EXHAUST EMISSION CONTROL DEVICE FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To prevent deterioration of black smoke and excessive temperature increase of a catalyst at a high speed and high load when lowering an engine λ in executing rich spike for reduction of a catalyst.

SOLUTION: The device is equipped with a catalyst 42 which occludes NOx in the exhaust gas flowing into an exhaust passage 40 and reduces NOx when the air-fuel ratio in the exhaust gas drops, a fuel injection valve 23 for directly injecting fuel to a cylinder internal combustion chamber of a diesel engine 20, an exhaust light oil adding injector 41 capable of injecting light oil in the exhaust passage 40, and a control part 100 for controlling combustion of the diesel engine 20 so as to reduce the air-fuel ratio in the exhaust passage 40. The control part 100 controls an operation of a fuel injection valve 23 so as to make the timing of the post injection up to 20 degree crank angle after a top dead center in the high speed and high load range while separately injecting fuel by the main injection in the vicinity of the top dead center in a compression stroke of a cylinder and the post injection in the expansion stroke after the main injection.

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