目的 揭示聚合物短齿变位齿轮在时变热弹流润滑条件下的润滑变化规律及其影响机理,明确短齿变位设计在聚合物齿轮热弹流润滑中的优势。方法 基于无限长线接触理论建立聚合物短齿变位齿轮的时变热弹流润滑模型。综合分析齿轮副材料、传动方式、变位系数对油膜特性的影响,对比短齿变位齿轮在热条件与等温条件下膜厚与压力分布变化,对比热条件下标准齿轮与短齿变位齿轮沿啮合线的膜厚变化。结果 Steel-PA（聚酰胺）齿轮副因其较低弹性模量和导热系数,在相同工况下形成的油膜厚度最大,润滑性能优于Steel-PEEK（聚醚醚酮）与Steel-Steel齿轮副。正传动的最小膜厚与中心膜厚均明显高于其他传动方式,负传动反之。随着变位系数x∑从0.3、0.5增至0.7,最小膜厚呈上升趋势,摩擦系数与最高温升明显降低,提高了弹流润滑的热稳定性。热效应的引入使油膜厚度显著减小,黏度下降导致承载能力减弱,最小膜厚较等温条件下降幅度在10%左右。同时,温升抑制了局部压力峰,但整体油膜稳定性下降。与标准齿轮相比,短齿变位齿轮沿啮合线方向分布的中心膜厚和最小膜厚分均高于标准齿轮。结论 聚合物齿轮副较金属齿轮副具有更优的润滑与承载性能,而短齿变位设计进一步增强了油膜稳定性并降低了接触应力。然而,热效应引起的油膜厚度减小仍是不可忽视的关键因素。
Abstract
With the continuous pursuit of high efficiency, lightweight construction, and low noise in modern mechanical transmission systems, polymer gears have attracted extensive attention in automobiles, household appliances, robotics, and new energy equipment. Their advantages, including low density, cost-effectiveness, corrosion resistance, self-lubrication, and excellent vibration damping, make them ideal for sustainable and quiet power transmission. However, the intrinsic material characteristics of polymers, including low thermal conductivity, small elastic modulus, and a large thermal conductivity coefficient, lead to significant thermal elastic deformation and temperature rise within the tooth contact region under medium to high load and high-speed conditions. These effects induce complex variations in oil film characteristics and lubrication stability, which may ultimately result in film rupture or adhesive wear. To deal with these challenges, this study proposes an optimized tooth profile design and develops a geometric model of a polymer short addendum modified gear. By shortening the addendum height, tooth tip interference is effectively avoided, oil film formation is promoted, and frictional losses are reduced. Furthermore, a positive profile shift is introduced to increase the composite radius of curvature and reduce Hertzian contact stress, enabling stable elastohydrodynamic lubrication (EHL) even under severe loading. The transient thermoelastohydrodynamic lubrication (TEHL) behavior of the short addendum modified gear pair is systematically investigated to reveal the intrinsic lubrication mechanisms and advantages of the profile modification design under coupled thermal-mechanical conditions. A time-varying local line contact model is established for a gear pair with a module of 3 mm, 25 teeth on the pinion, 69 teeth on the gear, and a standard center distance of 141 mm. The governing equations of TEHL, including the Reynolds, film thickness, viscosity, density, load, and energy equations, are numerically solved to achieve full coupling among pressure, temperature, and film thickness fields. The multigrid method is employed in combination with a W-cycle iteration to calculate the pressure and film thickness, while elastic deformation is obtained using a multigrid integration scheme. The temperature field is computed via a column-by-column scanning algorithm. Within each time step, the oil film pressure is updated using the Gauss-Seidel iterative approach, and convergence is achieved when the relative errors of pressure, load, and temperature are below 1×10-4, ensuring high numerical accuracy in transient analysis. The numerical results demonstrate that both material combinations and transmission types significantly affect the lubrication behavior. The Steel-polymer gear pairs exhibit larger film thickness than the Steel-Steel pair, with the Steel-PA (polyamide) gear showing the greatest central and minimum film thicknesses. This superior performance results from PA's low elastic modulus and thermal conductivity, which enhances contact compliance and reduced frictional heating. In contrast, metallic gears, characterized by higher stiffness and conductivity, produce higher contact stresses and thinner films. Regarding transmission type, positively modified gears exhibit greater central and minimum film thickness than standard and negatively modified gears. Increasing the total profile shift coefficient x∑from 0.3 to 0.7 leads to an increase in minimum film thickness and a decrease in both friction coefficient and maximum temperature rise, indicating improved thermal stability of the EHL film under positive modification. When thermal effects are considered, the minimum film thickness decreases by approximately 10% compared with isothermal conditions due to viscosity reduction caused by temperature rise. Although local pressure peaks are slightly mitigated by thermal softening, overall film stability deteriorates because of viscosity degradation and intensified shear heating. Compared with standard gears, short addendum modified gears demonstrate superior load-carrying capacity and thermal stability due to enhanced oil replenishment at the meshing exit and smoother lubrication transitions. In conclusion, polymer gears, particularly PA gears, exhibit excellent potential for reducing contact stress and frictional heat accumulation under high-load and high-speed conditions. The short addendum positive modification design improves oil film formation and load distribution, thereby mitigating pressure concentration and film thinning. Nevertheless, viscosity reduction induced by temperature rise remains a critical factor influencing TEHL performance. These findings provide theoretical guidance and practical insights for the design and optimization of lightweight, high-efficiency polymer gear transmissions under transient thermoelastohydrodynamic conditions.
关键词
聚合物 /
聚酰胺 /
短齿变位齿轮 /
弹流润滑 /
热效应 /
时变
Key words
polymer /
polyamide (PA) /
short-tooth profile-shifted gear /
elastohydrodynamic lubrication /
heat effect /
time-varying
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