Basic study on measurement of surface temperature at high contact pressure by dynamic thermocouple with dissimilar hardened gears

Power transmission systems using gears require both large capacity and miniaturization. As a result, the gears used in power transmission need to be strong enough to withstand high loads and high engine speeds. Because surface damage and temperature are related, it is very important to know the surface temperature of gears in operation. However, measuring the surface temperature of gears in operation is difficult. As an effective means to measure the surface temperature, method of using dissimilar metals is known. The voltage proportional to surface temperature was produced by contacting dissimilar metals. This is known as Seebeck effect. The authors tried to use two simple ferrous metals. In this study, S55C (Carbon steel) and SUS316 (Stainless steel) were selected to dissimilar metals. Both dissimilar metals were heat-treated and surfaces were hardened. SUS316 was performed plasma carburizing process and S55C was performed induction hardening. As for the gear, it is known that the two or more teeth will mesh simultaneously. In order to remove the influence of the number of tooth in operation, the gear of two sheets were made into the one structure meshed by turns (combined lacked gear). When making the gear of two sheets into one structure meshed by turns. The experiments were operated on maximum condition of contact pressure 1.47GPa in a pitch point. As a result, surface temperature measured almost successfully by combined lacked gear by SUS316 plasma carburizing process and S55C induction hardening. When we compared the experimental values and the theoretical values using Blok's formula, surface temperatures on gear teeth values were largely same.