Development and analysis of switchable hydromounts for engine mounting

Hydromounts are a type of passive engine mount that offer advantages over simple rubber mounts. Hydromounts are tuned to the resonance frequency of the engine on its mounts, providing increased damping. The aim of the current work is to investigate a method for implementing a two-state hydromount and develop a model to describe it. A quarter car model is first used to consider different damping strategies for an engine mounting. Measurements were carried out on a proprietary hydromount and the results were compared to a model with linear and non-linear forms, and the sensitivity of the model to changes in the parameters was studied. The model was optimised using particle swarm optimisation, giving an improved fit, particularly at higher amplitudes. The main mismatch was found at the resonance peak. The hydromount model was then adapted to include a second inertia track and compared with experimental data. Ultimately a good agreement was found and this could be used in designing two inertia track systems. A theoretical analysis of the compliance of an annular diaphragm is presented, and used to aid in the estimation of the compliance of the chambers of the mount along with equi-biaxial inflation of circular rubber diaphragms. For the system studied there was a large variation in calculated compliance with the changes in chamber pressure. Inclusion of the hydromount model in the quarter car model suggested that it is important to have high damping over a large bandwidth to control the behaviour around the resonance. Experimental work carried out on an adaptive system showed that altering the upper chamber volumetric compliance of a hydromount and controlling a second tuned frequency via a second inertia track could both be successful strategies for implementing a two state mount. A switching mechanism was also developed that relies on the use of a magnetorheological fluid. This versatile solution would potentially allow both retrofitting into existing devices and use in applications other than engine mounts