The invention relates to a method for operating a reciprocating piston machine, particularly an internal combustion engine, having at least one piston rod that is hydraulically adjustable in length for setting a compression ratio, wherein the piston rod comprises a piston and a hydraulic cylinder for adjusting its length, wherein the piston with the hydraulic cylinder delimits at least one working chamber, through the fill level of which at least two switching positions of the piston rod are possible, wherein independently from the setting of the compression ratio the working chamber is at least partially filled and emptied as a function of at least one first predetermined requirement to effect an at least partial exchange of a hydraulic medium in the at least one working chamber.

The invention relates to a method for operating a reciprocating piston machine, particularly an internal combustion engine, having at least one piston rod that is hydraulically adjustable in length for setting a compression ratio, wherein the piston rod comprises a piston and a hydraulic cylinder for adjusting its length, wherein the piston with the hydraulic cylinder delimits at least one working chamber, through the fill level of which at least two switching positions of the piston rod are possible, wherein independently from the setting of the compression ratio the working chamber is at least partially filled and emptied as a function of at least one first predetermined requirement to effect an at least partial exchange of a hydraulic medium in the at least one working chamber.

A hydraulic cylinder (10) comprises a cylinder tube (12) having a circular slide hole (13), a piston unit (18), and a piston rod (20). The piston unit (18) has a circular piston body (40), packing (42) that is installed on the outer circumferential portion of the piston body (40), a movable member (44) that is mounted to the outer circumferential portion of the piston body (40) so as to be able to rotate relative to the piston body (40), and a magnet (46) that is held by a magnet holding unit (58) of the movable member (44). Relative rotation of the movable member (44) with respect to the cylinder tube (12) is regulated.

A hydraulic cylinder (10) comprises a cylinder tube (12) having a circular slide hole (13), a piston unit (18), and a piston rod (20). The piston unit (18) has a circular piston body (40), packing (42) that is installed on the outer circumferential portion of the piston body (40), a movable member (44) that is mounted to the outer circumferential portion of the piston body (40) so as to be able to rotate relative to the piston body (40), and a magnet (46) that is held by a magnet holding unit (58) of the movable member (44). Relative rotation of the movable member (44) with respect to the cylinder tube (12) is regulated.

Provided is a compression ratio varying mechanism, including a communication hole including: a first opening opened in an outer peripheral side surface of a piston rod; and a second opening, which is prevented from being opposed to the first opening in a radial direction of a piston rod, and is connected to an oil passage at a position apart from the first opening in a stroke direction.

Provided is a compression ratio varying mechanism, including a communication hole including: a first opening opened in an outer peripheral side surface of a piston rod; and a second opening, which is prevented from being opposed to the first opening in a radial direction of a piston rod, and is connected to an oil passage at a position apart from the first opening in a stroke direction.

A piston rod unit and a method for producing a piston rod unit, or a shaft, in light-weight construction, with a rod which is hollowly-drilled by means of a deep bore into the rod shank, and the resulting rod opening is closed subsequently by means of a forging process.

A piston rod unit and a method for producing a piston rod unit, or a shaft, in light-weight construction, with a rod which is hollowly-drilled by means of a deep bore into the rod shank, and the resulting rod opening is closed subsequently by means of a forging process.

An internal combustion engine may include an engine block, a cylinder defining at least one combustion chamber, and a piston in the cylinder. The piston may travel in a first stroke from one end to an opposite end of the cylinder, and may be sized relative to the cylinder to enable an expansion stroke portion of the first stroke while the piston travels under gas expansion pressure, and a momentum stroke portion of the first stroke for the remainder of the first stroke following the expansion stroke portion. A passageway may be formed in the piston rod to communicate gas flow between a first combustion chamber and an area external to the cylinder when the piston is in a first position, and to communicate gas flow between a second combustion chamber and an area external to the cylinder when the piston is in a second position.

An internal combustion engine may include an engine block, a cylinder defining at least one combustion chamber, and a piston in the cylinder. The piston may travel in a first stroke from one end to an opposite end of the cylinder, and may be sized relative to the cylinder to enable an expansion stroke portion of the first stroke while the piston travels under gas expansion pressure, and a momentum stroke portion of the first stroke for the remainder of the first stroke following the expansion stroke portion. A passageway may be formed in the piston rod to communicate gas flow between a first combustion chamber and an area external to the cylinder when the piston is in a first position, and to communicate gas flow between a second combustion chamber and an area external to the cylinder when the piston is in a second position.