Piston ring topography variation and robust characterization

• It is a constant challenge for the automotive industry to reduce friction losses and oil consumption in automobile engine. The piston ring friction accounts for approximately 20% of the total mechanical energy losses in a modern engine. Oil control rings limit and control the oil consumption of the engine as well. They scrape off excess lubricating oil from the cylinder walls and return it to the crank case. Piston rings are designed to distribute the thin oil film evenly to ensure piston and ring lubrication. The surface topography of a piston ring is an efficient variable in the control of the oil consumption and friction losses. In places where the interacting surfaces come in contact, the oil film thickness is extremely thin and the surface asperities may deform because of the high pressures. There are different types of oil control rings.The most common one is the twin land oil control ring, which consists of two narrow lands that scrape off the oil on the liner and a spring on the back that exerts the load. In this paper, the surfaces of the two lands were investigated, since they play the key role in its function. The goal is to map the variation in surface roughness of piston rings that appear at different scales from form and waviness to micro and nano roughness. Areal topography measurements were made by white light interferometer designed at the Halmstad University able to measure and scan the total functional area of a piston ring. An significant amount of oil control piston rings of heavy duty truck engines were examined and 24 measurements were made in circumferential direction and on each ring land. The results show both the variation and uncertainty of the ring topography and discuss the instrument and measuring methodology uncertainty. The most stable parameters were found and recommended for an effective quality control. Comparisons between established coherence scanning interferometer and the instrument built in Halmstad were made. To ensure a good quality, the measurements were made both on calibration standards and on piston ring surfaces. Finally the influence on function and energy losses in the final engine assembly is discussed to indicate future design and metrology improvements.  

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

piston ring

white light interferometer

surface topography

measurement uncertainty

Publication and Content Type

ref (subject category)

kon (subject category)