Andreas Stihl Ag & Co.

Andreas Stihl Ag Co. Kg

Axel Klimmek

Werner Geyer

Heiko Rosskamp

Andreas Bähner

Hans Nickel

Lars Bergmann

Peter Pretzsch

Harald Schliemann

Helmut Zimmermann

Georg Maier

Thomas Stark

Florian Hoche

Peter Linsbauer

Bernhard D&uuml;rr

Tommy Roitsch

Ralf Tuckermann

Michael Joos

J&ouml;rg Schlossarczyk

Hans Holderle

Andreas Lingen

Olaf Schmidt

Roland Schmidt

Fritz Kiesewetter

Matthias Hehnke

Silke Kaminski

Joachim Baumhauer

Gunter Stein

Ralf Blechsmidt

Edgar Bignion

Matthias Mugele

Jan Tribulowski

Peter St&uuml;cke

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.

Two-stroke engine

An exhaust-gas muffler includes a muffler housing () having an inlet opening () and an outlet (). The exhaust-gas muffler is especially for the internal combustion engine in a portable handheld work apparatus. At least one attenuating space (&#x2033;) is configured in the exhaust-gas muffler (). The exhaust-gas muffler () includes at least one resonance pipe () to increase power and to reduce the hydrocarbon emissions. The resonance pipe () is fluidly connected to the inlet opening () and the resonance pipe leads to a backflow of exhaust gases into the combustion chamber (). For a simple manufacture, it is provided that the exhaust-gas muffler () includes lower and upper half shells () via which the resonance pipe () is at least partially delimited.

Exhaust-gas muffler

A two-stroke engine () has a combustion chamber () disposed in a cylinder (). The combustion chamber () is delimited by a reciprocating piston (). The piston () drives a crankshaft () via a connecting rod () and the crankshaft () is rotatably journalled in a crankcase (). The two-stroke engine () has an intake channel () for the supply of fuel into the crankcase (), an outlet () for exhaust gases from the combustion chamber () and an air channel () for the supply of substantially fuel-free air. A throttle element () is mounted in the air channel (). At pregiven positions of the piston (), the crankcase () is connected via at least one transfer channel () to the combustion chamber (). In order to prevent air from being drawn by suction into the air channel because of leakages during idle or at low rpm, a fluid connection is provided between the air channel () downstream of the throttle element () and the crankcase () for underpressure compensation which connection is present at least partially for a position of the piston from 90&#xb0; ahead of bottom dead center to 90&#xb0; after bottom dead center. A connection between the crankcase () and the intake channel () can be provided in lieu of, or in addition to, the connection to the air channel ().

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

Intake system

The invention relates to a two-cycle engine for a drive engine in a portable, manually operated tool. The combustion chamber formed in a cylinder is delimited by a piston that moves up and down, whereby the piston, by means of a connecting rod, drives a crankshaft rotatably mounted in a crankcase. The combustion chamber has an outlet for removing waste gases, and provided for supplying a fuel/air mixture prepared by a mixture preparation device, and combustion air, are gas-supplying channels that open into the combustion chamber. In order to reduce scavenging losses, it is provided that for the entire duration of the gas exchange exclusively air flows in the area near the outlet and exclusively fuel/air mixture flows out of the crankcase in the area further away from the outlet.

Two-cycle engine with a stratified charge

The invention relates to a two-stroke engine in the form of a drive motor in a motor-driven chain saw or like portable handheld work apparatus. A combustion chamber ( ) is provided in a cylinder ( ) of the engine and is delimited by a piston ( ). The piston ( ) drives a crankshaft ( ) via a connecting rod ( ) and the crankshaft ( ) includes a crankweb ( ). The combustion chamber ( ) is connected via an outlet to an exhaust-gas muffler. A fresh mixture is supplied to the combustion chamber ( ) from the crankcase ( ) via a transfer channel ( ). The entry of the fresh mixture takes place via the crankcase ( ). Also, an air channel ( ) is provided for supplying fuel-free air. To reduce the scavenging losses, the air channel ( ) is connected via a storage space ( ) to the crankcase ( ). The transfer channel ( ) is either connected directly via a valve ( ) to the crankcase or indirectly via the storage space ( ).

An exhaust gas control mechanism for a two-stroke engine is provided. A first housing chamber is in communication with a discharge window of the cylinder of the engine, while a second housing chamber has the exhaust gases flowing therethrough into an exhaust gas outlet. A flow communication establishes a controlled communication of flow of exhaust gas from the first chamber to the second chamber. A valve is provided for controlling the flow communication, wherein such valve, if initially open, closes upon partial opening of the discharge window and after a given period of time again opens.

