| 摘要 |
PURPOSE:To obtain image quality with stable gradations at all times irrelevantly to the rest of toner by detecting the torque of an agitator and adjusting the bias voltage of a developing roller automatically according to the rest of toner. CONSTITUTION:Single-component toner is agitated by the agitator 30 in the hopper 29 of a developing unit 18 and supplemented to a developing roller 32 by a supplementing roller 31, and the toner on the developing roller 32 is layered thinnly with a blade 3 and carried onto a photosensitive body to perform development. The developing roller 32 and supplementing roller 31 are applied with voltages which have a certain constant potential difference and when the input voltage Vi to the supplementing roller 31 varies, the bias voltage Vb to the developing roller 32 also varies. This bias voltage Vb is adjusted automatically according to variation of the torque of the agitator 30. Namely, a detecting device 35 detects the torque of the agitator 30 as an electric signal and a bias voltage control circuit 36 controls a variable bias unit 37 according to the torque quantity to adjust the input potential Vi. Thus, the bias voltage Vb of the developing roller 32 is adjusted automatically according to the rest of toner. |
