Patent ID: 8721484

Claim:
A speed reduction mechanism, comprising: a rotary shaft that rotates about a first axis and that has an eccentric portion of which a central axis is a second axis that is offset from the first axis; an input member that is arranged radially outward of the rotary shaft, that has a center hole of which a central axis is a third axis and a plurality of through-holes arranged at equal intervals around the third axis, and that is formed of an external gear provided with a first bearing interposed between an inner periphery of the input member, which defines the center hole, and an outer periphery of the eccentric portion; a rotation force applying member that is in mesh with the input member and that is formed of an internal gear having teeth the number of which is larger than the number of teeth of the external gear; and a plurality of output members that receive rotation force applied to the input member by the rotation force applying member, that output the rotation force to an output target as torque of the output target, and that are passed through the respective through-holes with second bearings provided radially outward of the respective output members, wherein the output members are arranged at such positions that a size S′ that is a sum of a fitting clearance formed between an outer periphery of each of the output members and a corresponding one of the second bearings, a fitting clearance formed between the second bearing and an inner periphery of the input member, which defines a corresponding one of the through-holes, and a radial internal clearance in the second bearing is smaller than a size S that is a sum of a fitting clearance formed between the first bearing and the outer periphery of the eccentric portion, a fitting clearance formed between the first bearing and the inner periphery of the input member, which defines the center hole, and a radial internal clearance in the first bearing.