On Surface Topography of Cylinder Liners

Licentiate thesis, 2008

The frictional losses, oil consumption and emissions in internal combustion engines are in great extent controlled by the cylinder liner surface topography. This emphasises the importance of: investigating the liner’s topography by objectively characterising it, investigating its effects on the tribological function to gain a better understanding and improving its manufacturing. As a first attempt in this study to objectively characterise the liner surface, a traditional combination of Scanning Electron Microscope (SEM) images and roughness profiles was used. The groove and image parameters characteristic for liner topographies were extracted by applying specially developed algorithms and together with the standard parameters served to study wear on liners of diesel and petrol engines. An experiment was designed to improve the liners’ manufacturing by varying of the honing process parameters and oil flow simulations were run to study the influence of the characteristics of the manufactured surfaces on their function. The results suggested that reducing the base honing pressure and increasing the plateau honing time gave the best surface with smoother plateaux, summits of higher density and milder slopes, more but smaller islands and shallower valleys. The potentials of fast acquiring and containing 3D data of the interference measurements were utilised to overcome the encountered problems in the usage of the combination of profile and SEM measurements and to enable automatic quality control of the cylinder liner surfaces. In the efforts to examine the influence of the surface properties on liner’s function, the extent of blechmantel (cold work material) removal was estimated from 3D measurements of run liners in engine tests. For characterising this feature, algorithms were developed and implemented and it was found that the most of the blechmantel is still left on the liner pointing that it plays a minor role on wear.