Abstract: The instantaneous thermal elastohydrodynamic lub- rication (EHL) of the mesh of a pair of helical gears is simulated by the pseudo-steady state thermal EHL of two tapered rollers in opposite orientation approximately. The behavior of pseudo-steady state thermal EHL is investigated by multilevel method and sequential sweeping method. It is found from the numerical results that, firstly, pressure, film thickness, temperature of the film and gears surfaces are different at different positions on the meshing line of the helical gears, especially the distribution of temperature. The lowest temperature rise is nearly zero, however the highest can exceed 100 K in the contact area. That is because that the distributions of pressure and film thickness depend strongly on the distribution of the equivalent radius in the direction of the roller length, and the distribution of temperature depends strongly on the local slide/roll ratio in the direction of the roller length. Secondly, the high pressures and temperatures in the ends can be decreased by the end modifications, but the pressure and temperature there are still higher than those in the middle, and the film thicknesses there are smaller than that in the middle. The place in which the pressure and temperature is high and the film is thin is corresponding to the place where pitting and scoring are most likely to occur.

Key words: Helical gears, Opposite orientation, Pseudo-steady state, Tapered rollers, Thermal elastohydrodynamic lubrication