Design And Reliability Study Of Rope-gripper Driving Mechanism Of Knotter Driven By Two Toothed Discs With Same Tooth Direction

Aiming at the rope-gripping failure of the rope gripper driving mechanism in the knotter driven by double fluted disc,this paper analyzes the failure position and failure reason of the rope-gripping,and puts forward a knotter driven by double toothed discs with same tooth direction.Based on the rope-gripping principle of the rope gripper driving mechanism of the knotter driven by double fluted disc,the kinematics design and structure optimization of the rope gripper driving mechanism of the knotter driven by double toothed discs with same tooth direction are carried out to improve the stress characteristics of the transmission parts of the the rope gripper driving mechanism,and it is expected to improve the reliability of the structure and movement of the knotter.The main research contents of this paper are as follows:(1)By analyzing the rope-gripping failure of the knotter driven by double fluted disc,it is found that the main cause of rope-gripping failure is the deviation of rope-gripping point on the rope gripper disc caused by transmission phase lag in the transmission process of worm pair;The reasons for the transmission phase lag of worm pair include: the excessive helical angle of worm transmission helical gear leads to large nonlinear force in the transmission process of worm pair,which intensifies the wear of worm pair and leads to the phase lag of worm transmission;At the same time,the large helical angle of helical gear makes the worm shaft bear large radial force and fatigue bending in the transmission process,which eventually leads to the abnormal transmission of worm pair.(2)Based on the kinematic design of knotter driven by double toothed discs with same tooth direction,the optimization scheme of the twine disc drive mechanism is determined,and the transmission components in the rope gripper driving mechanism are optimized by using Geartrax and KISSsoft.The optimized structure mainly includes bevel gear pair with 70°intersecting shaft and right-hand worm pair with 72° staggered shaft.In the design of right-hand worm transmission,the helical gear helix angle is greatly reduced compared with the original transmission helix angle,and the worm and worm shaft adopt left-hand thread connection design,which effectively improves the transmission reliability of worm pair.At the same time,the spatial parameters of the support of the knotter driven by double toothed discs with same tooth direction are analyzed,and the spatial angle position relationship of each shaft hole on the support is determined.(3)The virtual prototype models of the knotter driven by double toothed discs with same tooth direction and the original double tooth disc knotter are established by Solid Works.The kinematics simulation analysis of the virtual prototype models of the two kinds of knotters is carried out by using ADAMS.The stress conditions of the main transmission components before and after the structural optimization of the rope gripper driving mechanism are compared and analyzed.According to the stress simulation results,the stress characteristics and transmission reliability of the rope gripper driving mechanism designed in this paper are evaluated.(4)Using the flexible body data transmission interface between ANSYS and Adams,the flexible models of worm gear,rope-gripping bevel gear and worm shaft in the rope gripper driving mechanism are established in ADAMS,and the rigid flexible coupling dynamic simulation analysis is carried out.The simulation results are used as the load data conditions in ncode Design Life fatigue analysis.Combined with fatigue theory and material S-N curve,the fatigue life of easy fatigue parts is predicted,and the fatigue damage distribution and fatigue life distribution of worm gear,rope-gripping bevel gear and worm are obtained.(5)Considering the complex geometric parameters of the transmission parts of the rope gripper driving mechanism and the complex spatial parameters of the knotter support,the prototype of the knotter driven by double toothed discs with same direction is trial manufactured by precision casting method,and the casting accuracy is tested by 3D mechanism scanner.The casting accuracy of the cast parts meets the design and transmission requirements.The feasibility and reliability of the designed rope gripper driving mechanism are tested by using the continuous knotting test-bed.The test results show that the designed rope gripper driving mechanism meets the requirements,and the success rate of rope-gripping is 100%.