| 摘要 |
PURPOSE:To invariably measure the air/fuel ratio accurately by always maintain the concentration of an inside electrode as the reference oxygen electrode of an oxygen sensor at a constant level to prevent variation in the average level of output of a sensor depending on the operating condition. CONSTITUTION:A high level signal corresponds to the rich signal in the air/fuel ratio while a low level signal to the lean signal (R/L signal). Based on the R/L signal, a air/fuel ratio controller 9 performs a feedback control so that the air/ fuel ratio of a gas mixture supplied to the engine gives the theoretical air/fuel ratio. A means is provided to apply a bias voltage between both terminals 20 and 21 with a specified current Is running to an oxygen sensor 7 to always maintain the reference oxygen concentration of the inner electrode almost at a fixed value. An exhaust judging device 14 actuates analog switches 10 and 11 according to the exhaust temperature. When a resistance is selectively interposed between A and B according to the temperature of exhaust to bring the total resistance to Rab, a run-off current Is is supplied to an oxygen sensor 7 depending on the difference between the sensor output Vs and the bias voltage Vb. Thus, the quantity of current is determined by Is=(Vb-Vs)/Rab. |
