The numerical analysis model for mixed lubrication of filtering reducer tooth was built considering the tooth contact geometry

normal load of meshing point

tooth parameters

real surface roughness

rheological behavior of lubricant. A completely numerical solution of mixed lubrication analysis in tooth contact surface was achieved by solving the Reynolds equations and elastic deformation equations using compound iteration method and fast Fourier transformation (FFT) method respectively. The pressure and average film thickness were obtained at engaging-in point

engaging-out point and pitch point of filtering reducer

and the effects of speed on the average film thickness and contact area ratio in tooth contact surface were also obtained. The results show that the pressure distribution along the tooth width direction is not equal at engaging-in point

engaging-out point and pitch point

and pressures on both sides are higher; the variation of pressure is smaller on both sides and the average film thickness is greater at engaging-in point. When the tooth contact surface is rough

with the decrease of speed of filtering reducer

the average film thickness at engaging-in point

engaging-out point and pitch point is decreased

and the contact area ratio increases

leading to poor lubrication. Besides

the average film thickness of meshing points of rough tooth contact surface is less than that of smooth tooth contact surface under the same conditions.