Development method and apparatus and multicolor image forming apparatus using these

摘要

The development apparatus of this invention includes a developer supporting body consisting of a rotatable non-magnetic sleeve and a magnet roll fixedly installed within the rotatable non-magnetic sleeve. The development method involves the following steps: a latent image formed on a latent image supporting body is developed or made visible with a two-component developer carried on the developer supporting body in a non-contact manner; a horizontal magnetic field which is orientated in the circumferential direction of the developer supporting body is applied to the developer in an effective development area on the developer supporting body, the effective development area facing the latent image supporting body; and a developer movement promotion magnetic field is applied locally to a part of the effective development area on the developer supporting body so that the developer is expelled from that part of the effective development area and that chains of carrier of the developer in the developer expelled region are slid in the circumferential direction of the developer supporting body. This development method ensures a sufficiently high development performance during the multicolor image forming process without disturbing the toner image formed.