JPS58139161A - Electrifier - Google Patents

Abstract

PURPOSE:To charge a photoreceptor to a stable potential for a long time, by providing a grid electrode between a corona electrode and the photoreceptor and connecting a variable resistor and a constant voltage passive element in series to the grid electrode and grounding the constant voltage passive element. CONSTITUTION:A corona electrode 4 connected to a DC high voltage source 3 is provided in a conductive shield 1 provided for a photoreceptor 2. A grid electrode 5 is provided between the corona electrode 4 and the photoreceptor 2, and a variable resistor 6 and a constant voltage passive element 7 are connected directly to the electrode 5, and the element 7 is grounded. When the bias voltage of the grid electrode 5, the constant voltage value of th passive element 7, the voltage generated in the resistor 6, and th voltage accumulated on the surface of the grid electrode are denoted as Vg, Vt, Vr, and Vm respectively, expression is true. The voltage Vm rises in accordance with the number of times of corona discharge, and the resistance value of the variable resistor 6 is adjusted in accordance with this rise to obtain the always constant bias Vg, thereby obtaining a stable image for a long time.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a scorotron type charging device, which is a type that has been widely used in the past as a scorotron type charging device. There is a so-called corotron that is charged by ion discharge. Although this corotron has the advantage of being simple and inexpensive, it lacks stable and uniform charging performance. In other words, the corotron is no longer able to reproduce higher-quality images and satisfy the imaging conditions required by the hardware.

2 For this reason, a grid electrode is provided between the corona electrode and the photoreceptor, and a high voltage is applied to the corona electrode, and a DC bias voltage is applied to the grid electrode.

It is conceivable to use a scorotron that is charged by This type of scorotron has the advantage that the charging potential can be set approximately equal to the potential applied to the grid-poles, and as a result, it can be uniformly charged to any potential. Of course, in this case, a transformer for applying a DC bias voltage is required, which makes the structure larger and more expensive. Therefore, as shown in Japanese Patent Publication No. 51-17419, if a constant voltage passive element functioning as a self-bias voltage applying means is connected to the grid electrode and the constant voltage value of the constant voltage element is set constant, the above-mentioned result can be achieved. 0 and F4 can be uniformly charged to a potential approximately equal to the constant voltage value without the need for a transformer. A film is formed, and corona discharge charges are trapped in this insulating film, causing the effective bias voltage value of the grid electrode to change, and as a result, the charged potential also changes. In other words, the grid electrode can be charged to a predetermined potential at the initial stage of use, but the potential gradually fluctuates, causing a change in image quality.

"mouth LΩ" mouth play This invention was made in view of the above-mentioned drawbacks, and its purpose is to provide device R' with WI', which can be charged to a constant potential without fluctuation over a long period of time. The goal is to provide fc.

Embodiment FIG. 1 shows a schematic configuration of a scorotron charging device according to the present invention, in which (1) is a conductive shield provided with its opening facing the photoreceptor (2), in which a high DC A corona electrode (4) connected to a voltage source (3) is provided. A grid electrode (5) is provided between the corona electrode (4) and the photoreceptor (2), and the grid electrode (5) is equipped with a variable resistor (6) and a constant voltage passive element (7) such as ZNH. A constant voltage passive element (7) is connected in series and grounded. In other words, the grid electrode (5) and the photoreceptor (2
) between the electrodes of the variable resistor (6) and constant voltage passive element (7)
are connected in series. Note that the shield (1) may be made of a dielectric material.

As the grid electrode (5), for example, Utility Model Application No. 54-102
A mesh-like structure as shown in Publication No. 40, or a structure in which a large number of wires (8) are stretched in parallel at fine intervals and supported by a frame (9) as shown in Fig. 2. can be used. Note that the wire (8) is attached to the photoreceptor 1 (
2) It is desirable to install it in an inclined manner in the direction of movement. Also,
As the constant voltage passive element (7), not only ZNH but also a constant voltage diode, a constant voltage discharge tube, etc. can be used.

Due to the operation of the charging and device with the above configuration, a variable resistor (6
).
1. Fluctuations in the charged potential will be described when the constant voltage passive element (7) is directly connected to the grid electrode (5) without the variable resistor (6). An unused grid electrode (5) 1 was placed at a distance of 1 mm from the surface of the photoreceptor, and was charged to a surface potential of 600 V at a constant voltage. This means that the surface potential can be controlled to be approximately equal to the value of the gold constant voltage passive element with no charge. When the surface potential was measured by repeating the above charging 30,000 times under the same conditions, a predetermined potential of 600V was obtained for the first 10,000 times, but after that, it gradually increased to 50V after 30,000 times. It increases to 670V. This is because an insulating film is formed on the surface of the grid electrode (5) by ion discharge, and the discharge charge is gradually trapped in this insulating film, causing an increase in potential.0Here, the grid electrode (5) is a new one. When replaced with , the surface potential becomes the predetermined 600V again, and a problem arises in that the potential rises even more when used repeatedly.

