KR20050033230A - Damper of washing machine - Google Patents

Abstract

A damper structure of a washing machine is provided to enable quick reduction of vibration and to decrease production of noise by a collision of components when vibration occurs. A damper structure of a washing machine comprises a hollow cylinder(10); a piston body(20) having one end inserted in the cylinder; an extension bar(30) extended from one end of the piston body; a friction ring(40) freely moving from the extension bar and coming in contact with the cylinder by a friction member(41) formed to the outer periphery; and a friction ring rotation-preventing structure for fixing the rotating direction of the friction ring. A friction member(21) is formed to the inserted outer periphery of the piston body and the piston body comes in contact with the cylinder. A fitting projection(31) is formed to the extended end of the extension bar, and the friction ring is formed between the fitting projection of the extension bar and the end of the piston body.

Description

Damper structure of washing machine {Damper of washing machine}

The present invention relates to a damper structure, and in detail, the damping force is applied by being divided into multiple stages according to the amount of vibration generated in the washing machine, so that both large and small vibrations can be quickly and properly reduced in a low noise state. It relates to a two-step damper structure of a washing machine.

The washing machine is classified into a drum type, agitator type, and a pulsator type according to a washing method. In particular, the drum type washing machine is provided with a protrusion formed on the inner wall of the drum, so that washing is performed by the impact force of the laundry being lifted up and down along the inner circumferential surface of the drum when the drum rotates.

Such a drum washing machine is less damage to the laundry, there is an advantage that you can use less washing water in recent years, its use is increasing.

1 is a view schematically illustrating a structure of a general drum washing machine.

Referring to FIG. 1, the drum washing machine may further include a case 3 having a hollow rectangular parallelepiped shape, a tub 1 accommodated in the case 3 to contain water, and an inside of the tub 1. And a drum (2) for receiving laundry, and a driving motor (2a) mounted on the rear surface of the tub (1) to rotate the drum (2).

The operation of a general drum washing machine will be described.

First, when the drum 2 is rotated by the rotational force of the drive motor, the laundry accommodated in the drum 2 rotates together. At this time, since the drum 2 is rotated at a low speed, if the laundry is placed on the upper side of the drum 2 while the drum is rotating, the laundry is dropped by gravity and collides with the water contained in the tub 1. The dirt from the laundry is lost by the impact force between the laundry and the washing water generated at this time.

In addition, the weight (4) for correcting the center of gravity in the front and rear / left and right direction of the tub (1) formed on a predetermined side of the tub (outer periphery), the case (3) and the tub (1) Both ends are respectively connected to the spring (5) for buffering the amount of vibration generated in the tub (1) and the drum (2), and both ends are respectively connected to the case (3) and the tub (1) A damper (8) is included to dampen the amount of vibration generated at.

The weight (4) is to adjust the center of gravity of the tub (1), thereby removing the vibration that may be generated due to the eccentric center of gravity of the tub (1).

In addition, the amount of vibration generated by the operation of the tub 1 is buffered by the spring 5 and attenuated by the damper 8 so that the amount of vibration generated during the operation of the tub 1 is rapidly attenuated. .

In detail, the damper 8 includes a cylinder 6 having one end connected to the tub 1 side, and a piston rod 7 having one end connected to the case 3 side and inserted into the cylinder 6. Included.

2 is a cross-sectional view of a general damper.

Referring to FIG. 2, the general damper 8 is formed with a cylinder 6 and a piston rod 7 having a predetermined portion inserted therein as described above. In addition, a tub side fastener 61 for connecting the cylinder 6 to the tub 1, a case side fastener 71 for connecting the piston rod 7 to the case 3, and the piston rod. The friction member 9 is formed at one end of the cylinder 7 to perform frictional action with the inner circumferential surface of the cylinder 6, and is further formed inside the piston rod 7 to compress the air inside the cylinder 6. Aeration holes 72 are included to avoid this.

The operation of the damper 8 will be described with reference to the configuration of the damper 8 as described above.

When a certain amount of vibration occurs in the tub 1 and the drum 2, a relatively different positional displacement occurs between the inner circumferential surface of the cylinder 6 and the outer circumferential surface of the piston rod 7. Then, by the friction member 9 formed between the cylinder 6 and the piston rod 7, the vibration amount is changed into frictional heat and attenuated.

