Patent ID: 7520253
Filing Date: 2009-04-21
Classification: F02B

Abstract:
1. A two-stroke internal combustion engine configured to introduce fuel-free air into a combustion chamber together with an air-fuel mixture pre-compressed in a crank chamber in a scavenging stroke, comprising: a cylinder bore in which a piston is fitted to reciprocally move and define the combustion chamber therein; an exhaust port formed in the cylinder bore to be opened and closed by the piston; first scavenging ports formed in the cylinder bore to be opened and closed by the piston; and second scavenging ports formed in the cylinder bore to be opened and closed by the piston, the second scavenging ports being remoter from the exhaust port than the first scavenging ports, the first and second scavenging ports being oriented in a direction of an elevation angle, and the angle of elevation of each second scavenging port being larger than the angle of elevation of each first scavenging port, wherein, in the scavenging stroke, the second scavenging ports are opened earlier than the first scavenging ports to introduce fuel-free air therefrom into the combustion chamber, and the first scavenging ports are opened later to next introduce an air-fuel mixture pre-compressed in the crank chamber into the combustion chamber.