Abstract: A two-stroke engine has a cylinder with a combustion chamber delimited by a reciprocating piston, wherein the piston drives in rotation a crankshaft, and wherein a spark plug projects into the combustion chamber and ignites a fuel/air mixture. The two-stroke engine further has devices for supplying fuel and combustion air to the combustion chamber and a control unit that determines the ignition timing based on an ignition map. The ignition map indicates the ignition timing as a function of the engine speed for at least one first and one second operating states and for at least one first and one second engine speed ranges. The engine is controlled in that for an engine cycle the ignition timing is set in the second operating state at least within the first engine speed range based on the engine speed and on the number of engine cycles since the last combustion.

Abstract: An internal combustion engine includes a cylinder (2) wherein a combustion chamber (5) is formed. The engine also includes devices for metering fuel and combustion air as well as an ignition device for igniting the mixture in the combustion chamber (5). A method for operating the internal combustion engine provides that fuel and combustion air are supplied to the engine and the mixture is ignited in the combustion chamber (5). The combustion chamber (5) is delimited by a piston (7) which drives a crankshaft (25) rotatably journalled in a crankcase (3). A control is provided which controls the supply of fuel and the ignition of the mixture in the combustion chamber (5). The internal combustion engine is so controlled in at least one operating state that the number of combustions is less than the number of engine cycles in the same time span. To avoid the formation of self ignitions, the operating state is a high rpm range wherein the rpm lies above the rated rpm and below the rpm in a regulating range.

Abstract: A carburetor (1, 51) has an intake channel (2) wherein a throttle element and a choke element are arranged with the choke element being upstream of the throttle element. The choke element is displaceable between an operating position (8) and at least one starting position (9). A first fuel path is provided which supplies fuel to the intake channel section (2) in dependence upon the underpressure present therein. A first controllable valve (20) for controlling the supplied fuel quantity is mounted in the first fuel path. In order to achieve an adapted fuel supply in different operating states, a second fuel path is provided which defines a bypass line to the first valve (20). A second valve (44, 54) is mounted in the second fuel path. A method for operating the carburetor (1, 51) provides that the second valve (44, 54) is actuated in dependence upon at least one operating parameter of the carburetor (1, 51).

Abstract: A carburetor (1, 51) has an intake channel (2) wherein a throttle element and a choke element are arranged with the choke element being upstream of the throttle element. The choke element is displaceable between an operating position (8) and at least one starting position (9). A first fuel path is provided which supplies fuel to the intake channel section (2) in dependence upon the underpressure present therein. A first controllable valve (20) for controlling the supplied fuel quantity is mounted in the first fuel path. In order to achieve an adapted fuel supply in different operating states, a second fuel path is provided which defines a bypass line to the first valve (20). A second valve (44, 54) is mounted in the second fuel path. A method for operating the carburetor (1, 51) provides that the second valve (44, 54) is actuated in dependence upon at least one operating parameter of the carburetor (1, 51).

Abstract: A two-stroke engine has a cylinder with a combustion chamber delimited by a reciprocating piston, wherein the piston drives in rotation a crankshaft, and wherein a spark plug projects into the combustion chamber and ignites a fuel/air mixture. The two-stroke engine further has devices for supplying fuel and combustion air to the combustion chamber and a control unit that determines the ignition timing based on an ignition map. The ignition map indicates the ignition timing as a function of the engine speed for at least one first and one second operating states and for at least one first and one second engine speed ranges. The engine is controlled in that for an engine cycle the ignition timing is set in the second operating state at least within the first engine speed range based on the engine speed and on the number of engine cycles since the last combustion.

Abstract: A two-stroke engine has a cylinder and a piston reciprocating in the cylinder and delimiting a combustion chamber. The piston has at least one piston recess. A crankshaft is rotatably arranged in a crankcase connected to the cylinder. A connecting rod connects piston and crankshaft. Transfer channels connect the crankcase to the combustion chamber in pre-defined piston positions. The transfer channels each have a transfer port opening into the combustion chamber. A device for supplying fuel and an air channel supplying combustion air are provided. In predetermined piston positions, the air channel is connected by the piston recess to the transfer ports. The air channel opens into the cylinder bore opposite the exhaust for the exhaust gases. The air channel, the piston recess, and the transfer channels define an air passage that provides approximately uniform distribution of air from the air channel into the transfer channels.

Abstract: A piston for a two-cycle engine having a piston head and a piston wall in which are disposed wrist pin eyes. At least one undercut is formed between the underside of the piston head and the wrist pin eyes at a distance from the piston head. The undercut extends from the interior of the piston toward the piston wall. A respective thickened portion is provided in at least one region of the piston that is rotationally shifted about the longitudinal axis of the piston by 90° relative to one of the wrist pin eyes. The thickened portion is disposed at a distance below the piston head and extends into the interior of the piston.

