JPS6021066A - Optical beam printer - Google Patents

Abstract

PURPOSE:To prevent an optical system from dirt by arranging plural dividing walls having slits and a dust removing box provided with a space for settling dust between the dividing walls on an optical beam projection port part of an exposure optical means. CONSTITUTION:A scanning/exposure optical means 18 related to the exposure optical means is stored in an optical box 19 to be protected from external dust and a scanning beam scans and exposes the surface of a photosensitive drum 7A through a rotary polyhedron mirror 5A, and Ftheta lens 6A, reflecting mirrors 20, 21, and a cylindrical lens 8A. A slitlike opening part 19b is formed on the laser beam projection port part 19a of the optical box 19 to project the laser beam and the optical box 19 is joined with the attachable/detachable dust removing box 22 as a unit including the cylindrical lens 8A to constitute a closed space.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a light beam printer, and in particular, a light beam printer that scans and exposes the surface of a photoconductive photoreceptor to a laser beam or the like to form an electrostatic latent image. This invention relates to a light beam printer that develops this electrostatic latent image with fine powder toner.

[Background of the invention]

A laser beam printer, which is a type of light beam printer, uses a deflection mirror, Fθ, that rotates or swings around a spindle in order to scan and expose the surface of a uniformly charged photoconductive photosensitive drum with a laser beam. It is equipped with an optical system that corrects lens and polarizing mirror surface tilt.

The polarizing mirror surface tilt correction optical system compensates for the decrease in resolution of recorded images due to poor deflection scanning accuracy due to the deflection mirror, and scans the surface of the photoconductive photosensitive drum with the laser beam reflected by the deflection mirror via an Fθ lens. An exposure system for exposure can be placed between an Fθ lens and a photoconductive photosensitive drum.

A cylindrical lens is often used as this optical system for correcting surface tilt, and since a cylindrical lens with a short focal length has a large correction effect, 7. Cylindrical lenses with a short focal length are photoconductive It is arranged close to the surface of the drum.

On the other hand, an electrostatic latent image is formed on the surface of a photoconductive photosensitive drum, which is a component of an electrostatic recording mechanism, by scanning exposure of the exposure system, and this electrostatic latent image is developed with fine powder toner.

In general, dry developers for electrostatic latent images include one-component developers and two-component developers, and development methods include a cascade method and a magnetic brush method.

However, no matter which development method is used, it is impossible to avoid scattering of the fine powder toner, which is a component of the developer, into the air, and therefore, it is impossible to avoid scattering of the fine powder toner, which is a component of the developer, into the air. However, there is a problem in that fine powder toner adheres and stains the toner, reducing the laser beam transmission efficiency.

In particular, when a semiconductor laser beam generator (laser diode) is used, it is not possible to obtain a large laser beam output, so attenuation of the laser beam due to contamination of the cylindrical lens may cause insufficient exposure of the photoconductive drum surface. This may lead to a decrease in the quality of recorded images.

To solve this problem, the cylindrical lens can be cleaned frequently, but there is a risk of scratching the cylindrical lens during cleaning. can be,
In addition, it is necessary to take measures to prevent positional displacement due to attachment and detachment.

Even if the lens falls down, the maintenance period for this part should be very long, and measures should be taken to reduce the frequency of maintenance as much as possible, and measures should be taken to prevent the lens from becoming dirty. This applies to Fθ lenses and the like in exposure optical mechanisms that do not have a surface tilt correction optical system.

[Purpose of the invention]

In view of the above, the present invention prevents the surface tilt correction optical system in the exposure optical mechanism or the Fθ lens from being contaminated by fine powder toner, thereby obtaining high-quality recorded images over a long period of time, and even if the contamination progresses. Another object of the present invention is to provide a light beam printer that is easy to maintain.

[Summary of the invention]

The structure of the light beam printer according to the present invention is such that an electrostatic latent image formed by selectively discharging charges on the uniformly charged surface of a photoconductive photoreceptor is developed with fine powder toner. An exposure device having an electrostatic recording mechanism and a light beam optical path that is isolated from the electrostatic recording mechanism and scans and exposes the surface of the photoconductive photoreceptor by deflecting a light beam from a light source to selectively release charges. a plurality of partition walls having slits forming a light beam optical path at a light beam exit portion of the exposure optical mechanism;
A dust removal box with a dust settling space formed between the partition walls is provided, and a deflection mirror surface tilt correction optical system is attached to this dust removal box to form a single unit, and this unit can be detachably attached. It is composed of

In addition, the following is added.

