| 摘要 |
PURPOSE:To prevent exhaust gas from being excessively diluted by decreasing the quantity of secondary air to be supplied for enriching the air fuel ratio of a mixture. CONSTITUTION:In a case where there is a need to enrich the air fuel ratio as the case of low load driving, secondary air is ejected through the first secondary air supply passage 12 to an exhaust gas component concentration sensor 10, and a false signal is generated so that the air fuel ratio detected by the exhasut gas component concentration sensor 10 becomes leaner than the theoretical air fuel ratio. The air fuel ratio is enriched by this false signal to improve the drivability. In this step, at the initial time when the supply of secondary air is started from the passage 12, the exhasut gas is diluted by secondary air, and moved to the lean side. However, since the quantity of secondary air supplied is slight, the movement is also slight, and hence the lowering of the purification function of NOx in this transient period can be suppressed. |
