| 摘要 |
PURPOSE:To achieve a higher air/fuel ratio detection accuracy in a starting warming up, by a method wherein the measurement of an electromagnetic force is performed until a detector is heated up to a required temperature after the warming up and then, a limiting current is measured. CONSTITUTION:An air/fuel ratio detector starts operation simultaneously with the start up of an internal combustion engine and the energization of a heater 15 is turned ON to heat an air/fuel ratio sensor 1. The sensor 1 is initially connected to a theoretical air/fuel ratio detection circuit section 4 and an electromotive force signal of an oxygen concentration battery is detected to apply an output Vs thereof to an air/fuel controller 10. When the sensor 1 is heated sufficiently to make accurate measurement of an air/fuel ratio ready with a pumping of oxygen ions, a signal to the effect is sent to an change-over switch 6 to switch the connection of the sensor 1 over to a linear air/fuel ratio detecting circuit section 5 for detection of oxygen ion current from the detection of the electromotive force. At the same time, a switching signal is applied to the device 10 from a sensor temperature detection circuit section 2 to switch the signal Vs over to a linear output signal V0. Thereafter, an air/fuel ratio control is performed by the signal V0 thereby enabling highly accurate and efficient air/fuel ratio control. |