In addition, in order to prevent the damper 8 from being damaged when the tub 1 swings back, forth, left, and right, the tub side fastener 61 and the case side fastener 71 include a predetermined hole illustrated in a circle. And is fixed to the tub 1 and the case 3 in a state where movement is possible. In addition, the vent 72 may be configured such that, when the piston rod 7 is moved to the left with reference to the drawings, the air escapes to the outside to prevent the air inside the cylinder 6 from being compressed to weaken the damping force. Make a passage.

On the other hand, the drum washing machine is a case where a large amount of vibration and a small amount of vibration is generated can be generated both cases. For example, since the drum rotational speed is severely changed in the intermittent dehydration section in the dehydration section, a large amount of vibration is generated. In addition, since the change of the drum rotational 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 damper 8 as described in the drawing. Therefore, in the case where a small amount of vibration is generated, the damper 8 acts as a rigid body so that it is not possible to quickly attenuate the amount of vibration, and the noise is also large. When a large vibration amount is generated, not only the vibration amount can be quickly attenuated by the vibration amount exceeding the displacement limit of the damper 8, but also the damper 8 is broken. In view of this, it is common for the conventional damper 8 to form the damper 8 so as to be suitable when a large amount of vibration is generated.

As such, the conventional damper cannot actively cope with a change in the amount of vibration, and thus has a disadvantage in that noise and vibration are severely generated and inconvenience in use increases.

In other words, a large damping force is applied to a section where a large amount of vibration is generated so that the amount of vibration is rapidly attenuated, and a small damping force is generated in a section where a small amount of vibration is generated, thereby quickly reducing vibration and reducing noise. It must be.

The present invention has been proposed in order to solve the problems as described above, the appropriate damping force is applied to each case when a large amount of vibration and a small amount of vibration is generated, it is possible to quickly reduce the amount of vibration of the washing machine It is an object to provide a damper.

In addition, the present invention provides a damper of the washing machine to reduce the amount of noise that can be generated due to the impact of other components when the vibration is generated by applying a damping force to the damping force is quickly attenuated by the damper. It aims to provide.

Moreover, an object of this invention is to provide the damper of the washing machine which can prevent the damage of a damper even when a strong vibration amount is generated.

Damper structure of the washing machine according to the present invention for achieving the object as described above is a hollow cylinder; A piston body having one end inserted into the cylinder and having a friction member formed on an outer circumference of the portion to be inserted into contact with the cylinder; An extension bar further extending from one end of the piston body, the engaging end being formed at an extended end; A friction ring formed between the engaging end of the extension bar and the end of the piston body, the friction ring being freely movable with respect to the extension bar and being in contact with the cylinder by another friction member formed on an outer circumference thereof; Friction ring anti-rotation structure is included to ensure that the rotation direction of the friction ring is fixed.

Damper structure of the washing machine of the present invention according to another idea is a hollow cylinder; A piston body having one end inserted into an inner circumference of the cylinder and an extension bar further extending from the piston body; A friction ring formed between the extension bar and an end of the piston body, the friction ring being freely movable with respect to the extension bar and contacting the cylinder by a friction member formed on an outer circumference thereof; And a friction ring anti-rotation structure for fixing the friction ring so that the friction ring is not rotated.

By the damper structure of the washing machine as proposed, it is possible to quickly reduce the amount of vibration generated in the washing machine in a low noise state. In addition, damage to the damper can also be prevented.

Hereinafter, with reference to the drawings propose a specific embodiment of the present invention. However, the spirit of the present invention is not limited to the present embodiment, and those skilled in the art will be able to easily propose another embodiment by adding, deleting, or modifying the elements in the present embodiment.

3 is a cross-sectional view of the washing machine damper according to the spirit of the present invention.

Referring to Figure 3, the damper of the present invention is coupled to the piston body 20, the piston body 20 is inserted into the inner hollow portion of the cylinder 10, the piston body 20 is empty inside the An extension bar 30 further extending from the piston body 20, and is formed to maintain a predetermined interval between the outer circumference of the extension bar 30 and an interview with an inner circumferential surface of the cylinder 10. Circular friction ring 40 is included.

In addition, the tub-side fixture 11 is formed at one end of the cylinder 10 to be connected to the tub of the washing machine, and the case is formed at one end of the piston body 20 to be connected to the case of the washing machine. A plurality of side fasteners 24, a first friction member 21 formed on the outer circumference of the other end of the piston body 20 and causing friction with the inner circumferential surface of the cylinder 10, and on the outer circumferential surface of the piston body 20 Is formed to be long and includes a heat radiation fin 22 for releasing frictional heat. In particular, the first friction member 21 may be formed at the left end of the piston body in order to maximize the moving distance of the piston body 20.

