| 摘要 |
PURPOSE:To prevent the wear of a shaft hole by using dynamic pressure gas bearings and a static pressure gas bearings for supporting a carriage, and operating the static pressure gas bearings when the rotating speed of the shaft which constitutes one of the dynamic pressure gas bearings has assumed a predetermined value. CONSTITUTION:Air inlet ports for the static pressure gas bearing are provided in the carriage 3. These air inlet ports 17 communicate with minute gas between the shaft 7 and the support sleeves 6. The shaft 7 rotates by a driving motor 11, and the carriage 3 is driven in the direction of an arrow B while being supported by the dynamic pressure gas bearings when the shaft 7 is in a state of reaching a predetermined rotating speed. On the other hand, when the rotating speed of the shaft 7 is less than the predetermined value, the static pressure bearings are operated. That is, the rotating speed of the shaft 7 discriminates the rotating speed of the motor 11 by operating an air valve driving circuit, and compressed air is supplied from the air inlet ports 17 to the gaps between the shaft sleeves 6 and the shaft 7 to thereby support the carriage 3 by air pressure. |
