Patent Publication Number: US-2021172106-A1

Title: Washing machine and vibration reduction apparatus thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2019-0159839, filed on Dec. 4, 2019 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The disclosure relates to a washing machine, and more specifically, to a washing machine provided with a vibration reduction apparatus to reduce vibration of a tub according to rotation of a drum in a spin-drying process. 
     2. Description of the Related Art 
     A washing machine is a household appliance that washes laundry, such as clothes, using electric power, and is classified into a pulsator type washing machine in which a pulsator provided inside a rotating tub rotates to generate water current and laundry is washed by the generated water current, and a drum-type washing machine in which lifters are formed on an inner circumferential surface of a rotating tub and laundry is lifted and dropped with the lifters so that the laundry is washed. 
     In general, the pulsator-type washing machine has a top-loading method in which an opening through which laundry is put into a rotating tub is formed in the top of the main body, and the drum-type washing machine has a front-loading method in which an opening through which laundry is put into a rotating tub is formed in the front of the main body. 
     The pulsator-type washing machine includes a cabinet forming the external appearance, a tub accommodating washing water, and a rotating tub accommodating laundry and rotatably provided inside the tub, and the tub is supported against the cabinet by a suspension device. 
     During a spin-drying process, the rotating tub rotates at a high speed, and the rotating tub may perform precession according to weight imbalance of laundry contained in the rotating tub, and the precession of the rotating tub may cause vibration of the tub. The suspension device may be effective in reducing the vibration in the vertical direction of the tub, but not the vibration in the horizontal direction of the tub. 
     SUMMARY 
     Therefore, it is an object of the disclosure to provide a vibration reduction apparatus for effectively reducing the vibration in the horizontal direction of the tub generated during rotation of the rotating tub, and a washing machine having the same. 
     It is another object of the disclosure to provide a vibration reduction apparatus having an improved vibration reduction and preventing deformation of the suspension device, and a washing machine having the same. 
     It is another object of the disclosure to provide a vibration reduction apparatus for reducing vibration of a tub at a transient vibration section in which a large vibration occurs in the tub due to resonance, and preventing vibration of a tub from being transmitted to a cabinet in a normal section in which vibration of the tub is small, such as the highest revolution per minutes (RPM) section, and a washing machine having the same. 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     According to an aspect of the disclosure, there is provided a washing machine including: a cabinet; a tub disposed inside the cabinet; a rotating tub rotatably disposed inside the tub; a suspension device connecting the tub to the cabinet such that the tub is supported by the cabinet; and a vibration reduction apparatus installed between the tub and the suspension device to reduce vibration of the tub according to rotation of the rotating tub, and including a first rod and a second rod rotatably coupled to the first rod. 
     The first rod may be connected to the tub, and the second rod is connected to the suspension device. 
     The first rod may include a hinge pin, and the second rod rotates around the hinge pin. 
     The second rod may include a suspension device connection portion connected to the suspension device, the suspension device may include a suspension bar elongated in one direction, and the suspension device connection portion may be connected to the suspension bar so as to be movable along the suspension bar. 
     The suspension device connection portion may include a holder having a connection groove into which the suspension bar is inserted and a bracket to which the holder is rotatably coupled. 
     The first rod may include a disk formed at a circumference of the hinge pin, and the second rod may include a disk housing into which the disk is inserted. 
     The disk may be provided in a cylindrical shape having an upper surface, a lower surface, and a circumferential surface, and the disk housing may include a first wall and a second wall spaced apart from each other to form a slot into which the disk is inserted. 
     The washing machine may further include a friction member provided inside the disk housing to come in friction with the disk when the second rod rotates around the hinge pin. 
     The disk housing may include a mounting rib formed on at least one of an inner surface of the first wall or an inner surface of the second wall such that the friction member is mounted on the mounting rib. 
     The disk may include a thickness increasing portion, a thickness of which increases such that a frictional force increases according to a rotation angle of the second rod. 
     According to another aspect of the disclosure, there is provided a vibration reduction apparatus for a washing machine including a cabinet, a tub disposed inside the cabinet, and a suspension device connecting the tub to the cabinet, the vibration reduction apparatus including: a first rod including a tub connection portion connected to the tub of the washing machine and a first rod having a first hinge portion; and a second rod including a suspension device connection portion connected to the suspension device and a second rod having a second hinge portion rotatably coupled to the first hinge portion. 
