A calculation method for friction coefficient and meshing efficiency of plastic line gear pair under dry friction conditions

A calculation method for the friction coefficient and meshing efficiency of plastic line gear(LG)pair under dry friction conditions was studied theoretically and experimentally,taking a polyoxymethylene parallel line gear pair(POM PLGP)as an example.Firstly,the geometric and mechanical models of PLGP were built by considering the effects of misalignment and loaded deformation under the actual operating condition.Then,the friction coefficient of POM specimens was obtained via the ball-on-disk experiment,of which the value varies between 0.35 and 0.45 under the experimental conditions.The calculation formula for the friction coefficient of POM LG pair was obtained by fitting the friction coefficient of the POM specimens,and the meshing efficiency of POM LG pair was calculated based on the calculation formula for friction coefficient and the meshing efficiency calculation approach.Finally,the meshing efficiency of POM PLGP specimens was measured using a homemade gear meshing efficiency test rig.The experimental results validated the feasibility of the proposed calculation method for the friction coefficient and meshing efficiency of the plastic LG pair.This study provides a method for the calculation of the friction coefficient and meshing efficiency of plastic gear pairs under dry friction conditions.It also provides the basis for the wear calculation of plastic LG pair under dry friction conditions.

Dynamics of lubricated spiral bevel gears under different contact paths

To assess the meshing quality of spiral bevel gears,the static meshing characteristics are usually checked under different contact paths to simulate the deviation in the footprint from the design point to the heel or toe of the gear flank caused by the assembly error of two gear axes.However,the effect of the contact path on gear dynamics under lubricated conditions has not been reported.In addition,most studies regarding spiral bevel gears disregard the lubricated condition because of the complicated solutions of mixed elastohydrodynamic lubrication(EHL).Hence,an analytical friction model with a highly efficient solution,whose friction coefficient and film thickness predictions agree well with the results from a well-validated mixed EHL model for spiral bevel gears,is established in the present study to facilitate the study of the dynamics of lubricated spiral bevel gears.The obtained results reveal the significant effect of the contact path on the dynamic response and meshing efficiency of gear systems.Finally,a comparison of the numerical transmission efficiency under different contact paths with experimental measurements indicates good agreement.