| 摘要 |
A catalyst deterioration detection device for an internal combustion engine, according to the present invention, includes: a three-way catalyst (38) mounted in an exhaust passage (30,34) of the internal combustion engine (20) and having an O2 storage capability; an air-fuel ratio sensor (45), mounted upstream of the three-way catalyst, for linearly detecting an air-fuel ratio; an air-fuel ratio feedback control unit (70) for, based on the output of the air-fuel ratio sensor (45), calculating a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero; an O2 sensor (46), mounted downstream of the three-way catalyst, for detecting whether the air-fuel ratio is rich or lean; a catalyst deterioration determining unit (70) for determining deterioration of the three-way catalyst on the basis of the length of a response curve that the output of the O2 sensor describes during the time that air-fuel ratio feedback control is being performed by the air-fuel ratio feedback control unit. <IMAGE>
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