JPH0980341A - Deflection scanning device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To prevent the reflecting surface of a rotating polygon mirror from being contaminated by dust or the like in the outside air. A scanning light L ₁ of a rotary polygon mirror 3 is extracted from a window 8 of an optical box 7 toward a photosensitive drum 5 via a spherical lens 4a and a toric lens 4b. Spherical lens 4a
The lower end of is fixed to a pedestal 11a, and a rib 12 facing the side surface of the spherical lens 4a is provided around the lower end of the pedestal 11a to block the air flow that bypasses the bottom surface of the spherical lens 4a by the labyrinth effect. A filling material 13 such as urethane foam is provided between the upper surface of the spherical lens 4a and the lid member 9 to block an air flow that bypasses the upper surface of the spherical lens 4a.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As shown in FIGS. 11 and 12, a deflection scanning device used in an image forming apparatus such as a laser printer or a laser facsimile linearly converts a laser beam generated from a light source unit 101 into a linear lens 102. The light is condensed into a light beam, and is deflected and scanned by the rotary polygon mirror 103 in a predetermined direction (hereinafter, referred to as “Y-axis direction”) perpendicular to a direction along the rotation axis (hereinafter, referred to as “Z-axis direction”). , Spherical lens 104a and toric lens 104
b through the image forming lens system 104 including the photosensitive drum 105
Image on top. The light flux that forms an image on the photosensitive drum 105 is
An electrostatic latent image is formed by main scanning in the Y-axis direction by rotation of the rotary polygon mirror 103 and sub-scanning in the Z-axis direction by rotation of the photosensitive drum 105.

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

A light source unit 101, a cylindrical lens 102, a rotating polygon mirror 103, an imaging lens system 104, B
The D mirror 106a and the BD sensor 106b are the optical box 1
It is attached to the side wall and bottom wall of 07. Photosensitive drum 105
Is disposed outside the optical box 107, and the optical box 107
A window 108 for taking out the scanning light L ₀ from the optical box 107 toward the photosensitive drum 105 is provided on the side wall of the. The upper opening of the optical box 107 is closed by a lid member 109 shown only in FIG.

Each of the optical box 107 and the lid member 109 has a partition wall 10 protruding toward the spherical lens 104a.
7a (see FIG. 11) and a projecting portion 109a (see FIG. 12) so that the internal space of the optical box 107 faces the space portion 110a around the rotary polygon mirror 103 and its driving portion 103a and the window 108. Divided into parts 110b,
It is devised to prevent a large amount of outside air from flowing into the optical box 107 through the window 108 due to the suction force generated by the rotation of the rotary polygon mirror 103.

[0006]

However, according to the above-mentioned conventional technique, the amount of the outside air flowing around the rotary polygon mirror cannot be sufficiently reduced only by the protrusion provided on the partition wall or the lid of the optical box. At the same time, the intruded dust accumulates on and around the motor of the rotating polygon mirror. There is an unsolved problem that such dust rises every time the motor rotates and contaminates the reflecting surface of the rotary polygon mirror significantly, and the optical performance of the deflection scanning device is greatly impaired.

Lenses such as the spherical lens 104a and the toric lens 104b are provided with a plurality of pedestals 107 that project upward from the bottom wall of the optical box 107, as shown in FIG.
each lens 104a, which is fixed to the lens b by adhesion or the like.
For example, 1 mm is provided between the bottom surface of 104b and the bottom wall of the optical box 107 in a portion where the pedestal 107b is not provided.
Since a small gap is left, when the rotary polygon mirror 103 rotates at a high speed, an airflow is sucked from the gap, and the dust carried by this airflow contaminates the reflecting surface of the rotary polygon mirror.
In particular, color toners such as color toners that do not contain a magnetic material tend to float inside the image forming apparatus, and therefore, even an extremely minute gap can be passed along the airflow. Therefore, in the color image forming apparatus, the contamination of the reflecting surface of the rotating polygon mirror tends to proceed more rapidly.