     The first hinge portion may include a disk and a hinge pin provided on a center of the disk, wherein the second hinge portion may include a disk housing into which the disk is inserted and a hinge pin insertion hole formed in the disk housing such that the hinge pin is inserted into the hinge pin insertion hole. 
     The suspension device may include a suspension bar elongated in one direction, and the suspension device connection portion may be connected to the suspension bar so as to be movable along the suspension bar. 
     The vibration reduction apparatus may further include a friction member provided inside the disk housing to come in friction with the disk when the second rod rotates around the hinge pin. 
     The disk may include a thickness increasing portion, a thickness of which increases such that a frictional force increases according to a rotation angle of the second rod. 
     According to another aspect of the disclosure, there is provided a washing machine including: a cabinet having a front plate, a rear plate, both side plates, and a bottom plate; a tub disposed inside the cabinet; a rotating tub rotatably disposed inside the tub; and a plurality of vibration reduction apparatuses installed between the cabinet and the tub in parallel with the bottom plate of the cabinet to reduce vibration of the tub according to rotation of the rotating tub, wherein the plurality of vibration reduction apparatuses includes a first vibration reduction apparatus and a second vibration reduction apparatus each formed to be extended and contracted in a length direction thereof, and a longitudinal central axis of the first vibration reduction apparatus and a longitudinal central axis of the second vibration reduction apparatus are positioned in line with each other. 
     The first vibration reduction apparatus and the second vibration reduction apparatus may be installed between the tub and the rear plate of the cabinet to be in parallel with the rear plate of the cabinet. 
     Each of the plurality of vibration reduction apparatuses may include a cylinder connected to the tub and having an inner space and a piston connected to the cabinet and provided to advance and retract in the inner space of the cylinder. 
     The cabinet may be provided with a guide bar, the tub may be provided with a support pin, and each of the plurality of vibration reduction apparatuses may have one end connected to the guide bar so as to be rotatable on the guide bar while moving in a vertical direction along the guide bar, and an other end connected to the support pin so as to be rotatable on the support pin while being restricted from moving in the vertical direction. 
     The cabinet may be provided with a support pin, the tub may be provided with a guide bar, and each of the plurality of vibration reduction apparatuses may have one end connected to the guide bar so as to be rotatable on the guide bar while moving in a vertical direction along the guide bar, and an other end connected to the support pin so as to be rotatable on the support pin while being restricted from moving in the upper and lower side directions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a view illustrating the external appearance of a washing machine according to an embodiment of the disclosure; 
         FIG. 2  is a side cross-sectional view schematically illustrating main parts of the washing machine of  FIG. 1 ; 
         FIG. 3  is a perspective view schematically illustrating main parts of the washing machine of  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a vibration reduction apparatus installed between a cabinet and a tub of the washing machine of  FIG. 1 ; 
         FIG. 5  is a plan cross-sectional view illustrating the vibration reduction apparatus installed between the cabinet and the tub of the washing machine of  FIG. 1 . 
         FIG. 6  is an enlarged plan cross-sectional view illustrating the vibration reduction apparatus of the washing machine of  FIG. 1 ; 
         FIG. 7  is a view illustrating an operation of the vibration reduction apparatus of the washing machine of  FIG. 1 ; 
         FIG. 8  is a view illustrating an operation of a vibration reduction apparatus of a washing machine according to another embodiment of the disclosure; 
         FIG. 9  is a perspective view schematically illustrating main parts of a washing machine according to still another embodiment of the disclosure; 
         FIG. 10  is a plan cross-sectional view illustrating a vibration reduction apparatus installed between the cabinet and the tub of the washing machine of  FIG. 9 ; 
         FIG. 11  is an exploded view illustrating the vibration reduction apparatus of the washing machine shown in  FIG. 9 ; 
         FIG. 12  is a view illustrating a first rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 ; 
         FIG. 13  is a view illustrating a second rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 ; 
         FIG. 14  is a view illustrating a coupling state of the first rod and the second rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 ; 
         FIG. 15  is a view illustrating an operation of the vibration reduction apparatus of the washing machine shown in  FIG. 9 ; 
         FIG. 16  is a view illustrating a first rod according to another embodiment of the disclosure; 
         FIG. 17  is a plan view and a side exploded view illustrating a disk of the first rod shown in  FIG. 16 ; 
         FIG. 18  is a view illustrating a first state of a vibration reduction apparatus having the first rod shown in  FIG. 16 ; 
         FIG. 19  is a cross-sectional view illustrating the vibration reduction apparatus in a state shown in  FIG. 18 ; 
         FIG. 20  is a view illustrating a second state of the vibration reduction apparatus having the first rod shown in  FIG. 16 ; and 
         FIG. 21  is a cross-sectional view illustrating the vibration reduction apparatus in a state shown in  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments set forth herein and illustrated in the configuration of the disclosure are only the most preferred embodiments and are not representative of the full the technical spirit of the disclosure, so it should be understood that they may be replaced with various equivalents and modifications at the time of the disclosure. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. It is to be understood that the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. It will be further understood that the terms “include”, “comprise” and/or “have” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The terms including ordinal numbers like “first” and “second” may be used to explain various components, but the components are not limited by the terms. The terms are only for the purpose of distinguishing a component from another. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the disclosure. 
     Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a view illustrating the external appearance of a washing machine according to an embodiment of the disclosure.  FIG. 2  is a side cross-sectional view schematically illustrating main parts of the washing machine of  FIG. 1 . 
     Referring to  FIGS. 1 to 2 , a washing machine  1  includes a main body  2 , a tub  20  provided inside the main body  2  and storing washing water, a rotating tub  30  rotatably provided in the tub  20  and accommodating laundry, and a pulsator  40  rotatably provided in the rotating tub  30  to generate washing water. 
     The main body  2  includes a cabinet  11  and a top cover  12  coupled to an upper portion of the cabinet  11 . The top cover  12  is provided with an inlet  13  through which laundry may be injected into the rotating tub  30 , and the inlet  13  may be opened and closed by a door  3 . A control panel  14  for displaying operation information of the washing machine  1  or receiving an operation command may be provided on the top cover  12 . 
     The cabinet  11  may have a box shape. That is, the cabinet  11  may have a front plate  11   a , a rear plate  11   b , a left side plate  11   c , a right-side plate  11   d , and a bottom plate  11   e.    
     The tub  20  is provided in a cylindrical shape with an open top surface to store washing water. The tub  20  may be suspended from the cabinet  11  by a suspension device  6 . The suspension device  6  may be provided at four corners of the cabinet  11 . 
     The suspension device  6  may include a suspension bar  8  elongated in the vertical direction, a suspension cap  7  configured to couple an upper end of the suspension bar  8  to the cabinet  11  and couple a lower end of the suspension bar  8  to the tub  20 , and a spring  9  provided at the lower end of the suspension bar  8  to reduce vibration of the tub  20 . The spring  9  may reduce the vibration of the tub  20  in the vertical direction. 
     A drain hole  21  for draining the washing water stored in the tub  20  to the outside of the tub  20  may be formed in a lower portion of the tub  20 . A drain hose  22  may be connected to the drain hole  21 , and a drain valve  23  may be provided in the drain hose  22  to open and close the drain hose  22 . 
     The rotating tub  30  may be rotatably provided inside the tub  20  and may accommodate laundry. The rotating tub  30  may be formed in a cylindrical shape with an open top surface. A through hole  33  may be formed on the side of the rotating tub  30  to allow washing water to flow in and out. A balancing unit  31  may be installed at an upper portion of the rotating tub  30  to eliminate load imbalance caused by laundry. The balancing unit  31  includes a housing having an annular channel, and a ball or a fluid mass provided to be movable inside the channel, and as the ball or fluid moves according to rotation of the rotating tub  30 , load imbalance of the rotating tub  30  may be resolved. 
     The pulsator  40  may be rotatably provided on a lower portion of the rotating tub  30  to generate washing water current. Laundry may be washed by the washing water generated by the pulsator  40 . 
     The washing machine  1  includes a water supply device  4  for supplying washing water into the tub  20 . The water supply device  4  may include a water supply pipe connected to an external water supply source to guide washing water to the tub  20 , and a water supply valve provided in the water supply pipe to regulate water supply. 
     The washing machine  1  may include a detergent supply device  5  for supplying detergent. Washing water supplied through the water supply device  4  is provided to pass through the detergent supply device  5  so that detergent may be supplied to the tub  20  together with the washing water. 
     The washing machine  1  includes a driving device for rotating the rotating tub  30  and the pulsator  40 . 
