Dual spark plug ignition internal combustion engine

An internal combustion engine including a cylinder block having therein a cylinder in which a piston is reciprocally movably disposed, comprising:

• a cylinder head secured at its flat surface to the flat surface of the cylinder block and formed with a concavity, the surface of the concavity closing one end of the cylinder and defining a combustion chamber between the concavity surface and the crown of the piston;
• two spark plugs secured to the cylinder head such that the midpoints of the spark plug gaps formed between the center and side electrodes thereof project and lie in the combustion chamber and lie generally opposite to each other with respect to the center axis of the cylinder, the midpoint of the spark plug gap of each spark plug being located at a first predetermined distance from the extension of the first surface of said cylinder head in the direction of the center axis of the cylinder;
• intake and exhaust valve seats embedded in the concavity surface of said cylinder head, said intake valve seat having an annular surface which is exposed to the combustion chamber, the center of said intake valve seat which lies on the extension of the annular surface being located at a second predetermined distance from the extension of the flat surface of said cylinder head in the direction of the cylinder center axis, the second predetermined distance being in the range of from slightly larger to smaller than the first predetermined distance;
• intake and exhaust valve heads respectively seatably disposed on said intake and exhaust valve seats, the centers of said intake and exhaust valve heads which lie on the surfaces exposed to the combustion chamber being located generally opposite to each other with respect to the cylinder center axis;
• and
• means for supplying a portion of the exhaust gases of the engine into the combustion chamber.