In addition, even when the rotary polygon mirror is stopped,
When the cooling fan continues to be rotated so that the operation of the deflection scanning device can be immediately started, the forcedly flowing outside air enters the optical box and contaminates the reflecting surface of the rotating polygon mirror as described above.

When the reflecting surface of the rotary polygon mirror is contaminated by such outside air, the frequency of cleaning the reflecting surface of the rotary polygon mirror or replacing the rotary polygon mirror increases, and the maintenance cost significantly increases.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and the bottom surface of an imaging lens such as a spherical lens or a toric lens is provided in the atmosphere around the rotary polygon mirror and its driving portion. It is an object of the present invention to provide a deflection scanning device that can prevent the outside air from entering by bypassing and can significantly reduce the maintenance cost of a rotary polygon mirror.

[0011]

In order to achieve the above object, a deflection scanning device of the present invention comprises a rotary polygon mirror and at least one image forming means for forming an image of a light beam deflected and scanned by the polygon mirror on a photosensitive member. A lens, accommodating means for accommodating the rotary polygon mirror in a predetermined space, and dustproof means for bypassing the bottom surface of the imaging lens and preventing dust from entering the predetermined space of the accommodating means. It is characterized by having.

It is preferable that the dustproof means has a barrier which is disposed integrally with the bottom wall of the housing means in the vicinity of the imaging lens.

Further, it is preferable that the dust-proof means has a filler disposed between the lid member of the accommodating means and the imaging lens.

The dustproof means may have a second barrier protruding from the lid member of the housing means in the vicinity of the imaging lens.

The dustproof means has a rib-shaped member for locally reducing the gap formed between the bottom surface of the imaging lens and the bottom wall of the housing means, and the rib-shaped member is the length of the imaging lens. It is good to extend in the direction.

[0016]

When outside air invades a predetermined space of the optical box accommodating the rotating polygon mirror from around the imaging lens, dust in the outside air adheres to the reflecting surface of the rotating polygon mirror to reduce the reflectance. Therefore, a barrier that protrudes from the bottom wall of the accommodating means to the vicinity of the imaging lens is provided to prevent outside air from entering due to the labyrinth effect or the like. In addition, the gap formed between the lid member of the accommodating means and the imaging lens is filled with a filling material such as urethane foam to block the outside air.

Further, by locally reducing the gap formed between the bottom surface of the imaging lens and the bottom wall of the accommodating means by the rib-like member, dust having a predetermined particle size or more passes through the gap. To prevent completely. In this way, it is possible to prevent dust from entering the atmosphere around the rotary polygon mirror and its drive unit, and to realize a deflection scanning device in which the reflecting surface of the rotary polygon mirror is not likely to be rapidly polluted.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing a deflection scanning device according to the first embodiment, which is a laser beam L ₁ which is a light beam generated from a light source 1 (see FIG. 2) and is transmitted by a cylindrical lens 2. It is condensed into a linear light beam, deflected and scanned in a predetermined scanning direction by the rotary polygon mirror 3, and passes through an imaging lens system 4 including a spherical lens 4a which is an imaging lens and a toric lens 4b, and a photosensitive drum which is a photoconductor. Image on 5. The luminous flux that forms an image on the photosensitive drum 5 is the rotating polygon mirror 3.
To form an electrostatic latent image by the main scanning by the rotation and the sub-scan by the rotation of the photosensitive drum 5.

The rotary polygon mirror 3 is rotated by a drive unit 3a. The scanning light L ₁ of the rotary polygon mirror 3, which reaches one end of the scanning surface, is introduced into a BD sensor (not shown), converted into a scanning start signal, and transmitted to the light source. The light source 1 starts the write modulation after receiving the scanning start signal.

The light source 1, the cylindrical lens 2, the rotary polygonal mirror 3, the imaging lens system 4, the BD sensor and the like are attached to the side wall and the bottom wall of an optical box 7 which is integral with the body frame 6 of the deflection scanning device. The photosensitive drum 5 is arranged outside the optical box 7, and the scanning light L ₁ is applied to the optical box 7 on the side wall of the optical box 7.
A window 8 is provided for taking out from the photosensitive drum 5 toward the photosensitive drum 5. Further, the upper opening of the optical box 7 is closed by a lid member (cover) 9 which constitutes a housing means together with the optical box 7.

