JPS58159552A - Electrophotographic apparatus - Google Patents

Abstract

PURPOSE:To obtain a stable print quality, by monitoring surface potential of a photoreceptor with a surface electrometer, feeding back this value, controlling charging voltage, and retaining the surface potential always constant. CONSTITUTION:A photoreceptor 1 is electrostatically charged uniformly with a corona charger 2, its surface potential is monitored with a surface electrometer 9, and transmitted to a DC high voltage power source 3. This value is compared with a predetermined potential in the power source 3, when lower, charging voltage is raised and when higher, it is lowered. This feedback mechanism retains the surface potential always constant, and permits stabilized print quality to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic apparatus such as a non-impact printer, and particularly to a photoreceptor charging device thereof.

Conventionally, there was a device of this type as shown in Figure O1. In the figure, 11) is an electrophotographic photoreceptor such as a selenium drum,
(2) is a corona charger that uniformly charges this photoreceptor il+, and (3) is this corona charger (2) and transfer device (41).
(5) is a DC high-voltage power supply that applies voltage to the photoreceptor il+
OF T (optical fi'
ber tube), (6) is a developing machine that develops the electrostatic latent image formed by image exposure, (7) is a cleaner brush that cleans the surface of the photoreceptor, and (8) is a cleaner brush that removes the residual charge on the photoreceptor. It is a cleaner lamp to be erased.

A conventional electrophotographic apparatus is configured as described above, in which the electrophotographic photoreceptor fi+ rotates at a constant speed, and the corona charger (2) rotates at a constant speed.
The toner is uniformly charged by the TE, imagewise exposed by the 0FT (5) to form an electrostatic latent image, and further developed with toner by the developing device (6). The toner-developed image on the photoreceptor film is transferred onto printing paper by a transfer device (4), and this transferred image is fixed and output. On the other hand, the photoreceptor tll
The toner remaining on the top is scraped off by the cleaner brush (7), the residual charge is erased by the cleaner lamp (8), and the process returns to the charger (21).The above process allows continuous printing. In such a conventional device, the voltage applied from the high-voltage power supply (3) to the charger (2) K is set in advance and remains constant regardless of the condition of the photoreceptor fi+.

Since the photoreceptor charging device of a conventional electrophotographic apparatus is constructed as described above, the charging voltage is always constant, and the surface potential of the photoreceptor fluctuates due to deterioration of the electrophotographic photoreceptor or changes in the atmosphere, causing printing problems. The drawback is that the quality changes, and to compensate for this, the operator or service person had to finely adjust the charging voltage setting.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by monitoring the surface potential of the photoreceptor with a surface electrometer 1 and controlling the charging voltage by feeding back this value, The purpose of this method is to provide an electrophotographic apparatus that always obtains a constant surface potential of the photoreceptor, thereby achieving stable printing quality.

FIG. 2 shows an embodiment of this invention, 11)
- (8) are exactly the same as the above-mentioned conventional device. (9
) is a surface electrometer installed on the electrophotographic photoreceptor +11 to monitor the surface potential of the photoreceptor.

This surface electrometer (9) is connected to a terminal ial of a DC high voltage power supply. Note that the terminal +al of the DC high voltage power supply is a charging power supply, the terminal (bl is a transfer power supply, and the terminal (0) is a grounding terminal).

In the electrophotographic photoreceptor charging device configured as described above, the electrophotographic photoreceptor +1 is charged by the corona charger (2).
1 is uniformly charged, the surface potential of the photoreceptor is monitored by a surface electrometer (9), and a DC high voltage power supply (3)
will be communicated to. This measured value is the DC high voltage power supply (3)
If the potential is lower than that value, the charging voltage is increased, and if it is higher, the charging voltage is decreased. Due to this feedback mechanism, the surface potential of the photoreceptor is always kept at a constant potential. Since the photoreceptor surface potential has a large effect on the print quality of an electrophotographic apparatus, keeping the photoreceptor surface potential constant means that stable print quality can be obtained.

In the above embodiment, the value of the surface potential is set in advance in the DC high-voltage power supply (3), but a mechanism for changing the set potential from the outside may be provided.

Further, in the above embodiment, an OF T +51 was used for image exposure, but a light emitting element such as a 1-day light emitting device may be used, and the development does not need to be toner development, but may be a liquid development or a mist method. Furthermore, the electrophotographic photoreceptor fil does not have to be cylindrical, and even if it is paper-shaped or flat, the same effect can be achieved.

As explained above, this invention is equipped with a control device that controls the output of the power supply in four ways, and is configured to keep the charged potential constant, so that it is effective in providing stable printing quality in an electrophotographic apparatus.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional electrophotographic photoreceptor charging device, and FIG. 2 is a block diagram showing an electrophotographic photoreceptor charging device according to an embodiment of the present invention. In the figure, (1) is an electrophotographic photoreceptor, (2) is a corona charger, +31ij DC high voltage power supply, and (9) is a surface electrometer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Shin Kuzuno −

Claims (1)

[Claims] +11 A charger disposed opposite to the surface of the photoreceptor to charge the photoreceptor, a power source connected to the charger, a surface potential of the photoreceptor detected, and a detected value and a reference value. An electrophotographic apparatus comprising a control device that compares and controls the output of the power supply based on the deviation. (2) The electrophotographic apparatus according to claim 1, wherein the control device includes a surface electrometer arranged to face the surface of the photoreceptor and detect the surface potential thereof.