STUDY ON TORSIONAL RIGIDITY OF A NOVEL BALL SCREW TRANSMISSION BY FINITE ELEMENT METHOD

摘要

A certain key project starves for a most advanced swaying executor, swaying mechanism, which should produce torque up to 280N · m with its unit weight, and sets strict demands on such indexes as system torsional rigidity, rotate speed, scope of swaying angle, size, deadweight, etc. According to original complex planetary gearing plan, a swaying mechanism was developed, being far inferior to requirement. On the basis of analyzing existing dozens of reductors, a new structure that achieves swaying with ball guide screw driven by reciprocating piston rod of high-pressure oil cylinder was put forward. Having analyzed and compared more than ten novel plans, a structural model of straight-rotary ball pair was proposed, an ideal plan of identical radius ball-return was found, and the structural optimal design of the novel swaying mechanism was finished. Both computer simulation and prototype experiment make clear that each performance index of the novel swaying mechanism is very good; consequently this engineering problem is resolved triumphantly. In order to ensure good load performance, high efficiency, stationary transmission, and great output torque, a special structure is adopted, which is composed of the ball straight-rotary pair with multi-start and big helical lift angle, the ball splinder pair, the ball unload pair, the piston hydraulic cylinder, etc. The new swaying mechanism not only can be used to drive the wings of airplanes, space shuttles and rockets, and so on, and to control the sway of radars, and to run the doors and windows of ships and naval vessels, but also may be widely applied to varied occasions which need swaying mechanisms. System torsional rigidity is an important design index, having important influence on operating performance of the novel swaying mechanism; therefore, this paper emphasizes the study on calculation of system torsional rigidity. This paper firstly introduces working principle and structural features of the novel ball screw transmission. Then uses commercial CAD and FEM softwares, SolidWorks2001 and COSMOS/Works, fulfils deformation analytical computation for such three key parts as driveshaft, fixed guiding sleeve and straight-rotary sleeve. Next, sum up each term of torsional rigidity. Finally, makes a conclusion that the system torsional rigidity of the novel ball screw transmission satisfies the designing demand.