| 摘要 |
PROBLEM TO BE SOLVED: To provide a pinion shaft in a radial needle bearing used for a pinion gear in a planetary gear mechanism of an automobile automatic transmission in which plastic deformation is hard to occur. SOLUTION: The radial needle bearing 1 is suitably used for a pinion gear in a planetary gear mechanism of an automobile automatic transmission, and comprises: outer rings 2; a pinion shaft 3; and a plurality of rolling elements 4 arranged between the outer ring 2 and the pinion shaft 3 so as to freely turned. The pinion shaft 3 is composed of steel comprising, by mass, 0.4 to 1.5% silicon, and is further provided with: a core part 3b with the content of retained austenite of 0 volume%; and a surface layer parts 3a arranged around the core part 3b. The surface hardness of each surface layer part 3a is≥700 Hv, the content of retained austenite in the surface layer part 3a is 15 to 50 vol%, and the residual compressive stress therein is 400 to 1,200 MPa. COPYRIGHT: (C)2007,JPO&INPIT
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