| 摘要 |
<P>PROBLEM TO BE SOLVED: To miniaturize a rotational speed detecting device and so to reduce cost. <P>SOLUTION: Large-sized drum driving gears 9Y to 9K whose diameters are made larger than a distance between the rotary shafts of adjacent photoreceptor drums are alternately selected in order of the arrangement of the respective photoreceptor drums 3Y to 3K, are divided to a first drum driving gear group and a second drum driving gear group, and are arranged to be deviated each other in a direction going along drum driving shafts so that the large-sized drum driving gears of the first drum driving gear group and the second drum driving gear group may not interfere with each other and the large-sized drum driving gears of the adjacent photoreceptor drums may be partially superposed. The adjacent two photoreceptor drums are paired, and slit detection parts 13a and 13b for detecting the respective slits of the large-sized drum driving gears are respectively arranged corresponding to parts where the large-sized drum driving gears of the respective pairs are partially superposed. <P>COPYRIGHT: (C)2007,JPO&INPIT |
