Patent ID: 10955039

Abstract:
A transmission includes a first shaft that is rotatable in a circumferential direction about a central axis extending in one direction, a second shaft that is rotatable in the circumferential direction and in series with the first shaft in an axial direction in which the central axis extends, a tubular housing, an internal gear including an internal tooth portion, and held by an inner surface of the housing, an annular external gear connected to the second shaft, and including an external tooth portion that partially meshes with the internal tooth portion, and a wave generator connected to the first shaft to deform the external gear such that meshing positions between the internal tooth portion and the external tooth portion shift in the circumferential direction. The internal gear and the housing are defined by separate members. At least one of a joining surface of the internal gear joined to the housing, and a joining surface of the housing joined to the internal gear, includes a recessed portion recessed in radial directions centered on the central axis. At least a portion of the recessed portion overlaps with the internal tooth portion when viewed in the radial directions.