| 摘要 |
PURPOSE:To improve the perpendicularity and parallelism of a polygon mirror by interposing a slide member between a rotary body and a support body, enclosing a hollow chamber wherein the polygon rotor is put by the support body and a cover body fitted thereupon, and charging gas which is small in concentration to air in the hollow chamber. CONSTITUTION:The slide member 10 made of a ceramic material where a groove 11 for dynamic pressure generation, i.e. spiral groove is formed is interposed and arranged between the rotary body 3 and support body 4, the hollow chamber 20 wherein the polygon rotor can be interposed is enclosed by the support body 4, the cover body 12 fitted thereupon, and a seal material 23 such as an O ring, charged with the gas which is small in concentration to air, and put in operation under reduced pressure. In this case, helium gas is used as the charged gas. Consequently, the perpendicularity and parallelism of the polygon rotor are improved and the windage loss at the time of rotary operation is reduced greatly to enable fast rotation. |
