JPS63131120A - Method for fitting rotary mirror - Google Patents

Abstract

PURPOSE:To reduce the shift of a rotary mirror from the center of rotation owing to its radial movement by engaging a mirror fitting surface and a mirror with each other by aligning their engagement contact surfaces in a high temperature state at the time of use in consideration of the coefficients of thermal expansion of the materials of the mirror fitting surface and mirror. CONSTITUTION:A mirror fixing shaft 1 is made of a SUS-based material and the rotary mirror 3 is made of an aluminum-alloy-based material, and the projecting annular part 5 of the mirror fitting surface and the recessed groove part 6 of the mirror 3 engage each other while having a clearance at room temperature. The sizes of the projecting annular part 5 and the recessed groove part 6 at the room temperature are so set that the radius r2 of the inner periphery of the annular part 5 of the mirror fitting part 4 is equal to the radius r1 of the inner periphery of the recessed groove part 6 of the mirror 3 at high temperature in the use state. Further, a material which is equal in coefficient of thermal expansion to the material of the rotary mirror 3 is used as the materials of a mirror pressing member 2 and a clamping screw 7, so the shifting of the rotary mirror 3 due to its radial movement from the center of the rotary shaft 1 can be suppressed.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a polygon mirror in a laser deflector, and is used as an optical writing system by a laser deflector in a laser printer, digital copying machine, fax machine, etc. .

[Prior art]

Conventionally, as this type of technology, a structure has been proposed in which unevenness is provided on the abutting surfaces of the rotating polygon mirror and the polygon mirror holding member, and an adhesive is applied and filled between them to connect and fix the rotating polygon mirror to the holding member. However, as the temperature of the rotating polygon mirror rises, it does not have a positioning function in the radial direction between the rotating polygon mirror and the holding member, and it is difficult to adhere to the uneven groove between the rotating polygon mirror and the holding member. If the internal temperature of the optical deflector rises, the adhesive will thermally expand, worsening the mirror deflection of the rotating polygon mirror. It had drawbacks such as the mirror being impossible to replace.

〔the purpose〕

The present invention relates to a method for mounting a rotating mirror in an optical deflector, and in particular, the internal temperature of the optical deflector becomes quite high due to the heat of the motor, and the present invention generally relates to a rotating mirror made of aluminum alloy and a mirror made of SUS. This eliminates the drawback that the fit between the fixed shaft and the fixed shaft becomes loose due to the difference in thermal expansion, and the rotating mirror moves radially from the center of the rotating shaft, resulting in large fluctuations in the distance between the center of the rotating shaft and the reflecting surface of the rotating mirror. The present invention aims to provide a method for attaching a rotating mirror to a mirror fixing shaft without the drawbacks of the prior art.

〔composition〕

An example of the configuration of the present invention will be described below.

As shown in FIG. 1, the mirror fixing shaft 1 has a protruding mirror mounting portion 4 suitable for supporting the lower surface 3a of the rotating mirror 3, and the mirror mounting portion 4 has a convex annular portion 5. The convex annular portion 5 is fitted into a concave groove 6 formed on the lower surface 3a of the rotating mirror 3.

The mirror fixing shaft 1 that forms the mirror mounting part 4 is made of SUS material, and the rotating mirror 3 is made of aluminum alloy material, which have different coefficients of thermal expansion. Although there is some looseness in the fitting between the ring part 5 and the concave groove part 6, the convex ring part formed in the mirror mounting part 4 of the mirror fixing shaft 1 at the operating temperature (high temperature) The convex annular portion 5 and the concave groove portion 6 at room temperature are arranged such that the radius γ2 of the inner circumference of the rotating mirror 3 is equal to the radius γ1 of the inner circumference of the concave groove portion 6 formed on the lower surface 3a of the rotating mirror 3. Set the dimensions.

Therefore, the positions of the fitting holes of the six examples of concave grooves formed on the rotating mirror 3 are φ20+0.02, and the positions of the fitting holes of the five examples of convex annular parts formed on the mirror mounting part 4 are φ20−.
0.02 and the finished dimensions are the worst value, the diameter of the fitting hole of the three rotating mirrors is φ20.2, the diameter of the fitting hole on the mirror mounting part 4 side is φ=19.98, and at room temperature. A 40 μm backlash occurred, and when the rotating mirror 3 was in use,
If the temperature inside the optical deflector increases by 50 degrees, the diameter of the fitting hole for the three rotating mirrors becomes φ = 20.043, and the diameter of the fitting hole for the four mirror mounting parts becomes φ = 19.99. Therefore, the play between the rotating mirror 3 and the mirror mounting portion 4 increases to 52.7 μm in the radial direction.

