JPH11252886A - Dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC brushless motor, which is simple in structure and can be easily adjusted with an improved reluctance piece for making an easy start-up of the DC brushless motor. SOLUTION: In this DC brushless motor, a reluctance piece 10 is constituted of a magnetic material thin plate and has a circular arc forming section 10-2 extending in the axial direction, which is formed by bending and is secured and held by an edge of the external surface of a bearing box 4, or is constituted of a magnetic material sintered member and has the circular arc forming section 10-2 extending in the axial direction, which is formed as an integral part of the bearing box and is secured and held by an edge of the external surface of the bearing box, or is constituted of a magnetic material member and has a circular arc forming section 10-2 extending in the axial direction, which is formed as an integral part of the bearing box. The circular arc forming section which extend in the axial direction is so located as to face the inner surface of a disc-like permanent magnet 8 via a space and is structured close to the coil side in the radial direction of a hollow coil 3, so as to face that part of the hollow coil 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase DC brushless motor for driving an axial fan or the like, and more particularly to a DC brushless motor having high start-up reliability.

[0002]

2. Description of the Related Art FIGS. 7 and 8 are a front view showing a stator of an example of a DC brushless motor for driving an axial fan according to the prior art and a sectional view corresponding to the main part. An example of a similar DC brushless motor using a flat reluctance piece is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-69480. Between the pair of air-core coils 3 is a flat annular portion 12-1 and a radial arm 12 on the outer periphery of the annular portion.
A reluctance piece 12 of a magnetic member provided with a magnetic member 2 is also provided.

Although the details are omitted, the reluctance piece 12 is a single-phase drive for facilitating the avoidance of a dead point at the time of startup, and the shape and size of the reluctance piece 12 are variously devised for efficient startup. Since the reluctance piece 12 is disposed on the same plane as the air-core coil 3, the gap between the opposing rotor and the permanent magnet 8 is limited by the thickness of the air-core coil 3 and the gap between the stator and the rotor. In fact, the actual condition also depends on the manufacturing accuracy, such as voids.

[0004]

The conventional structure as described above has basic performance as a self-startable single-phase DC brushless motor, but the gap between the permanent magnet and the reluctance piece is large, and the self-starting is not possible. Therefore, there are many points to be improved, such as setting of optimum conditions for generating cogging torque and simplification of the shape.

[0005]

In the DC brushless motor according to the present invention, the reluctance piece used is formed of a magnetic thin plate, and an arc-shaped portion extending in the axial direction is bent and fixed to the outer peripheral end of the bearing housing. An arc-shaped portion formed of a magnetic material sintered member and extending in the axial direction is integrally formed and fixedly held at the outer peripheral end of the bearing box, or an arc-shaped portion formed of a magnetic material and extended in the axial direction is formed in the bearing box. The arc-shaped portion extending integrally in the axial direction is disposed so as to face the inner peripheral surface of the disk-shaped permanent magnet via a gap, and the arc-shaped portion is formed in the radial direction of the air-core coil. Are configured so as to be close to / opposed to the coil side.

In the above-described structure, the shape of the reluctance piece and the like can be determined centrally by determining the structure of the disk-shaped permanent magnet, which is a basic design requirement, and the reluctance piece is made of a permanent magnet. Is directly opposed to the inner peripheral surface in the radial direction, so that it is opposed by a small gap, and it is possible to efficiently generate cogging torque at the dead point position.

[0007]

FIG. 1 is a cross-sectional view of a DC brushless motor according to the present invention applied to an axial fan, and FIG. 2 is a cross-sectional view of a main part along line AA in FIG. In FIG. 1, 1 is a mounting plate, 2 is a substrate to which an air-core coil 3 is fixed, 3 is an air-core coil, 4 is a bearing box, 5 is a bearing, 6 is a rotor yoke, 7 is a blade, and 8 is a disk-shaped permanent. The magnet, 9 is a rotating shaft, and 10 is a reluctance piece.

In FIG. 1, the mounting plate 1 is provided with a plurality of windows 1-1 near the outer periphery thereof at positions facing the blades 7, and through this window 1-1, the flow of air generated by the rotation of the blades 7 is reduced to the outside. A bearing box 4 is fixed to the center of the mounting plate 1, an air core coil 3 is fixed to the substrate 2, and a rotating shaft 9 supported by a bearing 5 mounted on the bearing box 4. The rotor yoke 6, the permanent magnet 8, and the blade 7 are integrally fixed and rotatably held, and are integrated with an annular member 10-1 slidably provided on the outer periphery of the bearing housing 4. The arc-shaped forming portion 10-2 of the reluctance piece 10 comprising the arc-shaped forming portion 10-2 extending in the axial direction of the disc-shaped permanent magnet 8 is disposed so as to face the inner peripheral surface of the disk-shaped permanent magnet 8 via a gap. I have.

