Spiral bevel gears are widely used in aero-engines because of their strong bearing capacity and smooth transmission. The working environment of bevel gear is extremely bad during the change of engine working state. The pitting and scuffing on the tooth surface often occur after disassembly is closely related to the lubrication state of the gear. Relevant data show that more than 50% of mechanical failures of gears are also caused by lubrication failure. Because the working speed of bevel gear is very high, the temperature of lubricating oil supply is high, and the thermal effect of gear meshing cannot be ignored, so it is very necessary to carry out the research on thermal elastohydrodynamic lubrication of bevel gear.
FRYZA et al. measured the oil film thickness of point contact under different working conditions by thin film colorimetric interferometry, and found that the oil film thickness was mainly determined by the entrainment speed and oil viscosity. ZHANG et al. measured the rolling speed of the ball from 0 to 51 According to the distribution of oil film thickness at 15 m/s, it is found that the center of the oil film is no longer flat at high speed, but presents a convergent wedge distribution, and the maximum deviation between the film thickness at high speed and that predicted by Dowson-Higginson isotherm can reach 75%. ZHANG et al. also verified this phenomenon in their experiments and numerical calculations. Wang Yanzhong et al. constructed the unified relationship between the tooth surface and the tool profile surface according to the space surface conjugation principle, and found that the minimum oil film thickness and the maximum pressure on the entire tooth surface appeared at the midpoint of the tooth in the direction of the tooth root under the isothermal condition. Yan Hongzhi and others calculated the pressure distribution on the tooth surface through finite element method, and then solved the minimum oil film thickness of spiral bevel gear based on the Dawson-Higginson minimum film thickness equation. It was found that the higher the rotational speed of spiral bevel gear, the greater the oil film thickness, and the minimum oil film thickness when the gear meshing. XIAO et al. applied the micro-electro-hydrodynamic lubrication point contact model and the adhesive wear model to the gear operation and start-stop stage, and found that the gear high speed plays an important role in the minimum oil film thickness, and the high speed will also produce a greater temperature rise than the load and roughness. Sun Xiaoyu found that the component of the entrainment speed along the major axis of the contact ellipse has a key impact on the thickness of the lubricating film of spiral bevel gears. Because the ellipticity of the contact tooth surface of spiral bevel gears is large, the lubricant leakage caused by the component of the entrainment speed along the major axis of the contact ellipse is limited, so the component of the entrainment speed along the major axis of the contact ellipse has a small impact on the thickness of the lubricating film. In the study of elliptical point contact, Han Xing and others found that the oil film increased significantly with the increase of the velocity parameter. When the parameter doubled, the secondary peak continued to move towards the inlet, and the pressure peak height gradually increased. The load parameter had little effect on the film thickness. MEZIANE et al. verified through experiments that the increase of rotational speed will increase the minimum film thickness, and the increase of load will have little effect on the minimum film thickness, but will increase the central film thickness. At the same time, the increase of external temperature will reduce the central film thickness and the minimum film thickness.
Most of the existing researches on EHL are focused on gears with an online speed of less than 30m/s and conditions with less drastic changes in working conditions. Due to the characteristics of high speed, high temperature and high load of aero-engine transmission, combined with the transmission characteristics of bevel gear, there will inevitably be the position with the highest load and the worst working environment in its transmission process, such as the high speed and high load when the bevel gear meshing in the indexing circle position. In engineering practice, the gear mechanism is often limited by the installation structure and external environment, resulting in the inability to improve the lubrication state by adjusting some structural parameters and operating parameters of the gear. However, most of the existing studies qualitatively study the influence of different parameters (speed, load, etc.) on the gear oil film pressure, film thickness, and temperature rise. The influence degree of each input parameter on the lubrication characteristics is unknown. Therefore, it is necessary to calculate the sensitivity coefficient to obtain the influence degree of each input parameter on the gear lubrication effect. Without changing the gear structure, Change some parameters to effectively improve the lubrication conditions of gears. Taking the central transmission spiral bevel gear of a certain type of engine as the research object, the influence of multiple working conditions and parameters on the distribution of oil film pressure, film thickness and temperature rise in the gear meshing area is studied, and the influence law and degree of different parameters on the characteristic parameters of oil film (maximum pressure, maximum temperature rise and minimum film thickness) are discussed, which provides a theoretical basis for the design and improvement of aero-engine gear lubrication.