JP2004162905A - Dynamic vibration absorber and dynamic vibration absorbing device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic vibration absorber installable in a compact fashion even when increasing the mass of a weight, easy to tune to a low natural frequency even when using a great mass of weight and suitably usable for damping the horizontal vibration of a structure due to earthquake or strong wind, and a dynamic vibration absorbing device using the plurality of dynamic vibration absorbers. <P>SOLUTION: The dynamic vibration absorber 1 comprises a dead weight 2, a frame 3 encircling the dead weight 2, totally four U-shaped parallel leaf spring 4, 5, 6, 7 in sets of two laid between the frame 3 and the dead weight 2 for holding the dead weight 2 on the frame movably in all directions in a horizontal plane and holding it non-movably in a vertical direction V, and a damping mechanism 8 for damping the vibration of the dead weight 2 in the horizontal plane. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a dynamic vibration absorber that reduces vibrations generated in a structure due to a strong wind, an earthquake, or the like, and a dynamic vibration absorber using a plurality of the dynamic vibration absorbers.

JP-A-9-119477

  A dynamic vibration absorber described in Patent Literature 1 is known, and this dynamic vibration absorber extends a plurality of leaf spring members from a common support member, and each of the plurality of leaf spring members is provided at a tip of the leaf spring member. Weights are attached to support these weights so that they can swing freely, and a damping member for damping the swinging of these weights is attached.

  By the way, in such a dynamic vibration absorber, when a weight having a large mass is used in order to tune to a low natural frequency so that the weight is swingably cantilevered by the leaf spring member, the leaf spring member is bent from the beginning. Therefore, a large space is required between the weight and the structure in order to perform the predetermined swing of the weight, and it is difficult to install the weight in the structure in a compact manner. , It is difficult to tune to a low natural frequency even with a heavy weight.

  Also, in the above-described dynamic vibration absorber, the swing direction of the leaf spring member is a direction orthogonal to the installation surface of the dynamic vibration absorber on the structure, and therefore, the vibration in the vertical direction of the structure is somewhat effective. However, it is not suitable for damping horizontal vibrations of structures due to earthquakes, strong winds, etc.

  The present invention has been made in view of the above-mentioned points, and a purpose thereof is to provide a predetermined swing to the weight even if the mass of the weight is increased. Since there is no need to provide a large space, it can be installed compactly, and even if a heavy weight is used, there is no need to use a leaf spring member with a large elastic constant. Another object of the present invention is to provide a dynamic vibration absorber that can be suitably used for damping horizontal vibration of a structure due to an earthquake, a strong wind, and the like, and a dynamic vibration absorber using a plurality of such dynamic vibration absorbers.

  The dynamic vibration absorber according to the first aspect of the present invention includes a weight, a frame surrounding the weight, and the weight held movably with respect to the frame in all directions in the plane with respect to the frame, while being perpendicular to the plane. A plurality of vertically placed U-shaped leaf springs interposed between the frame and the weight so as to be held stationary in the vertical direction, and a damping mechanism for damping vibration in the plane of the weight. Is provided.

  According to the dynamic vibration absorber of the first aspect, the U-shaped leaf spring is placed vertically, and is interposed between the weight and the frame, so that the weight is positioned in a plane relative to the frame. While it is movably held in the direction, it is held immovably in the vertical direction perpendicular to the plane, so even if a weight with a large mass is used, it hardly bends in the vertical direction, so that the weight of the weight Even if the mass is increased, there is no need to provide a wide space between the weight and the structure in order to cause the weight to perform a predetermined swing, so it can be installed compactly, and even if a heavy weight is used. Accordingly, it is not necessary to use a leaf spring member having a large elastic constant, so that it is possible to easily tune to a low natural frequency.In addition, by setting the plane to the horizontal plane, the structure of the structure due to earthquake, strong wind, etc. It can be suitably used for damping horizontal vibration.

  In the present invention, preferably, like the dynamic vibration absorber of the second embodiment, the weight is a regular polygon including a substantially regular triangle in plan view, for example, a square, a regular pentagon, and a regular hexagon, and is more preferable. In the example, the square is a regular hexagon, but if a U-shaped leaf spring can be interposed between the vertical wall and the weight as desired, the weight may be formed of a cylindrical body, Furthermore, the shape may be substantially rectangular, circular, oval or the like in plan view, or may be asymmetric with respect to the vertical axis.

