| 摘要 |
PURPOSE:To obtain sufficient image density even in the case the electrostatic charging ability of developer is deteriorated by providing a control means for switching developing potential and a specified target value at the time of forming a reference image for detection in the case a toner concentration target value becomes equal to or above previously set threshold. CONSTITUTION:At the time of forming the image, a control part 51 turns on a developing clutch 54 through a driver 53 so as to drive a developing device. The control part 51 functions also as a correction means for correcting the toner concentration target value VREF, and forms the reference image for detection in every specified timing so as to correct the target value VREF. When the target value VREF becomes >=3.5V being the previously set threshold, the control part 51 switches the developing potential at the time of forming the reference image for detection and switches the target value of the output value of a reflection type photosensor 42 to be a specified value. Thus, even when the electrostatic charging ability of the developer is deteriorated with time, the image satisfies the target lower limited value and the sufficient image deity is obtained. |
