Balancer mechanism for rotating shaft

A balancer mechanism for a rotating shaft for alleviating unbalanced torque acting on the rotating shaft that is freely rotationally supported by a shaft support member via a bearing member, from a member that is supported by the rotating shaft;

• wherein there is provided an assistance torque generation means for generating an assistance torque that mutually cancels out at least a part of the unbalanced torque;
• the assistance torque generation means comprising a cam member that is fixed to the rotating shaft, a cam follower member that contacts against and follows the cam member, and a biasing means for applying assistance torque to the rotating shaft via the cam member by biasing the cam follower member toward the cam member;
• and further comprising a reaction force generation means, by the biasing force of the biasing means, for generating a balancing moment that mutually cancels out a tilting moment that tilts the rotating shaft, around the bearing member as a center, in a direction away from the assistance torque generation means, and that is provided on an opposite side of the rotating shaft from the assistance torque generation means.