  In the present invention, preferably, like the dynamic vibration absorber of the third aspect, the frame is a regular polygon including a substantially regular triangle in plan view, for example, a square, a regular pentagon, a regular hexagon, and In a preferred example, the frame is a square or a regular hexagon, but if a U-shaped leaf spring can be interposed between the vertical wall and the weight as desired, the frame may be formed of a cylindrical body. The shape may be substantially rectangular, circular, elliptical or the like in plan view, or may be asymmetric with respect to the vertical axis.

  In the dynamic vibration absorber according to the fourth aspect of the present invention, the frame body has a pair of X-direction vertical wall portions opposed to each other in the X direction in the plane with the weight interposed therebetween, and the frame in the plane with the weight interposed therebetween. A pair of Y-direction vertical wall portions opposing each other in the Y direction intersecting with the X direction, and one edge portion extending in the vertical direction between each of the pair of X-direction vertical wall portions and the weight; And at least one leaf spring whose other edge extending in the vertical direction is fixed to the weight, is interposed between the X-direction vertical wall portion and the pair of Y-direction vertical wall portions and the weight, respectively. One edge extending in the vertical direction is fixed to the vertical wall portion in the Y direction, and the other edge extending in the vertical direction is fixed to the weight, and at least one other leaf spring is interposed.

  In the present invention, each leaf spring has a U-shaped portion curved between one edge portion extending in the vertical direction and the other edge portion also extending in the vertical direction. The weight is movably held with respect to the frame in all directions in the plane.

  One leaf spring may be interposed between each of the pair of X-direction vertical wall portions and the weight and between each of the pair of Y-direction vertical wall portions and the weight, but preferably, As in the dynamic vibration absorber of the fifth aspect of the present invention, a plurality of leaf springs arranged in parallel are interposed, and each leaf spring has one edge on the vertical wall and the other edge on the other. Are fixed to the weights respectively.

  In the present invention, the Y direction only needs to intersect with the X direction, but is preferably orthogonal to the X direction as in the dynamic vibration absorber of the sixth aspect of the present invention.

  The damping mechanism may be a mechanism using the shear resistance of a viscous body.However, as in the dynamic vibration absorber of the seventh aspect of the present invention, the damping mechanism is fixed to one of the weight and the frame and applies a magnetic field. And a plate-shaped conductor which is fixed to the other of the weight and the frame and generates an eddy current by a relative movement with respect to the magnetic field generator. As in the dynamic vibration absorber according to the eighth aspect, the magnetic field generator includes a permanent magnet that generates a pair of magnetic poles of different polarities facing each other with a gap so as to generate a magnetic field at the center of the conductor. You may.

  Although the dynamic vibration absorber of the present invention is installed in a structure that attenuates vibration, when one dynamic vibration absorber is installed in such a structure, preferably the ninth aspect of the present invention is used. It is tuned to the natural frequency of the installed structure, such as a dynamic vibration absorber.

  The dynamic vibration absorber according to the first aspect of the present invention includes a plurality of the dynamic vibration absorbers according to any one of the first to ninth aspects, and has a natural frequency with respect to the weight of at least one dynamic vibration absorber. Is different from the natural frequency of the other dynamic vibration absorber with respect to the weight.

  According to the dynamic vibration absorber of the first aspect, since the natural vibration frequencies have different natural frequencies with respect to the weight, the different natural frequencies can be brought close to each other to cope with a change in the natural frequency of the installed structure. Therefore, it is possible to preferably attenuate the vibration of the structure irrespective of the change in the natural frequency of the structure, and by adjusting the different natural frequencies to the respective modes of the natural frequency of the installed structure, It is possible to cope with each mode of the natural frequency of the installed structure, so that each mode of vibration can be effectively attenuated.

  In the dynamic vibration absorber of the present invention, as in the second embodiment, the mass of the weight of at least one dynamic vibration absorber may be different from the mass of the weight of another dynamic vibration absorber, As in the third embodiment, the spring constant of at least one dynamic vibration absorber may be different from the spring constant of the other dynamic vibration absorber, and as in the fourth embodiment, at least one dynamic vibration absorber May be different from the damping coefficients of other dynamic vibration absorbers.

