Patent ID: 8567792

Claim:
A gas seal structure for use with a gas having a high permeability with respect to a rubber material, the gas seal structure comprising: a main seal means that is made of the rubber material and is disposed between two seal surfaces; a sub-seal means that is made of resin and is disposed between the two seal surfaces, the sub-seal means being located closer to a higher-pressure region than the main seal means and being provided with a concave groove, the higher-pressure region arranged to receive the gas having a high permeability with respect to a rubber member, such that the sub-seal means is positioned to be exposed to the gas; and a pressure variation reducing means comprising a variation reducing space connected only to a gap located between the main seal means and the sub-seal means, the pressure variation reducing means and the gap located between and defined by the two seal surfaces, the variation reducing space being closed by the main seal means and the sub-seal means such that the variation reducing space is disconnected from atmosphere; and the variation reducing space being formed by a concave portion formed in one of the two seal surfaces, the variation reducing space and the gap each having a volume, and wherein the volume of the variation reducing space is larger than the volume of the gap formed between the two seal surfaces.