Experimental Study and Modeling of Hydraulic Mount and Engine System

Hydraulic (fluid) mounts use the inertia of a fluid to provide high damping over a narrow range of frequencies. This high damping is useful for reducing vibrations, such as engine idle shake. The various configurations of hydraulic mounts can be divided into two categories: single and double-load-bearing fluid chambers. Mathematical models in the literature^{(1, 2, 3, 4, 5 and 6)} for both categories are reviewed. A more comprehensive model for the single-load-bearing-chamber fluid mount has been developed and validated by comparison with experimental data. This model relates dynamic properties of hydraulic mounts to device parameters, such as chamber stiffness, channel length, channel cross-sectional area (orifice size), and fluid density. These device parameters can be internally manipulated to change mount performance. This comprehensive model was used for initial design of a fluid engine mount. The resonances for the engine/mount system were then determined using experimental modal analysis. The mount was tuned for one of the rigid body mode frequencies of this engine/mount system by varying device parameters as directed by the model. The tuned mount substantially reduced vibration at this frequency.