| Title of Thesis: Research on the Rotating Performance And Optimization Designfor Backhoe Device of Backhoe Loader Specialty: Mechanical Design and Theory Supervisor: prof. Zhang ZiDa The Backhoe Loader is a sort of multipurpose construction machinery, equipped with backhoe device and loader device, based on a special or general chassis. It is made up of body, backhoe device and loader device, its function containing shoveling, excavating and bulldozing, and is a kind of on-the-spot construction machine with extensive use and stronger adaptability.Rotation mechanism in the backhoe device is one of the important organizations of Backhoe Loader. Rotation time, energy consumption and the caloric given up by hydraulic system etc. occupy greater proportion to those in the whole work circulation of excavate system. While Rotating, especially fully loaded, if the dynamic performance of Rotation mechanism is not good, the arm will swing seriously and drive the heavy object to rock, the stability will be bad, the security will be influenced. Deeply studying rotation mechanism is very important to know the dynamic performance during rotating, solve the problem that exist during Backhoe Loader works, improve device's design, boost productivity and function utilization ratio and improve condition of work, etc. At present, the Backhoe Loaders are designed and manufactured according to the analogy and drawing at home, or by connecting ready-made machines to tractor. Because this designing means lacks the instructing of modern design theory and method, there is greater blindness and a large number of hard work often be needed to gain a group of satisfactory schemes. In this way, not only design efficiency is very low, but also it is very difficult to receive the best scheme with better economy and dependability. And at present the research on rotation mechanism in the backhoe device still blank basically at home. Kinematics analysis to rotating is the foundation of the whole research work. Now WZ25-20 is regarded as an example, its backhoe device consists of moving arm, pole, bucket, guiding organization and rotation mechanism. Two hydraulic cylinders which can swing, supply power for rotating, drive moving arm rotate about shaft from side to side and make backhoe device rotate, excavate and unload in the range. The distance between the joint of the hydraulic cylinder and the center of rotation shaft, the turning radius , the angle andinitially mounting hydraulic cylinders are main independent parameter of the organization. According to the geometry relation of the mechanism and Kinematics knowledge, the kinematics mathematics model can be set up on the basis of neglecting starting stage. We can program, calculate and simulate by using MATLAB which generally be used for large-scale number value calculating and simulation. It is the key site on which piston rod or its extension line passes the rotation center and which is called " extreme site ". During rotating after this site, the direction of flexing of one of the two piston rods will change, for example, piston-rod which extended before would begin to shrink. This change causes rotating speedup, and speed value changes in evidence, it prove angle acceleration exist. At this moment or later braked, the backhoe device will be lashed because of very great rotation inertia moments. The relation between rotation angle, or speed, or acceleration and the journey of flexing of the piston-rods, or rotating time.On the basis of kinematics analysis, in addition to consideration of the rotation inertia, the dynamics model can be set up. The rotation inertia of irregular geometry parts is difficult to solve, but CATIA which is used for three-dimensional sculpting and analysis can help us to solve easily this problem. The dynamic performance includes the biggest rotation angle, energy consumption, lashing while braking, and rotation time spent. Lashing while braking is the main factor. The value of the angle acceleration is larger, inertia-momen...
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