Non Hertz contact gear design theory

Gear is an important industrial basic component and the core component of mechanical equipment. Its performance and reliability determine the performance and reliability of the whole mechanical equipment.

The performance and reliability of gear products involve many technologies, but the most important one is the design technology. Statistics show that the performance and reliability of gear system are 60% – 70% dependent on the design.

At present, China’s gear industry basically relies on ISO gear standard to design gears, and the evaluation of tooth contact strength is based on Hertz contact theory. Hertz contact theory does not consider the relative motion, lubrication, tooth surface roughness, thermal effect and other factors of the contact interface, and the description of contact state is over simplified. The research shows that these factors have important influence on the contact fatigue life of gears. Although there are some influence factors determined by experiments to estimate the influence of the above factors, but “with the further requirements of gear for high power density and long service life, the existing design criteria based on Hertz contact theory are difficult to accurately reveal the tooth contact and failure mechanism, which often leads to insufficient estimation of gear failure mode and life, or waste of materials and power These problems highlight the necessity and importance of correctly describing and grasping the real contact behavior of the tooth surface and surmounting the gear design theory and method based on Hertz contact theory.

It has been proved by practice and theory that EHL will form between the contact surfaces of gears under certain conditions. The EHL film can separate the meshing surfaces of gears, reduce friction and avoid wear, and significantly improve the working efficiency, service life and reliability of gears. Therefore, under the premise of ensuring the contact strength of the gear, if the gear works in the EHL state, it can be considered as an ideal working state.

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