KR101221474B1 - Variable friction damper - Google Patents

Abstract

The present invention is a cylinder having a predetermined space therein; A piston having a piston rod penetrating the cylinder in a vertical direction and a piston head connected to an end of the piston rod and moving vertically in the cylinder; A first friction member extending a predetermined length from the upper and lower surfaces of the cylinder in the direction of the piston head; And a second friction member contacting the first friction member when the piston head is moved upward and downward by a predetermined length extending from the upper and lower surfaces of the piston head in the direction of the first friction member. As a result, efficient attenuation coefficients can be obtained under all vibration conditions in the resonance region and the high frequency region.

Description

Variable friction damper

The present invention relates to a variable friction damper, and more particularly, to a variable friction damper capable of obtaining an efficient damping coefficient in all vibration conditions in the resonance region and the high frequency region.

The friction damper has the function of absorbing or eliminating oscillation of mechanically moved elements, such as deflection of the washing drum on the washing machine caused by imbalance.

1 is a cross-sectional view of a friction damper according to the prior art. As shown, the friction damper according to the prior art includes a cylinder 6 and a piston rod 7 in which a predetermined portion is inserted into the cylinder 6. ) Is formed. In addition, the cylinder 6 may be connected to one side of a vibration generating medium (for example, a tub in a washing machine or a compressor of a refrigerator), and the piston rod 7 may be connected to the other side of the vibration generating medium. And a friction member (9) formed at one end of the piston rod (7) to friction with the inner circumferential surface of the cylinder (6), and further formed inside the piston rod (7). 6) A vent 72 is included to prevent the air inside from being compressed.

The operation of the friction damper 8 will be described with reference to the configuration of the friction damper 8 according to the prior art.

When a certain amount of vibration is generated in a friction generating medium such as a tub of a washing machine or a compressor of a refrigerator, a relatively different positional displacement is generated between the inner circumferential surface of the cylinder 6 and the outer circumferential surface of the piston rod 7. The vibration amount is changed into frictional heat and attenuated by the friction member 9 formed between the cylinder 6 and the piston rod 7.

In addition, the vent 72 is a passage through which air escapes to the outside in order to prevent the air inside the cylinder 6 from being compressed to weaken the damping force when the piston rod 7 is moved to the left with reference to the drawings. To form.

On the other hand, in the vibration generating medium, such as a tub of the drum washing machine, a case in which a large amount of vibration is generated and a case in which a small amount of vibration is generated may be distinguished and both cases may occur. For example, since the drum rotational speed is severely changed in the intermittent dewatering section of the dewatering section, a large amount of vibration is generated. In addition, since the change of the drum rotation speed is not severe in the separation section, a small vibration amount is generated.

However, the same damping force is always generated by the conventional friction damper 8 as described in the drawing. Therefore, in the case where a small vibration displacement is generated (high frequency region), the friction damper 8 acts as a rigid body, which not only can quickly damp the vibration amount but also the noise is large. In the case where a large vibration displacement occurs (resonant region), not only the vibration amount can be rapidly attenuated by the vibration amount exceeding the displacement limit of the damper 8, but also the damper 8 is broken.

Thus, friction dampers require high damping coefficients (damping forces) in large vibration displacements (resonance regions) and low damping coefficients (damping forces) in small vibration displacements (high frequency regions), while conventional friction dampers always provide constant friction. Since only a constant attenuation coefficient can be obtained with an area, there is a problem that an appropriate attenuation coefficient cannot be obtained that can satisfy both vibrations generated in the resonance region and the high frequency region.

The present invention has been invented to solve the above problems, and an object thereof is to provide a variable friction damper capable of obtaining an efficient damping coefficient in all vibration conditions of a resonance region and a high frequency region.

According to an aspect of the present invention for achieving the above object, a cylinder having a predetermined space therein; A piston having a piston rod penetrating the cylinder in a vertical direction and a piston head connected to an end of the piston rod and moving vertically in the cylinder; A first friction member extending a predetermined length from the upper and lower surfaces of the cylinder in the direction of the piston head; And a second friction member contacting the first friction member during vertical movement of the piston head by extending a predetermined length from the upper and lower surfaces of the piston head in the direction of the first friction member.

