Symmetry-Restoring Profile Modification of Polyoxymethylene Gears Based on Cumulative Deformation Energy

During the meshing process of plastic gears, inhomogeneous thermal deformation is prone to occur due to the coupling effect of frictional heat generation and material thermal sensitivity, leading to contact misalignment on tooth surfaces. Traditional modification designs mostly rely on empirical approaches or merely compensate for static elastic deformation, which cannot adequately address thermo-mechanical interactions. In this paper, an active modification method based on the identification of thermal deformation regions is proposed. First, a thermo-structural coupling finite element model of polyoxymethylene (POM) gears is established, taking into account the temperature-dependent modulus. The steady-state temperature field is obtained through ANSYS 2024 R1 simulations, and its accuracy is verified against experimental measurements. Subsequently, the thermal deformation distribution is acquired by coupling the structural field. The cumulative deformation energy function is introduced, and the modification length is objectively determined as L = 0.35 mm by adopting the extreme point of the second derivative of the normalized cumulative energy. Three modification strategies, namely linear modification, Walker curve modification, and Mingchuan curve modification, are designed. Simulation results demonstrate that all three strategies effectively reduce the thermal deformation, steady-state temperature, and contact pressure of the gears, among which the Walker curve modification exhibits the best performance. After modification, the maximum thermal deformation is reduced by 44.14%, the maximum contact pressure by 16.2%, and the maximum steady-state temperature by 9.5%. The proposed method transforms thermal deformation from a “passive response” into an “active design input”, verifies the feasibility of thermally driven modification, and thereby establishes a quantifiable thermally adaptive modification approach for plastic gears.