Controller for internal combustion engine and method for controlling internal combustion engine

A controller for an internal combustion engine, wherein

• the internal combustion engine includes
• an exhaust passage into which an exhaust produced in the internal combustion engine is discharged, and
• an exhaust purification device including a catalyst arranged in the exhaust passage and having an oxygen adsorption function, the exhaust purification device using oxygen adsorbed in the catalyst to purify the exhaust flowing through the exhaust passage,
• the controller comprising circuitry configured to
• adjust an amount of fuel supplied to a cylinder of the internal combustion engine through feedback control that uses an air-fuel ratio deviation, which is a deviation between an air-fuel ratio detection value that is an air-fuel ratio detected by an upstream side air-fuel ratio sensor located at an upstream side of the catalyst in the exhaust passage and a target air-fuel ratio, as an input,
• alternately repeat a lean period process in which the target air-fuel ratio is set to a leaner value than a stoichiometric air-fuel ratio and a rich period process in which the target air-fuel ratio is set to a richer value than the stoichiometric air-fuel ratio,
• update a learning value that compensates for a steady deviation in the air-fuel ratio detection value, and
• use the learning value to correct a deviation between an oxygen adsorption amount, which is an amount of oxygen adsorbed in the catalyst during the lean period process, and an oxygen desorption amount, which is an amount of oxygen desorbed from the catalyst during the rich period process,
• in a case where an absolute value of an oxygen amount deviation between the oxygen adsorption amount and the oxygen desorption amount is less than a determination value, the circuitry is configured to update the learning value when one of the lean period process and the rich period process is switched to the other one of the lean period process and the rich period process, and the circuitry is configured not to update the learning value when the other one of the lean period process and the rich period process is switched to the one of the lean period process and the rich period process, and
• in a case where the absolute value of the oxygen amount deviation is greater than or equal to the determination value, the circuitry is configured to update the learning value in both of a case where one of the lean period process and the rich period process is switched to the other one of the lean period process and the rich period process and a case where the other one of the lean period process and the rich period process is switched to the one of the lean period process and the rich period process.

A method for controlling an internal combustion engine, wherein

• the internal combustion engine includes
• an exhaust passage into which an exhaust produced in the internal combustion engine is discharged, and
• an exhaust purification device including a catalyst arranged in the exhaust passage and having an oxygen adsorption function, the exhaust purification device using oxygen adsorbed in the catalyst to purify the exhaust flowing through the exhaust passage, and
• the method comprising:
• adjusting an amount of fuel supplied to a cylinder of the internal combustion engine through feedback control that uses an air-fuel ratio deviation, which is a deviation between an air-fuel ratio detection value that is an air-fuel ratio detected by an upstream side air-fuel ratio sensor located at an upstream side of the catalyst in the exhaust passage and a target air-fuel ratio, as an input;
• alternately repeating a lean period process in which the target air-fuel ratio is a leaner value than a stoichiometric air-fuel ratio and a rich period process in which the target air-fuel ratio is a richer value than the stoichiometric air-fuel ratio;
• updating a learning value that compensates for a steady deviation in the air-fuel ratio detection value;
• correcting a deviation between an oxygen adsorption amount, which is an amount of oxygen adsorbed in the catalyst during the lean period process, and an oxygen desorption amount, which is an amount of oxygen desorbed from the catalyst during the rich period process, using the learning value;
• in a case where an absolute value of an oxygen amount deviation between the oxygen adsorption amount and the oxygen desorption amount is less than a determination value, updating the learning value when one of the lean period process and the rich period process is switched to the other one of the lean period process and the rich period process and not updating the learning value when the other one of the lean period process and the rich period process is switched to the one of the lean period process and the rich period process;
• and
• in a case where the absolute value of the oxygen amount deviation is greater than or equal to the determination value, updating the learning value in both of a case where one of the lean period process and the rich period process is switched to the other one of the lean period process and the rich period process and a case where the other one of the lean period process and the rich period process is switched to the one of the lean period process and the rich period.