Patent ID: 8047943

Claim:
A reduction gear transmission comprising: an internal gear; an external gear that comprises a through hole at a position offset from its central axis, wherein the external gear is supported such that the external gear is capable of rotating on its central axis while revolving with respect to a central axis of the internal gear and maintaining a meshed state with the internal gear; a carrier that comprises a support shaft that extends into the through hole of the external gear, wherein the carrier is supported such that the carrier is capable of rotating with respect to the central axis of the internal gear; a crank member that comprises a though hole into which the support shaft extends and an eccentric member that engages inside the through hole of the external gear, wherein a central axis of the eccentric member is offset from a central axis of the support shaft; and a bearing mechanism that comprises an inner ring into which the support shaft fits and an outer ring that fits into the through hole of the crank member, wherein the bearing mechanism supports the crank member such that the crank member is capable of rotating with respect to the central axis of the support shaft, wherein a clearance that extends along the support shaft between the carrier and the inner ring is narrower than a clearance that extends along the support shaft between the carrier and an end face of the crank member.