Dramatic increases in fuel and lubricant costs together with longer life expectancy and significantly higher power ratings through turbocharging have led to priorities in engine development over the last eight years which place high demands on piston rings. These demands include: Better sealing (low blow-by)
Improved oil scraping (increased oil economy) Less friction (reduced fuel consumption) Lower wear rates (longer engine life) Faster and more reliable running-in (reduced production costs).
Modified edge designs on compression rings guarantee low blow-by. A special lapping process for chrome plated rings increases scuff resistance and reduces running-in time. Oil scraper rings with extremely narrow lands manufactured to very fine tolerances by profile grinding permit the use of low tangential loads for reduced friction. The use of such ring designs in European diesel engines is proving successful.
Since the first energy crisis in 1973, the developmental aims in the engine construction sector in Europe and elsewhere have concentrated above all on the achievement of maximum economy.
Whereas previously, increases in output brought about by higher r.p.m. and higher mean effective pressures plus the whole question of exhaust gas emissions occupied the foreground, the most important developmental aims at present are the reduction of fuel consumption, the attainment of maximum oil economy and the longest possible service life.
The problem areas of scuffing, oil consumption and ring breakage which used to be the determining factors in piston ring development for heavy duty engines, have been joined by additional demands for greater gas tightness, i.e. less blow-by in the engine, reduced friction and minimum wear rates. Ring designs, running surface strengthening and ring materials which are solving these problems in Europe, form the contents of this paper.