JP2001201923A - Electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device using a roller type electrifier in which there is no danger that toner may enter an electrifier and which enables an electrostatic charger to be arranged beneath a photoreceptor. SOLUTION: First, the roller type electrifier 13 is arranged not just beneath the developing position of a developing device 14, but beneath the photoreceptor 10. Secondly, the electrifier 13 is arranged beneath the photoreceptor while interrupting between the developing position and the charger by the photoreceptor 10. In the 1st and 2nd cases, it is more preferable to arrange the electrifier 13 so that it may not be positioned just beneath the position cleaned by the cleaning device 17. Thirdly, a shutter member for preventing foreign matter from intruding from the outside is installed in the electrifier 13. Forth, a roller cleaning member for cleaning the electrification roller 12 is installed in the electrifier 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction peripheral thereof. In particular, charging, writing, developing,
A toner image is sequentially formed on a photoreceptor by repeating transfer, cleaning, etc., and the toner image is sequentially transferred directly to a recording medium, or once transferred to an intermediate transfer body, and then re-transferred to a recording medium. The present invention relates to an electrophotographic image forming apparatus that performs recording on a recording medium.

[0002]

2. Description of the Related Art In such an electrophotographic image forming apparatus, as a charging device for uniformly charging the surface of a photoreceptor,
In recent years, the roller type using a charging roller attracts attention,
Has been put to practical use.

However, in this type of roller-type charging device, even if a small amount of toner enters, uneven charging occurs.
There was a problem that the image quality deteriorated.

That is, if a charging device having a charging roller 2 is disposed below a belt-shaped photoreceptor 1 as in a color laser printer shown in FIG. There is a possibility that the toner that is located immediately below the developing position a and falls from the developing position a enters the charging device, causing charging unevenness and deteriorating the image quality.

In FIG. 5, reference numeral 4 denotes a cleaning blade of a cleaning device for cleaning the surface of the photoreceptor 1, and reference numeral 5 denotes a belt-like shape for sequentially transferring images sequentially formed on the photoreceptor 1 to form a composite color image. Reference numeral 6 denotes a transfer roller of a transfer device for transferring the composite color image on the intermediate transfer member 5 to the recording medium 7.

For this reason, in an image forming apparatus using such a roller type charging device, a charging device is disposed above the photosensitive member 1 so that toner dropped from the developing device 3 and the cleaning device is charged. Had been prevented from getting inside.

[0007]

However, recently, there are advantages in that the occupied installation space can be reduced, the operability is good, and the pages can be stacked in the order of pages. There is a tendency that an image forming apparatus that discharges the image with the image surface facing upward (so-called face-down) is preferred.

In order to obtain such an image forming apparatus,
From a design standpoint, it is desirable to dispose a charging device below the photoconductor 1 as shown in FIG.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus using a roller-type charging device, in which the charging device can be disposed at a position below the photosensitive member without the risk of toner entering the charging device.

[0010]

According to the first aspect of the present invention, there is provided an electrophotographic image forming apparatus having a roller type charging device, wherein the charging device is disposed at a position below the photosensitive member so as to avoid a position immediately below the developing position. It is characterized by having done.

According to a second aspect of the present invention, in the electrophotographic image forming apparatus having a roller-type charging device, the charging device is disposed at a position below the photosensitive member by blocking the photosensitive member from the developing position. Features.

According to a third aspect of the present invention, in the electrophotographic image forming apparatus according to the first or second aspect, a charging device is disposed at a position below the photosensitive member so as to avoid a position immediately below the cleaning position. .

According to a fourth aspect of the present invention, there is provided an electrophotographic image forming apparatus having a roller type charging device, wherein a shutter member for preventing foreign matter from entering the charging device from outside is provided, and a shutter member is provided at a position below the photosensitive member. A charging device is provided.

According to a fifth aspect of the present invention, there is provided an electrophotographic image forming apparatus having a roller type charging device, wherein a roller cleaning member for cleaning a charging roller of the charging device is provided, and the charging device is disposed below the photosensitive member. It is characterized by the following.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a main part of a color laser printer according to the present invention.

In the figure, reference numeral 10 denotes a belt-shaped photosensitive member provided so as to extend over a plurality of rollers 11. A roller type charging device 13 having a charging roller 12 is disposed around the photoreceptor 10 at a lower position. A developing device 14 is provided on the right side, a belt-shaped intermediate transfer member 15 is provided on the left side, and a cleaning device 17 having a cleaning blade 16 is provided on the lower left side in the rotation direction of the photoconductor 10 from the charging device 13 in order.

