Analysis On Digging Force And Mechanism Optimization For Large-sized Hydraulic Excavator Working Attachment

Large-sized hydraulic excavator is a large capacity of earthwork construction equipment. It is widely used for mining and large construction projects. Because of the variability of mining conditions in the process of the operation and that cause the force acted on working attachment in complex stress, which affcct the overall performance of the machine. For this problem, taking70T large-sized hydraulic excavator as prototype, this paper established the virtual prototype model of excavator, the changes of digging force and force acted on hinged joints for working attachment in the process of operation were analyzed, and the mechanism optimization was studied, so that the comprehensive operating performance can been imporved.The main works are as follows:The kinematics model of working attachment for excavator was established by using D-H method, the mathematical model for theoretical digging force of hydraulic cylinder and theoretical digging force of whole machine were established based on the kinematics model.The dynamic simulation model for working attachment was built by using the software of Inventor and ADAMS. The changing characteristics of the theoretical digging force of the whole machine in the mining process and the ratio of the limiting factors in mining area were analyzed, which found the posture of which working attachment has the largest digging force. Next, the arm and bucket digging actions were simulated to obtain the hinge force, which provided reference for further optimization of the structure for hinged joints.Taking the theory digging force and the lifting force in the main excavation area of the bucket and arm as the optimization goal, the positions of the hinge points was designed. The results show that the mechanical properties of the excavator working attachment and the stress of the hinge point can be improved by adjusting the position of the hinge point in a small scale. At the same time, the working scale of the excavator was enlarged.Through the test of cylinder pressure and the displacement data of piston in the real excavator digging process, which were used to get the rod force curve, by which the bucket prong digging resistance was calculated indirectly, the accuracy of the simulation and calculation model was verified.