Patent ID: 7267116

Claim:
An ignition apparatus having a spark plug comprising: a mounting bracket to be mounted to an internal combustion engine; a center electrode insulatedly-supported by the mounting bracket, one end of which being a cylindrical form and exposedly extending from one end of the mounting bracket; and only a single earth electrode, said single earth electrode having one end coupled with the one end of the mounting bracket and having another end including one surface formed to face to the one end of the center electrode, the one surface having a cylindrical protrusion secured thereon and extending toward the center electrode so as to face the one end of the center electrode, a spacing formed between the one end of the center electrode and the protrusion of the earth electrode and formed to serve as a discharge gap, both of the one end of the center electrode and the protrusion of the earth electrode being 2.3 mm or less in diameter to keep an amount of ignition energy supplied to the spark plug below 17 mJ.