JPS6145231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharge device, and particularly to a corona discharge device that is incorporated into an electrophotographic apparatus to charge a photoreceptor.

A typical example of a conventional corona discharge device used for the above purpose is shown in FIG. In this example, a body 1 is provided which is made of a conductive material such as metal and acts as a corresponding electrode;
is fixed within the electrophotographic apparatus such that its open end is close to the surface of the photoreceptor 2 of the electrophotographic apparatus. The photoreceptor 2 is moved in the direction of the arrow in FIG. 1 at a predetermined speed relative to the corona discharge device. A corona discharge wire 3 is provided in the internal space of the main body 1, and the corona discharge thin wire 3 is located approximately in the middle between both side walls 4 and 5 of the main body 1 and extends approximately parallel to the side walls 4 and 5. It is insulated and supported by the main body 1 in such a manner. The corona discharge device constructed in this manner is arranged such that the side walls 4 and 5 and the corona discharge fine wire 3 extend substantially perpendicular to the moving direction of the photoreceptor 2. With such a configuration, when a predetermined voltage is applied between the corona discharge wire 3 and the main body 1 during use and corona discharge occurs between them, the area near the side wall 4 of the main body 1, that is, of the corona discharge device A relatively large current, that is, an initial charging current, rapidly flows from the corona discharge wire 3 to the portion of the photoreceptor 2 moving on the entry side, and the photoreceptor portion is connected to the side wall 5 of the main body 1, that is, the exit of the corona discharge device. The current flowing to the photoreceptor decreases rapidly as it moves up the side, and almost no charging current flows at the end of charging.

In a typical electrophotographic device, a corona discharge device as shown in Fig. 1 is installed in the process of forming an electrostatic image on the surface of a photoreceptor, and the electrostatic image on the photoreceptor is developed by a developer containing developer powder. Developed by the device. This developing device is installed in the electrophotographic device,
The developing powder image on the photoreceptor is transferred to a recording paper, and then the developer powder remaining on the photoreceptor is removed by a cleaning device so that the photoreceptor can be reused.

However, the photoreceptor is not completely cleaned, and when the photoreceptor is reused, a small amount of developing powder is attached to the photoreceptor, and a small amount of developing powder is floating in the electrophotographic apparatus. When these developing powders move toward the entry side of the corona discharge device during repeated use of the photoreceptor, they are caused to collapse at the lower end of the side wall 4 of the main body 1 due to the action of the electric field generated by the large-value cut-off charge current as described above. It partially attaches and accumulates in the vicinity. As a result, the corona discharge of the corona discharge device becomes non-uniform, and the photographic image formed becomes unclear.

FIG. 2 shows another example of a conventional corona discharge device, in which two corona discharge wires 6 and 7 are provided, each of which is connected to the main body 1. It is spaced approximately equal distances from the side walls 4 and 5. Further, an example of the conventional corona discharge device shown in FIG. 3 is such that a plurality of ground grid wires 9 are arranged at the open end of the main body 1 in the device shown in FIG.
It is installed almost parallel to 7. In these devices shown in FIGS. 2 and 3, as in the case of the device shown in FIG.
There is a drawback in that developing powder accumulates near the tip of the side wall 4, producing a photographic image of poor quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a corona discharge device having a simple and convenient structure that eliminates the drawbacks of the conventional devices as described above.

A fourth preferred example of the corona discharge device according to the present invention
As shown in FIG. First, in the example shown in FIG. 4, the corona discharge wire 8 is placed closer to the exit side of the corona discharge device, and is placed between the corona discharge wire 8 and the side wall 4 of the main body 1 on the entry side of the corona discharge device. When the distance between the corona discharge wire 8 and the side wall 5 of the main body 1 on the exit side of the corona discharge device is b, the relationship a>b holds. With this configuration, the value of the initial charging current flowing to the photoreceptor on the entrance side of the apparatus can be lowered than in conventional apparatuses, making it difficult for developing powder to adhere to the side wall 4, resulting in good image quality. Photographic images can be produced in extremely large quantities.

In the apparatus shown in FIG.
The relationship is the same as the above relationship in the device shown in the figure.
Further, a plurality of grid lines 9 are provided at the open end of the main body 1, and these grid lines are arranged at a distance from the side wall 4 of the main body 1. With this configuration,
The effect of preventing developing powder from adhering to the side wall 4 is further enhanced. Furthermore, in this device, the end of the side wall 4 near the photoreceptor 2 is not curved inward;
It is formed straight, which further enhances the effect of preventing the developing powder from adhering to the side wall 4.

The effects of the present invention were confirmed by the following examples. That is, a photoreceptor consisting of an electrode layer, a photoconductive layer containing cadmium sulfide powder, and an insulating layer is attached to the circumferential surface of a rotating drum, and the corona discharge device (applied voltage
6000V) to uniformly charge the surface of the photoreceptor, then use the corona discharge device shown in Figure 5 (applied voltage -6000V).
The photoreceptor was charged to the opposite polarity by a method, and at the same time an original optical image was irradiated onto the photoreceptor, and then a uniform light beam was irradiated onto the photoreceptor to form an electrostatic image on its surface. In the device shown in Figure 4 used here, a and b are 20 mm and 10 mm, respectively.
, and is arranged so that the open end is approximately 2 mm away from the surface of the photoreceptor. Also, the device in Figure 5 is a
and b are 30 mm and 10 mm, respectively, the distance between the side wall 4 and the nearest grid line is about 19 mm, the distance between the grid lines is 3 mm, and the open end is separated from the photoreceptor surface by about 3 mm. It is located. The electrostatic image on the photoreceptor described above was developed by a magnetic roller type developing device, and after the image was transferred to recording paper, the surface of the photoreceptor was cleaned by rubbing with an elastic member. As a result of continuously performing the above operations to create photographic images, even after creating 10,000 photographic images, there was almost no developing powder adhering to the two corona discharge devices, and even after that, the images remained clear. I was able to create a photographic image of good quality.

Next, as a result of repeatedly creating photographic images using the corona discharge apparatus shown in FIGS. 1 and 3 in the same manner as the image forming operation described above, after 50 image formations, the developed powder entered the corona discharge apparatus. A lid was deposited on the side wall of the main unit, resulting in an unclear photographic image.

[Brief explanation of the drawing]

1, 2 and 3 are side sectional views of a conventional corona discharge device, and FIGS. 4 and 5 are side sectional views of different examples of the corona discharge device according to the present invention. DESCRIPTION OF SYMBOLS 1... Main body, 2... Photoreceptor, 3... Corona discharge wire, 4, 5... Side wall, 6, 7, 8... Corona discharge wire, 9... Grid wire.

Claims (1)

[Claims] 1. A conductive body having an entrance side wall and an exit side wall defining a corona discharge opening in proximity to an electrophotographic photoreceptor on which visible image formation with a developer, transfer, and cleaning steps are repeatedly performed, and a conductive body within the body. the only corona discharge wire provided in the space, and the distance from the entrance side wall to the corona discharge wire is greater than the distance from the exit side wall to the corona discharge wire. 1. A corona discharge device characterized in that the initial charging current on the entrance side is regulated to a value that prevents developer from adhering to the entrance side wall by arranging the corona discharge device at a position where the charging current is long.