| 摘要 |
PROBLEM TO BE SOLVED: To provide a detection element which can be used also for ultra-lean combustion where an air/fuel ratio exceeds 18 and oxygen can be accurately detected a wide range. SOLUTION: A sensor part 2 where a pair of electrodes 22 and 23 are provided on the upper and lower surfaces of a flat oxygen ion conductive solid electrolyte 21 is provided, one electrode 22 is exposed to a gas room to be measured where exhaust gas exists, and the other electrode 23 is exposed to a low-oxygen-concentration gas room A which is isolated from the gas room to be measured. The oxygen concentration of the low-oxygen-concentration gas room A is controlled to be a low constant value by an auxiliary oxygen sensor part 3 and an oxygen pump part 4 and oxygen concentration in the exhaust gas with a high oxygen concentration of at least approximately 4% can be detected by controlling it with a low value closer to approximately 1%. |
