| Sprag clutch is a one-way overrunning clutch. Becauses of good carrying capacity, compactstructure and easy manufacturing process, the sprag clutch is widely used in transmission systemof helicopter. As a most important part in transmission system, the properties of the clutch directlyimpact the whole helicopter. Therefore, the research on the design method of sprag clutch hasvery important engineering significance.In this paper, comprehensive studies on sprag clutch are performed. The relevantachievements can be divided into the following five parts.(1) Force analysis of clutch components in transmission mode are conducted. The Contactstresses between sprags and races, the hoop stress of inner ring and outer ring are calculated. Theinfluencing factors of radial deformation are discussed and the corresponding formulas areobtained. Conditions of selflocking are obtained based on the force analysis. With theconsideration of centrifugal force and spring force, the force analysis of sprag in overrunningmode is conducted.(2) The detailed structural design and calculation is conducted. Method of calculation ofsprag contact angles are obtained. Effects of sprag structural parameters on mechanical propertiesof the clutch are analyzed.(3)Contact properties between sprags and races are simulated in Ansys Workbench, then theresults of simulation are compared with the theoretical results. Effects of coefficient of friction oncontact properties of the clutch are discussed. At last, the shape of sprag is improved based on thefinite element simulation results.(4) A dynamical simulation model is bulit based on ADAMS. Through reasonable setting ofsimulation parameters, the engagement process of clutch is simulated, and the results are analyzed.Effects of taper error of innerrace on the engagement process are analyzed.(5) Calculation software is designed by MATLAB GUI, it can be used to calculate thestructural sizes and stresses,deformation of the sprag clutch. |
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