JPH0363617A - Motor for laser beam printer - Google Patents

Abstract

PURPOSE:To decrease the number of components, to improve the productivity, and to miniaturize a motor by composing a rotary polygon mirror of a cylinder part and a flat plate part, and supporting the cylinder part on a fixed shaft through a bearing. CONSTITUTION:The rotary polygon mirror 3 is constituted of the cylinder part 1 and the flat plate part 2 extended to below the cylinder part in an external collar shape. Then the cylinder part 1 is supported pivotally on the fixed shaft 4 through the bearing 8, a flat plate type rotor magnet 6 is provided on the internal surface of the flat plate part 2, and a planar coil 7 is fixed on the fixed side opposite to the rotor magnet 6. Consequently, the flat plate part 2 of the polygon mirror body 3 is arranged almost in the axial center of the fixed shaft 4, so the polygon mirror 3 rotates in a stable state. Further, neither a rotor holder nor a fitting board is required, so the number of components is decreased to reduce the cost and size.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a motor for a laser beam printer.

[Prior art and problems to be solved by the invention] As shown in FIGS. 4 and 5, the conventional motor for a laser beam printer has a shaft C that is pivoted on the cylindrical portion of the bracket a).
, a stator d that is fitted onto the cylindrical portion, and a shaft C.
A rotor holder e fixed to one end side, a flat rotating polygon mirror g attached to the rotor holder e via a mounting plate f with bolts m, and a rotor magnet h attached to the rotor holder e. ing. i is a rotor yoke, j is a bearing, k is a control board, and n is a water element.

Therefore, since the rotating polygonal mirror g, the rotor holder e, etc. are supported in a cantilever manner with respect to the shaft C, the shaft ring center may be tilted with respect to the motor axis, and in such a case, During rotation, smooth rotational movement cannot be performed.

Therefore, the shaft C must be made highly rigid,
It is necessary to increase the diameter of the shaft or to make it from a metal with high rigidity, which has the drawback of increasing the size and weight of the entire motor.

Further, it requires a rotor holder e, a mounting plate f, etc., and has an extremely large number of parts, making assembly troublesome, and many of the parts require high machining accuracy, resulting in poor productivity. Furthermore, there is also the drawback that the distance l between the substrate and the rotating polygon mirror g is relatively large.

Therefore, the present invention provides a laser beam printer in which a rotating polygon mirror always rotates in a stable state, and which can improve productivity and reduce defective rate, failure rate, and cost. The purpose is to provide motors for

(Means for Solving !1lII!) In order to achieve the above-mentioned object, the motor for a laser beam printer of the present invention includes a cylindrical portion and a flange extending from an approximately central portion in the axial direction of the cylindrical portion. a rotating polygon mirror body consisting of a flat plate portion; a fixed shaft that pivotally supports the cylindrical portion via bearings disposed at both ends of the cylindrical portion; and a fixed shaft disposed on the inner surface of the flat plate portion of the rotary polygon mirror body; a flat rotor magnet disposed; a planar coil disposed on a fixed side so as to face the rotor magnet;
It is equipped with the following.

[Effect]

The flat plate part of the rotating polygon mirror is disposed approximately at the axial center of the fixed shaft, and the bearings are disposed at both ends of the cylindrical part, so that the rotating polygon mirror can rotate in a stable state. It becomes possible. Also, the rotor holder etc. can be omitted,
The number of parts can be reduced, and the size can be reduced accordingly.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show a motor for a laser beam printer according to the present invention. A mirror body 3, a fixed shaft 4 that pivotally supports the cylindrical portion 1, a flat rotor magnet 6 disposed on the inner surface 5 of the flat plate portion 2 of the rotating polygon mirror body 3, and a rotor magnet 6 that faces the rotor magnet 6. A planar coil 7 disposed on the fixed side as a shape.

As shown in FIG. 2, the rotating polygon mirror body 3 has a flat plate portion 2 having a hexagonal shape in plan view (in this embodiment), the outer circumferential surface of which is a ξ-shaped surface 17, and a cylindrical portion. Bearings 8, 8 are installed at both ends of the cylindrical portion 1, and the cylindrical portion 1 is pivotally supported on the shaft 4 via the bearings 8.8. A concave circumferential groove 9 is provided on the inner surface 5 of the flat plate portion 2, and a rotor magnet 6 is fitted into the concave circumferential groove 9. In addition, this flat plate part 2
A rotor yoke IO is housed inside the rotor yoke IO, which is made of a flat ring whose outer periphery 11 is bent to surround the outer periphery of the rotor magnet 6 and create a magnetic resistance. We are trying to reduce this.

