Patent ID: 7523849

Claim:
An ultrasonic welding method comprising: an arranging process for arranging a horn unit at a side of a flange portion of a first member so that the horn unit and a second member are respectively positioned at two opposite sides of the flange portion, the flange portion being positioned at an end of the first member, the horn unit including a first horn member and a second horn member which are separate from each other in a circumferential direction of the flange portion at division surfaces of the first horn member and the second horn member; a moving process for moving the first horn member and the second horn member into contact with each other, and a joining process for vibration-exciting the flange portion while pressurizing the flange portion toward an end portion of the second member at pressure-applying surfaces of the first horn member and the second horn member so that the flange portion of the first member is joined to the end portion of the second member at a joining surface, the joining process being performed in such a state that the first horn member and the second horn member are pressed against each other at the division surfaces thereof, wherein: in the arranging process, each of the first horn member and the second horn member is slantways arranged in such a manner that a part of the pressure-applying surfaces thereof which is nearer to the division surfaces thereof is nearer to the joining surface; and in the joining process, the pressure-applying surfaces of the first horn member and the second horn member are disposed to be substantially parallel to the joining surface due to a pressure-applying reaction force, and a vibration of the first horn member is transferred to the second horn member through the division surfaces which are pressed against each other.