Control device for compression self-ignition engine

A control device for a compression self-ignition engine, comprising:

• an engine having a combustion chamber operable to combust an air-fuel mixture, an injector operable to inject fuel to supply the fuel into the combustion chamber, and a spark plug operable to ignite the air-fuel mixture in the combustion chamber, the engine configured to cause the air-fuel mixture in the combustion chamber to be self-ignited in association with the spark ignition of the spark plug;
• and
• a controller configured to control at least the injector and the spark plug to control an operation of the engine,
• wherein the engine performs a first combustion in which the air-fuel mixture is combusted due to a flame propagation triggered by a spark ignition of the spark plug, and a second combustion in which the air-fuel mixture is combusted due to a self-ignition induced by the flame propagation,
• wherein the controller comprises a processor configured to:
• control a SI ratio serving as an index relating to a ratio of a heat amount generated in the first combustion with respect to a total heat amount generated in the first and second combustions or a heat amount generated in the second combustion, based on an operating state of the engine and during each combustion cycle of the engine;
• and
• control an initial in-cylinder temperature which is an internal temperature of the combustion chamber before a start of the first combustion, based on the operating state of the engine and during each combustion cycle of the engine, and
• wherein the controller is configured to change combustion states of both the first and second combustions by controlling both the SI ratio and the initial in-cylinder temperature according to the operating state of the engine, during each combustion cycle of the engine.