Thus, the planar coil 7 is arranged on the control board 12, and the board 12 is attached to the mounting board 13. In other words, the planar coil 7 is disposed on the fixed side. Here, the mounting board 13 serves as both a bracket and a back yoke, and the shaft 4 is fitted into the through hole 14. That is, a concave circumferential groove 15 is formed in the shaft 4, and the circumferential edge of the through hole 14 fits into the concave circumferential groove 15. The shaft 4 is therefore held on the mounting plate 13. 16 is a cap that closes the opening of the cylindrical portion l.

Therefore, in this motor, the flat plate portion 2 of the rotating polygon mirror 3 is disposed approximately at the center of the fixed shaft 4 in the axial direction, and furthermore,
Since the bearings 8.8 are disposed at both ends of the cylindrical portion 1, mutual inclination of the ring center of the rotating polygon mirror 3 and the axis of the shaft 4 can be reliably prevented. Further, the dimension between the substrate 12 and the inner surface 5 of the rotating polygon mirror 3 can be made extremely small, and the dimension L between the substrate 12 and the outer surface 20 of the rotating polygon mirror 3! can be made small, resulting in a compact overall design. Furthermore, in this embodiment, since the back yoke and bracket are used, it is possible to further improve productivity and reduce costs.

Next, FIG. 3 shows another embodiment, in which the shaft 4 projects from approximately the center of the bracket 8, and the shaft 4 and the bracket 18 are integrally formed. Further, a back yoke 19 is interposed between the bracket 18 and the board 12.

Therefore, in this embodiment, the rigidity of the shaft 4 is increased, and the work of attaching the bracket 19 to the shaft 4 can be omitted, improving productivity.

Note that the present invention is not limited to the above-described embodiments, and the design may be changed without departing from the gist of the present invention. For example, the rotating polygon mirror 3 and the rotor magnet 6 may be made of ABS resin,
Plastics such as thermoplastic plastics such as methacrylic resin (PMMA) may be used as an integral part, and the material of the rotating polygon mirror 3 may be made of aluminum alloy or the like other than plastic. be. moreover,
The rotor yoke 10 installed inside the mirror body 3 can be freely extended until it reaches the vicinity of the ξ curved surface 17 without bending its outer peripheral edge.If it is extended, the rigidity of the outer peripheral edge of the mirror body 5 is improved, and the deformation of the mirror surface 17 due to thermal expansion (
This has the effect of suppressing deformation (such as becoming convex or concave).

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

Since it does not require a rotor holder, etc., the number of parts is reduced, productivity is improved, and costs can be reduced.In addition, the accumulation of assembly errors is reduced, and overall dimensional accuracy is good. This makes it possible to provide high-precision motors with low defective products and low failure rates.

In addition, the mass of the rotating part is significantly smaller than that of the conventional one (see Fig. 4), and the moment of inertia during rotation is reduced. Since it extends approximately at the center in the axial direction of the cylindrical portion l, this motor can perform precise rotation even when the rigidity of the shaft 4 is made smaller than before. Therefore, the required rigidity of the shaft 4 can be reduced, so the shaft diameter can be made smaller, the shaft material can be made of plastic, and the size and weight can be reduced. Note that if the shaft 4 is made of plastic, the bracket 18 of the motor in the embodiment shown in FIG. 3 is also made of plastic, and vibration noise can be reduced.

Further, since the motor can be made compact, there is an advantage that the degree of freedom in designing applied products such as laser printers using this motor is increased, and the weight can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a plan view, and FIG. 3 is a sectional view of another embodiment. FIG. 4 is a sectional view of the conventional example, and FIG. 5 is a plan view. DESCRIPTION OF SYMBOLS 1... Cylindrical part, 2... Flat plate part, 3... Rotating polygon mirror, 4... Fixed shaft, 5... Inner surface, 6... Flat rotor magnet, 7... Plane shaped coil, 8...
- Wheel support. Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A rotary polygon mirror body 3 consisting of a cylindrical portion 1 and a flat plate portion 2 extending in the shape of an outer flange from a substantially central portion in the axial direction of the cylindrical portion 1; and both ends of the cylindrical portion 1. a fixed shaft 4 that pivotally supports the cylindrical portion 1 via bearings 8, 8 disposed in the rotating polygon mirror body 3; A motor for a laser beam printer, comprising: a planar coil 7 disposed on a fixed side so as to face the rotor magnet 6.