JP2002014518A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of stably controlling the potential of an electrostatic latent image carrier even though the device is used for a long time and stably forming an excellent image over a long term. SOLUTION: This image forming device is constituted of at least a discharge wire, a counter electrode for discharge installed near the discharge wire, the electrostatic latent image carrier on the surface of which an electrostatic latent image is formed, and a potential control grid provided between the discharge wire and the electrostatic latent image carrier. By applying DC voltage on the discharge wire, the surface of the electrostatic latent image carrier is electrified. Then, the surface of the potential control grid is coated with a dielectric.

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 for forming an image by transferring a developer to a recording medium, and more particularly, to a scorotron type charging device in which the surface of a potential control grid is coated with a dielectric. The present invention relates to an image forming apparatus having a container.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image carrier such as a photosensitive drum on which an electrostatic latent image is formed on a surface and the surface of the electrostatic latent image carrier are uniformly charged by corona discharge. A scorotron-type charger, electrostatic latent image forming means for forming the electrostatic latent image on the surface of the electrostatic latent image carrier after charging by the charger, and an electrostatic latent image forming means formed by the electrostatic latent image forming means. There is known an image forming apparatus including a developing unit for developing the electrostatic latent image with a developer such as toner. In this type of image forming apparatus,
An electrostatic latent image is formed by electrostatic latent image forming means on the surface of the electrostatic latent image carrier uniformly charged by the charger, and the electrostatic latent image is formed by a developer charged by friction charging or the like by developing means. An image is formed by developing the latent image and then transferring the developer to a recording medium.

When a scorotron-type charger for uniformly charging the surface of an electrostatic latent image carrier by corona discharge is used, the scorotron-type charger may be deteriorated for the following reasons, and must be replaced. In some cases, the cartridge is housed in a cartridge as one of the replacement parts.

In these image forming apparatuses, various external additives such as silica are added to the toner in order to ensure the fluidity of the toner. Further, in a fixing device for fixing an image to transfer paper, silicone oil or the like is used to prevent fusion of toner, and these are floating in the air. By discharging in the charging section, those substances adhere to the potential control grid due to a dust collection effect, and uneven discharge occurs due to the coating, and an image may not be appropriately formed in a portion corresponding to the coating. Therefore, the scorotron-type charger has to be replaced, and it is difficult to form the charger separately from other replacement parts and use it repeatedly as described above.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to stably control the potential of an electrostatic latent image carrier even when used for a long time and to stably form an excellent image over a long period of time. An object of the present invention is to provide an image forming apparatus.

[0006]

The above objects of the present invention have been attained by the following constitutions.

[0007] 1. At least a discharge wire, a counter electrode for discharge placed near the discharge wire, an electrostatic latent image carrier having an electrostatic latent image formed on its surface, and a portion between the discharge wire and the electrostatic latent image carrier An image forming apparatus comprising a potential control grid provided on a surface of the electrostatic latent image carrier by applying a DC voltage to the discharge wire, wherein the surface of the potential control grid is coated with a dielectric material. An image forming apparatus, comprising:

[0008] 2. The potential control grid surface is charged by applying a voltage of the opposite polarity to the discharge portion to the conductor portion of the potential control grid, and the voltage applied to the conductor is set to a voltage lower than that at the time of charge saturation. 2. The image forming apparatus according to claim 1, wherein a potential difference is generated inside to control a current value flowing through the electrostatic latent image carrier.

3. 2. The image forming apparatus according to claim 1, wherein a voltage value applied to the potential control grid is -5 kV to 5 kV.

[0010] 4. 4. The image forming apparatus according to claim 1, wherein the dielectric is glass.

5. 4. The image forming apparatus according to claim 1, wherein the dielectric is a ceramic material.

6. (5) The ceramic material as described in (5), wherein the ceramic material is at least one selected from alumina, zirconia, borane nitride, beryllium oxide, and silicon nitride.
The image forming apparatus as described in the above.

7. The image forming apparatus according to any one of claims 1 to 3, wherein the dielectric is a resin material.

8. 8. The image forming apparatus according to the item 7, wherein the resin material is at least one selected from polyethylene, polyester, polystyrene, silicone, and fluororesin.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described by way of embodiments with reference to the drawings. FIG. 1 is a cross-sectional view of the charger and the electrostatic latent image carrier of the image forming apparatus of the present invention. The charger of the present invention is a scorotron charger, and has a discharge wire 3.
And an opposite electrode 2 for discharge installed in the vicinity thereof, an electrostatic latent image carrier 6 on which an electrostatic latent image is formed on the surface, and provided between the discharge wire 3 and the electrostatic latent image carrier 6. It consists of a potential control grid 1. Then, a DC voltage is applied to the discharge wire 3 by a DC power supply 4 to discharge the surface of the electrostatic latent image carrier 6 to uniformly apply a charge. The potential control grid 1 of the present invention is characterized in that its surface is coated with a dielectric. Examples of the dielectric include glass or a ceramic material, and examples of the ceramic material include alumina, zirconia, borane nitride, beryllium oxide, and silicon nitride. In the present invention, the dielectric is preferably glass.

