Abstract: To study the effects of the excitation amplitude and frequency on the vibration modes of the hydraulic mounting system of powertrain, firstly the amplitude-dependent characteristics of the stiffness of the upper fluid chamber are analyzed, taking an inertial channel-type hydraulic mount as an example, the formulae of the amplitude-frequency characteristics of the mount stiffness is derived,and the methods of modal analysis and decoupling-degree calculation for the mounting system under the influence of nonlinearity is proposed. Then, a real case analysis on the vibration modes and decoupling-degrees of the hydraulic mounting system of powertrain with different amplitudes is carried out with this method. Finally, the criterion for modal type discrimination and the optimization objective of vertical decoupling-degree are summarized, and based on which an optimization on mount stiffness is conducted. The results show that the amplitude-frequency characteristics of hydraulic mount dynamic stiffness have a great influence on the vertical, torsional and rolling modes of the system, while the other modes are basically unaffected, and the optimized mount stiffness meet the requirements of vibration isolation.

Key words: powertrain mounting system, hydraulic mount, nonlinear characteristics, amplitude-dependent characteristics, modal analysis