Patent ID: 8171961

Claim:
A plug structure for sealing an opening end portion of a fluid passage being circular in cross-section and formed in a housing, the structure comprising: a plug being equal in resistance against deformation to, or smaller than the housing, and having a circular column portion and an annular flange portion formed on an end portion of the circular column portion; a flange pressure-contacting portion of the opening end portion deformed to be pressure-contacted with a lower surface of the annular flange portion of the plug, wherein a part around the annular flange portion of the opening end portion is deformed with the plug fitted at the circular column portion in the fluid passage and engaged at the annular flange portion with the opening end portion; a contracted diameter portion having a shape made to be gradually narrow in the middle in which the circular column portion of the plug is deformed by the fluid passage which is contracted in diameter with the deformation of the part around the annular flange portion of the opening end portion; and a deformed circumferential portion at a circumferential edge of the annular flange portion of the plug, the deformed circumferential portion being deformed to be pressure-contacted with the flange pressure-contacting portion of the opening end portion.