Cam Gear Walk off in a Diesel Engine

Abstract

A diesel engine, for the heavy commercial vehicles, employing a helical engine gear train which was developed by Cummins a few issues were observed with the cam gear while engine over speeding. A failure of cam gear walk-off was observed due to which the timing of the engine was affected leading to failure of the engine. Current understanding for the root cause of failure is significant torsional vibrations introduced in the gear train at over-speeds. The preliminary tests and studies to the issue suggested changing the helical gear train to the spur gear train as this would fit into the gear cover with the same work envelope and without axial thrust but would require a thorough research so that it works properly with low vibrations. The gears are expected to work in various speed and load ranges, due to which they experience higher dynamic loads further giving rise to various failure modes like bending fatigue and surface wears which hamper the functioning and life of the gear train. Therefore, to improve the durability and reduce noise a thorough dynamic analysis of the system should be done. The dynamic response of the gear system is a lot sensitive to the modifications of the tooth profile from a perfect involute. Thus, intentional modifications to the micro design of the tooth profile is to be done to reduce the dynamic forces at some torque values. In this project, the spur gear train will be designed so as the vibrations are least by checking the dynamic response of the model and further the micro design will be modified to reduce the wear of the teeth of the gears. The joint capacity analysis and the gear web design will also be done.