JPS6022134A - Potential control method of electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain an invariably stable electrostatic latent image and to stabilize the potential, specially, of an intermediate part by using a model potential corresponding to white paper and potentials corresponding to a pencil original and black paper for control over the quantity of electrostatic charging and a grid bias potential. CONSTITUTION:The brightness of light 24 is varied by varying the voltage to a blank exposure light source 16 before image exposure 16 to generate the potential V1 corresponding to 0.1 original density, potential V2 corresponding to 0.35 reflection density, and potential V3 corresponding to black paper. They are measured by a sensor 17 and compared by a control part 18 with a standard potential to be approximated thereto, and its control value is sent to primary and secondary high-voltage transformers 19 and 40 and a grid bias power source 23 to perform control. Then, such a potential between V1 and V2 that development is not performed with the potential V1 and carried out with the potential V2 is applied as a bias potential to a developing electrode. Thus, a general original is copied clearly without any fog all the time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a method for automatically controlling an electrostatic latent image on an electrophotographic photoreceptor of an electrophotographic apparatus to an optimum state.

(Prior art) In electrophotography, a normal latent image formation cycle is performed on a copy song, and at that time, a completely unexposed area (dark area potential) is formed on the photoreceptor.
A conventionally known method is to form a perfect 11-element part (bright part potential), detect these potentials with a potential sensor, and change the amount of band 14i after calculation so as to approach each standard potential.

However, in such a method, when the dark area potential and the bright area potential are controlled, various h light peaks (l!21. (
V1 curves are obtained and therefore 41 for each
Even if the M bias was changed, there was a problem in that the image in the middle part (gray part) would be different.

(Object of the Invention) The present invention provides a method for controlling a potential as described above.
The aim is to always obtain stable images. The purpose is to stabilize the potential in the middle of pencil manuscripts, etc., which are especially commonly used.
, o5~0.2) and a reflection density of 0.3~
0.5 and the dark potential or ordinary black paper (
This objective is achieved by controlling the potential corresponding to the reflection density (1.0 or more).

(Means for Solving the Problem) In order to achieve the above purpose, before starting copying, a model potential is set on the photoreceptor, which corresponds to a normal blank paper, and
A potential corresponding to a pencil manuscript, etc., and a potential corresponding to normal black paper in the completely unexposed area are formed, and each of these model potentials is detected by a potential sensor (7. The structure is such that process parameters such as the voltage and the grid bias voltage are controlled so that the potentials are equalized.

(Embodiment 1) The structure and operation of the present invention will be explained below with reference to the drawings. 2+J shows an embodiment of the structure of the electrophotographic apparatus of the present invention. A photosensitive drum 4 (FIG. 3 is a partially detailed explanatory diagram) consisting of a surface insulating layer 1, a photosensitive layer 2, and a conductive layer 3 was provided with a band 'C65 and grids 21 and 22 at the opening. An electrostatic latent image is formed by the secondary band and simultaneous image exposure unit 6 and the full-surface exposure lamp 7, and the developing unit 8 performs development with toner, and the C1 sheet is fed to the transfer charger 9. low 2
Transfer the toner image onto a transfer paper 11 sent by 10,
The toner image is discharged to the front side [2, 13] of the transfer paper by a fixing device 12 comprising a heating roller 2 and a pressure roller.

Further, the photosensitive drum 4, which has toner on its surface that has not been completely used for the transfer, is cleaned of residual toner by the cleaning device surface 14.

At the start of copying by the image exposure 15 +jiJ, the supply pressure to the blank fin flasher 16 is changed to change the brightness of the blank fog light 24, and the potential v1 corresponding to the original density 0.1 and the reflection density are changed. A 'upper v2' corresponding to o, a5 and a dark area potential (complete non-fog potential) V3 are formed. Thereafter, the surface potential sensor 17 provided after the entire surface exposure lamp 7 determines the model potential v.

Measure v2 and v3, send it to the performance section 18, and compare it with a predetermined standard potential.
'After calculating to get close to $7Ji, that fli!
1 direct current is sent to the primary and secondary image transformers 19 and 2 (+ grid bias voltage source 23), and the - order, secondary charge current and grid bias voltage are controlled by ttf!I.

measurement and control, predetermined times, or standard type b
This process is repeated until the difference from "L" falls within the specified range.

After that, the part of the potential vl is not tji11#,
The potential V applies a developing bias to the developing device 8 for developing. That is, a potential between potentials V and V2 is applied to the developing electrode as a bias voltage.

Each model potential set as described above ■1.

(2) The value of the developing bias is determined with respect to the target value of 2. There is no problem in fixing the bias value to that value. By doing this, ordinary originals can always be copied clearly without overlapping.

Note that if the background color of the original is dark, it is possible to prevent the background from being covered by making the exposure light 24 slightly darker relative to the potential v1. If the document is still extremely faint, use 24 blank fog lights for potential v2? Darker copies can be obtained by darkening the image.

To demonstrate this, we actually varied the supply voltage to the blank fog light pipe 16 to 20V, L5V, and 0V to obtain each model voltage vI and v2, respectively.

■3 and standard potentials tQV, 250V, respectively,
When the control was set to 450V and copies were made, it was possible to clearly copy originals that are generally difficult to reproduce, such as originals with light pencil writing and blue graph paper, even when various changes were made to the photoreceptor.

Note that this single-axis method can also be applied to the Carlson process.

(Other Embodiments) In addition to the above-mentioned embodiments, a white portion (original reflection density 0.05 to 0.2
A gray area (equivalent to 0.3 to 0.5 of reflective density), a black area (equivalent to reflection density 1.0 or more) are provided, and each model potential v is exposed by an original illumination lamp.

I am thinking of ways to form V, V3.

(Effects of the Invention) As explained above, the present invention uses a potential corresponding to a blank paper for hunting as a model, a potential corresponding to a lead gH manuscript, etc. By controlling the grid bias voltage using a potential corresponding to the charging potential, a stable electrostatic latent image can always be obtained even if the photoreceptor changes dramatically, especially in the middle part of a pencil manuscript, etc. This has the effect of stabilizing the potential of.

[Brief explanation of drawings]

FIG. 1 is an exposure acid (E+ vs. potential IVI sensitivity characteristic curve), FIG. 2 is a sectional view illustrating the configuration of an embodiment of the electrophotographic apparatus of the present invention, and FIG. 3 is a partially detailed explanatory view of a photosensitive drum. 4...Photosensitive drum 5...-Charger 6...Secondary charging simultaneous image exposure device 7...
...Full exposure lamp 8... Imager 9 ... Transfer charger 11 ... Transfer paper 16 ...・Blank exposure lamp 17...(Surface) potential cell 18...Calculation/control unit 21.22...Grid

Claims (1)

[Claims] In an electrophotographic device, before copying starts, model potentials are set on the photoreceptor: a potential corresponding to a normal blank paper, a potential corresponding to a pencil original, etc., and a potential corresponding to a completely unexposed area or a normal black paper. 1. A potential control method for an electrophotographic apparatus, characterized in that the model potentials are detected by a potential controller, and a process operator is controlled so that a predetermined standard potential is equal to the model potential.