JPS63180981A - Printing device - Google Patents

Abstract

PURPOSE:To precluded fogging and density variation by providing an erasure unit with a sensor which can correct environmental variation in the surface potential of an image carrier and a light quantity feedback mechanism which uses the sensor. CONSTITUTION:Toner which is not transferred partially sticks on the surface of a drum after transfer and is scraped off by a cleaner blade 7. The surface potential of the drum is lowered uniformly by exposing a cold cathode tube 8 because there is a difference between an exposed and an unexposed part. This serves as the cold cathode tube 8, but the surface potential of the photosensitive drum varies with the quantity of erasure light. The erasure unit consists of the cold cathode tube 8 and a high voltage power source 11, and a CdS cell 9 is arranged so as to the quantity of erasure light constant and the current of a high voltage power source is brought under feedback control. Thus, a light quantity feedback mechanism which uses the sensor is provided and the quantity of erasure light is varied according to environment, and consequently the environmental change in the surface potential of the image carrier can be corrected and fogging and density variation are precluded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic printing apparatus.

[Conventional technology]

Previously, the printing equipment in this building had been equipped with a light intensity feedback mechanism using a sensor with good environmental characteristics in order to stabilize the erase light intensity.

[Problem that the invention seeks to solve]

In the conventional printing apparatus described above, the amount of erase light remains constant even if the environment changes. Therefore, when using an image carrier whose surface potential changes depending on the environment, the surface potential cannot be corrected, and therefore, when the environment changes, capri or density changes are likely to occur.

[Means for solving problems]

The printing apparatus of the present invention includes a sensor having a characteristic capable of correcting environmental changes in the surface potential of the image carrier in the erase unit;
It has a light amount feedback mechanism using the sensor.

〔Example〕

Next, the present invention will be explained using the drawings.

FIG. 1 is a cross-sectional view of the development process of the present invention. A path light LED, a drive 2, a main charger 3, a developing unit 4, a sleeve 5, a transfer charger 6, a cleaner blade 7, and a cold cathode tube 8 for erasing are arranged on the rotating side of the photosensitive drum 1.

A CdS cell 9 for a light amount sensor is arranged at the turn of the erase tube 8. Further, there is a cleaner tank 11 that retains the waste toner scraped off by the cleaner blade 7.

The main charger 3 charges the surface of the photosensitive drum to e and a constant surface potential Vo. The portion exposed by the LED head is de-charged and drops to the image potential vI. Toner negatively charged at this portion by the bias potential VB value adheres to the sleeve 5 and the citrus surface.

The paper fed by the paper transport mechanism is positively charged by the transfer charger 6, and negatively charged toner is attached to it. The paper is passed between a heat roller 15 heated by a halogen pump 16 and a pressure roller 17 pressed against the heat roller with a constant pressure, so that the toner is fixed on the paper, and the toner is fixed on the paper.
8.19 and stacked on a stacker (not shown).

A portion of the toner that has not been transferred adheres to the surface of the drum after the transfer, and is scraped off by the cleaner blade 7. Since there is a difference in potential on the drum surface between exposed and unexposed areas,
By exposing the cold cathode tube 8 to light, the drum surface potential is lowered uniformly. This is the role of the cold cathode tube 8, but the surface potential on the photosensitive drum varies depending on the intensity of the erase light amount.

Figure 2 shows the configuration of the erase unit.

The erase unit is composed of a cold cathode tube 8 and a high voltage power supply 10, and in order to keep the amount of erase light constant, a Cd8 cell 9 feeds and controls the current of the high voltage power supply.

The amount of erase light is determined by the resistance of the CdS cell. Conventionally, CdS was used, which does not change much due to the environment, but when using a photosensitive drum with the characteristics shown in Figure 3, it is not possible to compensate for changes in surface potential ± people. , which caused capri or concentration changes.

The present invention utilizes the characteristic that the surface potential changes depending on the amount of erase light to correct the change in surface potential.

As shown in the first quadrant in Figure 4, the surface potential of the photosensitive drum changes depending on the amount of erase light, so by performing light amount feedback using CdS, which shows the characteristics of the third and fourth quadrants. Furthermore, the surface potential can be corrected and capri or concentration changes can be prevented.

〔Effect of the invention〕

As explained above, the present invention has a sensor in the erase unit that has the characteristic of correcting environmental changes in the surface potential of the image carrier, and has a light amount feeder mechanism using the sensor to adjust the amount of light according to the environment. By changing the amount of erase light, environmental changes in the surface potential of the image carrier can be corrected, and capri or density changes can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the developing process of the present invention, FIG. 2 is a configuration diagram of the erase unit, and FIG. 3 is a characteristic diagram of the photosensitive drum.
FIG. 4 is a characteristic diagram of the present invention. 1...Photosensitive drum, 2...LED head, 3...Main charger, 4...
Developing unit, 5... Sleeve, 6...
・Transfer charger, 7...Cleaner blade,
8...Cold cathode tube, 9...Cd8 cell,
lO...High voltage power supply, 11...Cleaner tank, 12...Feed roller, 13.14
... Separate roller, 15 ... Heat roller, 16 ... Heater, 17 ...
Pressure roller, 18.19...Discharge yfi
2nd side'jfJ3 fissure'fi4 figure

Claims (1)

[Claims] A printing apparatus using an electrophotographic method, characterized in that the erase unit has a sensor having a characteristic capable of correcting environmental changes in the surface potential of an image carrier, and a light amount feedback mechanism using the sensor. Device.