AIR FUEL RATIO DETECTING METHOD

摘要

PURPOSE:To detect an air fuel ratio with good accuracy without being influenced by the inner part resistance of oxygen sensor by providing the electrode on air side and the electrode on the gas side to be measured on the surface of oxygen ion conductive solid electrolyte and by making the voltage between electrodes in the prescribed voltage. CONSTITUTION:The air side electrode 2 and gas to be measured side electrode 3 are provided on the surface of oxygen ion conductive solid electrolyte 1. The gas to be measured touches the electrode 3 through diffusion layer 4. The operational amplifier circuit to feed the constant voltage V1 to the electrode 3 and to constitute a low pass filter on the electrode 2 is connected. The potential difference between the electrodes 2, 3 is held to the sum (e+ir) of the prescribed voltage (e) and the value ir multiplying current (i) by the internal resistance (r) of the oxygen sensor by adjusting the voltage of the inverse input terminal (-) and non-inverse input terminal (+) of the operational amplifier 5. The density of the oxygen and CO in the gas to be measured is then detected from the current value (i). The air fuel ratio can therefore be detected with high accuracy by reducing the effect of the internal resistance of the oxygen sensor and the effect due to the temp. variation because of the voltage between electrodes being held to (e+ir).