Patent ID: 6513466
Filing Date: 2003-02-04
Classification: F02B,F02M,Y02T

Abstract:
A method for operating a two-stroke engine including an engine in a portable handheld work apparatus, the two-stroke engine including: a cylinder having a cylinder wall; a piston mounted in said cylinder to undergo a reciprocating movement along a stroke path between top dead center and bottom dead center during operation of said engine; said cylinder and said piston conjointly delimiting a combustion chamber; a crankcase connected to said cylinder; a crankshaft rotatably mounted in said crankcase; a connecting rod connecting said piston to said crankshaft to permit said piston to drive said crankshaft as said piston reciprocates in said cylinder; an outlet for conducting exhaust gases away from said combustion chamber; a transfer channel connecting said crankcase to said combustion chamber; said transfer channel having a first end defining a transfer window lying in said cylinder wall and opening into said combustion chamber; said transfer channel having a second end defining an inflow opening; a mixture-preparation unit for supplying an air/fuel mixture; an inlet in said crankcase downstream of said mixture-preparation unit for conducting said air/fuel mixture into said crankcase; an air channel for supplying an essentially fuel-free gas flow to said crankcase; a storage space in said crankcase; said air channel communicating with said crankcase through said storage space; and, a valve mounted in said crankcase so as to be movable between a first position wherein said inflow opening of said transfer channel is connected directly to said crankcase and a second position wherein said inflow opening is connected indirectly to said crankcase via said storage space; the method comprising the steps of:storing air in said transfer channel toward the end of a scavenging cycle; at the start of the next scavenging cycle, pushing the stored air as advance air into said combustion chamber with a fresh mixture flowing out from said crankcase; and, said transfer window being opened to said crankcase close to top dead center and said storage space being closed with respect to said crankcase.