Patent ID: 6941906
Filing Date: 2005-09-13
Classification: F02B,F02M

Abstract:
1. A crankcase scavenged internal combustion engine ( 1 ) of two-stroke type, primarily intended for a handheld working tool, such as a chain saw, a trimmer or a power cutter, with a cylinder ( 2 ) and a piston ( 4 ) reciprocating along the cylinder wall ( 3 ), which piston separates a combustion chamber ( 5 ) above it and a crankcase volume ( 6 ) below it, and in the cylinder wall ( 3 ) there are ports ( 7 , 8 , 9 , 10 , 10 ′) for air inlet ( 11 ), exhaust outlet ( 12 ) and for a number of scavenging ducts ( 13 , 13 ′), which connect the combustion chamber with the crankcase, characterized in that at least one auxiliary duct ( 14 ) is arranged with an auxiliary port ( 15 ) in the cylinder wall, which auxiliary port ( 15 ) is opened and closed by the piston, and in that the inlet is divided into: a fuel inlet ( 16 ) leading to a fuel port ( 7 ), and an air inlet ( 17 ) leading to an air port ( 8 ), and in that these ports are opened and closed by the piston ( 4 ), which also comprises a transfers space ( 18 ), which mouth edges are limited by the piston periphery and which, in at least one piston position, creates a connection between the fuel port ( 7 ) and the auxiliary port ( 15 ), so that fuel can be supplied to the auxiliary duct via the auxiliary port ( 15 ), and then, after the port ( 15 ) later on has been opened by the piston ( 4 ), can flow into the combustion chamber.