JP2802853B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus of a backside light exposure system, and more particularly to the prevention of a decrease in focusing performance due to a deviation of a substrate of a photosensitive film from a perfect circle.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Sho 58-44445 shows the basic principle of an optical backside exposure system. In this method, a photosensitive film such as a-Si is provided on the outer peripheral surface of a transparent cylindrical substrate such as glass, and an exposure head such as an LED print head is accommodated inside the substrate. The optical backside exposure method has attracted attention because it has the effects of reducing the size and cost of an image forming apparatus, improving safety by charging at a low pressure, and preventing ozone generation.

However, the substrate made of glass or the like used for the photoreceptor has a low roundness, and its inner and outer peripheral surfaces are deformed by about ± 200 μm from the shape determined based on the perfect circle. Such a decrease in roundness causes a variation in the distance between the exposure head and the photosensitive film on the outer peripheral surface of the substrate. For example, in the case of an exposure head using a self-focusing array, ± 2
The disturbance of the distance of 00 μm changes the width of the exposure beam from the exposure head by about 15 to 20%. When the beam diameter changes, the dot diameter of the latent image changes, the printing line width changes, and the printing quality such as density unevenness deteriorates.

In order to keep the distance between the exposure head and the photosensitive member constant, it is conceivable to arrange a small bearing such as a space roller between the inner peripheral surface of the base of the photosensitive member and the exposure head. However, in this method, a large pressure is applied from the space roller to the inside of the substrate, and there is a possibility that the substrate such as fragile glass may be broken. The pressure applied to the substrate from the space rollers increases as the rotation speed of the photoconductor increases. In order to perform high-speed printing, the rotation speed of the photoconductor is increasing, and there are many problems in positioning using space rollers.

Japanese Patent Application Laid-Open No. 2-141774 discloses a related art in which two fixed rollers and one movable roller are provided inside a base, and the base is positioned by these rollers. It has been proposed to bring the photoconductor into contact with the developing roller. However, this publication does not disclose the positioning of the exposure head with respect to the substrate of the photoconductor.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to prevent a decrease in printing quality due to a decrease in roundness of a substrate by keeping a distance between an exposure head and a photoreceptor film in an optical back exposure method. is there. A secondary object of the present invention is to position the substrate and the exposure head without applying abnormal pressure to the substrate and without destroying the substrate.

[0007]

An image forming apparatus according to the present invention is an image forming apparatus comprising: a photosensitive cylindrical film provided on an outer peripheral surface of a transparent cylindrical base; an exposure head accommodated inside the base; and a developing device provided outside the base. In the forming apparatus, while mounting flanges with bearings at both ends of the base,
A spring member is provided between the flange and the inner peripheral surface of the base for holding the exposure head by the flange and pressing the outer peripheral surface of the flange against the inner peripheral surface of the base. It is characterized by.

Here, as the exposure head, for example, a liquid crystal shutter array head, a PLZT optical shutter head, an EL head, etc. may be used in addition to the LED head shown in the embodiment. As the spring member, a spring flange shown in FIG. 2, a viscous fluid shown in FIG. 1, or a fluid of magnetic powder shown in FIG. 3 may be used. Any structure may be used as long as the surface and the inner peripheral surface of the substrate are pressurized and pressure is applied so that the flange and the substrate are brought into close contact with each other on the developing device side.

[0009]

According to the present invention, the exposure head is supported by the flange, and the exposure head is positioned by the flange. Next, a spring member is provided between the outer peripheral surface of the flange and the inner peripheral surface of the photoreceptor base, and the distance between the exposure head and the photoreceptor film on the developing device side is increased by applying pressure by the spring member. Keep it constant. As a result, it is possible to prevent a decrease in printing quality due to a decrease in the roundness of the base. Since the pressurization by the spring member is performed almost uniformly over a wide range, local concentration of stress on the substrate can be prevented, and destruction of the substrate can be prevented.

Preferably, the spring member is a fluid spring such as air, water, glycerin, or a magnetic fluid, as shown in FIGS. With this configuration, the flange and the inner peripheral surface of the base can be sealed by the spring member, and the intrusion of toner powder or paper powder generated inside the image forming apparatus can be prevented, and the deterioration of printing quality can be prevented. be able to.

