JPH04247420A - Method for fixing rotary polygon mirror - Google Patents

Abstract

PURPOSE:To eliminate the blurring of a rotary polygon mirror. CONSTITUTION:A hole 11d having difference in level is formed at the center of the polygon mirror 11 which is an almost polygonal prism in an optical deflection device. Besides, the shrinkage fitting of the hole 11d and a shaft 12 is executed. Such shrinkage fitting is executed under a state that the bottom surface 11c of the mirror 11 is made to press-contact with the bearing surface 12b of a flange 12a provided on the shaft 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing a rotating polygon mirror in an optical deflection device that deflects a light beam from a laser light source or the like and scans an object to be irradiated.

0002

7 shows a configuration diagram of an optical deflection device used in a laser scanning device. A laser element 2 is driven to emit light by a current from a laser driver 1, and the emitted laser beam passes through a collimator lens system 3. The parallel light beam is reflected by the rotating polygon mirror 4 rotating in the direction of the arrow B, and is imaged on the photoreceptor drum 6 by the fθ lens group 5 for scanning. In such a device, the rotating polygon mirror 4 has an ultra-high precision plane in order to perform deflection for scanning with high precision, and is required to be lightweight in order to reduce power consumption. An aluminum alloy with a metal vapor-deposited film to prevent oxidation is used.

As shown in FIG. 8, the rotating polygon mirror 4 is inserted through the rotating shaft 7 in a clearance fit state and is fixed to a flange (not shown) provided on the rotating shaft 7 with a screw 8. That is, by providing a plurality of screw insertion holes at equal angular intervals in the rotating polygon mirror 4, passing the male screws 8 through the holes, and screwing them into the plurality of female threads provided on the flange of the rotating shaft 7, the screws of the male screws 8 can be screwed. Rotating polygon mirror 4 between head and flange
is being held.

[0004] Such a fixing method is superior in terms of strength, and even when the rotating polygon mirror 4 is large in size or rotates at high speed, no deviation from the rotating shaft 7 occurs.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, when the rotating polygon mirror 4 thermally expands due to heat generated by high-speed rotation, it expands inward around the portion fixed by the screw 8, and the rotation is interrupted. It comes into contact with the shaft 7 and biases it. This biasing force causes the center of rotation of the rotating polygon mirror 4 to shift, resulting in a scanning position shift, and also disrupts balance adjustment, causing vibrations and significantly deteriorating the quality of recorded images.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for fixing a rotating polygon mirror that eliminates the above-mentioned drawbacks and does not reduce the positional accuracy of the rotating polygon mirror regardless of temperature changes.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, an optical deflection device according to the present invention positions a rotating polygon mirror in the direction of the rotation axis by bringing it into contact with a flange provided on the rotation axis. The rotating polygon mirror is fixed to the rotating shaft by shrink fitting.

[0008]

[Operation] According to the method for fixing a rotating polygon mirror having the above-described structure, since the rotating polygon mirror is attached by shrink fitting, there is no possibility that the rotation axis of the rotating polygon mirror will shift due to temperature changes.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the embodiments shown in FIGS. 1 to 5.

FIG. 1 shows an exploded perspective view of the rotating polygon mirror and rotating shaft before fixation, and the polygon mirror 11, which is a low-height, substantially prismatic body made of aluminum, is shrink-fitted to the rotating shaft 12 made of iron. It shows the shape of. The polygon mirror 11 has a plurality of side surfaces 11a.
is a plane mirror, and a stepped hole 11d is formed from the upper surface 11b to the lower surface 11c. A flange 12a is provided in the middle of the rotating shaft 12, and a seating surface 12b on the upper side of the flange 12a is a plane perpendicular to the central axis.

FIG. 2 is a sectional view of the main part shown in FIG. 1, showing a state in which the polygon mirror 11 is fitted onto the rotating shaft 12. The hole 11d at the center of the polygon mirror 11 has a length t in the central axis direction, that is, a thickness t, and the inner surface of the lower half of the hole 11d having a length of t/2 is in close contact with the rotating shaft 12, and the upper half of the hole 11d has a length of t/2. length t/2
The inner diameter of the part is larger than that. Further, the lower surface 11c of the polygon mirror 11 is in close contact with the bottom surface 12b of the rotating shaft 12.

