To sufficiently and securely fix a power take-out device on a crank shaft by taking out force in a radial direction that causes higher clamping of the both structure groups by a direction conversion means or a clamping element.

Two power take-out devices, namely, a chain wheel 2 and a pulley 3, are tightened to a shaft shoulder part 6 by a clamping screw 4 in the shaft extension part of a crank shaft 1. A clamping ring 7 is arranged between the chain wheel 2 and the pulley 3 as a clamping element, and two conical regions being arranged at a recessed part corresponding to the chain wheel 2 or the pulley 3 are provided. Then, when formation is made so that gap is formed in the clamping ring 7, the chain wheel 2 and the pulley 3 run on to the clamping ring 7 by tightening the clamping screw 4, and the clamping ring is compressed, thus applying clamping force with a constituent in a radial direction, and hence securing improved fixing.