Air-fuel ratio control system for internal combustion engine and control method therof

The air-fuel ratio control system for an internal combustion engines comprising:

• a controller that:
• divides a catalyst provided in an exhaust passage of an internal combustion engine into multiple sections in a flow direction of an exhaust gas,
• calculates a change in an oxygen storage amount in a specified section among the multiple sections based on an air-fuel ratio of an exhaust gas flowing into the catalyst,
• estimates the oxygen storage amount in the specified section based on a record of the change in the oxygen storage amount;
• and
• controls the air-fuel ratio based on the oxygen storage amount in the specified section.

An air-fuel ratio control method for an internal combustion engine comprising the steps of:

• dividing a catalyst provided in an exhaust passage of the internal combustion engine into multiple sections in a flow direction of the exhaust gas,
• calculating a change in an oxygen storage amount in a specified section among the multiple sections based on an air-fuel ratio of an exhaust gas flowing into the catalyst,
• estimating the oxygen storage amount in the specified section based on a record of the change in the oxygen storage amount, and
• controlling the air-fuel ratio based on the estimated oxygen storage amount.