Planetary reduction gear apparatus
A planetary reduction gear apparatus has a sun gear having external teeth; planetary gears, each having external teeth and configured to be meshed with the sun gear; planetary shafts, each being a rotation shaft of the planetary gear; a ring gear having internal teeth and configured to be meshed with the planetary gears; and a planetary carrier including an annular base plate and an annular back plate. The planetary carrier supports the planetary shafts between the annular base plate and the annular back plate and determines a relative position between planetary gears. The annular base plate is integrally formed with one end of the planetary shaft to support the one end. The annular back plate supports the other end of the planetary shaft. At least one of the planetary shaft and the planetary carrier has lower stiffness in its part adjacent to the one end of the planetary shaft than stiffness of its part adjacent to the other end thereof.
1. 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.
2. The planetary reduction gear apparatus according to claim 1 , wherein the axially extending through-hole is formed in a portion of the annular base plate inner with respect to a portion corresponding to the carrier post in a diametrical direction of the annular base plate.
3. The planetary reduction gear apparatus according to claim 1 , wherein the axially extending through-hole is formed as an arcuate hole concentrically with the planetary shaft, in a portion of the annular base plate inner with respect to a portion corresponding to the planetary shaft in a diametrical direction of the annular base plate.
4. The planetary reduction gear apparatus according to claim 1 , wherein the axially extending through-hole is formed in a portion of the annular base plate outer with respect to a portion corresponding to the planetary shaft in a diametrical direction of the annular base plate.
5. The planetary reduction gear apparatus according to claim 1 , wherein the carrier post is hollow, and the axially extending through-hole is formed in a portion of the annular base plate facing a hollow portion of the carrier post.
6. The planetary reduction gear apparatus according to claim 1 , wherein a thin-walled portion is provided, as lattice grooves, on the annular base plate.
7. The planetary reduction gear apparatus according to claim 1 , wherein the carrier post has a lateral section in a shape of a trapezoid.