In order to achieve the above object, the present invention includes a plurality of partition walls having slits that form an optical path of the light beam at a light beam exit portion of an exposure optical mechanism, and dust particles formed between the partition walls. A dust removal box equipped with a settling space is provided, and by weakening the velocity of the airflow passing through the slit in the dust settling space, fine toner particles floating in the air are settled and removed, and the fine toner particles are used to correct surface tilt in the exposure optical mechanism. In addition to being configured so that it does not adhere to the optical system, the surface tilt correction optical system and the dust removal box are installed together to form an integrated unit, and this unit is configured to be detachable. The system is characterized in that even if the system becomes contaminated, it can be easily maintained.

[Embodiments of the invention]

An embodiment of a light beam printer according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a schematic configuration of a laser beam printer used in an embodiment of the present invention, FIG. 2 is an explanatory diagram of its surface tilt correction function, and FIG. 3 is a laser beam printer according to an embodiment of the present invention. FIG. 4 is an enlarged vertical cross-sectional view of the exposure optical mechanism of the beam printer; FIG. 4 is an enlarged detailed vertical cross-sectional view of the dust removal box; FIG.
The figure is an enlarged cross-sectional view of the dust removal box showing its related parts.

First, in Fig. 1, 1 is a laser diode, 2 is a laser drive circuit, 3 is a collimator lens, 4 is a beam shaper, 5 is a rotating polygon mirror, 6 is an Fθ lens, 7 is a photosensitive drum, and 8 is a cylindrical lens. , 9 is a charger, 10
1 is a developing device, 11 is an electrostatic transfer device, 12 is a recording paper, 13 is a reflecting mirror, 14 is a photodetector, 15 is a synchronizing signal generation circuit, 16 is a print signal control circuit, and 17 is a rotating polygon mirror. This is a control circuit for the drive motor.

Therefore, the photosensitive drum 7, charger 9. Developing device 10
and the electrostatic transfer device 11 etc. constitute an electrostatic recording mechanism,
Also, laser diode 1. Collimator lens 3. The beam shaper 49-times transition mirror 5, the Fθ lens 6, the cylindrical lens 8, and the like constitute an exposure optical mechanism.

That is, the laser diode 1 generates a laser beam controlled by pulse modulation by the laser drive circuit 2.

The laser beam generated from this laser diode 1 is made into a parallel beam by a collimator lens 3,
The beam shaper 4 shapes the beam into a predetermined cross-sectional shape.

The shaped laser beam is deflected and scanned by a rotating polygon mirror 5, focused by an Fθ lens 6, and focused on the irradiated surface of a photoconductive photosensitive drum 7 to form a minute beam spot.

A cylindrical lens 8 is still installed between the Fθ lens 6 and the photosensitive drum 70 for the purpose of correcting the surface tilt of the rotating polygon mirror 5.
is placed.

In an electrophotographic laser beam printer, a charger 9, which is necessary for the electrophotographic process, is installed around the photosensitive drum 7. Developing device 10. An electrostatic transfer device 11 and the like are arranged.

That is, the surface of the photosensitive drum 7, which is rotated in the direction of the arrow by a drive source (not shown), is uniformly charged by the charger 9, and then scanned and exposed with a laser beam by the exposure optical mechanism related to the above-mentioned scanning exposure optical system. to form an electrostatic latent image.

The developing device 10 uses a magnetic brush adsorbed to a magnetic roll to apply a one-component developer made of magnetic fine powder toner or a two-component developer mixed with a magnetic carrier and fine powder toner to the photoconductive photosensitive drum 7. The electrostatic latent image is developed by rubbing and a toner image is formed.

On the other hand, recording paper 1 is transported by a paper feeding mechanism (not shown).
2 comes into contact with the photosensitive drum 7 , and the toner image on the surface of the photosensitive drum 7 is transferred by the electrostatic transfer device 11 .

Through the above process, the laser beam printer can record predetermined information on the recording paper 12.

Furthermore, a reflector 13 for synchronizing the modulation signal is used to control these functions. Photodetector 14. Synchronous signal generation circuit 15. A print signal control circuit 162, a rotation mirror drive motor control circuit 17, and the like are provided.

In the above, since the laser beam has good focusing properties, it is possible to form a minute beam spot, and therefore high-resolution image recording can be expected.

However, to achieve this, the laser beam must be deflected and scanned accurately.

