A cylinder liner is an insert in the cylinder of a reciprocating engine that forms the running surface for the piston .
Engine blocks (cylinder crankcase ; ZKG) are made of aluminum or cast iron , in rare applications also as a magnesium-aluminum composite structure. However, the piston does not always run directly in the engine block material, because this material does not meet higher tribological requirements and the replacement of the piston and cylinder as the main wearing parts is considerably more complicated. This is why a cylinder liner is often installed. The inner surface of this liner is usually bored after installation (in the case of “wet” cylinder liners before installation) and finely machined by honing . This ensures the geometrical shape and surface roughness required by the manufacturer in order to meet the required tribological properties. The surface must not be too rough (piston wear), but also not completely smooth - rather, it must ideally have micro-reservoirs for the lubricating oil, which is achieved through porosity or certain grinding patterns. The "finishing" is done by the piston with its piston rings when the engine is retracted.
Materials and designs
Materials for cylinder liners:
- Cast iron (gray cast iron): pores and flake graphite are good for lubrication; possibly the same material as the engine block
- Aluminum alloys with silicon: possibly the same material as the engine block
- Steel (rare)
Depending on the type of installation in the engine block, a distinction is made between “wet” and “dry” liners. The engine coolant washes around wet cylinder liners. They alone form the cylinder, have a wall thickness of 7 to 15 mm and are used with a seal. Dry liners are only a few millimeters thick and are shrunk or poured in, e.g. B. with the Alfer process .
Advantages: easily exchangeable, optimal cooling (direct contact with the cooling medium), high stability due to the large wall thickness
Disadvantages: Sealing problematic (oil against cooling water), engine block less stable, cylinder head gasket endangered
Advantages: Stable engine block, no additional sealing required, material savings due to thin wall thickness, high accuracy of fit, dimensional accuracy and wear resistance
Disadvantages: hardly replaceable, difficult to use, poor cooling due to air pockets
Advantages: very stable engine block, high wear resistance, accuracy of fit and dimensional accuracy, optimal cooling, can be mechanically inserted into the mold
Disadvantages: not replaceable, cracks can form in the engine block, starting from the joint between the bushing and the engine block
Engine blocks without liners can be provided with a wear and friction reducing coating. This results in a weight reduction and space savings between the cylinders. Coatings are e.g. B .:
- Nikasil : silicon carbide particles dispersed in a galvanic nickel layer
- So-called nanoslide ( Daimler AG ): nanocrystalline iron-carbon layer applied by arc wire spraying , post-processing by honing, which opens pores and improves lubrication
- Plasma-sprayed steel-molybdenum composite ( Volkswagen AG , Sulzer Metco , now OC Oerlikon ): Post-processing Honing exposes the pores - better lubrication
- Hans Jörg Leyhausen: The master craftsman's examination in the automotive trade, part 1 . 12 edition, Vogel Buchverlag, Würzburg, 1991, ISBN 3-8023-0857-3
- Wilfried Staudt: Vehicle Technology Handbook, Volume 2 . 1st edition, Bildungsverlag EINS, Troisdorf, 2005, ISBN 3-427-04522-6
- Peter Gerigk, Detlev Bruhn, Dietmar Danner: Automotive engineering . 3rd edition, Westermann Schulbuchverlag GmbH, Braunschweig, 2000, ISBN 3-14-221500-X
- ↑ http://www.moto-selmer.de/technik,motor-einfahren.html
- ↑ http://www.kfz-betrieb.vogel.de/neue-ylinderbeschichtung-bei-daimler-a-330312/
- ↑ Archived copy ( Memento of the original dated December 3, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Sulzer Technical Review 2/2001 page 8ff