| 摘要 |
PURPOSE:To detect the concn. of oxygen in measuring gas and that in a lean air/fuel ratio region, by detecting voltage corresponding to the oxygen partial pressure ratio of the measuring gas and the atmosphere and controlling the oxygen partial pressure of a measuring gas introducing part. CONSTITUTION:A small hole 43 is opened to the end part of a cylinder 42 to introduce gas to be measured while an oxygen ion conductive solid electrolyte 45 having a flat plate shape is provided in the cylinder 42 to partition the cylinder 42 into a gas introducing part 47 and an atmosphere introducing part 46. The sensor anode 50 and cathode 51 of an oxygen partial pressure ratio detection part are provided to the electrolyte 45, and the pump anode 52 and cathode 53 of an oxygen partial pressure control part are provided thereto. Then, potential Vs by the oxygen partial pressure ratio based on the oxygen concn. in the atmosphere and that in the measuring gas is detected by the sensor anode 50 and the cathode 51. Further, the difference of reference voltage Vo when a theoretical air/fuel ratio is 1 and the potential Vs is detected and a current is supplied to the oxygen partial pressure control part to control oxygen partial pressure and the air/fuel ratio is continuously detected. As a result, the oxygen concn. of gas to be measured can be detected from detected potential by an oxygen partial pressure ratio with good accuracy. |
