General

Cylinder block (CB) is the main component of an internal combustion engine that integrates engine cylinders into a single block manufactured by casting with further machining

CB crankshaft seating (cylinder block crankshaft bed) is designed for mounting bushes and crankshaft while keeping the required oil clearance.

Cylinder block bottom supporting plane is designed for oil pan installation.

CB top support plane is designed for cylinder head installation.

Cylinders within the cylinder block are designed for conversion of the reciprocating piston motion and for transmission of fuel-air explosion energy through connecting rods to crankshaft rotational motion.

CB cylinders can be cast as a single piece (dry liner), where the coolant does not come into contact with the liner wall, or as an insert (wet liner), where the coolant comes into contact with the liner wall.

Spaces for coolant (tosol, antifreeze agent) circulation are arranged around CB cylinders (cylinder block water jacket). In addition, oil channels are arranged inside of the CB. They deliver motor oil to lubrication points under pressure generated by the oil pump and provide correct function of friction bearings of the entire internal combustion engine.

The CB is made of cast iron or aluminium alloy. Cast iron was the only material for cylinder block manufacturing for a long time. It is relatively inexpensive, has high strength, wear resistance, hardness, and good castability. Major deficiencies of cast iron are its high specific weight and low thermal conductivity.

Aluminium alloy is a light (low specific weight) corrosion-resistant free-machining constructional material. Its thermal conductivity is 3 times higher than that of cast iron, hence the internal combustion engine heats up faster and more uniformly. The combination of these factors helps raise the efficiency and economy of internal combustion engines.

Aluminium alloy falls short of cast iron in terms of hardness and wear resistance. For this reason aluminium cylinder blocks shall have special structural elements to increase its hardness. Cast iron liners poured into an aluminium block during manufacturing are usually used as cylinders. Aluminium cylinder blocks have modern coatings. Aluminium cylinder surface is usually saturated with silicon carbide crystals (alusil, silumal). This innovation uses a technology for transition to oversize. Cylinders made of this material are easy to maintain. Moreover, aluminium cylinders are covered with wear-resistant coatings with a shallow layer thickness, therefore they are unrepairable.Such cylinders have a complex maintenance pattern where the design allows for it, i. e. where there is sufficient distance between cylinders for cast iron liner installation

In the course of work, CB cylinders are subject to wear.

CB cylinder wear is the result of combined effect on its walls of multiple physical, chemical and other swift-flowing processes that are divided into 3 main types by manifestation:

• erosive  — occurs as a result of piston rings friction on the CB cylinder, seizure and other destructive processes due to direct contact of metal friction surfaces;
• corrosive — occurs due to different oxidizing processes on friction surfaces;
• abrasive — leads to friction surface damage if solid abrasive particles, including internal combustion engine mechanism wear products, are present between these surfaces.

Worn out internal combustion engine parts shall be replaced or repaired. Repair is followed by machining that includes: cylinder boring for honing, cylinder boring for CB cylinder liner installation (standard or non-standard liners), CB cylinder honing, CB plane machining.

Boring of CB cylinders for liner installation.

Cylinder boring is performed on Rottler F7A/F8A boring machines produced in the USA.

There are two methods for locating the cylinder block when boring liners:

• CB is located on parallel guides, where machining is performed from CB oil pan plane, and cylinder location geometry is provided by unique structural possibilities of the equipment. This method has its peculiarity: boring is only possible with cylinder blocks that have minimum permanent elastic deformations of CB planes.

• CB is installed on a boring bar, where machining is performed from the crankshaft axis to maintain the alignment of cylinder axis to crankshaft axis with maximum accuracy. This method is most preferable for CB cylinder boring, however, for V-type CBs machining from crankshaft axis is the only possible variant.

The housing for cylinder liner installation is prepared according to the liner installation method (see para. 3). Cylinder surface roughness after boring Ra = 0.63 µm (boring surface roughness) is provided by special removable cutting plates with a rounded corner of 0.80 mm;

Cylinder liner installation.

