| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device capable of detecting toner concentra tion with high precision by providing level difference of a developer in the vicinity of a shortened transportation path 06 without retaining the developer. SOLUTION: In the developing device with a developer transportation area the inside of which the developer is filled, a transportation member which is provided in the developer transportation area and transports the developer by rotation and a concentration sensor to measure toner concentration in the developer transportation area, the transportation member is provided with a rotational axis and the helical shape formed on the rotational axis and the rotational axis is provided at least with a large diameter part to be opposed to the density sensor and a small diameter part with diameter smaller than that of the larger diameter part in its axis direction. |
