JPH06175064A - Polygon mirror - Google Patents

Abstract

PURPOSE:To provide a polygon mirror having stable structure and without causing the deviation of the optical axis of a laser beam reflection. CONSTITUTION:A sleeve 6 having a shape symmetrical up and down in an axial direction is shrinkage-fitted and fixed on the outer periphery of a cylindrical bearing member 5, and a polygon mirror main body 1 is arranged at the upper part or the lower part of the sleeve 6 and a yoke 3 is arranged on a side opposite thereto, then they are tightened and fixed by a screw 4. The shape and the weight of the polygon mirror main body 1 and the yoke 3 are constituted so that centrifugal force acting on them may be nearly equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon mirror of a scanner device used in a laser printer or the like.

[0002]

2. Description of the Related Art The structure of a conventional polygon mirror of this type is shown in FIG. As shown in the figure, the polygon mirror, which is a rotating body, has a yoke 102 made of a metal material fixed to a cylindrical bearing member 105 made of a ceramic material by shrink fitting,
The polygon mirror body 101 and the yoke 103 are fastened and fixed to the yoke 102 with screws 104.

[0003]

However, the yoke 102 to which the polygon mirror main body 101 is attached is thinner than the ceramic bearing member 105, and thus the bearing member 105 is not required.
Since they are fixed at the upper end or the lower end of the yoke 102 by shrink fit, the shrink fit residual stress and strain of the yoke 102 become non-uniform with respect to the axial direction, and as shown in FIG. The surface in contact with the polygon mirror main body 101 is deformed during rotation, and the reflection surface 101a of the polygon mirror main body 101
Angle changes and the surface tilt characteristics deteriorate, and the laser reflection optical axis 2
Had caused 02 fluctuations. In other words, according to the changes in the shrinkage allowance due to the centrifugal force due to rotation and the temperature rise, the yoke 10
2 is deformed, and the screw hole portion of the surface of the yoke 102 which is in contact with the polygon mirror body 101 serves as a fulcrum due to the centrifugal force applied to the polygon mirror body 101 and the yoke 103 fixed to the yoke 102. The polygon mirror 101 and the yoke 103 are tilted toward the yoke 102.

As a result, the reflecting surface 1 of the polygon mirror 101
There is a problem in that the tilt of 01a differs depending on the number of revolutions and the temperature, the laser light reflection axis is not stable in the vertical direction, and causes a phenomenon of optical axis shift.

The present invention has been made in view of the above points, and an object of the present invention is to eliminate the above-mentioned problems and provide a polygon mirror having a stable structure in which the optical axis of the laser light reflection axis does not shift. To do.

[0006]

In order to solve the above problems, according to the present invention, as shown in FIG. 1, a sleeve 6 having a vertically symmetrical shape in the axial direction is shrink-fitted on the outer circumference of a cylindrical bearing member 5. The polygon mirror main body 1 is arranged on the upper or lower part of the sleeve 6 and the yoke 3 is arranged on the opposite side of the sleeve 6, and the yoke 3 is tightened and fixed by the screw 4, and the polygon mirror main body 1 and the yoke 3 are attached to it. It is characterized in that its shape and weight are configured so that the centrifugal forces acting are substantially equal.

As shown in FIG. 3, the sleeve 6 has an annular shape and is shrink-fitted and fixed to the center of the bearing member 5, and the polygon mirror main body 1 is arranged on the upper or lower portion and the yoke 3 is provided on the opposite side. Is arranged and tightened and fixed with a screw 4.

[0008]

According to the present invention, since the polygon mirror is constructed as described above, the shrink fit stress applied to the sleeve 6 becomes uniform in the vertical direction with respect to the axis of symmetry m. Since the surface of the sleeve 6 in contact with the polygon mirror main body 1 is hardly deformed due to the change or the change of the rotation speed, the reflecting surface 1a is hardly affected and the surface inclination characteristic is improved.

Further, the polygon mirror body 1 has a sleeve 6
When it is fixed to the upper part of the robot, a force that tilts the polygon mirror main body 1 toward the yoke 3 side acts depending on the rotation speed and temperature, but on the contrary,
The force of tilting toward the polygon mirror main body 1 side also acts on the black 3 and the forces cancel each other out. That is, by designing the weight and the diameter of the polygon mirror main body 1 and the yoke 3 in consideration of these, the forces for inclining each other become substantially equal, and the inclination of the polygon mirror main body is suppressed so that the laser light is emitted. The reflected optical axis can be kept stable.

[0010]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below in detail with reference to the drawings. 1A and 1B are views showing a structure of a polygon mirror according to a first embodiment of the present invention. FIG. 1A is a sectional view and FIG. 1B is a plan view. In the figure, reference numeral 5 is a bearing member made of a ceramic material and has a cylindrical shape. The sleeve 6 is a tubular body having a cross-sectional shape toward the center line and is shrink-fitted and fixed to the outer periphery of the bearing member 5 (details will be described later). The outer peripheral convex portion 6a of the sleeve 6 has a polygon mirror above and below it.
It is for fixing the main body 1 and the yoke 3.

