| 摘要 |
PROBLEM TO BE SOLVED: To prolong the service life of a light deflector by preventing dusts from entering and accumulating into a dynamic pressure generating groove. SOLUTION: A rotating body 42 has a rotating polygon mirror 32 and a rotary shaft 38 and a cylindrical sleeve 44 whose lower end is sealed is arranged on the side of the outer periphery of the rotary shaft 38. Lubricating oil is filled in a clearance between the sleeve 44 and the rotary shaft 38. A herringborn-like dynamic pressure generating groove 48 is provided in the inner peripheral part of the sleeve 44 and the dynamic pressure generating groove 48 forms a radial bearing part 50 for supporting the rotary shaft 38 in the radial direction. A dynamic pressure generating groove 54 for separating lubricating oil; being liable to be deteriorated, around the upper end part of opening of the sleeve 44 from lubricating oil around the radial bearing part 50 by rotating the rotary shaft 38; is provided on the inner peripheral surface of the sleeve 44. |
