| 摘要 |
<p>PURPOSE: To diagnose deteriorating condition of absorbent with high accuracy by providing air-fuel ratio detecting means upstream and downstream of absorbent, and diagnosing deteriorating condition of absorbent by a HC desorption amount which is estimated from the difference between both air-fuel ratio detecting signals after the temperature of absorbent attains the HC desorption temperature of absorbent. CONSTITUTION: A catalyst 4 (catalytic converter rhodium) for purifying exhaust gas is interposed in an exhaust passage 3 to purify pollutant component in exhaust gas in a prescribed high temperature condition, and also absorbent 5 is interposed in the exhaust passage 2 upstream from the catalyst 4 to desorp HC in a prescribed low temperature condition. In this case, air-fuel ratio sensors 6, 7 are provided upstream and downstream of the absorbent 5, and also a temperature sensor 9 is mounted in an exhaust passage 3 in the vicinity of the upstream of the absorbent 5. In a control unit 15, deteriorating condition of the absorbent 5 is diagnosed by the desorption amount of HC which is estimated on the basis of the difference between both air-fuel ratio detecting signals to be detected by both air-fuel ratio sensors 6, 7 after the temperature of the absorbent 5 attains the HC desorption temperature of the absorbent 5, or an amount according thereto.</p> |
