| 摘要 |
PURPOSE:To fix bias voltage by switching a developing bias power supply to be used at the development of a recording latent image on an electrostatic carrier to a developing sleeve and an earthed resistor element at the development of a reference latent image. CONSTITUTION:A recording latent image on a photosensitive drum 5 is developed with toner by the developing sleeve 7. At that time, the sleeve 7 is connected to the earthed bias power supply 10 to apply a voltage to the sleeve and to prevent the developed image from fogging. On the other hand, a black reference pattern B is adhered to an original board 1 and a reference latent image is formed on the drum 5 and developed by the sleeve 7. At that time, a switch 12a is turned to connect the sleeve 7 to the earthed resistor element 11. The change of a developing current into the drum 5 coated with electrically charged toner is detected by a voltage follower 14 as the electric potential between the sleeve 7 and the resistor element 11 to detect the quantity of toner adhesion and control the quantity. Since the developing bias power supply for the recording latent image can be changed to a connection line for detecting the quantity of toner adhesion through the switch, a fine image free from fogging can be obtained. |