The photosensitive member 10 is moved, for example, at a linear speed of 178.
After rotating counterclockwise at mm / sec, the surface of the photoreceptor 10 is uniformly charged by the charging device 13 with the rotation, and then laser light L is irradiated by an optical writing device (not shown) to write the first color. To form an electrostatic latent image on the surface of the photoconductor 10.

Thereafter, one of the color developing units 14BK, 14C, 14M, and 14Y provided in the developing device 14 in a plurality of stages is provided.
First, an image of the first color is formed on the photoconductor 10. Then, the image is transferred by a transfer device (not shown) with the rotation of the photoconductor 10, and the first color image is transferred onto the intermediate transfer body 15.

On the surface of the photoreceptor 10 after the image transfer, the residual toner is removed by a cleaning blade 16 of a cleaning device 17.
Remove and clean. Then, the charge is removed by a charge removing device (not shown).

Then, the photosensitive drum 10 is uniformly charged again by the charging device 13 and then irradiated with laser light L by the optical writing device to write the second color, thereby forming an electrostatic latent image on the surface of the photoconductor 10. .

Thereafter, each color developing device 14B of the developing device 14
Development is performed using the next one of K, 14C, 14M, and 14Y, and an image of the second color is formed on the photoconductor 10 subsequently. Then, the image is transferred by a transfer device (not shown) along with the rotation of the photoreceptor 10, and the second color image is transferred onto the intermediate transfer body 15 so as to overlap the first color image.

After the image is transferred, the surface of the photoreceptor 10 is cleaned by the cleaning device 17, the charge is removed by the charge removing device, and the charging device 13 is uniformly charged again. Then, similarly, the images of the third color and the fourth color are superimposed and transferred on the intermediate transfer body 15 to form a composite color image on the intermediate transfer body 15.

The intermediate transfer member 15 is wrapped around a plurality of rollers 18, and is rotated in a clockwise direction in the figure, transferred by a transfer roller 20 of a transfer device 19, and transferred to a recording medium 21 conveyed upward in the figure. Make a record. The surface of the intermediate transfer body 15 after the image transfer is cleaned by removing residual toner by a cleaning device (not shown).

By the way, in the color laser printer shown in FIG. 1, a roller type charging device 13 is disposed so as not to be located immediately below a developing position by the developing device 14, as shown in FIG. Therefore, the toner dropped from the developing position is
3 can be prevented, and the occurrence of charging unevenness can be prevented, so that a uniform charging potential can be obtained over a long period of time.

FIG. 2 is a schematic structural view of a main part of another color laser printer according to the present invention. In this example, the respective color developing units 14B of the developing device 14
K, 14C, 14M, and 14Y are arranged side by side, and the intermediate transfer body 15 is formed in a drum shape instead of a belt shape.

The other structure is almost the same as that of the example shown in FIG. 1. In FIG. 2, portions corresponding to FIG. 1 use the reference numerals used in FIG. 1 as they are, and duplicate explanations are omitted.

In the color laser printer shown in FIG. 2, as shown, a roller type charging device 13 is disposed so as to be shielded from a developing position by a developing device 14 by a photoreceptor 10. Accordingly, it is possible to prevent the toner dropped from the developing position after being blocked by the photoreceptor 10 from entering the charging device 13, thereby preventing the occurrence of charging unevenness and obtaining a uniform charging potential for a long period of time.

In this example, as shown in the figure, the roller type charging device 13 is disposed so as not to be directly below the cleaning position by the cleaning device 17. Therefore, it is possible to prevent the toner dropped from the cleaning position from entering the charging device 13, thereby preventing the occurrence of charging unevenness and obtaining a uniform charging potential for a long period of time.

FIG. 3 is a configuration diagram of the charging device 13 used in the color laser printer shown in FIG. 1, for example. In the charging device 13 shown in FIG. 3, the charging roller 12 having a diameter of, for example, 14 mm is housed in the casing 25. Then, the base end side of the shutter member 26 is attached to the developing device 14 side of the upper edge of the casing 25, and the front end side is provided close to the photoconductor 10.

The shutter member 26 prevents foreign matter from entering the charging device 13 from the developing position. In the example shown in FIG.
Although formed by a mylar such as ET, it is not limited to this, and may be formed by, for example, the casing 25 itself.

As described above, when the shutter member 26 for preventing foreign matter from entering the charging device 13 from the outside is provided, the shutter member 26 drops from the above-described developing position or other cleaning position. It is possible to prevent the toner from entering the charging device 13, prevent the occurrence of charging unevenness, and obtain a uniform charging potential over a long period of time.

