| 摘要 |
Provided is a ball screw device having a novel ball circulation structure suitable for a screw shaft with a large lead, optimum for downsizing and weight saving of a nut member, capable of being manufactured at low cost, and capable of exhibiting high reliability even under severe use conditions. In a ball screw device (1) where a screw shaft (2) and a nut member (3) are screwed to each other through an intermediation of a large number of balls (4), a no-load ball path (50) which forms an infinite circulation path for the balls (4) is constituted by a no-load ball groove (33a) spirally formed in an inner peripheral surface of a through-hole (30) of the nut member (3) and by a pair of direction change grooves (34) which communicatively couple a load rolling groove (20a) and the no-load ball groove (33a) to each other so as to complete the infinite circulation path as a closed loop.
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