Surfaces of Honed Cylinder Liners
Cylinder liner surfaces are often on the agenda of engine developers because of their large influence on the frictional losses, oil consumption and emissions of internal combustion engines. Improving the liner function involves not only manufacturing new surfaces and checking their function but also characterising them as a necessary intermediate step for better understanding of the changes made. In the manufacturing of the liners, honing is a well adapted and widely used finishing process and along with the characterisation and function has been the subject of studies in this thesis. Regarding the liner’s function, three phenomena were monitored: wear, friction and oil passage rate (correlated with engine’s oil consumption). The first one was studied experimentally while the other two were simulated. Only the interactions with the twin land oil control ring were simulated as it has the greatest influence on the control of friction and oil consumption of all other rings. In the mid-stroke region of truck engine liners, the presence of axial wear scratches was observed and their relation with the removal of the cold worked material (“Blechmantel”) folded inside the deep honing grooves was investigated. Algorithms were developed for estimating the extent of Blechmantel, revealing that most of it remained on the surface whereas the engines still performed well. Other algorithms for characterising honing angle, balance of honing texture, width, height, distance between honing grooves/axial wear scratches, etc were developed for quicker and more objective inspection of unworn and worn surfaces from 3D interference measurements. Based on such 3D measurements, the algorithms were incorporated in a characterisation tool enabling rating of the surfaces and determining the number of measurements necessary to achieve stable roughness parameter values. In addition, it was found that interference measurements are more suitable for quantification of the deposits on the worn truck liner surfaces compared with scanning electron microscope measurements. The lubrication and friction of flat oil control ring lands and differently slide honed surfaces of truck liners were simulated. Friction mean effective pressure and oil passage rate were calculated for each surface showing in each case a reduction for the surfaces with smoother plateaus and smaller valleys. Such a liner surface was finished by using a low base honing pressure and a longer plateau honing time. In a car engine, the influence of different liner surfaces, ring land widths and tensions was examined by running simulations. The results suggest that a considerably improved function can be achieved if the ring land width and tension are reduced whereby the differences between the liner surfaces would reduce.