Benedict and Kelley studied the instantaneous contact friction coefficient of spur gears through the gear test bench, and studied the viscosity of different lubricating oils through a large number of tests η 0. The variation of friction coefficient under different loads, such as entrainment speed UE, relative sliding speed vs, and W, is fitted to the following empirical formula of friction coefficient:
Xu and Kahraman studied the friction loss and transmission efficiency of spiral bevel gears based on the Line Contact EHL model In order to improve the efficiency of solving the friction coefficient, Xu and Kahraman calculate a large number of friction coefficients and use the multiple linear regression method to give the fitting formula of the meshing friction coefficient of spiral bevel gear. The formula contains more key parameters than the friction coefficient formula of Benedict and Kelley, that is, the maximum Hertz contact pressure pH Equivalent curvature radius Rx, slip roll ratio SRR and lubricating oil viscosity in the direction of the minor axis of the contact ellipse η 0. Entrainment speed UE, relative sliding speed vs and root mean square roughness σ The expression is as follows:
Where s RR = 2vs / (UE COS) θ e)， f(S S R, ph, η 0 σ) Expressed as:
Where the regression coefficients b1~b9 are listed in the table.