The rotating polygon mirror 5 that deflects and scans the laser beam deflects and scans the laser beam on each reflective surface while rotating at a constant speed, but the normal line of each reflective surface and the angle of the rotation axis are not constant, which is what is called a tilted surface. Then, the scanning position of the beam spot shifts in the direction of rotation of the photosensitive drum 70, causing scanning line pitch unevenness.

In order to prevent the occurrence of this scanning line pitch unevenness, the rotating polygon mirror 5 must be processed with high precision.

For example, if the distance between the rotating polygon mirror 5 and the irradiated surface of the photosensitive drum 7 is 50'Oyam, and the permissible scanning line pitch unevenness on the irradiated surface is ±0.01 mm, then the surface tilt of the rotating polygon mirror 5 is allowed. The angle will look like this:

However, this allowable angle is close to the limit of the accuracy of rotating polygon mirror processing, and the resulting rotating polygon mirror 5 is extremely expensive.

The above-mentioned cylindrical lens 8 optically corrects the deviation in the deflection and scanning position of the laser beam due to the surface tilt of the rotating polygon mirror 5, and its surface tilt correction function will be explained in detail with reference to FIG. do.

In FIG. 2, the deflection scanning position shift amount corresponding to the surface tilt angle ψa/2 of the rotating polygon mirror 5 is
Letting δ be the case where the lens is not used, and δC be the case where the cylindrical lens 8 is used, the following relationship will be obtained.

However, fθ: focal length of the Fθ lens 6.

f: Focal length of the cylindrical lens 8.

Therefore, the surface inclination correction effect becomes larger as the focal length f of the cylindrical lens 8 is shorter than the focal length fθ of the Fθ lens 6.

From the above results, the cylindrical lens 8 for surface tilt correction is arranged near the surface of the photosensitive drum 70.

On the other hand, in consideration of the dark decay characteristic of the surface potential of the photoconductive photoreceptor, it is desirable that the developing device 10 be placed as close to the exposure optical system as possible to shorten the process time from exposure to development.

Therefore, as mentioned above, preventing the cylindrical lens 8 from being contaminated by floating fine powder toner generated during the development process is an essential issue for laser beam printers that have a surface tilt correction optical system, and countermeasures are desired. Become.

Next, a laser beam printer according to an embodiment of the present invention will be explained with reference to FIGS. 3 to 6.

The structure according to this embodiment is the same as that shown in FIG. 1 except for the structure of the scanning exposure optical mechanism shown in FIG. 3.

That is, in FIG. 3, the scanning exposure optical mechanism 18 related to the exposure optical mechanism is installed and housed in an optical box 19 to be protected from external dust, and the scanning beam is transmitted through the rotating polygon mirror 5A and the Fθ lens. 6A, reflective mirrors 20 and 21. Photosensitive drum 7 via cylindrical lens 8A
The surface of A is scanned and exposed.

A slit-shaped opening 19b is formed in the laser beam exit portion 19a of the optical box 19 to guide the laser beam, and the optical box 19 is a dust removal box that is detachable as a unit including the cylindrical lens 8A. 22 to form a closed space.

Hereinafter, the structure of the dust removal box 22 will be explained in detail using FIG. 4.

FIG. 4 is an enlarged detailed longitudinal sectional view of the dust removal box 22.

In the figure, the holder 23 is made of a conductive member manufactured by extrusion molding on an aluminum machine, etc., and is detachably attached to the optical box 19, and is electrically grounded via the optical box 19 at the time of attachment. shall be carried out.

A recess 23a for supporting the cylindrical lens 8A and a slit-shaped opening 23b for guiding the laser beam emitted from the cylindrical lens 8A are formed on the optical box 19 side of the holder 23.

Further, on the photosensitive drum 7A side of the holder 23, four parts 23C are formed to sandwich a plurality of dustproof slit plates 24a to 24C.

Furthermore, when the holder 23 is an extrusion molded product, both ends are open, so side walls 25 are used to close the openings.
are provided and fixed using screws 26.

The dust-proof slit plates 242 to 24C have openings 24a-1 to 24 corresponding to slits for guiding laser beams.
C-1 is provided.

The cylindrical lens 8A is a boulder 230 concave portion 23
a with a fitting gap of the required precision, and then fixed with a lens holder 28 via a cushion 27.

The lens holder 28 is made of an elastic member such as a plate spring material, and has a slit-shaped opening 28a that serves as an opening for guiding the laser beam.

Still, the lens holder 28 uses its elasticity to fix the cylindrical lens 8A via the cushion 27, and also forms a closed space in contact with the plane of the laser beam exit portion 19a of the optical box 19.