Preferably, the cylinder is filled with a working fluid, the working fluid is a magnetic flow fluid, characterized in that the piston head is provided with a magnetic induction coil to form a magnetic field according to the application of an external current.

Preferably, the outer side of the piston rod is characterized in that the spring is elastically supported between the cylinder and the external vibration transmission medium.

Preferably, the first friction member has a shape in which the width is constantly reduced along the direction extending toward the piston head, and the second friction member is constantly along the direction extending toward the first friction member. The width is reduced, and the end portions of the first friction member and the second friction member that face each other are positioned to be offset from each other.

Preferably, the first friction member and the second friction member are characterized in that the elastic body made of a deformable.

Preferably, a sponge is attached to the outside of the elastic body.

Preferably, the first friction member has a constant width along the direction extending toward the piston head, the second friction member has a constant width along the direction extending toward the first friction member, End portions facing each other of the first friction member and the second friction member are positioned to be offset from each other.

Preferably, the first friction member and the second friction member is characterized in that made of a rigid body.

Preferably, a sponge is attached to the outside of the rigid body.

In the variable friction damper according to the present invention, the contact area between the first friction member and the second friction member increases as the displacement amount due to vibration increases, so that a damping force corresponding to the displacement amount can be obtained, and thus the magnitude of vibration generated Damping performance can be secured.

In addition, according to the present invention, by varying the rheological properties of the magnetic flow fluid by adjusting the intensity of the amount of current, a wider range of attenuation coefficients can be obtained, and as a result, damping that can more efficiently correspond to the magnitude of the generated vibrations. Performance can be secured.

1 is a cross-sectional view showing a friction damper according to the prior art,
2 is a cross-sectional view schematically showing a variable friction damper according to a first embodiment of the present invention;
3 is a cross-sectional view schematically showing a friction member of a variable friction damper according to a first embodiment of the present invention;
4 is a graph schematically showing an experimental result of a damping coefficient according to the displacement of the variable friction damper according to the first embodiment of the present invention;
5 is a cross-sectional view schematically showing a variable friction damper according to a second embodiment of the present invention;
6 is a cross-sectional view schematically showing a friction member of a variable friction damper according to a second embodiment of the present invention;
7 is a graph schematically showing an experimental result of a damping coefficient according to the displacement of the variable friction damper according to the second embodiment of the present invention;
8 is a cross-sectional view schematically showing a variable friction damper according to a third embodiment of the present invention;
9 is a graph schematically showing an experimental result of a damping coefficient according to the displacement of the variable friction damper according to the third embodiment of the present invention;
10 is a cross-sectional view schematically showing a variable friction damper according to a fourth embodiment of the present invention;
11 is a graph schematically showing an experimental result of a damping coefficient according to a displacement amount of a variable friction damper according to a fourth exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the variable friction damper according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the technical scope of the present invention. Will be.

(Embodiment 1)

2 is a cross-sectional view schematically showing a variable friction damper according to a first embodiment of the present invention, FIG. 3 is a cross-sectional view schematically showing a friction member of a variable friction damper according to a first embodiment of the present invention. 4 is a graph schematically showing the experimental results of the damping coefficient according to the displacement of the variable friction damper according to the first embodiment of the present invention.

As shown in FIGS. 2 to 4, the variable friction damper according to the first embodiment of the present invention includes a cylinder 110, a piston 120, a first friction member 130, and a second friction member 140. It is configured to include.

The cylinder 110 is a cylindrical body, and has a predetermined space in which the piston 120 can be moved in the vertical direction. The cylinder 110 is a vibration generating medium 10, such as a tub of a washing machine or a compressor of a refrigerator, and a vibration transmitting medium (not shown, for example, an outer housing of the washing machine) to which vibration generated from the vibration generating medium 10 is transmitted. Is installed between.

The piston 120 consists of a piston rod 121 and a piston head 122. The piston rod 121 penetrates the upper part of the cylinder 110 in the vertical direction to connect the vibration transmission medium located outside the cylinder 110 and the piston head 122 located inside the cylinder 110. The piston head 122 is connected to the end of the piston rod 121 in the cylinder 110 to move integrally with the piston rod 121 in the cylinder 110. That is, the piston 120 is moved in the vertical direction in the cylinder 110. On the other hand, between the piston rod 121 and the external vibration transmission medium may be provided with a rubber vibration plate 150.

