| 摘要 |
PURPOSE:To detect accurate concentrations by providing a voltage detecting method which detects the electric current of an oxygen pump element in the form of voltage signals proportional to the oxygen concentration and providing a voltage applying method which applys the deviation voltage from a reference voltage. CONSTITUTION:In the detecting system of air/fuel ratio of an internal combustion engine, exhaust gas flows in an air reservoir 2 surrounded with solid electrolyte 1, and if the air/fuel ratio is lean, the voltage between the electrodes 6a and 6b of electric cell element 8 becomes lower than the voltage Vr1 of the reference voltage supply 12 and the output level of the differential amplifier 11 becomes plus. Then electric current appears from the electrode 5a to 5b in the oxygen pump element 7, which applys voltage on a resistor 15 and inversion input of an operational amplifier 13. If the air/fuel ratio is rich, outputs or electric current in this process are inversed. Therefore, the pump current is always proportional to the oxygen concentration in exhaust gas, so that the voltage appearing on the resistor 15 is A/D converted and processed with a processor 17. Thus, the output of the obtd. detecting device are almost proportional to the oxygen concentration. |
