Workfunction based A/F sensor

Details Workfunction based A/F sensor Workfunction based A/F sensor

1992-07-13

1994-05-10

Niebling, John

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204426, 204427, 324470, 123438, G01N 2726

Patent

active

053104749

ABSTRACT:
A sensor for determining the stoichiometric air to fuel ratio (A/F) at the input to the cylinders of an internal combustion engine which is based on measuring the change in the workfunction of a material which occurs when the oxidizing and reducing species in the adjacent gas phase are at or near their stoichiometric ratio. In one method the sensor includes a material which is capable of thermionically emitting alkali metal or other appropriate ions into an exhaust gas atmosphere where they are subsequently collected by a nearby collector electrode and the magnitude of the emission current is measured. The interaction of the emitting surface with the gas phase reversibly changes the workfunction of the emitting surface from large to smaller values as that gas phase is varied through the stoichiometric ratio with respect to the amounts of the oxidizing and reducing species in the gas. Such a change in workfunction of the surface is accompanied by a change in the rate of the thermionic emission at the stoichiometric ratio thereby sensing that ratio in the gas phase which is proportional to the A/F at the input to the cylinders.

REFERENCES:
patent: 3416070 (1968-12-01), McGowan, Jr.
patent: 4272329 (1981-06-01), Hetrick
patent: 5028544 (1991-07-01), Rasulev et al.
H. Dietz, W. Haecker, and H. Jahnke, Advances in Electrochemistry and Electrochemical Engineering, vol. 10, Wiley, New York, p. 1 (1977).
E. M. Logothetis, Ceramic Engineering Science Proceedings, 8th Automotive Materials Conference, 1, 281 (1980).

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