Patent Publication Number: US-2006010935-A1

Title: Damper and washing machine having the damper

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates a damper of a washing machine and, more particularly, to a damper for reducing vibration and noise of a washing machine by generating a strong damping force at an interval where vibration is excessively generated and generating zero or a weak damping force at an interval where vibration is small.  
      2. Description of the Background Art  
       FIG. 1  is a sectional view of a general drum washing machine.  
      The related art drum washing machine includes a cabinet  2  forming the exterior, a tub  4  disposed inside the cabinet  2  and storing washing water, a drum  6  rotatably disposed at the inner side of the tub  4  and washing and dewatering the laundry, and a driving motor  10  positioned at a rear side of the tub  4  and rotating the drum  6  by being connected with the drum  6  by a driving shaft  8 .  
      An inlet  12  allowing the laundry to be taken in or taken out therethrough is formed at a front side of the cabinet  2 , and a door  14  for opening/closing the inlet  12  is provided at a front side of the inlet  12 .  
      The tub  4  communicates with the inlet  12  of the cabinet  2 , a plurality of support springs  16  are installed between an upper portion of the tub  4  and an upper inner wall of the cabinet  2 , a plurality of dampers  18  are installed between a lower portion of the tub  4  and a lower inner wall of the cabinet  2  so as to reduce transfer of vibration generated from the tub  4  to the cabinet  2 .  
       FIG. 2  is a sectional view showing the damper of the related art washing machine.  
      The damper  18  of the related art washing machine includes a cylinder mounted on the tub  4 , a piston  22  inserted to be linearly moved in the cylinder  20 , a piston rod  24  integrally formed with the piston  22  and connected with a bottom surface of the cabinet  2 , and a friction member  26  fixed at an outer circumferential surface of the piston  22  and perform a damping operation while rubbing on an inner circumferential surface of the cylinder  20 .  
      A hinge connection part  28  is formed at an upper end of the cylinder  20  and hinge-coupled with an outer circumferential surface of the tub  4 . A lower end of the cylinder  20  is opened to allow the piston rod  24  to be inserted therethrough.  
      The piston  22  includes an insertion recess  32  formed on its outer circumferential surface, to which the friction member  26  is insertedly fixed. A hinge connection part  30  is formed at the lower end of the piston rod  24  and hinged at the bottom surface of the cabinet  2 .  
      In the related art washing machine, when vibration is generated from the tub  4 , the damper  18  rubs on the inner circumferential surface of the cylinder  20  to generate a damping force to reduce vibration.  
      However, the damper is disadvantageous in that the friction member  26  fixed at the piston  22  has such a single damping force that the same damping force is applied to the tub  6  at an interval, such as dewatering process period, where vibration is excessively generated and at an interval, such as a washing process period, where the washing machine is normally operated, the tub support capability and vibration attenuation capability are degraded.  
      Namely, if the frictional force generated from the friction member  26  is set strong, when small vibration is generated, the friction member  26  does not rub on the inner circumferential surface of the cylinder  20 , resulting in that a damping force is not generated, so vibration of the tub  6  is transferred as it is to the cabinet  2  to increase noise and vibration of the washing machine.  
      If the frictional force generated from the friction member  26  is set weak, when strong vibration is generated, a damping force of the friction member  26  is reduced, failing to effectively support the tub  6 , which results in degradation of performance of the washing machine and causing generation of more vibration.  
     SUMMARY OF THE INVENTION  
      Therefore, an object of the present invention is to provide a damper capable of controlling a damping force to generate a desired damping force at a desired point so that a strong damping force can be generated at an interval where excessive vibration is generated and zero or a weak damping force can be generated at a normal interval to thereby reduce vibration and noise of a washing machine, and the washing machine having the damper.  
      To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a damper including: a cylinder; a piston rod disposed to be movable linearly in the cylinder; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.  
      The friction unit includes: holders disposed at equal intervals in a circumferential direction inside the cylinder; a friction member fixed at an outer circumferential surface of the holders and rubbed on the inner circumferential surface of the cylinder according to radial movement of the holders; and an elastic member connected between holders and providing an elastic force in a direction that a radius of the holders is diminished.  
      The damping force control unit includes: an operation unit disposed at an inner circumferential surface of the holders and pressing the holders so as to be expanded in a radial direction; and a driving force generating unit mounted at an upper end of the piston rod and driving the operating unit.  
