Study on Wear Characteristics of the Rack-and-Pinion Driving Mechanism in the Rack Railway Under Mixed Elastohydrodynamic Lubrication

The rack-and-pinion is a crucial driving mechanism in the rack railway, especially when climbing slopes. As an open transmission system with low speed and heavy load, it is prone to failures primarily caused by tooth surface wear. Therefore, it is essential to understand wear characteristics of the tooth surface to ensure the safety and the service life of the rack railway. In this paper, a prediction model for tooth surface wear (TSW) of the rack-and-pinion driving mechanism in the rack railway under mixed elastohydrodynamic lubrication (EHL) is established. The meshing parameters of the rack-and-pinion are calculated. Then the contact pressure of the asperity is calculated according to Hertz's elastic contact theory and load sharing concept. The sliding distance at the contact point is achieved by single point observation method. Taking into account the effects of lubrication state, surface roughness, and contact temperature on the tooth surface, a wear model for the rack-and-pinion under mixed EHL is established, and the wear characteristics of the driving pinion are studied. Effects of working parameters, surface roughness and geometrical parameters on the wear depth of the driving pinion are further investigated. The findings of this study can be used as a basis for predicting the wear of the rack-and-pinion under mixed EHL and optimizing the design of the rack-and-pinion driving mechanism in the rack railway.