Patent ID: 6491004
Filing Date: 2002-12-10
Classification: F02B,F02F

Abstract:
A two-stroke engine including a two-stroke engine in a portable handheld work apparatus, the two-stroke engine comprising: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: a carburetor for supplying an air/fuel mixture and said carburetor having an intake channel; an inlet channel connected to said intake channel and leading to said crankcase so as to permit the entire quantity of said air/fuel mixture to be drawn by suction via said crankcase; said cylinder having a discharge outlet formed therein for conducting exhaust gases away from said combustion chamber; an outlet-near transfer channel connecting said crankcase to said combustion chamber; said outlet-near transfer channel having a first end defining a transfer window opening into said combustion chamber and a second end defining an inflow opening open to said crankcase; an air channel opening into said transfer channel at approximately the elevation of said transfer window thereof for supplying an essentially fuel-free gas flow to said transfer channel; an outlet-remote transfer channel connecting said crankcase to said combustion chamber; said outlet-remote transfer channel having a first end defining a transfer window opening into said combustion chamber and a second end defining an inflow opening open to said crankcase; a sum of the constructive volumes of said outlet-near transfer channel between said transfer window and said inflow opening being approximately 20% to 60% of the volumetric total air input of said engine at rated engine speed so that approximately 30% to 70% of the volumetric total air input of said engine to said combustion chamber at said rated engine speed is supplied via said outlet-near transfer channel and a stratified charge formed in said combustion chamber is maintained via said outlet-near transfer channel over a time of approximately 65% to 95% of the scavenging operation.