JPH0915522A - Scanning optical device - Google Patents

Abstract

(57) [Summary] [Purpose] It prevents the mirror from turning back when the lid is attached to the optical box and changing the reflection angle of the mirror. The scanning light L ₁ deflected and scanned by the rotary polygon mirror 3 forms an image on a rotating drum 6 via an imaging lens 4 and a folding mirror 5. An upper opening of the optical box 7 that houses the rotary polygon mirror 3 and the turning mirror 5 is closed by a lid 9. The side wall 7a of the optical box 7 has a stepped portion 7d in the vicinity of the folding mirror 5, and is configured so as not to come into contact with the lid 9 at this portion. To be done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device used in an image forming apparatus such as a laser printer or a laser facsimile.

[0002]

2. Description of the Related Art As shown in FIG. 5, a scanning optical device used in an image forming apparatus such as a laser printer or a laser facsimile linearly scans a laser beam generated from a light source unit 101 having a semiconductor laser 101a with a cylindrical lens 102. -Shaped light flux is condensed to form a rotary polygon mirror 103.
Direction along the axis of rotation (hereinafter, "Z-axis direction")
That. ) Is deflected and scanned in a predetermined direction (hereinafter, referred to as “Y-axis direction”) perpendicular to)), and passes through an imaging lens system 104 including a spherical lens 104a and a toric lens 104b and a folding mirror 105, and a rotary drum D ( (See Figure 6)
Form an image on the upper photoconductor. The light beam formed on the photoreceptor forms an electrostatic latent image by the main scanning in the Y-axis direction by the rotation of the rotary polygon mirror 103 and the sub-scanning in the Z-axis direction by the rotation of the rotary drum D.

The scanning light L ₀ from the rotary polygon mirror 103 is separated by a BD mirror 106 a below the scanning surface at one end of the scanning surface (XY plane) in the Y-axis direction, introduced into a BD sensor 106 b, and starts scanning. The light is converted into a signal and transmitted to the semiconductor laser 101a of the light source unit 101. The semiconductor laser 101a starts the write modulation after receiving the scanning start signal.

A light source unit 101, a cylindrical lens 102, a rotary polygon mirror 103, an imaging lens system 104, a turning mirror 105, a BD mirror 106a and a BD.
The sensor 106b and the like are attached to the side wall 107a and the bottom wall 107b of the optical box 107. The rotating drum D is an optical box 10.
7 is provided below the bottom wall 107 of the optical box 107.
In b, a window 108 is provided for taking out the scanning light L ₀ reflected by the folding mirror 105 from the optical box 107 toward the rotary drum D. Further, as shown in FIG. 6, the upper opening of the optical box 107 is closed by a lid 109.

[0005]

However, according to the above-mentioned conventional technique, the lid for closing the upper opening of the optical box is usually made of metal or resin, and is abutted on the upper end of the side wall of the optical box and fixed with screws. Alternatively, it is fixed to the side wall of the optical box by a known snap fit (patching).

However, as shown in FIG.
When the upper end of the side wall 107a of the optical box 107 is brought into contact with the upper end of the optical box 107 with a screw, the side wall 107a of the optical box 107 is inclined outwardly as indicated by an arrow A ₁ due to bending of the lid 109 and variation in flatness. Occurs. When such an inclination occurs near the turning mirror 105, the reflection angle of the turning mirror 105 changes and the image forming point on the rotating drum D shifts in the direction indicated by the arrow A _2. If the paper is tilted, the margin width of the printing paper is changed, or the image formation position is significantly displaced, an abnormality such as laser light being eclipsed by another component occurs, and the image formation itself May not be possible.

For example, if the lid 109 is made of metal, the flatness is about 0.3 mm even if a good quality flat plate with little bending is used, and there are minute bendings and flatness variations within this range. However, if the rigidity of the lid 109 is large, the side wall 107a of the optical box 107 is inclined and the above-mentioned trouble occurs.

Further, as shown in FIG. 8, a lid 2 made of resin is used.
The locking claw 209a is provided on the side wall 09 of the optical box 207.
The locking claw 209a is provided on the locking portion 207b formed on the 7a.
A so-called snap fit that locks the lid 2
When 09 is fixed to the optical box 207, as shown by an arrow B ₁ , the side wall 207a of the optical box 207 has an inward inclination opposite to the above, which causes the folding mirror 20.
The reflection angle of 5 changes and the image forming point on the rotating drum D is indicated by the arrow B.
_As shown in ₂ , shift in the opposite direction. As a result, when the image is tilted, the width of the margin of the printing paper is changed, or the image forming position is significantly displaced, the laser beam is eclipsed by other components to form an image as described above. Becomes impossible.

