| 摘要 |
<p>PURPOSE:To detect catalytic activity easily and precisely without requiring any temperature sensor by arranging a sensor, which detects oxygen concentration in exhaust gas, on downstream side of a catalyst, which eliminates toxic constituents in exhaust gas, and determining that the catalyst is in active condition when an output fluctuation is within the predetermined range. CONSTITUTION:In a V type-engine 1, two branch exhaust pipes 2, 3 are respectively provided with beneath catalysts 5, 6 while a collecting exhaust pipe 4 is provided with an underfloor catalyst 7. Each of upstream side oxygen concentration sensors 10, 11 is arranged on the upstream side of each of the beneath catalysts 5, 6 individually while a downstream side oxygen concentration sensor 12 is arranged on the downstream side of the underfloor catalyst 7. In addition, each of downstream side oxygen concentration sensors 13, 14 may be arranged on the downstream side of each of the beneath catalysts 5, 6. In an electric controller 15, air-fuel ratio feed back control is carried out on the basis of each of the detected signals form each of the upstream side oxygen concentration sensors 10, 11. On the other hand, the electric control unit (ECU) 15 analyzes the fluctuation on the basis of each of the detected signals from each of the downstream side oxygen concentration sensor 12-14 so as to detect whether catalytic activity for each of the catalysts 5-7 exists or not.</p> |
