| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technique for simply determining the deterioration of the concentration detector of gas provided to the exhaust system or the like of an engine with high precision. <P>SOLUTION: A sensor control part 70 measures the current (first current Is1) flowing to a first sensor electrode 56b in a step S3 to store the measured value in a memory not shown in the figure. The sensor control part 70 measures the current (second current Is2) flowing to a second sensor electrode 56c in a step S6, and subsequently calculates a current ratio Ri using a formula (Ri=Is2/Is1) in a step S7. The sensor control part 70 determines whether the current ratio Ri is less than a predetermined deterioration determining threshold value Rir (e.g., 2.5) in a step S8. Since the deterioration speed of the second sensor electrode 56c is high if the concentration detector is used over a long period of time, the current ratio Ri gradually becomes small and the determination of the step S8 becomes Yes at last. Hereupon, the sensor control part 70 sets a sensor deterioration flag Fsr of an inial value 0 to 1 in a step S9. <P>COPYRIGHT: (C)2010,JPO&INPIT |
