| 摘要 |
PROBLEM TO BE SOLVED: To provide a planetary gear device having longer service life.SOLUTION: A pinion shaft 15 of a planetary gear device 10 includes a hardened layer 15a which is hardened by a carbonitriding process on a rolling surface. The hardened layer 15a has surface hardness of Hv650 or higher and a residual austenite amount of 20 vol.% or more and 50 vol.% or less. A needle roller 16 has a hardened layer which is hardened by a carbonitriding process on a rolling surface. The hardened layer has surface hardness of Hv750 or higher and a residual austenite amount of 5 vol.% or more and 45 vol.% or less. On the hardened layer of the needle roller 16, an Si-Mn nitride is precipitated, and the amount of the precipitated Si-Mn nitride is 1% or more and less than 10% in terms of an area ratio, and the number of Si-Mn nitride particles having a particle diameter of 0.05 μm or more and 1 μm or less is 100 or more per area of 375 μm. The surface nitrogen concentration of the hardened layer of the needle roller 16 is 0.2 mass% or more. |