Such backlash that occurs between the rotating mirror 3 and the mirror mounting portion 4 due to the rise in temperature can be eliminated by the above-described means of the present invention.

Due to the convex annular portion 5 of the mirror mounting portion 4 and the concave groove portion 6 of the rotating mirror 3 of the present invention, the rotating mirror 3 can be attached to the mirror mounting portion 4 at high temperatures when the rotating mirror 3 is in use. On the other hand, it is possible to rotate while accurately maintaining the degree of area without shifting the center of rotation.

A mirror holding member 2 is arranged on the upper surface 3b of the rotating mirror 3, and in order to fix the rotating mirror 3 to the mirror mounting part 4,
Three tightening screws 7 are inserted from the mirror holding member 2 side.

In the present invention, the mirror holding member 2 and the tightening screw 7 are made of materials that have a coefficient of thermal expansion equal to that of the material of the rotating mirror 3.

For this reason, conventionally, an iron-based material is used for the tightening screw 7, and an aluminum-based alloy is used for the mirror holding member 2 and the rotating mirror 3, respectively, and the coefficient of thermal expansion is iron 1.03 x 1.
0 -'/K, aluminum 2.3 Thermal stress is also larger.

In the present invention, such inconveniences can be solved by using the tightening screw 7,
By using materials for the mirror holding member 2 and the rotating mirror 3 that have the same coefficient of thermal expansion, displacement due to thermal stress can be prevented.

FIG. 2 shows another embodiment of the invention.

The mirror attachment part 4 formed on the mirror fixing shaft 1 has a convex annular part 5' having a tapered shape with a triangular cross section, and a concave groove part 6 formed in the lower surface 3a of the rotating mirror 3 in response to the convex annular part 5'. ′ with a tapered triangular cross section
The groove is shaped like this. In this case, a means is required to uniformly and always press the rotating mirror 3 against the mirror mounting portion 4. For this purpose, a mirror holding member 8 is provided on the upper surface of the rotating mirror 3 with a spacer 9 interposed therebetween. The holding member 8 has one end 8a attached to the mirror fixing shaft 1, and the other end 8b for pressing the rotating mirror 3 through a spacer 9 so that the rotating mirror 3 is always evenly pressed against the mirror mounting portion 4. There is.

With this configuration, the rotating mirror 3 can rotate without deviation of the center of rotation with respect to the center of the mirror mounting part 4, from room temperature to high temperature when the rotating mirror is used. Accurate surface accuracy of the mirror can be maintained.

〔effect〕

With the rotating mirror mounting method of the present invention, when the rotating mirror is in use, it is possible to reduce the deviation from the rotation axis due to radial movement of the rotating mirror, and also eliminate thermal stress acting in the thickness direction of the mirror. Therefore, it has the effect of maintaining the surface accuracy of the rotating mirror.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of the rotating mirror mounting method of the present invention, FIG. 1(b) is a top view of the mirror fixing shaft, and FIG. 1(c) is a bottom view of the rotating mirror. FIG. 6 shows a cross-sectional view of another method of attaching the rotating mirror of the invention. 1... Mirror fixing shaft, 2... Mirror holding member, 3...
...Rotating mirror, 4...Mirror mounting surface, 5,5'...
・Convex annular portion, 6, 6′... Concave groove portion, 7...
Tightening screw.

Claims (2)

[Claims] (1) A convex or concave portion for restricting radial movement is formed on the mirror mounting surface provided on the mirror fixing shaft, a concave or convex portion that can fit into the convex or concave portion is formed on one surface of the mirror, and the mirror The fitting of the convex part or the concave part between the mounting surface and one surface of the mirror is made by considering the coefficient of thermal expansion of each material of the mirror mounting surface and the rotating mirror, so that the engaging surfaces are aligned in the high temperature state during use, and the other surface of the mirror is A method for attaching a rotating mirror, characterized in that the mirror is fixed to the mirror fixing shaft side by a fixing means via a mirror holding member. (2) A patent characterized in that, in order to fix the mirror on the fixed shaft side of the mirror, the materials of the mirror holding member and the tightening bolt as a fixing means are made to have the same coefficient of thermal expansion as the material of the mirror. A method for attaching a rotating mirror according to claim 1.