| 摘要 |
PURPOSE:To eliminate windage loss and turbulence and reduce load capacity and to obtain a scanner which has no irregularity of rotation by sealing the gap between a polygon mirror and a bearing with a seal and evacuating a space part where the polygon mirror is arranged into a vacuum. CONSTITUTION:The polygon mirror 50 is fitted to the flange part 20a of a shaft body 20 and the seal 16 is provided between the polygon mirror 50 and bearing 21 to prevent air which contains impurities such as lubricating oil from entering the space part 11. Further, an exhaust passage is formed of the air vent 26, radial air vent 27, and air vent 13 of the shaft body 20. When a vacuum pump is connected with the air vent 14 and put in operation, the space part 11 where the polygon mirror 50 is provided is evacuated through said exhaust passage. Consequently, there is a little windage loss even when the polygon mirror 50 rotates, no turbulence is generated to reduce the motor load, and the scanner having no irregularity of rotation is obtained. |
