Patent ID: 7444981

Claim:
An internal-combustion engine comprising: a cylinder block having a plurality of cylinder bores generally aligned along a first axis to form a row of cylinders; a plurality of pistons, each of the pistons being received in a respective one of the cylinder bores; a cylinder head coupled with the cylinder block and cooperating with the cylinder bores and pistons to form a combustion chamber in each of the cylinders, the cylinder head being formed with an inlet path and an outlet path opening into the combustion chamber; a pair of inlet valves and a pair of outlet valves disposed within the combustion chamber; a first ignition plug disposed in the cylinder bead within a generally central area of the combustion chamber in plan view; and second and third ignition plugs disposed in the cylinder head at opposite peripheral portions of the combustion chamber positioned approximately along the first axis direction in plan view; the second and third ignition plugs being arranged so that discharge electrode portions of the second and third ignition plugs are inclined inwardly of the combustion chamber in opposite directions; the discharge electrode portions of the second and third ignition plugs being disposed substantially symmetrical relative to the first ignition plug in plan view, a line intersecting the discharge electrode portions of the second and third ignition plugs forming an oblique angle with the first axis of the row of cylinders in plan view.