| 摘要 |
<P>PROBLEM TO BE SOLVED: To output a detection value required for controlling an engine even if a gas sensor is abnormal. <P>SOLUTION: A gas concentration detector has a monitor cell 1b sensitive to oxygen, and a sensor cell 1c sensitive to oxygen and NO<SB>x</SB>, and detects the concentration of NO<SB>x</SB>from the difference in the detection value of both the cells 1b, 1c. In the gas concentration detector, as a range for the normal detection value of the monitor cell 1b, the range of the detection value estimated, based on the operating state of an internal combustion engine is set to be a reference range. The actual detection value of the monitor cell 1b is determined whether it is outside the reference range or not. When the result of determination is affirmative, a detection system comprising the monitor cell 1b and its detection circuit is decided to be abnormal, and a prescribed reference value in the reference range is outputted in place of the actual detection value of the monitor cell 1b, where a detection error caused by the abnormality is large. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
