Oxygen sensor having protective hood and method of using same

Claim 1

An oxygen sensor for detecting oxygen concentration in the exhaust gas of an internal combustion engine, said sensor having an oxygen ion conductive solid electrolyte tube which is closed at one end, and open at the other end, anode and cathode electrode layers porously coated respectively on the outer and inner surfaces of the electrolyte tube and a tubular metal shell which tightly receives the electrolyte tube therein such that a closed end portion of the electrolyte tube protrudes from the shell and is adapted to be disposed in an exhaust gas stream, a protective hood which has the shape of a cylindrical tube with a closed end and is fixed at its open end portion to the shell, the inside of said hood being spaced from the anode electrode layer outside of the shell, said hood having a plurality of apertures formed in its wall to allow the gas to be measured to pass through the interior of said hood, the improvement comprising: said hood having a gas inlet of a single aperture formed in the side wall of said hood in an elongate shape to extend axially of the hood, and a gas outlet formed in the side wall of said hood comprising at least one aperture, said gas outlet being located at an angle of approximately 180° with said gas inlet aperture in cross-sectional view of said hood, said gas outlet having a total area of opening which is smaller than the area of opening of said gas inlet aperture, and said shell having means for permitting attachment of the sensor to an article in which a gas to be measured flows in a definite orientation such that said gas inlet aperture opens facing the stream of said gas.

Claim 20

A method of detecting the oxygen content of a gas stream which comprises the steps of: (a) providing an oxygen sensor having an oxygen ion conductive solid electrolyte tube which is closed at one end, anode and cathode layers porously coated respectively on the outer and inner surfaces of said electrolyte tube, and a tubular metal shell which receives the electrolyte tube therein such that a closed end portion of the electrolyte tube protrudes from said shell and is adapted to be disposed in an exhaust gas stream, a protective hood which has the shape of a cylindrical tube with a closed end and is fixed at an open end portion to the shell, the inside of said hood being spaced from the anode electrode layer outside of said shell, said hood comprising a single outlet aperture and an outlet comprising at least one aperture, said inlet aperture being spaced from said outlet apertures by approximately 180°; said inlet aperture having a larger area than the total area of said outlet apertures; (b) arranging said sensor in said gas stream such that said inlet aperture is arranged normal to the direction of flow of said gas stream and such that said outlet apertures are downstream of said inlet aperture in the direction of flow of said gas stream; and (c) measuring the oxygen content of said gas stream.

Claim 21

A method of detecting the oxygen content of a gas stream which comprises the steps of: (a) providing an oxygen sensor having an oxygen ion conductive solid electrolyte tube which is closed at one end, anode and cathode layers porously coated respectively on the outer and inner surfaces of said electrolyte tube, and a tubular metal shell which receives the electrolyte tube therein such that a closed end portion of the electrolyte tube protrudes from said shell and is adapted to be disposed in an exhaust gas stream, a protective hood which has the shape of a cylindrical tube with a closed end and is fixed at an open end portion to the shell, the inside of said hood being spaced from the anode electrode layer outside of said shell, said hood comprising a single outlet aperture and an outlet comprising at least one aperture, said inlet aperture being spaced from said outlet apertures by approximately 180°; said inlet aperture having a larger area than the total area of said outlet apertures; (b) arranging said sensor in said gas stream such that said inlet aperture is arranged normal to the direction of flow of said gas stream and such that said outlet apertures are downstream of said inlet aperture in the direction of flow of said gas stream; and (c) measuring the oxygen content of said gas stream.