JPS6093468A - Laser beam printer - Google Patents

Abstract

PURPOSE:To prevent dirt by providing plural partitioning walls, which have slits forming an optical path of a laser beam, and a dust removing box in the laser beam exit part of an exposure optical mechanism to precipitate and remove a fine powdery toner or the other dusts floating in air. CONSTITUTION:A dust removing box 22 has what is called a labyrinth structure where aperture parts 24a of dustproof plates 24 are provided in the surface side of a photosensitive drum 17 and a dust sedimentation space having a relatively large capacity is provided between dustproof plates. Consequently, the fine powdery toner floating near the surface of the photosensitive drum 7 must pass through aperture parts 24a of dustproof plates 24 of the dust removing box 22 successively when it is stuck to the surfaces of a reflective mirror 13 and a cylindrical lens 8. However, since the internal space between dustproof plates 24 is larger than sperture parts 24a, the velocity of the air current in the box is reduced exremely, and the floating fine powdery toner is precipitated by its own weight. The sedimentation space is partitioned to many stages by plural dustproof plates 24, and therefore, the fine powdery toner flowed from narrow aperture parts 24a is dispersed in the wide sedimentation space and is thinned.

Description

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

[Background of the invention]

A laser beam printer uses a deflection mirror 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 F-theta lens, a deflection mirror surface tilt correction optical system, a beam detection device, etc. The beam detection device scans and detects when the laser beam reaches the reference position and controls the writing start position at a constant level.A reflecting mirror is installed in a part of the laser beam optical path to bend the optical path. It is configured to guide the laser and a portion to the light receiving element.

Since the deflection mirror has variations in its inclination with respect to the support axis, in order to correct this, surface inclination correction is performed. A cylindrical lens with a short focal length is often used as the surface tilt correction optical system, and is disposed close to the surface of the photoconductive photosensitive drum. The beam detection device is also affected by the tilting of the deflecting mirror, which reduces the detection accuracy fc. Therefore, the reflecting mirror is installed behind the cylindrical lens, that is, between the cylindrical lens and the photoconductive photosensitive drum, so that the deflecting mirror does not have to be taken care of. We are making sure that there is no influence from this. On the other hand, an electrostatic latent image is formed on the surface of the photoconductive photosensitive drum, which is a component of the electrostatic recording mechanism, by the scanning exposure of the exposure system,
Kono Shizuka 1! The latent image is developed with fine powder toner. In general, dry developers for electrostatic latent images include l-component developers and two-component developers, and development methods include cascade methods and magnetic brush methods. No matter which development method is used, it is impossible to avoid the scattering of fine powder toner, which is a component of the developer, into the air. Toner adheres and stains it, reducing the accuracy of laser beam detection, and in the worst case, the beam cannot be detected, ie, printing becomes impossible. To solve this problem, the reflector and cylindrical lens can be cleaned frequently, but there is a risk that the reflector or cylindrical lens may be damaged during cleaning, or the accuracy of the installation may be disrupted. Further, even when these are configured to be detachable, it is necessary to take measures to ensure that they are easy to attach and detach and to prevent positional displacement due to attachment and detachment. In any case, the maintenance period for this part should be very long and the frequency should be reduced as much as possible, and measures should be taken to prevent the reflector and lens from becoming dirty and to make their cleaning easier.

[Purpose of the invention]

Therefore, an object of the present invention is to prevent the beam detection device and the surface tilt correction optical system in the exposure optical mechanism from being contaminated by fine powder toner, maintain the accuracy of beam detection over a long period of time, and obtain high-quality recorded images. An object of the present invention is to provide a laser beam printer that is easy to maintain even if it becomes contaminated.

[Summary of the invention]

To achieve this object, the present invention provides a laser beam exit portion of an exposure optical mechanism with a plurality of dustproof plates having slits that form the optical path of the laser beam, and a dust settling space formed between the dustproof plates. A dust removal box is provided, and by weakening the velocity of the airflow that has passed through the slit in a dust settling space, fine toner particles floating in the air are settled and removed, and the structure is configured to prevent fine toner particles from adhering to the beam detection optical system. The detection optical system can be installed in this dust removal box to form an integrated unit, and this unit can be attached to and detached from the laser beam exit port, making maintenance easy even if these optical systems become contaminated. It is characterized by something that has been made possible.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a perspective view showing a schematic configuration of a laser beam printer to which the present invention is applied.

