Patent ID: 8444520

Claim:
A gear device capable of transmitting rotational force between a pair of mating members at a predetermined speed reduction ratio, comprising: an outer cylinder fixed to one of the mating members and provided with internal teeth on an inner surface thereof; a crankshaft provided inside the outer cylinder in a rotatable manner about an axis thereof and having an eccentric portion; an external gear mounted to the eccentric portion of the crankshaft and adapted to be rockingly rotated while being meshed with the internal teeth, in conjunction with an eccentric rotation of the eccentric portion; a carrier fixed to the other mating member and having a through-hole formed in a central region thereof to axially penetrate therethrough, wherein the carrier is adapted, according to the rocking rotation of the external gear transmitted thereto, to be rotated relatively and coaxially with respect to the outer cylinder; and a cylindrical body fittingly inserted in the through-hole to become coaxial with the carrier, wherein the carrier has a first portion externally fitted in a fixed position relative to one of opposite end portions of the cylindrical body, and a second portion disposed in axially spaced-apart relation to the first portion and externally fitted in a fixed position relative to an axially intermediate portion of the cylindrical body; the other end portion of the cylindrical body extends toward a corresponding one of the mating members while protruding axially outwardly beyond the second portion; and a remaining portion other than the two portions of the cylindrical body to which the first and second portions are externally fitted, has an outer diameter equal to or less than an outermost diameter of the portion to which the first portion is externally fixed, and an outermost diameter of the portion to which the second portion is externally fixed.