Patent ID: 7885757

Claim:
A degradation determination apparatus for an oxygen concentration sensor, which is used in an internal combustion engine that has a fuel injection valve for injecting fuel used for combustion and the oxygen concentration sensor is used for detecting oxygen concentration in exhaust gas and for effecting a feedback control of fuel injection quantity of the fuel injection valve to equalize an air-fuel ratio calculated from a detection value of the oxygen concentration sensor with a target air-fuel ratio, said degradation determination apparatus comprising: a dither control means for performing a dither control, which compulsively changes the air-fuel ratio alternately to rich side and to lean side by controlling the fuel injection quantity of the fuel injection valve; an integral calculation means for calculating an integral of a difference between the detection value of the oxygen concentration sensor, which changes in accordance with the dither control, and a previously memorized predicted value that indicates an ideal change of the detection value generated by the dither control; and a degradation determination means for determining presence and absence of degradation of the oxygen concentration sensor based on a value of the integral calculated by the integral calculation means.