Effect of bearing types on performance of bearings for gear units of railway vehicles

Abstract

Helical gears are commonly used in the gear units of railway vehicles in Japan, and the bearing types used for the gear units are tapered roller bearings. In this gear unit bearing arrangements, it is important to appropriately adjust the combined clearance, called the endplay, of the two bearings supporting the pinion to prevent the damage such as seizure. Our previous research has shown that the smaller the endplay value at gear unit assembly (Initial endplay value) and the lower the ambient temperature, the greater the decrease in endplay value during rotation and the greater the risk of seizure. One of method to prevent seizure is to increase the initial endplay value, but this means an increase in the internal clearance of the bearings, which may reduce the fatigue life of the bearings or cause damage to their cages due to increased vibration. In order to prevent seizure without reducing bearing life, therefore, this study has examined the use of cylindrical roller bearings with ribs that allow a certain degree of axial displacement of inner rings and outer rings, and has compared its performance with that of a conventional structure using tapered roller bearings through various rotating tests. As a result, it is found that the temperature rise immediately after the start of rotation and torque of pinion shaft are lower for the cylindrical roller bearings with ribs than for the tapered roller bearings during the rotation test using the actual gear unit. Further, the results of rotating tests under the radial and axial loads for the pinion bearings alone showed that the torque of cylindrical roller bearings with ribs tended to be lower than that of tapered roller bearings under a large range of flow rate and temperature of lubricants.

Keywords

• machine element
• tribology
• railway vehicle
• gear unit
• pinion bearing
• tapered roller bearing
• cylindrical roller bearing