Patent attributes
Fine adjustment of the rotation speed ratio or intentional control of the rotation speed ratio is carried out, centered on a desired speed ratio, including 1:1, for the rotation speed ratio between an input shaft and an output shaft. A planetary-roller speed-increasing mechanism whose input shaft is a carrier and whose output shaft is a sun roller, a planetary-roller speed-reduction mechanism whose input shaft is a sun roller and whose output shaft is a carrier, and a worm speed-changing mechanism for rotationally driving a roller ring in contact with planetary rollers of the planetary-roller speed reduction mechanism are provided in a housing. The output shaft of the planetary-roller speed-increasing mechanism and the input shaft of the planetary-roller speed-reduction mechanism are linked.