Andreas Stihl Ag & Co.

Lars Bergmann

Heiko Rosskamp

Michael Raffenberg

Peter Linsbauer

Axel Klimmek

Reinhard Gerhardy

Jochen Kramer

Igor Klaric

Peter Pretzsch

The invention relates to a two-stroke engine for a portable handheld work apparatus such as a motor-driven chain saw, cutoff machine, brushcutter or the like. A crankcase ( ) is formed below the engine cylinder ( ). A piston ( ) moves up and down in the cylinder ( ) and drives a crankshaft ( ) rotatably journalled in the crankcase ( ). A fuel-containing mixture is supplied via a membrane carburetor ( ) to the combustion chamber ( ) delimited between the piston ( ) and the cylinder ( ). A bypass channel ( ) is provided parallel thereto and supplies essentially fuel-free air to the combustion chamber ( ). The bypass channel ( ) opens into a channel segment ( ) via a connecting piece ( ) fixedly attached to the cylinder ( ). The channel segment ( ) is formed in the cylinder wall ( ). A spark plug ( ) and an ignition control device ( ) are assigned to the combustion chamber ( ). The ignition control device ( ) is fixedly mounted with a portion to the cylinder ( ) via one attachment point ( ) and is fixedly mounted to the connecting piece ( ) via another attachment point ( ).

Two-stroke engine

A cylinder is produced of die cast metal and is for a two-stroke engine in a portable handheld work apparatus such as a motor chain saw. A combustion chamber ( ) is formed in the cylinder ( ) and this combustion chamber is delimited by a piston ( ). In the cylinder wall ( ), there is an outlet ( ) for conducting away the combustion gases from the combustion chamber ( ). Transfer channels ( ) are provided which open into the combustion chamber ( ) via transfer windows ( ) and supply the operating medium from the crankcase ( ) needed for operating the two-stroke engine. The transfer channels ( ) are configured in the cylinder wall ( ) as channels opening radially to the outside and are closed by a seated cover ( ).

Die cast metal cylinder assembly 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 ( ).

The invention relates to a two-stroke engine in a portable handheld work apparatus. A combustion chamber ( ) is formed in a cylinder ( ) and the chamber is delimited by a piston ( ). At least one transfer channel ( ) is provided which connects the crankcase ( ) to the combustion chamber ( ). An air channel ( ) opens into the transfer channel ( ) and this channel supplies essentially fuel-free gas, preferably air. The intake channel ( ) of a carburetor ( ) is connected to an intake opening ( ) in the housing base ( ) of the air filter housing ( ) upstream of a carburetor throttle flap. The intake channel ( ) connects downstream of the carburetor throttle flap to an intake channel ( ) to the crankcase ( ). To provide an ignition-ready mixture in order to start and run up the engine, it is provided that the air channel ( ) is connected to a bypass opening ( ) in the housing base ( ) of the air filter ( ) and a common pivotable choke element ( ) is assigned to the intake opening ( ) as well as the bypass opening ( ). The choke element ( ) clears the openings ( ) in the operating position and closes the passthrough cross section of the bypass opening ( ) in the start position whereas the passthrough cross section of the intake opening ( ) is reduced to a start cross section.

Internal combustion engine having a choke flap arranged in an air filter housing

The invention relates to a two-stroke engine for a portable handheld work apparatus such as a motor chain saw. The combustion chamber ( ), which is configured in a cylinder ( ), is delimited by a piston ( ) which drives a crankshaft ( ) rotatably journalled in a crankcase ( ). The crankcase ( ) is connected to the combustion chamber ( ) via a transfer channel ( ). A first end ( ) of the transfer channel ( ) opens into the combustion chamber ( ) via an entry window ( ) lying in the cylinder wall ( ); whereas, the second end ( ) of this transfer channel ( ) is open toward the crankcase ( ). The transfer channel ( ) is connected between its ends ( ) to an air channel ( a, b) via a check valve ( ). The air channel ( a, b) supplies essentially fuel-free gas via a throttle ( ) having an adjustable throttle element ( ). A mixture-preparation device ( ) is provided for the air/fuel mixture downstream of an air filter ( ) in the flow direction of the combustion air. The air/fuel mixture is supplied via an inlet ( ) to the crankcase ( ). In order to meter clean air to the air channels in a controlled manner, an adjustable throttle element ( ) is mounted in a throttle channel ( ) of an independent throttle housing ( ) and the throttle channel ( ) is connected upstream of the throttle element to the clean space ( ) of the air filter ( ) connected ahead of the mixture-preparation device ( ).

Two-stroke engine having a bypass branching from an air filter housing

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

The invention relates to a two-stroke engine having a combustion chamber (,) configured in a cylinder (,). The combustion chamber is delimited by a piston (,) which moves upwardly and downwardly. The crankcase (,) is connected to the combustion chamber (,) via an transfer channel (,). A first end (,) of the transfer channel (,) opens into the combustion chamber (,) via an entry window (,) lying in the cylinder wall (,) and controlled by piston the (,). Between its ends (,), the transfer channel (,) is connected to a gas channel (,) via a valve (,). The gas channel (,) essentially supplies fuel-free gas. The air/fuel mixture, which is necessary for the operation of the two-stroke engine, is supplied to the crankcase (,) via an inlet (,). In order to ensure a full charge of the transfer channel (,) with fuel-free gas, the entry window (,) of the transfer channel (,) is held open to the crankcase (,) in a stroke position of the piston (,) in the region of top dead center. The maximum cross section then corresponds only to a portion of the area of the entry window (,).

Growing community of inventors

Welzheim, Germany

Lars Bergmann