| 摘要 |
PURPOSE:To keep always the sensor output in the stable state to keep always the developer concentration constant by providing a sensor which detects the concentration of the developer so that this sensor faces a position aft development and making the gap between the sensor and a sleeve shorter than that between a doctor and the sleeve. CONSTITUTION:A sensor 20 which detects the toner concentration of a developer 2 is arranged to face a magnetic pole N2 of a magnet 11 after development. This sensor 20 is attached to an upper cover 18 of a developing tank 19 and is attached a considerable length apart from a sleeve 10 so that the center of the sensor 20 coincides with the center of the magnetic pole N2 of the magnet 11. That is, the sensor 20 is arranged to satisfy x>y where (y) is the gap be tween the sleeve and the sensor 20 and (x) is the gap between a doctor 12 and the sleeve 10. Since the sensor 20 is arranged in this manner, the quantity of the developer brought into contact with the surface of the sensor 20 is not changed much even if the gap (x) between the doctor 12 and the sleeve 10 is changed, and a stable magnetic permeability detection output is obtained. |
