JPH0453650Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a scorotron charging device having a screen grid. This type of charging device is used in electrophotographic devices.

(Conventional technology) As a conventional scorotron charger grid, (1) Multiple wires stretched in parallel.

(2) A grid pattern is formed on a thin metal plate by etching, etc., and has a constant aperture ratio in the direction of movement of the photoreceptor.

has become publicly known.

However, in the case of (1), (a) Poor assembly.

(b) Due to poor charging efficiency (discharging efficiency), the width of the charger in the direction of movement of the photoreceptor is required.

(c) Potential control is poor and uneven charging tends to occur.

(d) Poor compatibility with high process and linear speeds.

There was a drawback.

In the case of (2), although the charging efficiency is somewhat superior to the case of (1), it is still far from being sufficient, and there are disadvantages in that it is not compatible with high process linear speeds.

Therefore, the same applicant has already improved the grid pattern shape, pattern arrangement direction, grid tension form, etc. in the screen grid of the scorotron charger used in the electrophotographic process, and has developed a charger that eliminates the drawbacks of the prior art. However, the positional relationship between the charging wire and the grid pattern in the direction of movement of the photoreceptor was not clearly disclosed.

(Purpose) The present invention was made based on such a background, and an object thereof is to provide a scorotron charger with excellent charging efficiency and potential control performance.

(Structure) In order to achieve this objective, the present invention considers the positional relationship between the wire and the grid pattern directly below the charging wire.

In other words, the grid lattice directly below the charging wire is located approximately at the midpoint of the grid sides parallel to the direction of movement of the photoreceptor.

Hereinafter, the configuration of the present invention will be explained based on an illustrated embodiment.

FIG. 1 is a schematic diagram showing the area around a photoreceptor, which is an electrophotographic process part, in an electrophotographic apparatus to which a scorotron charging device according to the present invention is applied.

In the figure, 1 is a photosensitive drum, 2 is a scorotron charging device, 3 is an imaging light beam, 4 is an eraser, and 5
is a pre-transfer exposure LED, 6 is a registration roller, 7 is a transfer charger, 8 is a separation charger, 9 is a separation claw, 10 is a conveyor belt, 11 is a toner collection shaft, 12 is a cleaning blade, 13 is for static elimination
LED, 14 is a waste toner bottle. Note that a developing device is not shown.

In such equipment, the electrophotographic process is
Charging, image exposure, development, pre-transfer exposure, transfer, separation,
Cleaning and static electricity removal are performed in this order.

FIG. 2 is a front sectional view of the charging device according to the present invention.

The grid pattern of the screen grid 18 is a regular hexagonal pattern and is stretched in parallel along the radius of curvature R of the photoreceptor 1 at intervals of dR. In the present invention, as described above, the problem is the positional relationship between the wire 15 and the grid pattern in the section A directly below the charging wire 15. This will be described later based on FIG.

The grid holder 17 is a part of a thin metal plate bent into an L shape and fixed to the case 16 by welding or caulking.The grid 18 is held by the end face of the case 16 and the bent part of the grid holder 17, and the grid 18 and case 16 are electrically connected. Although this is not directly related to the gist of the present invention, by grounding the grid 18 and the case 16 through a common constant voltage element (varistor) in this way, the case 16 is grounded. The charging efficiency of the photoreceptor is improved.

FIG. 3 is a plan view of the charging device according to the present invention.

The charging wire 15 has one end fixed to an end block 19 made of an insulating resin material, and the other end fixed via a spring 20 to a connection tab 22 to a power source. (Tab 22 is the end block 21
(fixed within). In this manner, the charging wire 15 is tensioned with a constant tension applied by the action of the spring 20. Further, a part of the case 16 protrudes to serve as a connection tab 23 to the constant voltage element. As can be seen from FIG. 3, the positional relationship between the charging wire 15 and the grid pattern at part A directly below the charging wire 15 is within the grid side of the grid pattern parallel to the photoreceptor moving direction (x direction). A feature of the present invention is that the charging wire is placed at a position passing through the point.

4a and 4b are enlarged plan views showing the positional relationship between the charging wire 15 and the grid pattern;
3 is a diagram showing the positional relationship in the present invention shown in FIG. 3, and b is a diagram showing the positional relationship in a state where the wire 15 is deviated from the midpoint of the grid side of the grid pattern.

FIG. 5 shows coordinate axes extending in the direction of movement of the photoreceptor with the position of the charging wire 15 as a reference.
FIG. 3 is a diagram showing the state of change in the aperture ratio ρ (%) of the grid pattern in a direction perpendicular to the photoconductor moving direction as viewed at a distance x from the photoreceptor. In the figure, the solid line indicates the state in FIG. 4a, and the dashed-dotted line indicates the state in FIG. 4b. Symbol in the figure, L is the length of one side of the pattern grid, dL
is the pattern width.

As is clear from the figure, in the case of FIG. 4b, when the position of the charging wire 15 is shifted in the x direction, the change in the aperture ratio ρ occurs from the point L/4; In the case of FIG. a, the margin for displacement of the charging wire 15 in the x direction is doubled.

In addition to the above-mentioned problem of aperture ratio, in addition to the ease with which the wire discharge point moves during cathode discharge, having a diagonal part of the grid pattern directly below the wire is important for the wire during discharge. Discharge points tend to shift due to misalignment with the pattern due to vibration, and the potential controllability and discharge efficiency are close to conventional examples, making it possible to take full advantage of the characteristics of the grid pattern shape, which is the premise of this invention. It becomes something that does not exist.

However, in the present invention, this problem is solved by establishing the positional relationship between the two as shown in FIG. 4a.

X between the charged wire and the grid in actual use
The positional relationship in the direction may vary slightly due to the accumulation of dimensional tolerances of the installed parts.
Furthermore, the wire in the discharge state repeats minute vibrations, and from this point of view as well, the positional relationship as shown in FIG. 4a is ideal for absorbing variations. The screen grid 18 is a thin metal plate manufactured by etching or electroforming.

(Effects) The present invention is as described above, and according to the scorotron charging device according to the present invention, charging efficiency and potential control performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the drum and surroundings of an electrophotographic apparatus to which the charging device according to the present invention is applied, FIG. 2 is an enlarged view of the charging device section, and FIG. 3 is a plan view of the charging device according to the present invention. Figures 4a and 4b are enlarged plan views showing the positional relationship between the wire and the grid pattern, where a is a view showing the positional relationship according to the present invention, b is a view showing a different positional relationship, and Figure 5. is the fourth
FIG. 6 is a diagram showing how the aperture ratio of the grid pattern in FIGS. 1... Photosensitive drum, 15... Charging wire,
18...Screen grid.

Claims (1)

[Scope of utility model registration request] The aperture pattern of the plate-shaped grid provided in the charger provided facing the surface of the photoreceptor is formed by a large number of regular hexagonal microholes so as to have an isodirectional aperture ratio. There are 6 patterns
Two of the sides are formed in a direction parallel to the rotational direction of the photoreceptor, and the charging wire stretched across the charger is located above the approximate midpoint of the two sides parallel to the rotational direction of the photoreceptor. A scorotron charging device characterized by being located at.