This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Engines such as I3 and I4 which are not inherently balanced require balance shaft to offset their first order (I3 engine) or second order (I4 engine) vibrations. The gears transmitting the engine rotation to the balance shaft can lead to NVH issues appearing as broad band rattling noise and/or narrow band tonal whine. Engine gear rattle and whine evaluation at an early stage of the design can help to avoid this type of error state. Upfront multi-body dynamics simulation of engines including gear components can provide directions for a robust design in terms of NVH attribute to prevent gear-related NVH issues. The analytical assessment can address both the source of the excitation and the path sensitivity under different engine loading conditions of steady full load, light load, fast run-up and/or run-down coast.
In order to reduce the excitation at the gear teeth, different gear microgeometry parameters (e.g., gear pressure angle, tip relief, teeth crowning, etc.) are investigated. This includes evaluation of path sensitivity, balance shaft positioning, mass and inertia distribution, component stiffening ( front cover, oil pan and supporting brackets) among the actions taken into consideration to achieve robust engine noise attenuation for these error states.
In this presentation, risk assessment for engine balance shaft gear rattle and whine errors states and their trade-off will be reviewed based on simulation results from use of Multi-Body Dynamics (MBD). The excitation leading to engine rattle and whine from the source through the path resulting in the engine vibration response will be thoroughly discussed. Additionally, various sensitivity analyses involving different engine loading conditions, gear backlash and gear micro-geometry levels will be presented. The output from the MBD analysis will be used to extend the engine vibrational assessment to acoustic response for gear rattle and whine. This includes generation of sound wave files simulating engine balance shaft gear rattle and whine.