DEVELOPMENT APPARATUS AND IMAGE FORMING APPARATUS USING SAME

摘要

PROBLEM TO BE SOLVED: To suppress attachment of carrier to the surface of an image carrier when toner concentration in developer is lowered or when processing speed is slowed down.

SOLUTION: The development apparatus includes: the developer carrier 48 for carrying two component developer comprised of toner and the almost spherical carrier and with specific gravity which is smaller than for a ferrite carrier and developing an electrostatic latent image formed on the image carrier; a toner concentration detection means 56 for detecting the toner concentration in the developer; and a bias control means controlling a duty ratio which is the proportion of a component moving the toner to the image carrier side occupying one cycle among AC wave forms in developing bias voltage applied to the developer carrier when the toner concentration in the developer is lowered to a prescribed value or below based on the detected result by the toner concentration detection means so that the duty ratio is lower than when the toner concentration in the developer exceeds the prescribed value.

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