Abstract: An internal combustion engine includes a cylinder (2) wherein a combustion chamber (5) is formed. The engine also includes devices for metering fuel and combustion air as well as an ignition device for igniting the mixture in the combustion chamber (5). A method for operating the internal combustion engine provides that fuel and combustion air are supplied to the engine and the mixture is ignited in the combustion chamber (5). The combustion chamber (5) is delimited by a piston (7) which drives a crankshaft (25) rotatably journalled in a crankcase (3). A control is provided which controls the supply of fuel and the ignition of the mixture in the combustion chamber (5). The internal combustion engine is so controlled in at least one operating state that the number of combustions is less than the number of engine cycles in the same time span. To avoid the formation of self ignitions, the operating state is a high rpm range wherein the rpm lies above the rated rpm and below the rpm in a regulating range.

Abstract: A two-stroke engine has a cylinder and a piston reciprocating in the cylinder and delimiting a combustion chamber. The piston has at least one piston recess. A crankshaft is rotatably arranged in a crankcase connected to the cylinder. A connecting rod connects piston and crankshaft. Transfer channels connect the crankcase to the combustion chamber in pre-defined piston positions. The transfer channels each have a transfer port opening into the combustion chamber. A device for supplying fuel and an air channel supplying combustion air are provided. In predetermined piston positions, the air channel is connected by the piston recess to the transfer ports. The air channel opens into the cylinder bore opposite the exhaust for the exhaust gases. The air channel, the piston recess, and the transfer channels define an air passage that provides approximately uniform distribution of air from the air channel into the transfer channels.

Abstract: A piston for a two-cycle engine having a piston head and a piston wall in which are disposed wrist pin eyes. At least one undercut is formed between the underside of the piston head and the wrist pin eyes at a distance from the piston head. The undercut extends from the interior of the piston toward the piston wall. A respective thickened portion is provided in at least one region of the piston that is rotationally shifted about the longitudinal axis of the piston by 90° relative to one of the wrist pin eyes. The thickened portion is disposed at a distance below the piston head and extends into the interior of the piston.

Abstract: A two-stroke engine (1) has a combustion chamber (3) disposed in a cylinder (2). The combustion chamber (3) is delimited by a reciprocating piston (5). The piston (5) drives a crankshaft (7) via a connecting rod (6) and the crankshaft (7) is rotatably journalled in a crankcase (4). The two-stroke engine (1) has an intake channel (8) for the supply of fuel into the crankcase (4), an outlet (13) for exhaust gases from the combustion chamber (3) and an air channel (10) for the supply of substantially fuel-free air. A throttle element (18) is mounted in the air channel (10). At pregiven positions of the piston (5), the crankcase (4) is connected via at least one transfer channel (14) to the combustion chamber (3).

Abstract: A two-stroke engine (1) has a combustion chamber (3) disposed in a cylinder (2). The combustion chamber (3) is delimited by a reciprocating piston (5). The piston (5) drives a crankshaft (7) via a connecting rod (6) and the crankshaft (7) is rotatably journalled in a crankcase (4). The two-stroke engine (1) has an intake channel (8) for the supply of fuel into the crankcase (4), an outlet (13) for exhaust gases from the combustion chamber (3) and an air channel (10) for the supply of substantially fuel-free air. A throttle element (18) is mounted in the air channel (10). At pregiven positions of the piston (5), the crankcase (4) is connected via at least one transfer channel (14) to the combustion chamber (3).

Abstract: An intake system for preparing combustion air (1) is for an internal combustion engine of a portable handheld work apparatus. The intake system includes: a carburetor (2); an air filter (3) which is connected upstream of the carburetor (2); and, a filter case (4) which closes the air filter (3) from the outside. A combustion air channel (5) leads from a take-up opening (6) in a cooling air fan (7) of the engine to an inlet opening (24) in the filter case (4). The filter case (4) includes at least one defined ventilation opening (8) for connecting an inner space (9) of the filter case (4) to the ambient air. The flow cross section of the ventilation opening (8) is so designed that the airflows through the inlet opening (24), the intake opening (18) of the carburetor (2) and the ventilation opening (8) are compensated at the rated rpm of the engine and that a uniform pressure level adjusts in the inner space (9) of the filter case (4).

Abstract: A method is provided for producing a cylinder in a two-cycle engine. The cylinder bore is first machined as a preparation for the provision of a coating. The thereby resulting window edges that surround an inlet window are then at least partially chamfered. The cylinder bore is consequently provided with the coating, which at least partially overlaps the chamfered window edge. There thereby results in the region of the window edge a location of least spacing relative to the axis of the transfer channel. The piston liner or gliding surface is finally machined to a finished dimension such that in the region of the chamfered and coated window edge or corner there is formed a coating edge having a wall spacing relative to the location of least spacing, which such wall spacing having a maximum value of 0.7 mm.

