Patent ID: 8336303

Claim:
A multi-cylinder internal combustion engine comprising: a plurality of combustion chambers including a plurality of exhaust ports, each of the plurality of combustion chambers including at least one of the plurality of exhaust ports; a plurality of exhaust valves each arranged to open or close a respective one of the plurality of exhaust ports, each of the plurality of exhaust ports including an opening period in which the respective exhaust port is open; and an exhaust path arranged to guide exhaust gas discharged from each of the combustion chambers via the exhaust port; wherein the exhaust path includes: a convergent section including a flow path cross-sectional area that is smaller at a downstream end thereof than at an upstream end thereof; a divergent section provided downstream with respect to the convergent section and including a flow path cross-sectional area that is larger at a downstream end thereof than at an upstream end thereof; and an exhaust merging section provided upstream with respect to the divergent section and arranged to connect the plurality of combustion chambers, and only the exhaust ports of different combustion chambers that include opening periods of that do not overlap are connected to each other upstream of the divergent section; the exhaust merging section is arranged such that a shock wave, propagating in the exhaust merging section at a higher velocity than the exhaust gas flowing into the exhaust merging section when one of the plurality of exhaust ports connected by the exhaust merging section is opened, is reflected by the exhaust valve closing another one of the plurality of exhaust ports; the exhaust gas flowing into the exhaust path from the combustion chamber is caused to pass the convergent section and to collide against the reflected shock wave, between an upstream end of the exhaust merging section and the divergent section, so as to increase the pressure of the exhaust gas in the convergent section; and the exhaust gas is caused to pass the divergent section to generate a new shock wave and thus to generate a negative pressure in a portion of the exhaust path which is upstream with respect to the divergent section by the generated new shock wave.