Patent ID: 8348803

Claim:
A planetary reduction gear apparatus comprising: a sun gear having external teeth; a plurality of planetary gears, each of the planetary gears having external teeth and being configured to be meshed with the sun gear; a plurality of planetary shafts, each of the planetary shafts being a rotation shaft of each of the planetary gears; a ring gear having internal teeth and configured to be meshed with the planetary gears; a planetary carrier including an annular base plate and an annular back plate, the planetary carrier being configured to support the planetary shafts between the annular base plate and the annular back plate and determine a relative position between planetary gears, the annular base plate being integrally formed with one end of the planetary shaft so as to support the one end, the annular back plate being configured to support an other end of the planetary shaft; and an axially extending carrier post coupling the annular base plate with the annular back plate, wherein the annular base plate is coupled with an output shaft, and has a lower stiffness in its part adjacent to the one end of the planetary shaft than a stiffness of a part of the annular back plate adjacent to the other end of the planetary shaft, wherein an amount of material in the part of the annular base plate adjacent to the one end of the planetary shaft is reduced, and wherein an axially extending through-hole is formed in the annular base plate.