| 摘要 |
PROBLEM TO BE SOLVED: To prevent noise from being generated by a rotary polygon mirror which rotates fast by a simple structure by exhausting a housing, which is formed of a transparent member and fitted on the rotary shaft side of a rotary motor and stores the polygon mirror, in synchronism with the rotation of the rotary motor. SOLUTION: The polygon mirror 1 which is driven by the rotary motor 2 is stored in the sealed housing 3 formed of the transparent member. As the rotary motor 2 rotates, the rotary shaft 1 rotates and the polygon mirror 1 also rotates. The air in the housing 3 flows by the rotation of the rotary shaft 21 and polygon mirror 1 and passes through an exhaustion groove 22 formed in the tip part of the rotary shaft 21 to push up an exhaust valve 5; and the air in the housing 3 is thus discharged and the pressure in the housing 3 drops to produce vacuum. Thus, the vacuum is produced in the housing 3 and then turbulence caused by the rotation of the polygon mirror 1 is not generated to prevent noise from being generated even when the polygon mirror 1 rotates fast. |
