| 摘要 |
PURPOSE:To detect an air fuel ratio correctly in a logical and thin regions of air fuel ratio by supplying a large current to a solid-state electrolytic oxygen pump element and causing output voltage variation which is abrupt at the logical air fuel ratio point across a solid-state electrolytic oxygen concentration cell element. CONSTITUTION:The solid-state electrolytic oxygen pump element 6 and solid- state electrolytic oxygen concentration cell element 10 are provided at a fine interval (a) in an exhaust pipe 1. The element 10 varies in electromotive force (e) with the air fuel ratio for supplying a large current from a constant current source 19 to the element 6 and the variation is measured through the terminal 20 of an electronic control part 16 to obtain an electromotive force (e)-air fuel ratio A/F curve which varies abruptly at the logical air fuel ratios 14.7. The air fuel ratio is detected accurately from a thick region close to the logical air fuel ratio to a thin region. Further, a switch 18 is operated to lead out variation in electromotive force (e) based upon a set concentration boundary P through a terminal 17 and feedback control is performed to perform desired air fuel ratio control. |
