Title: Measurement devices for piston assembly friction and oil film thickness

Authors: Sung Woo Cho, Sang Min Choi, Choong Sik Bae

Addresses: Department of Mechanical Engineering, KAIST (Korea Advanced Institute, of Science and Technology) 373-1, Kusong-dong, Yusong-gu, Taejon 305-701, Korea. Department of Mechanical Engineering, KAIST (Korea Advanced Institute, of Science and Technology) 373-1, Kusong-dong, Yusong-gu, Taejon 305-701, Korea. Department of Mechanical Engineering, KAIST (Korea Advanced Institute, of Science and Technology) 373-1, Kusong-dong, Yusong-gu, Taejon 305-701, Korea

Abstract: A technique for estimating the instantaneous frictional force between the piston assembly and the cylinder wall has been developed by improving the moveable bore technique. The technique can be easily applied to small multi-cylinder engines since its structure is simple and stable so that the measuring range could be extended. The reliability of the friction data can be improved by a newly-proposed compensation method. The technique was applied to a four cylinder SI engine under various engine speeds, engine loads, and oil viscosity. An instrument for measuring the oil film thickness on the piston rings was also developed by using the commercially available gap sensors. It was possible to measure the oil film thickness on thin oil ring rails as well as on the compression rings. The frictional characteristics were established as a relationship between frictional mean effective pressure and a parameter which is the product of the piston mean speed and the oil viscosity.

Keywords: frictional force; lubrication; moveable bore; oil film thickness.

DOI: 10.1504/IJVD.2002.002020

International Journal of Vehicle Design, 2002 Vol.29 No.4, pp.390-402

Published online: 15 Aug 2003 *

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