JPS63274352A - brushless motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a brushless motor, and more particularly to a brushless motor that can be applied to laser beam writing systems such as laser printers and digital copying machines.

(Prior Art) An example of a conventional inner rotor type brushless motor will be described with reference to FIGS. 4 and 5. Figure 4 is a longitudinal sectional view;
FIG. 5 is a sectional view taken along line B-B of the slot core portion in FIG. 4. In the same figure, upper case 1a and lower case 1
In the center of case pair 1 consisting of b, the upper and lower cases l
A shaft 3 is installed which is rotatably supported by a pair of bearings 2a and 2b arranged at a and Ib, respectively. A polygon mirror 4 is fixed together with a pedestal 5 to the end of the shaft 3 protruding from the upper case 1a, and a magnet 6 is fixed to the end of the shaft 3 protruding from the lower case 1b. A coil body 8 housed in a frame body 7 is disposed around the magnet body 6 to constitute a frequency generator. Further, a rotor magnet 10 is fixed to the shaft 3 inside the case 1 via a rotor yoke 9, and a slot iron core 11 is disposed on the outer circumferential surface of the rotor magnet 10, the inner circumferential surfaces of which face each other with an appropriate gap. The outer peripheral surface of this slotted iron core 11 is fixed to the inner wall of the upper case 1a.

As shown in FIG. 5, the slotted core 11 is provided with a plurality of grooves 12 that communicate with a part of the inner peripheral surface.
A coil 13 is wound around each. In addition, in the figure, 14 is a Hall element.

By the way, in the brushless motor having the above-mentioned configuration, cogging torque occurs because it has the slot iron core 11.
It is very disadvantageous to use it in an optical deflector that requires uniform rotation.

As a brushless morph that does not generate the cogging torque, the coreless flat brushley motor that does not have the above-mentioned slot iron core is known.

However, a coreless flat brushless motor has a large structure and a large magnetic gap, resulting in a reduction in effective magnetic flux linkage (magnetic flux that contributes to torque), resulting in large losses. Furthermore, the diameter is larger than that of the inner rotor type brushless motor described above, making it unsuitable for high-speed rotation.

(Objective) An object of the present invention is to solve the problems of the prior art described above, and to provide a brushless morph that is cogging-free, has low loss, and is suitable for high-speed rotation.

(Structure) In order to achieve the above object, the present invention is characterized in that a non-magnetic material is used as the winding frame around which the coil is wound, and the entire surface facing the rotor magnet is formed concentrically with the rotor magnet. This is what I did.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

Fig. 1 is a longitudinal sectional view of this embodiment, Fig. 2 is a sectional view taken along the line A-A of the winding frame portion in Fig. 1, Fig. 3 (aJ is a front view of the coil alone, Fig. 3 ('b ) is a wiring diagram of a coil. In the figure, members corresponding to those explained in FIGS. 4 and 5 are given the same reference numerals.

In FIG. 1, in the center of a case body 1 consisting of an upper case 1a and a lower case 1b, there is a pair of bearings 2a arranged in the upper and lower cases la and lb, respectively.

A shaft 3 rotatably supported by 2b is installed.

A polygon mirror 4 is fixed together with a pedestal 5 to the end of the shaft 3 protruding from the upper case la, and a magnet 6 is fixed to the end of the shaft 3 protruding from the lower case 1b.
is fixed, and a frequency generator is constructed by arranging a coil body 8 housed in a frame body 7 around this magnet body 6.

Further, a rotor magnet 10 is fixed to the shaft 3 inside the case 1 via a rotor yoke 9. A winding rod 16 is installed so that the entire inner circumferential surface of the rotor magnet 10 faces the outer circumferential surface of the rotor magnet 10 in a concentric manner with an appropriate gap 15 therebetween. That is, the entire inner circumferential surface of the winding frame 16 faces the outer circumferential surface of the Roku magnet 1-10 without any grooves or irregularities. This winding frame 16 is formed using a non-magnetic material such as aluminum or a candle, and is fixed to the inner wall of the upper case 1a via a stator yoke 17 made of a ferromagnetic material. Since this winding frame 16 causes thin flow loss, it is better to have a laminated structure as shown in FIG.

Furthermore, as shown in FIG. 2, the winding frame 16 has a plurality of recesses 16a formed on its outer peripheral surface, and the protrusions 16b between the recesses 16a are fixed to the inner peripheral surface of the stator yoke 17.

A coil 13 is wound around the through hole formed by the recess 16a and the inner peripheral surface of the stator yoke 17 in the shape shown in FIG. 3 (al).
13a and 13b in Fig. In Fig. 2, the symbol ■ or ■ shown on each coil 13a to 131 indicates the direction in which the current flows. It shows.

In addition, in the figure, 14 is a Hall element.

In the above embodiment, speed is detected by a frequency generator consisting of a magnet body 6 and a coil body 8, and a control circuit (not shown) controls the current to the coils 13a to 13J to perform excitation switching and drive the shaft 3 to rotate. let The rotation of the shaft 3 causes the polygon mirror 4 to rotate at a constant speed.

In this way, the inner circumferential surface of the winding frame 16 is made into a curved surface without unevenness and is arranged so that this inner circumferential surface faces the outer circumferential surface of the rotor magnet 10 in a concentric manner.
・No energy is generated, and iron loss can be suppressed as much as possible, and the magnetic gap is smaller than conventional coreless flat brushless motors, resulting in less loss. Therefore, it is most suitable for ultra-high-speed rotation brushless motors using, for example, air bearings.

Note that plastics, ceramics, etc. can also be used as the material for the winding frame 16 if the problem of heat generation is solved.

Furthermore, in the above embodiment, a 3-phase 4ti inner rotor type brushless motor was shown as an example, but the present invention is limited by the number of phases, the number of poles, the motor type (inner rotor or outer rotor), and the wiring type. It's not a thing.

(Effects) As described above, the present invention can provide a brushless motor that can rotate at high speed without cogging and with low loss.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of one embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A of the winding frame portion in Fig. 1, and Fig. 3 (al is a front view of the coil alone; (b) is a coil connection diagram, FIG. 4 is a vertical cross-sectional view of the conventional example, and FIG. 5 is a cross-sectional view taken along the line B-B of the slot core portion in FIG. ... Coil, 16 ... Winding frame. ¥g/Figure 2 Figure 3 (a) (b,)

Claims (1)

[Claims] A brushless motor characterized in that a non-magnetic material is used as a winding frame for winding a coil, and the entire surface facing a rotor magnet is formed concentrically with the rotor magnet.