JPH06289315A - Optical deflector - Google Patents

Abstract

PURPOSE:To reduce a howling sound generated in a cover when a rotary polygon mirror rotates at a high speed. CONSTITUTION:The rotary polygon mirror 1 which rotates above a 30m/s peripheral speed of the maximum external diameter part 1b of an outer peripheral surface is covered with a nearly cylindrical cover 2 and the difference between the internal diameter of its cylindrical wall 2a and the diameter of the circumscribed circle D of the maximum external diameter part 1b of the rotary polygon mirror 1 is set to 4-12mm. When the difference is <4mm, the wind pressure in the cover 2 rises to generate loud howling sound, but when >12mm, a motor current greatly increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector for deflecting and scanning a laser beam or the like at a high speed in a laser printer or the like.

[0002]

2. Description of the Related Art Optical deflectors for laser printers, laser facsimiles and the like have been particularly accelerated in recent years, and rotary polygon mirrors used for these deflectors rotate at high speeds of 10,000 or more revolutions per minute. When the rotary polygon mirror is rotated at such a high speed, the wind noise during rotation is increased and a large noise is generated. Therefore, the periphery of the rotary polygon mirror is covered with a substantially cylindrical cover.

FIG. 5 illustrates the general structure of a general optical deflector, which is a laser beam L generated from a laser oscillator 110.
₀ is focused into a predetermined beam shape by the cylindrical lens 105, then deflected and scanned by the rotary polygon mirror 101, and passes through the imaging lens system 106 and the photosensitive drum 107.
Image on top. A part of the laser light reflected by the rotating polygon mirror 101 is reflected by the reflecting mirror 108 to the optical fiber 1.
09, and is converted into a scan start signal.

FIG. 4 shows the rotary polygon mirror 101 and its drive unit. The drive unit of the rotary polygon mirror 101 is a rotary shaft 111.
And the rotor magnet 112 integrally connected to the
The rotary polygon mirror 1 includes a stator coil 114 that is integral with a bearing device 113 that supports the rotary shaft 111, and a circuit board 115 that supplies a drive current to the stator coil 114.
01 is a corrugated washer 116a and a flat washer 116b
A pressing mechanism 116 including a stopper ring 116c presses the flange member 111a, which is integrated with the rotating shaft 111, and thereby is integrated with the rotating shaft 111. The rotary polygon mirror 101 is covered with a substantially cylindrical cover 102, which restricts the flow of air accompanying the rotation of the rotary polygon mirror 101, reduces wind noise, and reduces wind noise to the outside. Prevent it from leaking. The cover 10
The second cylindrical portion 102a has a window 10 through which laser light passes.
3 is provided.

[0005]

However, according to the above conventional technique, the rotary polygon mirror has a maximum peripheral speed of 30 on the outer peripheral surface.
When rotating at a high speed of m / s or more, a particularly loud wind noise may occur in the cover.

The present invention has been made in view of the above-mentioned problems of the prior art, and is a wind noise when the rotating polygon mirror rotates at a high speed at a peripheral speed of 30 m / s or more of the maximum outer diameter portion of the outer peripheral surface. It is an object of the present invention to provide an optical deflector capable of reducing the above.

[0007]

In order to achieve the above object, the optical deflector of the present invention comprises a rotary polygon mirror for deflecting and scanning the illumination light irradiated on the outer peripheral surface and a cylindrical portion covering the outer peripheral surface. In an optical deflector having a cover provided with the rotary polygon mirror rotating at a peripheral speed of 30 m / s or more of a maximum outer diameter portion of the outer peripheral surface, a circumscribed circle circumscribing the maximum outer diameter portion of the rotary polygon mirror is provided. The difference between the diameter and the inner diameter of the cylindrical portion of the cover is 4 mm or more.

[0008]

The gap between the rotary polygon mirror and the cylindrical portion of the cover is set by setting the difference between the diameter of the circumscribed circle circumscribing the outermost surface of the rotary polygon mirror and the inner diameter of the cylindrical portion of the cover to be 4 mm or more. The dimension can be 2 mm or more. As a result, it is possible to prevent an increase in wind pressure acting on the outer peripheral surface of the rotary polygon mirror, and reduce wind noise generated in the cover.

[0009]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial schematic cross-sectional view showing the main part of one embodiment. An optical deflector E1 of this embodiment is a rotary polygon mirror 1 which is rotated in the direction of arrow A by a drive mechanism (not shown). The cover 2 is provided with a substantially cylindrical cover 2 which covers a disk-shaped top wall (not shown) and a cylindrical portion which concentrically surrounds the outer peripheral surface of the rotary polygon mirror 1 including the reflecting surface 1a. A cylindrical wall 2a is provided, and the cylindrical wall 2a is irradiated from the light source 3 through the collimator lens 4 and the like to the reflecting surface 1a of the rotary polygon mirror 1, and the window 5 for passing the laser beam L1 deflected and scanned by this. Is equipped with. The laser light reflected by the rotary polygon mirror 1 is focused on a photosensitive drum (not shown) via an imaging lens system 6 having a spherical lens 6a and a toric lens 6b.

