A member having a sliding contact surface that exerts a reduced frictional force when making sliding contact with a prescribed member and retains the lubricating oil more uniformly is provided. The sliding contact surface is a honed surface having flat plateau parts and groove parts. As calculated in regard to the sliding contact surface by using a mean line derived from a cross-sectional curve of the sliding contact surface in accordance with ISO 13565-1, a ten-point average roughness is 0.6-7.0 m, a load length ratio at a cut level of 20% is 60-98%, an effective load roughness is 0-1 m, and a mean value of intervals between the groove parts having a depth of 0.2 m or greater from the mean line is 79-280 m.

An internal combustion engine with at least one cylinder having a cylinder barrel that forms a guide for a piston associated with the cylinder. The cylinder barrel is only partially formed by a cylinder wall of a crankcase or of a cylinder liner fastened to the crankcase. The cylinder barrel, in a central region as seen in the cylinder axial direction, is formed by the cylinder wall. The cylinder wall, in an upper region of the cylinder barrel adjoining the central region and/or in a lower region adjoining the central region, has an encompassing recess into which is inserted a one-piece or multi-piece annular sliding element, the radially inner wall of which forms a part of the cylinder barrel.

An internal combustion engine with at least one cylinder having a cylinder barrel that forms a guide for a piston associated with the cylinder. The cylinder barrel is only partially formed by a cylinder wall of a crankcase or of a cylinder liner fastened to the crankcase. The cylinder barrel, in a central region as seen in the cylinder axial direction, is formed by the cylinder wall. The cylinder wall, in an upper region of the cylinder barrel adjoining the central region and/or in a lower region adjoining the central region, has an encompassing recess into which is inserted a one-piece or multi-piece annular sliding element, the radially inner wall of which forms a part of the cylinder barrel.

A machine having a cylinder, the configuration of the machine being such that a body portion of a piston of the machine periodically engages an inner surface of the cylinder during operation of the machine, this engagement defining a contact zone between the body portion of the piston and the inner surface of the cylinder, the inner surface of the cylinder having an enhanced bearing region comprising one or more recesses indented into the inner surface, the enhanced bearing region being smaller than the inner surface of the cylinder and being substantially centered on the contact zone.

A machine having a cylinder, the configuration of the machine being such that a body portion of a piston of the machine periodically engages an inner surface of the cylinder during operation of the machine, this engagement defining a contact zone between the body portion of the piston and the inner surface of the cylinder, the inner surface of the cylinder having an enhanced bearing region comprising one or more recesses indented into the inner surface, the enhanced bearing region being smaller than the inner surface of the cylinder and being substantially centered on the contact zone.

To provide a piston ring free from microwelding to a piston while exhibiting excellent wear resistance in side surfaces, for a long period of use in a high-temperature, high-pressure environment, and its production method, a nitride layer is formed on at least one of upper and lower side surfaces of the piston ring, and then subjected to a phosphate chemical conversion treatment, such that the nitride layer has at least one of granular and vermicular surface forms.

An engine cylinder block includes a cylinder block housing and a double-crankshaft mechanism installation case located at a downside of the cylinder block housing. The cylinder block housing is integrally connected with the double-crankshaft mechanism installation case. The cylinder block housing is provided with a cylinder block cavity. The double-crankshaft mechanism installation case is enclosed and formed by an end cover and a side cover. A piston rod guiding groove is installed in the double-crankshaft mechanism installation case. A connecting rod sliding groove is configured through the piston rod guiding groove. A crank operation cavity is configured on both sides of the piston rod guiding groove. A main spindle installation hole is configured on the shell at both ends of each crank operation cavity. A main spindle supporting portion is configured below the main spindle installation hole.

An engine cylinder block includes a cylinder block housing and a double-crankshaft mechanism installation case located at a downside of the cylinder block housing. The cylinder block housing is integrally connected with the double-crankshaft mechanism installation case. The cylinder block housing is provided with a cylinder block cavity. The double-crankshaft mechanism installation case is enclosed and formed by an end cover and a side cover. A piston rod guiding groove is installed in the double-crankshaft mechanism installation case. A connecting rod sliding groove is configured through the piston rod guiding groove. A crank operation cavity is configured on both sides of the piston rod guiding groove. A main spindle installation hole is configured on the shell at both ends of each crank operation cavity. A main spindle supporting portion is configured below the main spindle installation hole.

A structural frame is provided. The structural frame includes a bottom surface, first and second cylinder block sidewall engaging surfaces, the first and second cylinder block sidewall engaging surfaces positioned above the bottom surface at a height that is above a centerline of a crankshaft support included in a cylinder block when the structural frame is coupled to the cylinder block.

A machine having one or more cylinders, each cylinder having an inner surface configured to engage a circumferential surface of a piston ring of a piston thereby defining a contact zone between the inner surface of the cylinder and the circumferential surface of the piston ring, the inner surface having at least one recess indented into the inner surface, wherein the ratio of the dimension of the recess in the direction of travel of the piston to the dimension of the contact zone in the direction of travel of the piston is in the range of approximately 1:5 to 3:5.