Limiting current type oxygen sensor and method of sensing and measuring oxygen concentrations using the same

Abstract

A limiting current type oxygen sensor comprises an ion conductor, a pair of electrodes, a gas diffusion mechanism for supplying a diffusion-rate-determined gas, and a heater for heating the ion conductor. The gas diffusion mechanism includes a gas diffusion bore and an internal space communicating with the gas diffusion bore. In a first embodiment, the gas diffusion mechanism is configured such that the thickness (lin) of the internal space is formed equal to or larger than the bore diameter (S1) of the gas diffusion bore. This makes it possible to dominate diffusion-rate-determinateness in the gas diffusion bore and minimize the influence of diffusion-rate-determinateness in the internal space, thereby sensing the limiting current value accurately. In a second embodiment, the gas diffusion mechanism is configured such that an oxygen concentration gradient within the internal space satisfies the following expression: 1 / I lim = (1 / 4FDC o2 ){(l / S) + (l in / S in which is based on a relationship between the Faraday constant (F); a diffusion coefficient (D); an oxygen concentration (C o2 ); a bore area (S) of the gas diffusion bore; a bore length (1) in the axial direction of the gas diffusion bore; a distance (l in ) in the internal space between the first elextrode and the inner surface opposed thereto; an effective cross section (S in ) of the internal space; and an output current value (I lim ).

Description

[0001] This application claims priority from Japanese Patent Application Nos. 2006-176882 and 2006-176883 filed on June 27, 2006, the contents of which are incorporated herein by reference. technical field [0002] The present invention relates to a limiting current type oxygen sensor for sensing and measuring oxygen concentration and a method of sensing and measuring oxygen concentration using the oxygen sensor. Background technique [0003] As is generally known, the limiting current type oxygen sensor can be made of, for example, yttrium oxide (Y 2 o 3 ) An ion conductor composed of an additive-stabilized zirconia (yttria-stabilized zirconia: YSZ) solid electrolyte. Fig. 10 is a schematic diagram illustrating the structure of a conventional limiting current type oxygen sensor. As shown in FIG. 10 , a generally conventional limiting current type oxygen sensor 100 includes an ion conductor 101 of solid electrolyte, an anode electrode 102 and a cathode electrode 103 of por...

AI Technical Summary

Problems solved by technology

In this sensor, in the current limiting region where the oxygen concentration is 1% or less, the limiting current value may not satisfy the condition of the above expression (1)

Therefore, the oxygen concentration cannot be accurately sensed and measured

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