The spherical lens 4a and the toric lens 4b of the imaging lens system 4 are respectively supported on lens supports 10a and 10b provided integrally with the bottom wall of the optical box 7. Each of the lens supports 10a and 10b has a plurality of pedestals 11a and 11b for positioning on the upper surface thereof, and a spherical lens 4a, after applying an ultraviolet curable adhesive to them.
The toric lens 4b is placed and ultraviolet rays are irradiated to cure the adhesive. The method of fixing the spherical lens 4a and the toric lens 4b to the pedestals 11a and 11b is not limited to the method using the adhesive as described above.

Lens support 1 for supporting the spherical lens 4a
Reference numeral 0a has a rib 12 that is a dustproof means (barrier) that projects upward in the vicinity of the lower end of the spherical lens 4a.
The height H _{1 of} 2 is larger than the distance D to the side surface of the spherical lens 4a, and the height H ₂ of the spherical lens 4a exceeds the height H ₂ of the pedestal 11a of the spherical lens 4a so as to face both side surfaces of the spherical lens 4a. It

That is, H ₁ ≧ D H ₁ > H _{2 Further} , it is desirable that the height H ₂ of the pedestal 11a of the spherical lens 4a be lower in order to make the void formed below the spherical lens 4a as small as possible. However, if it is too low, inconvenience will occur in positioning the spherical lens 4a. Therefore, it is generally set to about 0.3 mm.

The rib 12 shields the void formed at the lower end of the spherical lens 4a by the so-called labyrinth effect,
It serves to prevent dust and the like in the outside air from bypassing the lower end (bottom surface) of the spherical lens 4 a and entering the atmosphere around the rotary polygon mirror 3.

Further, the upper end of the spherical lens 4a and the lid member 9
The space is filled with a filling material 13 which is an elastic dustproof means such as urethane foam commercially available under the trade name Moltoprene, and the filling material 13 is similar to the rib 12 in the upper end (upper surface of the spherical lens 4a. ) To prevent dust from entering the atmosphere around the rotary polygon mirror 3.

As shown in FIG. 3, both ends of the filling material 13 are held by holders 13a which are integral with the side walls of the optical box 7, and when the lid member 9 is fixed to the optical box 7 by means of screws or the like, it is slightly It is configured so that it is compressed into close contact with the lid member 9.

If the filler 13 is held by the holder 13a, the filler 13 may be displaced before the lid member 9 is attached, and the workability of the assembly may be impaired. Therefore, as shown in FIG. 4, the central portion, which is a part of the filler 13 in the longitudinal direction, may be attached to the spherical lens 4 a by the double-sided adhesive tape 14. Further, as shown in FIG. 5, the filling material 23 may be fixed to the lid member 9 with the double-sided adhesive tape 24.

According to this embodiment, it is possible to effectively prevent dust in the outside air from bypassing the upper surface and the bottom surface of the spherical lens and entering the atmosphere around the rotary polygon mirror. Even if the suction force of the outside air due to the rotation of the rotating polygon mirror increases due to high-speed rotation, or if cold air is generated to cool the cartridge and the power supply device inside the main body of the image forming apparatus, the rotating polygon mirror There is no possibility that dust will enter the surrounding atmosphere and the reflecting surface of the rotating polygon mirror will be rapidly contaminated. Therefore, the frequency of exchanging the rotary polygon mirror or cleaning the reflection surface due to contamination of the reflective surface of the rotary polygon mirror can be reduced, and the maintenance cost can be significantly reduced.

The same effect can be expected by arranging a filler or ribs for blocking the outside air around the toric lens instead of arranging it around the spherical lens.

