Oxygen sensor with a sintered reference source of oxygen

Claim 1

An oxygen sensor for determining the oxygen content in a fluid, comprising: a cylindrical metallic casing having a first inwardly bent portion at one end thereof and a second inwardly bent portion at the other end thereof; a disc-shaped solid electrolyte coaxially disposed in said casing so that the outwardly facing flat surface thereof contacts with said first inwardly bent portion; a porous metallic film coated on said outwardly facing surface of said solid electrolyte disc; a cylindrical sinter mass of a metal and an oxide of the metal, said sinter mass functioning as a reference source of oxygen and being coaxially disposed on the inside facing flat surface of said solid electrolyte disc; an annular insulating member disposed in said casing in a manner coaxially surrounding said sinter mass; a disc-shaped insulating plate having an aperture therethrough disposed in said casing on the side of said sinter mass opposite said solid electrolyte disc in a manner to enclose said sinter mass with the aid of said annular insulating member and said electrolyte; a ring member arranged between said second inwardly bent portion of said casing and the outside surface of said insulating plate, for achieving tight assemblage of the parts in the casing; and a metallic terminal member including an enlarged section immersed in said sinter mass and an elongated section passing through the aperture in said insulating plate, the cross sectional area of said enlarged section of said metallic terminal member being larger than that of the aperture.