Abstract
A vehicle driven by an internal-combustion engine is being shifted to an electric vehicle in recent years. A transmission (reduction gear) is also used for the electric vehicle because the driving motor is effectively used at high speed, and a small size and weight saving are desired than the past. Therefore, gears, main elements of a vehicle transmission, are required higher durability, and the study on the gear strength is of practical importance to develop a high performance transmission with high reliability. Considering these circumstances, the author has carried out the research and development on improving the reliability of the transmission gears. The tooth surface strength of the gears has been increased by using latest material, heat treatment and surface treatment. The gear design technology has been improved to clarify the influence of the tooth surface deviation and the lubricating conditions on the tooth surface strength. Recently, the author has also conducted the research on the prediction of residual surface fatigue life of the gears using X-ray diffraction method. Some of the results are introduced in this paper.
