To provide long-service-life structure, by suppressing abrasion of an outer circumferential face of an intermediate part of a roller support shaft 9 even in lubricating environment using lubricating oil into which insoluble components such as soot or the like are mixed.
The roller support shaft 9 is made of iron alloy containing, in total, 1.0 to 20.0 wt.% of Cr, Mo, V, and W, and containing, in total, 0.5 to 1.2 wt.% of C and N. After nitriding a surface, induction hardening is performed on needles 13, and the outer circumferential face of the intermediate portion in rolling-contact with the needles 13. Hardness of the outer circumferential face of the intermediate portion is enhanced by the constitution, resulting in solving the above problem.
YAMAMURA KENJI
Nakai Shun
Kinzo Koyama
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