Patent ID: 8545356

Claim:
A speed change gear device comprising: a housing; a cylindrical first member supported in the housing rotatably about a predetermined rotational axis; a shaft member arranged inside the first member rotatably about the rotational axis and formed with an external gear on a peripheral surface of the shaft member; an annular member arranged inside the first member with the shaft member passing through the annular member, the annular member formed with an internal gear at an internal surface of the annular member, the internal gear meshing with the external gear; a second member arranged such that the second member is not rotatable relative to the housing; and a transmission mechanism that transmits a load from the annular member to the second member; wherein: the external gear differs from the internal gear in number of teeth; the first member is formed with a receiving hole receiving the annular member at a position where an axis of the annular member is at a predetermined distance from the rotational axis; and the annular member is received in the receiving hole such that the annular member is rotatable relative to the first member.