Abstract: A new model of involute spur gear of form inking roller of offset press that contains rotational and axial velocities is proposed to study the lubrication behaviour. The model is based on the finite line-contact mixed Elastohydrodynamic Lubrication (EHL) formulas, which is capable of handling the numerical simulation gear lubrication with different rough surface patterns. On the basis of geometric analysis, the governing equations are built up with the help of the mixed EHL theory. Then, the efficient multigrid method is applied to solve the governing equations after the nondimensionalization and discretization. As results, the numerical simulations can accurately predict the film pressure distribution, the film thickness distribution, the compositive friction coefficient and the asperity load ratio. It is shown that the axial velocity of spur gear intensifies the stress concentration on the gear tip. Different rough surface patterns obviously influence the lubrication behaviour of the spur gear. The film pressure of longitudinally oriented surface reaches a maximum of 593.1 MPa under the condition of non-axial velocity. The rise of the film pressure of longitudinally oriented surface reaches a minimum of 188.7 MPa only under the condition that the axial velocity is not zero. It is also shown that both the axial velocity and the rough surface pattern obviously influence the friction coefficient.

Key words: machine design, rough surface pattern, mixed EHL, spur gear, two-dimensional velocities, finite line-contact