Electrophotographic apparatus comprising improved bias source for magnetic brush

摘要

A photoconductive sheet is wrappingly attached to an electrically conductive, grounded rotary drum so that part of the drum is covered by the sheet and another part of the drum is exposed. A magnetic brush developing member comprises a magnetic core and an electrically conductive sleeve surrounding the core. An electrically insulative layer is formed on the periphery of the sleeve. The core and/or sleeve are rotated to pick up toner particles which brushingly engage with the sheet to develop an electrostatic image formed thereon. A bias voltage is applied to the sleeve to prevent adherence of toner particles to white areas of the image. A regulator device maintains the bias voltage constant to prevent detrimental effects of charge buildup and dissipation across the electrically insulative layer on the sleeve of the magnetic brush.