| 摘要 |
A space for housing an optical sensor is formed between a detection gear of a drive transfer gear and a frame for supporting the detection gear. A detected part shaped like comb teeth is formed integrally on inner walls of the detection gear. The optical sensor is placed so that the detected part passes through a space between a photo emitter and a photo receptor of the optical sensor. Since the detection gear and the frame protect the optical sensor from stray light and interfering substances such as paper powder, or the like, a high-reliability, small-sized detection mechanism can be provided.
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