A piston includes a crown having a deck, a spark recess, an exhaust valve recess, and an intake valve recess. The piston also includes a wedge disposed on the crown extending from the exhaust valve recess and the intake valve recess toward the spark recess above the deck. The wedge is a planar wedge disposed at an angle substantially parallel to an associated exhaust valve received by the exhaust valve recess. The crown is symmetrical about a piston center line.

A piston includes a crown having a deck, a spark recess, an exhaust valve recess, and an intake valve recess. The piston also includes a wedge disposed on the crown extending from the exhaust valve recess and the intake valve recess toward the spark recess above the deck. The wedge is a planar wedge disposed at an angle substantially parallel to an associated exhaust valve received by the exhaust valve recess. The crown is symmetrical about a piston center line.

A piston for an internal combustion engine may include a piston crown, a piston body, and a ring portion. The piston body may have a radially outermost piston outer surface, which may emanate from the piston crown and extend axially and in a circumferential direction. The ring portion may be disposed axially spaced apart from the piston crown. The ring portion may extend axially and in the circumferential direction. The ring portion may include a ring carrier with a ring groove configured to receive a piston ring. The ring portion may further include a radially outer ring portion outer surface that extends in the circumferential direction. The ring portion outer surface may be disposed radially to an inside relative to the piston outer surface. The piston outer surface may extend elliptically in the circumferential direction. The ring portion outer surface may extend rotation-symmetrically in the circumferential direction.

A piston for an internal combustion engine may include a piston crown, a piston body, and a ring portion. The piston body may have a radially outermost piston outer surface, which may emanate from the piston crown and extend axially and in a circumferential direction. The ring portion may be disposed axially spaced apart from the piston crown. The ring portion may extend axially and in the circumferential direction. The ring portion may include a ring carrier with a ring groove configured to receive a piston ring. The ring portion may further include a radially outer ring portion outer surface that extends in the circumferential direction. The ring portion outer surface may be disposed radially to an inside relative to the piston outer surface. The piston outer surface may extend elliptically in the circumferential direction. The ring portion outer surface may extend rotation-symmetrically in the circumferential direction.

An engine is provided, which includes a combustion chamber defined by a piston crown surface, an inner wall surface of a cylinder, and a pentroof ceiling surface formed in a cylinder head, and an ignition part of a spark plug disposed at the ceiling surface to achieve flame propagation combustion inside the combustion chamber. A cavity recessed in a spherical cap shape is formed in a central area of the crown surface. An opening of an intake port is formed in the ceiling surface (intake side) and an opening of an exhaust port is formed in the ceiling surface (exhaust side). When seen in a cross-sectional view taken along a cylinder axis, the ignition part is located above the cavity to be offset toward the exhaust side with respect to a cylinder axial line whereas a cavity center point is located to be offset toward the intake side.

An engine is provided, which includes a combustion chamber defined by a piston crown surface, an inner wall surface of a cylinder, and a pentroof ceiling surface formed in a cylinder head, and an ignition part of a spark plug disposed at the ceiling surface to achieve flame propagation combustion inside the combustion chamber. A cavity recessed in a spherical cap shape is formed in a central area of the crown surface. An opening of an intake port is formed in the ceiling surface (intake side) and an opening of an exhaust port is formed in the ceiling surface (exhaust side). When seen in a cross-sectional view taken along a cylinder axis, the ignition part is located above the cavity to be offset toward the exhaust side with respect to a cylinder axial line whereas a cavity center point is located to be offset toward the intake side.

A resin coat film 39 formed on a skirt portion 10 of a piston 7 has a four-sided outer peripheral region knurled at upper and lower regions thereof corresponding in a rear view of the piston 7 to an upper skirt part 36 and a lower skirt part 38 of the skirt portion 10 extending in parallel with an axial direction of left and right piston pin boss portions 15 and 14, with a combination of short vertical grooves 43A and 43B and medium-length vertical grooves 42A and 42B extending in parallel with a central axis C of a piston crow portion 9, and at left and right edge regions thereof, with long vertical grooves 41.

A resin coat film 39 formed on a skirt portion 10 of a piston 7 has a four-sided outer peripheral region knurled at upper and lower regions thereof corresponding in a rear view of the piston 7 to an upper skirt part 36 and a lower skirt part 38 of the skirt portion 10 extending in parallel with an axial direction of left and right piston pin boss portions 15 and 14, with a combination of short vertical grooves 43A and 43B and medium-length vertical grooves 42A and 42B extending in parallel with a central axis C of a piston crow portion 9, and at left and right edge regions thereof, with long vertical grooves 41.

An internal combustion engine with a piston having a piston head with a resonance cavity opening onto the head, and where a fuel nozzle located in a cylinder head is positioned to inject a fuel such as natural gas into the combustion chamber where resonance formed within the resonance cavity will ignite the fuel without the need of a spark plug. Inlet and exhaust ports in the cylinder head allow for air and combustion gas enter or leave the combustion chamber.

A piston for an internal combustion engine may include a ring belt, a groove, and an additional groove. The ring belt may extend along an axial direction. The groove may be arranged on the outer circumference of the ring belt and may be configured to receive an oil scraper ring. The additional groove may be arranged on the outer circumference spaced apart from the groove with respect to the axial direction. The additional groove may include a first groove side axially facing away from the groove and a second groove side axially facing the groove. The first groove side may include an axial step.