| 摘要 |
PURPOSE:To facilitate a sensor part by comparing the toner concentration of a reference pattern visible picture, which is detected right after the start of the drive of a developing device, with the toner concentration of the reference pattern visible picture, which is detected after an elapse of a fixed time, and judging a use condition by means of a control mechanism. CONSTITUTION:The light reflection type sensor 20, which composes a picture density controller, is arranged for a photosensitive drum 3. The sensor 20 is composed of a LED and a photoresister as a light emitting element and a light receiving element, respectively, and has a function by which the toner concentration of the reference pattern visible picture on the drum 3 is detected. Here the toner concentration of the reference pattern visible picture right after the start of the drive of the developing device 6 is compared with that after an elapse of the fixed time; sensor check by a picture density detecting mechanism is used; thereby the condition of the developing device 6 is detected. Thus, whether the developing device 6 can be used or not is judged, the need for an extra sensor part is eliminated, and the detection sensor part can be simplified. |