The first friction member 130 is provided on the top and bottom surfaces of the cylinder 110, respectively, and extends a predetermined length in the direction in which the piston head 122 is located from the top and bottom surfaces of the cylinder 110. That is, the first friction member 130 extends in a direction facing each other on the top and bottom surfaces of the cylinder 110.

The second friction member 140 is provided on the top and bottom surfaces of the piston head 122, respectively, and extends a predetermined length from the top and bottom surfaces of the piston head 122 in the direction in which the first friction member 130 is located. That is, the second friction member 140 extends in opposite directions on the top and bottom surfaces of the piston head 122.

By such a configuration, when the piston head 122 moves upward, the second friction member 140 provided on the upper surface of the piston head 122 and the first friction member located on the inner upper surface of the cylinder 110 ( 130 are in contact friction with each other to generate a damping force.

On the contrary, when the piston head 122 moves downward, the second friction member 140 provided on the lower surface of the piston head 122 and the first friction member 130 located on the inner lower surface of the cylinder 110 are mutually different. Contact friction generates damping forces.

Preferably, the first friction member 130 and the second friction member 140 are constantly reduced in width along their extending direction. The end portions of the first friction member 130 and the second friction member 140 facing each other are positioned to be offset from each other.

Specifically, the first friction member 130 provided on the inner upper surface of the cylinder 110 has a triangular longitudinal section that is constantly reduced in width downward. In addition, the second friction member 140 provided on the upper surface of the piston head 122 has a triangular longitudinal section whose width is constantly reduced upward.

In addition, the first friction member 130 provided on the inner lower surface of the cylinder 110 has a triangular longitudinal section that is constantly reduced in width upward. In addition, the second friction member 140 provided on the lower surface of the piston head 122 has a triangular longitudinal section whose width is constantly reduced downward.

At this time, the pointed end of the first friction member 130 facing each other and the pointed end of the second friction member 140 are slightly shifted, and the inclined surface and the first surface of the first friction member 130 are not vibrated. The inclined surfaces of the two friction members 140 are in contact with each other.

By such a configuration, when displacement of the piston head 122 occurs due to vibration in the vibration generating medium 10, the contact area between the first friction member 130 and the second friction member 140 is set to the piston head 122. Depends on the amount of displacement.

That is, when the displacement amount of the piston head 122 is small, the contact area between the first friction member 130 and the second friction member 140 is formed small, so that the damping force between the two friction members 130 and 140 is reduced. Relatively small. Therefore, a damping force suitable for vibration in the high frequency region, that is, small magnitude of vibration can be obtained.

On the other hand, when the displacement amount of the piston head 122 is large, the contact area between the first friction member 130 and the second friction member 140 is large, and thus the damping force between the two friction members 130 and 140 is increased. It is relatively large. Therefore, a damping force suitable for vibration of the resonance region, that is, large magnitude of vibration, can be obtained.

Referring to FIG. 4, it can be seen that attenuation coefficient c in the resonant region with large vibration is obtained more than in the high frequency region with small vibration. In addition, it can be seen that the damping coefficient c increases nonlinearly as the displacement amount x increases.

This is because the damping force due to the contact between the first friction member 130 and the second friction member 140 affects not only the friction area between the two friction members 130 and 140, but also the pressing force between the two friction members 130 and 140. Because I receive. That is, since the compressive force acting between the two friction members 130 and 140 increases as the relative movement amount of the first friction member 130 and the second friction member 140 increases, the first friction member 130 and the second friction member 140 increase. The greater the relative amount of movement of the friction member 140, the greater the damping force is generated.

Preferably, as shown in FIG. 3, the first friction member 130 is formed of an elastic body 131 capable of deforming rubber or the like. In addition, the second friction member 140 is also made of an elastic body that can be deformed, such as rubber. For example, when the first friction member 130 and the second friction member 140 are made of a non-deformable material, when the two friction members 130 and 140 are in contact with each other, the two friction members 130 and 140 are in contact with each other. ) Cannot be moved in directions adjacent to each other. However, in the present invention, since the first friction member 130 and the second friction member 140 are made of an elastic body that can be deformed, such as rubber, the two friction members 130 and 140 continue to move in a state where they are rubbed with each other. It is possible.