FIG. 4 is a configuration diagram of another charging device used in the color laser printer shown in FIG. 1, for example. Similarly, the charging device 13 includes the charging roller 12 inside the casing 25.
To store. Also, the casing 2 is connected via the elastic member 27.
5, a roller cleaning member 28 is provided for cleaning the charging roller 12, which rotates along with the photoreceptor 10, with the rotation thereof.

Accordingly, even if the toner dropped from the developing position or the cleaning position, or the toner adhering to the photoreceptor 10 enters the charging device 13 little by little and adheres to the charging roller 12, for example, the adhered toner is removed. The charging roller 12 can be removed immediately by the roller cleaning member 28 to clean the charging roller 12, thereby eliminating contamination of the charging roller 12, preventing the occurrence of charging unevenness, and obtaining a uniform charging potential for a long period of time.

Although a nonwoven fabric is used as the roller cleaning member 27 in this example, a brush or a sponge may be used.

[0035]

As described above, according to the first aspect of the present invention, the roller-type charging device is disposed so as not to be directly below the developing position by the developing device, so that the toner dropped from the developing position is charged in the charging device. Thus, it is possible to prevent the occurrence of charging unevenness, obtain a uniform charging potential over a long period of time, and prevent deterioration in image quality.

According to the second aspect of the present invention, since the roller type charging device is disposed between the developing device and the developing position by the photoconductor, the toner dropped from the developing position by the photoconductor is charged. It is possible to prevent the toner from entering the apparatus, prevent the occurrence of charging unevenness, obtain a uniform charging potential over a long period of time, and prevent deterioration in image quality.

According to the third aspect of the invention, since the roller-type charging device is disposed so as not to be directly below the cleaning position by the cleaning device, the toner dropped from the cleaning position is prevented from entering the charging device. Prevent the occurrence of charging unevenness and obtain a uniform charging potential for a long time,
It is possible to prevent a decrease in image quality.

According to the fourth aspect of the present invention, since the shutter member is provided for preventing foreign matter from entering the charging device from the outside, the toner falling from the developing position or the cleaning position is charged by the shutter member. It is possible to prevent the toner from entering the apparatus, prevent the occurrence of charging unevenness, obtain a uniform charging potential over a long period of time, and prevent deterioration in image quality.

According to the fifth aspect of the present invention, since the roller cleaning member for cleaning the charging roller of the charging device is provided, for example, the toner dropped from the developing position or the cleaning position, or the toner adhering to the photoreceptor little by little. Even if the toner enters the charging device and adheres to the charging roller, the toner adhered to the charging roller can be immediately removed by the roller cleaning member to clean the charging roller, thereby eliminating contamination of the charging roller and preventing occurrence of uneven charging. Thus, a uniform charging potential can be obtained over a long period of time, and a decrease in image quality can be prevented.

According to the first to fifth aspects of the present invention, since the charging device is disposed below the photosensitive member, the image forming apparatus discharges the image onto the main body of the image forming apparatus with the image face down. Design can be facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a color laser printer according to the present invention.

FIG. 2 is a schematic configuration diagram of a main part of another color laser printer according to the present invention.

FIG. 3 is a configuration diagram of a charging device used in, for example, the color laser printer shown in FIG.

FIG. 4 is a configuration diagram of another charging device used in, for example, the color laser printer shown in FIG.

FIG. 5 is a schematic configuration diagram of a main part in a conventional color laser printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Photoconductor 12 Charging roller 13 Roller type charging device 14 Developing device 16 Cleaning blade 17 Cleaning device 21 Recording medium 25 Casing 26 Shutter member 27 Elastic member 28 Roller cleaning member

Claims (5)

[Claims] 1. An electrophotographic image forming apparatus having a roller-type charging device, wherein the charging device is arranged at a position below a photosensitive member while avoiding a position immediately below a developing position.
Electrophotographic image forming apparatus. 2. An electrophotographic image forming apparatus having a roller-type charging device, wherein the charging device is arranged at a position below the photosensitive member with a photosensitive member blocking the space between the developing device and the developing position. Photographic image forming apparatus. 3. The electrophotographic image forming apparatus according to claim 1, wherein the charging device is arranged at a position below the photoconductor so as to avoid a position immediately below a cleaning position. 4. An electrophotographic image forming apparatus having a roller-type charging device, wherein a shutter member for preventing foreign matter from entering the charging device from the outside is provided, and the charging device is disposed below the photosensitive member. Characterized by
Electrophotographic image forming apparatus. 5. An electrophotographic image forming apparatus having a roller-type charging device, wherein a roller cleaning member for cleaning a charging roller of the charging device is provided, and the charging device is arranged below a photosensitive member. Do
Electrophotographic image forming apparatus.