     The driving device may include a motor  50  that converts electric force into a mechanical rotational force, and a shaft system that transmits the driving force of the motor  50  to the pulsator  40  and the rotating tub  30 . 
     The motor  50  may include a stator  51  held stationary and a rotor  52  rotating by electromagnetically interacting with the stator  51 . 
     The shaft system includes a dehydration shaft  59  provided to transmit the driving force of the motor  50  to the rotating tub  30 , a washing shaft  58  provided to transmit the driving force of the motor  50  to the pulsator  40 , and a clutch device  53  connecting or disconnecting the motor  50  to or from the dehydration shaft  59 . 
     The dehydration shaft  59  may be formed to have a hollow, and the washing shaft  58  may be provided in the hollow of the dehydration shaft  59 . The washing shaft  58  may be kept connected to the rotor  52  of the motor  50 , and the dehydration shaft  59  may be connected to or disconnected from the rotor  52  of the motor  50  by the clutch device  53 . 
     When the clutch device  53  disconnects the dehydration shaft  59  from the motor  50 , power is transmitted only to the washing shaft  58  to rotate only the pulsator  40 , and when the clutch device  53  connects the dehydration shaft  59  to the motor  50 , power is transmitted both the dehydration shaft  59  and the washing shaft  58  to rotate the rotating tub  30  and the pulsator  40  at the same time. 
     When only the pulsator  40  is rotated, a washing water current is generated by the rotation of the pulsator  40 , and the laundry is rotated by the generated washing water current to be brought into friction with the rotating tub  30 , so that washing of the laundry is performed. When the pulsator  40  and the rotating tub  30  rotate at the same time, the laundry inside the rotating tub  30  is rotated and moisture of the laundry is separated by centrifugal force, so that the laundry is dehydrated. 
     The clutch device  53  includes an actuator  54  generating a driving force for power switching, a rod  55  linearly moving by the operation of the actuator  54 , a lever  56  connected to the rod  55  to rotate, and a coupling  57  coupled to the dehydration shaft  59  to ascend and descend according to the operation of the lever  56 . When the coupling  57  descends, the coupling  57  may be connected to the rotor  52  so that the driving force of the motor  50  may be transmitted to the dehydration shaft  59 , and when the coupling  57  ascends, the coupling  57  may be separated from the rotor  52  so that the driving force of the motor  50  may not be transmitted to the dehydration shaft  59 . 
     During the dehydration operation, the rotating tub  30  may rotate at a high speed, and in this case, the rotating tub  30  may perform a precession according to the weight imbalance of laundry contained in the rotating tub  30 . The precession of the rotating tub  30  may cause vibration in the tub  20 . The tub  20  may vibrate in the vertical and horizontal directions. 
     The above-described suspension device  6  may reduce the vibration in the vertical direction of the tub  20  by the suspension bar  8  formed elongated in the vertical direction and the spring  9  provided at the lower end of the suspension bar  7 . However, the suspension device  6  may not effectively reduce the vibration of the tub  20  in the horizontal direction. 
     The washing machine according to the embodiment of the disclosure may include vibration reduction apparatuses ( 60  and  70  in  FIG. 3 ) provided to reduce vibration of the tub  20 . The vibration reduction apparatuses  60  and  70  may effectively reduce the vibration of the tub  20  in the horizontal direction. The vibration reduction apparatuses  60  and  70  may be installed between the cabinet  11  and the tub  20 . 
     Since the vibration reduction apparatuses  60  and  70  are installed irrespective of the suspension device  6  as such, no force is applied to the suspension device  6  and deformation of the suspension device  6  may be prevented. A guide bar mount  15  is provided on the cabinet  70  to install the vibration reduction apparatuses  60  and  70 , and a support pin mount  24  is provided on the tub  20  to install the vibration reduction apparatuses  60  and  70 . 
     Hereinafter, the vibration reduction apparatuses  60  and  70  of the disclosure will be described in detail. 
       FIG. 3  is a perspective view schematically illustrating main parts of the washing machine of  FIG. 1 .  FIG. 4  is a perspective view illustrating a vibration reduction apparatus installed between a cabinet and a tub of the washing machine of  FIG. 1 .  FIG. 5  is a plan cross-sectional view illustrating the vibration reduction apparatus installed between the cabinet and the tub of the washing machine of  FIG. 1 .  FIG. 6  is an enlarged plan cross-sectional view illustrating the vibration reduction apparatus of the washing machine of  FIG. 1 .  FIG. 7  is a view illustrating an operation of the vibration reduction apparatus of the washing machine of  FIG. 1 . 