More preferably, the outer side of the above-mentioned elastic body 131 is an additional friction member 132 for generating a constant frictional resistance, for example, polyurethane material such as sponge or various types of synthetic fiber material having a certain durability and wear resistance, etc. Of course, an additional friction member may be attached to the outside of the elastic body of the second friction member 140.

Meanwhile, referring to FIG. 2, a spring 160 is elastically supported at an outer lower portion of the cylinder 110 between an outer bottom surface of the cylinder 110 and a vibration damper 150 connected to a vibration transmission medium. The spring 160 provides a restoring force that allows the moved piston head 122 to return to its original position when the vibration occurs in the vibration generating device 10 and the piston head 122 is moved up and down.

As described above, in the variable friction damper according to the first exemplary embodiment of the present invention, the contact area between the first friction member 130 and the second friction member 140 increases as the displacement amount due to vibration increases, thereby providing a damping force corresponding to the displacement amount. You can get it. Therefore, it is possible to secure the damping performance corresponding to the magnitude of the generated vibration.

(Second Embodiment)

5 is a cross-sectional view schematically showing a variable friction damper according to a second embodiment of the present invention, and FIG. 6 is a cross-sectional view schematically showing a friction member of a variable friction damper according to a second embodiment of the present invention. 7 is a graph schematically showing the experimental results of the damping coefficient according to the displacement of the variable friction damper according to the second embodiment of the present invention.

5 to 7, the variable friction damper according to the second embodiment of the present invention has substantially the same configuration as the variable friction damper according to the first embodiment, and includes the first friction member 130 and the second friction. The shape of the member 140 differs from the first embodiment.

The first friction member 130 and the second friction member 140 of the variable friction damper according to the second embodiment of the present invention have a constant width along the extending direction thereof. Referring to FIG. 6, the first friction member 130 ′ and the second friction member 140 ′ have a rectangular longitudinal section along the extending direction thereof.

The end portions of the first friction member 130 ′ and the second friction member 140 ′ facing each other are completely shifted from each other. This is to allow the first friction member 130 ′ and the second friction member 140 ′ facing each other to move in contact with each other as the piston head 122 moves.

With this configuration, when displacement of the piston head 122 occurs due to vibration in the vibration generating medium, the contact area between the first friction member 130 'and the second friction member 140' It depends on the amount of displacement.

That is, when the displacement amount of the piston head 122 is small, the contact area between the first friction member 130 ′ and the second friction member 140 ′ is small, and thus, between the two friction members 130 ′ 140 ′. Damping force is relatively small. Therefore, a damping force suitable for vibration in the high frequency region, that is, small magnitude of vibration can be obtained.

On the other hand, when the displacement amount of the piston head 122 is large, the contact area between the first friction member 130 ′ and the second friction member 140 ′ is large, and thus, between the two friction members 130 ′ 140 ′. Damping force is relatively large. Therefore, a damping force suitable for vibration of the resonance region, that is, large magnitude of vibration, can be obtained.

Referring to FIG. 7, it can be seen that the attenuation coefficient c in the resonant region with large vibration is obtained more than in the high frequency region with small vibration. In addition, it can be seen that as the amount of displacement x increases, the damping coefficient c increases linearly.

Preferably, as shown in FIG. 6, the first friction member 130 ′ is made of a rigid body 131 ′ which hardly deforms such as metal. The second friction member 140 'is also made of a rigid body. For example, when the first friction member 130 ′ and the second friction member 140 ′ are made of a deformable material, the contact area thereof increases while the two friction members 130 ′ and 140 ′ are in contact with each other. Even though the two friction members 130 'and 140' are deformed, the magnitude of the damping force is hardly changed.

However, in the present invention, since the first friction member 130 'and the second friction member 140' are made of a rigid body with little deformation of metal or the like, the contact area of the two friction members 130 'and 140' is changed. As a result, the magnitude of the damping force can also be changed.

More preferably, the outside of the rigid body 131 ′ of the first friction member 130 ′ described above is an additional friction member 132 ′, for example a polyurethane material such as a sponge, or a certain durability and a certain friction resistance. Various types of synthetic fibers and the like having wear resistance may be attached. In addition, an additional friction member may be attached to the outside of the rigid body of the second friction member 140 ′.

