| 摘要 |
PURPOSE:To prevent the generation of a blackening phenomenon, by stopping the supply of current between electrodes of an oxygen pump element when an AC component peak voltage generated between electrodes of a battery element exceeds a specified voltage. CONSTITUTION:This detector has a pair of oxygen ions conducting solid electrolytic materials each having a pair of electrodes arranged as opposed to each other through a specified clearance part 3. One of the materials acts as oxygen pump element 1 and the other does as battery element 2 for measuring the oxygen concentration ratio. A current supply circuit 11 supplies current between electrodes 5 and 6 of the element 1 and the supply current value is changed to keep voltage generated between the electrodes 7 and 8 of the element 2 at a constant value. Then, AC component of the voltage generated in the element 2 is detected and when the peak voltage of the AC component exceeds a specified value, the supply of current between the electrodes 5 and 6 of the element 1 is stopped. This allows the avoiding of an excessive current running to the element 1 regardless of violent changes in voltage as generated in the element 2 in the vicinity of the theoretical air/fuel ratio when the concentration of oxygen in an engine exhaust gas is measured. |
