Patent Document ID: 20150075507
Application ID: 14463188
Patent Flag: 0

Claim One:
1. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine, comprising: an air-fuel-ratio sensor detecting an air-fuel-ratio of an exhaust gas at a confluent portion into which the exhaust gas flows from each of multiple cylinders of the internal combustion engine; an estimation portion executing an air-fuel-ratio estimation for estimating the air-fuel-ratio of each cylinder based on a detection value which the air-fuel-ratio sensor detects at an air-fuel-ratio detection timing for each cylinder; a control portion executing a cylinder-by-cylinder air-fuel-ratio control in which the air-fuel-ratio of each cylinder is controlled based on the estimated air-fuel-ratio of each cylinder; a learning portion computing a learning value of a correction quantity for each cylinder, which is obtained by executing the cylinder-by-cylinder air-fuel-ratio control; a convergence-determination portion determining whether the estimated air-fuel-ratio has converged; and a leaning-prohibit portion prohibiting a computation of the learning value of the correction quantity for each cylinder until the convergence-determination portion determines that the estimated air-fuel-ratio has converged.