| 摘要 |
PURPOSE:To enhance the efficiency of cooling an exhaust valve, thereby reducing the required amount of air passed through a cylinder and enhance the efficiency of recovering heat from an exhaust gas, by a method wherein the closing timing of an exhaust valve is advanced and the valve is momentarily maintained at a low opening, in a Diesel engine. CONSTITUTION:The exhaust valve 21 is driven by an exhaust valve driving mechanism consisting of a rocker arm 23, a pushing rod 23, a roller 24 and a driving cam 25. In the case of a 4-stroke-cycle engine, the profile of the cam 25 is so set that closing of the exhaust valve 21 is started before the opening 2 of a suction vavle reaches 100% opening, and a low opening A is thereafter maintained at least until the bottom dead center is reached. The timing of 100% closing is appropriately set in accordance with the thermal efficiency of the engine and the valve-cooling effect after the valve 21 is maintained at the low opening A. Curve 1' represents the opening characteristic of a conventional exhaust valve. |
