| 摘要 |
PURPOSE:To provide an inexpensive developing device capable of accurately detecting toner density. CONSTITUTION:Developer in a housing 411 is stirred and carried with a spiral shaft 413 having screw blades 414. A permeability sensor 440 for detecting toner density pierces the side wall 411a of the housing 411. A gap B between a screw blade part 414B on the downstream side of a screw blade part 414A and the inner wall surface 411b of the housing 411 is set narrower than a gap A between the sensor surface 440a of the sensor 440 and the screw blade part 414A to which the surface 440a is opposed. Since the screw blades 414 is not brought into contact with the sensor surface 440a, the gap between the sensor surface 440a and the screw blades 414 is made narrow and the replacement of the developer at this part is accelerated. |
