIG. 3(A) shows a state in which the magnetic poles of the magnet and the stator magnetic pole teeth are interlocked. In this state, no rotational force acts on the magnet, only the attractive force between the magnet and the magnetic pole teeth.

In the state shown in FIG. 3(B), magnetic flux passes from the north pole of the rotor to the magnetic pole teeth of the stator, and a portion of the magnetic flux passes directly through the surface of the magnetic pole teeth to the adjacent south pole. From this state, the magnet tries to move toward a state where the flow of magnetic flux is stable. That is, the state shown in FIG. 3(A) or the state in which the N pole is replaced by the S pole from the state shown in FIG. 3(A) is reached. Or rotor N.

The south pole boundary lies in the center of the stator's magnetic pole teeth. However, in the state shown in FIG. 3(B), the area where the N pole of the rotor faces the magnetic pole teeth of the stator is large, so it is easy to return to the state shown in FIG. 3(A).

TI) When the stator magnetic pole teeth are excited, the magnetic flux is distributed around the exciting coil winding.

The center of the magnetic pole of the magnet in the state shown in FIG. 3(a) will be slightly shifted.

As shown in FIG. 3(c), torque is generated due to the difference between the distribution center C of the magnetic flux density of the rotor 11 magnets and the excitation center C2 of the stator magnetic pole teeth 15, and rotational force is generated in the rotor magnets. do. Arrow X in the figure indicates the direction of rotation.

FIG. 4 shows another embodiment of the present invention, in which the stator magnet 4 protrudes slightly from the center of the temporary teeth 5 so that the flow of magnetism and flux is biased toward one side from the center of the magnetic pole tooth 15. A hole 17 is provided.

The present invention includes a rotatable cylindrical rotor in which N and S permanent magnets are arranged alternately as shown above, and a rotor that is arranged inside the rotor and that is connected to the surface of the magnetic pole teeth and the rotor. The stator has a certain clearance with the inner peripheral surface and has an excitation coil, and the center of the distribution of magnetic flux generated in the system stator by the current flowing through the excitation coil is
Since it is configured to be offset from the center of the rotor's magnetic flux distribution, (a) the entire circumference of the stator can contribute to torque generation, increasing efficiency.

(b) The structure is simple.

(c) Self-starting is easy.

It has the following effects.

[Brief explanation of drawings]

FIG. 1 shows a conventional brushless motor, FIG. 2 shows a brushless motor according to the present invention, and FIGS. 3(A) and 3(B). (C) is an explanatory diagram, and FIG. 4 shows another embodiment. DESCRIPTION OF SYMBOLS 11... Rotor, 12... Stator, 13... Center, 14... Arm, 15... Magnetic pole tooth, 16... Excitation coil, 17... Hole patent applicant

Claims (3)

[Claims] (1) A rotatable cylindrical rotor formed by alternately arranging N and S permanent magnets, and a rotor disposed inside the rotor and between the surface of the magnetic pole teeth and the inner peripheral surface of the rotor. and a stator having a certain clearance and a magnetic coil of B, and the center of the magnetic flux distribution generated in the system stator by the current flowing through the excitation coil is shifted from the center of the magnetic flux distribution of the rotor. A brushless motor characterized by: (2) Claim 1, wherein the center of the stator magnetic pole teeth and the center of the excitation coil are deviated from each other.
Brushless motor as described in section. (3) A patent claim characterized in that holes are provided in the magnetic pole teeth of the stator so that when the excitation coil of the stator is excited, the magnetic flux generated is biased toward one side from the center of the magnetic pole teeth. The brushless motor according to the range 1 above.