| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus which prevents deterioration in image quality or wasteful consumption of toner in the printing in a monochromatic mode, in the constitution having a common power supply for an electrifying device or a developing device. <P>SOLUTION: A developing roller 2a for each color is connected to a common developing high voltage power supply 20, and an electrifying roller 6 for each color is connected to a common electrifying high voltage power supply 20. In the constitution using such a common power supply, the process control is changed between a color mode and the monochromatic mode. The electrifying bias voltage is controlled so that the inverse contrast electric potential of the monochromatic mode is larger than that of the color mode. In the non-contact development using a nonmagnetic single component toner, the frequency of an alternating bias voltage of the monochromatic mode is controlled so as to be higher than that of the color mode. <P>COPYRIGHT: (C)2004,JPO |
