| 摘要 |
PURPOSE:To prevent unnecessary toner and carrier from sticking to a photosensitive body at the beginning and at the end of the image forming by switching the bias of a developing device on or off while an auxiliary electrostatic charging area is passing the moving area of the developing device. CONSTITUTION:A grid voltage is controlled by using a scorotron electrostatic charging device 2 as a main electrocharging charging device, then the auxiliary electrostatic charging area having the lower electric potential than the main electrostatic charging area is formed. And at the beginning and at the end of the image forming action, the auxiliary electrostatic charging area having the lower electric potential than the main electrostatic charging area is formed on the surface of the photosensitive body, then the bias voltage of the developing device 5 is switched on or off while the auxiliary electrostatic charging area is passing the developing operation area of the device 5. The potential difference between the surface of the photosensitive drum 1 and the developer of the developing device 5 is reduced, then the unnecessary developer will not stick on the photosensitive drum 1 by this. |