     Referring to  FIGS. 3 to 7 , the vibration reduction apparatus  60  and  70  may include a first vibration reduction apparatus  60  and a second vibration reduction apparatus  70 . The structures of the first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be the same. 
     The first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be provided to be extended and contracted along the length direction thereof. The first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may damp vibration by extending and contracting operations. 
     The first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be installed to be parallel with a bottom plate  12   e  of the cabinet  11 . The first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be disposed such that the longitudinal central axis of the first vibration reduction apparatus  60  and the longitudinal central axis of the second vibration reduction apparatus  70  are in alignment with each other on the same line (CL in  FIG. 5 ). 
     Since the suspension device  6  is connected to the lower part of the tub  20 , the first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be connected to the upper part of the tub  20  to balance the upper and lower parts of the tub  20 . 
     The first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be installed between the tub  20  and the rear plate  11   b  of the cabinet  11  so as to be parallel with the rear plate  11   b  of the cabinet  11 . 
     With such a structure, the vibration of the tub  20  may be efficiently and uniformly reduced with a minimum number of the vibration reduction apparatuses  60  and  70 . 
     However, unlike the embodiment, the first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be installed between the tub  20  and the front plate  11   a  of the cabinet  20  to be in parallel with the front plate  11   a  of the cabinet  11 . 
     Alternatively, the first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be installed between the tub  20  and the left side plate  11   c  of the cabinet  11  to be in parallel with the left side plate  11   c  of the cabinet  11 . 
     Alternatively, the first vibration reduction apparatus  60  and the second vibration reduction apparatus  70  may be installed between the tub  20  and the right-side plate  11   d  of the cabinet  11  to be in parallel with the right-side plate  11   d  of the cabinet  11 . 
     The cabinet  11  may include a guide bar mount  15  protruding from the rear plate  11   b  of the cabinet  11  and a guide bar  16  supported by the guide bar mount  15  to install the vibration reduction apparatuses  60  and  70 . The guide bar  16  may be formed to be elongated in the vertical direction, and may guide the vibration reduction apparatuses  60  and  70  to move in the vertical direction along the guide bar  16 . 
     The tub  20  may include a support pin mount  24  protruding from the tub  20  and a support pin  25  supported on the support pin mount  24  to install the vibration reduction apparatuses  60  and  70 . The support pin mount  24  may restrict the vibration reduction apparatuses  60  and  70  from moving in the vertical direction with respect to the support pin mount  24 . 
     The first vibration reduction apparatus  60  may include a cylinder  61  having an inner space  62  and a piston  66  provided in the inner space  62  of the cylinder  61  to advance and retreat. 
     The cylinder  61  may be provided with a connecting ring  64  and may be connected to the tub  20  in such a manner that the support pin  25  of the tub  20  is inserted into the connecting ring  64 . The connecting ring  64  of the cylinder  61  may be configured to come in close contact between a pair of support pin mounts  24  to restrict the connecting ring  64  of the cylinder  61  from moving in the vertical direction with respect to the support pin  25 . Accordingly, the first vibration reduction apparatus  60  may perform a rotational movement on the support pin  25  while being restricted form performing the vertical movement or horizontal movement with respect to the support pin  25 . 
     The piston  66  may be provided with a connecting ring  67  and may be connected to the cabinet  11  in a such manner that the guide bar  16  of the cabinet  11  is inserted into the connecting ring  67 . The connecting ring  67  of the piston  66  may move up and down in a predetermined range along the guide bar  16 . Therefore, the first vibration reduction apparatus  60  may perform rotational motion and an upward and downward motion with respect to the guide bar  16  while being restricted from performing horizontal motion with respect to the guide bar  16 . 
     Friction between the piston  66  and the cylinder  61  generated while the piston  66  advances and retracts in the inner space  62  of the cylinder  61  may damp vibration of the tub  20 . However, a friction member  63  may be provided in the inner space  62  of the cylinder  61  to increase the frictional force. The friction member  63  may be formed of polyurethane or rubber. 
     Referring to  FIG. 7 , the operation of the vibration reduction apparatuses  60  and  70  will be described in brief. 