  According to the present invention, even if the mass of the weight is increased, it is not necessary to provide a large space between the weight and the structure in order to cause the weight to perform a predetermined swing. Even if a large weight is used, it is not necessary to use a leaf spring member having a large elastic constant, so that it can be easily tuned to a low natural frequency, and in addition, a horizontal vibration of the structure due to an earthquake, a strong wind, etc. And a dynamic vibration absorber that uses a plurality of such dynamic vibration absorbers that can be suitably used for damping the vibration.

  Next, an example in which the present invention and its embodiments are used for a structure will be described in more detail with reference to the drawings. The present invention is not limited to these examples.

  1 to 3, the dynamic vibration absorber 1 of this example is substantially square in plan view and has a weight 2 formed of a rectangular parallelepiped, and surrounds the weight 2 and is substantially square in plan view. While holding a certain frame 3 and the weight 2 with respect to the frame 3 in a plane, in this example, movably in all directions in a horizontal plane, the frame 3 is immovable in a vertical direction perpendicular to the horizontal plane, in this example, a vertical direction V. A plurality of U-shaped leaf springs 4, 5, 6, and 7 which are interposed between the frame 3 and the weight 2 so as to be held, in this example, a set of two U-shaped leaf springs 4, 5, 6 and 7 in total. And a damping mechanism 8 for damping the vibration of the weight 2 in the horizontal plane.

  The frame body 3 fixed to the floor 45 such as the rooftop of the structure has a pair of X directions facing each other in the X direction in the horizontal plane with the gap 2 between the weight 2 and the weight 2. The vertical wall portions 21 and 22 intersect the X direction in the horizontal plane with the gap Y1 between the weight 2 and the weight 2, and in this example, a pair of Y direction verticals facing each other in the orthogonal Y direction. It has walls 23 and 24, and the pair of X-direction vertical walls 21 and 22 and the pair of Y-direction vertical walls 23 and 24 are integrated so as to form a square frame 3 in plan view. Are connected to each other.

  One edge 31 extending in the vertical direction V is vertically provided between the pair of X-direction vertical wall portions 21 and 22 and the side surfaces 33 and 34 of the weight 2, respectively. The other edge portion 32 extending in the direction V is fixed to each of the side surfaces 33 and 34 of the weight 2, and at least one, in this example, two sets of two leaf springs 4 and 5 are interposed. One edge 32 extending in the vertical direction V is provided between the pair of Y-direction vertical wall portions 23 and 24 and the side surfaces 35 and 36 of the weight 2, respectively. The other edge portion 32 extending in the vertical direction V is fixed to each of the side surfaces 35 and 36 of the weight 2, and at least one, in this example, a pair of two in total, two sets of leaf springs 6 and 7 are interposed. Have been.

  Between the X-direction vertical wall portion 21 and the side surface 33 of the weight 2, a plurality of, in this example, a pair of leaf springs 4 are arranged in parallel, and the X-direction vertical wall portion 22 and the weight A plurality of, in this example, a pair of leaf springs 5 is interposed between the side wall 34 and the side wall 34 of the weight 2 between the Y-direction vertical wall portion 23 and the side wall 35 of the weight 2. In this example, a plurality of leaf springs 6 are interposed, and between the Y-direction vertical wall portion 24 and the side surface 36 of the weight 2, a plurality of leaf springs 6 are disposed in parallel. In this example, a pair of leaf springs 7 is interposed, and the leaf springs 4 facing each other with a concave surface are formed on the X-direction vertical wall portion 21 at one edge portion 31 and the side surface of the weight 2 at the other edge portion 32. The leaf springs 5 fixed to each other and facing each other with concave surfaces are fixed to the X-direction vertical wall portion 22 at one edge 31 and to the side surface 34 of the weight 2 at the other edge 32. The leaf springs 6 facing each other with a concave surface are fixed to the Y-direction vertical wall portion 23 at one edge 31 and to the side surface 35 of the weight 2 at the other edge 32, and face each other with a concave surface. Each leaf spring 7 is fixed to the Y-direction vertical wall portion 24 at one edge portion 31 and to the side surface 36 of the weight 2 at the other edge portion 32.

