Andreas Stihl Ag Co. Kg

Michael Harrer

Claus Naegele

Heinrich Leufen

Eberhard Schieber

Ernst Gorenflo

Andreas Neubauer

Andreas Paa

A portable, handheld work apparatus such as a chain saw has a handle () to guide the work apparatus () and has an air-cooled, mixture-lubricated combustion engine () arranged in a casing as a drive for a work tool (). The cylinder () has a combustion chamber () formed therein to which an air/fuel mixture is supplied. The air/fuel mixture is ignited by a spark plug () which projects into the combustion chamber (). An ignition control () triggers a spark in dependence on the angular position of the crankshaft (). A temperature sensor () is provided to control the cylinder temperature. The temperature signal of the temperature sensor () is connected to a power control (). When a predetermined temperature is exceeded, the power control () changes the operating parameters of the combustion engine () in such a manner that the power of the combustion engine () is changed.

Handheld work apparatus having an air-cooled combustion engine

A two-stroke engine () has a cylinder () defining a combustion chamber () delimited by a piston (). The piston () drives a crankshaft () which is rotatably journalled in a crankcase (). The crankcase () is connected to the combustion chamber () via a transfer channel () at at least one position of the piston. The two-stroke engine has an inlet () into the crankcase () and an outlet () from the combustion chamber. There is an arrangement to supply fuel, a control, and a device to determine the crankcase pressure (p). A method to operate the two-stroke engine () includes determining the crankcase pressure (p) during every engine cycle. The fluctuation in the crankcase pressure (p) is determined and the fluctuation is compared to a limit value (&#x394;p) to determine whether a combustion occurs during every engine cycle. In this way, a determination can be reliably made as to whether the two-stroke engine is running in a four-stroke mode.

Method for operating a two-stroke engine

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Stuttgart, Germany

Michael Harrer