Patent ID: 8555614
Filing Date: 2013-10-15
Classification: F02D,Y02T

Abstract:
1. An exhaust gas control apparatus of an internal combustion engine, comprising: a catalyst that is provided in an exhaust passage of an internal combustion engine and is configured to store oxygen; an oxygen sensor that is provided on an exhaust gas downstream side of the catalyst in the exhaust passage and is configured to output a signal indicative of an air-fuel ratio of exhaust gas; and a controller comprising a first estimating portion, a second estimating portion, a third estimating portion, a fourth estimating portion, and a determining portion; the first estimating portion being configured to estimate whether an amount of oxygen stored in the catalyst is a maximum amount or a minimum amount; the second estimating portion being configured to execute forced rich control that forcibly makes an air-fuel ratio of exhaust gas that flows into the catalyst richer than a stoichiometric air-fuel ratio when it is estimated by the first estimating portion that the amount of oxygen stored in the catalyst is the maximum amount, and to estimate an amount of oxygen released from the catalyst during a period of time between a point in time at which the forced rich control starts and a point in time at which the output of the oxygen sensor makes a rich reversal from a value corresponding to an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio to a value corresponding to an air-fuel ratio that is richer than the stoichiometric air-fuel ratio, based on the period of time; the third estimating portion being configured to execute forced lean control that forcibly makes an air-fuel ratio of exhaust gas that flows into the catalyst leaner than the stoichiometric air-fuel ratio when it is estimated by the first estimating portion that the amount of oxygen stored in the catalyst is the minimum amount, and to estimate an amount of oxygen stored in the catalyst during a period of time between a point in time at which the forced lean control starts and a point in time at which the output of the oxygen sensor makes a lean reversal from a value corresponding to an air-fuel ratio that is richer than the stoichiometric air-fuel ratio to a value corresponding to an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, based on the period of time; the determining portion being configured to determine that there is a response delay abnormality in one of the rich reversal or the lean reversal of the output of the oxygen sensor when a degree of deviation between the oxygen release amount estimated by the second estimating portion and the oxygen storage amount estimated by the third estimating portion is equal to or greater than a predetermined degree; and the fourth estimating portion being configured to perform fuel cut control that stops fuel injection in the internal combustion engine when it is estimated by the first estimating portion that the amount of oxygen stored in the catalyst is the minimum amount, and to estimate a response delay time of a lean reversal of the output of the oxygen sensor based on a period of time between a point in time at which the fuel cut control starts and a point in time at which the output of the oxygen sensor makes a lean reversal; wherein the third estimating portion takes the response delay time of the lean reversal of the output of the oxygen sensor estimated by the fourth estimating portion into account when estimating the oxygen storage amount.