     When vibration occurs in the tub  20  according to rotation of the rotating tub  30 , the pistons  66  and  76  of the vibration reduction apparatuses  60  and  70  may advance and retract in the cylinders  61  and  71 . The frictional force generated during the advance and retracting of the pistons  66  and  76  may reduce the vibration of the tub  20 . 
     When the tub  20  moves in the vertical direction, the vibration reduction apparatuses  60  and  70  may move together in the vertical direction along the guide bar  16 , and so that the vibration reduction apparatuses  60  and  70  may be maintained in a horizontal state and efficiently reduce the horizontal vibration of the tub  20 . 
       FIG. 8  is a view illustrating an operation of a vibration reduction apparatus of a washing machine according to another embodiment of the disclosure. 
     The same reference numerals are assigned to the same configurations as those in the above-described embodiment, and detailed description thereof may be omitted. 
     Unlike the above-described embodiment, a guide bar  27  and a guide bar mount  26  may be provided on the tub  20 , and a support pin and a support pin mount  17  may be provided on the cabinet  11 . 
     Therefore, the cylinder connecting rings  64  and  74  of the vibration reduction apparatuses  60  and  70  may be connected to the guide bars  27 , and the piston connecting rings  67  and  77  of the vibration reduction apparatuses  60  and  70  may be connected to the support pins. 
       FIG. 9  is a perspective view schematically illustrating main parts of a washing machine according to still another embodiment of the disclosure.  FIG. 10  is a plan cross-sectional view illustrating a vibration reduction apparatus installed between the cabinet and the tub of the washing machine of  FIG. 9 .  FIG. 11  is an exploded view illustrating the vibration reduction apparatus of the washing machine shown in  FIG. 9 .  FIG. 12  is a view illustrating a first rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 .  FIG. 13  is a view illustrating a second rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 .  FIG. 14  is a view illustrating a coupling state of the first rod and the second rod of the vibration reduction apparatus of the washing machine shown in  FIG. 9 .  FIG. 15  is a view illustrating an operation of the vibration reduction apparatus of the washing machine shown in  FIG. 9 . 
     Referring to  FIGS. 9 to 15 , a washing machine and a vibration reduction apparatus provided therein according to still another embodiment of the disclosure will be described. The same reference numerals are assigned to the same configurations as those in the above-described embodiment, and detailed description thereof may be omitted. 
     A washing machine  300  includes a cabinet  11  forming the external appearance, a tub  20  disposed inside the cabinet  11 , a rotating tub  30  rotatably disposed inside the tub  20 , a suspension device  6  connecting the tub  20  to the cabinet  11  so that the tub  20  is supported by the cabinet  11 , and a vibration reduction apparatus  80  installed between the tub  20  and the suspension device  6  to reduce vibration of the tub  20  according to rotation of the rotating tub  30 . 
     The suspension device  6  is installed at each of the four corners of the cabinet  11 , and the vibration reduction apparatus  80  may be connected to each of the suspension devices  6 . 
     The vibration reduction apparatus  80  may include a first rod  81  and a second rod  91  that are rotatably coupled to each other. 
     The first rod  81  may include a tub connection portion  82  connected to the tub  20 , a first hinge portion  85  rotatably coupled to the second rod  91 , and a first rod body  84  connecting the tub connection portion  82  to the first hinge portion  85 . 
     The tub connection portion  82  may have an insertion hole  83  and may be coupled to the tub  20  in such a manner that a shaft  29  provided in the tub  20  is inserted into the insertion hole  83 . A shaft mount  28  may protrude from the tub  20 , and may be provided with an insertion hole  28   a  into which the shaft  29  is inserted. The shaft  29  may include a head portion  29   a  formed at an end of the shaft  29  and a locking protrusion  29   b  protruding from the outer circumferential surface of the shaft  29  so as to be fixed in a state inserted into the insertion hole  28   a . The first rod  81  may be rotatable about the shaft  29 . 
     The first hinge portion  85  may include a disk  87  and a hinge pin  86  protruding from the disk  87 . 
     The disk  87  may be formed in a cylindrical shape having an upper surface  88 , a lower surface  89 , and a circumferential surface  90 . The hinge pin  86  may be formed to protrude from the centers of the upper surface  88  and the lower surface  89 . 
