device for the schwärzungsdichte figure of vervielfältigenden template in a elektrophotographischen copier

摘要

PURPOSE:To properly control the image density by controlling it through a bias voltage control and by detecting the toner image, which is obtained from a patch placed on a carriage, thereby to control the supply of the toners to a developing device. CONSTITUTION:A control circuit 15 judges the term, for which the exposing side of a patch 3 is positined on a roller 6, from the counted number of the pulses of an angular sensor 14 so that the bias voltage is controlled to a preset level for that period and so that the bias voltage is controlled to a preset level during the period for which the exposure side of an original 2 is positioned on the roller 6. As a result, the density of the image of the original is controlled to a preset level, and the developing density of the patch can be constant irrespective of the preset value of the image density so that toner density to be controlled by the developing density of the patch can be constant and so that the control of the image density by the bias voltage control can be proper.