Self-igniting engine

In a self-igniting possible range, both intake and exhaust valves (6),(7) are placed in a closure condition for a period from the end of an exhaust stroke and the beginning of an intake stroke for establishing a negative overlap period in which a residual gas is pressurized to increase its temperature, thus raising the air-fuel mixture temperature in a combustion chamber (3) up to a compression ignition possible temperature. In addition, when a crank angle reaches a predetermined crank angle in the first half of an intake stroke, a fuel is injected from an in-cylinder injector (11) into the combustion chamber (3). This fuel injected becomes a premixed air-fuel because of being evaporated by the gas temperature in the combustion chamber (3), and on shifting to a compression stroke afterwards, the temperature in the combustion chamber (3) reaches the compression ignition possible temperature.