| 摘要 |
PURPOSE:To control an air fuel ratio over a wide range extending from the lean area to the rich area by a simple arrangement by combining an oxygen pumping element and an oxygen gas sensing element. CONSTITUTION:In the lean state, negative potential is applied to an inner electrode and a positive potential is applied to an outer potential that is not contacted with a gas diffusion part 4 of a pair of electrodes constituting an oxygen pumping element 2 together with a solid-state electrolyte 1. Oxygen ions are then moved in the electrolyte 1 from inner to outer electrodes to pump out the oxygen gas in the diffusion part 4. The oxygen partial pressure of the detected gas in the diffusion part 4 formed by a porous body 7 to limit the flow of measured gas is changed and detected by an oxygen gas detection element 2 provided to the diffusion part 4 as the resistance value. When the current supplied to the element is controlled so that the resistance value will be constant, the oxygen gas content ratio is determined substantially linearly from the current volume. In such a way, for the rich state, the air fuel ratio can be controlled in the feedback fashion on the basis of the wide range of measurement from the lean state to the rich state by a simplified constitution requiring no reference oxygen source. |
