New method for decoupling the Powertrain Roll mode to improve Idle Vibration 2019-01-1588
Modern engines have high torque outputs and have low RPM due to increased demand for fuel efficiency. Such engines have high vibration and must be mitigated for customer comfort. Decoupling the roll mode from the remaining five rigid body modes results in a vibratory response which is predominantly about the torque roll axis (TRA). Therefore, placing the mounts on the TRA early in the design phase is crucial. Best NVH performance can be obtained by optimizing the powertrain mount parameters like position, orientation and stiffness. Many times, packaging restricts the mounts to be placed about the TRA resulting in degradation in NVH performance. Assuming that the engine mounts cannot be moved, let the desired TRA be the line through the existing engine mount (body side) centers. We propose a novel method of shifting the TRA by adding mass modifying the powertrain inertia such that the new TRA is parallel to and on top of the desired TRA. This in turn will decouple the roll mode and reduce vibrations. This problem is formulated as an optimization problem. Example presented demonstrates the NVH improvement by modifying the Torque roll axis.
Syed F. Haider, AHMAD ABBAS, Francisco Sturla
FCA US LLC
Noise and Vibration Conference & Exhibition