Abstract: A controlling transmission comprising a planetary gear mechanism in which at least one pair of intermediate gears are interposed to mesh with a sun gear and an internal gear and in which intermediate shafts respectively supporting the intermediate gears are fixed on a carrier. The indexing positions for fixing the intermediate shafts on the carrier are set such that a tooth surface contacting state, in which one of the intermediate gears meshes with the sun gear and the internal gear, and another tooth surface contacting state, in which the other of the intermediate gears meshes with the sun gear and the internal gear, are determined to have opposite power transmitting directions.

Abstract: Herein disclosed is a controlling transmission to be used with an industrial robot or the like, which is constructed of a planetary or star gear mechanism having at least one pair of intermediate gears arranged between a sun gear and an internal gear. The paired intermediate gears are set by the movement adjustment of a movement adjusting mechanism such that one of them has its back-lash eliminated with respect to the rotations in the clockwise direction whereas the other has its back-lash eliminated with respect to the rotations in the counter-clockwise direction.