AIR-FUEL RATIO DETECTOR

摘要

PURPOSE:To detect correctly an air-fuel ratio in approximately the entire region thereof and to control easily said ratio by controlling the pump current to be impressed to an oxygen pump in such a manner that the electromotive force of an oxygen concn. cell part attains the prescribed value larger than the electromotive force by the difference between the oxygen concn. in the exhaust gas and the oxygen concn. in the atm. in a theoretical air-fuel ratio. CONSTITUTION:The oxygen in a diffusion chamber 4 is pumped as oxygen ion out in a direction from an electrode 1b to 1a when the pump current IP is passed to an oxygen pump part 1 in the direction from the electrode 1a to 1b. The oxygen partial pressure is then decreased and the electromotive force VS of the oxygen concn. cell part 2 is increased. The force VS is detected 6 and is compared with the prescribed reference voltage VREF. The current IP is increased if VSVREF to decrease the amt. of the oxygen to be pumped and to decrease the force VS. The current IP is thus so controlled as to maintain VS=VREF at all times. The current IP is measured by a measuring means 9 or is outputted in the form of the voltage output.