Multi Body Dynamic Analysis Of The Slewing Ring Of Hydraulic Excavator

Hydraulic excavator is an important engineering machinery, it is widely used in transportation, energy development, urban construction, national defense construction and other engineering construction. And for excavator important two parts, slewing bearing can be used to carry the load of the upper part of the body and provides rotary motion for the car body, working device is the chief executive that excavator to achieve the grasping movements. so,the related research to the two parts is very necessary.This paper take the hydraulic excavator as the background, based on the method of multi body dynamics theory, the Hertz contact theory, virtual prototyping technology theory, establish the 3D model of slewing bearing and virtual prototype model of excavator system, by multi body system model of hydraulic excavator include slewing bearing, working device, etc., get the kinematics and dynamics theory and dynamic simulation of analysis. Main contents include:(1) A single row four point contact ball type slewing ring dynamic model is established, and the dynamic simulation analysis is carried out. By comparing the simulation results and the theoretical calculation results of the transmission ratio and the angular velocity of the outer ring, find the relative error is very small, which verifies the correctness of the model. Under the action of three different load include axial force alone, overturning moment alone, axial force and overturning moment together, get static simulation of slewing ring, came to a conclusion that the contact force of numerical and theoretical values are compared, the error is small.(2) The gear meshing force that only under axial loading force in the dynamic response of different speed were analyzed. The results show that with the increasing of speed, the amplitude of the meshing force decreases, while the average value increases, the greater the speed, the greater the stress of gear meshing, but vibration instead more and more small. Comparing with contact for the rolling body in four different rolling, found a scroll body in four roller contact way force into a diagonal relationship; On different rolling body contact force in a same rolling are compared, found a scroll body contact force distribution rule, from by contact force the biggest roll body began to extend to both sides, contact force is more and more small with a roller; Through the analysis of the centroid of outer ring in slewing plane displacement to verify the affected by the small gear and outer ring centroid along the radial direction has small fluctuations, resulting in axial force under the rolling contact force distribution is not uniform.(3) Establish hydraulic excavator virtual prototype, kinematics simulation of the working device, through the bucket tooth tip displacement trajectories, obtained excavator digging range and limit dimensions, including maximum digging height, maximum discharge height, maximum extension distance, maximum digging depth; Comparing with composite mining and sequence mining, found that compound mining in a shorter time and improve the work efficiency of excavator, and make full use of the power of the engine and oil pump.(4) Established the rotary excavator system which considers slewing ring, and taked dynamic simulation analysis, and compare with working device dynamic analysis that does not take into account the slewing bearing, it can be seen that slewing bearing for the working device, the hinge force influence is very big, the hinge force curves appear obvious fluctuations. The working device for slewing gear meshing force, rolling contact force, the outer ring of the centroid change is particularly important. Therefore, the working device and the rotary support are a coupled system, which can not be studied separately.