US Patent 7812509 Spark plug

A spark plug (10) includes a plug body (51), a center electrode (52), a ground electrode (53) and injection control side poles (61, 62, 63). The ground electrode has an end portion (53a) opposing the end of the center electrode in a direction indicated by arrow A parallel to the axis of the plug body. A tip (53b) of the ground electrode and a tip (60a) of the injection control side poles (61, 62, 63) are positioned in substantially the same plane (71) perpendicular to the axis (C). The ground electrode (53) and the injection control side poles (61, 62, 63) are arranged at substantially regular intervals around the center electrode (52).