| 摘要 |
FIELD: engines and pumps.SUBSTANCE: outlet channel of the engine in the order of inlet side is provided with hydrocarbon supply valve (16), oxidation (13) catalyst and cleaning catalyst (14) of exhaust gas. In compliance with the engine working mode, there selectively applied is the first NOcleaning method, in which air-fuel ratio of exhaust gas flowing to exhaust gas cleaning catalyst (14) is reduced at a certain interval at maintaining its poor level so that NOcan be removed without forced NOaccumulation in the form of nitrates, and the second NOcleaning method, in which composition of air-fuel mixture of exhaust gas flowing to exhaust gas cleaning catalyst (14) is switched over from poor to rich at the interval exceeding the above period so that NOcan be removed.EFFECT: providing high NOcleaning speed at high temperature of exhaust gas cleaning catalyst.18 cl, 22 dwg |