FIG. 6 is a schematic cross-sectional view showing a deflection scanning device according to the second embodiment. Instead of the filling material 13 of the first embodiment, a recessed portion is formed in a lid member 39 that closes the upper opening of the optical box 7. 39a is provided, and this is provided close to the upper surface of the spherical lens 4a, and the rib 32 which is the second barrier protruding from the recess 39a to the inside of the optical box 7 is provided.
The second rib 32 has the same structure as the rib 12 of the optical box 7, and blocks the air flow that bypasses the upper surface of the spherical lens 4a by the labyrinth effect.

The rotary polygon mirror 3, the toric lens 4a, the photosensitive drum 5, the optical box 7 and the like are the same as those in the first embodiment, so they are designated by the same reference numerals and their description is omitted.

According to the present embodiment, the air flow that bypasses the bottom surface and the top surface of the spherical lens is effectively blocked by the first and second ribs to prevent the reflection surface of the rotary polygon mirror from being contaminated, and the filling material is used. By omitting it, the number of assembly parts of the apparatus can be reduced, and the cost reduction of the image forming apparatus can be greatly promoted.

FIG. 7 is a schematic plan view showing the deflection scanning device according to the third embodiment with the lid member removed.
This is because a laser beam, which is a light beam generated from the light source unit 41, is condensed into a linear light beam by the cylindrical lens 42, and a direction along the rotation axis thereof by the rotating polygon mirror 43 (hereinafter, “Z axis direction”). Deflection scanning in a predetermined direction (hereinafter referred to as “Y-axis direction”) perpendicular to
An image is formed on the photosensitive drum 45 (see FIG. 8) through a known image forming lens 44 having an fθ function. The light flux imaged on the photosensitive drum 45 forms an electrostatic latent image by main scanning in the Y-axis direction by rotation of the rotary polygon mirror 43 and sub-scanning in the Z-axis direction by rotation of the photosensitive drum 45.

The scanning light from the rotary polygon mirror 43 has a BD mirror 46 at one end of the scanning surface (XY plane) in the Y-axis direction.
The BD sensor 4 is separated below the scanning surface by a.
6b, converted into a scanning start signal and transmitted to the semiconductor laser of the light source unit 41. The semiconductor laser starts writing modulation after receiving the scanning start signal.

The light source unit 41, the cylindrical lens 42, the rotary polygon mirror 43, the imaging lens 44, and the BD mirror 4
6a and the BD sensor 46b are attached to the side wall and the bottom wall of the optical box 47. The photosensitive drum 45 is disposed outside the optical box 47, and a side wall of the optical box 47 is provided with a window 48 for taking out scanning light from the optical box 47 toward the photosensitive drum 45. Further, the upper opening of the optical box 47 is a lid member 49 that constitutes a housing means together with the optical box 47.
Is blocked by.

The bottom surface of the imaging lens 44 is brought into contact with the contact reference surfaces (upper surfaces) of the three contact members 50 provided upright on the bottom wall of the optical box 47, and also on the bottom wall of the optical box 47. The thickness applied to the upper surfaces of the pair of standing bases 51 is 0.05 to 0.
It is fixed to the pedestal 51 with an adhesive of about 1 mm.

A space between both side surfaces of the imaging lens 44 and the side wall of the optical box 47 is closed by a protrusion 47a provided on the side wall, and outside air bypasses both side surfaces of the imaging lens 44 to rotate the polygon mirror 43. Prevents intrusion around.

The bottom wall of the optical box 47 is formed by the imaging lens 4
Ribs 52, which are barriers provided upright near the lower end of
And a rib-shaped projection 53, which is a rib-shaped member standing upright toward the bottom surface of the imaging lens 44, and the rib-shaped projection 53 constitutes dust-proof means together with the rib 52. As shown in FIG. 8B, the distance D between the rib 52 and the surface of the imaging lens 44 facing the rib 52 is selected to be approximately 1 mm in consideration of the shape accuracy and the positioning accuracy of the imaging lens 44. It has a function of reducing the amount of air that bypasses the bottom surface of the imaging lens 44 by the same labyrinth effect as the rib 12 in the first and second embodiments. The distance D is 2 mm
Experiments have shown that the following is sufficient to prevent outside air from bypassing the imaging lens 44 and entering around the rotating polygon mirror 43.

