US Patent 7284460 Balancer

A weight 4 which is held by a weight holder 3 in a balancer has a pressing face 4b′ which is pressed against a guide face 12a provided along the circumferential direction of rotation of the weight holder 3 by centrifugal force generated by rotation of a rotary body. When the rotary body rotates, the weight 4 which is pressed against the guide face 12a via the pressing face 4b′ changes its position relative to the rotary body in the circumferential direction of rotation, whereby the weight 4 is disposed in a position in which it suppresses whirling motion of the rotary body. The guide face 12a and pressing face 4b′ are inclined relative to the axial direction of rotation so as to tend to outward side in the diametrical direction of rotation as tending to one side in the axial direction of rotation. The weight 4 is pressed against a receiving portion 7a′ by component of the centrifugal force, in which the component acts along the guide face 12a and pressing face 4b′.