TABLE OF CONTENTS This chapter presents two case studies of cam-follower systems taken from the author's consulting experience that proved to be both interesting and challenging. One is an automotive valve train and the other is an application from industrial machinery.
This study was done to determine what information could be obtained from the analysis of experimentally measured acceleration, velocity, and displacement of the valve in a modern overhead camshaft (OHC) valve train. The measured data were compared to the theoretical cam functions as designed. This information has been reported previously in [1]. Modern OHC IC engine valve trains are designed to operate at high speed for 300 million camshaft revolutions or more with very little maintenance. The displacement functions used for valve motion in the DaimlerChrysler 2.0L inline 4-cylinder, 16-valve engine are "shape-preserving" splines[2]. The acceleration function over the valve motion event shown in Figure 17-1 is a quadratic spline, making the velocity a cubic spline, and the displacement a quartic spline.[3] The two "square waves" of acceleration that precede and follow the motion event are the "ramps" of constant acceleration. The ramp that precedes motion is intended to wind up the compliance in the follower train (principally in the hydraulic lash adjuster) prior to the actual opening of the valve so that the timing of valve opening will be accurate. The ramp following the motion event is intended to control the impact velocity of the valve against the valve...
