| 摘要 |
<p>PURPOSE:To lay the oxygen in exhaust gas into a proper state and properly judge the deteriorating degree of a catalyst by a catalyst deterioration judging means having such a constitution so as to conduct feedback control of air-fuel ratio according to the detection value of a second exhaust sensor and deterioration judgment on the basis of a third exhaust sensor. CONSTITUTION:Front end catalytic convertors 18a, 18b are disposed on upper stream side exhaust passages 161, 162, respectively, and a main catalytic convertor 19 is disposed on a lower stream side exhaust passage. On the upper stream side and lower stream side of each front end catalytic convertor 18a, 18b in the upper stream side exhaust passages 161, 162, exhaust sensors 201-204 are placed. On the lower steam side of the main catalytic convertor 19 in the lower stream side exhaust passage, also, an exhaust sensor 205 is place. Since feedback control of air-fuel ratio is conducted by the exhaust sensors 201-204 on the upper stream of the main catalytic convertor 19 at the time of judging the deterioration of the convertor 19, thus, the exhaust gas allowing to properly judge the deteriorating degree of catalyst is exhausted to the lower stream side exhaust sensor 205.</p> |