The installation of iron cylinder liners of standard and non-standard sizes into aluminium and iron cylinder blocks is performed.

There are 3 cylinder liner installation methods:

• liner installation with top support (liner with collar);
• liner installation with bottom support (liner without collar);
• installation of a pennant liner (liner without collar); the liner seating reliability is provided by the size overlapping value.

Cylinder liner installation into CB is performed by cooling of the cylinder liner in a liquid nitrogen container up to –180 °C and heating of the CB up to 100 to 120 °C. In order to provide the reliable installation, the temperature difference between the CB and the liner shall be about 200 °C. As a result of liner cooling its diameter reduces by 0.1 mm and the liner mounting bore expands up to 0.25 mm after heating, hence a 0.35 mm clearance appears during installation, which allows easy installation of the cylinder liner into the prepared CB housing

Boring of CB cylinders for honing.

See "“Boring of CB cylinders for liner installation”".

Cylinder boring is performed with an oversize of 0.08–0.10 mm for honing. This oversize is sufficient to remove deformed surface layer of the liner material with uneven hardness formed during boring, as well as to correct the cylinder shape defects.

CB cylinder honing.

Finish machining of the cylinder liner working surface is performed by honing on Rottler HP6A equipment produced in the USA.

CB cylinder honing is finish machining using diamond hone-stones that are placed in a special tool carrier and attached to a honing head.

Rotational and reciprocating motions of the tool are mixed during honing, which ensures a specific profile (hone profile) as a result of movement of diamond grains along the spiral line.

Honing effectively corrects CB cylinder surface and shape defects, such as: taper, bow, barrel, waviness.

The operation performed on Rottler HP6A equipment produced in the USA provides unique results: cylinder size on manufacturer-specified cylinder length is sustained with an accuracy of 0.005 mm.

Surface roughness after honing is precisely sustained depending on the fuel type:

• for petrol engines Rz = 3–6 µm, Ra = 0.6–1.0 µm;
• for diesel engines Rz = 4–8 µm, Ra = 0.8–1.2 µm;

Roughness can be measured using a special instrument, profilograph, that apart from the roughness values Rz, Ra allows to view and print out a roughness diagram of the inspected cylinder surface. Apart from the cylinder size, geometry, roughness, another important parameter under inspection is a hone profile angle. The hone profile angle is within 30–80 °, which matches the recommendations of the world's leading ICE manufacturers (Kolbenschmidt, Mahle). We also maintain angle parameters specified by customers. Angle inspection is performed using hone angle pattern film.

The finish step of cylinder honing is brushing (plateau honing). This operation creates a support surface for piston and rings by removing microroughness peaks, and provides for at least 20 % of uncoated spherical flake graphite on the cast iron cylinder (cylinder liner) surface, which matches the quality requirements of the world's leading ICE manufacturers.

Conclusion.

Cast iron cylinder (cylinder liner) machining includes repair of the following parameters:

• cylinder size (along X-Y axis) to a tolerance of +0.005 mm;
• cylinder geometry (along axis) to a tolerance of +0.005 mm;
• surface roughness;
• hone profile angle;
• uncoated spherical flake graphite percentage. The following parameters were introduced and inspected:
  - equipment possibilities;
  - instrument quality;
  - special grinding fluid quality;

CH plane machining.

CB plane machining is performed on Rottler S7M, S8M, SFOE, SF1400 machines. Machining for special and quarry machinery is performed on a Rottler F98Y working centre.

The work is performed using a cutter, a carbide blade mounted on a revolving table. The cutting tool rotates parallel to the CB jointing plane and the material is fed along the CB plane. This provides for non-flatness accuracy of not more than 0.010 mm and roughness for any gasket type as specified by ICE manufacturers.

Surface roughness after machining meets the requirements of the leading gasket and sealing manufacturers such as GOETZE, Elring, Payen.