Abstract: An air/fuel ratio sensor is described, comprising an oxygen concentration electrochemical cell and an oxygen pump disposed in a face-to-face relationship with a gap being formed therebetween, the side of said electrochemical cell opposite the side facing said oxygen pump being in contact with the atmosphere, said gap forming a gas diffusion compartment that communicates with a gas to be analyzed by a gas diffusion limiting means, wherein the gap existing between said oxygen concentration electrochemical cell and said oxygen pump has a width of no more than 0.2 mm and no less than 0.01 mm.

Abstract: An air/fuel ratio sensor is described, comprising an oxygen concentration electrochemical cell and an oxygen pump disposed in a face-to-face relationship with a gap being formed therebetween, the side of said electrochemical cell opposite the side facing said oxygen pump being in contact with the atmosphere, said gap forming a gas diffusion compartment that communicates with a gas to be analyzed by a gas diffusion limiting means, wherein the gap existing between said oxygen concentration electrochemical cell and said oxygen pump has a width of no more than 0.22 mm and no less than 0.01 mm.

Abstract: In the joining structure of the solid electrolytic element, terminals connected to the heating element and the electrodes are attached through metallic oxide layers onto the solid electrolytic layer. The thermal conductivity coefficient of the metallic oxide layers is larger than that of the solid electrolytic layer. The thermal expansion coefficient of the metallic oxide layers is the same as or smaller than that of the solid electrolytic layer. Consequently, when the lead wires are soldered to the terminals, heat is quickly conducted to the terminals, enhancing the fluidity and the solderability of the soldering material. Since excess heating is not required for soldering, the solid electrolytic layer is prevented from deteriorating due to heat. Since a low-melting solder is not used, the joining structure has high heat resistance. Moreover, during soldering, the metallic oxide layers do not detach from the solid electrolytic layer due to heat.

Abstract: A method for producing an oxygen detection element having uniform pores and an excellent durability against toxic matter contained in the measurement gas. The method includes a first step of applying a paste to be sintered to form a catalytic electrode layer onto at least a part of an oxygen-ion conductive solid-state electrolytic body, and sintering the paste to thereby form said catalytic electrode layer at a predetermined position on said surface of said solid-state electrolytic body after sintering, and a second step of forming an electrode protection layer for coating and protecting at least a part of the catalytic electrode layer either after or simultaneous with the first step. In a first embodiment, the paste contains mainly a noble metal powder acting as a catalyst and an organic metal compound, in a second embodiment mainly co-precipitated powder consisting of a noble metal and a metal hydroxide, and in a third embodiment mainly noble metal powder and a powder of a metal other than a noble metal.

Abstract: An oxygen sensor comprising a hollow cylindrical member closed at one end but open at the other to admit a reference gas. There is at least one radial through-hole in the hollow cylindrical member. An oxygen-ion conductive solid electrolyte later has at least one pair of electrodes on its opposite sides. The electrolyte layer is wrapped around the hollow cylindrical member with the electrode on its inner side facing the through hole. In other embodiments, an oxygen sensor is provided which is very insensitive to the direction of flow of the gas to be analyzed. The electrodes of the sensor are spaced at substantially equal intervals on the circumference of a cylindrical solid electrolyte layer in registry with through-holes formed in a hollow tubular member surrounded by the electrolyte layer. A heating unit may be formed on either the inner or outer surface of the solid electrolyte layer.