The Structural Design And The Study On Isolation Characteristics Of A Semi-active Mount With Magnetorheological Fluids

Vibration isolation of automobile, especially vibration isolation of power plant is a kind of important technology of automobile design. Vibration affects not only the ride comfortableness, but also automobile's ride stability and safety. Mount is the primary vibration-isolation component between car body or chassis and power plant; its characteristic determines energy transfer between car body and power plant.Perfect automobile engine mounts should have the performance of low stiffness and proper damping. The conventional elastic rubber mounts can't meet these requirements because of the localization of their material. Hydraulic engine mounts can significantly alter performance of modern automobiles. Hydraulic engine mounts possess the advanced benefits ,such as reduced interior noise and vibration, improved ride quality. It is well known that the hydraulic engine mounts can provide excellent frequency and amplitude response characteristics compared to the conventional elastic rubber type ones. Such properties include that a large damping under excitation of high amplitude in the low frequency region, and low dynamic stiffness at low amplitude in high frequency region.As a kind of hydraulic mount, semi-active control hydraulic mount does not need active execute element that consumes large enery. Its dynamic performance can be shifted with the change of engine speed, so its performance of decreasing and isolating vibration is boosted as well as it has many kinds of advantages. Magnetorheological technology is a new and marginal science. Magnetorheological fluids is a kind of smart material, with the control of external applied magnetic field, its coefficient of viscosity and shear yield stress can berapidly changed, and this process is controllable, continuous, and reversible. With its particular performance, magnetorheological fluids can be used as controllable damping media, which brings a promising way to research the semi-active engine mount system.Magnetorheological fluids mount is a kind of new product in this paper. It achieves the control of damping due to the controllable yield stress of magnetorheological fluids through the applied magnetic field strength. It accomplishes the large range variable-damping through a magnetic coil installed at the bottom of the hydraulic mount. Magnetorheological fluids mount can avoid systemic resonant actively, decrease the amplitude of transmitted force abviously, isolate the vibration of engine in much wider frenquency range under the control of external magnetic field. Magnetorheological fluids mount will be widely used in the isolation of engine vibration system of automobile power plant in future.This paper introduces the present status of mount based on large amount of internal and external thesis. The develop process and category of different mounts have been introduced in detail, and the necessity of semi-active mount has been list. This paper presents concept and compose of magnetorheological fluids, analyzes characteristic of magnetorheological fluids. The mechanism of the magnetorheoligical effect is studied, and several kinds of models are built. The factors of magnetorheoligical fluids rheology are analyzed, at last the application and development trend of magnetorheoligical fluids are summarized.Later, the basic theory of engine is summarized, internal stimulation and isolated vibration principle are studied. The design requirement and collocation form of mount system are presented. This paper analyzes work principle and pattern of magnetorheoligical fluids mount, designs structure of magnetorheoligical fluids mount.Then, the relationship between damping of magnetorheoligical fluids mount and magnetic field strength , movement parameters, geometrical dimension is deduced. Elements of magnetorheoligical fluids mount are pointed out, the elements'size is also indicated. The mechanical and mathematical models of semi-active engine mount have been built, and method of control is put forward.At last, on the foundation of the mathematical model that has been set up in the front, a simulink model is set up in the end. The performance with control and without control is simulated in Matlab, the performance of reducing the transmitted force is analyzed under the difference engine speed. The result of the simulation indicates that semi-active engine mount can isolate the vibration transmitted by the engine to the vehicle chassis effectively, the transmitted force can be reduced about 50%, the displacement of engine is reduced obviously at the same time.