Two-cycle internal combustion engine

Abstract

A two-cycle internal combustion engine which is capable of inhibiting air-fuel mixture from being mixed with the air introduced in advance into the combustion actuating chamber during the scavenging period, thereby realizing a complete lamellar scavenging. This engine is constructed such that one or more pairs of Schnürle type scavenging passageways ( ), each allowing the combustion actuating chamber ( ) disposed above a piston ( ) placed in a cylinder ( ) to be communicated with the crank chamber ( ), are symmetrically provided on both sides of a longitudinal section (F—F) which imaginatively divides an exhaust port ( ) into two equal parts, thereby enabling air (A) to be introduced into the scavenging passageways ( ) and also enabling an air-fuel mixture (M) 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 (A) to be introduced via the scavenging passageway into the combustion actuating chamber ( ) prior to the introduction of air-fuel mixture (M) 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 ( ).