JPH0527857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharge device, for example, a corona discharge device used in an electrophotographic copying machine or the like to uniformly charge or eliminate static electricity on the surface of a photoreceptor.

For more details, please refer to the applicant's previous proposal (Japanese Patent Application Laid-Open No.
188062) regarding improvements in the corona discharge device.

The corona discharge device according to the above proposal includes a wire-shaped corona discharge electrode, a shield member that surrounds the wire-shaped corona discharge electrode and has a corona discharge opening, and an insulating block that supports the corona discharge electrode. An auxiliary shield member made of a conductive material that is insulated from others and grounded is provided on the top surface of the insulating block.The existence of this auxiliary shield member prevents outside air from being blown out from the corona discharge opening. Replacement flow into the inner part of the shield member occurs gradually in an approximately evenly distributed manner outside the corona discharge opening, including the area where the insulating block exists, and as a result, external foreign matter enters the inner space of the shield member. As a result, the rate of contamination of the corona discharge electrode and the inner wall surface of the shield member is reduced, making it possible to maintain good discharge performance of the corona discharge device over a long period of time.

However, in the conventional configuration described above, since the auxiliary shield member is at ground potential, there is a limit to the amount of ion wind blown out due to the induction of discharge.

The purpose of the present invention is to solve the above-mentioned conventional problems,
This greatly reduces the incorporation of external foreign matter into the shield member.

The corona discharge device of the present invention that achieves the above object includes an insulating block that supports a corona discharge electrode provided at both ends of a shield member, and a conductive block provided on the opening side (top surface) of this insulating block. A voltage having a polarity opposite to that applied to the corona discharge electrode is applied to the conductive member, and
An insulating member is provided at a portion of the conductive member facing the corona discharge electrode.

The embodiments of the present invention will be described above with reference to the drawings.

Figures 1 and 2 are a longitudinal side view and a cross-sectional view of a concrete example device (corotron) as an example of improving the incorporation of external elements into the contents of the shield member. A conductive trough-like shield member, 2, a discharge wire serving as a corona discharge electrode, stretched between insulating blocks 3 and 4 disposed at both left and right ends of the shield member, and disposed within the shield member, 5; 5 is a conductive auxiliary shield member disposed on the top surface of the insulating blocks 3 and 4 to be insulated from others; 6 is a conductive tension spring that constantly tensions the discharge wire; 7 is a power supply terminal for the discharge wire; 8 is a high voltage power supply, 9 is a corona discharge aperture, and 10 is a surface of an object to be discharged, such as a photoreceptor surface, facing the corona discharge aperture.

The shield member 1 is grounded. discharge wire 2
receives a voltage from a high-voltage power source 8 via a power supply terminal 7 and a conductive tension spring 6 . The auxiliary shield members 5, 5 are grounded or applied with a voltage of opposite polarity to the corona wire 2, respectively.

The electric field between the shield member 1 and the discharge wire 2 and between the discharge wire 2 and the auxiliary shield member 5 causes the gas (air) around the discharge wire to become ionized, and the ionized charged particles are directed toward the discharge opening 9. Once moving, at that time, it gives kinetic energy to other gas molecules and generates a blow-out type of ion wind a at the discharge opening, and the surface 10 of the object to be discharged is charged or neutralized by the ion wind a.

On the other hand, as the ion wind a is blown out from the discharge opening 9, the inner space of the shield member 1 becomes negative pressure, so the outside air b is blown out from the discharge opening 9 into the inner space of the shield member, replacing the ion wind a. Flow into.

In this case, if the above-mentioned auxiliary shield members 5, 5 are not provided on the top surfaces of the insulating blocks 3, 4, the outside air b flows into the interior of the shield member mainly at both left and right ends of the discharge opening 9. This occurs locally from the openings near the insulating blocks 3 and 4. This is because both ends of the shield member 1 are insulating blocks, so the blowing wind pressure of the ion wind from the openings closer to the insulating blocks in the entire area of the discharge opening 9 is weaker than from other openings. . The flow velocity of the outside air that intensively flows into the interior of the shield member from the discharge opening portions near the insulating blocks 3 and 4 becomes quite strong in order to compensate for the negative pressure within the entire interior of the shield member.

