Structure Design And Anlysis Of Slotted Belleville Spring For Ultrasonic Motor

As one of the pressure parts with nonlinear stiffness characteristic,the belleville spring has already been widely used in our production.Due to its compact structure,great bearing capacity and flexible design,the belleville spring can be used to meet various engineering requirements.Now,the belleville spring has been used for preloading in some ultrasonic motors,but in some small size series,higher accurate calculation model and stricter requirement for structure design are need because these motors can be seriously disturbed by small fluctuation of the preload.In this paper,the slotted belleville spring is used for preloading in the samll size series of ultrasonic motors.Based on the axisymmetric bending theory of rotating shell,the calculation model for slotted belleville spring was established under the condition of axisymmetric loading and sliding support.An experiment was designed to verify this model.The validity was comfirmed by its result and the relative error was within ±2.4%.The higher precision of the model was proved comparing with the traditional design formulas.Based on the theory of bending cantilever beam with large deformation,the calculation model was built for the cantilever with gradual change section and the validity was verified by the finite element method.With the calculation model of belleville spring and cantilever beam of various section,a calculation method was presented for slotted belleville spring.A higner precision of this model was showed with the comparision of the FEM result and the relative error was within ±3.5% comparing with the experimental result.Based on the structure of the experimental belleville spring,single parameter influence on the stiffness characteristic was studied.To study the quasi zero stiffness characteristic of slotted belleville spring,a parameter-sensitivity analysis testing flow was designed.The radio of free high and thickness was proved to have a great influence on the zero stiffness characteristic of slotted belleville spring and the optimal ratio range was 1.5 to 1.8.Based on the result of sensitivity analysis,a design process was presented and a design software was built by Matlab.