| 摘要 |
PURPOSE: To control the displacement of a rotary polygon mirror caused by the generation of local negative pressure at the inside of a cover member by providing a guiding member guiding atmosphere at the inside of the cover member to the inside of the radial direction of the rotary polygon mirror. CONSTITUTION: The top plate 9c of a cover 9 possesses plural guide blades 10 projecting toward the upper surface of the rotary polygon mirror 1, and they are disposed in the peripheral direction of the rotary polygon mirror 1 at equal intervals. Respective guide blades 10 are constituted so as to guide a part of air flowing from the center part to the outer peripheral part of a rotating rotary polygon mirror 1 back to the center part of the rotary polygon mirror 1. Then, a large amount of outdoor air sucked in the inside of the cover 9 from a window 9a by the rotation of the rotary polygon mirror 1 cools a stator coil 8 and flows along the outer peripheral part of the rotary polygon mirror 1 and flows out again from the window 9a. At this time, an air flow flowing from the outer peripheral part of the rotary polygon mirror 1 inward in an radial direction of the rotary polygon mirror 1 is generated along the guide blade 1 at the top of the cover 9, so that the center of the top of the cover 9 is prevented from becoming an evacuated state. |