  Each of the leaf springs 4, 5, 6, and 7 has, in addition to one edge 31 extending in the vertical direction V and the other edge 32 extending in the vertical direction V, between the edge 31 and the edge 32. The U-shaped portion 41 is provided, and the weight 2 holds the weight 2 movably with respect to the frame 3 in all directions in a horizontal plane.

  The damping mechanism 8 faces a container 51 fixed to a floor 45 such as a rooftop of a structure, a viscous body 52 stored in the container 51, and a bottom plate 53 of the container 51 with a small gap. The damping mechanism 8 includes a resistance plate 54 disposed in the viscous body 52 and an attachment member 56 for attaching the resistance plate 54 to the bottom surface 55 of the weight 2. Causes the viscous body 52 between the bottom plate 53 and the resistance plate 54 to undergo a shearing deformation, and the relative movement of the weight 2 in the horizontal plane with respect to the floor 45 by the shearing resistance due to the shearing deformation. It is designed to attenuate.

  In the above-described dynamic vibration absorber 1, the frame 3 is fixed to the floor 45 at the lower edge thereof, and is installed on a structure. In this installation, the natural frequency of the weight 2 is tuned to the natural frequency of the structure. In such a dynamic vibration absorber 1, when the structure does not vibrate in the horizontal plane, the weight 2 is movable in all directions in the horizontal plane by the plate springs 4, 5, 6, and 7, and is immovable in the vertical direction V. Each is held.

  In the dynamic vibration absorber 1, the floor 45 of the structure vibrates in the X and Y directions due to an earthquake, a strong wind, or the like, and the weight 2 moves in the X direction relative to the floor 45 in synchronization with the vibration. And the vibration in the Y direction, the vibration causes the viscous body 52 between the bottom plate 53 and the resistance plate 54 to undergo a shearing deformation, and the shear resistance caused by the shearing deformation causes the viscous body 52 to move in the horizontal plane with respect to the floor 45 of the weight 2. The relative movement is attenuated, and the vibration of the structure in the X and Y directions is attenuated by absorbing the vibration energy of the damping mechanism 8.

  By the way, according to the dynamic vibration absorber 1, the U-shaped leaf springs 4, 5, 6, and 7 are vertically arranged, and are interposed between the weight 2 and the frame body 3 to form the weight 2 into a frame. The body 3 is movably held in all directions in the horizontal plane while being held immovably in the vertical direction V perpendicular to the horizontal plane. Therefore, even if the mass of the weight 2 is increased, it is not necessary to provide a large space between the weight 2 and the structure in order to cause the weight 2 to perform a predetermined swing. Even if the weight 2 having a large mass can be installed, it is not necessary to use the leaf springs 4, 5, 6, and 7 having a large elastic constant accordingly, so that it is possible to easily tune to a low natural frequency, In addition, the plane in which the weight 2 is movable with respect to the frame 3 is aligned with the horizontal plane as in this example. Allowed by installed, it can be suitably used for the attenuation of the horizontal direction of the vibration of the structure earthquake, due to strong wind or the like.

  The damping mechanism 8 in the dynamic vibration absorber 1 of this example has a shear resistance due to a shear deformation generated in the viscous body 52 between the bottom plate 53 and the resistance plate 54 due to the relative movement of the weight 2 with respect to the floor 45 in the horizontal plane. A mechanism using a shear resistance of a viscous body configured to attenuate the vibration of the weight 2 in the horizontal plane is provided. Alternatively or additionally, for example, as shown in FIGS. The magnetic damping mechanism 101 may include a plurality of magnetic field generators that are fixed to the weight 2 and, in this example, the weight 2 and generate a magnetic field. 103 and the other of the weight 2 and the frame 3, in this example, a plurality of plate-like members that are fixed to the frame 3 and that generate eddy currents when moved in the X and Y directions relative to the magnetic field generator 103. And a conductor 102.

  The plurality of conductors 102 are fixed to the inner surfaces of the X-direction vertical wall portions 21 and 22 and the Y-direction vertical wall portions 23 and 24, respectively. 35 and 36 respectively have a pair of permanent magnets 106 and 107 having different polarities fixed to each other via a magnetically permeable L-shaped member 105. The conductor 102 and the magnetic field generator 103 are disposed between each of the pair of leaf springs 4, 5, 6, and 7. The permanent magnets 106 and 107 that generate a magnetic field are disposed opposite to each other with a gap in the vertical direction V with the conductor 102 interposed therebetween. In order to reduce the magnetic resistance between the L-shaped member 105 supporting the permanent magnet 106 and the L-shaped member 105 supporting the permanent magnet 107 and form a good magnetic circuit, a magnetically permeable A member may be interposed.

