Abstract: The invention relates to an air/fuel ratio detection apparatus. This apparatus includes (a) a heater portion having an elongate cylindrical shape and heating by applying electricity thereto from outside; (b) a solid electrolyte layer surrounding the heater portion and being activated by heat to conduct oxygen ions therethrough; (c) first and second electrodes in contact with the solid electrolyte layer and being away from each other such that pumping voltage is applied by the first and second electrodes to the solid electrolyte layer; (d) a reference electrode for outputting an air/fuel ratio detection signal, the reference electrode being formed on the solid electrolyte layer and being away from the first and second electrodes; and (e) a diffusion layer made of a porous material and surrounding periphery of the solid electrolyte layer to cover the first and second electrodes and the reference electrode.

Abstract: The invention relates to an air/fuel ratio detection apparatus for a gas. This apparatus includes (a) a heater portion having an elongate cylindrical shape; (b) a solid electrolyte layer surrounding the heater portion and activated by heat to conduct oxygen ions therethrough; (c) a first electrode positioned between the heater portion and the solid electrolyte layer; (d) second and third electrodes in contact with an outer surface of the solid electrolyte layer and away from each other; (e) a first voltage applying device for applying a first voltage between the first and second electrodes; (f) a second voltage applying device for applying a second voltage between the first and third electrodes, the second voltage being higher than the first voltage; and (g) a diffusion layer made of a porous material and covering the second electrode to adjust transmission of the gas to the second electrode.

Abstract: The invention relates to an oxygen-concentration detecting element including (a) a base member constructed of a first insulating material; (b) an electric heater layer formed on the base member to generate a heat when electrically energized; (c) an oxygen-detecting laminated unit formed on the base member, the unit including a solid electrolyte layer activated by the heat; (d) a printed protecting layer covering the base member, the electric heater layer and the oxygen-detecting laminated unit, being constructed of a mixture of a second insulating material and a solid electrolyte material, and having a porous structure provided with voids derived from a void forming agent contained in an amount of 10-80 volume %, based on a total volume of the second insulating material and the void forming agent, prior to a baking for producing the oxygen concentration detecting element; and (e) a porous protecting layer covering the printed protecting layer.

Abstract: The invention relates to an oxygen-concentration detecting element including (a) a base member of a first insulating material; (b) an electric heater layer formed on the base member to generate a heat when electrically energized; and (c) an oxygen-detecting laminated unit formed on the base member, the unit including a solid electrolyte layer and inner and outer electrodes interposing the solid electrolyte layer therebetween. The inner electrode may be constructed of a noble metal material and voids that are dispersed in the noble metal material and are derived from a void forming agent. The oxygen-concentration detecting element may include a penetration layer for allowing penetration of oxygen therethrough, between the outer surface of the base member and the oxygen-detecting laminated unit. The penetration layer is extended in the axial direction of the base member from the position of the unit.

Abstract: The invention relates to an air/fuel ratio detection apparatus for a gas. This apparatus includes (a) a heater portion having an elongate cylindrical shape; (b) a solid electrolyte layer surrounding the heater portion and activated by heat to conduct oxygen ions therethrough; (c) a first electrode positioned between the heater portion and the solid electrolyte layer; (d) second and third electrodes in contact with an outer surface of the solid electrolyte layer and away from each other; (e) a first voltage applying device for applying a first voltage between the first and second electrodes; (f) a second voltage applying device for applying a second voltage between the first and third electrodes, the second voltage being higher than the first voltage; and (g) a diffusion layer made of a porous material and covering the second electrode to adjust transmission of the gas to the second electrode.

Abstract: The invention relates to an air/fuel ratio detection apparatus. This apparatus includes (a) a heater portion having an elongate cylindrical shape and heating by applying electricity thereto from outside; (b) a solid electrolyte layer surrounding the heater portion and being activated by heat to conduct oxygen ions therethrough; (c) first and second electrodes in contact with the solid electrolyte layer and being away from each other such that pumping voltage is applied by the first and second electrodes to the solid electrolyte layer; (d) a reference electrode for outputting an air/fuel ratio detection signal, the reference electrode being formed on the solid electrolyte layer and being away from the first and second electrodes; and (e) a diffusion layer made of a porous material and surrounding periphery of the solid electrolyte layer to cover the first and second electrodes and the reference electrode.