| 摘要 |
PURPOSE:To enhance the responsiveness of air-fuel ratio control with no problem of thermal damage, by providing an air-flow ratio sensor provided with a heater between catalyst converters arranged in two series. CONSTITUTION:In a control circuit 56, when an exhaust gas temperature delivered from a temperature sensor 68 is below a predetermined temperature, a high level signal is delivered from an output port 64 to a transistor 70 to energize a solenoid 44'. Accordingly, a an intake-air vacuum is introduced into a diaphragm chamber 38 in an actuator 34 through a solenoid valve 44, and therefore, a change-over valve 28 is urged to rotate. Therefore, an inlet port 24a is opened to allow exhaust gas pass through a first catalyst converter 22, but it does not pass through a bypass pipe 25. Further, since a high level signal is applied from the output port 64 to a transistor 72 to energize a heater 54, it is possible to detect the air-fuel ratio of mixture in such a condition that an air-fuel ratio is active, irrespective of low exhaust gas temperature. |
