| 摘要 |
PROBLEM TO BE SOLVED: To enable to properly judge NOx storing capacity of a catalyst by diagnosing the catalyst by using the time delay between the adjustment of exhaust gas ahead of the catalyst interposed in the exhaust system of an internal combustion engine and the successive change of the signal of an exhaust gas sensor. SOLUTION: Sensors, 7 to 9, by which a load L, a speed of rotation (n), a temperature, the position of a throttle valve and the like are detected, are installed, and, according to sensor signals, fuel supply signals to be applied to a fuel supply means 6 are formed in a control device 5. An internal combustion engine 1 is operated alternately, namely, in the first process, by a lean mixture having less fuel than a stoichiometric mixture composition (λ=1), and in the second process, by a rich mixture having more fuel than the stoichiometric mixture composition. In the first process, NOx emission is stored in an NOx catalyst, and in the second process, the stored catalyst is regenerated. In this case, the catalyst 2 is diagnosed by using the time delay between the adjustment of exhaust gas ahead of the catalyst 2 and the successive change of the signal of a gas sensor 4. |
