JPH09185201A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress toner splashed from a developing device to be attached to an electrostatic charge device and to stably obtain an excellent image. SOLUTION: This device is constituted so that the outside circumferential surface of a cylindrical image carrier 1 is electrostatically charged by the electrostatic charge device 2 by rotating the carrier 1 and an electrostatic latent image is formed on the outside circumferential surface of the electrostatically charged carrier 1 and developed by supplying the toner to the carrier 1 from the developing device 3. In such a case, the outside circumference side of the carrier 1 is provided with the electrostatic charge device 2 and the developing device 3 so that an angle θ formed by the electrostatic charge device 2 and the developing device 3 with respect to the center shaft 1a of the carrier 1 becomes within the range of 180 deg.±30 deg..

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 such as a copying machine or a printer, and more particularly, to rotating a cylindrical image carrier to charge its outer peripheral surface by a charging device. When the electrostatic latent image is formed on the outer peripheral surface of the charged image carrier and the toner is supplied from the developing device to the image carrier to develop the electrostatic latent image, the toner is prevented from adhering to the charging device. The present invention relates to the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, various types of image forming apparatuses such as copying machines and printers have been used, and generally, those utilizing an electrophotographic system have been widely used.

In the conventional image forming apparatus using the electrophotographic method as described above, generally, as shown in FIG. 1, the image carrier 1 formed in a cylindrical shape is rotated and the image carrier 1 is rotated. The outer peripheral surface of the is charged by the charging device 2,
An electrostatic latent image is formed on the outer peripheral surface of the image bearing member 1 thus charged by an exposing unit (not shown), and then the electrostatic latent image formed on the outer peripheral surface of the image bearing member 1 is developed. Device 3
The toner is supplied from the developing unit to develop the toner image formed on the image carrier 1 by the transfer device 4 (not shown).
The toner remaining on the surface of the image carrier 1 after the transfer is cleaned by the cleaning device 5 while the image is formed by transferring the toner to the cleaning device 5.
The electric potential remaining on the surface of the image carrier 1 is eliminated by a neutralizing device (not shown) as necessary.

Here, in the conventional image forming apparatus, a developing device for supplying toner to the charging device 2 for charging the outer peripheral surface of the image bearing member 1 and the image bearing member 1 on which the electrostatic latent image is formed for development. When the device 3 is provided on the outer peripheral side of the image carrier 1, generally, as shown in FIG. 1, an angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1 a of the image carrier 1.
Was about 90 °.

However, when an image is formed by such an image forming apparatus, the toner scattered from the developing device 33 easily adheres to the charging device 2 and the amount of toner adhered to the charging device 2 gradually increases. When the outer peripheral surface of the image carrier 1 is charged by the charging device 2 having a large amount of toner attached thereto, uneven charge occurs on the outer peripheral surface of the image carrier 1 and uneven density occurs in the formed image. ,
There is a problem that image noise such as background fog occurs.

Therefore, in the prior art, in order to prevent the toner scattered from the developing device 3 from adhering to the charging device 2 as described above, the portion between the charging device 2 and the developing device 3 is sealed. A member (not shown) is provided so as to be in contact with the outer peripheral surface of the image carrier 1, and the seal member prevents the toner scattered from the developing device 3 from adhering to the charging device 2. .

However, when the seal member is provided so as to be in contact with the outer peripheral surface of the image bearing member 1 as described above, uneven charging on the outer peripheral surface of the image bearing member 1 is caused by the contact between the seal member and the image bearing member 1. Then, the same problem as in the above case occurs, and this seal member is deformed by the contact with the rotating image carrier 1, and the toner scattered from the developing device 3 is charged by the charging device 2.
There is a problem that it is impossible to sufficiently suppress the adhesion to the.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems in an image forming apparatus using an electrophotographic system such as a copying machine and a printer.

That is, in the present invention, the cylindrical image carrier as described above is rotated to charge the outer peripheral surface thereof by the charging device, and the outer peripheral surface of the image carrier thus charged is statically charged. In an image forming apparatus that forms an electrostatic latent image and supplies toner from the developing device to the image carrier to develop the electrostatic latent image, when the image is formed by the image forming apparatus, the development is performed. To prevent the toner scattered from the device from adhering to the charging device, and prevent uneven charging on the outer peripheral surface of the image carrier when the outer peripheral surface of the image carrier is charged by the charging device, An object is to enable stable image formation.

[0010]

In order to solve the above problems, in the image forming apparatus according to the present invention, the cylindrical image carrier is rotated and its outer peripheral surface is charged by the charging device. In the image forming apparatus that forms an electrostatic latent image on the outer peripheral surface of the image bearing member thus charged, and supplies toner to the image bearing member from the developing device to develop the electrostatic latent image, When the device and the developing device are provided on the outer peripheral side of the image carrier, the angle formed by the charging device and the developing device with respect to the central axis of the image carrier is within the range of 180 ° ± 30 °.

Here, when the charging device and the developing device are provided on the outer peripheral side of the image carrier as in the image forming apparatus of the present invention, the charging device and the developing device form the central axis of the image carrier. If the angle is in the range of 180 ° ± 30 °, even if the toner is scattered from the developing device,
It is very unlikely that this toner reaches the position of the above-mentioned charging device and adheres thereto, uneven charging when the outer peripheral surface of the image carrier is charged by the charging device is suppressed, and uneven density occurs in the formed image. And the occurrence of image noise such as background fog are prevented.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of an image forming apparatus according to the present invention will be specifically described with reference to the accompanying drawings, and when the image forming apparatus according to the embodiment of the present invention is used, a developing device will be described. It is revealed that the scattered toner is less likely to adhere to the charging device.

