Patent ID: 8312713

Claim:
An internal combustion engine comprising: a combustion chamber including an exhaust port; an exhaust valve arranged to open and close the exhaust port; and an exhaust device including: an exhaust path arranged to guide exhaust gas discharged from the combustion chamber via the exhaust port; 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 a branch section arranged to branch a shock wave generated by the exhaust gas discharged from the combustion chamber, propagating in a downstream direction in the exhaust path at a higher velocity than the exhaust gas that generated the shock wave flowing into the exhaust path from the combustion chamber when the exhaust valve is opened, from a portion of the exhaust path which is upstream with respect to the divergent section, and to propagate the branched shock wave back to the exhaust path; wherein the divergent section is connected to the combustion chamber provided upstream with respect to the divergent section; the exhaust gas flowing into the exhaust path from the combustion chamber is caused to pass the convergent section and to collide against the shock wave generated by the exhaust gas which has propagated in the branch section, between the branch 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 a negative pressure is generated upstream with respect to the divergent section in the exhaust path by the generated new shock wave.