With the rapid development of automobile industry and aviation industry, spiral bevel gears have been widely used due to their special structure, high transmission efficiency and stable and reliable operation. In the transmission system of a helicopter, the spiral bevel gear is the key part in the reducer, and its normal operation has a vital impact on the overall performance. During the normal meshing operation of the gear teeth, the lubricating oil located in the meshing area will be subject to the combined action of high pressure and high speed at the same time. A large amount of friction heat may be generated on the gear tooth surface, resulting in excessive local temperature rise, and finally causing serious consequences of the tooth surface gluing.
The flash temperature represents the maximum rise of the tooth surface temperature, and is an important parameter in the design of the ultimate scuffing resistance of spiral bevel gears. At present, Blok flash temperature method is the most widely used calculation method of gear tooth bonding load capacity, but Blok flash temperature method is only applicable to the flash temperature prediction of spiral bevel gears under dry friction conditions. For closed gears, lubricant is usually considered to improve the stability of work, and only a few gear pairs work under dry friction conditions.
Wei Yongqi et al. used Blok flash temperature method to predict the instantaneous maximum temperature of a cylindrical gear with circular tooth profile under mixed elastohydrodynamic lubrication, but the flash temperature calculated by the method is higher than the temperature of the gear tooth body in most positions of the meshing line, which is unreasonable; Yu Guoda and others used Blok flash temperature method to predict the flash temperature of POM gear under dry operation, and the numerical results are similar to the simulation results. Therefore, the application scope of Blok flash temperature method has certain limitations. Considering the actual situation, the heat transfer in the lubricating oil film cannot be ignored.
The flash temperature calculation method mentioned in the guiding national standard for the calculation method of scuffing load capacity of spiral bevel gears issued by China in 2003 is based on the Blok flash temperature method, which is calculated by taking into account the influence of oil film and multiplying by a certain working condition coefficient. However, this method depends on the size of the selected coefficient and has strong subjectivity. Li Wei et al. used the national standard method to estimate the scuffing resistance reliability of spiral bevel gears, and calculated the numerical solution of flash temperature on the meshing line. In addition, in order to simplify the calculation, Blok flash temperature method considers that the flash temperatures on the tooth surfaces of the driving and driven gears are equal when the gear teeth mesh. Through the research of Wang and Cheng, it is confirmed that the flash temperature of the tooth surface of the driving and driven gears is indeed unequal.
In view of the shortcomings of the above Blok flash temperature method, the influence of lubricating oil film on heat transfer is fully considered, and the calculation formula of tooth surface flash temperature under EHL lubrication is deduced without the premise that the flash temperature of the driving and driven gears is equal. The numerical results calculated by this method and Joseito flash temperature method are compared with the results obtained by finite element simulation, which verifies the reliability of this method and provides a theoretical basis for further improving the calculation of gear tooth scuffing bearing capacity.