Analysis And Design Of Magneto-rheological Isolator Used On Automobile Engine

When engine runs, it’s moving parts suffer some imbalance force and torque thatproduce a wide frequency vibration and transfer it to the car body. This is not only todecrease riding comfort but also to cause noise. At present, passive rubber andhydraulic mounts are widely used in engine vibration isolation, they can effectivelyreduce the vibration in the low frequency range. But for the limitations that thedamping and stiffness are not controlled and the dynamic stronger situation, theycan’t attach to the affect of vibration isolation for a wide frequency. Along with thedevelopment of intelligent materials such as magnetorheological fluids, the rheologic-al properties of MRF that visco plastic will change if the magnetic field intensitychange can be applied to the engine vibration isolator, and this is becoming a trend ofengine vibration isolation’s research.The chief content of this paper includes the following aspect:1) Composition、Macroscopic and microscopic mechanical properties of MRF,generating mechanism and influence factors of the MR effect. The rheologicalproperties of MRF，the performance of Magnetism，viscosity temperature andviscosity pressure are described.2) The basic characteristic and evaluation index of the engine vibration isolationsystem is introduced. Analysis the engine excitation source and determine theimbalance force and torque that can cause vibration.3) Based on Navior-Stokes’ equation and Double viscosity Model, contact to theworking principle of MR vibration isolation device, be considered with the power lawproperty and boundary slip condition, a new squeeze model of MRF’s flow betweenthe two parallel disks is put forward. MRF’s radial velocity distribution in thenewtonian region and double viscosity district are got from theoretical derivation, andthe flow state under different power rate characteristic is analysised. At the last,basedon the the pressure gradient and the equation of continuity, the explicit expression ofdisk extrusion pressure is obtained that provide damping,and how are the power-lawcharacteristic and boundary slip effected on it is analysised.4) Based on the basic design guidelines of vibration isolator and magnetic Ohm’slaw and Ampere’s law, magnetic circuit of MR vibration isolator is designed, thestructure of MR vibration isolator is also designed. Combined the prior theory’s analysis, the desired number of turns and current density of excitation coil areestablished. The relationships between the damping force of MR vibration isolatorand current are obtained, and the range of the damping force value is established, thenstiffness calculation of isolator is done.5) The magnetic loop simulation analysis of MR vibration isolator is done byusing the software ANSYS, this verifies the rationality of magnetic circuit’s design.The dynamic model of vibration isolation system is established,and Matlab/Simulinksimulation analysis of MR vibration isolator’s dynamic behavior is done under thedifferent operating condition.