JPS6188282A - Scorotron electrostatic charger - Google Patents

Abstract

PURPOSE:To obtain the practically uniform aperture rate of a plate type grid between a corona wire and a photosensitive body even when the grid is curved and to perform uniform electrostatic charging by determining the aperture rate by a predetermined function. CONSTITUTION:Apertures bored in the plate type grid 3 are small in area at the center part in a plane perpendicular to its lengthwise direction and larger toward both sides to increase the aperture rate from the center part to both sides. The substantial aperture width d2 at distance l from the center of grid is d1cos(90 deg.-thetal), where d1 is the aperture width of the grid right under the corona wire, so the substantial aperture rate is equalized by letting d1cos(90 deg.-thetal) (90 deg.-thetal) is the angle of a cutting line in a curved surface at a point D2 to a horizontal surface).

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a charger for a photoreceptor in an electrophotographic copying machine or the like, and particularly to a technique for a scorotron charger.

It is common knowledge that a scorotron charger is used as a type of charger for a photoreceptor provided in a prior art electrophotographic copying machine or the like. ) Said scorotron j1″r electric R: ; is open facing the photoreceptor as shown in FIG. At least one corona wire 1 is stretched at the center of the inside of the casing 2 having a U-shaped cross section.
A grid 3 in the form of a plate with a large number of windows perforated in a flat plate is used, connecting the opposing casing edges so as to block the gap between the casing and the surface of the photoreceptor. Third (b)
Figure) E is a perspective view of the above-mentioned plate-like grid 3, in which the windows (openings) provided therein are arranged at equal intervals both in the vertical and horizontal directions, forming an overall uniform opening pattern. There is.

By the way, if the surface of the photoreceptor is curved, the gap between the charger and the photoreceptor can be narrowed and the gap can be made even.
It is necessary to take a bath and remove it [No. 4]
In this grid section 3 between the corona wire 1 and the vicinity of the end of the cage 2, the angle at which the opening at that location is viewed from the wire 1 is different.
Please refer to FIG. 4(b) for the state. ] As a result, the aperture ratio of the plate-shaped grid 3 relative to the photoreceptor decreases near the side of the casing, and as a result, the charged area becomes substantially narrower. This phenomenon occurs even if the plate-shaped grid is a flat plate.
This problem becomes particularly serious when the photoreceptor drum has a small radius and the plate-like grid is curved by bending the surface of the grid.

Purpose Therefore, the object of the present invention is to ensure that even when a curved plate grid is used in a conventionally used scorotron charger, both the grid immediately below the corona wire and the grid near the caning are substantially the same when viewed from the wire. An object of the present invention is to provide a charger in which a plate-like grid is formed so as to have an opening pattern, and its charging area is expanded in practice.

(1) There is a plate-shaped ′i between the corona wire and the photoreceptor.
In the charger equipped with a 4+-h grid, the plate-shaped grid has an aperture ratio of the grid based on the opened open Ropacoon that differs depending on the location, and the relationship therebetween is determined by a predetermined function. An aperture pattern like l
1. A scorotron charger characterized by comprising a plate-shaped grid with 1.

(2) In a scorotron charger in which a plate-shaped auxiliary grid is curved and used as a photoconductor, the aperture ratio of the aperture pattern of the plate-shaped grid should match the direction of movement of the photoconductor and be close to the surface of the photoconductor. In the cross section taken by orthogonal planes, the grid is curved as seen from the corona wire, with the minimum at the location closest to the corona wire, and the distance from the corona wire increasing (therefore, the grid is gradually increased at that location). The scorotron charger 3 according to the above item 111), in which the substantial aperture ratio of the grid is made uniform or nearly uniform over the entire surface of the plate grid even when Explain that it is a lodging.

