Two-cycle internal combustion engine

A two-cycle internal combustion engine which is constructed such that one or more pairs of schnürle type scavenging passageways, each allowing a combustion actuating chamber disposed above a piston placed in a cylinder to be communicated with a crank chamber, are symmetrically provided on both sides of a longitudinal section which imaginatively divides an exhaust port into two equal parts, thereby enabling air to be introduced into the scavenging passageways and also enabling air-fuel mixture to be introduced into the crank chamber;

• and that in the descending stroke of the piston the exhaust port is opened at first, and then, the scavenging port which is disposed at a downstream end of the scavenging passageway is opened, thereby enabling air to be introduced via the scavenging passageway into the combustion actuating chamber prior to the introduction of air-fuel mixture into the combustion actuating chamber;
• said internal combustion engine being characterized in that said one or more pairs of schnürle type scavenging passageways are respectively provided, near the end portion thereof located close to the crank chamber, with a throttled portion, wherein the volume of said scavenging passageways is set to such that it is equal to or slightly smaller than the quantity of air to be introduced in advance.

A two-cycle internal combustion engine which is constructed such that one or more pairs of schnürle type scavenging passageways, each allowing a combustion actuating chamber disposed above a piston placed in a cylinder to be communicated with a crank chamber, are symmetrically provided on both sides of a longitudinal section which imaginatively divides an exhaust port into two equal parts, thereby enabling air to be introduced into the scavenging passageways and also enabling air-fuel mixture to be introduced into the crank chamber;

• and that in the descending stroke of the piston the exhaust port is opened at first, and then, the scavenging port which is disposed at a downstream end of the scavenging passageway is opened, thereby enabling air to be introduced via the scavenging passageway into the combustion actuating chamber prior to the introduction of air-fuel mixture into the combustion actuating chamber;
• said internal combustion engine being characterized in that said one or more pairs of schnürle type scavenging passageways are respectively provided, near the end portion thereof located close to the crank chamber, with a throttled portion, wherein an effective cross-sectional passage area of the throttled portion is set to such that a required quantity of air-fuel mixture can be fed to the combustion actuating chamber following the introduction of air thereto.