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 ( 53 a ) opposing the end of the center electrode in a direction indicated by arrow A parallel to the axis of the plug body. A tip ( 53 b ) of the ground electrode and a tip ( 60 a ) 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 ).
1. A spark plug, comprising:
a plug body;
a center electrode provided on the plug body coaxially with the plug body;
a ground electrode provided on the plug body in a vicinity of the center electrode, and having a portion opposing an end of the center electrode along an axis of the plug body, a tip of the ground electrode intersecting an axis of the plug body and opposing a tip of the center electrode; and
at least one injection control side pole provided on the plug body in the vicinity of the center electrode, a tip of the at least one injection control side pole being separated from the tip of the ground electrode, and the tip of the ground electrode and the tip of the at least one injection control side pole being positioned on substantially the same plane perpendicular to the axis, the ground electrode and the at least one injection control side pole being arranged at substantially regular intervals around the center electrode,
wherein a maximum length of the ground electrode along a center axis of the plug body is substantially the same as a maximum length of the at least one injection control side pole along the center axis, and
a width of the ground electrode along a circumference of the center electrode is substantially the same as a width of the at least one injection control side pole along the circumference of the center electrode.
2. The spark plug according to claim 1 , wherein the at least one injection control side pole includes three injection control side poles.
3. The spark plug according to claim 1 , wherein the at least one injection control side pole has a first wall portion that extends along the axis of the plug body and a second wall portion that extends, in a direction perpendicular to the axis of the plug body and toward the axis of the plug body, from an end of the first wall portion, and
wherein the second wall portion is positioned on substantially the same plane as the tip of the ground electrode.
4. The spark plug according to claim 1 , wherein the at least one injection control side pole is curved towards the axis of the plug body forming a curved surface, and a tip of the curved surface is positioned on substantially the same plane as the tip of the ground electrode.