Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1992-07-14
1994-01-04
Tung, T.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204426, 204427, 324470, G01N 2726
Patent
active
052757129
ABSTRACT:
A sensor determines a wide range of air-to-fuel ratio values (A/F) about the stoichiometric A/F in a gaseous mixture which has oxidizing and reducing species as might be found in an automotive exhaust. The sensor includes a surface that serves simultaneously as the working electrode of a solid-state oxygen concentration cell and as a surface whose workfunction changes from a higher to a lower value as the oxidizing and reducing species in the adjacent gas phase, and in interaction with the surface, pass from an excess oxidizing to the excess reducing condition about the stoichiometric ratio. In one embodiment, the surface exposed to the gas in question is the emitter electrode of a thermionic diode which emits positively charged alkali ions into the exhaust ambient where they are collected by a nearby collector electrode. Changes in the ratio of the oxidizing and reducing species about the stoichiometric ratio produce corresponding changes in the thermionic emission. Oxygen pumping to or from the working electrode modifies the thermionic emission in a systematic way to provide a pumping method of operation in which the magnitude of the pump current required to maintain the thermionic emission current at some preset value despite changes in the A/F ratio of the ambient leads to a relationship between pump current and A/F that can be used to sense the A/F.
REFERENCES:
patent: 3416070 (1968-12-01), McGowan, Jr.
patent: 4272329 (1981-06-01), Hetrick
patent: 5028544 (1991-07-01), Rasulev et al.
SAE Paper No. 860409 "Wide-Range Air-Fuel Ratio Sensor" (no date available).
Hetrick Robert E.
Schamp Allen L.
Abolins Peter
Bell Bruce F.
Ford Motor Company
May Roger L.
Tung T.
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