Study on the meshing stiffness of plastic helical gear meshing with metal worm via point-contact

Time-varying meshing stiffness is the main internal excitation source for gear dynamic responses. A calculation method for meshing stiffness of point-contact transmission pairs is proposed to analysis the dynamic responses of the plastic helical gear metal worm drive. Based on the curvilinear motion trajectories and the contact ellipse changes of helical gear worm drive, a method of equivalent area rectangle is introduced to convert the contact ellipse into contact line, and the relationship between the contact line and the worm angle is established. The meshing stiffness of plastic helical gear metal worm drive is calculated and compared with the finite element method (FEM) to verify its accuracy. The results show that the meshing stiffness of plastic helical gear metal worm drive is affected by the meshing impact, and the time-varying meshing stiffness value of double-tooth meshing will be close to or even lower than that of single-tooth meshing. In the plastic helical gear metal worm drive, there is no stable stiffness value whether it is single-tooth meshing or double-tooth meshing. The single-tooth meshing stiffness has an upward trend under the influence of the pressure angle. The calculation results of theoretical model are basically consistent with the FEM results, but the theoretical model cannot fully reflect the stiffness change during meshing impact.