| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively provide a developing device having a long life which is free from avoidable degradation and prevents avoidable degradation of a developer by detecting the deflection state of the developer by a developer toner concentration detection means in an image forming apparatus provided with a two-component developer developing device which has the developer toner concentration detection means which detects the toner concentration of the developer in accordance with change of the permeability. SOLUTION: In a representative constitution of a detection method for developer deflection, the developing device is provided with a developer vessel where the developer consisting of toner and carrier is stored, a developer carrier which carries and conveys the developer, a developer carrying means which circulates the developer in the developer vessel, and a developer toner concentration detection means which detects the permeability of the circulated developer to detect the toner concentration, and the permeability detected before a prescribed timing and that after the prescribed timing are compared with each other by the developer toner concentration detection means to detect deflection of the developer. |
