| 摘要 |
PROBLEM TO BE SOLVED: To prevent a shaft and a sleeve from comming into contact with each other during rotating the rotary polygon mirror at low speed or at high speed. SOLUTION: A shaft 2 rotated integrally with a rotary polygon mirror 1 is provided with dynamic pressure generating grooves 2a, and is journalled by means of dynamic pressure of fluorine-based oil intervening in a microgap A between a sleeve 3 and the shaft itself. Spherical fine grains with a grain size of 20 to 90% of the gap-size of the microgap A are dispersed in the fluoric oil. When the shaft 2 is inclined during rotating the rotary polygon mirror at low speeds or at high speeds, the spherical fine grains function as a rolling bearing. |
