| 摘要 |
PURPOSE:To enable to control the air-fuel ratio exactly, by feedback controlling the air-fuel ratio on the basis of the output value of an oxygen pump type air- fuel ratio sensor constituted by an ion-conductive solid electrolyte. CONSTITUTION:An air-fuel ratio sensor 2 disposed in an exhaust pipe 1 consists of a solid electrolyte oxygen pump 6 consisting of an ion-conductive solid electrolyte (stabilized zirconia) 3 in the form of a plate having a thickness, for instance, of about 0.5mm. and having platinum electrodes 4, 5 attached to both side faces thereof an a solid electrolyte oxygen sensor 10 similarly having platinum electrodes 8, 9 attached to both side faces thereof. These pump 6 and sensor 10 are juxtaposed by a support bed 11, for instance, with a small spacing (d) of about 0.1mm.. The electromotive force (e) kept at a prescribed voltage V1 or V2 by an electronic control unit 12 is changed arbitrarily at predetermined intervals during operation of an engine, and the air-fuel ratio is detected from the output signal corresponding to pump current IP before and after the above changing of the electromotive force (e). Then, the output corresponding to the air-fuel ratio is calculated by judging whether the output of the air-fuel ratio sensor is richer or leaner than the theoretical air-fuel ratio. |
