| 摘要 |
PURPOSE:To make the fitting structure of an exhaust valve simple and small whose exhaust timing is variable by a method wherein a valve piece whose rotary edge is formed to be positioned along the upper edge of an exhaust port is provided rotatably in the position near the exhaust port. CONSTITUTION:The captioned exhaust valve device 20 is constituted by a valve rotary axis 21 supported axially in the upper part of an exhaust passage 5 near an exhaust port 4 and by a valve piece 22 fixed to the axis 21. The rotary axis 21, rotated in synchronization with the speed of an engine, has a small-diameter part 21a and a large-diameter part 21b supported axially by axial orifices 1a and 1b bored near the exhaust port 4 from the laternal side of a cylinder block 1, while in the large-diameter part 21b being provided a notch part 21c forming a part of the inner surface of the exhaust passage 5. The valve pipece 22 is formed with a curved surface so that the rotary edge 22a thereof is positioned along the upper edge of the exhaust port 4, while both side edges 22b thereof are formed also with a curved surface lying closing along the surface of the inside wall of the exhaust passage 5. |
