Numerical analysis of the lubricating gap between the gear shaft and the journal bearing in water hydraulic internal gear pumps

摘要

Water hydraulics has drawn considerable attention in recent years for its environmental friendliness. This paper presents a numerical model for analysing the lubricating gap between the gear shaft and the journal bearing in water hydraulic internal gear pumps. The model consists of two parts: the gear part that addresses the radial force on the gear shaft and the film part that addresses the film characteristics of the gear shaft/journal bearing interface. The radial force is obtained by summing the fluid pressure around the gear circumference and the meshing force of the gear pair. The film characteristics are analysed by an elastohydrodynamic model that involves the evaluation of the film geometry, the film pressure, and the elastic deformation of the gear shaft/journal bearing interface. The radial force evaluated by the gear part is balanced by the film pressure evaluated by the film part. The gear part is validated by experiments on an oil internal gear pump from the aspect of the outlet pressure ripple, and the film part is validated by comparison with the results from other research groups. The proposed model allows the evaluation of radial micro-motion as well as the eccentric positions of the gear shaft. In addition, the influence of film deformation is further discussed, suggesting that the maximum film deformation should be maintained under 1.3 times the minimum film height. The proposed model can be used as a tool for design optimization of the water-lubricated journal bearing in water hydraulic internal gear pumps.