Control apparatus for internal combustion engine

A control apparatus for an internal combustion engine that includes:

• an ignition device configured to ignite an air-fuel mixture in a cylinder;
• a fuel injection device that includes at least an in-cylinder injection valve configured to directly inject fuel into the cylinder;
• and
• an in-cylinder pressure sensor configured to detect in-cylinder pressure,
• wherein the control apparatus is configured to cause the fuel injection device to execute a main injection of fuel in or before an intake stroke and a compression stroke injection of the fuel in a compression stroke to perform a slightly stratified-charge lean-burn operation with a lean air-fuel ratio leaner than a stoichiometric air-fuel ratio, and
• wherein the control apparatus is configured, during the slightly stratified-charge lean-burn operation, to:
• (a) calculate, based on a required torque of the internal combustion engine, a basic total fuel injection amount that should be supplied in a cylinder during one combustion cycle;
• (b) calculate, based on an ignition delay index value, a compression stroke injection amount by the compression stroke injection;
• (c) calculate, as a basic main injection amount of the main injection, a value obtained by subtracting the compression stroke injection amount from the basic total fuel injection amount;
• (d) calculate, based on an output value of the in-cylinder pressure sensor, an actual specified combustion index value of a specified combustion index value that represents a main combustion speed or a combustion fluctuation rate;
• (e) calculate a main injection correction term based on a result of a comparison between a target specified combustion index value or a tolerable specified combustion index value, and the actual specified combustion index value;
• and
• (f) calculate a main injection amount by the main injection by adding the main injection correction term to the basic main injection amount.