| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing device for surely and thoroughly bringing developer into contact with the detection surface of a toner concentration sensor and accurately detecting the toner concentration, even in a small-sized developing device. SOLUTION: The developing device is provided with a developer stirring spiral member which is arranged in a developer carrying path so as to extend along the developer carrying path, and the toner concentration sensor which is arranged on the midway of the developer carrying path, and as for the diameter of the spiral member, the diameter near the detection surface of the toner concentration sensor is made smaller than the diameter of other part of the spiral member. |
