Patent ID: 7306502

Claim:
A method of producing a spark plug including (a) a metal shell, and (b) a center electrode which is disposed within said metal shell with a top portion thereof projecting from said metal shell and has a noble metal chip laser-welded to the top portion, (c) a ground electrode having a first end portion, a second end portion, and a middle portion between the first and second end portions, the first end portion being welded to said metal shell, the second end portion having a center electrode-opposed surface on which a noble metal chip is laser-welded, the middle portion being bent to have the noble metal chip face the noble metal chip of said center electrode through a spark gap, said method comprising: welding said ground electrode to said metal shell; placing the noble metal chip on the center electrode-opposed surface of said ground electrode; radiating laser beams to an interface between the noble metal chip and the center electrode-opposed surface of said ground electrode to produce fused portions which create welds between the noble metal chip and said ground electrode and are formed by materials of said ground electrode and said noble metal chip melted together; and bending said ground electrode to have the noble metal chip face the noble metal chip on said center electrode through a spark gap, wherein laser radiation paths along which the laser beams are radiated are located outside the angle θ 1 , angle θ 1 being defined as the angle between lines extending from the noble metal chip on said ground electrode, before it is bent, in a plane of the center electrode-opposed surface of the ground electrode to respective edges of said metal shell opposed in a widthwise direction of said metal shell, wherein adjacent two laser path projected lines, each defined as a line made by projecting a respective laser radiation path onto a plane extending over the center electrode-opposed surface of said ground electrode, before it is bent, make an angle θ 3 , and the angle θ 3 is greater than the angle θ 1 .