| 摘要 |
PURPOSE: To perform accurate potential calibration and control stable with time and to obtain an image having stable quality by interrupting the supply of bias voltage to an image carrier and discharging charge applied to the image carrier to ground via a resistor. CONSTITUTION: At the time of performing ordinary copying operation, reed relay contacts 75-2 and 76-2 where a switching means is a high breakdown strength reed relay are connected to an N.C. side, DC bias output is connected to one side of the output end of AC bias output, and a photoreceptor is connected to the F.G. side of the ground. At the time of performing potential calibrating operation, the relay contacts 75-2 and 76-2 are switched and connected to the N.O. side, the DC bias output is connected to the photoreceptor, and further a discharge resistor R77 is connected to the photoreceptor in parallel. In the case there exists the discharge resistor R77, the charge charged in the stray capacitance Cdr 78 of the photoreceptor flows in the F.G. side of the ground through the resistor R77 and an output level becomes OV in 20-50msec. Furthermore, the stable potential is obtained at the DC bias output by the resistor R77 and the accurate potential calibrating operation is performed. |
