To warm up a catalyst converter very quickly even at the time of engine start when an engine is cold so as to improve exhaust emission when the engine is cold by setting valve opening time to early time and arranging the catalyst converter in a first exhaust passage in which a flow rate of exhaust gas is large in a low rotation region of the engine.
In a series 4 cylinder diesel engine A, valve opening time of a first exhaust valve 7 opening and closing a first exhaust passage 15 in which a turbine 16 is arranged for a combustion chamber is set to earlier time than valve opening time of a second exhaust valve 8 opening and closing a second exhaust passage 18 in which the turbine 16 is not arranged for the combustion chamber. Lean NOx catalyst 17 capable of reducing and purifying NOx in exhaust air even when an air-fuel ratio is in a lean state is arranged in the first exhaust passage 1, and an upstream end of an exhaust air reflux passage 22 refluxing a part of exhaust gas on an air suction side is branched and connected with the first exhaust passage 15. Consequently, it is possible to increase torque in a low rotation region, improve the scavenging property in a high rotation region, and increase the exhaust air purifying property when the engine is cold.
| WO/2021/083965 | ENGINE WITH LOW PARTICULATE EMISSIONS |
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UCHIDA HIROYASU
MASUDA TOSHIHARU
ARAKI KEIJI
