Simulation of low torque bushings in automobile suspensions

摘要

One of the primary functions of automobile suspension bushings is to isolate the vibrations being transmitted from the suspension to the passenger compartment. Under certain operating and road conditions, the viscoelastic characteristics of the rubber bushings are not sufficiently high to damp out the road disturbances. Also small amplitude disturbances from the road at the tire foot prints are usually too small to activate the shock absorber and hence are not easily damped out. Low torque bushings can improve this situation using Coulomb damping which is generated by providing a slip surface between the rubber and the inner or outer metal. This construction, therefore, allows the possibility of controlling the torsional deformation and limiting the torque transmitted under service conditions by adjusting the torque required to slip. In this paper, we study the behavior of low torque bushings in an automotive rear suspension and compare their performance against conventional bushings. The tire footprint is given an input to simulate the vehicle traveling over a bump and the responses of the bushings are computed. By varying the slip torque, it is shown that an optimum value exists which provides maximum dissipation. The frequency characteristics of the torque transmitted by the bushing are also presented.