Internal combustion engine

An internal combustion engine comprising:

• a cylinder head having an inner wall;
• a spark plug arranged at a central portion of the inner wall of said cylinder head;
• an air blast valve arranged on a peripheral portion of the inner wall of said cylinder head;
• and
• a piston having a top face having a depression extending from a point beneath said spark plug to a point beneath a tip portion of said air blast valve, said air blast valve injecting fuel together with pressurized air toward said depression in the form of a conical shaped spray of fuel at the compression stroke of the engine to direct said conical shaped spray of fuel toward said depression beneath said spark plug along a bottom wall of said depression, a longitudinal width of said depression in the moving direction of said conical shaped spray of fuel being larger than a transverse width of said depression in the direction perpendicular to the moving direction of said conical shaped spray of fuel, opposing side walls of said depression, which define said transverse width, being positioned slightly outward from a side face of said conical shaped spray of fuel.