Vibration absorber

Abstract

A vibration absorber for absorbing a vibration between first and second members each of which is connected to the vibration absorber, includes a movable member adapted to contact with a fluid, and including a portion connected mechanically to one of the first and second members so that a movement of the fluid and a movement of the portion of the movable member correspond to each other, and a fluid moving member for flowing the fluid in either of an extension direction in which the portion of the movable member moves to increase a distance between the first and second members and a contraction direction in which the portion of the movable member moves to decrease the distance between the first and second members in such a manner that the vibration is restrained by a change of the distance between the first and second members from being transmitted between the first and second member.

What is claimed is:  
     
         1 . A vibration absorber for absorbing a vibration between first and second members each of which is connected to the vibration absorber, comprising, 
 a movable member adapted to contact with a fluid, and including a portion connected mechanically to one of the first and second members so that a movement of the fluid and a movement of the portion of the movable member correspond to each other, and a fluid moving member for flowing the fluid in either of an extension direction in which the portion of the movable member moves to increase a distance between the first and second members and a contraction direction in which the portion of the movable member moves to decrease the distance between the first and second members in such a manner that the vibration is restrained by a change of the distance between the first and second members from being transmitted between the first and second member.    
     
     
         2 . A vibration absorber according to  claim 1 , wherein a reaction force generated elastically in accordance with the movement of the fluid is applicable to the fluid moving member.  
     
     
         3 . A vibration absorber according to  claim 1 , wherein the fluid moving member is reciprocally movable.  
     
     
         4 . A vibration absorber according to  claim 3 , wherein the reciprocal movement of the fluid moving member resonates with a driving frequency at which the fluid moving member is driven reciprocally to flow the fluid in such a manner that the change of the distance between the first and second members for restraining the vibration from being transmitted between the first and second members is generated.  
     
     
         5 . A vibration absorber according to  claim 2 , wherein a characteristic frequency of a reciprocal movement of the fluid moving member determined by a mass or moment of inertia of the fluid moving member and a spring constant of the reaction force is substantially equal to a driving frequency at which the fluid moving member is driven reciprocally to flow the fluid, so that the reciprocal movement of the fluid moving member resonates with the driving frequency.  
     
     
         6 . A vibration absorber according to  claim 5 , wherein the spring constant is a dynamic spring constant.  
     
     
         7 . A vibration absorber according to  claim 2 , wherein a characteristic frequency of the fluid moving member determined by a mass or moment of inertia of the fluid moving member and a spring constant of the reaction force is slightly larger than a driving frequency at which the fluid moving member is driven reciprocally to flow the fluid in such a manner that the change of the distance between the first and second members for restraining the vibration from being transmitted between the first and second members is generated.  
     
     
         8 . A vibration absorber according to  claim 7 , wherein the spring constant is a dynamic spring constant.  
     
     
         9 . A vibration absorber according to  claim 2 , wherein a driving frequency at which the fluid moving member is driven reciprocally to flow the fluid is equal to or slightly more than a frequency of the vibration between the first and second members.  
     
     
         10 . A vibration absorber according to  claim 1 , wherein the movable member includes an elastic member elastically deformable in accordance with the movement of the fluid so that the portion of the movable member is movable with the movement of the fluid and a reaction force generated elastically in accordance with the movement of the fluid is applied to the fluid moving member.  
     
     
         11 . A vibration absorber according to  claim 1 , wherein the fluid is a liquid.  
     
     
         12 . A vibration absorber according to  claim 1 , further comprising a reservoir chamber for receiving therein the fluid to be moved by a first side of the fluid moving member other than a second side of the fluid moving member for moving the fluid in contact with the movable member, and another movable member which forms at least partially the reservoir chamber and is elastically movable in accordance with the movement of the fluid in the reservoir chamber, so that a reaction force generated elastically in accordance with the movement of the fluid in the reservoir chamber is applied to the fluid moving member.  
     
     
         13 . A vibration absorber according to  claim 12 , further comprising a main chamber for receiving therein the fluid movable with a movement of the portion of the movable member, and an orifice for fluidal communication at least partially throttled between the main chamber and the reservoir chamber.  
     
     
         14 . A vibration absorber according to  claim 1 , further comprising a throttle through which the fluid movable with the movement of the portion of the movable member is flowed by the fluid moving member.  
     
     
         15 . A vibration absorber according to  claim 12 , further comprising a main chamber for receiving therein the fluid movable with a movement of the portion of the movable member, an orifice for fluidal communication at least partially throttled between the main chamber and the reservoir chamber, and a throttle through which the fluid movable with the movement of the portion of the movable member is flowed by the fluid moving member.  
     
