JPH0318875A - Printing device - Google Patents

Abstract

PURPOSE:To prevent fogging and a change in density by providing an electrifier unit with a temperature sensor, controlling a current flowing into the electrifier according to the temperature and correcting an environmental change in the surface potential of an image carrier. CONSTITUTION:An exposing part 2, the electrifier 3, a developing unit 5, a transfer unit 6, a cleaning blade 7, an erasure lamp 8, and a toner recovery tank 9 are arranged around a photosensitive drum 1. In this case, the electrifier unit is composed of the electrifier 3 equipped with a charge wire 21, a high pressure unit 18 and the temperature sensor 4, detects the temperature with the aid of the temperature sensor 4, and controls the current flowing into the electrifier 3 according to the temperature. In other words, by taking advantage of the characteristics that the surface potential varies with the current flowing into the electrifier 3, a change in the surface potential is corrected. Consequently, fogging and density change can be prevented.

Description

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

[Conventional technology]

Conventionally, this type of printing device has been controlled to a constant current in order to keep the current flowing through the charger constant.

[The problem that the invention attempts to solve]

In the conventional printing apparatus described above, the current of the charger 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 there is a drawback that fog or density changes are likely to occur when the environment changes.

[Means to solve the problem]

The printing apparatus of the present invention includes a temperature sensor in a charger unit that is composed of a charger and a high-voltage unit, and controls the current flowing through the charger based on the temperature.

〔Example〕

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

FIG. 1 is a schematic diagram of a printing apparatus according to the present invention. An exposure section 2 is formed around the photosensitive drum 1. Charger 3. Developing unit 5. Transfer device6. Cleaning grade 7° erase lamp 8.
The surface of the photosensitive drum 1 is negatively charged by a charger 3 in which a toner recovery tank 9 is disposed. Thereafter, the photosensitive drum 1 is exposed to light by the exposure section 2 to form a latent image on the surface of the photosensitive drum 1.

The latent image is developed with toner by the developing unit 5. The paper 20 that is fed by the paper transport mechanism 17 or the like is charged by the transfer device 6 to have a polarity opposite to that of the toner, and the developed image on the photosensitive drum 1 is transferred. The paper 20 passes through a fixing device composed of a heater roll 12 heated by a heater 13 and a pressure roll 14, and the toner is fixed thereon. After fixing, the sheets are stacked on a stacker (not shown) by discharge rollers 15 and 16. Untransferred toner adheres to the surface of the photosensitive drum 1 after the − direction transfer, and is scraped off into the toner recovery tank 9 with a cleaning grade of 7. Thereafter, the erase lamp 8 reduces the residual potential on the surface of the photosensitive drum for the next charging.

FIG. 2 shows the configuration of a charger unit according to the present invention. The charger unit includes a charger 3 having a charge wire 21.
, a high pressure unit 18 , and a temperature sensor 4 . The temperature is detected by a temperature sensor 4, and the current flowing to the charger 3 is controlled according to the temperature.

Conventionally, a charger unit controlled to a constant current has been used, but when using a photosensitive drum with environmental characteristics as shown in Figure 3, this cannot compensate for changes in surface potential ±A, resulting in fog or fog. This caused concentration changes.

The present invention utilizes the characteristic that the surface potential changes depending on the current flowing through the charger to correct the change ±A in the surface potential. As shown in the first quadrant of Figure 4, the surface potential of the photosensitive drum changes depending on the current of the charger, so by using a temperature sensor that shows the characteristics of the third quadrant and controlling the current as shown in the fourth quadrant. , the surface potential can be corrected, and fog or density changes can be prevented.

〔Effect of the invention〕

As explained above, the present invention has a temperature sensor in the charger unit, which is composed of a charger and a high-voltage unit, and controls the current flowing through the charger depending on the temperature, thereby controlling environmental changes in the surface potential of the image carrier. It can be corrected and has the effect of preventing fog or density changes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the developing process of the present invention, FIG. 2 is a configuration diagram of a charger unit according to an embodiment of the present invention, FIG. 3 is a characteristic diagram of a photosensitive drum, and FIG. 4 is a characteristic diagram of the present invention. It is. 1. Photosensitive drum, 2. LED head, 3. Charger, 4.
Temperature sensor 5. Developing unit, 6° transfer device, 7. Cleaning grade, 8. Erase lamp, 9. Toner collection tank, 10, 11° separate rollers, 12. Heat roller, 13° heater 146 Blessing roll, 15, 16, Discharge roller, 17. Feed roller, 1
8. High pressure unit, 20. Paper, 21...Charger wire.

Claims (1)

[Claims] A printing apparatus using an electrophotographic method, characterized in that a charger unit comprising a charger and a high-voltage unit includes a temperature sensor, and the current flowing through the charger is controlled based on temperature.