GEAR AND GEAR DRIVING APPARATUS

摘要

A gear in which an oil film can be sufficiently formed between the surface of the teeth of the gear rotating at a high speed and the mating gear surface and the occurrence of pitting, abrasion, and scoring is prevented. This gear can be prevented from increasing in temperature and wearing and have improved durability. The gear has countless minute dimples randomly arranged in the tooth surface, wherein the surface having the dimples has a surface roughness parameter, Ryni, in the range represented by 0.8 µm=Ryni=2.3 µm. Thus, the tooth surface has the high ability to form an oil film. This gear can have a long life even when used under poor-lubrication conditions including a low viscosity and an extremely small oil-film thickness.