| 摘要 |
PROBLEM TO BE SOLVED: To provide a planetary gear device which is excellent in dimension stability and has long service life even when it is used under high temperature, high speed, high load conditions.SOLUTION: A pinion shaft 15 of a planetary gear device comprises a hardened layer 15a which is constituted by being hardened by high frequency hardening treatment on a rolling surface, surface hardness of the hardened layer 15a is Hv655 or higher, the residual austenite quantity is 12 volume% or more and 50 volume% or less. A needle roller 16 comprises a hardened layer which is constituted by being hardened by carbonitriding treatment on a rolling surface, surface hardness of the hardened layer is Hv752 or more, and the residual austenite quantity is 5 volume% or more and 45 volume% or less. An Si-Mn-based nitride is deposited onto the hardened layer of the needle roller 16. A residual austenite quantity γRa and a diameter Da of the hardened layer of the pinion shaft 15, and a residual austenite quantity γRb and a diameter Db of the hardened layer of the needle roller 16, satisfy a formula of γRa+2×(Db/Da)×γRb≤69. |
