Toyota Jidosha Kabushiki Kaisha

Shirou Kimura

Takashi Kamo

Shigenori Sakurai

Toshinobu Furutani

Mari Okazaki

Yoshio Torisu

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. The oxygen concentration is determined from the current thus outputted with reference to the outputted current-oxygen concentration conversion straight line. There is also disclosed a method for controlling the air-to-fuel ratio of a gas from an engine using the above voltage-current characteristic curves, inclined straight line and outputted current-oxygen concentration.

Method for detecting an oxygen concentration and a method for

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.

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Toyota, Japan

Shirou Kimura