      To achieve the above object, there is also provided a washing machine including: a cabinet; a tub installed in the cabinet and storing washing water; a drum rotatably disposed inside the tub and washing and dewatering the laundry; a plurality of support springs mounted between an upper portion of the tub and an upper inner wall of the cabinet; and a plurality of dampers installed between a lower portion of the tub and a lower inner wall of the cabinet, wherein the damper includes: a cylinder connected with one of the tub and the cabinet; a piston rod disposed to be movable linearly in the cylinder and connected with the other of the tub and cabinet; a friction unit disposed to be movable in a radial direction inside the cylinder and generating a damping force by rubbing on an inner circumferential surface of the cylinder; and a damping force control unit mounted at the piston rod and controlling a damping force by moving the friction unit in the radial direction.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
      In the drawings:  
       FIG. 1  is a sectional view of a general drum washing machine;  
       FIG. 2  is a sectional view of a damper for a washing machine in accordance with a conventional art;  
       FIG. 3  is a sectional view of a damper in accordance with the present invention;  
       FIG. 4  is an enlarged view of a portion ‘A’ of  FIG. 3 ;  
       FIG. 5  is a perspective view of the friction unit of the damper in accordance with the present invention;  
       FIG. 6  is a front view of the friction unit of the damper in accordance with the present invention; and  
       FIGS. 7 and 8  illustrate operational states of the damper in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The drum washing machine in accordance with a preferred embodiment of the present invention will now be described with reference to the accompanying drawings.  
       FIG. 3  is a sectional view of a damper in accordance with the present invention, and  FIG. 4  is an enlarged view of a portion ‘A’ of  FIG. 3 .  
      As shown in  FIG. 1 , the washing machine of the present invention includes: a cabinet  2  forming the exterior, a tub  4  disposed inside the cabinet  2  and storing washing water, a drum  6  rotatably disposed at the inner side of the tub  4  and washing and dewatering the laundry, a driving motor  10  positioned at a rear side of the tub  4  and rotating the drum  6  by being connected with the drum  6  by a driving shaft  8 , a plurality of support springs  16  installed between an upper portion of the tub  4  and an upper inner wall of the cabinet; and a plurality of dampers  50  disposed between a lower portion of the tub  4  and a lower inner wall of the cabinet  2  and reducing transfer of vibration generated from the tub  4  to the cabinet  2 .  
      The damper  50  includes a cylinder  52  mounted at one of an outer circumferential surface of the tub  4  and a bottom surface of the cabinet  2 , a piston rod  54  mounted at the other of the outer circumferential surface of the tub  4  and the bottom surface of the cabinet  2  and disposed to be movable linearly inside th3 cylinder  52 , a friction unit  56  disposed to be movable in a radial direction on an inner circumferential surface of the cylinder  52  and generating a damping force by rubbing on the inner circumferential surface of the cylinder  52 , and a damping force control unit  58  mounted at the piston rod  54  and controlling a damping force by moving the friction unit in a radial direction.  
      One side of the cylinder  52  is opened to allow the piston rod  54  to pass therethrough, and a hinge connection part  60  which is connected with one of the tub  4  and the cabinet  2  is formed at the other side of the cylinder  52 .  
      The piston rod  54  is disposed to be linearly and reciprocally movable on the inner circumferential surface of the cylinder  52 , and a hinge connection part  62  which is connected with the other of the tub  4  and the cabinet  2  is formed at an end portion of the piston rod  54 .  
      As shown in  FIGS. 5 and 6 , the friction unit  56  includes holders  70  disposed at equal intervals on an inner circumferential surface of the cylinder  52  and moved in a radial direction according to an operation of the damping force control unit  58 , a friction member  72  mounted on an outer circumferential surface of the holders  70  and rubbing on the inner circumferential surface of the cylinder  52 , and an elastic member  74  connected between the holders  70  and providing an elastic force in a direction that a diameter between holders is diminished.  
      The holders  70  are formed in an arc form and includes a sloped portion  76  slidably contacting with the damping force control unit formed at its inner circumferential surface and a fixing recess  78  formed at its outer circumferential surface, to which the friction member  72  is insertedly fixed.  
      The friction member  72  is formed as a circular ring type and its inner circumferential surface is insertedly fixed to the fixing recess  78  of the holders  70  and its outer circumferential surface rubs on the inner circumferential surface of the cylinder  52 . The friction member  72  is made of a material whose diameter can be varied within a certain range, and preferably, made of a grease-absorbed sponge material.  
