JPS6022135A - Potential control method of electrophotographic device - Google Patents

Abstract

PURPOSE:To take a copy of character patterns even on a low-contrast original clearly and to prevent a photosensitive body from deteriorating by varying a standard potential according to the texture of an original and the contrast of the image density of character patterns. CONSTITUTION:The standard white plate 22 of a platen 21 is exposed to a lamp 23 to form a white part potential V3 on a photosensitive drum 4 by exposure 15, and the potential is measured by a sensor 17, sent to a control part 18, where it is compared with the predetermined standard potential for a high-contrast original and so processed as to approximate thereto, thereby sending a control value to an original lamp power source 24 to be controlled. Then, the controlled amount of electrostatic charging and the amount of exposure are used to an electrostatic latent image of the original and its surface potential is measured by the sensor 17, and sent to the control part 18 to calculate its mean surface potential; when the value is within the estimated range of the expected high- contrast original, the operation is carried out as it is. When it is within said estimated range, the standard potential is switched to a potential for low contrast and the control is carried out again to take a copy.

Description

Detailed Description of the Invention (Field of Industrial Use) The present invention provides six electrostatic latent images on a photoreceptor in an electrophotographic device.
The present invention relates to a method for automatically controlling to an optimum state according to the contrast between the background of a document to be copied and the image density of a character pattern.

(Prior art) Electrostatic latent images formed by electrophotography generally suffer from C due to various conditions such as environmental changes, deterioration of the photoreceptor, and long periods of rest.
To avoid instability, a model potential is formed on the photoreceptor before copying, this model potential is detected by a potential sensor, and charging 111 and exposure are performed so that the model potential becomes equal to a predetermined standard potential. Methods for controlling the amount etc. are known.

However, with this method, when determining the standard potential, it is necessary to ensure that the character pattern is clear even on originals with low contrast between the background of the original and the image density of the character patterns, such as thin originals or color printed originals. It is necessary to take into account the copying conditions and the second layer to reduce charging deterioration of the photoreceptor. 1. An electrophotographic device that forms an electrostatic latent image by simultaneous secondary charging image Dx light and full DLR exposure (6: In model potential, dark area potential (complete non-light 4) and bright area potential (fully exposed area) In order to clearly copy the character pattern of a low-contrast original, it is necessary to increase the magnetic potential difference between the dark potential and the bright potential. This causes the problem of increased secondary charging and accelerated deterioration of the photoconductor, so in determining the standard type 1σ, it is necessary to satisfy several conflicting conditions, which is difficult. The problem was that it was often accompanied by

(Object of the Invention) The present invention aims to copy the pattern of a low-contrast original in an electrophotographic method such as AiJ, and to reduce the deterioration of the photoreceptor. The contrast lr of the original to be printed and the surface potential of the electrostatic latent image are detected and discriminated, and when the contrast is low, the potential difference between the standard potentials is increased, and when the contrast is high, the potential difference between the standard potentials is decreased. This aims to achieve the above objectives.

Figure 1 shows the relationship between each type of Minoru Sawahara and the average surface potential of its electrostatic latent image. , colored paper printing, etc. can be distinguished from the average surface potential.

(Means for Solving the Problem) In order to achieve the above object, the present invention detects and discriminates the contrast between the background and character pattern images (& density) of a document to be copied as the surface potential of an electrostatic latent image. , a standard potential corresponding to the contrast of the original is used according to a predetermined method.

(Example) Below, the configuration and operation of the present invention will be explained based on one example. FIG. 2 shows an embodiment of the configuration of an electrophotographic apparatus according to the present invention. Table ■ Loquat layer 1. A photosensitive drum consisting of a photosensitive layer 2 and a conductive layer 3 (FIG. 3 is a partially detailed explanatory diagram)
Then, a static foil image is formed by the -forming charger 5, the secondary belt simultaneous image exposure device 6, and the full-scale original lamp 7, the developing device 8 performs toner IW, and the transfer charger 9 supplies the image. The toner image is transferred onto a transfer paper 11 sent by a paper roller 10, and then pre-processed by a preservative device 12 consisting of a heating and pressure roller.
The self-toner image is fixed on the transfer paper and the paper is discharged to 13. Further, the photosensitive drum 4, which carries the toner that has not been used for transfer, is removed from the surface by the cleaning device edge 14 to remove the remaining toner.

When the copy start key is pressed, the latent image forming process is started, and the blank exposure lamp 16 is turned on to irradiate the drum, forming a bright area potential v1 on the drum. By turning off the light, a dark area B'L V 2 is formed on the drum. After that, the surface potential sensor 17 installed after the full-surface non-light lamp 7
Then, the bright area potential V and the dark area potential v2 are added together and sent to S18, and compared with a predetermined standard potential for high contrast cooling. After calculation is made to approximate the potential, the control value is sent to the high-voltage transformers 19 and 20, and the secondary and secondary charging currents 1- are controlled.

