| 摘要 |
PURPOSE:To maintain the specified temp. of an oxygen sensor which detects the concn. of the oxygen in the exhaust gas of an internal-combustion engine and to control the air-fuel ratio of te engine by controlling the voltage to be impressed to the heater contained in a sensor substrate. CONSTITUTION:The oxygen sensor is provided with an oxygen concentration cell and an oxygen pump on an alumina substrate and the heater in the substrate and is so constituted as to heat the electrode of the oxygen concentration cell and to maintain the cell at the working temp. The 1st resistor R1 is connected in series to the heater 43 and the 2nd resistor R2 and 3rd resistor R3 are connected in series to constitute a bridge circuit in parallel with the series circuit thereof. The difference between the voltage Vb at the juncture between the heater 43 and the resistor R1 and the voltage Va at the juncture between the resistors R2 and R3 is detected by an integration circuit 57. The voltage is impressed from a current control circuit 61 to the heater 43 so as to maintain the equal voltages Va and Vb. Since the heater voltage is controlled by forming the resistor into the bridge circuit, the specified working temp. of the sensor is maintained. The detection of the oxygen concn. with high accuracy is thus made possible and the air-fuel ratio is controlled. |