      The elastic member  74  is also formed as a circular ring type and formed as an elastic body made of a rubber material wound between the holders  70  and providing an elastic force in the direction that the diameter of the holders  70  is diminished.  
      The damping force control unit  58  includes an operating unit  80  disposed at an inner circumferential surface of the holders  70 , expanding the holders  70  in the radial direction so that the friction member  72  can rub on the inner circumferential surface of the cylinder  52 , and a driving force generating unit  82  mounted at an upper end of the piston rod  54  and generating a driving force for driving the operating unit  80 .  
      The operating unit  80  includes a first operating member  84  fixed at an upper surface of the driving force generating unit  80  and a second operating member  86  mounted to be movable in a vertical direction on the first operating member  84 . A sloped portion  88  is formed at at least one of facing surfaces of the first and second operating members  84  and  86  and contacts with the sloped portion  76  of the holder  70  to guide the holder  70  to be slidably moved.  
      A through hole  90  is formed at the center of the second operating member  86  and a fixing bolt  92  penetrates through the through hole  90 . The fixing bolt  92  is engaged with the first operating member  84 . Accordingly, the second operating member  86  is moved in the vertical direction within the interval (T) between the second operating member  86  itself and the head of the fixing bolt  92 .  
      When the first and second operating members  84  and  86  are tightly attached, the sloped portions  88  form a V shape and the sloped portion  76  of the holder  70  contacts with the sloped portions  88 . Accordingly, when the second operating member  86  is moved in the upward direction and spaced apart from the first operating member  84 , the holder  70  is slidably moved in the direction that its diameter is diminished by the elastic force of the elastic member  74 . Then, the friction member  72  is separated from the inner circumferential surface of the cylinder  52 , so no damping force works. And then, when a driving force is generated from the driving force generating unit  82 , the second operating member  86  is moved in the downward direction to be tightly attached with the upper surface of the first operating member  84  and the holder  70  is moved along the sloped portions  88  of the first and second operating members  84  and  86  and expanded in the radial direction. Then, the friction member  72  rubs on the inner circumferential surface of the cylinder  52  to generate a damping force.  
      Preferably, the first and second operating members  84  and  86  are formed as a magnetic material.  
      The driving force generating unit  82  includes a core  94  having a lower end fixed at the piston rod  54  and an upper end at which the first operating member  84  is integrally formed, and a coil  96  wound on an outer circumferential surface of the core  94  and generating a magnetic force by making the core  95  an electromagnet when power is applied thereto. Namely, when power is applied to the coil  96 , the core  94  becomes the electromagnet to generate a magnetic force to pull the second operating member  86 , namely, the magnetic material, in a downward direction.  
      The operation of the damper constructed as described above will now be explained.  
       FIGS. 7 and 8  illustrate operational states of the damper in accordance with the present invention.  
      First, when the drum  6  is rotated at a high speed RPM, power applied to the coil  96  is cut off to make a damping force zero. Namely, the holder  70  is moved in the direction that its diameter is diminished along the sloped portions  88  between the first and second operating members  84  and  86  according to the elastic force of the elastic member  74 . Then, the friction member  72  is separated from the inner circumferential surface of the cylinder  52 , generating no frictional force, so the damping force becomes zero.  
      When the drum  6  is rotated at a normal speed, movement of the second operating member  86  is controlled by adjusting strength of a current applied to the coil  96 , according to which an amount of radial movement of the holder  70  is controlled to control the frictional force between the friction member  72  and the inner circumferential surface of the cylinder  52 , thereby controlling the damping force.  
      If vibration is excessively generated at the drum, a current is applied to the coil  96  to make the core  94  and the first operating member  84  electromagnets to generate attraction with the second operating member, namely, the magnetic material, to pull the second operating member  86  in the downward direction. Then, the holder  70  is moved in the direction that its diameter is increased along the sloped portions  88  of the first and second operating members  84  and  86  to allow the friction member  72  to press the inner wall of the cylinder  52 . Accordingly, the frictional force of the friction member  72  is increased to generate a strong damping force.  
      As so far described, the damper in accordance with the present invention has such an advantage that it can reduce vibration and noise of the washing machine by controlling the damping force by controlling a frictional force between the cylinder and the friction member by adjusting strength of a current applied to the coil.  
      As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.