A pipe connection portion of a damper case has an opening opened toward the rear side. In an end surface around the opening in the pipe connection portion, a recess is formed in an inner diameter portion. The recess is recessed to the front side as compared to another portion of the end surface. In an end surface of a pipe member, a groove portion is formed in an outer diameter portion. The groove portion is recessed to the rear side as compared to another portion of the end surface. A first seal member and a second seal member are interposed between the end surface of the damper case and the end surface of the pipe member, and the damper case and the pipe member are sealed by the seal members in a liquid-tight manner.