Abstract: An oxygen gas concentration-detecting apparatus for use in an internal combustion engine comprising a plate-shaped substrate, a plate-shaped oxygen ion-conducting solid electrode for generating an electromotive force between a first surface contacted with air and a second surface contacted with an exhaust gas of the engine according to the difference between the concentrations of oxygen gases of the air and the exhaust gas, the solid electrode being laminated on the substrate, a pair of electrode members for taking out the electromotive force as a detection signal and a nitrogen oxide-reducing catalyst layer for promoting the reduction of nitrogen oxide arranged to cover the second surface of the oxygen ion-conducting solid electrode. By this apparatus, the concentration of oxygen gas inclusive of oxygen gas generated by reduction of nitrogen oxides can be precisely detected.

Abstract: Disclosed is an oxygen gas concentration-detecting apparatus comprising a ceramic substrate for generating an electromotive force according to oxygen gas concentration of gases contacted with both the surfaces of the ceramic substrate, a pair of electrode members arranged on the ceramic substrate to take out the electromotive force, an oxidation catalyst layer formed on the outer surface of the ceramic substrate to promote oxidation reaction of unburnt components and a reduction catalyst layer arranged on the outer surface of the ceramic substrate to promote reduction reaction of nitrogen oxides. By this apparatus, the concentration of oxygen gas inclusive of oxygen gas generated by reduction of nitrogen oxides can be precisely detected, and discharge of nitrogen dioxides is controlled and a so-called EGR control device can be omitted.