Abstract: An NO.sub.x absorber (18) is arranged in an exhaust passage of an internal combustion engine. The NO.sub.x absorber (18) absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) is lean while releases the absorbed NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) becomes the stoichiometric air-fuel ratio or rich. An air-fuel ratio sensor (22) is arranged in the exhaust passage downstream of the NO.sub.x absorber (18). When the air-fuel ratio detected by the air-fuel ratio sensor (22) is switched from lean to rich after the air-fuel ratio of the exhaust gas flowing into NO.sub.x absorber (18) is switched from lean to rich, it is decided that the releasing action of NO.sub.x from the NO.sub.x absorber (18) is completed.

Abstract: An air-fuel ratio detector and an air-fuel ratio measuring method for detecting an oxygen density in an exhaust gas emitted from the internal combustion engine of an automobile. The air-fuel ratio detector has a tubular body and a pair of partition members dividing the tubular body into a closed-end section and an open-end section. At least one of the partition members comprises a solid electrolyte permeable to oxygen ions. A pair of electrodes is mounted on opposite surfaces of the solid electrolyte and connected to a DC power supply, thus constituting an oxygen pump. Another pair of electrodes is mounted on one of the partition members and connected to a DC power supply, thus constituting a limited-current oxygen sensor. Oxygen is introduced into a space between the partition members at all times by the oxygen pump to maintain the gas, which has been supplied through a gas dispersion member into the space, lean.

Abstract: A detector and a measuring method for detecting an air-fuel ratio in an internal combustion engine or the like. The detector has a tubular body having a closed end, a solid electrolyte permeable to oxygen ions which divides the interior of the tubular body into a closed-end section and an open-end section, and electrodes mounted on opposite surfaces of the solid electrolyte. One pair of the electrodes on the opposite surfaces of the solid electrolyte is connected to a circuit for detecting an electromotive force, thus constituting an oxygen sensor. The other electrode pair is connected to a DC power supply, thus constituting an oxygen pump. The oxygen sensor detects the quantity of oxygen in a gas supplied through a gas dispersion member. The direction of flow and magnitude of and electric current in the oxygen pump are controlled on the basis of an output from the oxygen sensor for enabling the gas to have a stoichiometric air-fuel ratio.

Abstract: A method for detecting the oxygen concentration of a gas to be measured is disclosed using the limiting current type oxygen sensor. The method is characterized in that the relationship of an inclined straight line between the voltages applied to the oxygen sensor and the currents outputted therefrom is determined in such a manner that the inclined straight line may pass through the flat portions of the limiting current in the voltage-current characteristics curves at the different oxygen concentrations. The relationship between the outputted currents and the oxygen concentrations at the flat portion is such that when a given magnitude of voltage is applied to the oxygen sensor to cause it to output a current, a voltage which corresponds to this current at the inclined straight line is determined. The voltage thus determined is applied to the oxygen sensor to cause it to output a current.

Abstract: An oxygen sensor element with a ceramic heater, having a cylindrical element body formed of an oxygen ion permeable solid electrolyte with one end closed, inner and outer electrodes formed on the inner and outer surfaces of the element body, and an electrode protective layer covering at least one of the inner and outer electrodes, the ceramic heater including a bar-like ceramic core member, a ceramic covering layer which covers the outer surface of the ceramic core member and a heating member disposed in the interface between the core member and the covering layer.

Abstract: An oxygen sensor element having an oxygen ion-permeable solid electrolyte having a tabular or columnar shape and electrode layers formed on the solid electrolyte. At least one of the electrode layers is composed of a fired body having a uniform structure consisting of 100 weight parts of a metal and 0.1 to 10 weight parts of a glass which consists of the following materials in molar amounts: SiO.sub.2, 62-75%; ZrO.sub.2, 7-11%; R.sub.2 O, 13-23%; R'O, 1-10%; Al.sub.2 O.sub.3, 0-4%; B.sub.2 O.sub.3, 0-6%; Fe.sub.2 O.sub.3, 0-5%; CaF.sub.2, 0-2%; and TiO.sub.2, 0-4%; wherein R.sub.2 O is Na.sub.2 O which is substantially pure or is substituted by Li.sub.2 O within 2 mole percent thereof, and R'O is an oxide selected from the group consisting of the alkaline-earth metal oxides, ZnO and MnO. Disclosed also is a method of producing the oxygen sensor element.

Abstract: A leanness sensor has a sensor element made of an oxygen-permeable solid electrolyte and having a cylindrical form or a form like a vessel closed at one end thereof. The sensor element is provided with metallic electrodes formed on the inner and outer surfaces thereof. An inner metallic member and an outer metallic member are mounted on the sensor element and electrically connected to the metallic electrodes. The sensor element is fixed to the inner side of the end portion of a cylindrical insulating tube.

Abstract: A lean sensor for sensing oxygen concentration in exhaust emissions, including a sensor element consisting of a tabular solid electrolyte having opposed sides provided with electrodes with at least one surface thereof coated with a porous coating layer, an element fixing plate having an element fitting hole to which the element is fitted, and a pair of heat-resistant insulating support plates having opposing windows and clamping therebetween the element fixing plate together with the sensor element disposed in the windows. In this way, it is possible precisely to locate the element in relation to the plate and to improve the bonding strength and reliability while reducing the size of the sensor as a whole.

Abstract: There is disclosed a system for controlling vaporized hydrocarbon of fuel for a gasoline engine wherein the vaporized hydrocarbon is led from a carburetor float chamber to a canister through a pipe in which a chamber for separating fuel and vapor is provided.