Engine controller, engine control method, and memory medium

An engine control method that calculates an intake air amount of an engine and executes a fuel injection control of an injector by determining a fuel injection amount based on a calculated value of the intake air amount, the engine control method comprising:

• calculating the intake air amount based on a detected value of an intake air flow rate obtained by an air flow meter;
• calculating the intake air amount based on one of a detected value of an intake pipe pressure and a throttle opening degree without using the detected value of the intake air flow rate;
• determining that determines whether an intake air pulsation in an intake passage of the engine is great;
• updating a difference amount learning value based on a difference amount by which a first intake air amount differs from a second intake air amount such that the difference amount learning value becomes close to the difference amount when it is determined that the intake air pulsation is not great, the first intake air amount being the calculated value of the intake air amount obtained by calculation based on the detected value of the intake air flow rate, the second intake air amount being the calculated value of the intake air amount obtained by calculation based on one of the detected value of the intake pipe pressure and the throttle opening degree;
• calculating an upper limit guard value and a lower limit guard value based on a state quantity that indicates a running state of the engine;
• setting the upper limit guard value as a learning reflected value when the difference amount learning value is greater than the upper limit guard value;
• setting the lower limit guard value as the learning reflected value when the difference amount learning value is less than the lower limit guard value;
• setting the difference amount learning value as the learning reflected value when the difference amount learning value is less than or equal to the upper limit guard value and greater than or equal to the lower limit guard value;
• and
• setting the first intake air amount as the calculated value of the intake air amount when it is determined that the intake air pulsation is not great;
• and
• setting a sum of the second intake air amount and the learning reflected value as the calculated value of the intake air amount when it is determined that the intake air pulsation is great.

A non-transitory computer readable memory medium that stores a program that causes a processor to execute an engine control process, the engine control process calculating an intake air amount of an engine and executing a fuel injection control of an injector by determining a fuel injection amount based on a calculated value of the intake air amount, the engine control process comprising:

• calculating the intake air amount based on a detected value of an intake air flow rate obtained by an air flow meter;
• calculating the intake air amount based on one of a detected value of an intake pipe pressure and a throttle opening degree without using the detected value of the intake air flow rate;
• determining that determines whether an intake air pulsation in an intake passage of the engine is great;
• updating a difference amount learning value based on a difference amount by which a first intake air amount differs from a second intake air amount such that the difference amount learning value becomes close to the difference amount when it is determined that the intake air pulsation is not great, the first intake air amount being the calculated value of the intake air amount obtained by calculation based on the detected value of the intake air flow rate, the second intake air amount being the calculated value of the intake air amount obtained by calculation based on one of the detected value of;
• the intake pipe pressure and the throttle opening degree;
• calculating an upper limit guard value and a lower limit guard value based on a state quantity that indicates a running state of the engine;
• setting the upper limit guard value as a learning reflected value when the difference amount learning value is greater than the upper limit guard value;
• setting the lower limit guard value as the learning reflected value when the difference amount learning value is less than the lower limit guard value;
• setting the difference amount learning value as the learning reflected value when the difference amount learning value is less than or equal to the upper limit guard value and greater than or equal to the lower limit guard value;
• and
• setting the first intake air amount as the calculated value of the intake air amount when it is determined that the intake air pulsation is not great;
• and
• setting a sum of the second intake air amount and the learning reflected value as the calculated value of the intake air amount when it is determined that the intake air pulsation is great.