Effect of Engine Mount Damping on the Torque Roll Axis Decoupling 2007-01-2418

Several mounting system design concepts have been conceptually used to decouple the engine roll mode though limited success is observed in practice. One shortcoming of the existing theories is that they ignore damping in their formulations. To overcome this deficiency, we re-formulate the problem for a non-proportionally damped, linear system while recognizing that significant damping may be possible with passive (such as hydraulic), adaptive or active mounts. Only rigid body modes of power train are considered and chassis is assumed to be rigid. Complex mode method is employed and the torque roll axis (TRA) paradigms are re-examined in terms of mount rate ratios, mount locations and orientation angles. We will show that true TRA decoupling is not possible with non-proportional damping though it is theoretically achieved for a proportionally damped system. Results for both steady state (in the form of frequency response functions) and transient (given impulsive excitations) responses will be illustrated. The natural modes obtained using complex eigensolution method are coupled for the non-proportional damping case, even though they are completely decoupled for the proportional damping case. It is also seen that a higher value of non-proportionality induces more coupling between the rigid body motions of a powertrain. Our method and results are expected to lead to a better design of the mounting systems.