In addition, the second friction member 41 is formed on the outer circumferential surface of the friction ring 40 to cause friction with the inner circumferential surface of the cylinder 10. The first and second friction members 21 and 41 may be configured to have a lubricant applied to a predetermined porous plastic. In addition, the lubricant may be grease. The friction members 21 and 41 may be formed by wrapping a rectangular porous plastic. In addition, various shapes and structures are not prevented from being used as materials of the friction members 21 and 41.

In addition, an elastic deformation tool 32 formed at one end of the extension bar 30, and a locking groove 23 is inserted into the elastic deformation tool 32 is included. In addition, the other end of the extension bar 30, the friction ring 40 is caught when the piston body 20 moves to the right with reference to the drawings, that is, when the cylinder 10 moves to the left with reference to the drawings. It includes a locking end 31 to make.

On the other hand, if the friction ring 40 is rotated, the friction member 41 is pushed to a specific position in the outer circumference of the friction ring 40, it is preferable as a function of the damper, such as to lower the damping force Failure to do so may occur. Therefore, in order to prevent the rotation of the friction ring 40, the friction ring 40 is further formed with a predetermined structure for preventing the rotation.

The operation of the washing machine damper according to the spirit of the present invention will be briefly described.

While the tub-side fixture 11 is connected to the tub of the washing machine, and the case-side fixture 24 is connected to the case, the amount of vibration generated by the washing machine is operated through the tub-side fixture 11. Delivered to the damper. Therefore, the vibration amount generated in the washing machine causes the displacement of the cylinder 10, and moves relative to the piston body 20 fixed to the case and stopped.

When the cylinder 10 moves, the amount of vibration is attenuated by a damping force caused by frictional force generated between the inner circumferential surface of the cylinder 10 and the first friction member 21. On the other hand, when the vibration is severely generated and the displacement of the cylinder 10 is large, the friction ring 40 is brought into contact with the left end of the engaging end 31 and the piston body 20, so that the second friction The friction force is generated in the member 41 by the same mechanism as the first friction member 21.

That is, when the vibration amount is small and the displacement of the cylinder 10 is small, the friction force is applied only between the inner circumferential surface of the cylinder 10 and the first friction member 21 to generate a small damping force. However, when the amount of vibration is large and the displacement of the cylinder 10 is large, not only between the inner circumferential surface of the cylinder 10 and the first friction member 21, but also the inner circumferential surface of the cylinder 10 and the second friction member 41. Friction force is generated between Therefore, greater damping force is generated.

Thus, when the vibration amount is small, a small friction force or a small damping force is applied, and when the vibration amount is large, a large friction force or a large damping force is applied, so that an appropriate damping force is applied according to a specific case depending on the magnitude of the vibration amount. For example, when a large amount of vibration is generated, such as a section of intermittent dehydration, the amount of vibration is large, and a frictional force is generated on both the first friction member 21 / the second friction member 41 and the inner circumferential surface of the cylinder 10 to generate a strong vibration. Damping force is generated. However, when a small amount of vibration such as a main detachment section is generated, the amount of vibration is small, and a frictional force is generated only between the first friction member 21 and the inner circumferential surface of the cylinder 10 to generate a small damping force.

On the other hand, the elastic deformation sphere 32 is an article formed for the stable assembly of the extension bar 30 and the piston body 20, the friction ring 40 is extended after being fitted to the extension bar 30, The bar 30 can be fixed to the piston body 20 as a whole. In other words, after the friction ring 40 is inserted into the outer circumference of the extension bar 30, one end of the extension bar 30 is fitted into the piston body 20 so that the elastic deformation tool 32 is elastically deformed. Then, after the extension bar 30 is inserted to the end to reach the position where the locking groove 23 and the elastic deformation sphere 32 are aligned, the elastic deformation sphere 32 is restored and inserted into the locking groove 23. You lose. By this coupling process, the extension bar 30 and the piston body 20 can be completely fixed.

4A to 4E are cross-sectional views taken along the line A-A 'of the washing machine damper shown in FIG. 3, with reference to the drawings representing the respective embodiments, illustrating the anti-rotation structure of the friction ring 40. FIG.

