Patent attributes
A speed reducer includes: a case; an input shaft rotationally driven by an electric motor and having an eccentric shaft portion; an externally toothed gear wheel rotatably supported on the eccentric shaft portion; an output shaft rotatably supported on the case coaxially with the input shaft and having an internally toothed gear wheel; a guide plate formed with a guide recess recessed parallel to the input shaft, and disposed between the input shaft and the externally toothed gear wheel; a guide protrusion provided in the case to protrude parallel to the input shaft to guide sliding of the recess; and a guide portion provided between the externally toothed gear wheel and the guide plate to guide movement of the externally toothed gear wheel relative to the guide plate, thereby guiding the externally toothed gear wheel so as to be revolvable but non-rotatable in cooperation with the recess and the protrusion.
