| 摘要 |
An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed. Alternatively, the diagnosis operation may be performed based on a comparison between a total air/fuel ratio correction amount and a change of the air/fuel ratio detected by the air/fuel ratio sensor, a phase difference calculation between peaks of the air/fuel ratio or the air/fuel ratio correction coefficient, or by accumulating the differences between the air/fuel ratio and the target air/fuel ratio, and the differences between the air/fuel ratio correction coefficient and a reference value, and comparing the accumulated values. In addition, the system may detect a sensor abnormality based on the deviation in phase of the air/fuel ratio from the air/fuel ratio correction coefficient. These diagnosis operations can precisely and easily detect the occurrence of an abnormality in the air/fuel ratio sensor. As a result, the air/fuel ratio control system will not use an imprecise output from the sensor for air/fuel ratio control, thus achieving highly precise and highly reliable air/fuel ratio control. |
