Flexible shaft structure for transmitting high torque

Abstract

A flexible shaft structure comprises: a core wire having flexibility; holding portions provided on the core wire; a first wire wound around the core wire substantially at right angles with respect to an axial line of the core wire; and a second wire which is spirally wound around the first wire and of which both ends are respectively fixed to the holding portions. Accordingly, when an input-side holding portion rotates about a shaft, the rotational torque is transmitted to an output-side holding portion by the second wire. In this case, since the second wire is wound around the first wire wound around the core wire, the winding diameter of the second wire for transmitting rotational torque can be enlarged. As a result, tensile force acting on the second wire becomes smaller and stress acting on the core wire via the first wire or the holding portions accordingly becomes smaller.