Here, most preferably, a magnetic fluid is used for the spring member, and the magnetic fluid is sealed between the inner peripheral surface of the base and the outer peripheral surface of the flange by, for example, a permanent magnet provided on the outer peripheral surface of the flange. In this way, the magnetic fluid can be sealed between the flange and the inner peripheral surface of the base without a bag required for a fluid such as water, and the exposure head and the photoconductor film due to a change in the width of the bag. Does not occur, and problems such as durability of the bag do not occur. Further, similarly to the case of sealing with another fluid, the gap between the outer peripheral surface of the flange and the inner peripheral surface of the base can be sealed with a magnetic fluid, so that intrusion of paper dust and toner can be prevented.

[0012]

FIG. 1 shows an embodiment. In the drawing, reference numeral 2 denotes a cylindrical transparent substrate such as glass, and a photoreceptor film such as a-Si (not shown) is provided on the outer peripheral surface thereof. Reference numeral 4 denotes a developing roller of a developing device, 6 denotes toner, and 8 and 9 denote rollers for positioning the base 2. It is preferable that at least one of the positioning rollers 8 and 9 is a movable roller. Numeral 10 is a flange provided at both ends of the opening of the base 2 and having a high roundness. 12 is a bearing part of the flange 10, and 14 is its ball. Reference numeral 16 denotes a shaft fixed to the center of the flange 10 for fixing the LED head 18. Reference numeral 20 denotes a self-focusing lens array of the LED head 18.

Reference numeral 22 denotes a viscous fluid such as polyethylene glycol, glycerin, castor oil, water, and cutting oil. 2
Reference numerals 4 and 24 are synthetic resin films used as bags for containing the viscous fluid 22.

The operation of the embodiment will be described. A bag containing the viscous fluid 22 is fitted to the outer peripheral surface of the flange 10 and fitted to the inner peripheral surface of the base 2. The flanges 10 are respectively fitted to openings at both ends of the base 2, and support the exposure head 18 by the shaft 16. As a result, the exposure head 18
Are positioned with respect to the flange 10 via the shaft 16.

Next, when this is assembled as shown in FIG. 1, the base 2 is pressed leftward in the figure from the side of the developing roller 4 by the positioning rollers 8, 9, so that the viscous fluid 22 is, for example, as shown in FIG. It escapes to a portion on the opposite side of the developing roller 4 or the like. When the substrate 2 has undulation (out of a true circle), the viscous fluid 22 concentrates on the portion, and presses the substrate 2 and the flange 10 from there, as shown in FIG. 1, for example. As a result, on the side of the developing roller 4, the flange 10 comes into close contact with the base 2 with the two films 24, 24 interposed therebetween. As a result, the distance between the exposure head 18 and the substrate 2 becomes constant irrespective of the roundness of the substrate 2, and the error of about ± 200 μm of the prior art is reduced by ± 10.
It can be 0 μm or less. Since the flange 10 is in close contact with the base 2 through the two films 24, 24, even if the roundness of the base 2 is low, the base 2 can be prevented from being broken due to local contact.

Next, the gap between the base 2 and the flange 10 is sealed by a bag containing the viscous fluid 22. For this reason, even if the toner 6 and the paper dust are scattered, there is no possibility that the toner 6 or the paper dust enters the inside of the base 2 to lower the printing quality.

Here, the positioning rollers 8 and 9 are arranged on the outer peripheral surface of the base 2 on the side of the developing roller 4, but on the contrary, they are disposed on the inner peripheral surface of the base 2 and on the opposite side of the developing roller 4. Is also good. In this case, the flange 10 may be disposed slightly behind the surface of the opening of the base 2, and the positioning rollers 8 and 9 may be disposed between the flange 10 and the opening of the base 2.

Next, in the embodiment, the viscous fluid 2 is used as the sealing fluid.
2 is used to rotate the outer peripheral portion of the flange 10 together with the base 2. The outer peripheral portion of the flange 10 is
When rotated together, the pressure on the base 2 due to the relative rotation between the flange 10 and the base 2 can be reduced. Although the outer peripheral portion of the flange 10 rotates together with the base 2, the portion where the viscous fluid 22 is concentrated due to the undulation of the base 2 always appears in a place other than the portion facing the developing roller 4. An extremely low-viscosity fluid such as water or air can be used instead of the viscous fluid 22, but in this case, the outer peripheral portion of the flange 10 may rotate relative to the base 2.

