【作者】 王允；

【导师】 荆宝德；

【作者基本信息】 吉林大学 ， 机械电子工程， 2008， 硕士

【摘要】 液压系统在工业领域的应用随着现代化科技的进步和液压系统本身的制造技术的提高而越来越多,尤其是在工程机械这一行业,液压系统的应用更是越来越多技术化,多科技化。装载机已经成为工业、建筑业、矿业等不可缺少的得力助手。随着经济的发展,科技水平的提高,装载机的种类和用途越来越广。而在设计和改进装载机时也不可避免的会遇到一些急需解决的问题,很多的技术问题等待着我们去解决。本课题研究的对象就是解决在856Ⅲ装载机的改进系统中遇到的一个问题,那就是如何解决装载机卸料速度慢的问题。提高工作效率,减少劳动时间是我们的追求目标。主要的研究内容就是了解装载机的基本结构和主要的液压系统部分;分析新型装载机卸料速度慢的原因;提出解决问题的几种方案,并对方案进行分析筛选确定合适的方案;设计快速卸料系统,重点设计系统中需要的二位三通换向阀;对改进后的系统建模并用AEMSim软件进行系统仿真;进行相关的试验得到实验数据和试验曲线,分析试验结果,验证该改进后的系统的可行性。更多还原

【Abstract】 In this paper, the object of study is LIUGONG product 856Ⅲwheel loader. The sum of time of the loader bucket lifting, unloading,and return to material stack is the smaller the better with not only this model, but also other models. So it will save a lot of time and improve work efficiency.Fast unloading system can be used not only in the eight-link loader, can also be used in other wheel loader.Because mechanical hydraulic system are universal in a certain sense. Fast unloading system can be applied to other engineering machinery, such as bulldozers, bucket before Boom also need the rapid decline with using similar principles. It can improve work efficiency greatly.In this article, I introduct the development of the loader, development trends briefly,and note the major part hydraulic system of the Loader. Loader has six-bar linkage and eight -bar linkage two agencies working device, and that there are positive and inversion two different connectivity forms for devices. The common link is six inversion and eight positive these two institutions. And now the target of paper is 856Ⅲeight positive loader. This loader is a bit slowly when unloading.So the task of the paper is to solute this issue.The paper analysis the reasons for the 856Ⅲeight Loader unloading with the slow speed.The reason is that the hydraulic system uses the original six-bar reversal agencies Loader hydraulic system,856Ⅲloader uses eight positive agencies.It is to fight oil into the big cavity of the cylinder, when the bucket discharges, and the original six-bar reversal body cavity size loader when unloading oil from the contrary, but work pump and valve distribution linkage are the same as the six linkage.So eight linkage the large cavity enter the oil is smaller than the six-bar discharge to fight small cavity oil Relatively speaking reduced volume, when the loader bucket cylinder unloading ,at the same time the oil enter the big cavity to achieve maximum pressure lengthy, and the corresponding unloading speed is slower.We need design quick unloading system to solute the problem of slow, with the principle of the differential loop.We use the two-directional and the three openings hydraulic control directional control valve and user-friendly back-pressure valve. We will link the hydraulic control directional control valve cylinder size between the big and the small cavity of the bucket cylinder to connect the two cavities. That is, bucket cylinder can fight the hydraulic oil of the small cavity into the big cavity, to achieve the purpose of rapid discharge when discharges. A large number of formula applications in the analysis of the valve.Loader hydraulic system is the cylinder valve control system.We make the mathematical modeling for the system using the control principle, List reversing valve spool valve flow of the linear equation, hydraulic cylinder flow continuity equation, calculated the hydraulic cylinder of the balance equation and the transfer function, etc. We use theoretical analysis and calculation to the system, but also use software AMESim to simulate system.AMESim offers a time-domain simulation modeling environment, and establishments a new model components using the models have been used, constructs the actual prototype of the Optimization Design needs,with the easily identifiable standard ISO and multi-port diagram simple intuitive icons. The user can establishment complex system and the particular application examples friendly, modify model and simulation parameters, steady-state and dynamic simulation, analysis and mapping of simulation results.The operation is very convenient with the friendly interface. We use software components to Establish the structure of the whole system model, set the parameters of components in the model, and the actual application of numerical similar. We can use 3-D simulation of the software to see the model plans. RUN command of the software can simulate all kinds of curves we want. We can know the design system is improved with the design requirements or not by simulation both before and after improving system using AMESim, and comparing the two simulation results.Making comprehensive hydraulic test experiments to the two-directional three openings valve can test its Orifice pressure loss,oil-flow performance and dynamic characteristics by connecting valves’three mouthes to the test bed pressure sensors and flow sensors respectively, and setting the pilot pressure and the flow of the pump. It is necessary to test the valve open time and the close time because of the reduction valve spring . At last,we can get the result that the calve meet the actual needs.We install the two-directional and the three openings hydraulic control directional control valve in hydraulic system of the loader connecting between the big cavity and the small cavity of the bucket cylinder, at the same time install the 1.0 MPa back-pressure valve without the need fast unloading for user-friendly discharging slowly in the complete machine test and connect the big and small cavity of the bucket cylinder pressure sensors of the dynamic measurement instrument. Operating Loader to move Boom upgrade , the bucket unloading, or bucket and Boom decline several times,we can know the piston of the bucket cylinder extending and indentation only in the discharge and recovery the bucket. At this time we can get the relationship between pressure of the big cavity and the small cavity of the bucket cylinder and the time can be measured by dynamic measuring instrument. We can draw a conclusion by analysis the experimental results,and compare the experimental results to the actual working of the system without improvement to verify the feasibility of the improving system.更多还原