Capacitive A/F sensor

U.S. Patent Number: 5389224

Abstract: A sensor for determining the stoichiometric air to fuel ratio (A/F) at the intake of an internal combustion engine is based on a capacitive device in the exhaust stream which can be used to measure the change in the workfunction of an appropriate material which occurs at the stoichiometric point and which forms one of the two interacting elements of the capacitor. To measure A/F over an extended range about stoichiometry the material whose workfunction changes is made the working electrode of an oxygen concentration cell using a solid electrolyte. Oxygen pumping to and from that surface can change the magnitude of the workfunction allowing for a feedback control method for keeping the workfunction constant despite changes in the A/F so that the required pump current becomes a measure of the A/F.

Inventors: Hetrick; Robert E. (Dearborn Heights, MI)

Assignee: Ford Motor Company (Dearborn, MI)

Application Number: 08/084,498

Issued: 1995-02-14

Expired: 2007-02-14

Classes: 204/425 ; 123/438; 204/426; 204/427; 324/470

Field of search: 204/424,425,426,427,153.18 324/470,33 123/438

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