Experimental and modeled effects of camshaft manufacturing errors on the dynamics of high-speed valve trains.

摘要

The idea of harnessing combustion to perform mechanical work is by no means a new one. The internal combustion engine, as we know it today, has its origins in the last century, however the idea for controlling combustion to perform mechanical work dates back to the Renaissance. Even with the advent of alternative sources of power for commerce and personal applications, the internal combustion engine represents a large portion of the power generation available in this country.; There are numerous types of internal combustion engines, each with a variety of subsystems. While all of these types and corresponding subsystems are equally important, this investigation is focused on the valve train dynamics of a pushrod type internal combustion engine. Operating this type of engine at too high of an engine speed usually causes dynamic malfunctions such as spring surge, lifter/cam pair separation, valve bounce, etc. in the valve train. Although the interaction of each of the valve train components contributes to the limit speed, the shape of the cam plays a critical role. Therefore, this investigation will look at how small changes in the cam profile due to manufacturing errors change the dynamics of a valve train in a pushrod type engine.; Automotive cams can be manufactured as copied or original parts. Copied parts are typically produced on a rocker type cam grinder and the original parts are produced on a computer numerical control grinder. Therefore, various errors associated with these manufacturing techniques are studied herein.; Installing cams with profile errors in an engine may result in the dynamic malfunction of its valve train. In order to study the effect of these profile errors, some of the error cam profiles that were predicted for the rocker grinder were manufactured and tested in an actual valve train. In addition, the effects of error cam profiles were investigated by using an existing valve train simulation model. It was found by both experimentation and simulation that camshaft errors on the order of typical shop tolerances had little impact on the dynamics of high speed valve trains.