| 摘要 |
PURPOSE:To obtain good image quality free from surface stains, etc., by stably replenishing toners from a replenishing roller to a developing sleeve. CONSTITUTION:A developing bias VB is composed of DC AC VBD and AC VBA and a replenishing bias VH is formed of a DC VHD The electrostatic change quantity Q/M and adhesion M/A of the negatively charged toners on the replenishing roller 29 are respectively set at -1muC/g>Q/M>-15muC/g, 0.1mg/ cm<2M/A<0.5mg/cm<2>. VB may be composed of the DC VBD and AC VBA and VH may be composed of the DC VHD and AC VHA The periods and phases of VBA and VHA may be made approximately equal to each other. The voltage difference of VBD and VHD or the phase difference of VBA and VHA may be changed as well. The developing bias VB and the replenishing bias V may be so set as to satisfy VB-VH<=0 at all times. The potential difference between VB and VH may be set according to the electrostatic charge quantity Q/M of the toners and may be corrected according to the output values of a toner concn. sensor or thermometers and hygrometer. |
