A control method of an internal combustion engine, the internal combustion engine including an engine body, a fuel injection valve, a spark plug, a characteristic switching mechanism, and an electronic control unit,
- the fuel injection valve being configured to directly inject fuel into a combustion chamber of the internal combustion engine, an electrode portion of the spark plug being disposed in one of the inside of a fuel injection path and the vicinity of the fuel injection path, the characteristic switching mechanism being configured to switch a lift characteristic between a first lift characteristic and a second lift characteristic, the first lift characteristic being a lift characteristic of an exhaust valve of opening the exhaust valve in an exhaust stroke, the second lift characteristic being a lift characteristic of the exhaust valve of opening the exhaust valve in the exhaust stroke and an intake stroke,
- the control method comprising:
- controlling, by the electronic control unit, the fuel injection valve and the spark plug such that fuel is combusted by one of pre-mixture compression ignition combustion and flame propagation combustion;
- switching, by the electronic control unit, the lift characteristic of the exhaust valve to the second lift characteristic in a predetermined first operation range;
- switching, by the electronic control unit, the lift characteristic of the exhaust valve to the first lift characteristic in a predetermined second operation range;
- determining, by the electronic control unit, whether switching failure has occurred;
- performing, by the electronic control unit, homogeneous combustion in the flame ignition operation range when the electronic control unit determines that the switching failure has not occurred;
- and
- performing, by the electronic control unit, spray-guided stratified combustion in the second operation range when the electronic control unit determines that the switching failure has occurred,
- the predetermined first operation range includes at least a part of a compression ignition operation range, the compression ignition operation range is a range in which fuel is combusted by the pre-mixture compression ignition combustion, the predetermined second operation range includes at least a flame ignition operation range, the flame ignition operation range is a range in which fuel is combusted by the flame propagation combustion, the switching failure is failure in which the lift characteristic of the exhaust valve is not switchable from the second lift characteristic to the first lift characteristic by the electronic control unit, the homogeneous combustion is combustion in which fuel homogeneously diffused into the combustion chamber is ignited using the spark plug and is combusted by the flame propagation combustion, and the spray-guided stratified combustion is combustion in which fuel in the fuel injection path is ignited using the spark plug and is combusted by the flame propagation combustion.