Patent ID: 9291085
Filing Date: 2016-03-22
CPC Classification: F01N,F02D,Y02T

Claim Text:
1. A method executed by a controller in an internal combustion engine, comprising: receiving an output of an upstream air-fuel ratio sensor and an output of a downstream air-fuel ratio sensor, the upstream air-fuel ratio sensor being attached to an exhaust gas passage of the internal combustion engine such that the upstream air-fuel ratio sensor is positioned upstream of a catalyst provided in the exhaust gas passage to purify an exhaust gas generated in the internal combustion engine, the downstream air-fuel ratio sensor being attached to the exhaust gas passage such that the downstream air-fuel ratio sensor is positioned downstream of the catalyst; detecting a state in which the catalyst does not store or release oxygen based on the output of the downstream air-fuel ratio sensor; deciding as an estimated ideal air-fuel ratio in the internal combustion engine an air-fuel ratio detected by the upstream air-fuel ratio sensor when the state in which the catalyst does not store or release oxygen is detected; comparing a value of the output of the upstream air-fuel ratio sensor to a value of the estimated ideal air-fuel ratio, calculating an instantaneous value of the oxygen storage capacity and an instantaneous value of an oxygen release capacity, integrating the instantaneous value of the oxygen storage capacity and the instantaneous value of the oxygen release capacity to obtain an integrated value of the oxygen storage capacity, and deciding the integrated value as an estimated value of the oxygen storage capacity; and operating the internal combustion engine to feedback-control an air-fuel ratio such that the estimated value of the oxygen storage capacity converges at a predetermined target oxygen storage capacity.