| 摘要 |
<p>PURPOSE:To detect a degrading timing of a catalyst when an output range of an air/fuel ratio sensor exceeds a specified value and to measure a purifying rate from a relationship with a purifying rate of an exhaust gas by arranging an oxygen sensor on the upstream side of the catalyst and the air/fuel ratio sensor on the downstream side thereof. CONSTITUTION:A ternary catalyst 3 is mounted in an exhaust path 2 of an internal combustion engine 1 and an oxygen sensor 4 is mounted in the exhaust path of the upstream side of the catalyst 3 while an air/fuel ratio sensor 5 is mounted in the exhaust path on the downstream side thereof. The sensors 4 and 5 are connected electrically to an electronic controller 6 and a sensor controller 7 to obtain a sensor output therefrom. Then, the device 6 is connected electrically to a fuel injection valve 9 disposed in an intake path 8 of the engine 1 to control a fuel injection value of the injection value 9 according to an output voltage from the sensor 4. In other words, the sensor output contents of the device 6 are fed back to make a sensor output range almost constant as almost fixed air/fuel ratio. Thus, a degrading timing can be detected accurately by defining a specified value of the output range as such.</p> |