[0019]

Embodiment 2 FIG. 2 shows a second embodiment. In the figure,
Numeral 30 denotes an elastic belt made of rubber or the like, which is arranged along the inner peripheral portion of the base 2 so that the flange 10 is deflected on the waviness side of the base 2 on the left side in the figure. In other respects,
This embodiment is similar to the embodiment of FIG.

The position of the base 2 on the side of the developing roller 4 is regulated by positioning rollers 8 and 9. As a result, the spring belt 30 bends as shown in FIG.
Is pressed, the flange 10 is pressed against the base 2 by the elastic roller 4 side, and the distance between the exposure head 18 and the photosensitive film can be made constant. On the side of the developing roller 4, the outer peripheral surface of the flange 10 is in close contact with the base 2 via the belt 30, so that destruction of the base 2 due to local contact between the two can be prevented.

Compared with the embodiment of FIG. 1, the embodiment of FIG. 2 uses the belt 30 as the spring member,
The space between the flange 10 and the base 2 cannot be sealed. For this reason, in the embodiment of FIG. 2, it is preferable to separately provide a member for sealing the gap between the flange 10 and the base 2.

[0022]

Embodiment 3 FIGS. 3 and 4 show a third embodiment. In FIG. 3, reference numeral 32 denotes a magnetic fluid such as iron powder, which is sealed between the base 2 and a permanent magnet 34 arranged in a ring shape along the outer peripheral surface of the flange 10 as shown in FIG. Therefore, the difference between the embodiment of FIGS. 3 and 4 and the embodiment of FIG. 1 is that the film 24 for containing the fluid is not required. In other respects, the embodiment of FIGS. 3 and 4 is similar to the embodiment of FIG.

The features of the embodiment shown in FIGS. 3 and 4 are shown. The magnetic fluid 32 is formed by dispersing magnetic powder such as iron powder in lubricating oil, and is sealed in a gap with the base 2 by a permanent magnet 34. The particle size of the magnetic powder is about 0.01 to 1 μm.
When the base 2 is pressed from the developing roller 4 side by the positioning rollers 8 and 9, the magnetic fluid 32 escapes as shown in FIG. 3, for example, and the flange 10 is pressed from the left side in FIG. As a result, the distance between the exposure head 18 and the photosensitive film on the substrate 2 is kept constant. Since the magnetic fluid 32 is held by the permanent magnet 34, the films 24, 24 shown in FIG. 1 become unnecessary, and there is no need to consider the durability and the change in the distance between the exposure head 18 and the photosensitive member film due to expansion and contraction. Further, since the magnetic fluid 32 is sealed between the inner peripheral surface of the base 2 and the flange 10 by the permanent magnet 34, the same seal as in the embodiment of FIG. 1 can be achieved.

[0024]

According to the present invention, the exposure head can be easily and accurately positioned with respect to the substrate without damaging the fragile substrate such as glass. As a result, the distance between the exposure head and the photoconductor film can be kept constant, and the image quality can be improved. Further, when a fluid is used as the spring member, the gap between the base and the flange can be sealed to prevent the intrusion of toner, paper dust, and the like.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of an image forming apparatus according to an embodiment.

FIG. 2 is a side view of a main part of an image forming apparatus according to a second embodiment.

FIG. 3 is a side view of a main part of an image forming apparatus according to a third embodiment.

FIG. 4 is a sectional view of a main part of a third embodiment.

[Explanation of symbols]

 2 Base 4 Developing roller 6 Toner 8,9 Positioning roller 10 Flange 12 Bearing 14 Ball 16 Shaft 18 LED head 20 Self-focusing lens array 22 Viscous fluid 24 Film 30 Spring belt 32 Magnetic fluid 34 Permanent magnet

Claims (1)

(57) [Claims] 1. An image forming apparatus comprising: a photosensitive cylindrical film provided on an outer peripheral surface of a transparent cylindrical base; an exposure head housed inside the base; and a developing device provided outside the base; A flange with a bearing is attached to each of the openings, the exposure head is held by the flange, and an outer peripheral surface of the flange is provided between the flange and an inner peripheral surface of the base. An image forming apparatus, comprising a spring member for applying pressure to the image forming apparatus.