| 摘要 |
PURPOSE:To decrease the burden in a cleaning part and to prevent conversion of a toner to sludge by impressing a bias voltage in a reverse direction for the time corresponding to the time for impressing the bias voltage in a positive direction. CONSTITUTION:A control part 30 outputs the 12th pin at a low level and the 17th pin at a high level right after passage of the rear end of a latent image through a developing electrode 13. The bias voltage of the electrode 13 is changed over to -750V. The part 30 brings the 12th pin and the 17th pin to a low level and the outputs of AND circuits 33, 34 to the low level when the time when -750V is impressed to the electrode 13 elapses the time corresponding to the time when +240V is impressed to the electrode 13 before said time. The outputs of the 11th pin and the 12th pin of a driver 31 are brought to a high level by the output signals from the circuits 33, 34, by which relays RR1, RR2 are turned off and the electrode 13 is made electrically floating. The part 30 brings the 12th pin and the 17th pin to a high level just before the front end of the next latent image arrives at the electrode 13. The electrode 13 is thus impressed with +240V and the operation is similarly executed succeedingly until the copying operation ends. |
