Controller and control method for internal combustion engine

A controller for internal combustion engine, comprising at least one processor configured to implement:

• an angle information detector that detects a crank angle, a crank angle speed, and a crank angle acceleration, based on an output signal of a crank angle sensor;
• an actual shaft torque calculator that calculates an actual shaft torque applied to a crankshaft, based on a detection value of the crank angle acceleration, and an inertia moment of a crankshaft system, at each crank angle of arithmetic object;
• and
• a gas pressure torque calculator that,
• by referring to a specific unburning condition data in which a relationship between a crank angle and a shaft torque in unburning of a specific operating condition is set, calculates the shaft torque in unburning of the specific operating condition corresponding to each crank angle of arithmetic object;
• calculates a generated torque of unburning assumption of the specific operating condition which is a torque generated by a gas pressure in cylinder and a reciprocating movement of piston when assuming that it is the specific operating condition and it is unburning, using a physical model equation of a crank mechanism, at each crank angle of arithmetic object;
• calculates a generated torque of unburning assumption of a current operating condition which is a torque generated by the gas pressure in cylinder and the reciprocating movement of piston when assuming that it is unburning in the current operating condition, using the physical model equation of the crank mechanism, at each crank angle of arithmetic object;
• calculates a shaft torque in unburning of the current operating condition, by correcting the generated torque of unburning assumption of the current operating condition based on the shaft torque in unburning of the specific operating condition, and the generated torque of unburning assumption of the specific operating condition, at each crank angle of arithmetic object;
• calculates an external load torque which is a torque applied to the crankshaft from an outside of the internal combustion engine, based on the shaft torque in unburning and the actual shaft torque of the current operating condition which were calculated at a crank angle in a vicinity of a top dead center of a combustion stroke;
• and
• calculates an increment of gas pressure torque by burning which is included in a gas pressure torque generated by the gas pressure in cylinder, based on the shaft torque in unburning of the current operating condition, the actual shaft torque in burning, and the external load torque, at each crank angle of arithmetic object.