Control system of compression-ignition engine

A control system of a compression-ignition engine, comprising:

• an engine configured to cause combustion of a mixture gas inside a combustion chamber;
• an injector attached to the engine and configured to inject fuel into the combustion chamber;
• a pressure sensor configured to detect a pressure inside the combustion chamber;
• a spark plug disposed to be oriented into the combustion chamber and configured to ignite the mixture gas inside the combustion chamber;
• and
• a controller, operatively connected to the injector and the spark plug, comprising a processor configured to operate the engine by outputting a control signal to the injector and the spark plug, respectively, wherein
• after the spark plug ignites the mixture gas to start combustion, unburned mixture gas combusts by self-ignition,
• the controller outputs the control signal to the injector so that a fuel injection timing is more advanced when the engine operates at a high engine speed than at a low engine speed that is lower than the high engine speed,
• the controller sets a self-ignition (SI) ratio to be lower than 100% in accordance with SPCCI (Spark Controlled Compression Ignition) combustion, in which spark ignition combustion and compression ignition combustion are combined, and higher at the high engine speed than at the low engine speed, the SI ratio being a ratio of a heat amount generated when the ignited mixture gas combusts through flame propagation with respect to a total heat amount generated when the mixture gas inside the combustion chamber combusts, and
• the controller adjusts a timing of the ignition of the mixture gas by the spark plug such that an actual SI ratio approaches a target SI ratio when the controller determines that the actual SI ratio is deviated from the target SI ratio based on detection signals from the pressure sensor.