For example, when the distance from the reflection point of the turning-back mirror 205 to the image forming point on the rotating drum D is 100 mm, the turning-back mirror 205 can be tilted only by an angle of 10 minutes to form the image forming point. Results in a shift of 0.58 mm.

The present invention has been made in view of the above problems of the prior art. When the lid is assembled to the optical box, the reflection angle of the mirror is changed to change the reflection angle of the mirror and the image forming point of the laser beam. It is an object of the present invention to provide a high-performance scanning optical device that is free from misalignment.

[0011]

In order to achieve the above object, a scanning optical device of the present invention comprises a scanning optical system having a rotating polygon mirror and a folding device for reflecting a laser beam scanned by the scanning optical system toward a photosensitive member. A return mirror, an optical box that houses the scanning optical system and the return mirror, and a lid that closes an opening of the optical box, and the lid and the optical box include the return mirror. It is characterized in that they are not in contact with each other in the vicinity of the mirror and are fixed to each other in the rest.

It is preferable that the lid and the optical box are fixed to each other by screws.

The lid and the optical box may be fixed to each other by a snap fit.

At least one of the lid and the optical box may have a stepped portion near the folding mirror.

The lid may be plastically deformed in the vicinity of the folding mirror.

An elastic material may be provided between the lid and the optical box in the vicinity of the folding mirror.

[0017]

[Function] If the lid and the optical box are folded back and are in contact with each other in the vicinity of the mirror, when the lid is fixed to the optical box by screwing or snap-fitting, the optical element located near the folding mirror is located. The side wall of the box may be tilted due to the bending of the lid or the unevenness of the flatness, which may change the reflection angle of the folding mirror. Therefore, in the vicinity of the folding mirror, a gap is formed between the lid and the optical box so that they are not in contact with each other, and a fixing portion for screwing or snap-fitting is provided on the remaining portion.

If an elastic material is provided between the lid and the optical box in the vicinity of the folding mirror, the gap between the lid and the optical box is sealed by this and dust and the like in the atmosphere penetrates into the optical box. Can be prevented.

[0019]

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

FIG. 1 is a schematic sectional view showing a scanning optical device according to an embodiment, and FIG. 2 is a plan view showing the device of FIG. 1 with a lid removed. Laser light generated from a light source unit 1 having a semiconductor laser 1a is condensed into a linear light beam by a cylindrical lens 2 and deflected and scanned by a rotary polygon mirror 3 in a predetermined scanning direction perpendicular to the direction along the rotation axis. Then, an image is formed on the photoconductor on the rotating drum 6 via the image forming lens 4 and the folding mirror 5 which form the scanning optical system together with the rotary polygon mirror 3. The light flux that forms an image on the photoconductor is rotated by the rotary polygon mirror 3 and is scanned by the rotary drum 6.
An electrostatic latent image is formed by sub-scanning by rotation of the.

The scanning light L ₁ of the rotary polygon mirror 3, which has reached one end of the scanning surface, is introduced into a BD sensor (not shown), converted into a scanning start signal and transmitted to the semiconductor laser 1a of the light source unit 1. . The semiconductor laser 1a receives the scanning start signal and then starts the write modulation.

The light source unit 1, the cylindrical lens 2, the rotary polygonal mirror 3, the imaging lens 4, and the folding mirror 5
Etc. are attached to the side wall 7a and the bottom wall 7b of the optical box 7.
The rotary drum 6 is disposed below the optical box 7, and the scanning light L ₁ that is reflected by the mirror 5 and is reflected on the bottom wall 7b of the optical box 7 from the optical box 7 toward the rotary drum 6. A window 8 for taking out is provided. Also, optical box 7
The upper opening of the is closed by a lid 9.

The lid 9 is made of a metal plate material, abuts on the upper end of the side wall 7a of the optical box 7, and is screwed by a screw (not shown) screwed into a screw hole 7c of the side wall 7a. The side wall 7a of the optical box 7 has a step portion 7d so that a predetermined gap S is formed between the side wall 7a and the lid 9 near the folding mirror 5, and as shown in FIGS. The screw hole 7c is provided in the remaining portion of the side wall 7a except the step portion 7d. Further, the lid 9 has a bent portion 9a for preventing a large amount of air from being sucked into the optical box 7 from the gap S.

In this manner, the lid 9 is brought into contact with the side wall 7a of the optical box 7 and fixed to the side wall 7a of the remaining portion of the optical box 7 except the vicinity of the mirror 5. In the vicinity of the folding mirror 5, a gap S is formed between the lid 9 and the side wall 7a of the optical box 7.
Since the lid 9 and the optical box 7 are not in contact with each other, even if the lid 9 is bent or the flatness varies, the side wall 7a is tilted in the vicinity of the folding mirror 5. There is no possibility that the image forming point on the rotary drum 6 is displaced due to the change of the reflection angle of the folding mirror 5 unlike the conventional example. That is, when the lid 9 is attached to the optical box 7, it is prevented that the reflection angle of the folding mirror 5 is changed and the image is deteriorated and the margin width of the printing paper is varied, and the height of the image forming apparatus is increased. It is possible to greatly promote definition and the like.

