| 摘要 |
PROBLEM TO BE SOLVED: To make compensable a rich drift by applying a voltage pulse un related to detection voltage to a pump cell at the stable operation of a measur ing sensor to depolarize the measuring sensor. SOLUTION: When a fuel/air mixed gas is present in a lean area, a measuring sensor 10 gets into a rich drift. The measuring sensor 10 supplies the detection voltage UD corresponding to a high oxygen content generated in exhaust gas 24 to a circuit device 32. A timing element 50 detects the continuous time and magnitude of the detection voltage UD and sends out a signal 52 when the detected values are within a predetermined numerical value range corresponding to lean operation. A switching means 54 changes over the anode current of the pump current IP corresponding to the concn. of oxygen in a short-time pulse like state by the control of the signal 52. Corresponding to this changeover, oxygen ions are transported to an electrode 40 from the electrode 38 of a pump cell 14 from a hollow space 28. Herein, the pulse frequency changing the polarity of the short-time pump current IP and pulse length are adjusted in order to correct only the rich drift of the measuring sensor 10. |