     The second rod  91  includes a second hinge portion  92  rotatably coupled to the first hinge portion  85  of the first rod  81 , a suspension device connection portion  101  provided to be connected to the suspension device  6 , and a second rod body  100  connecting the second hinge portion  92  to the suspension device connection portion  101 . 
     The second hinge portion  92  may include a disk housing  93  into which the disk  87  is inserted. The disk housing  93  may include a first wall  95 , a second wall  96 , and a slot  97  formed between the first wall  95  and the second wall  96  so that the disk  87  is inserted into the slot  97 . A hinge pin insertion hole  94  into which the hinge pin  86  is inserted may be formed in the first wall  95  and the second wall  96 . 
     A friction member  99  may be provided inside the disk housing  93  to generate a friction force by coming in friction with the disk  87  when the first hinge portion  85  and the second hinge portion  92  rotate. The friction member  99  may be formed of polyurethane or rubber. 
     A mounting rib  98  protruding to mount the friction member  99  may protrude on at least one of an inner surface  95   a  of the first wall  95  and an inner surface  96   a  of the second wall  96  of the disk housing  93 . The friction member  99  may be fitted between the mounting ribs  98  and coupled. 
     However, unlike the embodiment, the friction member  99  may be omitted. Instead of the friction member  99 , the inner surface  95   a  of the first wall  95  of the disk housing  93  may be provided to come in close contact with the upper surface  88  of the disk  87 , and the inner surface  96   a  of the second wall  96  may be provided to come in close contact with the lower surface  89  of the disk  87 , so that the disk housing  93  and the disk  87  may directly come in friction with each other. 
     The suspension device connection portion  101  may include a holder  104  having a connection groove  105  into which the suspension bar  7  is inserted, and a bracket  102  to which the holder  104  is rotatably coupled. The holder  104  includes a rotation pin  106  so that the holder  104  is rotatably coupled to the bracket  102 , and a pin receiving portion  103  in which the rotation pin  106  is accommodated may be formed in the bracket  102 . 
     With such a configuration, the suspension device connection portion  101  may move in the vertical direction along the suspension bar  7 . 
     Referring to  FIG. 15 , the operation of the vibration reduction apparatus  80  will be described in brief. 
     When vibration occurs in the tub  20  according to rotation of the rotating tub  30 , the suspension device connection portion  101  of the second rod  91  moves in the vertical direction along the suspension bar  7  and the second rod  91  may rotate around the hinge pin  86 . 
     The frictional force generated between the disk  87  and the friction member  99  during rotation of the second rod  91  may reduce vibration of the tub  20 . 
     For example, when displacement occurs in +X direction in the tub  20 , the suspension device connection portion  101  may descend in direction C, and the second rod  91  may rotate in direction A in which the angle between the second rod  91  and the first rod  81  increases. As the second rod  91  rotates, a friction force is generated between the disk  87  and the friction member  99 , so that the displacement of the tub  20  may be reduced. 
     When displacement occurs in −X direction in the tub  20 , the suspension device connection portion  101  may ascend in direction D, and the second rod  91  may rotate in direction B where the angle between the second rod  91  and the first rod  81  decreases. As the second rod  91  rotates, a friction force is generated between the disk  87  and the friction member  99 , so that the displacement of the tub  20  may be reduced. 
     As such, the vibration reduction apparatus  80  damps the horizontal vibration of the tub  20  through rotational motion of the first rod  81  and the second rod  91 , thereby efficiently reducing the vibration without applying an excessive force to the suspension device  6 . 
       FIG. 16  is a view illustrating a first rod according to another embodiment of the disclosure.  FIG. 17  is a plan view and a side exploded view illustrating a disk of the first rod shown in  FIG. 16 .  FIG. 18  is a view illustrating a first state of a vibration reduction apparatus having the first rod shown in  FIG. 16 .  FIG. 19  is a cross-sectional view illustrating the vibration reduction apparatus in a state shown in  FIG. 18 .  FIG. 20  is a view illustrating a second state of the vibration reduction apparatus having the first rod shown in  FIG. 16 .  FIG. 21  is a cross-sectional view illustrating the vibration reduction apparatus in a state shown in  FIG. 20 ; 
     Referring to  FIGS. 16 to 21 , a first rod according to still another embodiment of the disclosure will be described. The same reference numerals are assigned to the same configurations as those in the above-described embodiment, and detailed description thereof may be omitted. 
