JPH04333816A - Fixing method for rotary polygon mirror - Google Patents

Abstract

PURPOSE:To hold a reflecting surface with high accuracy by gripping a polygon mirror with a receiving seat surface and a ring-shaped member provided on a rotary shaft and clamping the ring-shaped member threadably to a male screw provided on the rotary shaft. CONSTITUTION:After the polygon mirror 1 which has eight reflecting surfaces 2 at its periphery and is provided with a through hole 3 in the center is fitted to the fitting part 7 of the rotary shaft, the ring-shaped member 10 is clamped threadably to the male screw part 8 of the rotary shaft 4. Then the polygon mirror 1 is fixed while pressed against the receiving seat surface 5 which is finished into a highly accurate plane at right angles to the axial direction of the rotary shaft 4. At this time, the rotating direction wherein the screw is fastened is set to the opposite direction from the rotating direction of the polygon mirror 1 at the time of a rotary scan. Therefore, the screw is never loosened at the time of the rotary scan of the polygon mirror 1, which can stably be held.

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 used in an optical deflector of a laser printer, digital copying machine, etc.

0002

[Prior Art] Conventionally, as a method for fixing this type of rotating polygon mirror to a rotating shaft, in order to prevent the positional relationship between the rotating shaft and the polygon mirror from shifting due to rotational acceleration, the rotating polygon mirror is generally fixed at equal intervals. A method is adopted in which the polygon mirror is held between the screw head and the seat of the male screw by making multiple screw insertion holes, passing the female screws through these holes, and fixing them to the multiple female threads provided on the seat of the rotating shaft. has been done. This fixing method using screws has excellent strength, and is suitable for use with large polygon mirrors,
This has the advantage that even when the polygon mirror is rotated at a high speed such as 0 rpm, no misalignment occurs between the seat of the rotation axis and the polygon mirror.

0003

[Problems to be Solved by the Invention] However, in this conventional method, the pressure for fixing the polygon mirror to the seat of the rotating shaft is distributed at equal angular intervals, and the pressure applied to the polygon mirror is centered around the head of each tightened male screw. has been added. Therefore, when the polygon mirror thermally expands due to a rise in temperature caused by friction and wind damage when the device operates, the degree of thermal expansion differs between the parts that are fixed with screws and the parts that are not, causing distortion. Therefore, there is a drawback that the surface precision of the highly precisely finished reflective surface is significantly deteriorated.

Furthermore, if distortion due to thermal expansion occurs partially in the polygon mirror, the balance adjustment that prevents the center of gravity from shifting during rotation will be disrupted, causing the reflective surface to fall and the balance to collapse during rotation. This causes vibration, which significantly deteriorates the rotational performance of the polygon mirror.

In particular, in devices that require high-speed rotation, the motor section that generates the rotational driving force suffers a lot of energy loss due to friction, wind damage, etc., and the amount of heat generated by the motor section increases dramatically. A major problem is the reduction in image quality due to distortion due to thermal expansion.

On the other hand, in order to correct the uneven pressure caused by screw fastening, a method has been considered in which a spacer is inserted between the screw head and the polygon mirror to alleviate the pressure transmitted from the screw head to the polygon mirror. However, the spacer thickness increases the size of the device, increases power consumption and heat generation in the motor due to increased rotational moment, and furthermore, the center of gravity of the rotating shaft that supports the polygon mirror becomes higher, making the rotational balance unstable. , it has drawbacks such as hindering high-speed rotation of the polygon mirror.

An object of the present invention is to solve this problem by fixing the polygon mirror so that different pressures are not applied locally, thereby reducing the deterioration of the accuracy of the reflecting surface of the polygon mirror due to thermal expansion. An object of the present invention is to provide a method for fixing a rotating polygon mirror that prevents the rotation from occurring.

[0008]

[Means for Solving the Problems] A method for fixing a rotating polygon mirror according to the present invention to achieve the above-mentioned object is to fit a rotating shaft having a male threaded portion, a fitting portion, and a seat surface in order from the end. After fitting a through hole provided in the center of the polygon mirror into the part, a ring-shaped member having a female thread is screwed into the male thread part, thereby attaching the polygon mirror between the receiving surface and the ring-shaped member. It is characterized by being clamped and fixed between.