In FIG. 1, a laser diode 1 generates a laser beam controlled by pulse modulation by a laser drive circuit 2. In FIG. A laser beam generated from a laser diode 1 is made into a parallel beam by a collimator lens 3, and shaped into a predetermined cross-sectional shape by a beam shaper 4. The shaped laser beam is deflected and scanned by a rotating polygon mirror 5, focused by an F-theta lens 6, and formed into an image on the irradiated surface of a photoconductive photosensitive drum 7 to form a minute beam spot. Further, a cylindrical lens 8 is arranged between the F-θ lens 6 and the photosensitive drum 70 for the purpose of correcting the tilt of the rotating polygon mirror 5. Further, in order to synchronize the pulse modulation signal of the laser Pete, a reflecting mirror 13 and a photodetector 14 are provided, and a synchronization signal generation circuit 15 generates a synchronization signal based on the signals from the photodetector 14, and a video signal is generated using the synchronization signal. A print signal generation circuit 16 is provided to generate a print signal. In an electrophotographic laser beam printer, a charger 9, which is necessary for the electrophotographic process, is installed around the photosensitive drum 7.
A developing device 10, a transfer device 11, etc. are arranged. That is, the surface of the photosensitive drum 7 rotated in the direction of the arrow by a drive source (not shown) is uniformly charged by the charger 9.
Next, the above-described scanning exposure optical system performs scanning exposure with a laser beam to form an electrostatic latent image. Current gI! The device 10 uses a magnetic brush that adsorbs one stage of developer made of magnetic fine powder toner or two stages of developer made of a mixture of magnetic carrier and fine powder toner on a magnetic roll, and rubs the photosensitive drum 7 to form an electrostatic latent image. is developed to form a toner image.

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 11Vc. Through the above process, the laser beam printer can record predetermined information on the recording paper 12. Incidentally, the speed is controlled to be constant by a five-rotating polygonal mirror control circuit 17.

FIG. 2 is a longitudinal sectional view of the optical system of the laser beam printer according to the present invention. In the drawing, scanning exposure optical mechanism 1
8 has a structure that is installed and stored in an optical box 19 and protected from external dust, and the scanning beam is a rotating polygon mirror 5,
The surface of the photosensitive drum 7 is scanned and exposed through the F-θ lens 6, the reflecting mirrors 20 and 21, and the cylindrical lens 8.

A slit-shaped opening 19b is formed in the laser beam exit portion 198 of the optical box 19 to guide the laser beam, and includes a cylindrical lens and a reflector that sends the laser beam to the photodetector. A removal box 22 is provided to form a closed space.

The structure of the dust removal box 22 will be described in detail below using FIG. 3, FIG. 1M4.

FIG. 3 is a detailed vertical sectional view of the dust removal box 22, and FIG. 4 is a horizontal sectional view thereof. In the figure, the holder 23 is made of a conductive member manufactured by extrusion molding of aluminum material, is detachably attached to the optical box 19, and is electrically grounded via the optical box 19 at the time of attachment. There is. The optical box 19 side of the holder 23 is provided with four parts 23a for supporting the cylindrical lens 8 and a slit-shaped opening 23b for guiding the laser beam emitted from the cylindrical lens 8.

In addition, a plurality of dustproof plates 2 are provided on the photosensitive drum 7 side of the holder 23.
A recessed portion 23C for holding 4 is provided.

The dustproof plate 24 has an opening 24a for guiding the laser beam.
There is. Furthermore, in order to close both ends of the holder 23, fixing screws 268 (26
b) is fixed. An adjustment shaft 33 is rotatably provided on one side wall, and a reflecting mirror 13 is fixed to the tip thereof. The laser beam hitting the reflecting mirror 13 is reflected and enters the photodetector 14, which generates a synchronization signal for printing.

An adjustment arm 34 is attached to the adjustment shaft 33. The angle of the reflecting mirror 13 is adjusted using an adjusting arm 34 so that the laser beam is accurately incident on the photodetector 14, and the reflecting mirror 13 is fixed with a fixing screw 35. Concave part 2 of 8-cylindrical lens holder 23
3a with a fitting gap of 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 leaf spring, and has an opening 28a for guiding the laser beam. In addition, by utilizing the elasticity of the lens holder 281, the cushion 2
The cylindrical lens 8 is fixed through the lens 7 and is in contact with the plane of the laser beam exit portion 19a of the optical box 19 to form a closed space.