A screw hole 7 provided on the side wall 7a of the optical box 7
It is desirable that c is separated from the folding mirror 5 as far as possible, but if it is too far apart, it causes inconvenience such as rattling of the lid 9. Therefore, the folding back mirror 5 is arranged at a position where the influence on the mirror 5 is small and the lid 9 can be firmly fixed. For example, if the lid 9 is made of metal, considering the rigidity and flatness of the lid 9, the distance between the screw hole 7c closest to the folding mirror 5 and the folding mirror 5 is 20 m.
It is sufficient to configure them so that they are separated by m or more.

Further, the step portion 7d on the side wall 7a of the optical box 7 is formed.
The size of the gap S formed between the lid 9 and the lid 9 is such that the lid 9 is made of metal, the flatness is difficult to be obtained, and the bent portion 9a makes the lid 9 highly rigid. Even if the reference numeral 9 slightly touches the side wall 7a of the optical box 7, the side wall 7a may be tilted. If the lid is made of a flat metal plate without the bent portion 9a, the size of the gap S may be about 0.3 mm.

FIG. 4 shows three modified examples of the present embodiment. In the first modified example shown in FIG. 4A, the lid 19 is made of resin and is screwed to the optical box 17. Instead, it is fixed by a snap fit, and a step portion is provided on the lid 19 instead of providing a step portion on the side wall 17a of the optical box 17.
9a is provided. In this way, the resin lid 19
If so, the lid 1 near the folding mirror 15
The size of the gap formed between 9 and the side wall 17a of the optical box 17 needs to be about 1 mm.

In the second modified example shown in FIG. 4B, instead of providing a stepped portion on the lid 29, a part of the lid 29 is plastically deformed and folded back.
7 is configured so as to float from the upper end of the side wall 27a, and the third modification shown in FIG.
An elastic material 3 such as urethane foam is provided between the lid 39 and the side wall 37a of the optical box 37 near the folding mirror 35.
8, the lid 39 prevents the side wall 37a from tilting, and seals the side wall 37a and the lid 39 to prevent dust and the like from entering the optical box 37. According to this modification, there is an added advantage that the imaging lens and the rotary polygon mirror in the optical box can be prevented from being contaminated and the maintenance cost can be significantly reduced.

[0029]

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

When the lid is assembled to the optical box, it can be prevented from turning back and changing the reflection angle of the mirror to shift the image forming point of the laser light. As a result, it is possible to realize an extremely high-performance scanning optical device that does not have a problem such as an image being tilted or the margin of the printing paper is uneven.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a scanning optical device according to one embodiment.

FIG. 2 is a plan view showing the scanning optical device of FIG. 1 with a lid removed.

3 is a partial perspective view showing a portion of the apparatus of FIG.

FIG. 4 is a partial schematic cross-sectional view showing a main part of each of first to third modifications.

FIG. 5 is a plan view showing a conventional example.

6 is a schematic cross-sectional view showing the device of FIG.

FIG. 7 is a diagram illustrating a case where an outward inclination occurs on a side wall of the optical box in the conventional example of FIG.

FIG. 8 is a diagram illustrating a case where an inward tilt is generated on the side wall of the optical box in another conventional example.

[Explanation of symbols]

 3 rotating polygon mirror 4 imaging lens 5, 15, 25, 35 folding mirror 6 rotating drum 7, 17, 27, 37 optical box 7d, 19a step 8 window 9, 19, 29, 39 lid 38 elastic material

Claims (6)

[Claims] 1. A scanning optical system having a rotating polygonal mirror, a return mirror for reflecting a laser beam scanned by the scanning mirror toward a photoconductor, and the scanning optical system and the return mirror. And an optical box for closing the opening of the optical box, the lid and the optical box are in non-contact with each other in the vicinity of the folding mirror and are fixed to each other in the remaining portion. A scanning optical device characterized by the above. 2. The scanning optical device according to claim 1, wherein the lid and the optical box are fixed to each other by means of screws. 3. The scanning optical device according to claim 1, wherein the lid and the optical box are fixed to each other by a snap fit. 4. At least one of the lid and the optical box,
4. The scanning optical device according to claim 1, wherein a step portion is provided near the folding mirror. 5. The lid is plastically deformed in the vicinity of the folding mirror.
The scanning optical device according to claim 1. 6. The scanning optical device according to claim 1, wherein an elastic material is provided between the lid and the optical box in the vicinity of the folding mirror.