| 摘要 |
PURPOSE:To improve intake and exhaust efficiency by providing a secondary exhaust valve in the downstream of a main exhaust valve, and making the downstream of the main exhaust valve and the upstream of the main intake valve continuous to each other. CONSTITUTION:A secondary exhaust valve 3 is provided in the downstream of a main exhaust valve 11 and a secondary intake valve 2 in the upstream of a main intake valve 1. An exhaust passage between the main exhaust valve 11 and the secondary exhaust valve 3 is made continuous to an intake passage between the main intake valve 1 and the secondary intake valve 2 via a communication passage 7. At the time of an exhaust stroke start, the main exhaust valve 11 and the secondary exhaust valve 3 open concurrently and when the exhaust stroke has completed, only the secondary exhaust valve 3 closes. The main intake valve 1 and the secondary intake valve 2 open concurrently when an intake stroke has started. Air through the main intake valve 1 purges the main exhaust valve 11 of exhaust gases stagnating in a combustion chamber and causes the main exhaust valve 11 and then the secondary intake valve 2 to close respectively, thereby completing the intake stroke.
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