| 摘要 |
PURPOSE:To provide free degrees on the operation of an admission valve and make scavinging efficiency more favorable in such a way that the valve body of the admission valve is formed by being integrally combined with a differential pressure piston, in an engine which scavenges residual exhaust air in the cylinder by a piston pump. CONSTITUTION:When a pre-pump 601 closes a suction port 23, and it comes into its compression stroke, admission pressure P1 in an admission port 701 climbs, and when an exhaust port 27 is opened, inner pressure P2 gets suddenly near to the atmospheric pressure. Therefore, the admission pressure P1 is enlarged, force-F1 in the valve opening direction which is produced from the pressure difference according to P1-P2 is applied to a valve body 16, and force-F2 in the valve opening direction which is produced from the pressure difference according to P1-Po applied thereto. In consequence, when component of force-F1 and -F2 grows larger than force F in the valve closing direction of a valve spring 19, an admission valve 151 is operated in the valve opening direction. After the exhaust port 27 has been opened, when the admission port 701 is opened, new mixed air is fed under pressure through the admission port 701 into a cylinder 501, and the mixed air pushes out residual exhaust gas to the side of the exhaust port 27 and scavenges it. In the meantime, the cylinder 501 and the port 701 are interrupted. |
