| 摘要 |
<p>PURPOSE: To judge the deteriorated state of a catalyst by providing a control means additionally with the function of judging a catalyst to be normal when the output voltage of an exhaust sensor is the specified judgment value. CONSTITUTION: An internal combustion engine 2 is provided with a first exhaust sensor 86 and a second exhaust sensor 88 in an exhaust passage upstream and downstream of a catalyst 28 so as to respectively detect oxygen concentration to be the exhaust component value. On the basis of a first detection signal and a second detection signal outputted by the first and second exhaust sensors 86, 88, a control part 68 performs the feedback control of a fuel injection valve 30 so that an air-fuel ratio becomes the target value. The control part 68 is additionally provided with the function of judging the catalyst to be normal when the difference between the maximum value and minimum value of the output voltage of the second exhaust sensor 88 is smaller than the specified judgment value at the time of judging the deteriorated state of the catalyst 28. The deteriorated state of the catalyst can thereby be judged positively.</p> |
