| 摘要 |
PROBLEM TO BE SOLVED: To increase the responsiveness of detecting a sensor current of an air-fuel ratio sensor in an air-fuel ratio detection device, and also realize the downsizing of the device.SOLUTION: An air-fuel ratio detection device 1 comprises: a current detection resistor 5 connected in series to an air-fuel ratio detection sensor 3; first voltage application means 7 and 9 for applying a DC voltage Vp to one end of a series circuit 6 consisting of the air-fuel ratio sensor 3 and the resistor 5; second voltage application means 11 and 13 for applying a first voltage VH and a second voltage VL to the other end of the series circuit 6 while switching these voltages alternately on a prescribed cycle; amplification means 15 for amplifying voltage Vr at opposite ends across the resistor and outputting the amplified voltage; A/D conversion means 17 for converting the output voltage of the amplification means 15 from analog to digital; and arithmetic means 19. The A/D conversion means 17 executes A/D conversion each time the second voltage application means 11 and 13 switch the applied voltages. The arithmetic means 19 calculates the sensor current and impedance of the air-fuel ratio sensor 3 by using the results of two successive A/D conversions by the A/D conversion means 17. |
