| Loader is primarily utilized to load and unload piles of balk cargo and also do some light excavations. It has good mobility, applied widely in factory,mine,construction,water and electricity,road,dock,farmland even house, and it is a most important model of construction machinery. As far now, the portion of the loader industry of our country has already reached 50 percent of the whole world, and our country has become No.1 production and market of the world.With the construction performance becoming more and more strenuous, it is requested to enhance productivity consecutively, meanwhile, the increase in the weight of construction machinery request the steering system of the construction machinery to overcome larger steering inoment of resistance and possess some steering speed, this means the enhancement of steering power. Runners only need little operating force and general speed to control steering components with liquid being the transmitter of hydraulic powered steering system, and the energy to overcome great resistance with high speed is provided by engine, this not only improves driver's working condition and enhances productivity, but also increases safety performance on driving. Hydraulic steering system is one of the most important systems of the loader, and its functions are to manipulate the driving direction, guaranteeing both the vehicle stability of linear driving and flexibility of steering. Steering performance is a important factor to guarantee driving safety and alleviate driver's working intension and enhance productivity. The steering system the paper discusses is "dual-pump unloading hydraulic system with merge and division flow and coaxial flow amplification, steering on priority", whose shortened form is "unloading system with coaxial flow amplification", adopting full hydraulic steering,coaxial flow,unloading system. Its core is coaxial flow amplifier, produced by Chinese Hydraulic Institute for Farm Equipment Academy and Zhenjiang Main Hydraulic Components Company, bearing advantages both of small volume,little weight and little output volume for flow amplification system,of energy-saving for load sensing steering, and of realizing manual steering to meet an emergency for the steering system with little output volume. This is a new hydraulic steering system, adopted by several main domestic loader-producing companies recently, but there is no relative study on its steering performance. This paper focuses on static and dynamics characteristic of the steering system to enhance the stability and reliability of steering performance, thus, the product is applied more widely. Because the steering system is the newest one applied to the loader, and it is a very important to affect safety property and productivity of the loader, it is necessary to study the static and dynamics characteristics of the hydraulic steering system and make the loader with it apply more widely.From the in-place steering experiment pressure curve made on the Exploiter loader, it can be seen that pressure in the working chamber of oil cylinder surge greatly at the beginning of steering, the reason for it is that the value of friction factor is the largest at that time, after that, the value will decrease, thus resulting in low pressure. The pressure fluctuation is caused by internal feedback of the steering system and steering wheel input of non-uniform velocity.To simulate the static and dynamics characteristics of the hydraulic steering system on the computer can shorten the period of hydraulic system or components design greatly. So the costly expense can be reduced in duplicate experiments and manufactures. Meanwhile the drawbacks in static and dynamics of the system can be detected and eliminated. Computer simulation can not only predict the function of the system during design, but also shorten the period to test the system and make the best understanding of the system.The paper establishes mathematics model of steering system through analyzing the working principle of the hydraulic s...
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