The dust removal box 22 having the above-mentioned structure has the structure of the photosensitive drum 7A.
The openings of the dust-proof slit plates 242 to 24C are formed on the surface side of the dust-proof slit plates 242 to 24C, and a relatively large volume of dust settling space is provided between each slit plate, resulting in a so-called labyrinth-like structure.

Therefore, in order for the fine powder toner generated from the developing device 10 and floating near the surface of the photosensitive drum 7A to adhere to the surface of the cylindrical lens, the openings of the dustproof slit plates 248 to 24C of the dust removal box 22 must be opened. Parts 24a-1 to 24C
-1 must be passed sequentially.

However, since the internal space of the dust removal box 22 provided between the slits is larger than the openings 24a-1 to 24C-1 of the dust-proof slit plates 248 to 24C, the airflow speed inside the box is extremely weakened. Then, the floating fine toner particles settle due to their own weight.

In addition, the settling space is divided into multiple stages by multiple slits, so the fine powder toner that flows in through the narrow openings is
It diffuses and becomes diluted in a wide sedimentation space.

Therefore, in the example shown in FIG. 4, the amount of fine powder toner that reaches the surface of the cylindrical lens 8A through the three-stage diffusion process is extremely small.

Further, since the dust removal box 22 is conductive and is grounded via the optical box 19, even if charged fine powder toner adheres electrostatically, the attached toner releases its charge and has an adhesive force. is lost and falls to the bottom and accumulates.

As a result, the dust removal box 22 in this embodiment prevents the cylindrical lens 8A from becoming dirty and can be used for a long period of time.

However, the removal of toner accumulated inside the dust removal box 22 or the cleaning of the cylindrical lens 8A are necessary maintenance items, although they are performed at extremely long intervals.

Therefore, another function of the dust removal box 22 is that it is easy to maintain.

In this embodiment, in consideration of this point, the dust removal box 22 and the cylindrical lens 8A are made into an integrated unit, and this unit is made detachable from the optical box 19.

This point will be explained in detail below using FIGS. 5 and 6, including FIG. 4.

In FIG. 5, which is an external view of the dust removal box 22, the lens holder 28 is fixed to the left and right side walls 25a and 25b with screws 29.

Furthermore, engagement pins 30 are fixedly provided on the left and right side walls 25a and 25b, respectively.

As shown in FIG.
and the guide groove 23d of the holder 23, and the engaging pin 3 is inserted in the position shown in FIG. 6, which is a cross-sectional view.
o and the engagement hole 19C of the optical box 19 that engages with this
It is set in the correct position in a fitting relationship with the optical box 19, and then fixed to the optical box 19 with the fixing screw 32.

In the above-described configuration, the procedure for maintaining the dust removal box 22 is to first remove the fixing screw 32, remove the dust removal box 22 from the main body of the laser beam printer, and move it to a place where it is easy to work, such as on a desk. When the screw 29 is removed and the lens boulder 28 is removed, the cylindrical lens 8A can be removed.

Next, by removing the left side wall 25a, the internal dustproof slit plates 24a to 24C are pulled out, and the accumulated fine powder toner is removed.

After disassembling according to the above steps, maintenance is completed by assembling the cleaned parts in the reverse order.

As described above, according to this embodiment, the light beam exit portion of the exposure optical mechanism has a plurality of partition walls having slits that form the optical path of the light beam, and the dust particles formed between the partition walls. By providing a dust removal box equipped with a settling space, the velocity of the air flow in the dust settling space is weakened, and fine toner particles and other dust floating in the air are settled and removed.
Therefore, it is possible to provide a light beam printer that can prevent the exposure optical mechanism from becoming dirty and obtain high-quality recorded images over a long period of time.

In addition, by integrating the dust removal box and the surface tilt correction optical system such as a cylindrical lens into a unit and configuring it to be detachable from the optical box, maintenance work can be performed even if the exposure optical mechanism becomes dirty. This can be done easily.

In other words, since the photoconductive photoreceptor and the light beam exit portion of the exposure optical mechanism of a light beam printer are located in the center of the device, it is difficult to see the center of the device when the tilt correction optical system is fixed. It is difficult to perform cleaning work at the same location, which is not only difficult to do, but also makes it extremely difficult to check the results.

According to this embodiment, these can be taken out of the apparatus as a unit and moved to a location with good workability at will, so workability is good and the results can be clearly confirmed.

