Studies on Tooth Surface Strength of Spur Gears. Effect of Oil Temperature and Hardness of Gears.

In order to study the effect of lubricating oil temperature on tooth surface strength, the temperature of three kinds of oils which have very different viscosities at room temperature was changed between 60°C and 105°C under the condition that the viscosity is kept constant. It was shown that the tooth surface strength of case hardened gears is not affected much by the temperature change, but in the case of tempered gears, the tooth surface strength decreased remarkably with increasing oil temperature. Further, so as to study the effect of hardness on tooth surface strength, the effect of the hardness of tempered gears (HV≒285∼550) and the effective case depth of case hardened gears (heff≒0.2∼1.1mm) on the tooth surface strength were examined and discussed.