Patent ID: 7572839

Claim:
A seal ring which seals operating oil hermetically and is attached to an annular seal ring groove provided on an outer circumference of a shaft member, the seal ring comprising: fluororesin; modified fluororesin formed by being irradiated with an ionizing radiation in a range from 1 kGy to 10 MGy inclusive in a state of being heated up to a melting point thereof or higher under an inert gas atmosphere with an oxygen partial pressure of 1.33 kPa or less; and synthetic resin having a surface energy ranging from +0 N/cm to 20×10 −5 N/cm inclusive of that of an operating oil, wherein the seal ring comprises an inner ring circumferential surface facing an inside thereof in a radius direction, an outer ring circumferential surface facing an outside thereof in the radius direction, and a pair of side ring surfaces facing both sides thereof in an axial direction, and wherein when oil pressure is applied to the seal ring, the outer ring circumferential surface is pressed against an inner circumferential surface of a housing, and one of the pair of side ring surfaces is pressed against a side surface of the seal ring groove, thus retaining the oil pressure.