Automotive Exhaust Sensors Using Titania Ceramic

Abstract

<div class="htmlview paragraph">The resistivity of titania (TiO<sub>2</sub>) ceramic depends upon the partial pressure of oxygen (P<sub>O<sub>2</sub></sub>) in the atmosphere surrounding the ceramic. Because there is a functional relationship between the P<sub>O<sub>2</sub></sub> of the equilibrated exhaust gas and the air to fuel ratio (A/F) operating point of the internal combustion engine, the resistance of a TiO<sub>2</sub> ceramic sensor, when temperature controlled, can be used to determine quantitatively the A/F. TiO<sub>2</sub> sensors utilizing these principles have been built and found to work particularly well in the region rich of stoichiometry. Control of the A/F in the region rich of stoichiometry is desirable for engine/catalyst systems designed to meet low NO<sub>x</sub> emission levels.</div> <div class="htmlview paragraph">This paper reports on the design details and operating features of an experimental TiO<sub>2</sub> sensor and its associated electronic controller. In addition, experimental results are reported for the sensor/controller combination operating in engine dynamometer tests and on vehicles with feedback-controlled, electronic fuel injected engines. These results indicate that feedback control using the TiO<sub>2</sub> sensor represents a possible means of achieving the precision A/F control required to obtain efficient performance of vehicles using NO<sub>x</sub> catalysts.</div>