JPS6146533Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharger used in an image forming apparatus such as an electronic copying machine, and more particularly to prevention of contamination of shields and wires of the corona discharger.

As is conventionally known, a corona discharger that charges or removes static electricity from a photoreceptor in, for example, an electronic copying machine, generally applies a high voltage to a thin wire such as a tungsten wire to ionize the air and remove the charged object. Charge an object by attaching corona ions to it. In order to fully exhibit the ionization effect, it is important to prevent contaminants such as toner from adhering to the discharge wire. On the other hand, if you look at it from a different perspective, the discharge wire also works as an electrostatic precipitator, so toner contamination cannot be avoided. Therefore, in order to operate the electronic copying device smoothly, it is necessary to frequently clean the discharge wire of the corona discharger during periodic servicing, which is a troublesome task for the machine operator. .

By the way, if you look at the dirt on the discharge wire,
Both ends of the discharge wire are significantly dirtier than the center. This is because the ion current generated when corona is generated is blown out at the center of the corona discharger, and new air flows in from the longitudinal ends.
This airflow blows the toner scattered inside the machine into the discharger, which causes contamination, especially at the ends. Originally, fresh air is required to continuously generate corona, and therefore the ion flow cannot be stopped in order to fully operate the corona discharger. However, excessive air flow should be prevented, which is important in preventing toner from entering the corona discharger. Contamination of the discharge wire due to this airflow is unavoidable as described above, and since the end portion becomes dirty more quickly than the central portion in the longitudinal direction, good image quality cannot be obtained unless cleaned early.

The present invention solves the above problem, and its purpose is to significantly reduce the ingress of toner into the discharger by controlling the airflow, thereby reducing toner contamination of the discharge wire or shield. The present invention provides a corona discharger.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows a plan view of a conventional corona discharger. In the figure, 1 indicates the ion flow, and the discharger 1
It is sucked in from near the insulating blocks 2 and 3 at both ends, and blown out from the center. The toner is drawn into the corona discharger by the ion flow. By the way, on the surface of the photosensitive drum that is placed facing the corona discharger and is rotating in the direction of arrow A, there is an interfacial air flow that moves 2 to 3 mm away from the photosensitive drum surface as the drum rotates. An air flow W perpendicular to the longitudinal direction of the corona discharger traverses the discharger. This air flow has a significantly high velocity (80-150 mm/sec) due to the ion flow. In this conventional corona discharger, the insulating blocks 2 and 3 are located several mm to several centimeters away from the photosensitive drum, so the interfacial air flow W passes through the blocks as it is, and the ion flow 1 is sucked in. As a result, toner is also sucked in, and the discharge wire 4 and shield plate 5 are likely to be contaminated with toner.

The present invention attempts to make good use of this interfacial air flow, that is, it uses this interfacial air flow to blow away the toner carried by the ion flow, and forms an air curtain to move the toner into the discharge area of the corona discharger. This prevents toner from entering.

Figure 2 is a plan view of the corona discharger according to the present invention.
FIG. 3 is a sectional view taken along the - line, and FIG. 4 is a sectional view taken along the - line. In the figure, 6 is a plug for power supply, and 7 is a handle for pulling out the discharger from the main body of the copying machine. Note that members having the same functions as those in FIG. 1 are given the same reference numerals.

Now, on the side facing the photosensitive member of the insulating blocks 2 and 3 at both longitudinal ends of the corona discharger 1 according to the present invention, several protrusions are formed along the moving direction of the photosensitive drum 8 rotating in the direction of arrow A. 2a-2c, 3a-3c
It is formed. As shown in FIG. 3, these protrusions are close to the surface of the photosensitive drum 8 by about 2 mm or less, preferably around 1 mm, and in the direction of the protrusions, in other words, the air guide passages 2d, 2e between the protrusions. ;3
The directions d and 3e are directed away from the center of the discharger according to the rotational direction of the photosensitive drum 8, that is, toward the outside of the discharge area. As a result, as shown in FIG. 2, the interfacial airflow W is blown out as an airflow W deflected to the outside of the discharger. In this way, the toner carried by the ion current is prevented from entering by the high-speed air current W, and its direction of movement is changed and blown out of the apparatus, thereby significantly reducing contamination of the discharge wire.

As shown in FIG.
By narrowing the air guide passages 2d and 3e between b and 3c in the exit direction, it is possible to increase the speed of the interfacial airflow, and it is possible to blow off most of the toner between them.

When experiments were conducted using the corona discharger according to the present invention, it was possible to prevent toner staining by about 3 to 5 times compared to the conventional example. Also, at this time, some amount of toner was observed to adhere to the inner walls of the protrusions 2a to 2c and 3a to 3c. This clearly shows that the air guide passage of the present invention prevents floating toner from entering the discharge area.

Since the corona discharger of the present invention is constructed as described above, toner stains on the corona discharge wire and shield can be removed.
This can now be easily prevented with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a plan view of a conventional corona discharger, Fig. 2 is a plan view of a corona discharger according to the present invention, Fig. 3 is a sectional view taken along the - line, and Fig. 4 is a sectional view taken along the - line. It is. In the figure, 1... corona discharger, 2, 3...
Insulation block, 2a to 2c, 3a to 3c... protrusion, 2d, 2e, 3d, 3e... air guide passage,
4... Corona discharge wire, 5... Shield plate, 8...
Represents a photosensitive drum.

Claims (1)

[Claims for Utility Model Registration] (1) A corona discharger disposed facing a moving photosensitive member, having a corona discharge wire stretched in the longitudinal direction of the corona discharger and having at least an opening for discharge. In the corona discharger covered with a shield plate as described above, at least one of the longitudinal ends of the corona discharger has a convex portion extending toward the outside of the discharge area according to the moving direction of the photosensitive member. A corona discharger characterized in that an air guide passage is formed by the convex portion. (2) The above-mentioned air guide passage is provided so that the exit direction becomes narrower.
Corona discharger described in section.