Development of High Performance Exhaust Mountings

The rubber mountings used to support the exhaust piping in automobiles also play important roles in isolating the cabin of the vehicle from the exhaust pipe vibrations. Through our evaluation on the characteristics and mechanism of vibration transmission behavior of the rubber mountings, it was confirmed that dynamic stiffness of the rubber mounting increases at specific frequency ranges, and thereby increases the vibration transmission to the cabin in those frequencies. It was identified by both Modal and FEM analyses of the rubber mounting structure that this phenomenon of increase in dynamic stiffness is induced by resonance modes of the rubber which inherently accompanies the structure of conventionalrubber mounting designs. Sensitivity analysis of the vehicle body at the installation points of the rubber exhaust mountings in the piping line, confirmed that frequencies of high sensitivity zones coincide or are near the resonance frequencies of the rubber mounting. This is assumed to be a big factor to worsen the noise and vibration in the cabin from the exhaust pipes. Through careful study of the modes of the rubber resonance phenomenon, a new structure design for rubber exhaust mountings has been developed. Characteristic tests and vehicle evaluations confirmed that the new design mountings can successfully suppress the inherent resonace modes of the rubber mounting in the problem frequencies, and subsequently reduce vehicle vibration and noise when installed.