| 摘要 |
PURPOSE:To precisely control the concentration of a developer in a developing device by stopping the returning action of the developer by a developer returning means at the time of setting a reference value for the concentration of the developer in the developing means so that the developer from a cleaner means can be prevented from mixing. CONSTITUTION:In case of judging that a new developing device 18 is set, the driving of the toner returning means 68 is stopped and the toner collected by a cleaning device 21 is not made to mix into the developing device 18 by making a rotary shutter 99 in a closed state. After sufficiently stirring the developer D in the developing device 18, the reading of the reference value is executed by a toner concentration detector 70. Thus, the accurate reading of the reference value can be possible and the concentration of the developer in the developing means can be precisely controlled. |