As a result, the rate of entrainment of foreign matter into the inner space of the shield member 1 increases due to the strong inflow of outside air, and the rate of contamination of the discharge wire 2 and the inner wall surface of the shield member 1 increases. Foreign matter contamination on the inner wall surface of the discharge wire 2 and the shield member 1 is a major cause of uneven discharge, and in the case of a copying machine, it has a great effect on image quality, so frequent cleaning is necessary.

On the other hand, in the case of a device in which auxiliary shield members 5, 5 are disposed on the top surfaces of insulating blocks 3, 4 as shown in FIG. , 4 is promoted, and the ion wind is blown out almost evenly and gradually at each part along the length of the discharge opening, including this discharge opening. As a result, the rate of foreign matter being taken into the interior space of the shield member is significantly reduced, and the rate of contamination of the discharge wire 2 and the inner wall surface of the shield member due to foreign matter over time is reduced, resulting in good discharge performance of the device over a long period of time. It has a major feature that allows it to be maintained.

The corona discharge device having the structure in which the auxiliary shield members 5, 5 are disposed on the top surfaces of the insulating blocks 3, 4 has the above-mentioned great features and effects and is recommended, but there are some problems. When a high electric field is required, there is a possibility that dielectric breakdown (leakage) will occur between the discharge wire 2 and the auxiliary shield members 5, 5 disposed on the top surfaces of the insulating blocks 3, 4. Can be mentioned.

The present invention eliminates the above-mentioned possibility of dielectric breakdown, and an embodiment will be described with reference to FIG.

FIG. 3 shows a specific example of the embodiment of the present invention. In this example, the top plates 3a, 4a of the insulating blocks 3, 4 are extended at their ends 3b, 4b.
In b, the inner surfaces of the auxiliary shield members 5, 5 directly facing the corona discharge wire 2 are covered with a concealing coating. The above-mentioned portion may be covered with a polyethylene terephthalate film (trade name: Mylar film) or other insulating film, or coated with an insulating material.

In this way, the insulating coating layers 3b, 4
The presence of b eliminates the possibility of dielectric breakdown between the corona discharge wire 2 and the auxiliary shield members 5, 5 even in the case of a high electric field, resulting in a safe corona discharge device. Furthermore, even if the above insulating coating layers 3b and 4b are provided, an electric field C is generated between the remaining exposed surfaces (outer surfaces) of each of the auxiliary shield members 5 and 5 and the corona discharge wire 2. The blowing out of the ion wind at the discharge opening portions closer to 3 and 4 is sufficiently promoted, and the above-mentioned original effect based on the arrangement of the auxiliary shield members 5 and 5 is fully exhibited.

In Fig. 4, a grid 11 (discharge current control member) is provided at the corona discharge opening, and the bottom of the shield member 1 is opened as a light guide window hole, and the light guide window side is made of glass or transparent resin. It is a cross-sectional view of an example of a scorotron-type discharge device in which a cover body 13 having a light-transmitting window portion 12 such as a plate is disposed, and the auxiliary shield member 5 is overlapped at the end at the same position as the grid 11. It may be provided.

According to the present invention, by ensuring a sufficient amount of ion wind is blown out at both ends of the corona discharger, it has become possible to suppress the rate of external foreign matter being taken into the shield member as much as possible. Furthermore, the effect of inducing corona at both ends prevents the amount of charge from decreasing at the ends of the discharger, making it possible to charge uniformly across the entire width of the corona discharger.

[Brief explanation of the drawing]

1 and 2 are a longitudinal side view and a cross-sectional view of an example of a corona discharge device to which the present invention is applicable, FIG. 3 is a longitudinal side view of an embodiment of the device of the present invention, and FIG. 4 is a scorotron type FIG. 2 is a cross-sectional view of an example of the device. 1... Shield member, 2... Corona discharge electrode, 3,
4... Insulating block, 5, 5... Auxiliary shield member, 3b, 4b... Insulating material coating.

Claims (1)

[Scope of Claims] 1. A corona discharge having an insulating block supporting a corona discharge electrode provided at both ends of a shield member, and a conductive member provided on the opening side (top surface) of this insulating block. A corona discharge device, wherein a voltage having a polarity opposite to that applied to the corona discharge electrode is applied to the conductive member, and an insulating member is provided at a portion of the conductive member facing the corona discharge electrode.