| 摘要 |
PURPOSE:To improve support rigidity and suppress oscillations of a main shaft by rotatably supporting the main shaft through a roller bearing, inside a bearing case which is slidably supported through a static pressure bearing, and providing a spring which pressurizes a bearing case sliding surface against a housing sliding surface. CONSTITUTION:A main shaft 32 is driven by a built-in motor and is under a cutting work. A support rigidity of the main shaft 32 is improved because a diametral cutting resistance generated in the main shaft 32 is received by a static pressure bearing 12. Diametral oscillations generated on the main shaft 32 can be eliminated by oil resistance generated when it ties to push aside the oil of the static pressure bearing 12 entered between a bearing case 13 and a housing 11. The oscillations can be also eliminated by a frictional force between sliding surfaces 22 and 23 which is generated when the sliding surface of a bearing case 13 is pressurized against the sliding surface 22 of a stopping ring 20 by means of a coil spring 24. The frictional force also prevents the bearing case 13 from moving over a support center of the static pressurie bearing which may caused by the static pressure bearing. |