Further, the rib-shaped projection 53 is formed on the imaging lens 44.
Extends along the entire length of and has a width W of 1.0 to 3.0
2 mm of the above-mentioned three contact members 50 set to mm.
The rib-like protrusions 53 are integrally formed near both ends of the rib-like protrusions 53.

As described above, the imaging lens 44 is the optical box 4
The bottom wall of the optical box 47 and the bottom surface of the imaging lens 44 are fixed to the bottom wall of the optical box 47 by an adhesive applied to the abutment member 50 of the bottom wall of No. 7 and applied to the pedestal 51. In general, when the particle size of the dust in the outside air that enters the optical box 47 is small, the amount of outside air that bypasses the bottom surface of the imaging lens 44 is set as a rib. 5
Even if it is reduced by the labyrinth effect of 2, the particle size is 0.2
Fine particles of about mm or less are formed on the imaging lens 4
It is difficult to avoid bypassing the bottom surface of No. 4 and contaminating the reflective surface of the rotating polygon mirror 43.

The reason why the separation distance between the bottom wall of the optical box 47 and the bottom surface of the imaging lens 44 is required to be about 0.3 mm is that the bottom wall of the optical box 47 has a large surface area and therefore has a flatness of 0.1 to 0.1.
The limit is 0.2 mm, and in addition, an error of about ± 0.05 mm is inevitable in the surface accuracy of the contact reference surface of the contact member 50 that contacts the bottom surface of the imaging lens 44. This is because.

On the other hand, the dust in the outside air entering the optical box 47 has a particle size of 0.5 μm in a normal office environment.
It is roughly classified into the following and 0.2 mm or more, and it is the particle diameter of 0.2 mm that significantly contaminates the reflective surface of the rotating polygon mirror 43.
The above is dust. Therefore, by providing a rib-shaped projection 53 projecting toward the bottom surface of the imaging lens 44 on the bottom wall of the optical box 47, a gap between the bottom surface of the imaging lens 44 and the bottom wall of the optical box 47 is locally formed. And the dust with a particle size of 0.2 mm or more bypasses the bottom surface of the imaging lens 44 and rotates the polygon mirror 43.
Avoid getting around.

The width W of the rib-shaped projection 53 is 0.
Since it is as narrow as about 1 to 0.3 mm, its flatness can be suppressed to about 0.05 mm by general finishing. Even if an error of ± 0.3 mm in the surface accuracy of the contact reference surface of the contact member 50 is added to this, the gap B between the upper ends of the rib-shaped projections 53 and the bottom surface of the imaging lens 44 should be 0.08 mm. is there. That is, by providing the rib-shaped projections 53, the size of the gap between the bottom wall of the optical box 47 and the bottom surface of the imaging lens 44 is locally reduced to about 0.1 to 0.15 mm, and the particle size is 0.2 mm. Completely block the above dust intrusion.

As described above, the present embodiment reduces the amount of outside air that bypasses the bottom surface of the imaging lens by the labyrinth effect of the ribs arranged in the vicinity of the imaging lens, and also moves toward the bottom surface of the imaging lens. Most of the dust that contaminates the reflective surface of the rotating polygon mirror is reduced by locally reducing the gap between the bottom surface of the imaging lens and the bottom wall of the optical box by a rib-shaped protrusion protruding from the bottom wall of the optical box. Shut off. Thereby, the maintenance cost of the rotary polygon mirror can be significantly reduced.

The gap between the imaging lens 44 and the lid member 49 is sealed by a filler 47b disposed between them. The filler 47b is the filler 1 of the first embodiment.
Similar to 3, urethane foam and the like, which are commercially available under the trade name Moltoprene, are used. Also, the filler 47b
The assembling is performed by press-fitting both ends thereof between the holding members 47c provided on the side wall of the optical box 47.

The number of rib-like protrusions protruding from the bottom wall of the optical box toward the bottom surface of the imaging lens is not limited to one, and if two or more ribs are provided in parallel, the dustproof effect is improved.

