| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To perform a rich spike at the fuel injection pressure optimum for the rich spike. <P>SOLUTION: An NO<SB>X</SB>catalyst is arranged in an exhaust passage of an internal combustion engine in which an air-fuel ratio of mixture to be burnt in a combustion chamber is maintained to be lean. The NO<SB>X</SB>catalyst stores NO<SB>X</SB>in the flowing-in exhaust gas when the air-fuel ratio of the flowing-in exhaust gas is lean, and reduces the stored NO<SB>X</SB>if a reducing agent is contained in the exhaust gas when the air-fuel ratio of the flowing-in exhaust gas lowers, so that the amount of the stored NO<SB>X</SB>is decreased. In order to decrease the amount of NO<SB>X</SB>stored in the NO<SB>X</SB>catalyst by reducing NO<SB>X</SB>stored in the NO<SB>X</SB>catalyst, when main injection is stopped during engine decelerating operation, the rich spike is performed to temporarily change an average air-fuel ratio AFE of the exhaust gas flowing into the NO<SB>X</SB>catalyst to be rich by injecting fuel from a fuel injection valve. Fuel injection pressure PF of the fuel injection valve is controlled so that fuel injection pressure PR at the time of the rich spike is higher than fuel injection pressure PM at the time of the main injection. <P>COPYRIGHT: (C)2004,JPO</p> |
