| 摘要 |
PURPOSE:To prevent the surface staining of an image and the scattering of toner by correcting image density by the amount that desired density is attained within the range of the supplied toner electrostatic charging ability of a developing device at the time of correcting a target density value so that toner concentration may be high. CONSTITUTION:Based on the output of a toner concentration sensor 13 disposed to a developing device 4, the control of the replenishment of the toner that the device 4 is replenished with the toner is performed when the detected toner concentration is lower than the target one. At the time of detecting that the image density formed for detection is lower than the desired one, the target density value is corrected by the amount that the image density attains the nearly desired one within the range of the supplied toner electrostatic charging ability of the device 4. Thereafter, the control of the replenishment of the toner is performed according to the corrected target density value. By making the toner concentration high, the image density is made approximate to the desired one and the supplied toner quantity is prevented from exceeding the toner electrostatic charging ability of the device 4. |
