Image forming apparatus with control of charging voltage of photosensitive member

摘要

An image forming apparatus including: photosensitive members; charging devices to which a common charging power source applies a charging voltage to charge the photosensitive members; an exposure device configured to expose the photosensitive members; developing devices to form developer images on the photosensitive members; a transfer device to transfer the developer images onto a transfer medium; and a control portion configured to set a lower limit value of the charging voltage for each photosensitive member, apply the charging voltage having a magnitude not less than any lower limit value from the charging power source to the charging devices, control the output of the laser power for each photosensitive member individually, and set, based on the image density of the developer image transferred onto the transfer medium earlier, the lower limit value for a photosensitive member on which a developer image to be transferred onto the transfer medium later is formed.

主权项

1. An image forming apparatus configured to form an image on a recording medium, the image forming apparatus comprising:
a plurality of photosensitive members; a plurality of charging devices to which a common charging power source applies a charging voltage to charge the plurality of photosensitive members; an exposure device configured to expose surfaces of the plurality of photosensitive members, which have been charged by the plurality of charging devices, with a first laser power to form a non-image section potential, and expose the surfaces with a second laser power to form an image section potential; a plurality of developing devices configured to make developers adhere to areas in which the image section potential is formed to form developer images on the plurality of photosensitive members; a transfer device to which a transfer voltage is applied to transfer the developer images formed on the plurality of photosensitive members onto a transfer medium so as to sequentially superimpose the developer images on top of each other; and a control portion configured to control a magnitude of the charging voltage applied from the common charging power source and an output of a laser power from the exposure device, wherein the control portion is configured to set a lower limit value of the charging voltage for each of the plurality of photosensitive members, apply the charging voltage having a magnitude not less than any lower limit value from the common charging power source to the plurality of charging devices, and control the output of the laser power for each of the plurality of photosensitive members individually, and wherein the lower limit value for each of a second and subsequent photosensitive members in order of transferring the developer images from the plurality of photosensitive members onto the transfer medium is set based on a density of a developer image formed by a photosensitive member located before a corresponding one of the second and subsequent photosensitive members.