PURPOSE: To improve the stirring efficiency of developer, newly supplied toner and recycled toner in a developing device, to rapidly uniformize the toner concentration distribution in the developer and to improve the responsiveness of toner concentration control.
CONSTITUTION: This developing device is constituted of a main stirring member 103 stirring the developer and supplying it to a developer carrier, an auxiliary stirring member 104 mixing and stirring the developer refluxed from the main stirring member 103 and supply toner and resupplying it to the main stirring member 103 and a toner concentration detecting sensor 106 arranged on a developing device housing 101 bottom part under the fin part of the auxiliary stirring member 104 and detecting the toner concentration in the developer; and developer circulation in the direction of a rotary shaft normal line by the means of the auxiliary stirring member 104 is restricted by providing a projecting rib at the boundary part of the developing device housing 101 bottom part under the middle of the main stirring member 103 and the auxiliary stirring member 104, and also circulation performance of the developer is made excellent by making the boundary part of the developing device housing 101 bottom part near the detecting surface of the toner concentration detecting sensor 106 in a flat shape where the projecting rib is removed.
OKUBO TAKASHI
KIMURA TAKENOBU