4A shows a cylinder 10, a second friction member 41, a friction ring 40, and an extension bar 30 formed from the outermost shell. In particular, the outer circumference of the friction ring 40 and the inner circumference of the cylinder 10 are formed in a non-circular shape, for example, an ellipse with reference to the drawings. In addition, the second friction member 41 formed to be wrapped around the outer circumference of the friction ring 40 is also formed in an elliptical shape. As described above, the second friction member 41 may be formed by fitting a rectangular porous plastic of an elastic material. Therefore, the second friction member 41 can be formed into an elliptical shape by itself during the operation fitted to the outer circumference of the friction ring 40 without the shape at the time of manufacture being taken into consideration.

As such, the outer circumference of the friction ring 40 and the inner circumference of the cylinder 10 are fitted in an elliptical shape, so that the mounting direction of the friction ring 40 can be left in its original position without being moved during the operation of the damper. .

As such, the mounting direction of the friction ring 40 is fixed, thereby preventing the folding of the second friction member 41, which may be caused by the positional movement of the friction ring 40, during the operation of the damper. have. And, since the second friction member 41 is not folded, the friction force generated in the friction ring 40 can maintain the value at the time of mounting. As a result, in the operation of the damper, there is an advantage that the reliability can be maintained.

Referring to FIG. 4B, in order to prevent rotation of the friction ring 40, at least an outer circumferential cross section of the extension bar 30 and an inner circumferential cross section of the friction ring 40 are non-circularly exemplarily described with reference to the drawings. Forms oval.

As such, by being formed, the friction ring 40 is fixed only in the mounting direction guided by the shape of the extension bar 30, and does not move in any other way. That is, since the rotation of the friction ring 40 is prevented, it stops only at the position at the time of mounting, and it does not rotate.

Since the rotation of the friction ring 40 is prevented, the effect obtained has already been described with reference to FIG. 4A, and thus the detailed description thereof will be omitted.

Referring to FIG. 4C, a predetermined spline portion 301 is formed between the inner circumferential surface of the friction ring 40 and the outer circumferential surface of the extension bar 30.

The spline portion 301 is characterized in that the discontinuous portion is formed on one side between the friction ring 40 and the extension bar 30, so that the rotation of the friction ring 40 can be prevented. .

Since the spline portion 301 is formed, the effect obtained is the same as described above, and thus the description thereof will be omitted.

Referring to FIG. 4D, a fixed key 302 is formed between the inner circumferential surface of the friction ring 40 and the outer circumferential surface of the extension bar 30.

Since the rotation of the friction ring 40 is prevented by the fixing key 302, deformation of the second friction member 41 may be prevented in advance. However, the fixing key 302 is to prevent the friction ring 40 does not move in the rotational direction, and to move freely in the vertical direction (that is, up and down direction of the ground based on the drawings), the A gap between the extension bar 30 and the friction ring 40 should be formed. Therefore, the fixing key 302 is not forcibly fitted, and is integrally formed on one side of the friction ring 40 and the extension bar 30, and the groove on which the fixing key 302 is inserted is formed on the other side. It is preferable.

Referring to FIG. 4E, a serration 303 is formed between the friction ring 40 and the extension bar 30. Free rotation of the friction ring 40 may be prevented by the serration 303 and may be fixed in the mounting direction.

Meanwhile, the spline part 301, the fixing key 302, and the serration 303, which are observed through FIGS. 4C to 4E, are formed between the extension bar 30 and the friction ring 40. Although shown, it may be formed between the outer peripheral surface of the friction ring 40 and the inner peripheral surface of the cylinder 10. In other words, apart from the second friction member 41 being interposed between the friction ring 40 and the cylinder 10, a predetermined position of the contact surface between the friction ring 40 and the cylinder 10 is provided. In the case where the spline portion 301, the fixing key 302, and the serration 303 are formed, the rotation direction of the friction ring 40 may be fixed without moving, as described above.

Meanwhile, the spline portion 301, the fixing key 302, and the serration 303 illustrated in FIGS. 4C and 4E have a predetermined gap between the extension bar 30 and the friction ring 40. It must be formed in an intervening state. As a result, the rotational direction of the friction ring 40 may not be distorted. Furthermore, the friction ring 40 is independent of the extension bar 30 by the friction force of the second friction member 41. It can be moved back and forth with the cylinder 10.

