Patent ID: 7320769

Claim:
A method for manufacturing a fuel tank welding joint for connecting a fuel tank to a prescribed member, the method comprising: forming a joint main body made of a first resin material configured to be welded to a wall of the fuel tank, the joint main body including (i) a welded edge portion to be thermally welded to the wall of the fuel tank and (ii) a tube portion for connecting a hose, the tube portion having a connecting passage to connect an interior of the fuel tank and the prescribed member; and forming a barrier layer by injecting a second resin material into a cavity of a mold unit in which the joint main body has been set, the second resin material being adhesively and chemically reactive with the first resin material and more fuel-impermeable than the first resin material, wherein forming the barrier layer includes (i) allowing the second resin material to flow through an end of the tube portion into the cavity, so as to form an end portion, and (ii) allowing the second resin material to flow toward the welded edge portion, so as to form a lower end of the barrier layer with a gap from the welded edge portion, and the first resin material includes a modified olefinic resin containing a polar functional group and the second resin material is selected from the group of polyamide and polyacetal, and an injection temperature of the second resin material is higher than that of the first resin material.