Two-state internal combustion engine

Claim 1

A two-stroke internal combustion engine, especially for handheld portable tools such as a motor-driven chain saw, the two-stroke internal combustion engine comprising: a cylinder defining a cylinder wall; a piston defining a longitudinal axis and being mounted in said cylinder for reciprocating therein between bottom and top dead center positions; said piston having an essentially flat rotationally symmetrical upper end face; said end face and said cylinder conjointly defining a combustion chamber; said cylinder wall defining an inner wall surface and having an exhaust opening formed in said surface; said cylinder wall having an exhaust channel extending from said exhaust opening for conducting hot combustion gases entering said exhaust opening away from said combustion chamber; said end face of said piston having a first half surface area directly adjacent said exhaust opening and a second half surface area disposed away from said exhaust opening; an injection valve mounted in said cylinder wall opposite said exhaust opening and being adapted to discharge an injection jet directed at least substantially toward said second half surface area; said injection jet defining a jet axis; said jet axis and said longitudinal axis of said piston conjointly defining an angle of less than 90°; a crankcase; said cylinder wall having an inlet channel formed therein for conducting combustion air into said crankcase as said piston moves toward said top dead center position; said cylinder wall having an overflow channel formed therein communicating with said crankcase for conducting said combustion air from said crankcase to said combustion chamber when said piston moves downwardly toward said bottom dead center; said overflow channel having an overflow opening formed in said inner wall surface for passing said combustion air from said overflow channel into said combustion chamber; said overflow opening being disposed between said injection valve and said exhaust opening; means for directing said combustion air through said overflow opening and into said combustion chamber in a direction which is approximately opposite to the direction of said injection jet; said inner wall surface having an injection opening formed therein through which said injection jet passes into said combustion chamber; said injection opening being at an elevation above the elevation of at least one of said exhaust opening and said overflow opening by a predetermined amount (b) so as to cause said injection opening to be closed last after closure of said at least one of said exhaust opening and said overflow opening during the movement of said piston toward top dead center thereby permitting the duration of the injection of said injection jet to continue after the closure of said at least one of said exhaust opening and said overflow opening.