| 摘要 |
<P>PROBLEM TO BE SOLVED: To sustain a stable image without variation in density by stabilizing the thickness of a toner layer on a developing roller for a long period of time, without complicating the developing device and without decreasing the printing speed. <P>SOLUTION: The replacement of toner is enhanced by increasing the rotation speed of a magnetic roller to be higher than that of a developing roller, and successive high-speed copying is permitted in which time interval between forms (time slit B) is at the rotational one period of the magnetic roller 1. In this case, although the next copying is started after the lapse of the paper sheet time interval between forms (time slit B), a part of the toner layer during the previous copying is left on the developing roller if left as it is. Accordingly, during the time zone C after the lapse of the time interval between forms (time slit B) until the time when the rotational one cycle of the developing roller 2 is completed, the voltage Vdc2 of the magnetic roller is raised, and the toner is supplied. After the rotational one cycle of the developing roller is completed, the magnetic roller application voltage is returned to the value during the normal developing, wherein the magnetic roller application voltage (Vac+Vdc1) is kept constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
