| Summary: | Helical gears have long been known as one of the most commonly used mechanical components in transmitting power. Recently, the power to be transmitted has become large, and the engine speed is also increasing. However, the lubrication condition and the surface temperature that dominate the failure of the helical gear are complicated and not fully understood. Since the surface failure is influenced by temperatures in the tooth contacts, it is very important to know the surface temperatures of gears in operation. However, measuring the surface temperatures of gears in operation is difficult. As an effective means to measure the surface temperatures, method using dissimilar metals is known. The voltage proportional to surface temperatures was produced by contacting dissimilar metals. This is known as Seebeck effect. In this study, S55C (Carbon steel) and SUS316 (Stainless steel) were selected to dissimilar metals. Both dissimilar metals were heat-treated and surface were hardened. SUS316 was vacuum carburizing process and S55C was performed induction hardening. In order to remove the influence multiple meshing, the gear was designed so that the total contact ratio which is the sum of transverse contact ratio and the overlap contact ratio was less than 2. This result secured the area of a single contact zone. Surface temperatures measurement using hardened helical gears succeeded in the area of single contact zone. When we compared the experimental values and the theoretical values using Blok’s formula considering with lengthwise sliding velocity, surface temperatures on gear teeth were largely same.
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