  The permanent magnets 106 and 107 generate a pair of magnetic poles of different polarities facing each other with a gap so as to generate a magnetic field at the central portion O of the plate-shaped conductor 102 when the weight 2 is at rest.

  Such a magnetic damping mechanism 101 causes the floor 45 of the structure to vibrate in the X direction and the Y direction due to an earthquake, strong wind, or the like, and the weight 2 is moved relative to the floor 45 in synchronization with the vibration. When vibrating in the direction and the Y direction, the conductors 102 fixed to the X direction vertical wall portions 21 and 22 and the Y direction vertical wall portions 23 and 24 respectively move in the X direction and the Y direction relative to the magnetic field generator 103. The conductor 102 moves to generate an electromotive force in the conductor 102, and power is consumed by converting eddy current flowing in the conductor 102 into thermal energy (eddy current loss) due to the electromotive force. As a result of generating an electromagnetic force against the movement in the X and Y directions based on the current and the magnetic field of the magnetic field generator 103, the relative movement of the weight 2 in the X and Y directions with respect to the frame 3 is attenuated. When a large force is applied to the frame body 3 such as when the dynamic vibration absorber 1 includes the magnetic damping mechanism 101, the frame body 3 should be formed thick enough to securely fix the conductor 102 and the like. Good.

  Although the above is an example of the dynamic vibration absorber, the dynamic vibration absorber 61 may be configured by having two dynamic vibration absorbers 1 as shown in FIG. In the dynamic vibration absorber 61 shown in FIG. 8, the mass of the weight 2 of one dynamic vibration absorber 1 is made different from the mass of the weight 2 of the other dynamic vibration absorber 1, whereby the weight of the one dynamic vibration absorber 1 is reduced. The natural frequency for the weight 2 is tuned to the frequency of the primary mode of the natural frequency of the structure, and the natural frequency of the other dynamic vibration absorber 1 for the weight 2 is set to the secondary mode of the natural frequency of the structure. The natural frequency of one dynamic vibration absorber 1 with respect to the weight 2 is made different from the natural frequency of the other dynamic vibration absorber 1 with respect to the weight 2.

  In the dynamic vibration absorber 61 shown in FIG. 8, one of the dynamic vibration absorbers 1 is used to make the natural frequency of the weight 2 of the other dynamic vibration absorber 1 different from the natural frequency of the weight 2 of the other dynamic vibration absorber 1. The spring constant mainly determined by the leaf springs 4, 5, 6 and 7 of the vessel 1 may be different from the spring constant mainly determined by the leaf springs 4, 5, 6 and 7 of the other dynamic vibration absorber 1. Good.

  When a dynamic vibration absorber 61 is provided with a plurality of dynamic vibration absorbers 1 as shown in FIG. 8, the damping coefficient mainly determined by the damping mechanism 8 of one of the dynamic vibration absorbers 1 is changed to the other of the dynamic vibration absorbers. The vibration of the structure may be effectively and optimally attenuated by making it different from the attenuation coefficient mainly determined by the attenuation mechanism 8 of the vessel 1.

  In the dynamic vibration absorber 61, the natural frequency of one dynamic vibration absorber 1 with respect to the weight 2 is tuned to the frequency of the primary mode of the natural frequency of the structure, and the natural vibration of the other dynamic vibration absorber 1 with respect to the weight 2. Instead of tuning the number to the frequency of the second mode of the natural frequency of the structure, the natural frequency of one dynamic vibration absorber 1 for the weight 2 and the natural frequency of the other dynamic vibration absorber 1 for the weight 2 May be brought close to each other, whereby it is possible to cope with a change in the natural frequency of the installed structure and to preferably attenuate the vibration of the structure regardless of the change in the natural frequency of the structure. it can.

