Patent ID: 8747272

Claim:
A planetary gear system comprising: a sun gear having external teeth; a ring gear having internal teeth; at least one planet gear having, at its outer circumferential face, external teeth and an annular groove, the external teeth being meshed with the external teeth of the sun gear and the internal teeth of the ring gear and being formed of a pair of sets of teeth aligned in an axial direction, the annular groove being formed between the pair of sets of teeth; a fixed support shaft provided for each of the at least one planet gear and configured to rotatably support the planet gear via a bearing, the bearing including a pair of rolling element rows aligned in the axial direction; an oil supply path through which lubricating oil is supplied, at an inner side of the planet gear, to the pair of rolling element rows; and an oil discharge path which extends through the planet gear and through which the lubricating oil is discharged to the annular groove from space between the pair of rolling element rows which are provided at the inner side of the planet gear.