On the other hand, also in the variable friction damper according to the second embodiment of the present invention, the spring 160 is elastic at the outer lower portion of the cylinder 110 between the outer bottom surface of the cylinder 110 and the vibration plate 150 connected to the vibration transmission medium. Supported. The spring 160 provides a restoring force that allows the moved piston head 122 to return to its original position when the vibration occurs in the vibration generating device 10 and the piston head 122 is moved up and down.

As described above, in the variable friction damper according to the second embodiment of the present invention, the contact area between the first friction member 130 ′ and the second friction member 140 ′ increases as the displacement amount due to vibration increases, corresponding to the displacement amount. Damping force can be obtained. Therefore, it is possible to secure the damping performance corresponding to the magnitude of the generated vibration.

(Third Embodiment)

8 is a cross-sectional view schematically showing a variable friction damper according to a third embodiment of the present invention, and FIG. 9 schematically shows an experimental result of a damping coefficient according to the displacement amount of the variable friction damper according to the third embodiment of the present invention. It is a graph.

8 and 9, the variable friction damper according to the third embodiment of the present invention is substantially the same configuration as the variable friction damper according to the first embodiment, the working fluid 170 in the cylinder 110 Is different from the first embodiment in that is filled.

Preferably, the working fluid filled inside the cylinder 110 is a magneto-rheological fluid. Accordingly, the third embodiment of the present invention further includes a magnetic induction coil 180 for changing the rheological properties (viscosity, plasticity, elasticity) of the magnetic flow fluid, that is, the MR fluid. The magnetic induction coil 180 is inserted into the piston head 122 to form a magnetic field according to the application of external current.

On the other hand, when the magnetic flow fluid is briefly described, the magnetic flow fluid emits a fluid whose rheological properties (viscosity, plasticity, elasticity) can be reversibly changed in response to the magnitude of the magnetic field, and yields when the strength of the magnetic field increases. The stress is increased to have the property of resisting external movement. These magnetic fluids can be used in a variety of mechanical devices, such as harmonic dampers, vibration isolation systems, clutches, brakes, friction devices, and robotic arms.

In the variable friction damper according to the third embodiment of the present invention using such a magnetic fluid as the working fluid 170, as shown in FIG. 9, when a small vibration occurs in the high frequency region, the piston head 122 is used. A small contact area is generated between the first friction member 130 and the second friction member 140 according to the small displacement amount of. Thus, a small amount of damping force is generated.

On the other hand, when a large vibration occurs in the resonance region, a large contact area is generated between the first friction member 130 and the second friction member 140 according to the large displacement amount of the piston head 122, and therefore, Damping force is generated.

On the other hand, when the vibration occurs in the vibration generating medium 10, the current is applied to the magnetic induction coil 180, the rheological properties of the magnetic flow fluid of the working fluid 170 is changed. At this time, the damping coefficient of the damper according to the intensity of the applied current amount is adjustable, as shown by the dotted line in FIG.

Therefore, in the variable friction damper according to the third exemplary embodiment of the present invention, the contact area between the first friction member 130 and the second friction member 140 increases as the displacement amount due to vibration increases, thereby providing a damping force corresponding to the displacement amount. Not only can be obtained, but also by changing the rheological properties of the magnetic flow fluid by adjusting the intensity of the amount of current, a wider range of damping coefficient can be obtained than the damping coefficient achieved in the first embodiment. As a result, it is possible to secure a damping performance that can more efficiently correspond to the magnitude of the generated vibration.

Meanwhile, in the present invention, the working fluid 170 has been described and illustrated as using a magnetic flow fluid. However, the variable friction damper according to the present invention includes an electric fluid having a reversible change in the rheological properties corresponding to the strength of the electric field. It is easy to see that Electro-rheological Fluids, or ER fluids, may be used.

(Fourth Embodiment)

10 is a cross-sectional view schematically showing a variable friction damper according to a fourth embodiment of the present invention, and FIG. 11 schematically shows an experimental result of a damping coefficient according to the displacement amount of the variable friction damper according to the fourth embodiment of the present invention. It is a graph.

10 and 11, the variable friction damper according to the fourth embodiment of the present invention has a configuration substantially the same as that of the variable friction damper according to the second embodiment, and the working fluid 170 inside the cylinder 110. Is different from the second embodiment in that is filled.

