| 摘要 |
PURPOSE:To improve the responsiveness of developer supply control by providing two developing devices which contain the same developer at the periphery of an electrostatic latent image carrier, and changing the developing devices and performing the agitation of the developer and startup for the quantity of electrostatic charging in a stand-by state every time image formation is performed. CONSTITUTION:The two developing devices 20 and 30 where the same toner is charged are provided at the periphery of a photosensitive drum 1 and changed and used every time the image formation is performed. Even while the developing devices 20 and 30 are in the stand-by state, the agitation of the toner is carried on by the rotation of screw rollers 25 and 35 and bucket rollers 26 and 36 to increase the quantity of electrostatic charging, and when the concentration decreases, toner is supplied. The developing devices 20 and 30 are selected with a key of a printer main body and switched automatically when the B/W ratio of an image detected by a dot counter provided to a laser beam unit 10 decreases above 20%. |
