A modified design for hydraulic engine mount to improve its vibrational performance

Recently, hydraulic engine mounts have been used widely as an effective vibration isolator in automotive engines. They consist of two fluid chambers connected by an inertia track path and a decoupler mechanism with a floating plate. An ideal hydraulic mount should have high stiffness and damping at low frequencies and at high frequencies should act as a good isolator. Despite their acceptable performance, there are some drawbacks including switching, nonlinear behavior of the decoupler plate at low frequencies, and occurrence of the resonance due to the passage of the fluid through the decoupler in the high-frequency range. This paper proposes a new decoupler mechanism where the floating decoupler plate is replaced with a membrane where its tension could be controlled considering the operational frequency. Considering the discrete model of the operating fluid and the continuous model of the membrane, governing equations of the system are derived. By increasing the membrane tension at low frequencies, it is shown that the desired dynamic stiffness and damping can be achieved and the nonlinear switching behavior is eliminated. At the same time, by decreasing the membrane tension at high frequencies, it is shown that there is a significant increase in system compliance, resulting in better isolation. Results also show that the membrane replacement also eliminates the fluid resonances at high frequencies. Finally, the two-objective optimization method of the genetic algorithm is employed to find the optimal values of the membrane tension and the mount parameters. The results show that the proposed mechanism can be used as a suitable alternative to the conventional hydraulic mounts.