Method of manufacturing resin silencer and resin silencer

A method of manufacturing a resin silencer to be connected to piping of an air conditioner for a vehicle, the method comprising:

• forming, via resin injection molding,
• an insertion-side component comprising an annular circumferential rib disposed protruding from an outer circumferential surface of a barrel portion having a cylindrical shape, an insertion portion on one end portion in an axial direction of the barrel portion, and a pipe portion with a smaller diameter than the barrel portion connected to the other end portion in the axial direction via an expanded pipe portion expanded in diameter toward the barrel portion and
• a receiving-side component comprising an annular circumferential rib disposed protruding from an outer circumferential surface of a barrel portion having a cylindrical shape, a receiving portion into which the insertion portion is inserted on the other end portion in an axial direction of the barrel portion, and a pipe portion with a smaller diameter than the barrel portion connected to one end portion in the axial direction via an expanded pipe portion expanded in diameter toward the barrel portion;
• the receiving portion comprising an annular groove into which the cylindrical insertion portion is inserted and a cylindrical flow stopping wall portion connected to an outer circumferential side of the annular groove with a gap,
• joining the barrel portion of the insertion-side component and the barrel portion of the receiving-side component to make an integrally formed cylindrical portion by causing a leading edge surface of the insertion portion inserted into the annular groove to be brought into contact with and pressed against a bottom surface of the annular groove, bringing an outer circumferential surface of the insertion portion into contact with an outer circumferential wall of the annular groove, putting an inner circumferential surface of the insertion portion and an inner circumferential wall of the annular in a non-contact state with a gap therebetween, and rotating the insertion-side component and the receiving-side component relatively about an axial center to spin weld a contact portion between the insertion portion and the annular groove.