To make it possible to execute the adjustment of the phase difference of a movable eccentric weight to a stationary eccentric weight by improving an exciting machine of a structure obtd. by fixing the stationary eccentric weight to a common revolving shaft and mounting the movable eccentric weight turnably relative to the common revolving shaft.

The movable eccentric weight 51 is pressed in the direction where its phase is advanced by pressing a phase difference control spring 53 as shown in Fig. A. Its phase advance angle is limited by a stopper 61 and the overall eccentric moment of both eccentric weights is zero in the Fig. If the movable eccentric weight 51 is lightly braked while the stationary eccentric weight 49 is rotationally driven in an arrow R direction as shown in Fig. B, the movable eccentric weight deflects the phase difference control spring 53 to delay the phase and attains the max. state of the overall eccentric moment, thereby generating exciting force.