  In the above description, the dynamic vibration absorber 1 is configured by using the square weight 2 and the frame 3 in a plan view. Instead, as shown in FIG. 9, a regular hexagonal weight 2 and a frame are viewed in a plan view. 9, the dynamic vibration absorber 1 may be formed. As in the dynamic vibration absorber 1 shown in FIG. 9, each of the side surfaces 71 to 76 of the weight 2 and each of the vertical wall portions 81 to 86 of the frame 3 are formed. A single U-shaped leaf spring 91 to 96 may be interposed therebetween. In addition, instead of the square weight 2 and the frame body 3 in plan view, the weight (not shown) which is substantially circular and cylindrical in plan view and is substantially circular in plan view The dynamic vibration absorber 1 may be configured using a frame (not shown) made of a cylindrical body.

It is a top view of a desirable example of an embodiment of the invention. FIG. 2 is a sectional view taken along line II-II of the example shown in FIG. 1. FIG. 2 is a perspective view of a leaf spring of the example shown in FIG. 1. It is a top view of another preferable example of embodiment of this invention. FIG. 5 is an explanatory side sectional view of the example shown in FIG. 4. It is a top view of another preferable example of embodiment of this invention. It is a top view of another preferable example of embodiment of this invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Dynamic vibration absorber 2 Weight 3 Frame body 4, 5, 6, 7 Leaf spring 8 Damping mechanism

Claims (13)

  A weight, a frame surrounding the weight, and a frame that holds the weight movably with respect to the frame in all directions in the plane, while holding the weight immovably in a vertical direction perpendicular to the plane. A dynamic vibration absorber, comprising: a plurality of vertically arranged U-shaped leaf springs interposed between the weight and the weight; and a damping mechanism for damping vibration in a plane of the weight.   The dynamic vibration absorber according to claim 1, wherein the weight is a regular polygon or a circle substantially including a regular triangle in plan view.   The dynamic vibration absorber according to claim 1, wherein the frame is a regular polygon or a circle including a substantially regular triangle in plan view.   The frame body has a pair of X-direction vertical wall portions opposed to each other in the X direction in the plane with the weight interposed therebetween, and a pair of opposed vertical walls in the Y direction intersecting the X direction in the plane with the weight interposed therebetween. A vertical wall portion in the Y direction, one edge extending in the vertical direction between the pair of X direction vertical wall portions and the weight, and the other edge extending in the vertical direction to the X direction vertical wall portion; At least one leaf spring whose edges are fixed to the weight is interposed between the pair of Y-direction vertical wall portions and the weight, and one edge extending in the vertical direction is in the Y-direction. The dynamic vibration absorber according to any one of claims 1 to 3, wherein at least one other leaf spring is interposed in the vertical wall at the other edge extending in the vertical direction and fixed to the weight, respectively.   A plurality of leaf springs arranged in parallel are interposed between each of the pair of X-direction vertical wall portions and the weight and between each of the pair of Y-direction vertical wall portions and the weight, The dynamic vibration absorber according to claim 4, wherein each leaf spring is fixed to the vertical wall at one edge and to the weight at the other edge.   The dynamic vibration absorber according to claim 4, wherein the Y direction is orthogonal to the X direction.   The damping mechanism is fixed to one of the weight and the frame and generates a magnetic field, and the damping mechanism is fixed to the other of the weight and the frame and moves eddy current by relative movement with respect to the magnetic field. The dynamic vibration absorber according to any one of claims 1 to 6, further comprising a plate-shaped conductor that generates the following.   The dynamic vibration absorber according to claim 7, wherein the magnetic field generator includes a permanent magnet that generates a pair of magnetic poles having opposite polarities with a gap so as to generate a magnetic field at a central portion of the conductor.   The dynamic vibration absorber according to any one of claims 1 to 8, which is tuned to a natural frequency of a structure to be installed.   10. A dynamic vibration absorber according to any one of claims 1 to 9, wherein the natural frequency of at least one dynamic vibration absorber with respect to the weight is the natural vibration of another dynamic vibration absorber with respect to the weight. Dynamic vibration absorber different from the number.   The dynamic vibration absorber according to claim 10, wherein the mass of the weight of at least one dynamic vibration absorber is different from the mass of the weight of the other dynamic vibration absorbers.   The dynamic vibration absorber according to claim 10, wherein a spring constant of at least one dynamic vibration absorber is different from a spring constant of another dynamic vibration absorber.   The dynamic vibration absorber according to any one of claims 10 to 12, wherein a damping coefficient of at least one dynamic vibration absorber is different from a damping coefficient of another dynamic vibration absorber.

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