| 摘要 |
PURPOSE:To suppress the supply of toner completely by simple structure when development is not performed by controlling a bias voltage applied to a developing roller and an elastic roller, and giving a developer a difference in electrostatic attractive force and performing supply control. CONSTITUTION:The relay control circuit 11 of a controller 7 grounds a developing roller 1 through a contact 8a when development is not performed and an elastic roller 4 is applied with a bias voltage from a power source 10 through a contact 9a. Toner attracted to the elastic roller 4 strongly does not move a developing roller 1 with low attractive force as a result and no unnecessary toner stick on a photosensitive body 2. When a copying process beings to advance, the relay control circuit 11 switches the contacts 8 and 9 to apply the bias voltage to the developing roller 1 from the power source 10 and also ground the elastic roller 4. Toner charged positively by friction in a hopper 5 is supplied to the developing roller 1 with large toner attractive force through the elastic roller 4.
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