Behavior Analysis And Test Of Wheel Loader's Dynamic Load Sensing Hydraulic Steering System

Wheel Loader is a construction machinery with a single bucket, front dumping,articulating.It can be widely used in construction worksite,port wharf,station and storage,mainly used for loading or transporting in short distance 1oose materials such as earth,stones,coal and dust,further more is can be used for ground 1eveling,towing,stacking and piling. And so,it is a high-efficient and multi-function construction machinery. Every year there are more than 100,000 wheel loaders for sale in china and almost made in China. Wheel loader is best for competing with other countries for world market in Chinese brand construction machinery. Wheel loader develops to reliability, high-efficiency, fuel economy, low exhaust emissions, easy service, electro-mechanism, automatization, information and multi function with computer technology, auto control technology and information technology developing and applying abroad to the construction machinery, Wheel loader hydraulic system is made up of implement hydraulic system, power steering hydraulic system and power shift transmission hydraulic system. Development of implement hydraulic system has three phases. The three phases are from hand direct control flow divider valve to hydraulic pilot control flow divider valve and to computer control electro-hydraulic system. Control performance and automatization advance step by step. Hydraulic steering system is one of the most important systems of the wheel loader, and its functions are to manipulate the driving direction, guaranteeing both the vehicle stability of linear driving and flexibility of steering. Basic request of wheel loader is low-effort conventional steering wheel, smooth, stability, reliability and durability. Steering performance is a important factor to guarantee driving safety and alleviate driver's working intension and enhance productivity. It is important to research and develop hydraulic steering system of wheel loader. The emphases of research and development about hydraulic steering system is open center with non reaction type system in China and the load-sensing type hydraulic steering system is also developing, but only first generation. The first-generation load-sensing system means static load-sensing system. The second-generation load-sensing system means dynamic load-sensing .It is mostly developed and applied in other countries around world. The steering system the paper discusses is dynamic load-sensing hydraulic steering system. The paper discusses classify, structure and working principle of hydraulic steering system. The paper summarizes and analyzes working principle and characteristics of dynamic load-sensing hydraulic steering system, and analyzes its load compensate characteristics. This paper also builds mathematics model of dynamic load-sensing hydraulic steering. The paper calculates area of orifice and analyzes system vibration reason and eliminating approach. Meanwhile, analyze the function of the static and dynamics characteristics of the hydraulic steering system, and use the means of transfer function to analyze the structure of the steering system and search the regular pattern that the structure parameters influence the steering system. And calculates prime component parameter and designs wheel loader steering system and do experiment on stability, drop pressure, leakage and linear, the result make it clear that the model is correct. Research dynamic load-sensing hydraulic steering system and conclude these conclusions as below: To verify the correctness of the principle and the model made up of hydraulic pump, priority flow divider valve, dynamic load-sensing hydraulic steering unit and hydraulic cylinder. Driving wheel loader is easy because of its load compensate characteristics. To Build mathematics model of dynamic load-sensing hydraulic steering system and direct design of wheel loader steering system The stability and rate of response are directly influenced by the velocity amplify parameter k v. For the steering unit with little displacement, the stability is good For the steering unit with large displacement, the stability is bad but the rate of response is good. Hydraulic inherency frequency ? n be dependent of the parameter E,V t ,A c,M p and independent of the structure parameter of steering unit.When frequency changed between 2? nξn and ? n, the output has nothing to do with the load. The dynamics location rigidity is not change when frequency of system change in this range, the value is the rigidity of hydraulic spring. The fallibility of system is zero for the step input, and is direct ratio with the constant velocity input, but is inverse ratio with the velocity amplify parameter, and this system can't follow constant acceleration input. To designs wheel loader steering system and do experiment on stability, drop pressure, leakage and linear, the result make it clear that the model is correct.