| 摘要 |
PURPOSE:To detect the accurate residual amount of developer even when an AC power source and the impedance of shielding wire are varied due to an environmental change. CONSTITUTION:AC bias generated by an AC bias generator 3 is impressed on a developing sleeve, and the AC bias having amplitude in accordance with the value of an equivalent capacitor 103 appears at a toner amount detecting electrode 102. The AC bias is inputted to a toner voltage amplitude detecting circuit 5 through the shielding wire 201, and is transformed to DC potential (toner voltage) in accordance with the amplitude, and is impressed on the inverse input of a comparator 7. At the same time, the AC bias generated by the AC bias generator 3 is inputted to a reference voltage amplitude detecting circuit 6 through the capacitor 401, and is transformed to the DC potential (reference voltage) in accordance with the amplitude and is impressed on the non-inverse input of the comparator 7. When toner is consumed and the toner between the developing sleeve and the toner amount detecting electrode starts to reduce, the inverse input potential (toner voltage) of the compartor 7 starts to lower. |
