JPH0452752Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a corona discharge device, and particularly to a corona discharge device suitable for use in printers, copying machines, etc. using electrophotography.

[Conventional technology]

In an image forming apparatus such as a copying machine, in order to charge the surface of an image bearing member such as a photosensitive drum or an insulating drum to a uniform potential, a corona discharger having a control grid (for example, Japanese Patent Publication No. 55-49738, (See Japanese Patent Application Laid-open No. 11255/1983) is used.

[Problem that the invention attempts to solve]

However, in such conventional corona dischargers, in order to perform corona discharge uniformly, it is necessary to form the grid lattice or mesh finely and precisely, which makes it difficult to process the grid (generally (etching is used)
There was a problem in that it was difficult to simplify the corona discharger and make it available at a fixed price.

The present invention was devised in view of these conventional problems and aims to provide a corona discharger with a simple structure and low cost.

[Means for solving problems]

In order to achieve the above-mentioned object, the corona discharger of the present invention includes a corona discharge electrode and a conductive shield member surrounding the corona discharge electrode and having a corona discharge opening. The corona discharger is characterized in that the shield member is grounded via a constant voltage element, a conductive member is attached to the shield member, and one end of the conductive member is brought into contact with the surface of the image carrier. .

[Effect]

The measures described above operate as follows.

Since the surface of the corona discharge electrode has fine irregularities, the discharge generated by the corona discharge electrode is not uniform and varies depending on the location of the electrode.

However, since the current density varies around a certain predetermined value, it is possible to place almost the amount of charge necessary for charging on an image carrier such as a photosensitive drum by this discharge.

A conductive member that is attached to a shield member held at a predetermined potential and has the same potential as the shield member is in contact with the image carrier, thereby reducing the surface potential on the image carrier. Charges in high areas flow through the conductive member to ground, and conversely, charges in areas with low surface potential are charged by the conductive member, so that the surface potential on the image carrier becomes uniform.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. As illustrated, the corona discharger 1 includes a corona discharge electrode 2, a conductive shield member 3, a nonlinear resistance element 4 connected to the shield member 3 and grounded for setting a constant voltage, and a shield. It is composed of a conductive brush 5 as a conductive member attached to the member 3 and a high voltage power supply 6 that supplies high voltage to the corona discharge electrode 2. Further, in the corona discharger 1 configured in this way, one end of the conductive brush 5 comes into contact with the surface of the object 7 to be discharged, such as a photosensitive drum, which rotates in the direction shown by arrow A in the figure. It is arranged like this.

Hereinafter, the operation of the above-mentioned corona discharger will be explained.

When a high voltage (for example, about -5000 V in the case of negative charging) is applied to the corona discharge electrode 2 by the high voltage power supply 6, a discharge occurs, and first, charge is accumulated on the surface of the discharged object 7, and the surface is charged. Ru.

However, the surface of the corona discharge electrode 2 is microscopically uneven and the surface shape is not uniform, so the discharge that occurs is not uniform and varies depending on the location of the corona discharge electrode 2. Become. Therefore, the amount of charge accumulated on the surface of the discharge object 7 also varies, and the surface potential of the discharge object 7 becomes non-uniform.

In other words, since the current density distribution in the longitudinal direction of the corona discharge electrode 2 is as shown in FIG. , an amount of charge larger than a certain predetermined amount and with a rough variation is accumulated on the surface of the discharged object 7.

Next, the surface of the discharge object 7 charged in this manner moves in the direction of arrow A in FIG. 1 as the discharge object 7 rotates and comes into contact with the conductive brush 5. Since the conductive brush 5 is at the same potential (for example, -1000V) as the shield member 3 which is grounded via the nonlinear resistance element 4, the potential on the surface of the discharged object 7 is higher than the predetermined potential. In part,
Excess charge flows through the conductive brush 5 to the ground via the shield member 3, and conversely, charge is injected from the conductive brush 5 into areas with low potential, resulting in The surface potential becomes uniform.

A desired surface potential when charging the discharge object 7 can be obtained by appropriately selecting the nonlinear resistance element 4.

As a result of experiments using the corona discharger 1 of the present invention, it was found that the potential was approximately 1/2 of the voltage set by the nonlinear element 4 (for example, when the voltage set by the nonlinear resistance element 4 was -1000 V) It has been found that the surface of the material 7 to be discharged can be charged to a potential of about -500V.

In the above embodiment, a brush was used as the conductive member, but the present invention is not limited to brushes, and any conductive material such as a conductive blade or a conductive sponge may be used. Of course.

Further, even if the conductive member is provided not only on one side of the shield member 3 but also on both sides, the effect of the present invention will not be affected in any way.

[Effect of idea]

As explained above, according to the present invention, the configuration includes a corona discharge electrode, a conductive shield member surrounding the corona discharge electrode and having a corona discharge opening, and a corona that charges the surface of the image carrier. In the discharger, the shield member is grounded via a constant voltage element, and a conductive member is attached to the shield member, and one end of the conductive member is brought into contact with the surface of the image carrier. The surface of the carrier can be charged to a desired surface potential and to a uniform potential. Therefore, compared to conventional corona dischargers, it can have a simpler configuration.
It is also possible to provide the effect of making it possible to lower the price.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the present invention;
The figure is a graph showing the distribution of current density due to the corona discharger. 1...Corona discharger, 2...Corona discharge electrode,
3... Shield member, 4... Nonlinear resistance element, 5
...Conductive member, 6...High voltage power supply.

Claims (1)

[Scope of utility model registration request] In a corona discharger that has a corona discharge electrode and a conductive shield member that surrounds the corona discharge electrode and has a corona discharge opening, and charges the surface of an image carrier, the shield member is connected to the conductive shield member through a constant voltage element. A corona discharger characterized in that a conductive member is attached to the shield member while being grounded, and one end of the conductive member is brought into contact with the surface of the image carrier.