GETRIEBEVORRICHTUNG

The number of parts constituting a gear transmission is reduced, and a low cost gear transmission is presented. External gears 18X and 18Y have a number of teeth differing from a number of teeth of an internal gear 48, and are maintained in a meshing state with the internal gear 48. A center through hole and offset through holes 19X and 19Y are formed in the external gears 18X and 18Y. Column-shaped members 46 of a carrier pass through the offset through holes 19X and 19Y of the external gears 18X and 18Y. A pair of supporting members 42X and 42Y of the carrier supports each end of the column-shaped members 46. A pair of grooves is formed on a surface of a shaft of a crank member 14 at positions between which eccentric rotation members are interleaved. Rolling elements 8X and 8Y and outer races 6X and 6Y are arranged between each of the supporting members 42X and 42Y and the grooves. The shaft of the crank member 14 is supported so as to be capable of rotating with respect to the carrier and incapable of moving in its axial direction.