Patent ID: 7850833

Claim:
An oxygen sensor that is positioned downstream of a three-way catalyst for an internal combustion engine, the oxygen sensor comprising: an exhaust gas side electrode that is exposed to an exhaust gas; a reference gas side electrode that is exposed to a reference gas, which serves as a reference for oxygen concentration; an electrolyte that is positioned between the exhaust gas side electrode and the reference gas side electrode; a coating layer that has a porosity of 10% or less and is positioned opposite the electrolyte being in contact with the exhaust gas side electrode; and a cover for installing the oxygen sensor in an isolated manner in a piping that is positioned downstream of the three-way catalyst, wherein the cover includes vent holes, which are adjusted so that an exhaust gas flow rate prevailing at the surface of the coating layer is lower than or equal to 1/10 an exhaust gas flow rate prevailing outside the cover while the internal combustion engine idles after warm-up.