Four stroke engine charged by crankcase pressure - has inlet valve regulating transfer channel inlet

摘要

The four stroke engine uses a crankcase pressure as a pre-compressor for the fuel air mixture. The crankcase is designed as small as possible so that the volume is considerably less at piston bottom dead centre than that of the cylinder swept volume. The engine has a fuel/air mixture transfer pipe (33) which starts at a transfer port in the cylinder wall and terminates at an opening on the cylinder head. The opening is regulated in the conventional four stroke manner. The piston has an opening (26) just below the crown, opposite the transfer port (32) at piston bottom dead centre. The transfer pipe (33) volume is equal to the cylinder swept volume and acts as a mixture storage chamber. The fuel/air mixture is drawn into the crankcase via an intake pipe (31) and an inlet port (29). The inlet port is in the cylinder wall just below the lower piston skirt edge when the piston is at top dead centre.