Challenges of Hydraulic Engine Mount Development for NVH Refinement

NVH refinement of passenger vehicle is essential to customer acceptance for premium or even mid-size segment passenger cars. Hydraulic engine mount is becoming common for these segments to reduce engine bounce, idle shake and noise transfer to passenger cabin. Modern layout of hydraulic mount with integrated engine-bracket and smaller size insulator has made it cost-effective to use due to reduction of cost gap from conventional elastomeric mounts. However the downsizing and complex internal structure may create some new types of noises in passenger cabin which are very difficult to identify in initial development stage.

Main purpose of hydraulic mount is to provide high damping at low-frequency range (6~15 Hz) and to isolate noise transfer from combustion engine to passenger cabin within wide frequency range (15~600 Hz).This paper emphasizes on challenges and problems related to hydraulic mount development. Tuning of Hydraulic mount is required to avoid cavitation noise at low-frequency and also any abnormal noise due to hydraulic unit resonance at higher frequency. Design measures to curb NVH problems, e.g. cavitation noise, bump noise of mount stopper, resonance from hydro unit, at early development stage are explained in the paper.