Electrophotographic copier and charging means used therefor

Abstract

The invention is directed to an apparatus for an electrophotographic process, equipped with a charging device of a contact type using a conductive roller or brush, and the charging device used therefor. The apparatus is characterized in the following constructions: roll-shaped fiber aggregation that is rotated in contact with the photoconductive surface through a spacing member; use as applied voltage to the fiber aggregation of periodically oscillating voltage having a lower limit exceeding the surface potential of the photoconductor in the aforementioned device; a brush-type charger that is vibrated while contacted with the photoconductor surface and regulated as required; a fiber roll-type charger wherein ventilation holes are disposed on the roller substrate surface; the fiber roll-type charger with holes further including a closed container with exhausting means enclosing the charger; set-up of a product of planting fiber intervals on a fiber roller and a peripheral velocity ratio of the photoconductor to the roller such that the product is smaller the average particle size of the developer used; changing application voltage to a charger roller depending transfer-treated portion or portions otherwise on the photoconductor surface; and provision of dirt preventer, aligned with the longitudinal direction to the charging roller with conductive fiber, and shiftable between contact and spaced position.