Load state of tapered roller bearings used for pinion gear of gear units in electric railway vehicle

Abstract

The purpose of this paper is to understand the load state of pinion bearings used for a gear unit in an electric railway vehicle. For this purpose, a system capable of measuring the rolling element load distribution of the pinion bearing in an actual gear unit was constructed, and the measurement was conducted under the same conditions as in an actual railway vehicle. Generally, tapered roller bearings are used for pinion bearings in a face-to-face arrangement, which has an axial clearance (endplay value). Therefore, the effect of the endplay value on the rolling element load distribution was investigated by changing the endplay value at specified values, larger values, and smaller values. As a result of measuring the rolling element load, it was found that the rolling element load tended to increase as the transmission torque of the gear unit increased. In addition, large rolling element loads occurred only when the endplay value was smaller than the specified value. The reason for this is that the axial thermal expansion of the pinion shaft exceeded the endplay value, and the bearing became pressurized. The bearing loads (radial and axial loads) were determined from the measured rolling element loads, and it was found that under conditions where the endplay value was smaller than the specified value, the axial load was significantly higher, which could cause a reduction in bearing life and wear of the bearing. Finally, the load distribution factor of the bearing was determined for each condition. It was observed that the load distribution factor decreased as the endplay value increased, and that for the same endplay value, the load factor tended to be smaller for the conditions with lower torque. It was also found that the load distribution of the rolling elements does not change significantly except under conditions where the endplay value is smaller than the specified value.

Keywords

• railcar gear unit
• pinion bearing
• tapered roller bearing
• helical gear
• rolling element load
• bearing clearance
• endplay
• load distribution factor