| 摘要 |
PROBLEM TO BE SOLVED: To effectively display exhaust emission control capacity by appropriately controlling OSC (O<SB>2</SB>Storage Capacity) states of each catalyst according to an operation condition of an internal combustion engine. SOLUTION: An internal combustion engine is provided with a plurality of cylinder groups (banks) like a V-type internal combustion engine. A first catalyst is provided on each individual exhaust gas passage, and the individual exhaust gas passages merge to construct a common exhaust gas passage at downstream thereof. A second catalyst is provided on the common exhaust gas passage. When control of the internal combustion engine is changed over from separate control for each cylinder group to stoichiometric control, an air fuel ratio control part sets the cylinder group which is set rich during separate control for each cylinder, namely a rich combustion cylinder group, lean for a predetermined period of time, and sets the cylinder group which is set lean during separate control for each cylinder, namely a lean combustion cylinder group, rich for the predetermined period of time. Consequently, OSC of the first catalyst corresponding to each cylinder group shifts to a neutral condition where the catalyst can display emission control capacity at the maximum (for example, a condition where OSC is about 50%). COPYRIGHT: (C)2009,JPO&INPIT |
