Abstract

The engine excitation forces, arising from gas pressure and unbalance force, are widely considered among the main vibration sources for the road vehicles. Even though the current engine mount designs are acceptable for vibration isolation of the transmitted forces from engine to chassis, the performance improvement of the engine mounting system is still required for the tendency of light weight and higher power of the vehicle. In this thesis, a coupled three degree-of-freedom engine mount system with both elastomeric and hydraulic mounts, are developed. The system performance is evaluated through simulation with the purpose of isolating the vibrations in entire frequency range and under engine excitation force. The engine dynamic model is established based on the analysis of the kinematics and dynamics of its components and gas variation. The unbalanced inertia force caused by engine reciprocating and rotating parts is derived as the vertical excitation force. The net torque, generated by the inertia forces and gas pressure, is formulated using geometrical relationship of the engine components. Two types of individual mounts, including a nonlinear elastomeric mount and a flexible chamber hydraulic mount, are selected from the reported work. The validation of their characteristics is implemented in a single degree-of-freedom (SDOF) system with the response carried out in the time and frequency domain.