To reduce the cost without impairing the reliability by sufficiently securing the pressing fixing force of a circulation top by a strip-shaped retaining ring even in a case when a large and thin nut is used.
In this internal circulation-type ball screw device comprising the circulation top 28 fitted and fixed to a fitting hole 27 formed on an outer peripheral part of the nut 26 to form a ball circulation groove 28a for infinitely circulating a ball 25 rolling on a load orbit between a thread groove 22 of a screw shaft 23 and a thread groove 24 of the nut 26, a strip-shaped circumferential groove 29 is formed on an outer peripheral face of the nut 26 in a communicated state with the fitting hole 27, an engagement groove 30 deeper than the circumferential groove 29 is formed, an approximately C-shaped strip-shaped retaining ring 40 is mounted on the circumferential groove 29, and both circumferential end parts of the strip-shaped retaining ring 40 are engaged with the engagement groove 30 in a state of being bent inward, whereby the circulation top 28 is fixed to an outer peripheral part of the nut 26.
Yoshiaki Naito
Cui Shu Tetsu
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