| 摘要 |
An internal combustion engine is disclosed having first (14) and second (16) intake poppet valves, an exhaust poppet valve (18,20), and valve actuators (not shown) for opening and closing the intake and exhaust valves in synchronism with the rotation of the engine crankshaft. The valve actuators can be operated in two ways to enable the engine to operate in a four stroke or in a two stroke mode. To improve scavenging when the engine is operating in two stroke mode, the intake port (24) associated with the first intake valve (16) is designed to induce swirl in the intake charge, means (28) are provided for disabling the flow in the port (26) associated with the second intake valve (16) during two-stroke operation, and the direction of the swirl induced by the intake port (24) of the first intake valve (14) is such that the intake charge flows past the second intake valve (16) before reaching an exhaust valve (18,20). |
