| 摘要 |
PURPOSE:To measure the real toner concentration of a developer by using at least one of plural magnets as a cleaning magnet and setting contacting force with respect to the transparent detecting window of the developer held on the cleaning magnet stronger than that of the other magnet. CONSTITUTION:At least one of plural magnets 45 and 46 is used as the cleaning magnet 45, and the contacting force with respect to the transparent detecting window of the developer held on the cleaning magnet 45 is made stronger than that of the other magnet 46 by properly setting magnetic force or a distance between the magnet and the transparent detecting window 45. Therefore, the transparent detecting window 54 is surely cleaned by the cleaning magnet 45, and a developer concentration is measured in a state where the developer does not stick to the transparent detecting window 45. On the other hand, the developer concentration is detected by the developer held by the magnetic force of the magnet in the space having the constant thickness of the magnet 46 and the transparent detecting window 54. Thus, an accurate developer concentration can be detected regardless of the quantity and bulk density of the developer. |
