Control apparatus for engine

A control apparatus for an engine, the control apparatus comprising:

• the engine having a combustion chamber;
• a throttle valve disposed in an intake passage and configured to adjust an amount of fresh air introduced into the combustion chamber;
• an Exhaust Gas Recirculation (EGR) system comprising an EGR passage connecting an exhaust passage and the intake passage of the engine, and an EGR valve configured to adjust an amount of EGR gas introduced into the combustion chamber;
• a supercharging system comprising a bypass passage, an air bypass valve disposed in the bypass passage, and a supercharger provided in the intake passage downstream of the throttle valve and downstream of a connecting portion of the intake passage connecting the EGR passage with the intake passage;
• a spark plug disposed so as to face an inside of the combustion chamber, the spark plug configured to ignite air-fuel mixture in the combustion chamber;
• and
• a controller connected to the spark plug, the air bypass valve, the EGR valve, and the throttle valve, the controller configured to output a control signal to the spark plug, wherein
• after the spark plug ignites the air-fuel mixture to start combustion, unburned air-fuel mixture is combusted by autoignition,
• the controller changes, according to an operation state of the engine, a heat amount ratio that represents an index associated with a ratio of an amount of heat generated by air-fuel mixture being combusted by flame propagation, to a total amount of heat generated by air-fuel mixture in the combustion chamber being combusted, and
• the controller adjusts a temperature within the combustion chamber by changing an opening degree of the air bypass valve of the supercharging system, an opening degree of the EGR valve, and an opening degree of the throttle valve in accordance with the operation state of the engine.