| 摘要 |
PURPOSE:To apply high rigidity to a spindle from low speed rotation to high speed rotation by limiting the moving quantity of bearing box for pressing a bearing in axial direction and that of an intermediate ring by means of an adjusting member so as to adjust a pre-load quantity and applying fixed position pre-load in response to the number of revolution of a main shaft. CONSTITUTION:The sum of the initial gaps of four bearings 12, 13, 14, 15 is indicated as delta1 (The pre-lood sum at the time of the maximum speed operation), a gap between the step portion 26 of an adjusting member 25 and the step portion 28 of a bearing box 19 is indicated as delta2, a gap between the step portion 27 of the adjusting member 27 and an intermediating ring 20 is indicated as delta3, and the relation thereof is made to safil delta2 > delta3 > delta1. When the rotation of a main shaft 11 is in a low speed area, pressure is applied to a hydraulic chamber 21 so as to move the bearing box 19 until the step portions 26 and 28 are abutted to each other so that pre-load quantity due to position becomes delta2 - delta1 and the number of revolution is increased in increase the pre-load quantity.When the number of revolution reaches a certain value, oil in the hydraulic chamber 21 is discharge, pressure is applied to a hydraulic chamber 22 to force the intermediate ring 20 about to the step portion 27 so that the pre-load quantity becomes delta3 - delta1 fall, and when the number of rolation is increased further, the pre-load is increased, and when the number of rotation is increased moreover, and oil in the hydraulic chamber 22 is discharged, the pre-load quantity due to position becomes - delta1 to fall. When the number of revolution is increased moreover the pre-load quantity is increased. |
