Key Takeaways & Executive Findings
- •• An improved 3D anisotropic fractal model integrates tooth surface roughness and elastohydrodynamic lubrication for planetary gear meshing analysis. • Asperity contact transforms the lubrication regime from EHL to mixed lubrication, reducing oil film stiffness. • Ring-planet gears exhibit greater sensitivity to surface roughness than sun-planet gears, affecting meshing stiffness. • Torque is the most influential parameter on meshing characteristics compared to roughness, speed, and viscosity.
Abstract
The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state. The coupling effect of tooth surface roughness and lubrication on meshing characteristics of planetary gear is studied. An improved three-dimensional (3D) anisotropic tooth surface roughness fractal model is proposed based on the experimental parameters. Considering asperity contact and elastohydrodynamic lubrication (EHL), the contact load and flexibility deformation of the tooth surface are derived, and the deformation compatibility equation of the 3D loaded tooth contact analysis (3D-LTCA) method is improved. The asperity of the tooth surface changes the system from EHL to mixed lubrication and reduces the stiffness of the oil film. Compared with the sun-planet gear, the asperity has a greater effect on the meshing characteristics of the ring-planet gear. Compared with the proposed method, the comprehensive stiffness obtained by the traditional calculation method considering the lubrication effect is smaller, especially for the ring-planet gear. Compared with roughness, speed and viscosity, the meshing characteristics of planetary gears are most sensitive to torque.
1. Introduction
Planetary gear system has been widely used in machinery industry because of its advantages of high transmission efficiency, large load capacity and high reliability. The planetary gear system not only suffers from vibration and deformation caused by external excitation, but also the time-varying meshing stiffness (TVMS) is an important excitation source of vibration and noise in the system. Therefore, it is very important to obtain accurate TVMS, which is also the basis for dynamic characteristics analysis. Due to different processing methods and accuracy, the actual contact tooth surface has different microscopic morphologies.
At the same time, in order to reduce tooth surface wear and friction [1, 2], the lubricating oil film also exists on the tooth surface. The mechanism of the effects of tooth surface micromorphology and lubrication on mesh stiffness has not been thoroughly studied. The tooth surface micromorphology and lubrication both affect the contact state and TVMS of the tooth surface, and have an important impact on the durability and service life of the planetary gear system [3]. The coupling effect of tooth surface micromorphology and lubrication on the meshing characteristics of planetary gears cannot be ignored.
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LIU Ning, MA Hui, GUAN Hong, ZHOU Sai-nan, ZHAO Tian-yu, CAO Peng, WU Yu-ping (2025). Analysis of meshing characteristics of planetary gear system considering tooth surface roughness and elastohydrodynamic lubrication. Journal of Central South University. https://doi.org/10.1007/s11771-025-6020-5
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Frequently Asked Questions
What are the key factors affecting planetary gear meshing characteristics?
The study reveals that tooth surface roughness and elastohydrodynamic lubrication significantly affect meshing characteristics, with torque being the most sensitive parameter.
How does the proposed model improve gear contact analysis?
The paper proposes an improved 3D anisotropic fractal model that accounts for roughness and lubrication, refining the 3D-LTCA method for planetary gears.
What is the effect of asperity contact on lubrication regime?
Asperity contact changes the lubrication from elastohydrodynamic to mixed lubrication, reducing oil film stiffness.
Which gear pair is more affected by tooth surface roughness?
The ring-planet gear shows greater sensitivity to surface roughness compared to the sun-planet gear.
Why is accurate time-varying meshing stiffness important?
Accurate TVMS is crucial for dynamic analysis and predicting vibration and noise in planetary gear systems.
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