Patent ID: 8240195

Claim:
An abnormality detection apparatus for an air/fuel ratio sensor that outputs a signal that corresponds to air/fuel ratio of an internal combustion engine based on oxygen concentration in exhaust gas of the internal combustion engine, comprising: an air/fuel ratio control portion that performs an active air/fuel ratio control of periodically fluctuating the air/fuel ratio of the internal combustion engine between a rich state and a lean state; a data acquisition portion that acquires, as data for detecting abnormality, a parameter that corresponds to responsiveness during change of output of the air/fuel ratio sensor between a rich peak and a lean peak during the active air/fuel ratio control performed by the air/fuel ratio control portion; and an abnormality determination portion that determines presence/absence of abnormality of the air/fuel ratio sensor based on comparison between an abnormality criterion value and an average value of the data that have been obtained by performing acquisition of the data via the data acquisition portion a plurality of times, wherein: when the number of times the data has been acquired by the data acquisition portion becomes equal to or greater than a first set number, the abnormality determination portion executes determination as to the presence/absence of abnormality if the number of times the acquisition of the data at a time of large amount of intake air of the internal combustion engine has been performed by the data acquisition portion is greater than or equal to a second set number; and when the number of times the data has been acquired by the data acquisition portion becomes equal to or greater than a first set number, if the number of times the acquisition of the data at the time of large amount of intake air of the internal combustion engine has been performed by the data acquisition portion is less than the second set number, the abnormality determination portion does not execute the determination as to the presence/absence of abnormality, but continues to acquire the data until the number of times the data has been acquired by the data acquisition portion at the time of large amount of intake air of the internal combustion engine reaches the second set number.