Study On The Tribological Problems Of Oil-free Scroll Compressor

As a simple structure, low noise, high efficiency and good reliability positivedisplacement device, Scroll compressors develop quickly in compressor areas. Inrecent years, with the rapid development of industrial production, some specialoccasions need the high pressure gas not be polluted by lubricating oil, such as food,pharmacy, air separation fields and so on. In order to meet the manufacturing needs,Oil-free Scroll Compressor is the choice in these special occasions. At present, rictionpair of Oil-free Scroll Compressor lubrication is achieved through the self-lubricatingmaterials. The properties of self-lubricating and the character of sliding against steelplay an important role in performance of scroll compressors. Therefore, study on theproperties of self-lubricating materials and sliding against steel are very impoatant fordesing of self-lubricating materials and theoretical calculation of scroll compressors.This paper first measure surfaces profiles of PEEK with stylus profilometer. Onthe basis of fractal geometry, fractal characteristics of PEEK contour curves wereanalyzed. Result show that initial surface of PEEK has obvious fractal characteristics.To research the relationship between different surfaces roughness and fractaldimensions of PEEK, based on the different roughness of PEEK, fractalcharacteristics and fractal dimensions were analyzed. Then, the fit curve about thefractal dimensions and roughness was created by the SPSS statistical software.Results show that the fractal dimensions could be characterized as an independentparameter to represent the complex degree and roughness level of rough surface.Fitting result indicated that, for the PEEK, decrease relationship was existed betweenthe fractal dimensions and roughness, namely, if the roughness higher, the fractaldimension lower. Through the relationship between the fractal dimensions androughness, within a certain range, fractal dimension D could be got through theroughness.According to fractal theory, fractal dimension of PEEK surface profile andfriction coefficient and their correlation, investigated the relationship of originalsurface characteristics of self-lubricating materials PEEK and its friction performancewhen PEEK sliding against QT.Different surface roughness and different surfaceprofiles of PEEK were measured with stylus profilometer, friction tests of PEEK andQT were carried out on an UMT-3MT wear tester. On the basis of fractal geometry, fractal characteristics of PEEK contour curves and friction coefficient were analyzed,and their fractal dimensions were computed with structure function method. Fittingresults show that: the initial surface profile curve of PEEK and friction signals bothhave obvious fractal characteristics; the fractal dimensions of friction signal havelarger relationship with properties of materials, processing methods, and the initialsurface morphology of materials and friction experimental condition. The fractaldimension of friction coefficient curve decreased with the increase of surface fractaldimension.Friction performance tests were carried out by QT respectively soliding withPEEK composite or PI composite material.The test results show that: frictioncoefficient and its fractal dimension of original surface PEEK composite is moresmaller; so it can serve as a good self-lubricating materials; the Processing method ofthe lubricating material surface can use pressure film forming.