Patent ID: 9726070
Date: 2017-08-08
CPC Classifications: F02B,F02F,F02M

Claim:
1. A stratified scavenging two-stroke engine including one of a cylinder member in which a cylinder housing a piston is formed and a crankcase joined with the cylinder member, or the cylinder member and a crankcase-forming member forming a part of the crankcase joined with the cylinder member, the engine comprising: an intake passage formed in the cylinder member and that is configured to supply a gaseous mixture of fuel and air to an inside of the crankcase; an exhaust passage formed in the cylinder member and that is configured to discharge combustion gas in the cylinder; a first scavenging passage including a cylinder member-side passage and a crankcase-side passage, and that extends from a first scavenging intake that opens to the inside of the crankcase to a first scavenging port that opens to an inside of the cylinder according to movement of the position of the piston; a second scavenging passage including a cylinder member-side passage and a crankcase-side passage, and that extends from a second scavenging intake that opens to the inside of the crankcase to a second scavenging port that opens to the inside of the cylinder according to movement of the position of the piston; a communicating portion through which the cylinder member-side passage of the first scavenging passage and the cylinder member-side passage of the second scavenging passage communicate with each other; and an air passage formed in the cylinder member and connected to the first scavenging passage, but not connected to the second scavenging passage, the air passage being configured to supply air for pre-scavenging into the cylinder member-side passage of the first scavenging passage via a check valve that opens during an upward stroke of the piston, wherein the cylinder member-side passage and the crankcase-side passage of the first scavenging passage communicate with each other and the cylinder member-side passage and the crankcase-side passage of the second scavenging passage communicate with each other, via an interposed member provided in a joining portion between one of the cylinder member and the crankcase or between the cylinder member and the crankcase-forming member, and the interposed member has a first opening through which the cylinder member-side passage and the crankcase-side passage of the first scavenging passage communicate with each other, a second opening through which the cylinder member-side passage and the crankcase-side passage of the second scavenging passage communicate with each other, and an upper surface constituting a part of the air passage.