Patent ID: 8337355

Claim:
An eccentric speed reducer comprising: a casing having internal teeth provided on an inner circumference thereof; an external gear housed in the casing and having external teeth provided on an outer circumference thereof for meshing with the internal teeth; a plurality of crankshafts passing through holes provided in the external gear and disposed in a circumferential direction along the inner circumference of the casing, the crankshafts configured to rotate to allow the external gear to eccentrically rotate; a base carrier having a rotation supporting hole for rotatably supporting one end of the crankshafts; an end carrier that rotatably supports the other end of the crankshafts; and a plurality of struts each disposed between the crankshafts in a circumferential direction along the inner circumference of the casing and formed integrally with the base carrier, the struts connecting the base carrier and the end carrier, the struts including, at a basal portion of a peripheral side surface where the struts are continuous with the base carrier, a first curved portion and a second curved portion being in a form of a curved surface having a different radius of curvature and each being continuous with the base carrier, the first curved portion provided at a supporting hole-facing side of the struts disposed facing the rotation supporting hole, the second curved portion provided between an outer side and the supporting hole-facing side, the outer side being located in the struts at an outer position in a radial direction with respect to the inner circumference of the casing and on a side facing the inner circumference of the casing, and the second curved portion having a larger radius of curvature than the first curved portion.