Liner of cylinder block is the most crucial part of the cylinder and piston group of the internal combustion engine. Internal surface of the liner together with piston head forms combustion chamber and serves as a guide for piston motion.

Liner (sometimes called sleeve) has a cooling hollow - jacket, or, in case of air cooling - cooling fins, which ensure intensive heat removing from internal running surface to maintain the necessary heat balance of cylinder and piston group.

Among the heat-beat parts of the engine cylinder liner is of a particular importance due both to functions and to demands made to it. Ensuring of only strength of cylinder liner, notwithstanding the importance of this requirement, is not enough for long-term and reliable engine operation.

The surface of cylinder block is used as running only in some small diameter engines. The majority of modern water-cooled engines use the so-called wet cylinder liner.

In wet liner the outer surface - jacket has a direct contact with coolant.

In some small and medium capacity engines the so-called dry cylinder liner is used. Its outer surface does not have direct contact with coolant.

Dry cylinder liners with wall thickness of about 2-4 mm are pressed-in or installed into cylinder block with 0,01-0,04 mm gap. Small thickness of dry liners make for high-quality materials saving, but higher temperature lag of area of contact between the liner and the block worsens heat removing from cylinders to the coolant. Consequently in augmented engines wet liners are usually used as they ensure effective heat transfer and they are easy to replace if worn.

Design of wet liners has certain peculiarities depending upon application and type of engine. In automotive and tractor diesel engines wet liners with upper bearing flange are used. At the same time clamping force of block head is often non-uniformly distributed over the circumference and as a result of it the shape of cylinder running surface is deformed, efficiency of cylinder and piston group is reduced and oil consumption is increased.

In carburetor engine clamping force is smaller and bearing flange of the liner is sometimes noticeably shifted from the upper part of the block that is why temperature of the upper part of sleeve and correspondingly of piston rings is reduced.

For correct installation in the block and shape retaining cylinder liners are centered on two registers. Diameter of the upper register is a bit large than that of the lower, as in the lower register 0,05-0,13 mm gap is provided for ensuring of sleeve stretching during operation. Cooling hollows are sealed with special rubber rings, which are installed into grooves of cylinder block or liner grooves on the lower register. As a rule two or three rings are installed. One of them has a rectangular cross section. The rectangular ring of a large height prevents from wear and cavitation in the area of lower register.

Chemical composition, material structure, precision of liner making, microrelief of running surface are the basic criteria determining general reliability of the engine, anti-friction properties of tribological situation piston ring - cylinder liner and set up conditions for complete fuel burning, thermal cycles efficiency increase and performance index of engine increase.

That is why the precision of dimensions of some elements of cylinder liner amounts to less than 5 mkm, that is a characteristic feature of parts produced by precision engineering and instrument-making industries.

The most crucial parameters of liners are achieved by using special technologies and their specific quality is estimated by means of special high-accuracy control devices.

Organization of high-tech kinds of production including foundry, machining and heat-treatment, is necessary for cylinder liner manufacture.

Cylinder liners produced by centrifugal casting method are the most suitable to meet chemical composition and material structure requirements. Centrifugal casting method ensures 95-100% pearlite presence in material structure. Such liners are characterized by compact material structure, required disposition of graphite grains, which further prevents intensive wear of running surface during operation. Subsequent heat treatment excludes the change of liner dimensions in the process of operation in the engine.

That is why Motordetal-Konotop OOO produces 90% of cylinder liners using this method.

A special attention is paid by the specialists of Motordetal-Konotop OOO to honing of running surface of cylinder liners.

Only the technology of plateau-peak honing used by Motordetal-Konotop OOO enables to achieve at least 40% opening of graphite. At the same time the imprecision of running surface shape does not exceed 5 mkm.

Honing, rather technology of plateau-peak honing, abrasive instrument, unique tooling, western experience of cylinder liner production, using of modern high-accuracy equipment made by leading manufacturers of cutting machines enable Motordetal-Konotop OOO to ensure:

• quick run-in of twain (ring - cylinder face),
• forming of necessary oil layer thickness on friction surface,
• minimal oil burn-off,
• necessary engine operation conditions,
• essential increase of cylinder and piston group resource.