Effective Reduction of Peak Frequency in Hydraulic Engine Mounts

Hydraulic engine mounts are generally applied to the aerospace and the automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of hydraulic mount design parameters, at a certain frequency, namely the notch frequency, the dynamic stiffness will be smaller than the static stiffness and cabin vibration and noise reduction is provided at that frequency. Literature review indicates that in all previous hydraulic engine mount designs, the dynamic stiffness increases after the notch frequency. This phenomenon is not desirable because of the increase in transmitted force to the air-frame. Here in this paper, a new hydraulic engine mount design is proposed that uses two working fluids. This new design has two notch frequencies and two peak frequencies. In this study, effective reduction of the peak frequencies has been demonstrated by using a controllable fluid as one of the mount’s working fluids and a non-controllable fluid as the 2^nd working fluid. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but no peak frequency. The new hydraulic engine mount design and its mathematical model are presented in details and some discussions on the simulation results are also included.