Gas component detection apparatus

Abstract

A gas component detection apparatus for detecting gas components contained in an exhaust gas from a combustion device and determining an air-fuel ratio of an air-fuel mixture supplied thereto. A gas component detecting element composed of a semiconductive metal oxide is contacted by the exhaust gas andexhibits variable electric resistances according to the concentrations of the gas components. The electric resistance is taken out as an electric signal through two electrodes disposed either on the surface of the detecting element exposed to the exhaust gas or within the detecting element adjacent that exposed surface. A porous coating layer having an exhaust gas permeability covers the surface of the detecting element exposed to the exhaust gas so as to prevent poisonous substances contained in the exhaust gas from depositing on that exposed surface of the detecting element. The coating layer is formed of a metal oxide having electrically insulating properties and carries therein a catalyst promoting an oxidation reaction of the exhaust gas. The detecting element exhibits an abruptly changed electric resistance when the actual air-fuel ratio of the air-fuel mixture supplied into the combustion device is deviated from a stoichiometrical air-fuel ratio, thereby enabling the control of the air-fuel ratio of the air-fuel mixture.

Dependencies are inferred from the claim text.