Air/fuel ratio detector

摘要

An air/fuel ratio detector providing an unambiguous output for both fuel-rich and fuel-lean regions is disclosed. The detector includes a solid-electrolyte oxygen-concentration-difference-actuated electrochemical cell sensor element and a solid-electrolyte oxygen pump element, each element being in the form of an oxygen-ion-conductive solid electrolyte having a porous electrode formed on both sides thereof. The electrochemical cell sensor element is disposed to face the pump element with a small gap therebetween. An air compartment open to the atmosphere is formed on the side of the pump element opposite the small gap. One terminal of the pump element is connected to a switch having at least two positions, one providing connection to a varying current source for maintaining the electromotive source of the electrochemical cell sensor at a predetermined value, and another position providing connection to a constant current source for maintaining the pump current flowing through the pump element at a fixed predetermined level. The air/fuel ratio is detected by an output signal provided by one of the electromotive force of the sensor element and the pump current.