Further, as shown in FIG. 9, the imaging lens 4
If a recess 64 facing the rib-shaped projection 53 is provided on the bottom surface of 4, the labyrinth effect similar to that of the rib 52 is added, and the dustproof effect is further improved. In this case, the imaging lens 4
The gap C between the bottom surface of the recess 64 of No. 4 and the rib-shaped projection 53 is set to be about 0.1 to 0.15 mm.

Further, as shown in FIG. 10, ribs 52 projecting from the bottom wall of the optical box 47 to both front and rear sides of the imaging lens 44.
By providing a and 52b, the dustproof effect can be further improved.

[0050]

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

It is possible to prevent dust from invading the atmosphere of the rotary polygon mirror and its drive unit by bypassing the bottom surface of the imaging lens such as a spherical lens or toric lens, and to significantly reduce the maintenance cost of the deflection scanning device. . By using such a deflection scanning device, speeding up of the image forming apparatus can be promoted and the cost of maintenance can be greatly reduced.

[Brief description of drawings]

1A and 1B show a first embodiment, FIG. 1A is a schematic sectional view of the same, and FIG. 1B is an enlarged partial sectional view showing an area around a spherical lens in an enlarged manner.

FIG. 2 is a schematic cross-sectional view taken along the line AA of FIG.

FIG. 3 is a schematic plan view showing the device of FIG. 1 with a lid member removed.

FIG. 4 is a partial schematic cross-sectional view taken along the line BB in FIG.

FIG. 5 is a partial schematic cross-sectional view showing a modification of the first embodiment.

FIG. 6 is a schematic sectional view showing a second embodiment.

FIG. 7 is a schematic plan view showing a third embodiment with the lid member removed.

8A and 8B are sectional views showing the apparatus of FIG. 7, wherein FIG. 8A is a schematic sectional view showing the whole thereof, and FIG. 8B is an enlarged partial sectional view showing a part of FIG.

FIG. 9 is an enlarged partial sectional view showing a modification of the third embodiment.

FIG. 10 is an enlarged partial sectional view showing still another modification of the third embodiment.

FIG. 11 is a schematic plan view showing a conventional example with a lid member removed.

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

[Explanation of symbols]

 3,43 Rotating polygonal mirror 3a Drive part 4a Spherical lens 4b Toric lens 5,45 Photosensitive drum 7,47 Optical box 8,48 Window 9,49 Lid member 12,32,52,52a, 52b Rib 13,23,47b Filling Material 44 Imaging lens 53 Rib-shaped projection

Claims (8)

[Claims] 1. A rotary polygon mirror, at least one imaging lens for forming an image of a light beam deflected and scanned by the rotary polygon mirror on a photoconductor, and a housing means for housing the rotary polygon mirror in a predetermined space. A deflection scanning device having a dust-preventing means for preventing dust from entering the predetermined space of the housing means by bypassing the bottom surface of the imaging lens. 2. The deflection scanning device according to claim 1, wherein the dust-proof means has a barrier which is disposed integrally with the bottom wall of the housing means in the vicinity of the imaging lens. 3. The deflection scanning device according to claim 1, wherein the dustproof means has a filling material disposed between the lid member of the housing means and the imaging lens. 4. The deflection scanning device according to claim 1, wherein the dust-proof means has a second barrier protruding from the lid member of the housing means in the vicinity of the imaging lens. 5. The filling material is attached to the lid member or the imaging lens using a double-sided adhesive tape, and the double-sided adhesive tape is attached to a part of the filling material in the longitudinal direction. 3. The deflection scanning device according to item 3. 6. The dustproof means has a rib-shaped member for locally reducing a gap formed between the bottom surface of the imaging lens and the bottom wall of the housing means, and the rib-shaped member of the imaging lens is provided. 6. The deflection scanning device according to claim 1, wherein the deflection scanning device extends in the length direction. 7. The deflection scanning device according to claim 6, wherein the rib-shaped member is disposed so as to face a recess provided in the bottom surface of the imaging lens. 8. The size of the gap formed between the bottom surface of the imaging lens and the bottom wall of the accommodating means is locally reduced to 0.15 mm or less. Deflection scanning device.