AFR sensor

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors disposed on the upstream and the downstream of the catalyst which is installed in the exhaust passage of the engine and has oxygen storage effect, an air-fuel ratio correction amount is calculated in accordance with the output of the upstream O 2 sensor, and the actual air-fuel ratio is adjusted in accordance with the calculated air-fuel ratio correction amount. Further, the determination of the deterioration of the catalyst is carried out in accordance with the output of the second O 2 sensor when the air-fuel ratio of the engine is adjusted.

Abstract: DOUBLE AIR-FUEL RATIO SENSOR SYSTEM CARRYING OUT LEARNING CONTROL OPERATION ABSTRACT OF THE DISCLOSURE In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. When a change of an air-fuel ratio correction amount or a change of an air-fuel ratio feedback control parameter calculated in accordance with the output of the downstream-side air-fuel ratio sensor is small, a learning correction amount is calculated so that a mean value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In order to expand current atmospheric methane monitoring capabilities, we investigated the performance of an off-the-shelf, low-cost, metal oxide based methane (CH4) gas sensor. A sensor assembly was designed that powered the gas sensor and its resistive heater, provided ancillary temperature (T) and relative humidity (rH) measurements, and controlled sensor read-out and data storage. After calibrating the gas sensor with respect to methane concentration ([CH4]), T, and rH, we were able to estimate the [CH4] of lab air over a period of 31 days for a large range of T and rH conditions with a systematic error of −1.0 ppm and a variable error within ±1.7 ppm. The sensor showed no significant drift in [CH4] estimate. We show that sensor accuracy can likely be improved by optimizing the voltage regulator that powers the gas sensor’s heater, and by measuring and compensating for the difference in partial oxygen pressure of the air that was sampled during calibration and validation experiments. Such improvements are expected to allow the use of the sensor assembly for fence-line methane monitoring, for example near fossil fuel extraction sites. In its current form, the sensor assembly is suitable for detecting fugitive methane from leak-prone equipment.

Abstract: An air-fuel ratio sensor includes a sensor element inserted through a cylindrical housing for detecting an air-fuel ratio in an atmosphere of unburnt gas, and a measured gas side cover disposed on an end of the cylindrical housing so as to cover the sensor element and defining an inside chamber for storing therein a gas to be measured. The cover has a nested structure composed of a plurality of cup-shaped cover members disposed one inside another, each cover member having a gas inlet hole formed in a side wall thereof and a bottom hole formed in a bottom wall thereof. The gas inlet hole of an innermost one of the plural cover members that directly faces the sensor element is offset from an air-fuel ratio detecting portion of the sensor element toward the housing in an axial direction of the sensor.