| 摘要 |
PURPOSE:To ensure the detection of the air-fuel ratio in an excessively rich region on fuel in an engine, by keeping the electromotive force of an oxygen sensor at a specified value of 50-100mV. CONSTITUTION:An air-fuel ratio sensor 2 is constituted by the following devices: a solid electrolyte oxygen pump 6, which is constituted by providing platinum electrodes 4 and 5 on both side surfaces of a plate shaped ion transmitting solid electrolyte (stabilized zirconia) 3 having a thickness of about 0.5mm.; a solid electrolyte oxygen sensor 10, which is constitued by providing platinum electrodes 8 and 9 on both side surfaces of a plate shaped ion transmitting solid electrolyte 7 like the oxygen pump 6; and a supporting table 11, on which the oxygen pump 6 and the oxygen sensor 10 are arranged so as to face each other with a minute gap (d) of about 0.1mm. being provided. When an electromotive force is made to be 50mV or more, the air-fuel ratio in an excessively rich region of fuel can be detected based on an output signal corresponding to a pump current Ip. When the electromotive force is made to be 100mV, the change in the pump current Ip with respect to the change in the air-fuel ratio becomes large. When the air-fuel ratio becomes small, the pump current Ip becomes extremely large, and the oxygen pump 6 is broken. |
