11. Influence of pinion shaft bearing endplay (axial clearance) on its seizure initiation

In order to prevent pinion bearing seizure and increase the reliability of gear units, it is important to ensure that sufficient endplay is maintained with the pinion bearings during rotation (Fig. 1). Bench rotation tests were conducted to measure changes in endplay, variations in endplay caused by changes in temperature of the pinion bearings and the peripheral parts were estimated through calculation.

Results showed that the lower the temperature of the gear oil, the greater the reduction in endplay immediately after the rotation start of the shaft. In addition, the difference between measured and calculated endplay was 0.02 mm at most, confirming that the tendency of their variations were almost the same (Fig. 2).

The rotational torque of the pinion bearings and the temperature of each component were also measured. It was revealed that, when the (calculated) endplay reduced to near 0mm due to changes in temperature of the pinion bearings and its peripheral parts during rotation, seizure occurred, and the bearing shaft torque and temperature suddenly rose (Fig. 3).

From these results, it can be concluded that assembly methods capable of not reducing the endplay to near 0 mm during the shaft rotation, and structures capable of eliminating the adjustment of the endplay, were found to be effective in preventing pinion bearing seizure.

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