| 摘要 |
PURPOSE: To prevent erroneous operation of a control system due to an output signal from an oxygen concentration detector by stopping the closed loop control or the current control for a solid state catalyst in a region where the excess air rate of a gas to be detected is equal to 1 or below. CONSTITUTION: Under a state where the excess air rate λ of a gas to be measured is lower than 1, a current is generated due to electronic conduction and thereby the current control is stopped to keep the level of current I flowing through an electrolyte 1 at O. When a state of λ>1 is set, the operation is started while keeping the output voltage from a voltage detector 3 at a constant level. When the outside partial pressure PM of a diffused resistor 6 drops to cause lowering of λ, the partial pressure PV of oxygen in a chamber 5 drops to cause increase in the voltage V. On the other hand, when the partial pressure PM increases, the partial pressure PV also increases to cause lowering of the voltage V. When λ<1, erroneous operation of the control system can be prevented through closed loop control of fuel, air flow controller or through closed loop control with negative current I. The current 1 is set positive at the time of transition from a state where λ<=1 to a state where λ>1. |
