Spark plug with Ir-alloy chip

A spark plug comprising:

• a metal shell;
• a center electrode retained within said metal shell to be insulated from said metal shell;
• a ground electrode joined to said metal shell, said ground electrode having a center electrode-facing surface opposed to a tip of said center electrode through a spark plug gap, said ground electrode having a recess formed in the center electrode-facing surface;
• and
• an Ir-alloy chip working to produce a spark between itself and the tip of said center electrode, said Ir-alloy chip being embedded in the center electrode-facing surface of said ground electrode with a portion thereof exposed outside the center electrode-facing surface of said ground electrode, wherein said Ir-alloy chip other than the exposed portion thereof is installed inside said ground electrode, and said Ir-alloy chip is joined to said ground electrode through at least one fuse portion in which materials of said Ir-alloy chip and said ground electrode are melted together, said Ir-alloy chip being fitted within said recess, said fused portion extending continuously from an outer side wall of said ground electrode inside said Ir-alloy chip through an outer side wall of said Ir-alloy chip, the outer side wall of the ground electrode being defined between the center electrode-facing surface of the ground electrode and a surface of the ground electrode opposite the center electrode-facing surface.