Patent ID: 6332966
Filing Date: 2001-12-25
Classification: G01N

Abstract:
An arrangement for detecting an air/fuel (A/F) ratio, comprising:a casing having a gas cell into which exhaust gas flows and an air cell isolated from said gas cell, said casing including an outer periphery;first, second, third and fourth electrodes located in said air cell, said gas cell, said gas cell and at said outer periphery, respectively;an oxygen sensor part arranged with said casing, said oxygen sensor part providing an oxygen content signal indicative of a difference in oxygen content between said air cell and said gas cell through said first and second electrodes;an oxygen pump part arranged with said casing, said oxygen pump part urging oxygen ions to flow into and out of said gas cell through said casing in accordance with an oxygen pump signal received between said third and fourth electrodes;a heater arranged with said casing, said heater heating said oxygen sensor part and said oxygen pump part;a processing circuit which provides said oxygen pump signal to said third and fourth electrodes in accordance with said oxygen content signal and an A/F ratio signal indicative of an oxygen content in said gas cell in accordance with an electric power amount supplied to said third and fourth electrodes by said oxygen pump signal;a signal switching circuit which provides either of said A/F ratio signal or one of said oxygen content signal and a provisional oxygen content signal derived from said first and fourth electrodes; andan electronic control unit (ECU) connected to said signal switching circuit, said ECU being constructed to carry out an A/F ratio control by using said provisional oxygen content signal before an activation of said oxygen sensor part is determined in accordance with either of said oxygen content signal or said provisional oxygen content signal, and to provide a switching signal to said signal switching circuit for providing said A/F ratio signal when said activation is determined.