Patent ID: 6884827

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; metal powder having a hardness equal to or more than that of any of a side surface of the seal ring groove serving as a sliding partner and an inner circumferential surface of a housing engaged relatively rotatable with the outer circumference of the shaft member; and modified fluororesin formed by irradiating 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, 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 when oil pressure is applied to the seal ring, the outer ring circumferential surface is pressed against the inner circumferential surface of the housing, one of the side ring surfaces is pressed against the side surface of the seal ring groove, thus retaining the oil pressure.