Abstract: The invention is directed to an ignition circuit for a two-stroke engine in a portable handheld work apparatus. A spark plug (2) is connected via a switch (14) to a voltage source (16). The ignition switch (14) is actuated by an electronic control circuit (15) which closes the ignition switch (14) in dependence upon the crankshaft angle and additional operating parameters such as the rpm of the engine (1) in order to trigger an ignition spark per revolution of the crankshaft (10). To limit rpm, the ignition switch (14) is held open when a pregiven end rpm is exceeded in order to suppress an ignition spark over at least one crankshaft revolution.

Abstract: A method of limiting the maximum speed of a two-cycle engine in a manually-guided implement such as a hedge trimmer is provided. Via a unit for controlling the ignition time point in a crankshaft angular range prior to the upper dead center position of a reciprocating piston, the ignition is interfered with above an operational speed to keep the speed below the maximum speed. To ensure a rapid onset of the speed regulation along with good exhaust gas values, in the range between the operational speed and the maximum speed, the ignition time point is shifted in the direction toward the upper dead center position of the piston in such a way that in the vicinity of the maximum speed, the ignition time point is close to the upper dead center position of the piston and the engine output is reduced to a prescribed value that corresponds approximately to the frictional horsepower for the driving of the tool.

Abstract: A carburetor for an internal combustion engine includes an intake channel section (2) as well as a throttle element journalled in the intake channel section (2). The throttle element is adjustable between a full-load position (25) and an idle position (26). A pump (20, 30) is provided for additional fuel metering and this pump includes a pumping chamber (24, 34) and a pump piston (21, 31) guided in the pumping chamber (24, 34). The position of the pump piston (21, 31) is coupled to the position of the throttle element. To ensure an optimal supply of the internal combustion engine with fuel in each operating state, the pump piston (21, 31) is so coupled to the throttle element that fuel is pumped from the pumping chamber (24, 34) into the intake channel section (2) when there is a displacement of the throttle element from the full throttle position (25) into the idle position (26).

Abstract: The invention is directed to an ignition circuit for a two-stroke engine in a portable handheld work apparatus. A spark plug (2) is connected via a switch (14) to a voltage source (16). The ignition switch (14) is actuated by an electronic control circuit (15) which closes the ignition switch (14) in dependence upon the crankshaft angle and additional operating parameters such as the rpm of the engine (1) in order to trigger an ignition spark per revolution of the crankshaft (10). To limit rpm, the ignition switch (14) is held open when a pregiven end rpm is exceeded in order to suppress an ignition spark over at least one crankshaft revolution.

Abstract: A two-stroke engine is provided for a manually-guided implement. Formed in a cylinder is a combustion chamber that is delimited by a reciprocating piston that drives a crankshaft via a connecting rod. An outlet is provided for withdrawing exhaust gases out of the combustion chamber, and an inlet is provided for supplying fresh mixture to the combustion chamber. The inlet forms one end of a storage channel, the other end of which opens out via a window controlled by the piston into the crankcase. Via a fuel-supplying mixture channel, the storage channel is connected with a fuel supply. Combustion air is supplied to the crankcase via a crankcase inlet, with the combustion air being conveyed into the combustion chamber via a transfer channel and a transfer window. The storage channel is connected to the mixture channel via a connecting channel that is controlled by the piston.

Abstract: An intake device having an intake channel that includes an intake channel section is provided. A butterfly valve is pivotably mounted in the intake channel section. A dividing wall is disposed downstream of the butterfly valve and divides the intake channel section into an air duct and a mixture duct. The air duct has a flow cross-section that is greater than the flow cross-section of the mixture duct. A fuel jet opens into the mixture duct.

Abstract: A two-stroke engine in a hand-held working tool such as a motor chainsaw has a combustion chamber delimited by a piston which drives a crankshaft. An outlet for removing exhaust gases from the combustion chamber and an intake for supplying fresh mixture to the combustion chamber are provided. A storage duct opens into the intake and the crankcase and is connected with a carburetor. Combustion air flows via a crankcase intake and a transfer passage into the combustion chamber. For providing good power development with good exhaust emission values under all operating conditions, the flow cross-section of the mixture-forming channel leading to the storage duct is smaller by more than one half than the flow cross-section of the intake passage leading to the crankcase intake. During idle, the fuel required for operation is supplied substantially exclusively via the mixture-forming channel leading to the storage duct.

Abstract: The invention is directed to a method for operating a two-stroke engine in a portable handheld work apparatus. The engine includes a cylinder (12) and a combustion chamber (26) which is delimited by a reciprocating piston (14). The combustion chamber includes an outlet (28) discharging exhaust gases and an inlet (30) of a storage channel (34). The inlet (30) lies approximately opposite the outlet (28) and the other end of storage channel (34) opens via a controlled end (38) into the crankcase (18). Between its ends, the storage channel (34) is connected to a first fuel metering device (20) of a first fuel path; whereas, the crankcase (18) has a crankcase inlet (24) which is connected to a second fuel metering device (19) of a second fuel path. In the case of an acceleration, additional fuel is metered to one or both fuel paths via an acceleration unit (22).

Abstract: A two-stroke engine is provided for a manually-guided implement. Formed in a cylinder is a combustion chamber that is delimited by a reciprocating piston that drives a crankshaft via a connecting rod. An outlet is provided for withdrawing exhaust gases out of the combustion chamber, and an inlet is provided for supplying fresh mixture to the combustion chamber. The inlet forms one end of a storage channel, the other end of which opens out via a window controlled by the piston into the crankcase. Via a fuel-supplying mixture channel, the storage channel is connected with a fuel supply. Combustion air is supplied to the crankcase via a crankcase inlet, with the combustion air being conveyed into the combustion chamber via a transfer channel and a transfer window. The storage channel is connected to the mixture channel via a connecting channel that is controlled by the piston.

Abstract: A two-stroke engine in a hand-held working tool such as a motor chainsaw has a combustion chamber delimited by a piston which drives a crankshaft. An outlet for removing exhaust gases from the combustion chamber and an intake for supplying fresh mixture to the combustion chamber are provided. A storage duct opens into the intake and the crankcase and is connected with a carburetor. Combustion air flows via a crankcase intake and a transfer passage into the combustion chamber. For providing good power development with good exhaust emission values under all operating conditions, the flow cross-section of the mixture-forming channel leading to the storage duct is smaller by more than one half than the flow cross-section of the intake passage leading to the crankcase intake. During idle, the fuel required for operation is supplied substantially exclusively via the mixture-forming channel leading to the storage duct.

Abstract: The invention is directed to a method for operating a two-stroke engine in a portable handheld work apparatus. The engine includes a cylinder (12) and a combustion chamber (26) which is delimited by a reciprocating piston (14). The combustion chamber includes an outlet (28) discharging exhaust gases and an inlet (30) of a storage channel (34). The inlet (30) lies approximately opposite the outlet (28) and the other end of storage channel (34) opens via a controlled end (38) into the crankcase (18). Between its ends, the storage channel (34) is connected to a first fuel metering device (20) of a first fuel path; whereas, the crankcase (18) has a crankcase inlet (24) which is connected to a second fuel metering device (19) of a second fuel path. In the case of an acceleration, additional fuel is metered to one or both fuel paths via an acceleration unit (22).