| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the fuel consumption, and to lower than NOx concentration in the exhaust gas to be discharged into the atmospheric air by accurately detecting the deterioration of a NOx controlling means in a short time. SOLUTION: In a process for diagnosing deterioration of a NOx controlling means, an ECU determines whether the lean-burn control is performed or not (S1), and determines whether the rich spike control is performed or not (S2), and determines whether operation condition is changed or not (S3). In the case where the operation condition is not changed, a deterioration determining means detects the output peak value of the output from an NOx sensor arranged in the downstream of the exhaust passage of the NOx absorbent (S4) so as to detect the degree of deterioration (S6). In the case where the operation condition is changed, stop time near the theoretical air-fuel ratio is detected on the basis of the output voltage from an O2 sensor arranged in the downstream of the exhaust passage of the NOx absorbent (S5) so as to detect the degree of deterioration (S6). Degree of deterioration of the NOx absorbent is determined on the basis of these detection (S7), and in the case where a degree of deterioration is large, MIL lighting is performed (S8).</p> |
