A laminar-scavenging two-cycle engine which has a high laminar-scavenging effect, includes a scavenging passage having a crankcase side portion extending along a crankcase, and a cylinder side portion extending along a cylinder and having a length larger than the sum of the diameter and stroke of the cylinder. An ambient air introducing passage for introducing leading air into the scavenging passage is connected to an intermediate portion of the scavenging passage. A notch for opening a scavenging port to the side of the crankcase when a piston is near the top dead center is formed in the piston.

A laminar-scavenging two-cycle engine which has a high laminar-scavenging effect, includes a scavenging passage having a crankcase side portion extending along a crankcase, and a cylinder side portion extending along a cylinder and having a length larger than the sum of the diameter and stroke of the cylinder. An ambient air introducing passage for introducing leading air into the scavenging passage is connected to an intermediate portion of the scavenging passage. A notch for opening a scavenging port to the side of the crankcase when a piston is near the top dead center is formed in the piston.

To meet stringent emission standards and improve performance of two-stroke crankcase-scavenged engines, the muffler (13) of the engine is provided with mixing means (130, 31) for mixing the exhaust gases (42) resulting from the mixture participating in combustion and gases resulting from scavenging, so that a substantially homogenous gaseous mixture is formed within the muffler (13), and means (81) for sensing oxygen concentration is located in the homogeneous gaseous mixture and are configured to provide an output value to a control unit (80) for controlling supply of fuel to the engine and thereby the air-fuel ratio in the combustion chamber (41). The muffler (13) suitably is provided with a catalytic element (140), preferably a three-way catalyst. The engine (1) preferably is a stratified charge engine.

A two-stroke engine piston (1) is disclosed comprising a piston top (3), a mantle surface (5), a stratified scavenging channel (7) in the mantle surface (5), and a weight reduction space (9) arranged between the piston top (3) and the stratified scavenging channel (7). The weight reduction space (9) has a largest first axial extent (a1) at the mantle surface (5) and a second axial extent (a2) radially inside the mantle surface (5), and wherein the second axial extent (a2) is greater than the largest first axial extent (a1). The present disclosure further relates to an engine (30), a hand-held tool (40), and a method of manufacturing an engine piston (1).

A two-stroke engine piston (1) is disclosed comprising a piston top (3), a mantle surface (5), a stratified scavenging channel (7) in the mantle surface (5), and a weight reduction space (9) arranged between the piston top (3) and the stratified scavenging channel (7). The weight reduction space (9) has a largest first axial extent (a1) at the mantle surface (5) and a second axial extent (a2) radially inside the mantle surface (5), and wherein the second axial extent (a2) is greater than the largest first axial extent (a1). The present disclosure further relates to an engine (30), a hand-held tool (40), and a method of manufacturing an engine piston (1).

A fuel supply device has a base body, in which an intake channel section is formed. At least one adjustable throttle element for controlling the free flow cross section of the intake channel section is provided. At least one fuel opening opens into the intake channel section. A partition wall section is arranged in the intake channel section upstream of the throttle element. The partition wall section and the throttle element divide, in a completely open position of the throttle element, the intake channel section upstream of the throttle element into a mixture channel, into which the fuel opening feeds fuel, and an air channel. In order to improve the cooling of the fuel supply device, the partition wall section has at least one element for increasing the surface area within the mixture channel.

A carburetor has a carburetor body wherein an intake channel is formed. A throttle flap is pivotably mounted by a throttle shaft in the carburetor body for controlling the free flow cross-section of the intake channel. The intake channel has a first longitudinal center axis in the region of the throttle shaft. The throttle flap has first and second end positions, wherein the throttle flap opens a larger flow cross-section of the intake channel in the second end position than in the first end position. A partition wall section, on which the throttle flap lies in the second end position, is arranged upstream of the throttle shaft. A choke flap is upstream of the partition wall section and is pivotable between first and second end positions. In their second end positions, the throttle flap and the choke flap overlap in the direction of the first longitudinal center axis.

An improved rotary type carburetor for a stratified scavenging engine designed to enable the easy adjustment of air and fuel flow at the time of initial configuration is disclosed. The improved rotary carburetor includes an air intake passage and an air-fuel mixture passage formed in a horizontal direction on a carburetor main body. The throttle valve of the improved rotary carburetor can be fitted into a cylindrical-throttle-valve hole formed orthogonal to a fuel and an air passage of the carburetor main body. The throttle valve has the air supply side valve hole formed on the air intake passage side and a fuel supply side valve hole formed on the air-fuel mixture passage side.

A fuel feed unit has a base body with an intake channel section, into which a fuel opening opens. A partition wall section divides the intake channel section into a mixture channel and an air channel. The wall section has a recess in which the throttle flap at least partially lies in an end position. The wall section has, upstream of the recess, a continuous surface facing the mixture channel and which has lateral sections adjacent to the channel wall and a middle section running between the lateral sections. The lateral sections have, upstream of the throttle flap, a separation edge for the flow. In the end position, the side of the throttle flap facing the mixture channel defines a reference plane which divides the unit into a first region and a second region. The lateral sections extend, at least directly upstream of the recess, into the second region.

A fuel feed unit has a base body with an intake channel section, into which a fuel opening opens. A partition wall section divides the intake channel section into a mixture channel and an air channel. The wall section has a recess in which the throttle flap at least partially lies in an end position. The wall section has, upstream of the recess, a continuous surface facing the mixture channel and which has lateral sections adjacent to the channel wall and a middle section running between the lateral sections. The lateral sections have, upstream of the throttle flap, a separation edge for the flow. In the end position, the side of the throttle flap facing the mixture channel defines a reference plane which divides the unit into a first region and a second region. The lateral sections extend, at least directly upstream of the recess, into the second region.