ELECTROPHOTOGRAPHIC COPIER INCLUDING PHOTOCONDUCTOR CHARGE SENSING MEANS

摘要

A copier includes a conductive drum support 1 carrying a photoconductor 2. A portion of the drum, either seal 3 or, if a fixed photoconductor layer is used, an uncovered section, presents a conductive outer surface at a fixed reference potential, for example earth. A capacitive probe 6 senses the charge on a portion of the photoconductor adjoining the conductive outer surface and provides a signal indicating that charge relative to the fixed reference potential. Circuits 7 and 11 are responsive to the outputs of the probe to control a charging device 15, an illumination station 4 and a biassed magnetic roller 8 in a developer station.