Powertrain Mounting Design Principles to Achieve Optimum Vibration Isolation with Demonstration Tools

The way a powertrain is mounted plays an important role in improving vehicle noise and vibration caused by the engine firing forces and can be an effective role in improving vehicle ride comfort. This paper describes the basic concepts in powertrain mounting and derives a new concept of evaluating powertrain mounting. It is well known in publications that a decoupled powertrain mounting system has better NVH characteristics^[3][4][6]. But how to relate percentage of decouple to powertrain mounts transmitted forces, what “decoupled” really means, and how to evaluate how much it is decoupled are still ambiguous to many engineers. The traditional “one coordinate system” kinetic energy fraction (KEF) index can't give a clear picture of how much the engine mounting is decoupled and is often misleading. The new concept focuses on the excitations acting on the powertrain system. The KEF index is simulated in global, engine and torque roll axis (TRA) coordinate systems, and the evaluation of decoupling is directed to a specific excitation. The global coordinate KEF index focuses on road and wheel excitation; the engine coordinate KEF index focuses on engine cylinder direction forces and corresponding torques excitation; and the TRA coordinate KEF index focuses on the crankshaft torque variation excitation which is critical for idle isolation.