Also in the image forming apparatus in this embodiment, as shown in FIG. 2, the image carrier 1 having a cylindrical shape is used, and the image carrier 1 is rotated to rotate the outer peripheral surface of the image carrier 1. Is charged by the charging device 2, and an electrostatic latent image is formed on the outer peripheral surface of the image bearing member 1 thus charged by an exposing means (not shown), and then formed on the outer peripheral surface of the image bearing member 1. Toner is supplied to the formed electrostatic latent image from the developing device 3 to develop the electrostatic latent image, and the toner image formed on the image carrier 1 is transferred to a transfer paper (not shown) by the transfer device 4 to form an image. I am trying.

Here, in the image forming apparatus of this embodiment, the image is formed under the condition that it is not necessary to clean the surface of the image carrier 1 after the transfer or to eliminate the charge. As described above, the toner remaining on the surface of the image carrier 1 after the transfer may be removed by the cleaning device 5, or the potential remaining on the surface of the image carrier 1 may be neutralized by the neutralization device. It is possible.

In the image forming apparatus of this embodiment, the charging device 2 for charging the outer peripheral surface of the image carrier 1 as described above, and the image carrier 1 on which the electrostatic latent image is formed.
When the developing device 3 that supplies toner to the developing device 3 and develops it on the outer peripheral side of the image carrier 1, as shown in FIG.
The angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 is set to about 180 °, and the charging device 2 and the developing device 3 are separated via the image carrier 1. It is designed to be installed at the position.

Therefore, in the image forming apparatus of this embodiment, when the image is formed as described above,
Even if the toner is scattered from the developing device 3, the scattered toner is very rarely guided to the position of the charging device 2 and adhered thereto, and even when a large number of images are formed, the charging is performed. The amount of toner adhering to the device 2 is reduced, uneven charging when the outer peripheral surface of the image carrier 1 is charged by the charging device 2 as described above is suppressed, and unevenness in density or background fog in the formed image is suppressed. Image noise is less likely to occur, and good images can be stably obtained.

Next, as shown in this embodiment, the charging device 2 is set so that the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 is about 180 °.
As shown in FIG. 1, the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 is about 90 °. And then
A conventional image forming apparatus provided with the charging device 2 and the developing device 3 is used, and image formation is performed by each image forming device.
The relationship between the amount of toner adhering to each charging device 2 and the number of image formed sheets was examined, and the results are shown in FIG.

As a result, when the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 is set to about 180 ° as in the image forming apparatus in the above embodiment. In contrast, the amount of toner adhered to the charging device 2 was much smaller than that of the conventional image forming apparatus.

The relationship between the amount of toner adhering to the charging device 2 and the uneven density in the image formed as described above was examined, and the result is shown in FIG.

As a result, as the amount of toner attached to the charging device 2 increases, the density unevenness in the formed image also increases. As in the image forming apparatus of this embodiment, the amount of toner attached to the charging device 2 increases. When the amount is small, the density unevenness in the formed image is very small as compared with the conventional image forming apparatus.

Next, in the image forming apparatus as described above, the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis of the image carrier 1 is changed to form images of 200,000 sheets each. The relationship between the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 and the amount of toner adhered to the charging device 2 was examined, and the result is shown in FIG.

As a result, when the angle θ formed by the charging device 2 and the developing device 3 with respect to the central axis 1a of the image carrier 1 is set within the range of 180 ° ± 30 ° as shown in the present invention, The amount of toner adhered to the charging device 2 was very small.

[0023]

As described above in detail, in the image forming apparatus according to the present invention, the charging device for charging the outer peripheral surface of the cylindrical image carrier and the electrostatic charge by supplying the toner to the image carrier. When the developing device for developing the latent image is provided on the outer peripheral side of the image carrier, the angle formed by the charging device and the developing device with respect to the central axis of the image carrier is in the range of 180 ° ± 30 °. Even if toner is scattered from the developing device, it is very rare that the toner reaches the position of the charging device and adheres thereto.

As a result, in the image forming apparatus according to the present invention, even when a large number of images are formed, uneven charging occurs when the outer peripheral surface of the image carrier is charged by the charging device. As a result, it is possible to prevent uneven density in an image to be formed and to prevent image noise such as background fog from being generated, and a good image can be obtained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a conventional image forming apparatus.

FIG. 2 is a schematic explanatory diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the amount of toner adhering to each charging device and the number of images formed when images are formed using the image forming apparatus of the embodiment and the conventional image forming apparatus shown in FIG. It is the figure which showed.

FIG. 4 is a diagram showing a relationship between a toner adhesion amount in a charging device and density unevenness in a formed image.

FIG. 5 is a diagram showing a relationship between an angle θ formed by a charging device and a developing device with respect to a central axis of an image carrier and an amount of toner adhered to the charging device.

[Explanation of symbols]

1 image carrier 1a central axis 2 charging device 3 developing device θ angle formed by the charging device and the developing device with respect to the central axis of the image carrier

Claims (1)

[Claims] 1. A developing device, wherein a cylindrical image carrier is rotated to charge an outer peripheral surface of the image carrier by a charging device, and an electrostatic latent image is formed on the outer peripheral surface of the image carrier thus charged. In the image forming apparatus that supplies toner to the image carrier to develop the electrostatic latent image, when the charging device and the developing device are provided on the outer peripheral side of the image carrier, with respect to the central axis of the image carrier, The angle between the charging device and the developing device is 180 ° ± 3
An image forming apparatus characterized in that the range is 0 °.