Device for detecting air-fuel ratio of engine

摘要

A device for detecting the air-fuel ratio of an engine by measuring the oxygen concentration of the exhaust gas by means of an oxygen sensor including an oxygen pump and a cell element for measuring the oxygen concentration ratio, comprising a filter circuit for smoothing the output signal of the oxygen sensor, said filter circuit having a time constant which is variably set so that it is in proportional relation to the number of revolutions per units of time of the engine.