Torsional vibrations in an automotive drive-line equipped with a magneto-rheological elastomeric spring damper

A torsional vibration absorber for automotive transmission, based on the MagnetoRheological effect of an elastomeric spring, is proposed to attenuate the torsional oscillations responsible of many vibro-acoustic disturbances. The spring element of the damper is constituted by a Magneto-Rheological elastomer, at which a suitable magnetic field can be applied in order to change its modulus and so the dynamical characteristics of the damper. The magnetic field can be varied by controlling the current in a coil surrounding the elastomeric element. In particular the damper can be tuned to operate in a desired frequency range as requested by the operative conditions of the transmission drive-line. Some numerical simulations of the transmission dynamic behavior are presented to describe interesting performances of the device in order to reduce annoying effects of the undesirable torsional vibrations, such as the gear rattle noise in the gear box. A technique based on the relieves of the gears accelerations has been applied on the numerical results, in order to evaluate the effectiveness of the torsional vibration damper in reducing the angular irregularities. Moreover an index based on the Wavelet multi-resolution analysis has been applied to confirm the goodness of the device in reducing the gear rattle.