Spark ignition type two cycle internal combustion engine

TL;DR: In this paper, the downstream of a throttle valve on a suction pipe is divided into the first suction system (A) for supplying new air over a total operating range and the second system (B) for providing only air in an operating range in which a load is heavier than a prescribed one, and thereby making it possible to supply a relatively rich mixture without diffusion near an ignition plug.

Abstract: PURPOSE:To improve a combustion performance by providing a pair of scavenging ports opening into a combustion chamber at mutually opposite positions and a scavenging port opening into the combustion chamber at a position opposite to an exhaust port, and thereby making it possible to supply a relatively rich mixture without diffusion near an ignition plug. CONSTITUTION:The downstream of a throttle valve 26 on a suction pipe 11 is divided into the first suction system (A) for supplying new air over a total operating range and the second suction system (B) for supplying only air in an operating range in which a load is heavier than a prescribed one. The first suction system (A) is constituted to supply the air drawn into a crank case 8 by the reciprocating motion of a piston 4 through a long and narrow scavenging passage 30 into a combustion chamber 6, and to inject light oil or gasoline through the first and the second fuel injector 25a, 25b in the course of the scavenging passage 30 as occasion calls. The scavenging passage 30 is divided into two parts on its downstream, and the one part of them is connected to a pair of the first scavenging ports 32 opening into the combustion chamber 6 at mutually opposite positions, and the other part of them is connected to the second scavenging port 33 opening into a combustion chamber 5 at a position opposite to an exhaust port 18.