Ford Motor Company Limited

Elmer T Heiney, Iii

Stanley R Merchant

Achyuta Achari

Shunso F Watanabe

Wells L Green

Theodore W Daykin

A motor vehicle throttle valve positioner consisting of an elongated screw means moving the throttle valve and providing two ranges of movement, one being an engine idle speed mode of operation to maintain the engine at the correct idling speed level as determined by a microprocessor or similar electronic control, the other being a speed control mode of operation wherein a chosen engine off-idle speed level is maintained, and a failsafe operation returning the throttle valve to the idle speed range in the event of electrical failure or termination of the speed control mode of operation.

Carburetor throttle valve actuator

An exhaust gas sensor electrical circuit is improved by the provision of circuit means for inhibiting reduction in the magnitude of the change in voltage signal produced in the sensor circuitry. The reduction in magnitude change would otherwise result from prolonged exposure of the sensor ceramic elements to exhaust gases produced by combustion of a rich air/fuel mixture or a lean air/fuel mixture. The sensor has a titania or other exhaust gas sensing element responsive to temperature and to the partial pressure of oxygen. A second metal oxide ceramic element also is responsive to exhaust gas sensor temperature, but is more slowly responsive to the partial pressure of oxygen in the exhaust gases. Prolonged exposure of the second element in the sensor to rich-mixture exhaust gases or to lean-mixture exhaust gases can lead to a temporary but substantial loss of output signal magnitude from the sensor in the absence of the inhibiting means of the improved circuitry.

Exhaust gas sensor electrical circuit improvement

An improved sensor having a ceramic element that undergoes a change in an electrical characteristic in response to a change in the partial pressure of oxygen in a mixture of gases to which the ceramic element is exposed. Sensors of this type are used to detect the air-fuel ratio of mixtures supplied to internal combustion engines. Prior art titania and zirconia sensors are characterized by little change in their respective electrical characteristics at operating temperatures below about 350.degree. C. A charge transfer material, platinum, has been applied to the ceramic element to facilitate or make possible the electron transfers required for sensor operation. Loss of the platinum charge transfer material by vaporization, as the result of operation at normal elevated temperatures, has been discovered to be the cause of a loss of sensor response at low sensor operating temperatures. The improved sensor has a charge transfer material comprised of an alloy of platinum and rhodium. This alloy, which preferably is 90% platinum and 10% rhodium, reduces the minimum temperature of operation for the sensor and substantially eliminates the aforementioned vaporization loss of the charge transfer material.

Ceramic element sensor

An improved exhaust gas sensor of the type having first and second titania ceramic elements which have electrical resistances varying as a function of both the temperature and the composition of exhaust gases from internal combustion engines to which the elements are exposed. The first and second titania elements are connected in series circuit in the utilization of the sensor and the resistance of the second element over the operating temperature range of the exhaust gas sensor compensates the signal of the first titania element in a manner that produces a desired signal. The desired signal is a result of variation of the second titania element resistance values when exhaust gases cycle between lean-mixture and rich-mixture compositions. The resistance values of the second titania element are intermediate the corresponding resistances of the first titania element over the temperature range. The second titania element is more dense than the first titania element. It has a density in the range from 3.2 g/cm.sup.3 to 3.8 g/cm.sup.3, i.e., between about 76% and 90% of theoretical density.

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Huntington Woods, MI, United States of America

Elmer T Heiney, Iii