| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To perform a reducing processing by efficiently releasing NOx and SOx trapped in a catalyst while satisfactorily maintaining the operability of an engine. <P>SOLUTION: When a combustion is changed from a stratified combustion (lean combustion) to a stoichiometric or rich combustion, to perform the reducing processing by releasing the NOx trapped in the NOx trap catalyst, a target air/fuel ratio is steppingly increased, and gradually decreased. To rich the air/ fuel ratio, first fuel is injected by a limit amount not causing a torque variation by only a main injection in an intake stroke, and then an auxiliary injection in an expansion stroke for injecting by an amount short of a requirement for NOx processing is started in combination with the main injection after oxygen accumulated in an exhaust pipe is sufficiently consumed by a main injection rich control and the density of the oxygen is lowered. <P>COPYRIGHT: (C)2003,JPO</p> |
