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.

An assembly includes a spring seat, a spring seat insert, and a seal. The spring seat is slidable along the spring seat insert to define an expandable fluid chamber therebetween. The spring seat includes a groove defining a mating surface. The seal is between the spring seat and the spring seat insert. The seal includes a mating portion at the first end engageable with the mating surface of the groove to prevent fluid from exiting the fluid chamber.

An assembly includes a spring seat, a spring seat insert, and a seal. The spring seat is slidable along the spring seat insert to define an expandable fluid chamber therebetween. The spring seat includes a groove defining a mating surface. The seal is between the spring seat and the spring seat insert. The seal includes a mating portion at the first end engageable with the mating surface of the groove to prevent fluid from exiting the fluid chamber.

The present disclosure is to provide a piston assembly in which a particle does not leak out of a cylinder, and including, in an embodiment, a piston body; a piston rod connected to the piston body; a first groove formed in an outer surface of the piston body; and a particle discharge flow path extending from an internal space of the piston body to the outer surface of the piston body.

The present disclosure is to provide a piston assembly in which a particle does not leak out of a cylinder, and including, in an embodiment, a piston body; a piston rod connected to the piston body; a first groove formed in an outer surface of the piston body; and a particle discharge flow path extending from an internal space of the piston body to the outer surface of the piston body.

A piston for a high temperature internal combustion engine is provided. The piston includes an upper wall, base wall, outer rib, and inner rib defining a cooling chamber therebetween, and a plurality of ring grooves formed in the outer rib. Only the second ring groove is formed with the keystone cross-section, and all of the other ring grooves are formed with the conventional rectangular cross-section. Thus, the piston can be formed with low manufacturing costs and can also provide exceptional performance when used in high temperature combustion engines, wherein the temperature at the first ring groove is greater than 280° C., and thus prevents carbon from depositing or burns off any carbon deposits, but the temperature at the second ring groove is between 200° C. and 280° C., in which case carbon deposits can form and cause the piston ring to stick.

A piston for a high temperature internal combustion engine is provided. The piston includes an upper wall, base wall, outer rib, and inner rib defining a cooling chamber therebetween, and a plurality of ring grooves formed in the outer rib. Only the second ring groove is formed with the keystone cross-section, and all of the other ring grooves are formed with the conventional rectangular cross-section. Thus, the piston can be formed with low manufacturing costs and can also provide exceptional performance when used in high temperature combustion engines, wherein the temperature at the first ring groove is greater than 280° C., and thus prevents carbon from depositing or burns off any carbon deposits, but the temperature at the second ring groove is between 200° C. and 280° C., in which case carbon deposits can form and cause the piston ring to stick.

An oil control ring according the present disclosure includes a pair of side rails, and a spacer expander disposed between the pair of side rails. The spacer expander includes a plurality of sets and each set includes a lug part and a rail facing part. For each set, the lug part is in contact with an inner circumferential surface of either of the pair of the side rails, and the rail facing part is provided adjacent to the lug part and faces a side surface of either of the pair of the side rails. The lug part satisfies a following condition (1):

W/H≥1.5   (1)

In condition (1), W indicates a width of the lug part at a position 0.05 mm away from a highest position of the lug part in a direction towards the rail facing part, and H indicates a height difference between a highest position of a region on the rail facing part adjacent to the lug part and the highest position of the lug part.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a first stroke from one end to another. The first stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion. The non-expansion stroke portion may include a scavenging phase. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a first stroke from one end to another. The first stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion. The non-expansion stroke portion may include a scavenging phase. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.