| 摘要 |
PURPOSE:To stably maintain toner concentration at an appropriate value by setting and controlling the toner concentration of initial developer in a developing device according to rotational speed of the developing device. CONSTITUTION:The rotational speed of the developing device can be changed by B/W normal copying mode and B/W editing copying mode, and threshold value data for toner concentration control is derived by providing each of the B/W normal copying mode and the B/W editing copying mode with toner concentration setting control mode and measuring the toner concentration of the developer in the developing device ion this mode. Then, the toner concentration of the initial developer in the developing device is set and controlled according to the rotational speed of the developing device. Therefore, excessive image density and ground soiling due to abnormal increase in the toner concentration, deficiency in image density due to toner scattering or reduction in the toner concentration or generation of carrier sticking to a photosensitive body 1 can be prevented even when the output characteristic of the toner concentration sensor 29 is varied when the fluidity of the developer within the developing device is varied due to variation in the rotational speed of the developing device. |
