| 摘要 |
<p>[Problem] To configure an internal combustion engine provided with an exhaust gas discharge port (6) for each cylinder (2), the internal combustion engine being configured so that the activation of a catalyst disposed in the exhaust gas discharge system can be promoted during low-speed operation of the engine and so that the overheating of the catalyst can be prevented or suppressed during high-speed operation of the engine. [Solution] The upstream sections (6a, 6b) of an exhaust gas discharge port (6) are exhaust gas conduits provided to each cylinder (2) so as to extend from the cylinder (2) in the direction tilted relative to the axis (Y) of the cylinder (2). The downstream section (6c) of the exhaust gas discharge port (6) is an exhaust gas conduit which is located downstream of the upstream sections (6a, 6b) in the direction of flow of exhaust gas and with which the upstream sections (6a, 6b) are joined. Ridges sections (7, 8) extending in the direction of flow of the exhaust gas are provided on the inner peripheral surfaces of the upstream sections (6a, 6b) and of the downstream section (6c). The surface area (S1) of upstream regions of the ridge sections (7, 8), the upstream regions being located in the upstream sections (6a, 6b), is set to be greater than the surface area (S2) of a downstream region located in the downstream section (6c).</p> |
