Seal structure and sealing method

A sealing method that uses

• a rotatable rod,
• a housing with an opening through which the rod is to be inserted,
• a seal member arranged between a high-pressure space and a low-pressure space next to each other along an axial direction of the rod inside the housing, the seal member having an inner circumferential portion adjacent to the rod, and
• an annular plate spring that is in contact with the seal member and presses the inner circumferential portion against an outer circumferential surface of the rod, wherein the plate spring is curved along the seal member and contacting the seal member throughout its length until extending past s terminal end of the inner circumferential portion such that an inner circumferential surface of the plate spring projects further toward the low-pressure space than the inner circumferential surface of the seal member in a direction that extends in parallel with the outer circumferential surface of the rod,
• the sealing method comprising:
• in a case in which a pressure inside the high-pressure space is below a reference value, sealing a gap between an outer circumferential surface of the rod and an inner circumferential surface of the opening by maintaining the seal member in a state in which, of the seal member, the inner circumferential portion adjacent to the rod is curved toward the low-pressure space, and in which a sealing surface of the inner circumferential portion in the curved state, the sealing surface facing the rod, is in contact with the outer circumferential surface of the rod, and
• in a case in which the pressure inside the high-pressure space exceeds the reference value, separating the sealing surface from the outer circumferential surface of the rod by pressing the sealing surface of the inner circumferential portion by the pressure inside the high-pressure space.