JPS5956381A - Corona charger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona charging device that uniformly charges the surface of a photosensitive drum used in a dry electrostatic printing device or the like.

One of the printing processes of dry electrostatic printing equipment is the charging process.
This step uses a charging device called a colodron to charge the surface of the photoconductive drum to, for example, a positive electrode. The charging device generally consists of a corona discharge electrode, a shield case surrounding the electrode and having at least a discharge opening, and a power source that applies a corona generation voltage to the corona discharge electrode. In order to more evenly charge the surface of the photosensitive drum according to printing requirements, a configuration is adopted in which a grid electrode for controlling the amount of corona discharge is provided in the discharge opening of the shield case.

FIG. 1 schematically shows such a corona charging device with a grid electrode, in which 1 is a photosensitive drum, 2 is a shield case, 3 is a corona discharge electrode consisting of a plurality of linear electrodes,
4 is a grid electrode made up of a plurality of linear electrodes.

However, to explain in more detail, such conventional grid electrodes have a structure in which a plurality of metal wires with a wire diameter of 0.2 to 0.5 mm are arranged in parallel at intervals of 2 to 3 mm in the rotational direction of the photosensitive drum with constant tension. Therefore, it requires a large amount of man-hours (labor), time, and skill to assemble it, and the disadvantage is that during maintenance work such as cleaning due to adhesion of toner, etc., great care must be taken to prevent the wire electrode from being cut. was there.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional situation, it is an object of the present invention to provide a corona charging device with a grid electrode that can control the amount of corona discharge, is inexpensive to manufacture, and is easy to handle.

Briefly stated, the present invention has a configuration in which a grid electrode for controlling the amount of corona discharge is provided between a photosensitive drum and a corona discharge electrode, and the grid electrode is attached to and detached from a discharge opening of a shield case provided to surround the corona discharge electrode. freely set up,
and a frame plate having a curved plate surface along the surface of the photosensitive drum with an open portion facing the corona discharge electrode, and at least the corona having an arc-shaped plate surface fixed to the frame plate and extending along the surface of the photosensitive drum. The present invention is characterized in that it includes a metal mesoche plate whose portion facing the discharge electrode is formed into a mesoche, and the metal mesoche plate is clamped at a predetermined potential to act as a grid electrode.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to FIGS. 2 and 3.

Note that the same parts as in FIG. 1 are given the same reference numerals. FIG. 2 shows a perspective view for explaining the overall configuration of the corona charging device according to the embodiment of the present invention, excluding the power supply section. In the figure, 1 is a photosensitive drum, 2 is a shield case, 3 is a corona discharge electrode, and 5 is a frame plate, and 6 is a metal mesh plate.

As shown in FIG. 3(A), the frame plate 5 is formed by molding a stainless steel plate with a thickness of 2 mm into a substantially U shape, and the plate surface 51 facing the discharge opening of the shield case 2 is formed on the surface of the photosensitive drum 1. It has an arcuate shape curved along the surface, and is open at a portion facing the corona discharge electrode 3. The frame plate 5 molded in this manner has both side pieces 51 and 52 bent upwardly fixed to both side walls of the shield case 2 by screws, for example. Reference numeral 53 indicates a hole for screw attachment. On the other hand, the metal mesh plate 6 has a thickness, for example, as shown in FIG. 3(B).
A 0.3mm thin metal plate (for example, a stainless steel plate),
For example, a portion of the frame plate 5 facing the opening 54 has a thickness of 3 mm.
After etching the four-fold mesoduro 1, it is curved and molded along the surface of the photosensitive drum 1.

The non-mesh portion 62 of the metal mesh plate 6 thus formed is made to match the edge 55 of the frame plate 5, and then spot welded at the locations indicated by X marks to integrate them. In addition, if this spot welding work is carried out with the metal mesh plate 6 under tension, the mesh part 61 can be tightly fixed to the frame plate 5 while suppressing the tendency of the mesh part 61 to sag due to the bending process. It is possible to maintain a gap with a certain precision. Specifically, after welding one side (on the right side of the paper), when welding the other side, eccentric pins (not shown) are inserted into the holes 56 of the frame plate 5 and the elongated holes 63 of the metal mesh plate 6. Apply tension in the direction of the arrow.

The thus integrated frame plate 5 and metal mesh plate 6 are assembled by fixing the frame plate to the shield case 2 with screws as described above, and connecting the metal mesh plate 6 to a grid voltage source (not shown). This is used as a grid electrode.

As is clear from the above description, in the corona charging device of the present invention, the grid electrode is constructed of a metal mesh plate, and the metal mesh plate is integrated with a rigid frame plate and attached to a shield case. Therefore, the grid electrode structure is simple and inexpensive, and when cleaning adhered toner, etc., the frame plate can be removed and cleaned easily, and there is no risk of deforming the frame plate and deforming the metal mesh plate when the frame plate is attached or removed. Therefore, it is compatible as a charger unit and is advantageous in terms of maintenance, so it is extremely useful when applied to a dry electrostatic printing device. Although it is conceivable to directly fix the metal mesh plate to the shield case, this deforms the mesh plate when it is fixed, making it difficult to maintain a predetermined gap with the photosensitive drum.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventional corona charging device with a grid electrode, FIG. 2 is a perspective view for explaining one embodiment of the corona charging device according to the present invention, and FIGS. B) is an enlarged perspective view showing the frame plate and metal mesh plate of FIG. 2; 1: Photosensitive drum, 2: Shield case, 3: Corona discharge electrode, 4 Nigerid electrode, 5: Frame plate. 6: Metal mesh plate. Figure 1

Claims (1)

[Claims] In a configuration in which a grid electrode for controlling the amount of corona discharge is provided between a photosensitive drum and a corona discharge electrode, the grid electrode is detachably provided in a discharge opening of a shield case provided to surround the corona discharge electrode, and a frame plate having a curved plate surface along the surface of the drum and having an open portion facing the corona discharge electrode; and at least the corona discharge electrode fixed to the frame plate and having an arcuate plate surface extending along the surface of the photosensitive drum. 1. A corona charging device comprising a metal mesh plate whose opposing portions are formed into a mesh, and the metal mesh plate is clamped at a predetermined potential to act as a grid electrode.