Active dynamic vibration absorber

An active dynamic vibration absorber comprising:

• a weight;
• a frame arranged adjacent to said weight;
• a holding mechanism which is interposed between said weight and said frame and holds said weight movably in one direction in a horizontal plane with respect to said frame, while holding said weight immovably in another direction in the horizontal plane intersecting the one direction and in a vertical direction perpendicular to the horizontal plane;
• detecting means for detecting the relative vibration of a predetermined value in the one direction of said weight with respect to said frame;
• and moving means for relatively moving said weight in the one direction with respect to said frame so as to decrease the vibrational displacement in the one direction of said weight with respect to said frame on the basis of a detection signal from the detecting means, wherein said frame has a pair of vertical wall portions which are opposed to each other in the one direction with said weight located therebetween, and said moving means includes a first rotatable body which is rotatably mounted on one of the pair of vertical wall portions;
• a second rotatable body which is rotatably mounted on another one of the pair of vertical wall portions;
• a first flexible body which is connected at one end portion to said weight and is wound around the first rotatable body;
• a second flexible body which is connected at one end portion to said weight and is wound around the second rotatable body;
• and a flexible body pulling means which is provided on said weight and is connected to other end portions of said first and said second flexible body, such that, in its operation in the one direction, the flexible body pulling means pulls the first flexible body and causes said weight to pull the second flexible body due to the pulling of the first flexible body, while, in its operation in another direction which is a direction opposite to the one direction, the flexible body pulling means pulls the second flexible body and causes said weight to pull the first flexible body due to the pulling of the second flexible body.