| 摘要 |
PURPOSE:To prevent the generation of blackening and to prevent the deterioration in element performance by stopping the current supply between the electrodes of an oxygen pump element when the voltage generated between the electrodes of a battery element for measuring an oxygen concn. ratio is below the prescribed value. CONSTITUTION:The oxygen pump element 1 and battery element 2 for measuring the oxygen concn. ratio formed by providing electrode plates 5-8 to the front and rear surfaces of an oxygen ion conductive solid electrolyte material are disposed via a spacing part 3 into an exhaust pipe. Constant current is supplied from a constant current circuit 11 to the element 1 and the voltage signal generated between the electrodes 7 and 8 of the element 2 is inputted to an air-fuel ratio control circuit 31. A solenoid valve 44 is controlled according to the detected value. The output voltage of an amplifier 30 increases with an increase in the voltage between the electrodes 7 and 8 and when said voltage exceeds the reference voltage of a limiter reference voltage generator 43, the output voltage of an operational amplifier 12 decreases and a transistor 13 turns off to stop the current supply to the element 1. |
