Abstract
In the plastic crossed helical gear, there are two types of failure modes. They are excessive wear and tooth breakage. In case of the excessive wear, the lifetime can be evaluated by average meshing teeth temperature. On the other hand, in case of the tooth breakage, the lifetime can be evaluated by the stress ratio, which is the ratio of the tooth root stress and the allowable bending stress of plastics at meshing teeth temperature. Therefore, regardless the gear failure mode, it is possible to estimate the lifetime of plastic crossed helical gear if meshing teeth temperature can be predicted. With regard to this meshing teeth temperature of plastic crossed helical gear, we reported that there is a good correlation between the increase in meshing teeth temperature and the mean flash temperature using Coleman's method. However, this report was the contents about limited conditions. In this study, the meshing teeth temperature of the crossed helical gear when number of teeth of driving and driven gear differs was investigated experimentally. As a result, within the dimensions of the plastic gear which was generally used, we clarified that the mean flash temperature was a useful parameter for evaluating on the increase in meshing teeth temperature of plastic crossed helical gear.