FIG. 2 is a view for explaining the mounting of the bearing member 5 and the sleeve 6. Sleeve 6 as shown
Is made of a metal (a metal having a coefficient of thermal expansion higher than that of the bearing member 5), and is fixed to the outer periphery of the bearing member 5 made of a ceramic material by shrink-fitting with an annular body having a cross section toward the center line. It At that time, the symmetry axis m of the cross-sectional shape of the tongue is attached so as to be aligned with the central portion n of the bearing member 5 toward the center line. With this configuration, the symmetry axis m
The stress acts evenly in the vertical direction centering on the center, and the shape distortion of the sleeve 6 is less likely to occur due to changes in temperature and rotation speed.

As shown in FIG. 1, the polygon mirror main body 1 is arranged on the upper surface of the convex portion 6a of the sleeve 6, and is formed on the lower surface of the convex mirror 6a.
The polygon mirror body 1 and the convex portion 6a of the sleeve 6 and the yoke 3 are fastened with screws 4 to fix the polygon mirror body 1 and the yoke 3 to the sleeve 6. A magnet 7 is fixed to the lower surface of the yoke 3, and when the magnet 7 is used as a rotor magnet to apply a magnetic force from a stator or the like, the polygon mirror rotates about an axis passing through the central portion of the bearing member 5. To do.

[Second Embodiment] FIG. 3 is a view showing the structure of a polygon mirror according to a second embodiment of the present invention. As shown,
The sleeve 8 is annular and has a rectangular cross-sectional shape, so that the central portion of the bearing member 5 in the axial direction coincides with the axis of symmetry m.
Shrink fit around the bearing member. Other points are Example 1
In the same manner as above, stress acts evenly around the axis of symmetry m, and the shape distortion of the sleeve 8 is less likely to occur due to changes in temperature and rotation speed.

[0014]

As described in detail above, according to the present invention, the following excellent effects can be expected. (1) Since the shrink fit stress applied to the sleeve is uniform in the vertical direction with respect to the target axis, the polygon of the sleeve is affected by changes in centrifugal force due to changes in temperature and rotation speed during rotation of the polygon mirror. Since the surface in contact with the mirror body is hardly deformed, there is almost no effect on the polygon mirror reflection surface, and the surface collapse characteristics of the reflection surface of the polygon mirror body are improved.

(2) When the polygon mirror is fixed to the upper part of the sleeve, a force for tilting the polygon mirror toward the lower surface yoke acts due to the number of rotations and temperature. In the present invention, however, the lower surface yoke is reversed. Kuruku also exerts a force that tilts toward the polygon mirror main body side, and the forces cancel each other out. That is, by considering the weight and diameter of the polygon mirror main body and the lower surface yoke, the forces of tilting the polygon mirror main body become substantially equal to each other, the tilt of the polygon mirror main body is suppressed, and the laser reflection optical axis remains stable. be able to.

(3) In the conventional method, since the polygon mirror main body is sandwiched, it is necessary to finish the upper and lower surfaces of the polygon mirror main body with high precision. However, in the present invention, only the surface contacting the sleeve is finished. Finishing is easy.

(4) When the bearing member is made of a ceramic material, the shrinking stress applied to the bearing member is almost not compressive stress but shear stress, and the bearing member is cracked because it is not applied locally. Is gone.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a polygon mirror according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of mounting the bearing member and the sleeve.

FIG. 3 is a diagram showing a structure of a polygon mirror according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a structure of a conventional polygon mirror.

FIG. 5 is a diagram for explaining surface tilt of a polygon mirror-reflecting surface.

[Explanation of symbols]

 1 Polygon mirror main body 2 Yoke 3 Yoke 4 Screw 5 Bearing member 6 Sleeve 7 Magnet 8 Sleeve

Claims (3)

[Claims] 1. A polygon mirror having a structure in which a planar polygonal polygon mirror main body having a mirror surface formed on the outer periphery of a cylindrical bearing member is attached to the outer periphery of the bearing member in the axial direction. A polygon mirror characterized in that a vertically symmetrical sleeve is shrink-fitted and fixed, the polygon mirror body is arranged on the upper or lower part of the sleeve, and the yoke is arranged on the opposite side to the sleeve. . 2. The polygon mirror according to claim 1, wherein the sleeve has an annular shape and is shrink-fitted and fixed to the center of the bearing member. 3. The polygon mirror according to claim 1, wherein the polygon mirror body and the yoke are configured so that the centrifugal forces acting on them are substantially equal to each other in shape and weight.