An internal combustion engine having an air blast valve (14) which injects fuel together with pressurized air in the form of a conical shaped spray of fuel. A depression (20) is formed on the top face of the piston (2), and the conical shaped spray of fuel is injected from the air blast valve (14) toward the depression (20). The longitudinal width of the depression (20) in the moving direction of the spray of fuel is larger than the transverse width of the depression in the direction perpendicular to the moving direction of the spray of fuel, and the opposing side walls (20b) of the depression (20), which define the transverse width of the depression (20), are positioned slightly outward from the side face of the conical shaped spray of fuel. <IMAGE>
