| 摘要 |
PURPOSE:To prevent a decrease in image quality, which results from change in the replacement ratio of deteriorated developer to fresh developer, by preventing only carrier in the developer from being supplied from a developer supply unit at a stretch ahead of toner. CONSTITUTION:To replace deteriorated developer consisting of toner and carrier in a developing tank 16 successively, a mixture of toner and carrier is supplied from a developer supply unit 20, and, on the other hand, the developer in the developing tank 16 is discharged from a developer outlet 21. In a carry roller 22 provided in the developer storage chamber 20a of the developer supply unit 20, a movable permanent magnet 25, which, as the roller rotates, moves up and down in a closed space S made inside the roller, is sealed. |