Since the conventional potential control grid is a conductor grid, if discharge is performed for a long time, discharge products adhere to the surface of the potential control grid, which causes discharge unevenness. Therefore, it was necessary to periodically replace the potential control grid. The potential control grid 1 of the present invention covers the conductor grid with a dielectric, so that even if dirt such as discharge products adheres, the influence on image unevenness is smaller than that of the conductor grid, and a voltage can be applied inside the dielectric. Therefore, it was found that the grid was a highly durable potential control grid capable of controlling the value of the current flowing through the electrostatic latent image carrier 6.

A second aspect of the present invention is to apply a voltage having a polarity opposite to that of a discharge portion to a conductor portion of the potential control grid 1 by a DC power supply 5 to charge the surface of the potential control grid 1 and to charge the conductor with a voltage saturated. This is an invention of an image forming apparatus which controls a current value flowing through the electrostatic latent image carrier 6 by generating a potential difference between the surface and the inside of the potential control grid 1 by setting the voltage lower than the time. At this time, the voltage value applied to the potential control grid 1 is preferably -5 kV to 5 kV.

The conductor of the potential control grid is covered with a dielectric material such as glass, and the internal conductors are completely separated from the potential control grid 1, the discharge wire 3, and the discharge counter electrode 2 except for the voltage application part. When a positive voltage is applied to the potential control grid 1 and a negative corona discharge is caused to the discharge wire 3 by the scorotron charging method, the surface of the potential control grid 1 is negatively charged by electrons. When the surface of the potential control grid 1 is completely charged, the potential of the entire grid becomes 0V. At this time, when the voltage inside the grid is reduced, a potential difference is generated between the surface and the inside of the potential control grid 1, and a negative electric field is generated in the entire potential control grid 1. Using this potential difference, the amount of current flowing through the electrostatic latent image carrier 6 can be controlled.

After the potential control grid 1 was completely charged at 500 V, the value of the current flowing to the electrostatic latent image carrier 6 was measured. Next, the voltage of the potential control grid 1 was changed from 500 V as shown in Table 1, and the value of the current flowing on the side of each electrostatic latent image carrier 6 was measured. Similarly, after the potential control grid 1 is completely charged at 1000 V, the value of the current flowing to the side of the electrostatic latent image carrier 6 is measured, and the voltage of the potential control grid 1 is further changed as in the case of 500 V. And the results are shown in Table 2.

[0020]

[Table 1]

[0021]

[Table 2]

From Tables 1 and 2, in the image forming apparatus of the present invention, it is possible to control the value of the current flowing to the electrostatic latent image carrier 6 side. Also, the potential control grid is set to 1000
When charged to V, it is about 2 times more than when charged to 500V.
It is possible to have twice the control width.

[0023]

According to the present invention, there is provided an image forming apparatus capable of stably controlling the potential of the electrostatic latent image carrier even when used for a long time and stably forming an excellent image over a long period of time. I was able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a charger and an electrostatic latent image carrier of an image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric potential control grid 2 Counter electrode for discharge 3 Discharge wire 4 DC power supply 5 DC power supply 6 Electrostatic latent image carrier

Claims (8)

[Claims] 1. An electrostatic latent image carrier having an electrostatic latent image formed on at least a discharge wire, a discharge counter electrode disposed near the discharge wire, and the discharge wire and the electrostatic latent image It consists of a potential control grid provided between the carriers, and by applying a DC voltage to the discharge wire,
An image forming apparatus for discharging a surface of the electrostatic latent image carrier, wherein the surface of the potential control grid is coated with a dielectric. 2. A potential control grid surface is charged by applying a voltage having a polarity opposite to that of a discharge portion to a conductor portion of the potential control grid, and the voltage applied to the conductor is set to a voltage lower than that at the time of charge saturation. 2. The image forming apparatus according to claim 1, wherein a potential difference is generated between the surface of the potential control grid and the inside thereof to control a current value flowing through the electrostatic latent image carrier. 3. The voltage value applied to the potential control grid is-
2. The image forming apparatus according to claim 1, wherein the voltage is 5 kV to 5 kV. 4. The image forming apparatus according to claim 1, wherein the dielectric is glass. 5. The image forming apparatus according to claim 1, wherein the dielectric is a ceramic material. 6. The image forming apparatus according to claim 5, wherein the ceramic material is at least one selected from alumina, zirconia, borane nitride, beryllium oxide, and silicon nitride. 7. The image forming apparatus according to claim 1, wherein the dielectric is a resin material. 8. The image forming apparatus according to claim 7, wherein the resin material is at least one selected from polyethylene, polyester, polystyrene, silicone, and fluororesin.