| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an EGR control system that can reduce the amount of NOx emission by accurately controlling actual intake oxygen concentration to a target value, even if there are variations in flow rate characteristics of a fuel injection valve. <P>SOLUTION: The EGR control system is equipped with an EGR control valve 52 interposed in an exhaust recirculating pipe 51 and an electric control device 60. The electric control device 60 determines a target EGR rate, a target air flow rate, an actual EGR rate and an actual air flow rate, on the basis of an operating condition amount of the internal combustion engine. The ratio of the target EGR rate to the target air flow rate is determined as a target converted EGR rate, and the ratio of the actual EGR rate to the actual air flow rate is determined as an actual converted EGR rate. Then, the opening of the EGR control valve 52 is controlled so that the target converted EGR rate equals to the actual converted EGR rate. Since the actual converted EGR rate is in proportion to the intake oxygen concentration and the actual converted EGR rate and the target converted EGR rate can be calculated regardless of a requested injection amount, the intended intake oxygen concentration can be obtained regardless of the flow rate characteristics of the fuel injection valve. <P>COPYRIGHT: (C)2004,JPO |
