An internal combustion engine comprises a variable compression ratio mechanism that changes the relative position of a cylinder block with respect to a crankcase and a controlling device that controls the variable compression ratio mechanism. The variable compression ratio mechanism contains a driving device that rotates a shaft that includes an eccentric axis, and the drive device includes a clutch that blocks reverse input and is disposed in a drive power transmission route that transmits the rotational power of a motor to the shaft. The control device fixes the mechanical compression ratio to a predetermined low mechanical compression ratio when the amplitude of the rotational power vibration applied to an output shaft of the clutch is less than a predetermined determination value.

An internal combustion engine comprises a variable compression ratio mechanism that changes the relative position of a cylinder block with respect to a crankcase and a controlling device that controls the variable compression ratio mechanism. The variable compression ratio mechanism contains a driving device that rotates a shaft that includes an eccentric axis, and the drive device includes a clutch that blocks reverse input and is disposed in a drive power transmission route that transmits the rotational power of a motor to the shaft. The control device fixes the mechanical compression ratio to a predetermined low mechanical compression ratio when the amplitude of the rotational power vibration applied to an output shaft of the clutch is less than a predetermined determination value.

A cylinder liner for an opposed-piston engine, and corresponding methods of extending engine durability and thermal management therewith, has opposite ends and a bore with a longitudinal axis for supporting reciprocating movement of a pair of opposed pistons. An intermediate portion of the liner extends between the opposite ends and includes an annular liner portion within which the pistons reach respective TC locations. A liner ring is seated in a portion of the bore in the annular liner portion, between the TC locations, for scraping carbon from top lands of the pistons and/or increasing the thermal resistance of the annular liner portion.

A cylindrical sleeve for an internal combustion engine is disclosed. The cylindrical sleeve includes a hollow cylindrical sleeve body, extending along an axial direction, with an inner peripheral side that has, along the axial direction, a first axial portion and a second axial portion. The inner peripheral side in the first axial portion is either cylindrical or opens at a first opening angle towards the second axial portion. The second axial portion opens at a second opening angle away from the first axial portion that is greater than the first opening angle. A first surface roughness of the inner peripheral side in the first axial portion is greater than a second surface roughness in the second axial portion.

An iron-based sprayed coating for coating a bore inner surface of a cylinder block for an internal combustion engine. A coating surface contains pits, its pit amount is within a range of 0.01% to 2.1%, and an average roughness Ra of this coating surface is within a range of 0.01 μm to 0.15 μm. The cylinder block for an internal combustion engine includes a bore having this iron-based sprayed coating on its inner surface, and a cylinder block body having the bore. A sliding mechanism for an internal combustion engine includes this cylinder block for an internal combustion engine and a piston slidable with the bore of this cylinder block. The piston has a piston ring, and the piston ring has a chromium coating, a chromium nitride coating, or a diamond-like carbon coating at a sliding part with the bore.

An iron-based sprayed coating for coating a bore inner surface of a cylinder block for an internal combustion engine. A coating surface contains pits, its pit amount is within a range of 0.01% to 2.1%, and an average roughness Ra of this coating surface is within a range of 0.01 μm to 0.15 μm. The cylinder block for an internal combustion engine includes a bore having this iron-based sprayed coating on its inner surface, and a cylinder block body having the bore. A sliding mechanism for an internal combustion engine includes this cylinder block for an internal combustion engine and a piston slidable with the bore of this cylinder block. The piston has a piston ring, and the piston ring has a chromium coating, a chromium nitride coating, or a diamond-like carbon coating at a sliding part with the bore.

A cylinder liner assembly for inclusion in the cylinder bore of an internal combustion engine includes a sleeve-like cylinder liner and an anti-polishing ring to scrape combustion deposits from a piston reciprocally movable along an axis line of the cylinder liner. A fire dam may axially protrude from a first liner end of the cylinder liner and may have an obliquely angled chamfer disposed therein circumscribing the axis line. To locate the anti-polishing ring proximate to the top land of the piston when at the top dead center position, the anti-polishing ring can include a cuff header disposed at the first cuff end that is generally triangular and has an angled undercut corresponding to the obliquely angled chamfer. When mated, the chamfer and angled undercut abut against each other.

A cylinder block that can be used commonly in a longitudinally mounted engine and a transversely mounted engine without increasing a manufacturing cost. The cylinder block comprises an attachment flange joined to a transmission or a transaxle, and an oil pan or the oil pan and a ladder frame are attached to a lower end thereof. The attachment flange comprises: a first flange formed on an outer periphery thereof; a first joint surface formed on the first flange to be joined to a matching surface of the transmission; a second flange extending in the inner side of the first flange; and a second joint surface formed on the second flange to be joined to a matching surface of the transaxle.

A cylinder block that can be used commonly in a longitudinally mounted engine and a transversely mounted engine without increasing a manufacturing cost. The cylinder block comprises an attachment flange joined to a transmission or a transaxle, and an oil pan or the oil pan and a ladder frame are attached to a lower end thereof. The attachment flange comprises: a first flange formed on an outer periphery thereof; a first joint surface formed on the first flange to be joined to a matching surface of the transmission; a second flange extending in the inner side of the first flange; and a second joint surface formed on the second flange to be joined to a matching surface of the transaxle.

An internal combustion engine has a cylinder block and a cylinder head fixed to each other with a plurality of bolts, and a piston fitted in a cylinder bore of the cylinder block so as to be able to reciprocate. A portion of the cylinder bore having a minimum diameter in a travel range of a skirt across which the skirt travels as the piston reciprocates is located within a range facing the skirt when the piston is at a bottom dead center. A clearance between the skirt and the minimum-diameter portion has a minimum value of a clearance between the skirt and a wall surface of the cylinder bore.