Preferably, the working fluid 170 filled inside the cylinder 110 is a magneto-rheological fluid. Accordingly, the fourth embodiment of the present invention further includes a magnetic induction coil 180 for changing the rheological properties (viscosity, plasticity, elasticity) of the magnetic flow fluid, that is, the MR fluid. The magnetic induction coil 180 is inserted into the piston head 122 to form a magnetic field according to the application of external current.

The variable friction damper according to the fourth embodiment of the present invention using the magnetic flow fluid as the working fluid 170 has a small diameter of the piston head 122 when small vibration occurs in the high frequency region, as shown in FIG. According to the displacement amount, a small contact area is generated between the first friction member 130 ′ and the second friction member 140 ′. Thus, a small amount of damping force is generated.

On the other hand, when a large vibration occurs in the resonance region, a large contact area is generated between the first friction member 130 ′ and the second friction member 140 ′ according to the large displacement amount of the piston head 122. A damping force of magnitude is generated.

On the other hand, when the vibration occurs in the vibration generating medium 10, the current is applied to the magnetic induction coil 180, the rheological properties of the magnetic flow fluid of the working fluid 170 is changed. At this time, the damping coefficient of the damper according to the intensity of the applied current amount is adjustable, as shown by the dotted line in FIG.

Accordingly, in the variable friction damper according to the fourth embodiment of the present invention, the contact area between the first friction member 130 ′ and the second friction member 140 ′ increases as the displacement amount due to vibration increases, corresponding to the displacement amount. Not only can a damping force be obtained, but also by adjusting the strength of the amount of current to change the rheological properties of the magnetic flow fluid, a wider range of damping coefficient can be obtained than the damping coefficient achieved in the second embodiment. As a result, it is possible to secure a damping performance that can more efficiently correspond to the magnitude of the generated vibration.

The embodiments of the present invention described above are merely illustrative of the technical idea of the present invention, and the scope of protection of the present invention should be interpreted according to the claims. In addition, one of ordinary skill in the art to which the present invention pertains will be capable of various modifications and variations without departing from the essential characteristics of the present invention, all technical ideas within the scope equivalent to the present invention of the present invention It should be interpreted as being included in the scope of rights.

110: cylinder 120: piston
121: piston rod 122: piston head
130, 130 ': first friction member 131: elastic body
131 ': Rigid body 132: Additional friction member
140 and 140 ': second friction member 150: dustproof plate
160: spring 170: working fluid
180: magnetic induction coil

Claims (9)

A cylinder having a predetermined space therein;
A piston having a piston rod penetrating the cylinder in a vertical direction and a piston head connected to an end of the piston rod and moving vertically in the cylinder;
A first friction member extending a predetermined length from the upper and lower surfaces of the cylinder in the direction of the piston head; And
And a second friction member extending from the upper and lower surfaces of the piston head toward the first friction member in contact with the first friction member when the piston head moves up and down.
The method of claim 1,
The cylinder is filled with a working fluid, the working fluid is a magnetic flow fluid, the piston head is a variable friction damper, characterized in that the magnetic induction coil is provided to form a magnetic field according to the application of an external current.
The method of claim 1,
A variable friction damper, characterized in that the spring is provided on the outside of the piston rod elastically supported between the cylinder and the external vibration transmission medium.
4. The method according to any one of claims 1 to 3,
The first friction member has a shape in which the width is constantly reduced in a direction extending toward the piston head, and the second friction member is constantly reduced in the width in a direction extending toward the first friction member. The variable friction damper having a shape, wherein the end portions of the first friction member and the second friction member facing each other are positioned to be offset from each other.
5. The method of claim 4,
The first friction member and the second friction member is a variable friction damper, characterized in that made of a deformable elastic body.
The method of claim 5,
Variable friction damper, characterized in that additional friction member is attached to the outside of the elastic body.
4. The method according to any one of claims 1 to 3,
The first friction member has a constant width in a direction extending toward the piston head, the second friction member has a constant width in a direction extending toward the first friction member, and the first friction member and The opposing ends of the second friction member are positioned to be offset from each other.
The method of claim 7, wherein
The first friction member and the second friction member is a variable friction damper, characterized in that made of a rigid body.
9. The method of claim 8,
Variable friction damper, characterized in that additional friction member is attached to the outside of the rigid body.

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