Abstract:

Objective In calculating the wear of the kinematic pair in the spatial linkage weft insertion mechanism with clearance, the role and change process of the clearance in the wear process of the hinge clearance cannot be accurately expressed if simply considering the clearance of the flexible hinge or simply consider the flexible deformation of the rod. Therefore, in order to improve the calculation accuracy of clearance impact wear prediction, the influence of various factors on the system motion output should be considered comprehensively, so as to meet the requirements of high speed, light weight and heavy load of the mechanism and improve the operation accuracy of the mechanism.

Method Firstly, combined with the Lankarani-Nikravesh and Bai model, the variable stiffness and damping discontinuous contact impact force model was established. The improved Coulomb friction model was used to describe the friction between the shaft pin and the sleeve of the rotating hinge with clearance mechanism, and the system dynamics was modeled by Lagrange method. Secondly, the spatial linkage was selected as flexible object, and the rigid-flexible coupling dynamics simulation of the spatial linkage weft insertion mechanism was carried out by combining Ansys and Adams methods. Finally, the dynamic simulation response results of the sys-tem were combined with the Archard model.

Results In the rigid-flexible coupling system, the maximum stress of the spatial linkage was distributed near the rotating pair, and the maximum deformation distribution of the unit displacement was also at the hinge point of the two support frames. As the clearance was increased to r = 0.5 mm, the component flexibility failed to effectively alleviate the speed fluctuation caused by the clearance impact during the process of the rapier head sliding out of the shuttle, while in the weft handover process, the component flexibility effectively slowed down the high-frequency fluctuation of the rapier head acceleration. When the clearance r = 0.15 mm, the relative sliding distance showed a higher value in the two working states of weft handover and rapier head return. When the clearance was increasd to r = 0.5 mm, its maximum value did not increase significantly compared with the clearance r = 0.15 mm, although the sliding distance fluctuates greatly in the whole period. When the clearance r=0.15 mm, the maximum wear depth of the motion pair appeared in the vicinity of the spindle rotation angle, this was the same as that when the clearance r=0.01 mm. When the clearance was increased to r=0.5 mm, a large number of wear occurred in a wear calculation cycle with a much increased frequency. In such a case, the wear range was no longer concentrated on the fixed area, while the maximum wear depth did not show significant increase. With the increase of the clearance of the kinematic pair, the maximum value of the clearance impact force also was increased, and the wear depth was increased with the increase of the impact force under different clearance conditions.

Conclusion Compared with the pure rigid body mechanism, the flexibility of the component has a greater influence on the acceleration of the rapier head, which can prevent the yarn from breaking during the handover of the rapier head to a certain extent. In the high speed running process of the spatial linkage weft insertion mechanism, the relative sliding of the joint components with clearance in the impact process mainly occurs in the 'fast forward' and 'quick return' stages of the rapier head. Under the condition of clearance r = 0.15 mm, the maximum amplitude of the acceleration oscillation of the rapier head is reduced by 53.2%. When the clearance rises to r = 0.5 mm, although the wear range increases significantly, the wear depth of the clearance does not increase significantly.

Key words: weft insertion mechanism, contact impact force model, Coulomb frictional force model, rigid-flexible coupling wear, apatial linkage