| 摘要 |
PURPOSE:To improve the oscillation accuracy of a rotary shaft and the face-inclined rotation accuracy of a polygon mirror by increasing a distance between an upper bearing and a lower bearing and setting up the rotating position of the polygon mirror to be rotated at a high speed on a lower position between the upper and lower bearings. CONSTITUTION:The polygon mirror 48 for reflecting and scanning laser beams is arranged on a shell shape part 44 of the rotary shaft 43 at a position lower than the arranging position of an upper bearing 46 with a fixing tool 50 through a rubber ring 49 or the like. A loose engaging part with the bearing housing 41 side of the lower bearing 47 is pressed with a spring 49 to remove play in the lower bearing 47 and to minimize the rotational vibration of the rotary shaft 43. Since the arrangement distance between the upper and lower bearings 46, 47 for pivoting the rotary shaft 43 can be sufficiently secured in the bearing housing 41 to be a single unit occupying the approximately whole capacity of the rotary mechanism for the optical scanning polygon mirror 48 and the rotational position of the polygon mirror 48 to which centrifugal force is applied at the time of rapid rotation is set up on a low position between the upper and lower bearings 46, 47, the vibration accuracy of the rotary shaft 43 is improved. |
