| 摘要 |
PROBLEM TO BE SOLVED: To enhance a feed rate. SOLUTION: A ball circulating path 21 is formed rollably filled with a plurality of balls 22 and communicating an outer loading path 18 formed between a screw groove 16 of a fixed nut 17 ant an outer circumferential side screw groove 14 of a rotary nut 15 with an inner loading path 19 formed between a screw groove 11 of a screw shaft 12 and an inner circumferential side screw groove 13 of the rotary nut 15 and having the same twisting direction and lead as the outer loading path 18 by a ball circulating member 20 in at least two places. A plurality of the ball circulating paths 21 are axially arranged by considering a sum of the number of turns in the outer loading part 18 and the number of turns in the inner loading part 19 of the ball circulating path 21 as one turn. In one row of the ball circulating paths 21, an advancing amount of the plurality of balls 22 in an axial lead direction between the outer loading part 18 and the inner loading part 19 and a returning amount in the axial lead direction via the ball circulating member 20 are set same.
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