| 摘要 |
PURPOSE:To prevent the excessive electrostatic charging of a juncture and to improve a copying stage by controlling the electric current of a photoreceptor flowing from an electrostatic charger to the photoreceptor so as to decrease said current only when the approaching of the juncture of the photoreceptor to the electrostatic charger such as a corna discharger for electrostatic charging is detected. CONSTITUTION:When the detection piece of a limit switch 20 is fitted into a hole H by turning of a photoreceptor SD in an arrow direction and the approach of a juncture J to an electrostatic charger 10 is detected, the switch 20 is opened. A one shot circuit OS is then operated to conduct a transistor switch Tr only for the time determined by the time constant of a resistor R3 and a capacitor C1, and the resistor R2 attains the nearly short circuited state; therefore, a remote voltage RE decreases as well and an electric power source part 31 decreases the driving voltage of the charger 10 by as much as the voltage corresponding to said voltage drop, thereby reducing the photoreceptor current flowing in the photoreceptor SD. Therefore, if the circuit constant is so set that the photoreceptor current flowing in the stage of such control is decreased to the extent that excessive electrostatic charging is obviated, the photoreceptor SD is kept free from the insulation breakdown, and a cleaner part or the power source part 31 is kept free from overload. |
