| 摘要 |
PROBLEM TO BE SOLVED: To obtain a ball screw which is high in work efficiency at a forward operation, and low in the work efficiency at a revere operation by a method which is lower in manufacturing cost than a ball screw which is described in a patent literature 1.SOLUTION: During operations, a plurality of balls 3 contact with a load circular arc face of a screw shaft 1, a load circular arc face of a nut 2 and a non-load circular arc face of the screw shaft 1 or the nut 2 at points Cs, Cn and C3, respectively. Out of four circular arcs which are composed of two circular arcs 11a, 11b forming a spiral groove 11 of the screw shaft 1, and two circular arc faces 21a, 21b forming a spiral groove 21 of the nut 2, the surface roughness of the circular arc face 11a being the non-load circular arc face with which the balls 3 contact at a reverse operation is set higher than the surface roughness of the circular arc face 21b being the non-load circular arc face with which the balls 3 contact at a forward operation.SELECTED DRAWING: Figure 3 |