As a result, the grid electrode must be replaced frequently to maintain a predetermined surface potential.

In contrast, the present invention attempts to always guarantee a constant surface potential by connecting a variable resistor (6) in series with a constant voltage passive element (7) as shown in FIG. . In other words, in the present invention, the constant voltage passive element (7
) with a constant voltage value lower than the predetermined surface potential, and the voltage difference between the surface potential and the constant voltage value is measured using a variable resistor (61
This is compensated by the voltage generated in the In other words, the bias voltage (charged surface potential) iVg applied to the grid (5) IC.

The constant voltage value of the constant voltage passive element (7) is set by the vt1 variable resistor (
6), the voltage applied to Vr, and the grid electrode (5)
The following equation holds true when the voltage accumulated on the surface of is Vm.

Vg = Vt + Vr + Vm Here, as can be understood from the above, Vm is equal to ttovic at the beginning of use of the grid electrode (5) and is a variable resistance '
4 (6) The resistance value is adjusted so that the voltage Vr generated therein compensates for the difference between the predetermined surface potential Vg and the constant voltage t. In other words, adjust the resistance value so that Vg=Vr+Vt.
The resistance value of the variable resistor (6) is adjusted so that a voltage of 100 V is generated when Vr is 500 V and Vr is 500 V. However, Vm gradually increases as the grid electrode (5) is repeatedly exposed to corona radiation. Therefore, in the present invention, a variable resistor (6
), the resistance value is adjusted to change Vri so that a constant Vg is always obtained. In other words, in the above formula, Vt
Adjust VrtNi2 accordingly. For example, Vm is 7
If it becomes 0V, connect the variable resistor (6) so that vr becomes 30V.
) to ensure that Vg is 600V, the same as when Vm=OV.

The resistance value of the variable resistor (6) can be determined by, for example, measuring the surface potential of the photoreceptor with a probe and comparing it with a predetermined surface potential [
7. It is only necessary to adjust so that the voltage value equal to the phase difference is corrected by Vr. In this case, Vr is of course corrected according to the voltage Vm VC accumulated on the grid electrode, but also changes in the surface potential due to fatigue of the photoreceptor, and furthermore, the constant voltage of the constant voltage passive element (7) This is effective because it also deals with variations in values. Incidentally, the surface potential may be measured every copy or every fixed number of copies. In addition, you may periodically monitor changes in image density and adjust the resistance value of the variable resistor (6) accordingly. The resistance value of the variable resistor (6) may be adjusted to the grid electrode (5). The flowing corona current and the Vr voltage 11M in the range you want to correct,
It can be determined based on vr. For example, when the current flowing through the grid electrode is 200 μA, the voltage Vr generated in the resistor
If it is desired to make the voltage variable within the range of IO to 100V, a variable resistor (6) with a resistance of 0 to 500 Ω may be used. The relationship between the constant voltage value Vt of the constant voltage passive element (7) and the voltage Vr generated in the variable resistor (6) is set so that Vt is 70% or more of Vg and Vr compensates for the remainder. It is desirable to do so. This is because the corona current fluctuates due to changes in environmental conditions, etc., and if the Vr compensation range is too large, it will not be able to cope with it.
Set @vc at a distance of m, set VT to 500 V,
The charging potential Vgt was measured by applying a DC voltage of 6KV to the corona electrode with Vr as 0 < Vr < 100 V.According to this, in the first approximately 10,000 cycles≠4, as long as Vrl is 100V, the charging potential is Approximately 600V, the sum of Vt and Vt, was measured, but after that, the resistance value of the variable resistor (6) was changed so that Vr would be 70V when the O charging level, which gradually increased, was 630V.
The potential was again corrected to a predetermined value close to 600 VK.

Charged type.

When Vrt was corrected in accordance with the rise in potential, the ideal potential was approximately 600 cm in all cases.

! ! As is clear from the above description, the charging device i# according to the present invention can always charge the surface to a potential equal to the ideal surface potential, and can produce stable images over a long period of 1 km. Furthermore, the configuration and control are simple, and the grid electrode does not need to be replaced frequently, so it has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a charging device according to the present invention, and FIG. 2 is a diagram showing an example of the configuration of a grid electrode. (1)... Conductive shield, (4)... Corona electrode. (5)...grid electrode, (6)...variable resistor. (7)...Constant voltage passive element〇Applicant: Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A corona electrode connected to a high voltage source, a grid electrode between the corona electrode and the photoreceptor, and a variable resistor and a constant voltage passive element connected in series to the grid electrode. A charging device characterized in that the constant voltage passive element is grounded. 2. The voltage applied to the grid electrode is vg. When the constant voltage value of the constant voltage passive element is Vt, the voltage generated in the variable resistor is Vrs, and the voltage accumulated on the surface of the grid electrode is Vm, the formula Vg = Vt + Vr + Vm is established, and VrHVm is 2. The charging device according to claim 1, wherein the charging device is corrected according to fluctuations.