| 摘要 |
<p>An electrophotographic developing apparatus used with a two-component developer composed of a carrier and a toner both accommodated in a developer vessel (30), in which an intermediate roller (32) including a non-magnetic sleeve (32a) accommodating a magnet roller (32b), is disposed between a developing roller (33) for selectively attaching the toner to an image carrier (9) and an agitating means (31) for tribo-frictional charging the carrier and the toner, and when a magnetic brush consisting of the carrier and the toner is carried on the intermediate roller (32), the toner alone is transferred to the developing roller (33) by making use of a first bias (or a preliminary developing bias) developed between the intermediate roller (32) and the developing roller (33). In a regular developing step for selectively attaching toner from the developing roller (33) to the image carrier (9), a second bias (a regular developing bias) is applied between the developing roller (33) and the image carrier (9) to let the toner jump so as to effect development. In the preliminary developing step, a two-component magnetic brush developing method is adopted to form a thin layer of high density toner on the developing roller (33), and at the developing position the toner is caused to jump toward the image carrier (9) by the regular developing bias, thus effecting the development. Sufficient toner density thus can be ensured in high density image formation, specifically in the case of attaching toner to the entire transfer sheet surface such as the full black image development, the photographic development or the full color development.</p> |
