| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio detecting device which can detect air-fuel ratios in any air-fuel ratio domain. SOLUTION: The A/F detecting section 11 of an A/F sensor 10 has a solid electrolyte layer 14 and a diffused resistor layer 13 and outputs an electric current having the value corresponding to the oxygen concentration of an exhaust gas when a voltage is applied across the exhaust gas-side and air-side electrodes 15a and 15b of the electrolyte layer 14. An oxygen supplying and exhausting section 12 has a solid electrolyte layer 16 and a pair of electrodes 15c and 15d respectively formed on both surfaces of the layer 16 and supplies oxygen to the vicinity (air chamber 18) of the air-side electrode 15b of the A/F detecting section 11 or exhausts the oxygen near the electrode 15b. A control section 30 fetches the limiting current value Ip detected by means of a current detecting section 40 and controls the oxygen supplying or exhausting amount of the oxygen supplying and exhausting section 12. To be concrete, the control section 30 controls the oxygen supplying and exhausting amount of the section 12 by variably setting the target control value of the current flowing to the electrolyte layer 16 so that the moving amounts of oxygen in the electrolyte layers 14 and 16 may become equal to each other. |