     
         16 . A vibration absorber according to  claim 15 , wherein the fluidal communication between the main chamber and the reservoir chamber is prevented from being performed through the throttle.  
     
     
         17 . A vibration absorber according to  claim 15 , wherein the fluidal communication between the main chamber and the reservoir chamber is performed by the orifice and the throttle fluidally connected in series between the main chamber and the reservoir chamber.  
     
     
         18 . A vibration absorber according to  claim 14 , wherein the fluid moving member is reciprocally movable, and the fluid in the throttle resonates with the reciprocal movement of the fluid moving member.  
     
     
         19 . A vibration absorber according to  claim 14 , wherein a driving frequency at which the fluid moving member is driven reciprocally to flow the fluid is slightly larger than a characteristic frequency of the fluid in the throttle.  
     
     
         20 . A vibration absorber according to  claim 16 , wherein a vibration of the fluid in the throttle and a vibration of the fluid in the orifice harmonize with each other.  
     
     
         21 . A vibration absorber according to  claim 17 , wherein a vibration of the fluid in the throttle and a vibration of the fluid in the orifice harmonize with each other.  
     
     
         22 . A vibration absorber according to  claim 14 , wherein a reaction force generated elastically in accordance with the movement of the fluid is applicable to the fluid moving member, and a characteristic frequency of the fluid moving member determined by a mass or moment of inertia of the fluid moving member and a spring constant of the reaction force is slightly larger than a characteristic frequency of the fluid in the throttle.  
     
     
         23 . A vibration absorber according to  claim 1 , further comprising a baffle member between the movable member and a part of the fluid moving member at which part the fluid is moved with the movement of the portion of the movable member.  
     
     
         24 . A vibration absorber according to  claim 23 , wherein the baffle member covers the part of the fluid moving member to prevent the part of the fluid moving member from facing to the movable member in the extension and contraction directions.  
     
     
         25 . A vibration absorber according to  claim 23 , wherein the baffle member covers the part of the fluid moving member to decrease a cross-sectional area through which the part of the fluid moving member faces to the movable member in the extension and contraction directions.  
     
     
         26 . A vibration absorber according to  claim 3 , wherein the fluid moving member is rotationally movable on a rotational axis.  
     
     
         27 . A vibration absorber according to  claim 26 , wherein the fluid moving member includes at least two vanes for moving the fluid, and the vanes are distant circumferentially from each other.  
     
     
         28 . A vibration absorber according to  claim 27 , wherein the fluid moving member moves an axial flow of the fluid and a radial flow of the fluid at respective sides opposite circumferentially to each other on each of the vanes.  
     
     
         29 . A vibration absorber according to  claim 26 , further comprising a reservoir chamber for receiving therein the fluid to be moved by a first side of the fluid moving member other than a second side of the fluid moving member for moving the fluid in contact with the movable member, wherein the reservoir chamber is arranged at a radially outside of the fluid moving member so that the fluid flows radially between the reservoir chamber and the fluid moving member.  
     
     
         30 . A vibration absorber according to  claim 29 , wherein the reservoir chamber extends circumferentially around the fluid moving member.  
     
     
         31 . A vibration absorber according to  claim 26 , wherein each of the extension and contraction directions is substantially parallel to the rotational axis so that a part of the fluid moving member at which part the fluid is moved with the movement of the portion of the movable member is restrained from facing to the movable member in the extension and contraction directions.  
     
     
         32 . A vibration absorber according to  claim 26 , wherein each of the extension and contraction directions is substantially perpendicular to the rotational axis.  
     
     
         33 . A vibration absorber according to  claim 27 , further comprising another movable member adapted to contact with the fluid, and including a portion connected mechanically to another one of the first and second members so that a movement of the portion of the another movable member and the movement of the fluid correspond to each other, wherein the portions of the movable member and the another movable member move with the movements of the fluid flowed respectively by the vanes.  
     
     
         34 . A vibration absorber according to  claim 26 , further comprising an electromagnetic rotary actuator for driving rotationally the fluid moving member, wherein a torque for driving rotationally the fluid moving member is changed by changing a duty ratio of a voltage applied to the electromagnetic rotary actuator.  
     
     
         35 . A vibration absorber according to  claim 13 , wherein the orifice is prevented from extending straight parallel to the extension and contraction directions between the main chamber and the reservoir chamber, so that the movable member and the another movable member are prevented from facing to each other through the orifice in the extension and contraction directions.