The Method to Predict the Vibration Transfer Function of Hydraulic Engine Mount on a Vehicle

The CAE method to predict the vibration transfer function of the hydraulic engine mount on a vehicle with sufficient precision and calculation time without prototype cars was developed. The transfer function is given in the following steps. First, rubber deformation form under the power train weight loaded must be predicted. It’s obtained by using a reduction model of an engine mount, as a unit, which doesn’t have its fluid sealed inside, with the technique to get the static spring characteristics in a non-linear relationship. Second, Young’s modulus and structural damping coefficient for the deformed rubber must be given. As for these characteristics, ignoring the relations between these values and strain, the constant values are used. This considerably reduces computation time and model size. Next, the reduction model and the fluid model have must be combined to express actual product. In this step, coupled analysis for fluid and structure is used. Finally, the vibration transfer function on a vehicle from the bolting point between the power train and engine mount to the bolting point between the body and engine mount, was predicted using a mode synthesis method. A short calculation time is also required in actual developments, so several techniques about modeling and giving calculation conditions to shorten the time are suggested. The above made it possible to examine medium- and high-frequency band noise (e.g. engine noise, gear noise, motor noise), at the initial stage of car development that has hydraulic engine mounts.