Automatic transmission

摘要

Provided with a multi-stage automatic transmission using a reduction planetary gear and a planetary gear set in which the respective thrust forces generated thereat are supported by a low bearing load or a low case load. An automatic transmission is provided with a reduction planetary gear coupled to an input shaft to fix a reaction force element so as to output a reduction rotation to an output element, and a planetary gear set that outputs a speed shift rotation upon input of the subsequent reduction rotation. During at least first gear driving, there are provided a transmission passage in which thrust forces generated at one element of the reduction planetary gear and one element of the planetary gear set, respectively, are transmitted. On that passage, a torsion direction of the spiral teeth of the respective elements are set such that a direction of a thrust force of the element and a direction of the other thrust force of the other element are different from each other during first gear driving. <IMAGE>