Patent ID: 8359836

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