Investigation on sealing gap between ring gear and case in internal gear machines

Abstract

This paper presents a new modeling approach for studying the oil film characteristics between the ring gear and the case in internal gear machines. In traditional research, the assembly relationship of ring gear and case bore was considered as an ideal cylindrical pair, and the micro motion of ring gear and its influence on oil film height and pressure had not been discussed yet. However, wedge oil film between the ring gear and the case is actually formed due to the pressure acting on ring gear teeth while Internal Gear Machines are running, causing micro motion of the ring gear. The model presented mainly consists of two parts namely the gears meshing model that deals with the pushing force and the oil film model that deals with the supporting force. The gears meshing process is numerically modeled based on the characteristics of the involute, after which the pushing force can be precisely integrated. The oil film pressure field is analyzed based on the lubrication theory of the oil film under different oil film height field, after which the supporting force is precisely integrated. The supporting force is important for balancing the pushing force, being responsible for functions of sealing and lubricating. Consequently, the simulation model is implemented with MATLAB and running in co-simulation to obtain the resultant force of the ring gear, which should stay at its minimum value to achieve of the goal of minimizing shear stress and preventing excessive wear. Finally, the dynamic characteristics of the ring gear's micro motion and pressure distribution are analyzed.