JP2001211581A - Brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cogging torque, vibration and noise of a DC motor by simple structure. SOLUTION: A surface of a magnet 2 face-arranged with the inner or outer peripheral surface of the stator is formed with ruggedness in the peripheral axis direction by making the ruggedness skewed to the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor using a magnet formed of a resin to form a field.

[0002]

2. Description of the Related Art A conventional magnet motor will be described with reference to FIGS. FIG. 3 is a perspective view of a conventional inner rotor. FIG. 4 shows the magnet A shown in FIG.
It is -A sectional drawing. FIG. 5 is a side sectional view of a brushless DC motor using the rotor of FIG.

In FIG. 3, an inner rotor 11 includes a magnet 12 formed in a ring shape from resin, a ring-shaped rotor yoke 13 adhered and fixed to an inner peripheral surface of the magnet 12, and an inner rotor yoke 13. The shaft 14 is caulked around the periphery.

[0004] The outer peripheral surface of the ring-shaped magnet 12 is formed to be uneven in the circumferential direction. That is,
As shown in FIG. 4, a plurality of convex protrusions 12a are provided on the outer peripheral portion of the magnet 12 in the circumferential direction. The number of the protrusions 12a is equal to the number of magnetic poles. The magnetic pole is formed such that the boundary between the protrusions 12a, that is, the boundary between the concave bottom and the magnetic pole coincides with each other.

In FIG. 5, a brushless DC motor 15
A mold frame 19 having a stator 16 and a circuit board 17 built therein and molded into a bowl shape by molding with a mold resin 18; an inner rotor 11 housed in an inner peripheral portion of the mold frame 19; It is formed by bearings 20a and 20b which are inserted into the shaft 14 of the rotor 11 and rotatably support the rotor 11, and a housing 21 which accommodates the bearings 20a and 20b.

[0006]

As described above, by making the shape of the magnet outer peripheral surface of the rotor facing the inner peripheral surface of the stator uneven, the waveform of the induced voltage is approximated to a sine waveform. The vibration of the motor can be reduced.
However, since the cogging torque is generated between the stator and the rotor, the vibration cannot be sufficiently reduced.

[0007]

Therefore, according to the present invention, the surface of the magnet provided opposite to the inner or outer peripheral surface of the stator is formed in a circumferentially uneven shape, and the uneven portion is formed. A brushless DC motor characterized by forming a magnet by skewing in the axial direction.

[0008]

When the magnet used for the field is formed of resin, the surface of the magnet facing the stator is made uneven so that the induced voltage has a sinusoidal waveform, and the uneven portion is skewed. Reduce cogging torque.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS. 1 and 2, taking an inner rotor type brushless DC motor and an outer rotor type brushless DC motor as examples. FIG. 1 is a perspective view of an inner rotor according to the present invention. FIG. 2 is a perspective view of the outer rotor according to the present invention.

In FIG. 1, an inner rotor 1 has a magnet 2 formed in a ring shape, a rotor yoke 3 adhered to the inner peripheral surface of the magnet 2, and a shaft 4 caulked to the inner peripheral portion of the rotor yoke 3. It is composed of

The shape of the outer peripheral surface of the magnet 2 is formed to be uneven in the circumferential direction, similarly to the magnet of the rotor described in the conventional example.

Further, a cogging torque is generated due to a gap formed between a tooth portion of the stator and an adjacent tooth portion, that is, a so-called opening slot (not shown). The uneven portion on the outer peripheral surface is formed to be skewed in the axial direction. in this way. By applying skew, cogging torque can be reduced.

In FIG. 2, the outer rotor 5 includes a bowl-shaped magnet 6 and a shaft 7 attached to a hole 6a provided at the center of the bottom of the magnet 6.

As with the inner rotor 1 shown in FIG. 1, the shape of the inner peripheral surface of the magnet 6 facing the stator is as follows.
It is formed unevenly in the circumferential direction and is skewed in the axial direction.

As described above, the surface of the magnet facing the stator is made uneven so that the induced voltage becomes a sinusoidal waveform to reduce the vibration. Further, by skewing the uneven portion, the cogging torque is reduced. Has been reduced.

[0016]

According to the present invention, the cogging torque can be reduced with a simple structure. That is, vibration and noise of the motor can be reduced.

[0017]

[Brief description of the drawings]

FIG. 1 is a perspective view of an inner rotor according to the present invention.

FIG. 2 is a perspective view of an outer rotor according to the present invention.

FIG. 3 is a perspective view of a conventional inner rotor.

FIG. 4 is a sectional view taken along line AA of the magnet shown in FIG. 3;

FIG. 5 is a side sectional view of a brushless DC motor using the rotor of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 ... Inner rotor 2, 6, 12 ... Magnet 3, 13 ... Rotor yoke 4, 7, 14 ... Shaft 5 ... Outer rotor 15 ... Brushless DC motor 16 ... Stator 17 ... Circuit board 18 ... Mold resin 19 ... Mold frame 20a, 20b ... bearing 21 ... housing

Claims (1)

[Claims] In a brushless DC motor using a magnet formed of a resin to form a field, a surface of a magnet provided to face an inner peripheral surface or an outer peripheral surface of a stator is arranged in a circumferential direction. A brushless DC motor, wherein the magnet is formed in an uneven shape and the uneven portion is skewed in an axial direction to form a magnet.