| 摘要 |
PURPOSE:To suppress release of NOx toward the atomsphere by arranging an NOx absorbent which absorbs NOx when an air-fuel ratio of exhaust gas is lean and releases NOx when an oxygen density is decreased, making the air-fuel ratio be rich while releasing NOx when a load is low other than a rich operation area, and reducing it. CONSTITUTION:An exhaust port 8 of an engine main body 1 is connected to a casing 19 which houses an NOx absorbent 18 through an exhaust pipe 17. In the NOx absorber 18, for instance, potassium is held by a carrier such as alumina. The absorbent 18 absorbs NOx when an air-fuel ratio in a combustion chamber 3 is lean. When an oxygen density is decreased, namely lean degree of exhaust gas is decreased, the absorbent 18 releases NOx. Rich and lean conditions of the air-fuel ratio is controlled based on operation conditions through a correction factor K of a fuel injection time by means of an electronic control unit 30. After the air-fuel ratio gets rich, the rich degree is gradually decreased and a theoretical air-fuel ratio is kept. The absorbent 18 gradually releases NOx and reduction is sequentially performed, to suppress release of NOx to atmosphere. |
