Patent ID: 7882766

Claim:
An automatic torque-switching apparatus, comprising: a tubular apparatus housing; a motor coaxially fixed to a back end of the tubular apparatus housing, a motor shaft of which protrudes from a center of the forward surface of the motor and extends coaxially into the tubular apparatus housing, and a tip of the motor shaft reaches a position near a forward end of the tubular apparatus housing; an output flange rotatably supported via a first bearing on the forward end of the tubular apparatus housing, wherein the tip part of the motor shaft is rotatably supported via a second bearing in a concave part formed in a central portion of an inside end surface of the output flange; a wave-gear reduction device, a one-way clutch, and a torque limiter coaxially positioned within the tubular apparatus housing which are arranged in this order from the forward end to the back end of the tubular apparatus housing; the wave-gear reduction device being provided with a rigid internal gear, a cup-shaped flexible external gear positioned coaxially inside the rigid internal gear, and a wave generator that has an ellipsoid contour and is fit inside the flexible external gear, wherein the rigid internal gear is formed integrally with the output flange and the wave generator is coaxially fixed to the motor shaft; the cup-shaped flexible external gear being connected to the apparatus housing via the one-way clutch; and the motor shaft and the cup-shaped flexible external gear being connected via the torque limiter so as to rotate integrally only when a torque acting on the cup-shaped flexible external gear is less than or equal to a prescribed value.