The Tribological Behavior of an Automotive Cam and Flat Lifter System

Abstract

In order to thoroughly characterize the cam/tappet contact, a simulator was designed and constructed which presents a lifter which is stationary except for rotation. The cam instead moves through the lift curve so that the contact remains essentially in the horizontal plane. Three components of contact force on the lifter are measured. A series of eight nominally flat lifter foot materials were investigated for frictional loss as a function of speed. In addition, the effects of oil temperature, running in, lifter rotation and lifter foot spherical radius was studied. With one of the lifters (Al2O3) the surface temperature of the cam was measured at peak lift employing an infrared scanning system. Peak temperatures in excess of 300° C were observed for some operating conditions. Preliminary measurements were made with a roller lifter. The loss per revolution ranged from 1.75 J to 3.9 J for the flat followers. The roller follower loss was 18 percent of that of the flat follower for similar conditions.