Patent ID: 7284460

Claim:
A balancer comprising: a weight holder which is integrated with a rotary body; and a weight which is held by the weight holder; wherein: the weight holder has a guide face provided along the circumferential direction of rotation; the weight has a pressing face which is pressed against the guide face by centrifugal force generated by rotation of the rotary body; and when the rotary body rotates, the weight which is pressed against the guide face via the pressing fate changes its position relative to the weight holder in the circumferential direction of rotation, and thereby the weight is disposed in a position in which it suppresses whirling motion of the rotary body, wherein: an auxiliary weight storage chamber is provided; an auxiliary weight is stored in the auxiliary weight storage chamber so as to be capable of changing its position in the circumferential direction of rotation of said rotary body; the auxiliary weight storage chamber has an auxiliary guide face provided along the circumferential direction of rotation; the auxiliary weight has an auxiliary pressing face which is pressed against the auxiliary guide face by centrifugal force generated by rotation of the rotary body; the auxiliary guide face and auxiliary pressing face are inclined relative to the axial direction of rotation so as to rend to outward side in the diametrical direction of rotation as tending to one side in the axial direction of rotation; an auxiliary receiving portion which is positioned at the one side relative to the auxiliary weight in the axial direction of rotation is provided on the auxiliary weight storage chamber; and the auxiliary weight is pressed against the auxiliary receiving portion by a component of the centrifugal force, in which the component acts along the auxiliary guide face and the auxiliary pressing face.