| 摘要 |
PURPOSE:To reduce the number of parts, facilitate assembling work and improve durability by setting the outer diameter of the thrust bearing face formed of the end face of a supporting shaft to be specific times longer than the length of the radial bearing face of a rotor. CONSTITUTION:In this dynamic pressure bearing structure, the end face of a supporting shaft 5 is formed into a thrust bearing face, and the outer diameter of the thrust bearing face of the supporting shaft 5 is set to be two to five times longer than the length of the radial bearing face of a rotor 7. The rotation of the rotor 7 in the specified direction is started by the mutual action between the magnetic field generated to each coil 12 on the basis of the current application control of each coil 12 and the magnetic field of a magnet 10. In association with this rotation, air in a case 1 is forcibly led in between the supporting shaft 5 and the rotor 7 through air lead-in grooves 16, 17 to form an air bearing. Then the rotating speed of a polygon mirror 8 on the rotor 7 is increased and kept to the specified rotating speed, so that the upper end face area of the supporting shaft 5 is enlarged to support the whole rotor 7 stably through a thrust bearing body 14. |
