| 摘要 |
PURPOSE:To eliminate the need for leading cords and to limit the number of toner concentration detecting sensors to one regardless of the number of developing devices by separating a magnetic sensor from plural developing devices and sharing it with them. CONSTITUTION:The magnetic sensor 51 is attached to the front of a mobile stand 53 through a cushion pad 54. In synchronization with that a guiding means 33 brings the Bk developing device 7b, for instance, into contact with a photosensitive drum 6 with the aid of an eccentric driving body 36, a driving body 56 advances the mobile stand 53 with a spring 53, and brings the sensor 51 to abut on the rear outside surface of the developing device 7b. When the other C, M and Y developing devices 7c, 7m and 7y reach the developing height position, the sensor 51 acts similarly. When it abuts on the backs of the developing devices 7b, 7c, 7m and 7y, the concentration of two-component toner housed in them can be detected as current change due to change in inductance. |