     Typically, when the rotational speed of the rotating tub  30  is about 100 rpm, excessive vibration occurs in the tub  20  due to resonance, and when the rotational speed reaches the highest rpm (about 250 rpm), the vibration of the tub  20  decreases. A general vibration reduction apparatus exerts a damping force on the tub  20  in all rpm sections, and the corresponding reaction force may cause vibration to be transmitted to the cabinet  20  even in a section where small vibrations occur in the tub  20 . 
     The vibration reduction apparatus  80  according to the embodiment of the disclosure exerts a damping force on the tub  20  in a transient vibration section where resonance occurs to reduce the vibration of the tub  20  while exerts a small or no damping force on the tub in a section where vibration of the tub  20  is small, such as the highest rpm section, to prevent the vibration of the tub  20  from being transmitted to the cabinet  11 . 
     To this end, the disk  87  of the first rod  81  may include a portion that differs in thickness so that the frictional force is varied according to the rotation angle of the second rod  91 . Specifically, the disk  87  of the first rod  81  may include a thickness increasing portion  110  whose thickness increases so as to increase frictional force when the rotation angle of the second rod  91  increases. 
     When the second rod  91  rotates at a large angle and thus the friction member  99  reaches the thickness increasing portion  110  of the disk  87 , the frictional force between the friction member  99  and the disk  87  may be increased. Conversely, when the friction member  99  does not reach the thickness increase portion  110  of the disk  87 , the frictional force between the friction member  99  and the disk  87  may not be large or may not occur. 
     When a portion excluding the thickness increasing portion  110  has a thickness of T 1 , the thickness increasing portion  110  may have a maximum thickness of T 2  greater than T 1 . The thickness increasing portion  110  may have a thickness that gradually increases along the circumferential direction of the disk  87  before one point to remain constant, and then from another point gradually decreases. 
     The thickness increasing portion  100  may include an inclined portion  111  whose thickness gradually increases or decreases along the circumferential direction of the disk  87  and a step portion  112  whose thickness is kept constant. The surface of the inclined portion  111  may be formed in a flat shape or may be smoothly formed in a curved shape. However, unlike the embodiment, the step portion  112  is omitted, and the thickness increase portion  110  may be formed to have a thickness that gradually increases along the circumferential direction of the disk  87  and at one point, gradually decreases along the circumferential direction of the disk  87 . 
     Referring to  FIGS. 18 to 21 , the operation of the vibration reduction apparatus  80  will be briefly described. 
       FIGS. 18 and 19  are views illustrating a state (the first state) of the vibration reduction apparatus when no vibration or small vibration occurs in the tub  20 , and  FIGS. 20 and 21  views illustrating a state (the second state) of the vibration reduction apparatus when excessive vibration occurs in the tub  20 . 
     In the first state, the friction member  99  of the second rod  91  may come in friction with a portion other than the thickness increasing portion  110  of the disk  87 . Therefore, a relatively small frictional force may be generated. 
     Alternatively, in the first state, the friction member  99  of the second rod  91  may be provided to be spaced apart from the disk  87  without making friction with the disk  87 . In this case, since frictional force may not be generated, vibration of the tub  20  may not be transmitted to the cabinet  11  through the vibration reduction apparatus  80 . 
     In the second state, the friction member  99  may come in friction with the thickness increasing portion  110  of the disk  87 . Therefore, a relatively large frictional force may occur. 
     As is apparent from the above, the vibration reduction apparatus can effectively reduce the vibration of the tub that occurs during rotation of the rotating tub. 
     According to the aspect of the disclosure, the vibration reduction apparatus is not connected to the suspension device, or is connected to the suspension device with a small force applied to the suspension device, so that the suspension device can be prevented from being deformed. 
     According to the aspect of the disclosure, the vibration reduction apparatus effectively reduces vibration of the tub in a transient vibration section in which the vibration of the tub is large due to resonance, and prevents vibration of the tub from being transmitted to the cabinet in a section in which the vibration of the tub is in a stead state, such as the highest rpm section, as in the case of having no vibration reduction apparatus. 
     Although few embodiments of the disclosure have been shown and described, the above embodiment is illustrative purpose only, and it would be appreciated by those skilled in the art that changes and modifications may be made in these embodiments without departing from the principles and scope of the disclosure, the scope of which is defined in the claims and their equivalents.