5 is a view illustrating a case in which a contracting force is applied to the damper of the washing machine according to the present invention, and FIG. 6 is a view illustrating a case in which a tensile force is applied to the damper of the washing machine according to the present invention.

Referring to FIGS. 5 and 6, the operation of the damper according to the present invention will be described. First, when the contracting force is applied, the cylinder 10 is moved in the right direction (arrow direction in FIG. 5). When the cylinder 10 is moved in the right direction, since the first friction member 21 is stopped, frictional force is generated on the contact surface between the inner circumferential surface of the cylinder 10 and the first friction member 21. . However, the second friction member 41 and the friction ring 40 move to the right as with the cylinder 10.

Furthermore, when the moving distance of the cylinder 10 exceeds L1, the left end of the piston body 20 and the right end of the friction ring 40 come into contact, so that the friction ring can no longer be moved together with the cylinder 10. Therefore, the frictional force applied to the cylinder 10 from this time is a frictional force combined with the frictional force of the first friction member 21 and the second friction member 41 is applied.

In addition, when a tension force is applied to the damper, the cylinder 10 is moved to the left direction (arrow direction in FIG. 6). When the cylinder 10 is moved in the left direction, since the first friction member 21 is stopped with respect to the cylinder 10, between the inner circumferential surface of the cylinder 10 and the first friction member 21. Friction force is generated on the contact surface. However, the second friction member 41 and the friction ring 40 move to the left side like the cylinder 10.

Subsequently, when the cylinder 10 is moved and the moving distance of the cylinder 10 exceeds L2, the locking end 31 and the left end of the friction ring 40 come into contact, so that the friction ring is no longer connected with the cylinder 10. It cannot be moved together. Therefore, the frictional force applied to the cylinder 10 from this time is a frictional force combined with the frictional force of the first friction member 21 and the second friction member 41 is applied.

On the other hand, even when the friction ring 40 is moved back and forth several times due to repeated vibrations, since the rotation direction of the friction ring 40 is fixed in one direction, the second friction member 41 may be folded. There is no risk of back. Therefore, stable operation of the damper can be ensured.

7 is a graph illustrating the relationship between the displacement of the cylinder and the damping force in the washing machine damper according to the spirit of the present invention.

Referring to FIG. 7, the displacement L of the cylinder is set as the horizontal axis, and the damping force F by the damper is set as the vertical axis.

Specifically, when the cylinder 10 is moved to the right side (in the direction of the arrow in FIG. 5) by a force applied from the outside, the weak frictional force by the first friction member 21 until the predetermined distance L1 is reached. Only damping force F1 due to is applied. In addition, when the cylinder 10 is moved beyond the predetermined distance L1, the damping force F1 + F2 is applied due to the strong frictional force of the first friction member 21 and the second friction member 41. do. Therefore, the weak damping force is applied to the weak vibration with small displacement, so that the vibration can be quickly attenuated in the absence of noise. In addition, the strong damping force is applied to the strong vibration force having a large displacement, so that the greater friction force and the damping force are applied, so that the vibration can be quickly attenuated without damaging the noise and the damper.

In addition, when the cylinder 10 is moved to the left side (in the direction of the arrow in Fig. 6) by the force applied to the outside, it is due to the weak frictional force by the first friction member 21 until it reaches a certain distance (L2). Only damping force F1 is applied. And, when the cylinder 10 is moved to the left side beyond the predetermined distance (L1), the damping force (F1 + F2) caused by the strong friction force by the first friction member 21 and the second friction member 41 Can be applied. Therefore, the weak damping force F1 is applied to the weak vibration with small displacement, so that the vibration can be quickly attenuated in the absence of noise. In addition, the strong damping force (F1 + F2) is applied to the strong vibration force with a large displacement, the vibration can be quickly attenuated by the larger friction force and damping force without damaging the noise and damper.

That is, by applying different damping force to the damper according to the vibration amount and the magnitude of the displacement, it is possible to quickly damp the vibration in the absence of noise for any vibration.

In particular, since the friction ring 40 is moved only in one direction without rotation, the change in the damping force (F1, F2) that may be generated by the installation direction of the friction ring 40 is prevented in advance. Can be. Therefore, even with continued use, the damping force set at the time of manufacture can be stably applied by the damper.

