Patent ID: 8038562

Claim:
A power transmission device comprising: an outer member configured to be mounted to a vehicle body and having an inboard end and an outboard end, the outer member being formed with two raceways on an inner periphery thereof near said outboard end; an inner member having two raceways formed on an outer periphery thereof so as to radially oppose the respective raceways of the outer member, said inner member further including a bearing inner ring part and a hub ring part, said hub ring part having a wheel-mounting flange formed on an outer periphery at a first end portion of said inner member, said wheel-mounting flange of said hub ring part of said inner member protruding outwardly from said outer member, and said hub ring part, including said wheel-mounting flange thereof, being axially fixed with respect to said bearing inner ring part of said inner member; rolling elements received between the two raceways of said outer member and the two raceways of said inner member in two rows; a rotary shaft coaxial with said inner member, said rotary shaft including a non-eccentric main rotary shaft portion and an eccentric portion that is received in said outer member and fixed with respect to said non-eccentric main rotary shaft portion; an external gear rotatably supported on the eccentric portion of said rotary shaft and having external teeth which are smaller in number than internal teeth formed on the inner periphery of said outer member, and which mesh with said internal teeth; and a torque transmission disposed between said external gear and said bearing inner ring part of said inner member and configured to transmit rotation of said external gear about its own axis when said eccentric portion rotates eccentrically with respect to said inner member, while allowing free rotation of the center of said external gear about the axis of the rotary shaft.