| 摘要 |
A ball screw device comprises a screw shaft, a nut externally mounted on the screw shaft, and a multiplicity of balls interposed between thread grooves of the screw shaft and the nut. The screw shaft has a ball circulation groove for coupling downstream and upstream sides of the thread groove so that the balls are returned from the downstream side to the upstream side and thereby circulated in the thread groove of the screw shaft. The ball circulation groove has such a curved shape as to sink radially inward in an intermediate region in a rolling direction of the balls and has a curved shape protruding radially outward in both end regions, and is configured in the manner that the centrodes of the balls rolling in the both end regions and the balls rolling in the thread groove of the screw shaft satisfy predetermined conditions with respect to circulation of the balls. <IMAGE> |
