In traction gears, which transmit power from electric motors to railway axle, tapered roller bearings have been used for a long time. As a result of the severe operating conditions of this application (extensive vibration, high temperatures and high rotational speeds), many types of damage can occur such as cage breakage, dimensional change of the inner ring, and seizure. For this reason, tapered roller bearings for traction gears have special specifications that are different from those for general applications. In this report, I will first describe these special specifications, then present test results on newly developed tapered roller bearings with improved seizure-resistance, and finally discuss recent technical trends in bearings for the traction gears of bullet trains.
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