Further, the window 5 of the cover 2 has a guide piece 7 on the side edge 5a on the downstream side in the rotation direction of the rotary polygon mirror 1, and the guide piece 7 is provided.
Forms an air flow path 8 with the side surface 6c of the spherical lens 6a. When the rotary polygon mirror 1 rotates at a high speed, the air inside the cover 2 flows at a high speed, and a part of the air is discharged to the outside through the window 5. When the peripheral speed of the maximum outer diameter portion 1b on the outer peripheral surface of the rotary polygon mirror 1 is 30 m / s or more, the wind pressure of the air in the cover 2 may be significantly increased, and a particularly loud wind noise may be generated. A circumscribed circle D in which the inner diameter of the cylindrical wall 2a of the cover 2 circumscribes the maximum outer diameter portion 1b of the rotary polygon mirror 1.
Diameter (hereinafter referred to as "maximum outer diameter of the rotary polygon mirror 1")
Experiments have shown that the noise due to the wind noise can be significantly reduced by increasing the width by 4 mm or more. On the other hand, the inner diameter of the cylindrical wall 2a of the cover 2 and the rotary polygon mirror 1
When the difference between the maximum outer diameters is 12 mm or more, the rotating polygon mirror 1
It was also found that the amount of air flowing along with it increased and the load current of the drive motor of the rotary polygon mirror 1 increased sharply.

2 and 3 show the inner diameter of the cylindrical wall 2a of the cover 2 and the rotary polygon mirror 1 when the peripheral speed of the maximum outer diameter portion 1b of the outer peripheral surface of the rotary polygon mirror 1 is 30 m / s or more. It is a result of investigating the noise of the optical deflector E1 and the change of the motor current when the difference in the maximum outer diameter is changed. From these figures, the difference between the inner diameter of the cylindrical wall 2a of the cover 2 and the maximum outer diameter of the rotary polygon mirror 1 is set within the range of 4 to 12 mm, whereby the maximum of the cylindrical wall 2a of the cover 2 and the rotary polygon mirror 1 is set. By setting the gap dimension h between the outer diameter portions 1b to 2 to 6 mm, the noise of the optical deflector E1 can be significantly reduced, and
It can be seen that an increase in motor current can also be prevented.

According to this embodiment, the cylindrical wall 2a of the cover 2 is
Is set to be 4 to 12 mm larger than the maximum outer diameter of the rotary polygon mirror 1, a guide piece 7 is provided on the cylindrical wall 2a of the cover 2, and the air flowing out from the window 5 is introduced into the flow path 8. By flowing along the side surface 6c of the spherical lens 6a, noise can be reduced by 4 to 6 dB as compared with the conventional optical deflector.

[0014]

Since the present invention is configured as described above, it has the following effects.

The rotating polygon mirror has a peripheral speed of the maximum outer diameter portion of 30 m /
It is possible to prevent a large wind noise from being generated in the cover when rotating at a high speed for s or more. As a result, an optical deflector with less noise can be realized.

[Brief description of drawings]

FIG. 1 is a partial schematic cross-sectional view showing a main part of one embodiment.

FIG. 2 is a graph showing a result of an experiment in which a change in noise due to a change in a difference between an inner diameter of a cylindrical wall of a cover and a maximum outer diameter of a rotary polygon mirror is investigated.

FIG. 3 is a graph showing the results of an experiment in which changes in motor current due to changes in the difference between the inner diameter of the cylindrical wall of the cover and the maximum outer diameter of the rotary polygon mirror were investigated.

FIG. 4 is a partial schematic cross-sectional view showing a main part of a conventional example.

FIG. 5 is an explanatory diagram illustrating the entire conventional optical deflector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating polygon mirror 1a reflective surface 1b maximum outer diameter part 2 cover 2a cylindrical wall 3 light source 5 window 6 imaging lens system 6a spherical lens

Front page continuation (72) Inventor Taku Butada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Noboru Nabeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideyuki Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A rotary polygonal mirror for deflecting and scanning illumination light applied to an outer peripheral surface, and a cover having a cylindrical portion covering the outer peripheral surface, wherein the rotary polygonal mirror has a maximum outer diameter portion of the outer peripheral surface. In the optical deflector rotating at a peripheral speed of 30 m / s or more, the difference between the diameter of the circumscribed circle circumscribing the maximum outer diameter portion of the rotating polygon mirror and the inner diameter of the cylindrical portion of the cover is 4 mm or more. Optical deflector. 2. The optical deflector according to claim 1, wherein the difference is 12 mm or less.