Ford Motor Company Limited

Michael J Cermak

Stanley R Merchant

A high temperature thermistor and its method of fabrication are disclosed. The thermistor is fabricated from titanium dioxide ceramic forming material and is fabricated to achieve a high degree of densification approaching 100% of theoretical density. At elevated temperatures in the range of from about 700.degree. F. to about 1500.degree. F. densified titania ceramic material behaves as a semiconductor having a resistance which is responsive principally to the temperature of the thermistor element. The thermistor is fabricated by processing titania powder which includes a substantial majority of rutile phase material. The titania powder is processed to achieve a thermistor chip or member which demonstrates a high degree of density.

Titania thermistor and method of fabricating

A pair of ceramic chips, formed of similar metal oxide ceramic materials which are semiconductors at elevated temperature, are connected electrically in series and are arranged for exposure to the hot gaseous combustion by-products produced by an internal combustion engine. The chips are positioned in the exhaust gas conduit by a ceramic insulator having a plurality of longitudinal passages extending therethrough. A plurality of electrical terminal members are received within the rear of the longitudinal passages. Electrical leads extend from the chips to the terminal members through the plurality of passages and support the chips while providing electrical communication between the chips and the electrical terminals. The electrical terminals are adapted for communication to electronic and/or electrical utilization means. One of the pair of chips is processed to exhibit a rapid change in an electrical property responsive to differences in the exhaust gas chemistry and differences in exhaust gas temperature. The other of the chips is processed to exhibit a rapid change in an electrical property responsive to differences in exhaust gas temperature only. The preferred material is titania. For temperatures in the range of from about 700.degree. F. to about 1500.degree. F., the application of a reference voltage across the series connected chips will produce a substantially temperature independent voltage variation across either chip in response to changes in exhaust gas chemistry and which is relatively insensitive to changes in the exhaust gas temperature.

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Southfield, MI, United States of America

Michael J Cermak