| 摘要 |
PURPOSE:To compare and decide a toner adhering amount on the surface part of a photosensitive body and to accurately detect surface staining by comparing and deciding the amount in a state the output of a toner sensor in the case of detecting the surface of the photosensitive body in the non-developing state of a developing device is taken as reference. CONSTITUTION:In the non-developing state which is a bristle cutting state where none of the developing devices exist on a developing sleeve, the toner adhering amount of the surface part of the photosensitive body is detected by the toner sensor consisting of a reflection type photosensor. The detected result is taken as a reference value, which is compared with the value detected by the toner sensor when only the developing device from which the surface staining is to be detected is allowed to perform developing in a state the developer is bristled. When the detected value is larger than the reference value, it is judged that the surface staining does not occur. Therefore, the surface staining is accurately detected. In the case that the surface staining occurs, the developer is replaced when it is judged through a sheet number counter that the developer completes its life, and the appropriate control of the toner concentration is performed with the intension of rising by a stirring effect when the developer does not complete its life. |
