| 摘要 |
PURPOSE:To obtain a proper developed image without reference to manufacture variance of a photosensitive body by controlling a developing bias by a potential measuring circuit corresponding to dark attenuation up to a development part which is detected before the start of copying operation. CONSTITUTION:Dark part potentials of potential sensors 11 and 12 provided before and behind the development part 4 are measured by potential measuring circuits 13 and 14 under the condition that the output of a primary electrostatic charger 2 before the start of copying operation is made constant. The mean value of their measured values is processed in a DC control circuit 15 as the dark part potential of the development part 4 to determine the developing bias which is suitable to the measured values. The determined developing bias is applied to a developing sleeve 10 by a high voltage transformer 16. Consequently, even when a photosensitive body 1 which has large dark attenuation is used, proper developed images has density above specific density are obtained without damaging a photosensitive body 1 owing to an increase in the quantity of primary charging. |
