Two stroke internal combustion engine - has membrane in crankcase to keep fuel charge separate from lubricating oil

摘要

The engine has a crankcase (3) with a membrane (2) in a vertical plane running alongside the crankshaft (5). As the piston rises the membrane is pulled back by the suction in the crankcase and draws a charge in. On the downward stroke the membrane is pushed out and compresses the charge which enters the cylinder as soon the transfer port is uncovered by the piston. The suction and transfer ports have a common passage which contains a non return valve (1) in the suction inlet. The membrane separates the charge from oil (10) in the sump and thus reduces pollution in the exhaust.