The dust removal box 22 having the structure described above has the opening 24a of the dustproof plate 24 on the surface side of the photosensitive drum 70, and has a relatively large volume of dust settling space between each dustproof plate, so that it has a so-called labyrinth-like structure. Become. Therefore, fine powder toner generated from the developing device 10 and floating near the surface of the photosensitive drum 7 is transferred to the reflecting mirror 1.
3 and the surface of the cylindrical lens 8, it must pass through the opening 24a of the dustproof plate 24 of the dust removal box 22 in order. However, since the internal space between the dustproof plates 24 is large with respect to the opening 24a, the airflow velocity within the box is extremely weakened, and the floating fine powder toner settles due to its own weight. Furthermore, since the settling space is divided into multiple stages by a plurality of dustproof plates 24, the fine powder toner that flows in from the narrow opening 24a is diffused and diluted in the wide settling space. Therefore,
The reflecting mirror 13 undergoes a three-stage diffusion process as shown in this embodiment.
The amount of fine powder toner that reaches this point is extremely small. Furthermore, the dust removal box 22 is conductive and is grounded via the optical box 19, so even if charged fine powder toner adheres electrostatically, the attached toner releases its charge and strengthens its adhesion. It is lost and falls to the bottom and accumulates. As a result, the dust removal box 22 according to the present invention prevents the reflecting mirror 13 from becoming dirty and can be used for a long period of time. However, removing the toner accumulated inside the dust removal box 22 or cleaning the reflecting mirror 13 is a necessary maintenance item, although it is performed at extremely long intervals. Therefore, another function of the dust removal box 22 is ease of maintenance. In the present invention, the dust removal box 22 and the reflecting mirror 13 are designed in consideration of this point.
as an integrated unit, and this unit as optical box 1.
9, which can be attached and detached. This point will be explained in detail below using FIGS. 3 to 6.

5(a) to 5(d) are an external plan view, left side view, front view, and right side view of the dust removal box 22, and FIG. 6 is a cross-sectional view. In FIGS. 5 and 6, the lens holder 28 is fixed to the left and right side walls 25a, 25b with screws 29a, 29b. Furthermore, engagement pins 30a and 30b are fixed to the side walls 25a and 25b, respectively.

As shown in FIG. 3, the dust removal box 22 having the above structure is inserted with the guide plate 31 fixed to the optical box 19 engaged with the guide groove 23d of the holder 23.
At the position shown in FIG. 6, the locking pin Fob and the engaging hole 19C of the optical box 19 that engages with it are set in the correct position (the same applies to the locking pin 30a), and then the fixing screw 32 is fixed to the optical box 19.

Perform maintenance of the dust removal box in the above configuration9.
The procedure is to first remove the set screw 3-2, remove the dust removal box 22 from the laser beam printer body, move it to a desk or other place where it is easy to work, then remove the screw 29 and remove the lens boulder 28. Once removed, the cylindrical lens 8 can be removed. Next, the reflecting mirror 13 can be cleaned by removing the side wall 25a, and the internal dustproof plate 24 is pulled out to remove the accumulated fine powder toner. After disassembling according to the above steps, maintenance is completed by assembling the cleaned parts in the reverse order.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of partition walls having slits forming an optical path of the laser beam at the laser beam exit portion of the exposure optical mechanism, and a dust settling space formed between the partition walls are provided. By providing a dust removal box with a built-in dust removal box, 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, thus preventing the exposure optical mechanism from becoming contaminated. It is possible to provide a single laser beam printer that can accurately control the writing position over a long period of time and obtain high-quality recorded images.

Furthermore, by integrating the dust removal box and a light beam detection mechanism such as a reflector into a unit and configuring it to be detachable from the optical box, maintenance work can be easily accomplished even if the reflector is soiled. It is something. The photoconductive photoreceptor and the light beam exit part of the exposure optical mechanism of a laser beam printer are located in the center of the device, so if the light beam detection mechanism is fixed, cleaning should be done in a hard-to-see location in the center of the device. However, according to the present invention, these can be taken out of the device as a unit and placed in a place where workability is good. Since it can be moved at will, the work efficiency is good and the results can be clearly confirmed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic mechanism of a laser beam printer to which the present invention is applied, FIG. 2 is a vertical sectional view of the exposure optical mechanism of a laser beam printer to which the present invention is applied, and FIG.
The figure is a detailed cross-sectional view of the dust removal box, Figure 4 is a cross-sectional view of the vicinity of the reflector, Figures 5 (a) to (d) are external configuration diagrams of the dust removal box, and Figure 6 is its cross-sectional view. be. 1... Radey diode, 5... Rotating polygon mirror, 6
...F-θ lens, 7... Photosensitive drum, 13...
Reflector, 1chi... Photodetector, 19... Optical box, 19h... Laser beam exit section, 22... Dust removal box, 23...-Holder, 23d... Guide groove,
24...Dustproof plate, 25a, 25b...Side wall, 31.
··Guide plate. fJ30 Tomilfρj

Claims (1)

[Claims] 1. Electrostatic recording in which charges on the uniformly charged surface of a photoconductive photoreceptor are selectively released by laser beam exposure to form an electrostatic latent image, and this electrostatic latent image is developed with fine powder toner. and a laser beam optical path that is isolated from the electrostatic recording mechanism and performs the laser beam exposure for scanning and exposing the surface of the photoconductive photoreceptor by deflecting the laser beam from the light source and selectively emitting charges. a plurality of dustproof plates having slits forming an optical path of the laser beam at the laser beam exit portion of the exposure optical mechanism; and a plurality of dustproof plates formed between the dustproof plates. A laser beam printer characterized by a detachable unit including a dust removal phase having a dust settling space and an optical system for detecting a laser beam inside the dust removal box.