At the same time, the original reflection density 0 provided in the non-original part of the original platen 21
．． A standard white plate 22 equivalent to 0.05~0.2 is illuminated by the original illumination lamp 23, and the exposure 15 causes the photosensitive drum 4 to
A white part potential v3 is formed on the top, measured by the potential sensor 17, and sent to the calculation, control, and storage unit 18, and is softened in comparison with a predetermined standard potential for high-contrast originals so that it approaches this standard potential. After the calculation, the control value is sent to the original lamp power supply 24 to control the original illumination voltage. Next, a static latent image of the CIS manuscript is formed using this controlled charge amount and exposure amount, and the multifaceted potentials are added together with the potential length 17.
Calculation, control 1, the average surface potential of the electrostatic latent image of the document is calculated, and if the value is within a predetermined range assuming a high-contrast document, it is processed as is. Copying is performed using the charger and the exposure amount, and if it is within a predetermined range assuming a low-contrast original, the standard potential is switched to low-contrast and the above-mentioned control is re-performed before copying is performed.

In order to demonstrate this, we actually measured the standard potentials of the bright and dark areas, and in the case of contrast originals, the deviation ('t
1. -100 V, 350 V! *For low-contrast originals, set the standard potential to -150VI and 600V, respectively. In both cases, perform Ov and -C control for the standard potential of the white part. When the average potential is in the range of 60 to 250v, set it to 55V for high-contrast originals. Below or 255V
In the above cases, copying was performed while distinguishing from low-contrast originals.

Also, for comparison, bright and dark areas are compared using conventional standards.

Each standard potential of the white part potential is -L50V.

C copy was performed at 450V and OV.

First, as for M of a low-contrast original, in the case of an erudite manuscript with character reflection aV: 0.3, in the conventional example, it was copied with a reflection # of 0.5, whereas in the present invention, it was copied with a reflection # of 0.5.
．． Copies were made with a reflection density of 85, and clear copies were obtained even with low contrast originals.

Next, after copying 50,000 sheets, the photosensitive drum 4 was left in front of all the electronic photographs, and after an hour's rest, 100,000 copies were made.
When 0 copies were made continuously and the dark area potential of the 1st and 100th copies was determined, it was 40V in the present invention, whereas it was 70V in the conventional example, which actually shows that there is less charging deterioration of the photoreceptor. Confirmed.

Incidentally, the present application can be applied to the Carlsyn process and the NP process.

(Other Embodiments) In addition to the first embodiment, although not particularly shown in the drawings, control is performed in advance for the standard potentials of high-contrast IfA use and low-contrast original use, and Down 1
Memorize the Teijaku wax and photoresistance C, then detect and discriminate the contrast of the original to be copied under the latent image conditions for high contrast originals, and if the original has high contrast, use the same latent image condition. 14=, if the contrast is low, it is possible to switch to the memorized latent image conditions for low contrast and copy, and the so-called first copy time is 1 hour by the time that no control is performed after detecting the contrast of the original. (The time it takes for the original image to be copied onto the first sheet of transfer paper after the copy start key is pressed and the original image to be printed on the JJF paper) can be completely shortened.

In addition, automatic exposure is also possible by adding the appropriate exposure voltage of the document illumination lamp according to a predetermined calculation formula based on the average surface potential of the static image of the document and controlling the document illumination lamp electric wire. It is also possible to do so.

(Effects of the Invention) As explained above, in the present invention, character patterns of low-contrast originals can be clearly copied by changing the standard value depending on the contrast between the background of the original to be copied and the image density of the character pattern. In addition to this, it also has the effect of reducing deterioration of the photoreceptor.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the zelkovas of each suzuhara-oke and the average surface potential of its electrostatic latent image. FIG. FIG. 3 is a partially detailed explanatory diagram of the photosensitive drum. 4...Photosensitive drum 5...-Charger 6...Secondary charging simultaneous image exposure device 7...
......Full exposure lamp 8...Developer 9...Transfer charger 11...Transfer paper 16...・・・・・・Blank no light/Bu17...
・・・・・・C table turtle 1)゛Potential sensor 18・・・・・・
...Calculation, control, storage section 19.20...
...-Next, secondary iM4 pressure tranos 22...
・Standard white plate 23...Original illumination lamp 24...
...Manuscript illumination lamp Ichihara v + , V 2 , V
s...Models for bright, dark and white areas°
Crying

Claims (1)

[Claims] Before copying in an electrophotographic device, each model potential is formed on the photoreceptor, and these model potentials are detected by a potential sensor.
The surface of the latent image is calculated by calculating the contrast between the image density of the background of the document to be copied and the character pattern by % in a method of controlling the amount of light, etc. so that each predetermined standard potential and each of the model potentials are equal. A potential control method for electrophotography, which is characterized by detecting and discriminating potentials and using each standard potential according to the contrast of the original according to a predetermined method.