| 摘要 |
PURPOSE:To obtain a highly resposive, highly accurate oxygen detecting sensor by forming a first cell part at one side of solid electrolyte, forming a second cell part at the other side, and providing an oxygen reference electrode in the second cell part. CONSTITUTION:This sensor comprises a laminated body, wherein a lean cell 12, a Stoick cell 13 and a heater 14 are arranged in zirconia solid electrolyte 11. The cell is constituted of four electrodes. The air fuel ratio of a lean region is detected with a flowing pumping-current value Ip (the limit electrode value, which is unequivocally determined by diffusion control) when the lean cell 12 is excited with a voltage EL. A theoritical air-fuel ratio is detected with electromotive force elambda, which is generated when the Stoick cell 13 is excited with a current value Ip* from a current source. At this time, the exciting voltage of the lean cell is controlled so that the electromotive force of the oxygen reference electrode becomes equal to the preset voltage. Thus, the driving circuit of the sensor is easily constituted. When the preset voltage is made variable in response to the excess air ratio in the lean region, the response is improved. |
