Control device for compression self-ignition engine

A control device for a compression self-ignition 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 compression self-ignition engine configured to cause the air-fuel mixture in the combustion chamber to combust by a self-ignition in association with a spark ignition of the spark plug, the control device comprising:

• a controller configured to control at least the injector and the spark plug to control an operation of the engine;
• and
• a state quantity setting device configured to adjust an introduction of fresh air and burned gas into the combustion chamber of the engine so as to thereby set an inside of the combustion chamber to a desired state, the state quantity setting device selected from the group consisting of an EGR valve, an EGR system, a throttle valve, an air bypass valve, a supercharger, an intake variable valve timing device, and an exhaust variable valve timing device,
• wherein the engine performs a first combustion in which the air-fuel mixture is combusted due to a flame propagation triggered by the spark ignition of the spark plug, and a second combustion in which the air-fuel mixture is combusted due to the self-ignition induced by the flame propagation,
• wherein the controller comprises a processor configured to:
• control a spark ignition (SI) ratio which is 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,
• 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,
• wherein the controller is configured to set a target SI ratio and a target initial in-cylinder temperature before the start of the first combustion each according to the operating state of the engine, and to perform control of adjusting the SI ratio and control of adjusting the initial in-cylinder temperature, so as to attain the target SI ratio and the target initial in-cylinder temperature, and
• wherein the controller is configure d to:
• control the state quantity setting device such that a ratio between fresh air and burned gas to be introduced into the combustion chamber is adjusted so as to attain the target initial in-cylinder temperature;
• estimate an actual initial in-cylinder temperature before the start of the first combustion;
• and
• adjust a spark ignition timing of the spark plug as a function of the actual initial in-cylinder temperature, to thereby attain a self-ignition timing according to the target SI ratio and the target initial in-cylinder temperature.