Internal-combustion-engine control device and internal-combustion-engine control method

A control method of an internal combustion engine, comprising:

• (a) measuring a rotation number of a crankshaft in the internal combustion engine, and estimating a torque of the internal combustion engine from any of an intake air amount, a fuel amount, a thermal efficiency, and an accelerator opening;
• (b) measuring a combustion pressure in a combustion chamber of the internal combustion engine, and calculating an ignition delay period from an ignition timing of an ignition plug to a combustion start timing, and a combustion period from the combustion start timing to a set amount combustion end timing which a set amount of combustion ends, based on the measured combustion pressure in the combustion chamber and the rotation speed of the crankshaft measured in the step (a);
• (c) calculating, using a first calculating means, θPmax which is the crank angle that is the maximum value of the combustion pressure estimation sensor, and θP″max which is the crank angle that is the maximum value of the double derivative of the combustion pressure estimation sensor, and
• (d) calculating, using a second calculating means, ΔθPmax which is the period from the ignition timing by the ignition plug to the θPmax, and ΔθP″max which is the period from the ignition timing by the ignition plug to the θP″max,
• (e) setting an MBT region based on the ΔθPmax and the ΔθP″max, wherein
• the ignition timing of the ignition plug is controlled so as to fall within the MBT region set in the step (e),
• the internal combustion engine further includes:
• a throttle that controls an amount of air supplied to the combustion chamber;
• and
• an injector that injects fuel into an intake pipe that introduces air into the combustion chamber, wherein
• an excess air ratio region is set based on the ignition delay period and the combustion period,
• the throttle and the injector are controlled so as to fall within the set excess air ratio region, and
• the ignition delay period is calculated from a crank angle from an ignition timing of the ignition plug until a second derivative value of a detection value of the combustion pressure estimation sensor reaches a maximum value.