| 摘要 |
PROBLEM TO BE SOLVED: To ensure durability while ensuring allowable moment load, without enlarging a rotation support part. SOLUTION: Surfaces of an inner ring 9d, an outer ring 10d and each ball 13 are hardened by nitriding. A dimensional stabilizing process is applied to the inner ring 9d and the outer ring 10d, and grease having an excellent seizure resistance is sealed into an annular space 17. A depth of an inner ring track 11d and a depth of an outer ring track 12d are secured so as to be deeper than predetermined, and curved parts or chamfering parts are formed at both end edges of each of the tracks 11d and 12d.
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