| 摘要 |
PROBLEM TO BE SOLVED: To prevent a photoreceptor drum from being exposed to the outside when an image forming unit is not used and to prevent an electrifying roller from being plastically deformed and the surface thereof from being peeled. SOLUTION: When the drum unit 54 of this image forming unit is not engaged with an optical writing head 67, its upper part is covered with a light shielding cover 58 and a cover for an electrifying roller 59, and an electrifying roller 64 is supported separately from the photoreceptor drum 55 through a rotary shaft 65 by a turning bearing 66 integrated with the cover 59. When the head 67 descends from above and is engaged with the unit 54, the cover 59 and the cover 58 are pressed by the head 67 and opened. Simultaneously, the bearing 66 comes off from the rotary shaft 65 of the roller 64, and the roller 64 abuts on the peripheral surface of the drum 55 by gravity so that it can electrify it. When the unit 52 is disengaged from the head 67, the cover 58 and the cover 59 are closed and the bearing 66 picks up the roller 64.
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