JPS54154334A - Electrophotographic apparatus and nethod thereof - Google Patents

Abstract

PURPOSE: To form distinct images free from fog by detecting the sum of the primary charging current to a photoreceptor and opposite polarity current and controlling the bias voltage of a developing device.

CONSTITUTION: The capacity of a photoreceptor 13 constituted by a conductive layer, photoconductive layer and insulation layer is made the same as the capacity of the insulation layer by blank exposure. Next, the photoreceptor 13 having been evenly charged by a primary charger 14 is charged to the polarity opposite from that of primary charging by way of a discharge electrode 22 after image exposure, whereby latent images are formed. The sum of these charging currents are detected with current detectors 18 and 19, 25 and 26, current measuring means, etc., and the bias voltage of a developing device 30 is feedback-controlled by way of a converter 29 according to the measured current of the means 28. Hence, even when the primary charging voltage is changed owing to the fatigue deterioration, etc. of the photoreceptor or the ambinent environments or supply voltage has fluctuated, the bias value at the development processing is so controlled as to become always a fixed correct value, thus the high contrast images which do not cause fog in their bright parts in correspondence to the drastic changes of the charging currents are formed.

COPYRIGHT: (C)1979,JPO&Japio