Abstract: The invention relates to a carburetor arrangement for an internal combustion engine (1) which drives a work apparatus. The engine (1) has an intake channel (3) leading through a carburetor (2). The intake channel (3) includes an intake opening (4) on the side of the carburetor (2) facing away from the engine (1). A baffle wall (5) is provided and covers the intake opening (4) at least partially. The baffle wall (5) is mounted transversely to the longitudinal axis (6) of the intake channel (3) at a spacing to the intake opening (4). The baffle wall (5) and the intake opening (4) define a baffle enclosure (7) disposed therebetween. At least a first component part (8) of the baffle wall (5) is inclined with respect to the longitudinal axis (6) of the intake channel (3) in such a manner that fuel droplets (9), which exit from the intake channel (3) and which impinge on the first component part (8) of the baffle wall (5), form a fuel film (10).

Abstract: An intake system for preparing combustion air (1) is for an internal combustion engine of a portable handheld work apparatus. The intake system includes: a carburetor (2); an air filter (3), which is connected upstream of the carburetor (2); and, a filter case (4) which closes the air filter (3) from the outside. A combustion air channel (5) leads from a take-up opening (6) in a cooling air fan (7) of the engine to an inlet opening (24) in the filter case (4). The filter case (4) includes at least one defined ventilation opening (8) for connecting an inner space (9) of the filter case (4) to the ambient air. The flow cross section of the ventilation opening (8) is so designed that the air flows through the inlet opening (24), the intake opening (18) of the carburetor (2) and the ventilation opening (8) are compensated at the rated rpm of the engine and that a uniform pressure level adjusts in the inner space (9) of the filter case (4).

Abstract: The invention relates to a carburetor arrangement for an internal combustion engine (1) which drives a work apparatus. The engine (1) has an intake channel (3) leading through a carburetor (2). The intake channel (3) includes an intake opening (4) on the side of the carburetor (2) facing away from the engine (1). A baffle wall (5) is provided and covers the intake opening (4) at least partially. The baffle wall (5) is mounted transversely to the longitudinal axis (6) of the intake channel (3) at a spacing to the intake opening (4). The baffle wall (5) and the intake opening (4) define a baffle enclosure (7) disposed therebetween. At least a first component part (8) of the baffle wall (5) is inclined with respect to the longitudinal axis (6) of the intake channel (3) in such a manner that fuel droplets (9), which exit from the intake channel (3) and which impinge on the first component part (8) of the baffle wall (5), form a fuel film (10).

Abstract: A method is provided for producing a cylinder in a two-cycle engine. The cylinder bore is first machined as a preparation for the provision of a coating. The thereby resulting window edges that surround an inlet window are then at least partially chamfered. The cylinder bore is consequently provided with the coating, which at least partially overlaps the chamfered window edge. There thereby results in the region of the window edge a location of least spacing relative to the axis of the transfer channel. The piston liner or gliding surface is finally machined to a finished dimension such that in the region of the chamfered and coated window edge or corner there is formed a coating edge having a wall spacing relative to the location of least spacing, which such wall spacing having a maximum value of 0.7 mm.

Abstract: The invention relates to the combination of an air filter and a membrane carburetor (1). The membrane carburetor (1) has an intake channel section (3) configured in the carburetor housing (2) into which the fuel-conducting channels (4, 4′) open which are fed from a control chamber (5) of the carburetor housing (2). The control chamber (5) is separated by a control membrane (6) from the compensation chamber (7). A compensation channel (11) leads from the compensation chamber (7) into a flow space (9). A connecting piece (8) is led into the flow space (9) as a connection of the intake channel section (3) of the membrane carburetor (1) with the flow space (9). The compensation channel (11) and the connecting piece (8) open into the housing (21) on the clean air side (23). The housing (21) forms the flow space (9).

Abstract: The invention relates to the combination of an air filter and a membrane carburetor (1). The membrane carburetor (1) has an intake channel section (3) configured in the carburetor housing (2) into which the fuel-conducting channels (4, 4′) open which are fed from a control chamber (5) of the carburetor housing (2). The control chamber (5) is separated by a control membrane (6) from the compensation chamber (7). A compensation channel (11) leads from the compensation chamber (7) into a flow space (9). A connecting piece (8) is led into the flow space (9) as a connection of the intake channel section (3) of the membrane carburetor (1) with the flow space (9). The compensation channel (11) and the connecting piece (8) open into the housing (21) on the clean air side (23). The housing (21) forms the flow space (9).