The design methodology in terms of plastic gears is essentially based on those developed for steel gears, in spite of the fact that various kinds of design methodology have been proposed for plastic gears in recent years. Recently, several problems have been pointed out in relation to this design methodology since there are several experimental evidence, none of which can be clearly explained by the existing methodology. Therefore Tsukamoto, one of our co-workers, has performed many experiments and has proposed an entirely new strength formula, adopting the quantity referred to as the product of the contact period of teeth and loading torque, based on experimental results. The present study is aimed at establishing a practical gear strength design formula by developing Tsukamoto's thory, which is not sufficiently clear in its physical definitions. In this report, a calculation method of the fatigue strength of a gear due to strain energy is proposed.
When the values of coordinates and gradients at some points on a work tooth profile are given, the hob tooth profile can be calculated analytically. In this report, the tooth profile of hobs with rake angle and relief angle is calculated. Transmission of rake angle error and setting error of hobs to a work is analyzed. When the allowable value of a work tooth profile error is given, the allowable value of rake angle error and setting error of hobs can be decided by this method.
