| abstract |
(57) [Summary] [Purpose] Exhaust gas purification that adsorbs nitrogen oxides in the exhaust gas during lean combustion operation and reduces the adsorbed nitrogen oxides during rich combustion operation to maintain the adsorption capacity of nitrogen oxides. In an internal combustion engine equipped with a catalyst (NOx catalyst), substances other than nitrogen oxides (NOx) adhering to the exhaust purification catalyst that reduce the purifying ability are reliably removed, and the function of the exhaust purification catalyst is maintained well. [Structure] The exhaust passage includes a first exhaust passage (14a, 14b), a second exhaust passage (30a, 30b) shorter than the first exhaust passage, and valve means (31a, 31b) for opening and closing the second exhaust passage. ) And an adhesion amount estimating means for estimating the adhesion amount of the substance having a reduced purification capacity to the exhaust purification catalyst (13a, 13b), and when the adhesion amount reaches a predetermined value, the second exhaust passage is provided by the valve means. And a catalyst temperature raising means for raising the temperature of the exhaust purification catalyst by supplying exhaust gas having a temperature higher than that of the first exhaust passage to the exhaust purification catalyst via the second exhaust passage. |