Tappet Rotation and Friction Reduction in a Center Pivot Rocker Arm Contact

[+] Author and Article Information
P. A. Willermet, J. M. Pieprzak, D. P. Dailey

Scientific Research Laboratory, Ford Motor Co., Dearborn, MI 48121

J. Tribol 112(4), 655-661 (Oct 01, 1990) (7 pages) doi:10.1115/1.2920312 History: Received January 17, 1990; Revised June 01, 1990; Online June 05, 2008


The instantaneous tappet rotation velocity and instantaneous friction torque were measured simultaneously for the CVH center pivot rocker arm geometry. The measurements were made in a cam/tappet friction apparatus equipped with a laser reflectance tappet rotation monitor capable of following rapid changes in tappet rotation velocity. The data showed that more rapid tappet rotation resulted in lower friction. The effect was greatest in the region of maximum cam lift. Several tappets were modified to produce higher rotation rates than production tappets. The best results were obtained with tappets incorporating an internal squeeze film bearing to reduce resistance to rotation. The data were analyzed to elucidate the cause for the friction reduction effect. The analysis showed that most important effect was the partial rolling motion between the surfaces, rather than enhancement of the oil film thickness. A model based on that conclusion agreed reasonably well with the experimental data.

Copyright © 1990 by The American Society of Mechanical Engineers
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