Color image forming apparatus

A color image forming apparatus, comprising:

• a plurality of image bearing members, on which a plurality of unicolor toner images, colors of which are different from each other, are respectively formed through an developing process;
• an intermediate transfer member that circularly moves along an array of said plurality of image bearing members, so that said plurality of unicolor toner images are sequentially transferred onto said intermediate transfer member by primary transferring devices, in such a manner that said plurality of unicolor toner images overlaps with each other at a same position so as to form a full-color toner image on said intermediate transfer member;
• a secondary transferring device to transfer said full-color toner image formed on said intermediate transfer member onto a transfer material as a secondary transferring operation;
• a discharging device before secondary transfer that is disposed downstream from said array of said plurality of image bearing members and upstream from said secondary transferring device in a moving direction of said intermediate transfer member, and includes a discharging electrode to apply electronic charges having a polarity opposite to that of said full-color toner image to a surface of said intermediate transfer member and a grid electrode to which a voltage having a polarity same as that of said full-color toner image is applied;
• and
• a density detecting device to detect a toner density of either at least one of said plurality of unicolor toner images or said full-color toner image,
• wherein an value of said voltage to be applied to said grid electrode is determined, based on a toner charging amount corresponding value obtained by an output value of said density detecting device.