The idea of the present invention relates to a damper of a washing machine for reducing the amount of vibration generated by the operation of the washing machine, and different frictional and / or damping forces are applied by the damper according to the displacement caused by the amount of vibration and the amount of vibration. By doing so, it is possible to quickly attenuate the vibration generated by the operation of the washing machine in a low noise state.

On the other hand, the embodiments of the present invention are described in that the cylinder is connected to the tub side, the piston body is fixed to the case side, but these forms may be interchanged, even if so configured, in the practice of the present invention There is no problem.

By the damper of the washing machine according to the present invention, when a large amount of vibration is generated during operation of the washing machine and a small amount of vibration is generated, an appropriate damping force is applied to each other, thereby quickly reducing the amount of vibration generated in the washing machine. It works.

In addition, the present invention is applied to the appropriate damping force according to the amount of vibration so that the amount of vibration is quickly attenuated, it is possible to reduce the amount of noise generated due to the collision between the washing machine parts during the generation of vibration to improve the comfort of using the washing machine It can work.

In addition, the present invention has the effect of preventing damage to the damper even when a large displacement of the damper is generated by the strong vibration amount.

In particular, with the damper according to the present invention, since the friction ring and the friction member are not twisted even by the continuous use of the damper, the damping force determined at the time of manufacture can be continuously applied, so that the stable operation of the damper is achieved. There is an effect that can be continued.

1 is a view schematically illustrating a structure of a general drum washing machine.

2 is a cross-sectional view of a general damper.

3 is a cross-sectional view of the washing machine damper according to the spirit of the present invention.

4A-4E are cross-sectional views taken along the line A-A 'in the washer damper shown in FIG.

5 is a view for explaining the case that the contracting force is applied to the damper of the washing machine according to the present invention.

6 is a view illustrating a case where a tensile force is applied to the damper of the washing machine according to the present invention.

7 is a graph illustrating a relationship between a displacement of a cylinder and a damping force in a washing machine damper according to the spirit of the present invention.

<Explanation of symbols for the main parts of the drawings>

10 cylinder 20 piston body 30 extension bar

40: friction ring

Claims (9)

Hollow cylinder; A piston body having one end inserted into the cylinder and having a friction member formed on an outer circumference of the portion to be inserted into contact with the cylinder; An extension bar further extending from one end of the piston body, the engaging end being formed at an extended end; A friction ring formed between the engaging end of the extension bar and the end of the piston body, the friction ring being freely movable with respect to the extension bar and being in contact with the cylinder by another friction member formed on an outer circumference thereof; Damper of the washing machine to reduce the vibration of the washing machine includes a friction ring anti-rotation structure for fixing the rotation direction of the friction ring. The method of claim 1, The friction ring anti-rotation structure is a damper of a washing machine including a non-circular cylinder inner peripheral surface and a non-circular friction ring outer peripheral surface. The method of claim 1, The friction ring anti-rotation structure is a damper of a washing machine including a non-circular friction ring inner circumferential surface and a non-circular extension bar outer circumferential surface. The method of claim 1, The friction ring anti-rotation structure is a damper of the washing machine including an elliptical cylinder inner peripheral surface and a friction ring outer peripheral surface corresponding to the inner cylinder peripheral surface. The method of claim 1, The friction ring anti-rotation structure is a damper of the washing machine including an elliptical extension bar outer peripheral surface and a friction ring inner peripheral surface corresponding to the extension bar outer peripheral surface. The method of claim 1, The friction ring anti-rotation structure damper of the washing machine includes a spline portion on the inner peripheral surface of the cylinder and / or the outer peripheral surface of the extension bar in contact with the friction ring. The method of claim 1, The friction ring anti-rotation structure damper of the washing machine includes a fixing key on the inner peripheral surface of the cylinder and / or the outer peripheral surface of the extension bar in contact with the friction ring. The method of claim 1, The friction ring anti-rotation structure damper of the washing machine includes a serration portion on the inner peripheral surface of the cylinder and / or the outer peripheral surface of the extension bar in contact with the friction ring. Hollow cylinder; A piston body having one end inserted into an inner circumference of the cylinder and an extension bar further extending from the piston body; A friction ring formed between the extension bar and an end of the piston body, the friction ring being freely movable with respect to the extension bar and contacting the cylinder by a friction member formed on an outer circumference thereof; Damper of the washing machine to reduce the vibration of the washing machine includes a friction ring anti-rotation structure for fixing the friction ring is not rotated.