| 摘要 |
PROBLEM TO BE SOLVED: To highly accurately detect in a short time rotation phase differences between a plurality of image carriers of an image forming apparatus that forms a color image by superimposing toner images formed on the corresponding image carriers, while rotating the image carriers such that at least one or more of the image carriers are connected to corresponding drive motors rotated at predetermined target rotating speeds. SOLUTION: Four phase marks MK1 to MK4 are put on the outer peripheral part of a photoreceptor gear 54 at regular intervals, almost 90°. The phase marks MK1 to MK4 are detected by an angle detector 56, so that the angular position of the photoreceptor gear 54 and that of a photoreceptor drum 20 are detected in a rotating direction D20. This makes it possible to detect the absolute angular positions of the photoreceptor gear 54 and photoreceptor drum 20 at an interval of about 90°based on an output signal from an angle detector 56 without rotating the photoreceptor gear 54 and photoreceptor drum 20 one time. COPYRIGHT: (C)2006,JPO&NCIPI
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