Research And Development Of Drive System For Full-hydraulic Wheel Loader

The hydraulic loader is a loader whose drive system and work system use hydraulic transmission, which has advantages of compact structure, low noise, light weight and infinitely variable speeds, etc. therefore, the development of hydraulic loader has become a trend.This paper analyzed the hydraulic system of full-hydraulic wheel loader, took the choice of hydraulic components, and then made modeling and simulation with Matlab/Simulink, which provided theoretical foundation to the research of full-hydraulic wheel loader. The main research contents of this paper were as follows:(1) The components of the hydraulic transmission system consist of the drive system and the braking energy recovery system. In addition of the design, this paper explained the working principle of the two systems. The drive system in this paper adopted the high speed transmission scheme, and uses a combination of variable pump and constant displacement motor. The angle of the swash-plate is variable, change its value to control the flow of the variable pump, and then control the speed of the full-hydraulic loader. As to the braking energy recovery system, the braking energy is recycled by accumulator and then used to other mechanisms. This system can reduce fuel consumption and increase loading efficiency.(2) The main hydraulic components of the drive system and the braking energy recovery system were matched. Firstly, determined the working pressure of the system; secondly, based on flow continuity equation and the resistances of different work mode, selected the type of the variable pump and constant displacement motor; lastly, based on static balancing equation, determined the parameters of accumulator, braking energy recovery pump and other hydraulic valves.(3) Modeling and simulating the hydraulic drive system and the braking energy recovery system. In this part, variable displacement mechanism model of variable pump, pump-control-motor model and motor-control- velocity model in the hydraulic drive system were built. In addition, braking energy recovery and release model in the braking energy recovery system was built. Then used Matlab/Simulink to simulate and research. While simulating, kept the engine speed constant, and changed the angle of the swash-plate to control the flow of the variable pump, then simulated under V cyclic operation. By the simulation, the changing curve of pressure, torque and energy power of the hydraulic drive system and the changing curve of pressure and volume of accumulator were drawn. All of the data are in according with the expected targets. In addition, the recovery of the braking energy recovery system is 38.8%.