各歯の歯すじ精度ばらつきがトランスミッション歯車の歯面強度に及ぼす影響

抄録

To predict precisely the tooth surface strength of transmission gears has been a very important issue in developing a new vehicle-transmission with high reliability, because failures such as pitting or spalling on the tooth surface have recently determined the gear life. Mass produced transmission gears have some unevenness in helix deviation between the teeth, which is caused by runout of the cutter arbor, heat treatment distortion, assembly errors, etc. It is important to clarify quantitatively the influence of the variability in helix deviation on the tooth surface strength of gears; however, no report on the subject has been published. In this study, gear surface fatigue endurance tests were carried out using carburized gears with five types of uneven helix deviation between the teeth. The results were examined, and the author introduces a new parameter, “Modified Hertzian pressure” that is based on cumulative fatigue damage rule on the tooth surface and the variation of Hertzian pressure during gear mesh. It is demonstrated that tooth surface fatigue life can be estimated quantitatively using this parameter. Based on the information obtained, the influence of the variability in helix deviation on the tooth surface strength is discussed.