| 摘要 |
PURPOSE:To prevent oil mist from sticking on the reflecting mirrors of a polygon mirror by chamfering the 1st corner part between the flank and peripheral surface of the tip part of a rotary shaft. CONSTITUTION:The polygon mirror 14 is so constituted that the 1st corner (corner part 15) between the end surface 14A on the tip part of the rotary shaft and the flank where a reflecting mirror 12 is formed is chamferred. A swivel flow in a radiation direction is slanted toward a motor 18. Namely, the air resistance is reduced at the corner part 15 which is chamferred and becomes smaller than the air resistance at a corner part 17 which is not chamferred. The air speed is faster at this corner part 17 and a pressure difference is generated vertically across the reflecting mirror surface 12. Consequently, no oil mist reaches the part above the motor-side end surface of the polygon mirror 14. |
