Design Methods And Dynamic Analysis Of Planetary Gear Transmission Drive With Meshing Beyond Pitch Point

Because of the split-power and internal-meshing structure, planetary gear trains are better thanfixed axis gear trains in many ways, such as lighter quality, smaller volume, bigger transmission ratio,higher load capability and transmission efficiency etc. So it is widely used in industry, such asaeronautics and astronautics, ship and engineering machinery etc. For the gear drive with meshingbeyond pitch point, its actual line of action is located in one side of the pitch point. It can improve thevibration characteristics of the gear pair by unchanging the direction of friction. So this paper’spurpose is to design and dynamic analysis of planetary gear transmission drive with meshing beyondpitch point.Two important meshing characteristics of gear drive with meshing beyond pitch point areanalyzed, the decision conditions of gear drive with meshing beyond pitch point and coefficient ofbeyond pitch point. According to the analysis, it is found that internal-meshing pair is more easy toimplement the structure of drive with meshing beyond pitch point. And an easy way to implement thestructure of drive with meshing beyond pitch point is to use different pressure angles of referencecircle. Relationship between feasible region of modification coefficient and some gear parameters wasstudied, such as number of teeth, pressure angles of reference circle and addendum coefficient. Inplanetary gear transmission system, reducing planet wheel’s number of teeth appropriately isbeneficial to implement the structure of drive with meshing before pitch point for external-meshingpair and drive with meshing behind pitch point for internal-meshing pair. It is more reasonable to usethe structure of drive with meshing behind pitch point than the structure of drive with meshing beforepitch point for the internal-meshing pair, because the major factor to limit the strength of NGWplanetary gear transmission system is contact strength of its external-meshing pair.In order to make calculation formula suitable to strength calculation of gear drive with meshingbeyond pitch point, formula of strength calculation in related standard was modified. It is pointed thatcontact stress calculation point should be the point of maximum contact stress in single tooth meshingarea, and the rule of calculation point is studied. The mean friction coefficient of scuffing strength isgot by using simplified integration, and calculation formula of contact ratio coefficient is reduced.Based on the revised formula of strength calculation, module of strength calculation is developed, strength safety coefficient of gear drive with meshing beyond pitch point is analyzed, and itsrelationship with coefficient of beyond pitch point is established. It is found that too big coefficient ofbeyond pitch point reduces the strength of gear, especially bending and scuffing strength.Based on the meshing characteristic of gear drive with meshing beyond pitch point, planetarygear transmission drive with meshing beyond pitch point is optimization designed by using MATLABoptimization toolbox. The optimization design module of planetary gear transmission drive withmeshing beyond pitch point is developed, and parameters of system are got.Dynamic model and dynamic equation of planetary gear transmission drive with meshing beyondpitch point are built, this model take into account friction of tooth surface. After displacementcancellation of rigid body and dimensionless, inherent characteristics of this system is studied.Dynamic response and load coefficient are got by solving dynamic equation with Runge-Kuttanumerical integral. Module of dynamic analysis is developed, it is confirmed that the structure ofdrive with meshing beyond pitch point could improve load characteristic of system.