In the DC brushless motor according to the present invention shown in FIG. 1, the arc-shaped forming portion 10-2 of the reluctance piece is brought close to the radial coil side 3-1 of the air core coil 3 as shown in FIG. Air core coil 3
When no current is supplied to the coil, the magnetic pole of the permanent magnet 8 is attracted to the arc-shaped forming portion 10-2 of the reluctance piece 10 and stops at a position overlapping the air-core coil 3. This stop position is a position where starting is easy when the stator winding 3 is energized.

As shown in the perspective view of FIG. 3, the reluctance piece 10 has an outer diameter slightly smaller than the inner diameter of the disk-shaped permanent magnet 8 after the angular extension is punched and formed in the magnetic plate member. An annular forming portion 10-1 that is bent and formed to form an arc surface and two arc-shaped forming portions 10-2 extending in the axial direction are integrally formed.

FIG. 4 is a perspective view of a second embodiment of the reluctance piece 10. FIG. 4 shows an example in which the magnetic member is formed by sintering.
The individual arc-shaped forming portions 10-2 are integrally formed.

FIGS. 5 and 6 show the reluctance piece 10.
FIG. 9 is a partial front view and a cross-sectional view of a main part of a third example in which is formed integrally with the bearing housing 4. In FIGS. 5 and 6, the bearing housing comprises a cylindrical base 4-1 fixed to the substrate 2, and the cylindrical base 4-1.
The bearing holding section 4-2 provided at the center of the first section and the two arc-shaped forming sections 4-3 extending in the axial direction provided at the outer peripheral section are integrally formed. The arc-shaped forming portion 4-3 is arranged close to the coil side 3-1 in the radial direction of the air-core coil 3 as in the above-described first example.

The arc forming portion 10-2 extending in the axial direction of the reluctance piece 10 has a length in the axial direction and a gap length in accordance with the amount of leakage magnetic flux on the inner peripheral surface corresponding to the magnetic characteristics of the permanent magnet 8. The outer diameter to be determined can be set freely, and is not affected by the dimensions and accuracy of other members such as the stator winding unlike the prior art, and is opposed to the inner and outer peripheral surfaces of the disk-shaped permanent magnet 8. The configuration of the concentric arrangement of the arc forming portions of the reluctance pieces is advantageous in terms of securing the manufacturing accuracy and the like, and the configuration is applicable not only to the axial flow fan but to all DC brushless motors.

Since the DC brushless motor according to the present invention has the above-described structure, the structure of the reluctance piece for facilitating self-starting is simple, the adjustment is easy, and the DC brushless motor can be provided at a low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a DC brushless motor according to the present invention.

FIG. 2 is a cross-sectional view of a main part taken along line AA of the example of FIG. 1;

FIG. 3 is a perspective view of a first example of a reluctance piece of the DC brushless motor according to the present invention.

FIG. 4 is a perspective view of a second example of the reluctance piece of the DC brushless motor according to the present invention.

FIG. 5 is a front view of a third example of the reluctance piece of the DC brushless motor according to the present invention.

FIG. 6 is a sectional view of a main part of the example of FIG. 5;

FIG. 7 is a front view of a main part of a brushless motor according to the related art.

FIG. 8 is a sectional view of the example of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mounting plate 1-1 Window of mounting plate 2 Substrate to which stator windings are fixed 3 Air core coil 3-1 Coil side of air core coil in radial direction 4 Bearing box 4-1 Cylindrical base of bearing box 4-2 Bearing holding part 4-3 Arc-shaped forming part 5 Bearing 6 Rotor yoke 7 Blade 8 Permanent magnet 9 Rotor shaft 10 Reluctance piece 10-1 Reluctance piece annular part 10-2 Reluctant piece arc-shaped forming part 12 Flat reluctance piece 12-1 Annular part of flat reluctance piece 12-2 Arm of flat reluctance piece

Claims (5)

[Claims] 1. A stator having an air-core coil fixed on a substrate constituting a stator yoke, and a disk-shaped permanent magnet opposed to the air-core coil via a small air gap in a rotatable manner. An axial gap DC brushless motor having a revolving piece and a reluctance piece for avoiding non-startup, wherein the reluctance piece has an arc-forming portion extending in the axial direction, and the arc-forming portion has the arc-forming portion. A DC brushless motor characterized by being arranged so as to face an inner peripheral surface of a disk-shaped permanent magnet. 2. The reluctance piece according to claim 1, wherein an arc-shaped portion formed of a magnetic thin plate and extending in the axial direction is bent and formed and fixed to an outer peripheral end portion of the bearing housing. DC brushless motor. 3. The reluctance piece according to claim 1, wherein an arc forming portion made of a magnetic sintered material and extending in the axial direction is integrally formed and fixedly held at an outer peripheral end of the bearing housing. 4. The DC brushless motor according to 1. 4. The DC brushless motor according to claim 1, wherein the reluctance piece is formed integrally with a bearing box together with an arc-shaped portion formed of a magnetic member and extending in the axial direction. 5. The reluctance piece according to claim 1, wherein an arc forming portion is provided near a radial coil side of the air core coil.
5. The DC brushless motor according to 4.