Furthermore, although optical system components normally require high mounting position accuracy, this example uses high-precision retaining pins for positioning, which improves the reproducibility of mounting and dismounting. It is possible to secure it.

In addition to the above, by narrowing the aperture width of the slit in the dust-proof slit plate sequentially from the cylindrical lens to the photosensitive drum as shown in Figure 4, beam vignetting due to scanning errors can be effectively prevented, allowing for an acceptable assembly. The margin for adjustment error can be increased.

That is, according to this method, the opening width of the slit is narrowest at the drum surface, that is, the area where the concentration of floating toner is high;
Since the density of the toner that has passed through the first slit is extremely reduced due to diffusion, the increase in the amount of contamination due to the sequentially widening of the second and third slits becomes almost negligible. Therefore, it can be said to be the most effective means.

However, in the above embodiment, the dust removal box is made of a conductive material, but this is not suitable for cases where the charged floating toner is negligible, that is, when the path is long and the dust removal box falls and accumulates due to its own weight. In such cases, it can be made non-conductive.

However, if the usage environment is good and the frequency of maintenance is short, or if the assembly and adjustment are performed with high precision and there is little deviation of the optical axis, the opening width of the slit in the dust-proof slit plate described above may be set to the same value. There is no practical problem even if the width is formed.

Furthermore, although the above embodiments relate to laser beam printers, the present invention is a general-purpose printer that can use not only laser light but also other light sources.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the surface tilt correction optical system in the exposure optical mechanism or the Fθ lens from being contaminated by fine powder toner, thereby obtaining high-quality recorded images over a long period of time, and even if the staining progresses, It is possible to provide a light beam printer that is easy to maintain, and it can be said that the invention has excellent practical effects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a schematic configuration of a laser beam printer used in an embodiment of the present invention, FIG. 2 is an explanatory diagram of its surface tilt correction function, and FIG. 3 is a laser beam printer according to an embodiment of the present invention. FIG. 4 is an enlarged detailed sectional view of the exposure optical mechanism of the beam printer; FIG. 5 is an enlarged detailed sectional view of the dust removal box; FIG. 5 is a plan view and side views of the dust removal box; FIG. 2 is an enlarged cross-sectional view of the dust removal box showing the relevant parts thereof. DESCRIPTION OF SYMBOLS 1...Laser diode, 2...Laser drive circuit, 3...Collimator lens, 4...Beam shaper, 5A...Rotating polygon mirror, 6A...Fθ lens, 7
A... Photosensitive drum, 8A... Cylindrical lens, 9... Charger, 10... Developer, 11... Electrostatic transfer device, 12... Recording paper, 13... Reflector , 14・
...Photodetector, 15...Synchronization signal generation circuit, 16...
・Print signal control circuit, 17... Rotating polygon mirror drive upper control circuit, 18... Scanning exposure optical mechanism, 19...
Optical box, 19a...laser beam exit part,
19b...Slit opening, 19C...Engagement hole, 2
0.21...Reflection mirror, 22...Dust removal box, 2
3... Holder, 23a... Concave portion, 23b... Slit-shaped opening, 23C... Slit holding concave portion, 2
3d...Guide groove, 24a. 24 b, 24 C--dust-proof slit plate, 24a
-1゜24b-1, 24C-1...Opening of dustproof slit plate, 25...Side wall, 25a...Left side wall, 25b
...Right side wall, 26.29...Screw, 27...Cushion, 28...Lens holder, 28a...Srin +- shaped opening part, 30...Engagement pin, 31...・Guide plate, 32...Fixing screw. Agent: Patent attorney Kosaku Fukuda (and one other person)

Claims (1)

[Scope of Claims] (2) An electrostatic recording mechanism in which an electrostatic latent image formed by selectively discharging charges on the uniformly charged surface of a photoconductive photoreceptor is developed with fine powder toner. and an exposure optical mechanism that is isolated from the electrostatic recording mechanism and has a light beam optical path that deflects a light beam from a light source to scan and expose the surface of the photoconductive photoreceptor and selectively discharges charges. In the light beam printer, the light beam exit portion of the exposure optical mechanism is provided with a plurality of partition walls having slits forming a light beam optical path, and a dust settling space formed between the partition walls. 7. A light beam printer characterized in that a dust removal box is provided, and an optical system for correcting deflection mirror surface tilt is attached to the dust removal box to form a single unit, and the unit is configured to be detachable. 2. A light beam printer according to claim 1, wherein the dust removal box is grounded and conductive or non-conductive.