| 摘要 |
PURPOSE:To obtain oxygen concn. detection output characteristic having good linearity in a wide range from a lean region to a rich region, by calculating an oxygen concn. detection value from the supply current value of the pump current supply means between a pair of electrodes. CONSTITUTION:When the air-fuel ratio of an engine supply gaseous mixture is resent in a lean region in a sensor selection state, the positive level voltage of a differential amplifying circuit 22 is supplied to a series circuit of a resistor 24 and an oxygen pump element 15 and a pump current flows between the electrodes 11a, 11b of the element 15. Oxygen in a gas stagnation chamber 2 is ionized at the electrode 11b by said pump current to move through the element and discharged from the electrode 11a as oxygen gas and oxygen in the chamber 2 is pumped out. By this pumping-out action, oxygen concn. difference is generated between the exhaust gas in the chamber 2 and the gas in a reference gas chamber to generate voltage Vs between electrodes 12a, 12b and said voltage Vs is supplied to the reversal input terminal of the differential amplifying circuit 22 and, because the output voltage of the circuit is proportional to the difference voltage of the voltage Vs and the output voltage of a reference voltage source 26, the pump current value is proportional to the concn. of oxygen in exhaust gas. |
