DYNAMIC PRESSURE BEARING UNIT FOR ROTARY POLYGON MIRROR

摘要

PURPOSE:To prevent the inclination of a reflector surface from being deteriorated due to the accumulation of working accuracy and assembling by rotating a rotor fixing a hollow cylindrical sleeve on its inner periphery and fixing a thrust plate on an upper end face around a shaft fixed on a case. CONSTITUTION:The rotor 13 consists of the hollow cylindrical sleeve 15 fixed on the inner periphery 14a of a rotary polygon mirror 14, the thrust plate 17 fixed on a recessed part formed on the center of the upper end face of the rotary polygon mirror 14 by a screw 16 or the like and a rotor magnet 18 fixed on the lower end face of the polygon mirror 14 and the outer periphery of a cylindrical part 14b extended from the lower end face in the axial direction. When a driving coil is electrified, rotational driving force is generated between the rotor 13 and the rotor magnet 18 and the rotor 13 is driven in the clockwise direction to rotate the rotor 13. Consequently, the inclination of the reflector surface 14a of the polygon mirror 14 from the shaft 12 is removed, cost is reduced and the unit can be thinned.