| 摘要 |
A device for use in exhaust gases of internal combustion engines to detect changes in air/fuel ratio. The device has a body of a transition metal oxide, such as TiO2, with a first pair of electrodes attached thereto to measure a change in the resistance of the transition metal oxide in response to a change in the air/fuel ratio. The device includes a combination of a porous layer of an oxygen ion conductive solid electrolyte such as ZrO2 arranged such that the exhaust gas comes into contact with the transition metal oxide body always by diffusion through the solid electrolyte layer and a second pair of electrodes arranged so as to force a DC current to flow in the solid electrolyte from selected one of these electrodes to the other. Migration of oxygen ions in the solid electrolyte layer caused by the flow of the current has the effect of increasing or decreasing the supply of oxygen to the transition metal oxide thereby producing a difference between an oxygen partial pressure at the surface of the transition metal oxide body and the exterior exhaust gas. Therefore, the resistance of the transition metal oxide exhibits a sharp change in response to a change in the air/fuel ratio across a nonstoichiometric ratio which is above or below the stoichiometric ratio depending on the direction of flow of the current.
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