Embodiment FIG. 1 shows a perspective view of an embodiment of a plate-shaped grid 3 of a scorotron charger according to the present invention. υ; 40 area is narrowed, and both sides [1111;?: The opening area is expanded sequentially as it gets closer. In other words, the opening ratio is increased from the center to both sides (as it goes from ・) to next. In other words, Fig. In the middle, "uneven spacing" is indicated in the direction of the arrow 1.However, in the longitudinal axis direction of the plate grid, their aperture ratio is uniform, which is indicated by "equal spacing" in the direction of the longitudinal arrow. Displayed.

The above-described apertures with uneven intervals are reduced in size according to what rule. This point will be explained with reference to FIG. 2 below. In FIG. 2, 3 is a plate-like grid of P m3, which is curved at 6 around the circumference of radius R with O as the center. Although not shown, if the opening width of the grid directly below the corona wire is dll, and the effective opening width of the grid at location j1b, which is located a distance t from the center of the grid, is dl, then the distance n from the grid center point Dr is t. When the angle of cut on the curved surface at point D2 on the grid is defined as a horizontal plane (90°-θt), d2= d
+ cos (90°−θt) ・=−・・・= (
1) However, dl>dl, θtz9o.

Therefore, in order to correct this, when the grid 3 is curved with a radius of R and a circumference of KG,
The size dl of the aperture pattern of the plate-like grid located t away from the grid center D1 is d+ = d+ / cas
(90°-θt) (2), the actual aperture ratios will be the same. (Strictly speaking, the corona wire is not at an infinite distance, and the surface of the photoreceptor is curved, so even if the aperture ratio is set according to the above formula, it will not be exactly uniform, but in practice, It can be interpreted as almost identical, l
) Therefore, once R and t are determined, θ
t is calculated, and by substituting this into equation (2), t: the size of d1' to be cut, the numerical value of t and dl calculated by the tip of the sword whose opening back-/ is greater than or equal to Denru. (
(If the aperture pattern of the plate-like grid is shaped based on the shape, even when the plate grid is curved, a uniform aperture ratio can be obtained in practice, a substantial expansion of the charging area can be achieved, and even highly uniform charging can be achieved.) will be held.

Effects As described above, by forming the open lobe turf of the plate-like grid in accordance with the ratio determined based on the predetermined barrier, the plate-like grid is narrowed in the center and widened as it approaches both side edges. Even when a cylinder with a radius of , it is possible to perform charging with good uniformity.

11. r, fl ``li explanation of drawings Fig. 1 is a perspective view showing the developed scorotron charger of the present invention. )Number: Model diagram for calculating the aperture ratio of 1-reverse grid glue Hiro pattern on 7-grid which is 5 materials, 3rd (a), +b+
Figure 4(a) is a sectional view taken along a plane perpendicular to the longitudinal direction of a conventionally used scorotron charger, and an oblique view of its plate-like grid, and Figure 4(b) is FIG. 7 is a diagram showing that the aperture pattern of a conventional plate-like grid becomes substantially non-uniform in aperture ratio with respect to a photoreceptor when the grid is arranged in a curved manner.

l... Corona wire, 2... Charger case, 3...
plate grid.

Claims (1)

[Claims] 1. In a charger in which a plate-shaped auxiliary grid is provided between a corona wire and a photoreceptor, the plate-shaped grid has an aperture ratio that varies depending on the location based on the opened aperture pattern. A scorotron charger characterized in that it consists of a plate-like grid with an aperture pattern whose relationship is determined by a predetermined function. 2. In a scorotron charger that uses a plate-shaped auxiliary grid curved along the photoconductor, the aperture ratio of the aperture pattern of the plate-shaped grid matches the moving direction of the photoconductor,
In addition, within a cross section taken by a plane perpendicular to the surface, the value is the minimum at the part closest to the corona wire, and as the distance from the corona wire increases, the value is gradually increased at that location, and the value is changed as seen from the corona wire. 2. The scorotron charger according to claim 1, wherein the substantial aperture ratio of the grid is uniform or nearly uniform over the entire surface of the plate grid even when the grid is curved.