To prevent image defects occurring in a charging roller having large irregularities in a rotational direction, when charging control is performed, based on the operating values calculated from the average of the measurement values of a charging circuit.
The amplitude value of a voltage applied to the charging roller 21 is detected as a first detection value, the amplitude value of the differential waveform of a charging voltage is detected as a second detection value, and an AC current flowing into a photoreceptor from the charging roller 21 is detected as a third detection value. The minimum value of the discharge capacity of the charging roller 21 in its rotational direction is calculated, based on these first, second and third detection values, so that the charging voltage is controlled so as to make the minimum value of the discharge capacity a predetermined discharge current value.
OSHIMA NOBUO
OKA HIDETO
Yoshiyuki Kawaguchi
Mayuko Wakuda
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