| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve exhaust emission control performance at a cold-start of an internal combustion engine having an exhaust gas purification catalyst. SOLUTION: An in-cylinder temperature increase is achieved by securing in-cylinder remaining gas through operating a direct injection internal combustion engine by minus overlap where an intake valve is opened after an exhaust valve is closed under catalyst-inactive condition. When the in-cylinder temperature reaches a level at which oxidization of additional fuel is possible, an air- fuel ratio of the engine is shifted to one leaner than a stoichiometric one. Then additional fuel is injected after an expansion stroke. Accordingly, the additional fuel can be fully oxidized in the cylinder, thus increasing an exhaust gas temperature reliably, and the undesirable condition where the additional fuel still unburnt is discharged from the cylinder can be prevented reliably.</p> |