Exhaust gas control mechanism for a two-stroke engine

A two-stroke engine for a portable two-stroke engine in a portable handheld work apparatus includes a combustion chamber ( ) formed in a cylinder ( ). The combustion chamber ( ) is delimited by the piston ( ) which drives the crankshaft ( ) via a connecting rod ( ). The two-stroke engine includes several transfer channels ( ), which, referred to a symmetry plane ( ), lie on opposite sides ( ) with the plane partitioning approximately the outlet ( ). The transfer channels ( ) connect the crankcase ( ) to the combustion chamber ( ). A first end ( ) of each transfer channel ( ) opens via an entry window ( ) into the combustion chamber ( ) and the second end ( ) of each transfer channel opens to the crankcase ( ). Each transfer channel ( ) is connected, between its ends ( ), to an air channel ( ) via a membrane valve ( ). Air is supplied by the air channel ( ) via an adjustable throttle ( ).

A hand-held working tool has a housing and an internal combustion engine arranged in the housing and comprising a crankshaft and an air filter. A tool is driven by the crankshaft of the internal combustion engine. A fan housing is attached to the engine housing and has an air inlet. A fan wheel is arranged in the fan housing and is driven by the crankshaft of the internal combustion engine to supply cooling air, sucked in through the air inlet, to the internal combustion engine. The fan housing has a bottom extending radially to the crankshaft. The bottom and a side of the fan wheel facing the bottom define a chamber in the fan housing. The bottom has a combustion air outlet. A combustion air channel is connected to the combustion air outlet and to the air filter. The combustion air outlet is axially supplying combustion air from the chamber through the combustion air channel into the air filter of internal combustion engine. The fan housing has a channel wall having a bottom portion connected to the face of the bottom remote from the fan wheel and covering the bottom partially to form a double-walled bottom. The end face portion of the combustion air channel is defined by the bottom and the bottom portion of the channel wall. In an alternative embodiment the combustion air channel is provided in a hollow beam of a support that supports the drive unit of the working tool.

Hand-held working tool

The invention relates to a two-stroke engine which operates as a drive motor in a portable work apparatus such as a motor-driven chain saw. The two-stroke engine has a combustion chamber (,) which is formed in a cylinder (,) and is delimited by a piston (,) which moves up and down in the cylinder. The piston drives via a connecting rod (,) a crankshaft (,) which rotates in a crankcase (,). The crankcase (,) is connected to the combustion chamber (,) via a transfer channel (,). A first end (,) of the transfer channel (,) opens via an entry window (,) into the combustion chamber (,) and the second end (,) of the transfer channel (,) opens into the crankcase (,). The entry window (,) lies in the cylinder wall (,) and is controlled by the piston (,). The transfer channel (,) is connected to a gas channel (,) between its ends (,). An essentially fuel-free gas flow (,) flows via a check valve (,) from the gas channel (,) and flows into the transfer channel (,). The mixture, which is necessary for operating the two-stroke engine (,), is drawn from a membrane carburetor (,) into the crankcase (,) via an inlet (,). The flow element (,) is mounted in the flow path of the gas flow (,) which exits from the gas channel (,) into the transfer channel (,). A flow element fans out the gas flow (,). In this way, a complete scavenging of the transfer channel is ensured during the induction stroke.

Two-stroke engine having an air scavenged transfer channel

A two-stroke internal combustion engine for a hand-guided working tool has a cylinder with a cylinder wall and a piston reciprocating in the cylinder and defining a combustion chamber with the cylinder wall. Transfer parts, each having an outlet window, for introducing combustion air and fuel into the combustion chamber are provided. The outlet windows are cut into the cylinder wall for connecting the transfer parts to the combustion chamber. The outlet windows have limiting edges extending parallel to a central cylinder axis of the cylinder and are located within an inner mantle surface of the cylinder wall. The outlet windows have a window width measured in a circumferential direction of the inner mantle surface. The transfer parts have a channel width measured in the circumferential direction of the inner mantle surface, whereby the window width is greater than the channel width. The transfer parts have a transition portion into the outlet windows. The transfer parts have a flow stall edge at an end of the transition portion remote from the outlet windows. The flow stall edges extend parallel to the central cylinder axis.

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Schwaikheim, Germany

Axel Klimmek