Patent ID: 8241164

Claim:
A joint driving apparatus for a robot, comprising: an oscillating internally meshing reduction mechanism fixed to a first member and rotating a second member relatively with respect to the first member, the first member constituting a part of a fixing block of the robot, the second member constituting a part of a movable block of the robot, the oscillating internally meshing reduction mechanism having an external gear, an internal gear meshing with the external gear, an output member arranged at the side of the external gear in an axial direction so as to output a relative rotation of the internal gear with the external gear, the output member being connected to the second member; a center shaft member fixed to the output member, the center shaft member being a hollow shaft with a hollow portion penetrating through a central part of the oscillating internally meshing reduction mechanism, the center shaft member having a shaft portion extending axially beyond the output member and up to the side opposite to the external gear; a ring portion integrally formed with the first member and extended inwardly at the side opposite to the external gear in the axial direction of the output member, the ring portion facing the shaft portion of the center shaft member; and an oil seal disposed between the ring portion and the shaft portion of the center shaft member rotating relatively with the ring portion.