Air-fuel ratio controller of internal combustion engine and method for controlling air-fuel ratio of internal combustion engine

A method for controlling an air-fuel ratio of an internal combustion engine, the method comprising:

• setting a base injection, amount, which is an open-loop operation amount that controls an air-fuel ratio to a target value;
• calculating a feedback operation amount that controls a detected value of the air-fuel ratio, which is obtained by an air-fuel ratio sensor arranged in an exhaust passage of an internal combustion engine, to the target value;
• performing an increase correction on the base injection amount when a temperature of the internal combustion engine is lower than or equal to a specified temperature;
• operating a fuel injection valve based on the base injection amount on which the increase correction has been performed, wherein the base injection amount is corrected using the feedback operation amount and a learning value;
• and
• updating the learning value based on the feedback operation amount, wherein
• the internal combustion engine includes a cylinder wall surface, and
• if the increase correction is performed, when a temperature of the cylinder wall surface is high, the learning value is updated so that the learning value increases an increase correction rate of the base injection amount as compared to when the temperature of the cylinder wall surface is low.

An air-fuel ratio controller of an internal combustion engine, the air-fuel ratio controller comprising:

• circuitry configured to
• set a base injection amount, which is an open-loop operation amount that controls an air-fuel ratio to a target value,
• calculate a feedback operation amount that controls a detected value of the air-fuel ratio, which is obtained by an air-fuel ratio sensor arranged in an exhaust passage of an internal combustion engine, to the target value,
• perform an increase correction on the base injection amount when a temperature of the internal combustion engine is lower than or equal to a specified temperature,
• operate a fuel injection valve based on the base injection amount on which the increase correction has been performed, wherein the base injection amount is corrected using the feedback operation amount and a learning value, and
• update the learning value based on the feedback operation amount,
• the internal combustion engine includes a cylinder wall surface, and
• if the increase correction is performed, when a temperature of the cylinder wall surface is high, the learning value is updated so that the learning value increases an increase correction rate of the base injection amount as compared to when the temperature of the cylinder wall surface is low.