| 摘要 |
PURPOSE:To accurately detect the oxygen concentration by equalizing the potential in one end on the side of a current detecting resistance of a series circuit, which consists of a pump element and the current detecting resistance, to a reference potential. CONSTITUTION:If an air-fuel ratio is in the lean area when the current supplied to a heater element 3 is leaked to flow an oxygen pump element 8, a part of the current supplied from a power source 40 to the element 3 passes the inside of a solid electrolyte member 1 from the element 3 and reaches the position between electrodes 6a and 6b of the element 8 and joins the pump current due to the positive output level of a differential amplifier 11 and flows toward the electrode 6b and flows to the earth through a current detecting resistance 13. Oxygen in a gas storage chamber 2 is pumped out by this leak current, and a voltage is generated between electrodes 7a and 7b of a battery element 9, and the output voltage of the amplifier 11 is controlled, and a voltage indicating the pump current including the leak current is supplied from the resistance 13 to a control circuit 14. If the air-fuel ratio is in the rich area, a voltage indicating the pump current obtained by subtracting the leak current from the output current of the amplifier 11 is supplied as the oxygen concentration detection value from the resistance 13 to the circuit 14. |
