| 摘要 |
PURPOSE: To reduce an emission amount of NOx, HC, and Co by a method wherein an air pulse valve to feed air is arranged at an exhaust gas manifold and opened according to the negative pressure pulse of the exhaust manifold, in a small displacement internal combustion engine for a lawn mower. CONSTITUTION: The intake manifold 24 of a small engine 22 is provided with a float chamber carburetor 30 and an exhaust gas circulation valve 32 and meanwhile, and an exhaust manifold 26 is provided with an air pulse 34 for air intake operated in coordination with an exhaust gas device 32. When the engine 22 is run on a sufficient load, a part of exhaust gas is returned to the downstream side of an intake manifold 24 through an exhaust gas circulation valve 32 to reduce emission of NOx. Further, to reduce emission of HC and CO, air in the atmosphere is emitted in a flow of hot exhaust gas by the air pulse operation valve 34, and the air pulse operation valve 34 is controlled for opening and closing through a diaphragm according to a boost pressure introduced through a conduit 394. |
