Combustion control method and combustion control apparatus for gasoline engine for performing combustion

摘要

PROBLEM TO BE SOLVED: To suppress NOx generation while performing HCCI combustion in a high load region.SOLUTION: Fuel containing at least gasoline is injected from a fuel injection valve 10. A piston crown surface is formed along a ceiling surface of a combustion chamber, a recess is formed at an upper surface central part of the piston, and a geometrical compression ratio is set to 15 or more. In an engine high load region, fuel is injected in at least an intake stroke, the fuel in the recess is subjected to compression self-ignition at a compression top dead center or immediately before the compression top dead center, and the ignition of the fuel other than the fuel in the recess is retarded from the compression self ignition to establish a combustion form in which the first peak of heat generation rate of the combustion generating torque is at a piston lowering timing of an expansion stroke, and then the heat generation rate increases again after the passage of a duration in which the heat generation rate does not increase.