JPH02146943A - Polygon scanner motor - Google Patents

Abstract

PURPOSE:To contrive the improvement of rotary accuracy by using as a motor bearing only a single ball bearing of four-point contact with an outside diameter larger than the axial length of a supporting part for the motor bearing. CONSTITUTION:Since a four-point contact ball bearing 2, having an outside diameter larger than the length of a part supporting a motor bearing, is used, a distance between supporting points is determined by a diametric size of a constituent member, so that its outside diameter can be increased with no restriction of the axial length a motor part. This four-point contact ball bearing or bearing itself, generating no clatter, can be singly used. A polygon mirror 1 and the four-point contact ball bearing 2 are secured interposing a back yoke base 7. Thus, rotary accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] [Prior Art] Polygon scanner motors are used for laser beam scanning in laser beam printers, which have become mainstream in recent years. Conventionally, as a polygon scanner motor, as shown in FIG. 2, a ball bearing 9 is placed at a certain distance, and a back yoke 3, an aluminum polygon mirror 1, and a polygon for fixing the polygon mirror are mounted on the ball bearing 9. A device in which a base 12 and a polygon presser 13 are fixed is known.

[Problems to be Solved by the Invention] Since the print quality of a laser beam printer is determined by the accuracy of laser beam irradiation on the print drum, the polygon scanner motor is required to have high rotation accuracy. FIG. 2 shows a cross-sectional view of a conventional Volivon scanner motor. However, in such a conventional polygon scanner motor, in order to ensure rotation accuracy such as surface tilt and deflection of the polygon mirror 1, the tilt angle becomes smaller as the distance between the bearings that are the fulcrum of the shaft 10 increases. Therefore, it was necessary to provide a sufficient distance between the two bearings 9 in the axial direction.

Furthermore, the back yoke 3, polygon base 12, and polygon mirror 1 that are fixed to the shaft each need to be fixed to the shaft 10 with high precision, so it is necessary to make the length of the fit with the shaft 10 sufficiently large. there were. This corresponds to making each length of g1 to g23 sufficiently large in FIG. 4.

However, for the reasons mentioned above, although the shaft 10 needs to have a sufficient length to ensure accuracy, there is a strong demand for miniaturization in information equipment, so the distance between the bearings and the length of the mesh This has resulted in the problem that the printing quality of the printer deteriorates because the rotational accuracy is unsatisfactory.

Therefore, the polygon scanner motor of the present invention solves these conventional problems and provides a polygon scanner motor that is small but has high rotation accuracy.

[Means for Solving the Problems] In order to solve the above problems, the polygon scanner and motor of the present invention use only one ball bearing having an outer diameter larger than the axial length of the motor bearing support portion as the motor bearing. It is characterized by having been. Further, the polygon mirror is made of resin, the polyhedron is coated with a reflective film, and the polygon mirror is further characterized in that a four-point contact ball bearing is used as the ball bearing.

[Example] Examples of the present invention will be described below based on the drawings. 1st
The figure is a sectional view of a polygon mirror motor of the present invention, in which numeral 1 is a polygon mirror made of resin and a reflective film is applied to the polyhedron. 2 is a 4-point contact ball bearing, and there is no play in the bearing itself, so you can expect high-precision rotation when used alone. The polygon mirror 1 and the four-point contact ball bearing 2 are fixed to each other with a pack yoke base 7 in between. pack yoke base 7
A back yoke 3 is also fixed to the back yoke 3, and a driving magnet 4 is further bonded to the back yoke 3.

The magnet 4 is a rare earth resin bonded magnet, has no cracks or chips, and has a large residual magnetic flux density, which contributes to making the motor part thinner.

Reference numeral 5 denotes a motor driving coil fixed on the yoke 6. The yoke 6 has a circuit formed on its surface with an insulating layer in between to facilitate electrical connection of coils and the like.

The above members need to be attached to the chassis 14 with high precision, or the rotating parts need to rotate with high precision, but in the present invention, a four-point contact ball bearing with an outer diameter larger than the length of the motor bearing support part is used. Because
Since the distance between the fulcrums is determined by the diameter of the component, it is possible to increase the outer diameter of the component without being constrained by the axial length of a part of the motor. Scanner motor can be configured.

To explain this with reference to FIG. 3, first, the rotation accuracy of the bearing is determined by the distance m1 between the balls of the bearing in the same plane. That is, the larger the ml, the greater the rigidity of the bearing against runout of the inner ring relative to the outer ring. This corresponds to 511 in FIG. 4, which is a conventional example. In addition, in the conventional example, the fitting length g2 of the back yoke 3 to the shaft 10, the polygon mirror 1
However, in the present invention, it is possible to make 91, the snake corresponding to g2, and m3 sufficiently large, which improves accuracy. be able to. In the conventional configuration, the shaft was supported at two points as far apart as possible, and each part was attached to the shaft in sequence, which resulted in the distances between the fulcrums being integrated on the shaft. In the polygon scanner motor of the present invention, since the distances between the supporting points are all perpendicular to the axial direction, there is no integration, and rotation accuracy can be improved while achieving miniaturization.

Further, since the polygon mirror 1 is supported over a large area, there is no need to use an expensive metal, and it is possible to use a resin polygon mirror, which is slightly inferior in rigidity to metal but is very cheap. Furthermore, since polygon mirrors made of resin are smaller in weight than those made of metal, they can be attached by adhesive, making it possible to further reduce the size and price.

[Effects of the Invention] As explained above, the polygon scanner motor of the present invention can be made smaller and smaller by changing the support structure of the members.
This has the effect of not only achieving higher precision but also reducing the number of parts and lowering costs.

Furthermore, the structure of the polygon scanner motor of the present invention is applicable to hard disk drives, flexible disk drives,
It can also be applied to making optical disk drives smaller and more precise.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a polygon scanner motor according to the present invention, Fig. 2 is a sectional view of a conventional polygon scanner motor, Fig. 3 is an explanatory diagram of a polygon scanner motor according to the present invention, and Fig. 4 is a sectional view of a conventional polygon scanner motor. FIG. 3 is an explanatory diagram of a scanner motor. 1... Polygon mirror 2... 4-point contact ball bearing, 3... Back yoke 4... Magnet 5... Coil 6... Yoke 7... Pack yoke base 8... Board 9... Ball bearing 10・・Shaft 11・・Stopper 12・・Polygon base 13・・Polygon presser 14・・Chassis Fig. 1 Fig. 3 Fig. 2 Fig. 4

Claims (3)

[Claims] (1) In a polygon scanner motor equipped with a polygon mirror used for laser beam scanning in laser beam printers, etc., only one ball bearing with an outer diameter larger than the axial length of the motor bearing support part is used as the motor bearing. A polygon scanner motor characterized by its use. (2) The polygon scanner motor according to claim 1, wherein the polygon mirror is made of resin, and the polygon is coated with a reflective film. (3) The polygon scanner motor according to claim 1, wherein a four-point contact ball bearing is used as the ball bearing.