| 摘要 |
PURPOSE:To detect air fuel ratio over a wide range from a rich region to a lean region by detecting the inflow current and internal resistance value of such an oxygen pump part that a prescribed output is obtained by an oxygen concentration sensor. CONSTITUTION:A reference electrode 12 and an anode electrode 13 are arraged successively on one surface of a solid-state electrolyte 11,and a cathode electrode 14 is provided on the other surface. An oxygen concentration sensor part 16 consists of the solid-state electrolyte 11, reference electrode 12, cathode electrode 14, and porous protection layer 15, and a pump 17 consists of the solid-state electrolyte 11, anode electrode 13, cathode electrode 14, and porous protection layer 15. The pump current Ip of a pump part 17 is controlled by switching the output voltage Vs of the sensor part 16 so that air fuel ratios change abruptly, and such characteristics that the internal resistance of the pump part 17 varies abruptly about the ideal air fuel ratio are utilized to add the judgement of this internal resistance to the judgement of the air fuel ratio based upon the pump current Ip, thereby detects air fuel ratio over the wide range from the rich region to the lean region. |
