The disclosure provides a two-cycle engine and an engine work machine. When a piston is located on the side of a bottom dead center, at a part corresponding to a notch part in the piston, an inner surface of the crank case protrudes toward an interior side to form a crank case first protruding part penetrating through the notch part toward the interior side. Meanwhile, the crank case at a part corresponding to a part without the notch part in the piston is not in a shape protruding toward the interior side. By assembling the piston and the crank case in such shapes, the piston is able to reciprocally move up and down without interfering with the crank case. In this case, by disposing the crank case first protruding part, the volume in the crank case is able to be reduced.

A piston crown for a combustion system is disclosed. The piston crown includes a piston bowl having a circumferential recess and a plurality of first recesses arranged spaced apart from each other along a circumferential direction. The circumferential recess is disposed proximate to a circumference of the piston crown. Each recess of the plurality of the first recesses extends between a center of the piston crown and the circumferential recess, and a width and a depth of each recess of the plurality of first recesses are extended along a radial direction for an entire length of each recess of the plurality of first recesses.

A piston crown for a combustion system is disclosed. The piston crown includes a piston bowl having a circumferential recess and a plurality of first recesses arranged spaced apart from each other along a circumferential direction. The circumferential recess is disposed proximate to a circumference of the piston crown. Each recess of the plurality of the first recesses extends between a center of the piston crown and the circumferential recess, and a width and a depth of each recess of the plurality of first recesses are extended along a radial direction for an entire length of each recess of the plurality of first recesses.

An engine is provided, which includes a combustion chamber defined by a crown surface of a piston, an inner wall surface of a cylinder in which the piston is slidably accommodated, and a pentroof-type ceiling surface formed in a cylinder head and formed with an intake port and an exhaust port. The crown surface includes an exhaust-side bottom part, an intake-side bottom part, an exhaust-side sloped surface rising toward a center part of the crown surface from the exhaust-side bottom part, an intake-side sloped surface rising toward the center part from the intake-side bottom part, and a flat surface provided continuously between upper ends of the exhaust-side and intake-side sloped surfaces, and extending perpendicularly to a cylinder axial direction in the center part of the crown surface. A surface area of the flat surface is larger than a surface area of the exhaust-side sloped surface.

An engine is provided, which includes a combustion chamber defined by a crown surface of a piston, an inner wall surface of a cylinder in which the piston is slidably accommodated, and a pentroof-type ceiling surface formed in a cylinder head and formed with an intake port and an exhaust port. The crown surface includes an exhaust-side bottom part, an intake-side bottom part, an exhaust-side sloped surface rising toward a center part of the crown surface from the exhaust-side bottom part, an intake-side sloped surface rising toward the center part from the intake-side bottom part, and a flat surface provided continuously between upper ends of the exhaust-side and intake-side sloped surfaces, and extending perpendicularly to a cylinder axial direction in the center part of the crown surface. A surface area of the flat surface is larger than a surface area of the exhaust-side sloped surface.

A piston may have an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, a plane containing the longitudinal axis and the radial direction, and a contoured combustion bowl. In the plane containing the longitudinal axis and the radial direction, the crown portion includes a radially outer squish surface, and a swirl pocket having a reentrant surface that extends axially downwardly and radially outwardly from the squish surface defining a tangent that forms a reentrant angle with the squish surface that ranges from 53.0 degrees to 57.0 degrees.

A piston may have an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, a plane containing the longitudinal axis and the radial direction, and a contoured combustion bowl. In the plane containing the longitudinal axis and the radial direction, the crown portion includes a radially outer squish surface, and a swirl pocket having a reentrant surface that extends axially downwardly and radially outwardly from the squish surface defining a tangent that forms a reentrant angle with the squish surface that ranges from 53.0 degrees to 57.0 degrees.

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).

The piston has a contoured combustion bowl with a radially inner shelf portion that is spaced axially away from the radially outer lip portion a first axial distance, and a swirl pocket that extends radially from the radially inner shelf portion and defines a lower axial extremity that is spaced axially away from the radially outer lip portion a second axial distance that is greater than the first axial distance. The swirl pocket defines a tangent extending in the radially outer direction, forming an acute angle with the radially outer lip portion ranging from 70 degrees to 80 degrees.