[0012] Such a state is formed as follows. The diameter of the rotating shaft 12 is 20 (tolerance +
0.010 to +0.015) mm, and the inner diameter of the lower half of the polygon mirror 11, that is, the smaller one, is 20 (tolerance -0.005 to ±
0) mm, and the coefficient of linear expansion is 1.2×1 for the rotating shaft 12.
0-5/°C, and the polygon mirror 11 has a temperature of 2.3×10-5/°C. At room temperature, the rotating shaft 12 cannot fit in because it is thicker than the hole 11d of the polygon mirror 11, but when the polygon mirror 11 is heated to 100°C,
By increasing the temperature by ℃, the inner diameter becomes 20 x 75 x 2.3 x 10-
Expands by 5=0.0345 (mm).

In other words, the inner diameter of the hole 11d is 20 (tolerance +0)
．． 0295 to +0.0345) mm, and in this state, the rotating shaft 12 is inserted, and the lower surface 11c of the polygon mirror 11 is brought into close contact with the seating surface 12b of the flange 12a of the rotating shaft 12. In this way, the shrink-fitted polygon mirror 11 and rotation shaft 12 are
Even if the temperature rises by 27°C due to use, the diameter of the rotating shaft 12 is 20 (tolerance +0.017 to +0.022) mm, and the inner diameter of the hole 11d is 20 (tolerance +0.008 to +0.0 mm).
13) mm and will not come out.

Furthermore, since the polygon mirror 11 uses the lower surface 11c as a reference surface and cuts the reflecting surface 11a and the inner surface of the hole 11d, the perpendicularity between the hole 11d and the lower surface 11c is determined by the machining accuracy. In high-precision machining, it is advantageous to have a short length to be machined and a small area, so by shortening the length of the portion of the hole 11d that abuts the rotating shaft 12, the machining accuracy can be increased.

Specifically, in the past, the perpendicularity was, for example, 6μ.
m, but now it is 4 μm, which is an improvement. At the same time, it also has the advantage of shortening the time required for high-precision machining and extending the life of the processing machine. Furthermore, by shortening the length of the abutting part of the hole 11d, the vicinity of the hole 11d of the polygon mirror 11 becomes slightly deformed, and by shrink-fitting the lower surface 11c to the seat surface 12b, Lower surface 11c and hole 11
The lower surface 11c and the seat surface 12 are almost unaffected by the perpendicularity of d.
b can be brought into close contact with each other. Therefore, when the hole 11d is inclined from the right angle by the angle α as shown in FIG.
As shown in FIG. 4, it is possible to avoid a situation where the lower surface 11c comes into contact with the end of the flange 12a and is not parallel to the seat surface 12b.

In the first embodiment, the portion of the hole 11d that is in close contact with the rotating shaft 12 is t/2 from the bottom of the hole 11d.
However, the shorter the length, the better, and the position may be near the center of the hole 11d as shown in Figure 5, or at a certain length from above as shown in Figure 6. There is no problem even if there is. However, when the polygon mirror 11 is rotationally driven,
Needless to say, the length must be long enough to generate enough holding force to prevent the polygon mirror 11 from slipping.

[0017]

[Effects of the Invention] As explained above, according to the method for fixing a rotating polygon mirror according to the present invention, the central axis of the rotating polygon mirror does not shift due to temperature changes, so that deflected light beams are prevented from being deflected. do not have.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view before fixing.

FIG. 2 is a sectional view after fixing according to the first embodiment.

FIG. 3 is a cross-sectional view of a polygon mirror in which holes are formed at an angle.

FIG. 4 is a cross-sectional view of a polygon mirror with inclined holes attached to a rotating shaft.

FIG. 5 is a cross-sectional view of the second embodiment.

FIG. 6 is a cross-sectional view according to a third embodiment.

FIG. 7 is a layout diagram of a light deflection device.

FIG. 8 is a plan view of a conventional polygon mirror.

[Explanation of symbols]

11 Polygon mirror 11a Mirror surface 11c bottom 11d Through hole 12 Rotation axis 12a Flange 12b Seat surface

Claims (2)

[Claims] 1. In the case where the rotating polygon mirror is positioned in the direction of the rotation axis by abutting against a flange provided on the rotation shaft, the rotating polygon mirror is fixed to the rotation shaft by shrink fitting. How to fix a rotating polygon mirror. 2. The method of fixing a rotating polygon mirror according to claim 1, wherein the length in the axial direction of the inner surface shrink-fitted to the rotating shaft of the rotating polygon mirror is shorter than the thickness of the rotating polygon mirror.