[0009]

[Operation] The method for fixing the rotating polygon mirror having the above configuration is as follows:
The pressure applied to the polygon mirror by the fixing means is evenly distributed, and deformation of the reflective surface of the polygon mirror due to thermal expansion during temperature rise is suppressed.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the illustrated embodiments. 1 and 2 show a first embodiment, with FIG. 1 showing the assembled state of each member and FIG. 2 showing the disassembled state. In the drawings, reference numeral 1 denotes a polygon mirror having eight reflective surfaces 2 around it and a through hole 3 in the center, and a rotating shaft is attached to this polygon mirror 1. The rotating shaft 4 is continuous with a flange portion 6 having a seat surface 5 for receiving the polygon mirror 1.
It has a fitting part 7 that fits into the through hole 3 and a male threaded part 8, and the male threaded part 8, the fitting part 7, and the seat surface 5 are provided in this order from the end. The through hole 3 of the polygon mirror 1 and the fitting part 7 of the rotating shaft 4 have a function of coaxially aligning the rotation center of the rotating shaft 4 and the polygon mirror 1, and the length of the fitting part 7 in the axial direction is The thickness L is slightly smaller than the thickness d of the polygon mirror 1. Further, the outer diameter of the thread of the male threaded portion 8 is slightly smaller than the outer diameter of the fitting portion 7. The seat surface 5 for receiving the polygon mirror 1 has a highly accurate flat finish perpendicular to the axial direction of the rotating shaft 4. A ring-shaped member 10 having a female thread 9 is screwed into the male threaded portion 8 , and the polygon mirror 1 is screwed into the male threaded portion 8 .
are pressed down evenly.

[0011] These component parts are assembled in the following steps. First, after fitting the polygon mirror 1 into the fitting part 7 of the rotating shaft 4, the ring-shaped member 10 is screwed onto the male threaded part 8 of the rotating shaft 4 and tightened, and the polygon mirror 1 is pressed against the seat surface 5. Fix it in the fixed position. At this time, the direction of rotation in which the screw is tightened is set to be opposite to the direction of rotation of the polygon mirror 1 during rotational scanning. Therefore, even when the polygon mirror 1 is rotated and scanned, the screws do not come loose and the polygon mirror 1 can be stably held.

In this embodiment, the polygon mirror 1 is pressed by almost the entire surface of the ring-shaped member 10, so that stress is dispersed and the polygon mirror can be fixed with uniform pressure, compared to the conventional fixing method described above. Therefore, it is possible to solve the problem that occurs in conventional fixing methods due to partially uneven pressure, that is, the reflective surface of the polygon mirror deforms when the temperature rises. .

FIG. 3 shows a second embodiment, in which the ring-shaped member 10 is thicker at the outer circumferential portion 12 than at the central portion 11. As shown in FIG. For this reason, the ring-shaped member 10
Rather than applying pressure to the polygon mirror 1 with the entire lower surface of the polygon mirror 1, pressure is applied only with the lower surface of the outer circumference 12, making it possible to fix the polygon mirror 1 in a state where stress is more evenly distributed. .

FIG. 4 shows a third embodiment, in which a second ring-shaped member 13 having almost the same shape as the ring-shaped member 10 and having a smaller outer diameter is stacked one step above the ring-shaped member 10. An example of its use is shown. The ring-shaped members 10 and 13 are stacked in two stages and used when the lower surface of the first ring-shaped member 10 is not sufficiently flat.
Since it is possible that the polygon mirror 1 is fixed in one-sided contact with the polygon mirror 1, the pressure can be more evenly distributed by fixing it from above with the second ring-shaped member 13 having a small outer diameter. be. Further, the fixing performance of the polygon mirror 1 itself is improved.

[0015]

Effects of the Invention As explained above, the method for fixing a rotating polygon mirror according to the present invention is such that the polygon mirror is held by a seat surface provided on a rotating shaft and a ring-shaped member, and a male screw provided on the upper part of the rotating shaft is used. By screwing and tightening a ring-shaped member,
Since the polygon mirror is pressed down with even pressure, there is no local pressure on the polygon mirror, and as a result, the thermal deformation of the polygon mirror due to temperature rise is reduced, and the amount of deformation of the reflecting surface is partially reduced. Different phenomena can be prevented, and the precision of the reflecting surface of the rotating polygon mirror can be maintained with high precision.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a perspective view of an exploded state.

FIG. 3 is a sectional view of a second embodiment.

FIG. 4 is a sectional view of a third embodiment.

[Explanation of symbols]

1　Polygon mirror 3 Through hole 4 Rotation axis 5 Seat surface 6 Flange part 7 Fitting part 8 Male thread part 9 Female thread 10, 13 Ring-shaped member 11 Central part 12 Outer periphery

Claims (1)

[Claims] Claim 1: After fitting a through hole provided at the center of a polygon mirror into a fitting part of a rotating shaft having a male threaded part, a fitting part, and a seat surface in order from the end, a female thread is inserted into the male threaded part. A method for fixing a rotating polygon mirror, characterized in that the polygon mirror is clamped and fixed between the receiving surface and the ring-shaped member by screwing together a ring-shaped member.