Analytical methods of decoupling the automotive engine torque roll axis

This paper analytically examines the multi-dimensional mounting schemes of an automotive engine-gearbox system when excited by oscillating torques. In particular, the issue of torque roll axis decoupling is analyzed in signif icant detail since it is poorly understood. New dynamic decoupling axioms a re presented an d compared with the conventional elastic axis mounting and focalization methods. A linear time-invariant system assumption is made in addition to a proportionally damped system. Only rigid-body modes of the po wertrain are considered and the chassis elements are assumed to be rigid. S everal simplified physical systems are considered and new closed-form solut ions for symmetric and asymmetric engine-mounting systems are developed. Th ese clearly explain the design concepts for the 4-point mounting scheme. Ou r analytical solutions match with the existing design formulations that are only applicable to symmetric geometries. Spectra for all six rigid-body mo tions are predicted using the alternate decoupling methods and the closed-f orm solutions are verified. Also, our method is validated by comparing moda l solutions with prior experimental and analytical studies. Parametric desi gn studies are carried out to illustrate the methodology. Chief contributio ns of this research include the development of new or refined analytical mo dels and closed-form solutions along with improved design strategies for th e torque roll axis decoupling. (C) 2000 Academic Press.