| 摘要 |
PROBLEM TO BE SOLVED: To provide a vertical circulation system developing device excellent in responsiveness to the control of toner concentration and capable of increasing the toner concentration at the part of a developing sleeve to which developer is supplied to a prescribed value or above in an extremely short tie after toner is supplied. SOLUTION: A 2nd developer stirring and feeding mechanism 17 for feeding the developer in an opposite direction to a 1st developer stirring and feeding mechanism 16 is housed in an upper chamber 4. A lower chamber 3 and the upper chamber 4 communicate with each other at an front end part in a feeding direction by the 1st feeding mechanism 16 and at a front end part in a feeding direction by the feeding mechanism 17. Then, a communicating part between the chambers 3 and 4 positioned at the front end part in the feeding direction by the feeding mechanism 16 is provided with a developer pumping-up mechanism 25 for pumping up the developer to the chamber 4 from the chamber 3. A toner supply port 30 is provided at the part of the chamber 4 positioned within an area where the developing sleeve is arranged when viewed from the upper surface. |
