| 摘要 |
PURPOSE:To form intake/scavenging ports without gnawing a piston, by piercing a communication passage between a space section and a crank chamber through a cylinder block in the vertical direction. CONSTITUTION:Upon compression stroke during which a piston 6 moves upward, the pressure in a crank chamber 7 is made negative so that a reed valve 36 opens to introduce a mixture into the crank chamber 7 through an intake port 41. Due to the ignition of a spark plug 9, the mixture in a cylinder chamber 2 is burnt to move the piston 6 downward so that the pressure of the mixture introduced into the crank chamber 7 is raised. As a result, the reed valve 36 returns to its original position by its resiliency to close an intake-air passage 34, and when the top surface of the piston 6 initiates to meet the upper edges of main scavenging ports 14, 15 and counter-scavenging port 42, the mixture is fed to the upper section of the cylinder chamber 2 through the main scanvenging ports 14, 15 and the counter-scavenging port 42 to replace the burnt gas which is then discharged through an exhaust port 12. |
