Patent Publication Number: US-9839944-B2

Title: Dishwasher and control method thereof

Description:
This application claims the benefit of Korean Patent Application No. KR10-2014-0071650, filed Jun. 12, 2014 which is hereby incorporated by reference as if fully set forth herein. 
     FIELD 
     The present disclosure relates to a dishwasher and a control method of a dishwasher. 
     BACKGROUND 
     A dishwasher is an apparatus to remove garbage, such as leftover food, from dishes or cooking utensils (hereinafter, “objects to be washed”) using a detergent and washing water. 
     In general, a dishwasher includes a tub providing a washing space, dish racks provided within the tub so as to receive objects to be washed, spray arms to spray washing water to the racks, a sump to store washing water therein, and supply paths to supply the washing water stored in the sump to the spray arms. 
     The dishwasher including the above elements may remove garbage from objects to be washed, which are received in the racks, by spraying washing water to the objects to be washed according to a washing course selected by a user, and dry the objects to be washed, from which garbage has been removed, through hot air. 
     SUMMARY 
     According to an innovative aspect of the subject matter described in this application, a control method of a dishwasher configured to spray washing water to objects to be washed that the dishwasher including at least two flow paths having different flow rates, a chamber having communication holes that each communicate with a respective flow path, a water supply pump configured to supply washing water to the chamber through an impeller rotated by a motor, and a flow path switching unit located within the chamber and configured to sequentially open the communication holes based on washing water being supplied to the chamber, the control method includes the actions of measuring an amount of current supplied to the motor while the motor rotates the impeller to supply washing water to the chamber; and determining a position of the flow path switching unit by comparing the amount of current supplied to the motor with reference current amounts that are each designated as an amount of current supplied to the motor when the motor rotates the impeller to supply washing water to the respective flow path. 
     The method may include one or more of the following optional features. The method includes the action of notifying a user of malfunction of the dishwasher, based on the amount of current supplied to the motor not being equal to any of the reference current amounts. The action of notifying the user of the malfunction of the dishwasher includes notifying the user through an alarm unit located in the dishwasher by at least one of displaying a character signal on a display of the alarm unit or outputting a sound signal using a speaker of the alarm unit. Based on the amount of current supplied to the motor not being equal to a reference current amount for position judgment that is designated as one of the reference current amounts, the method includes the actions of intercepting, for measurement, power supplied to the motor; and measuring a second amount of current supplied to the motor while the motor rotates the impeller to supply washing water to the chamber by resupplying power to the motor. The method includes the action of repeating the interception and the measurement of the second amount of current until an amount of current measured in the measurement of the second amount of current is equal to the reference current amount for position judgment. A largest current amount and a smallest current amount of the reference current amounts are designated as reference current amounts for position judgment. The action of measuring the amount of current supplied to the motor includes measuring the amount of current supplied to the motor after a predetermined time from supplying power to the motor has elapsed. Each of the reference current amounts is a range having a maximum current amount and a minimum current amount. 
     According to another innovative aspect of the subject matter described in this application a control method of a dishwasher configured to spray washing water to objects to be washed the dishwasher including three flow paths with a first flow path having a different flow rate than a second flow path and a third flow path, a chamber having three communication holes that each communicate with a respective flow path, a water supply pump configured to supply washing water to the chamber through an impeller rotated by a motor, and a flow path switching unit located within the chamber and configured to sequentially open the communication holes based on washing water being supplied to the chamber, the control method includes the actions of measuring an amount of current supplied to the motor while the motor rotates the impeller to supply washing water to the chamber by supplying power to the motor; and determining at least one of a state of the flow path switching unit or a position of the flow path switching unit by comparing the amount of current supplied to the motor with reference current amounts that are each designated as an amount of current supplied to the motor when the motor rotates the impeller to supply washing water to the respective flow paths. 
     The method may include one or more of the following optional features. The actions further include notifying a user of malfunction of the dishwasher through an alarm unit located in the dishwasher by at least one of displaying a character signal on a display of the alarm unit or outputting a sound signal using a speaker of the alarm unit, based on the amount of current supplied to the motor not being equal to any of the reference current amounts. Based on the amount of current supplied to the motor is not being equal to a reference current amount for position judgment that is designated as one of the reference current amounts, the actions further include intercepting, for measurement, power supplied to the motor; and measuring a second amount of current resupplied to the motor while the motor rotates the impeller to supply washing water to the chamber by resupplying power to the motor. The actions further include repeating the interception and the measurement of the second amount of current until the amount of current measured in the measurement of the second amount of current is equal to the reference current amount for position judgment. The reference current amount for position judgment is designated as an amount of current supplied to the motor when the motor rotates the impeller to supply washing water to the first flow path. Each of the reference current amounts is a range having a maximum current amount and a minimum current amount. The action of measuring the amount of current supplied to the motor includes measuring the amount of current supplied to the motor after a predetermined time from supplying power to the motor has elapsed. 
     An object of the subject matter described in this application is to provide a dishwasher having improved washing ability and a control method thereof. 
     Another object of the subject matter described in this application is to provide a dishwasher in which a plurality of washing water flow paths is provided on one spray arm to spray washing water, and a control method thereof. 
     Another object of the subject matter described in this application is to provide a dishwasher having a flow path switching unit to selectively open a plurality of flow paths provided on one spray arm, and a control method thereof. 
     Yet another object of the subject matter described in this application is to provide a dishwasher which may judge the position a flow path switching unit and the state of the flow path switching unit, and a control method thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of an example dishwasher. 
         FIG. 2  is a view of an example upper arm, lower arm, and tower flow path of a dishwasher. 
         FIGS. 3A and 3B  are exploded perspective views of an example tower flow path and lower arm. 
         FIGS. 4A and 4B  are views of an example lower arm and lower arm chamber. 
         FIGS. 5A, 5B, 6A, and 6B  are perspective views of an example support body and switching unit body of a flow path switching unit. 
         FIGS. 7A (a),  7 A(b),  7 B(a),  7 B(b), and  8 A to  8 C are views of an example operation process of a flow path switching unit. 
         FIGS. 9A to 9C  are exploded views of an example upper arm. 
         FIGS. 10A and 10B  are views of an example upper arm flow path switching unit of an upper arm. 
         FIGS. 11A to 11D  are views of an example operation process of the upper arm flow path switching unit. 
         FIG. 12  is a flowchart of an example control method of a dishwasher. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example dishwasher. Dishwasher  100  includes a cabinet  1  forming the external appearance of the dishwasher  100 , a tub  11  located within the cabinet  1  and providing a washing space, a sump  13  located under the tub  11  and storing washing water therein (e.g., a unit to recover the washing water in the tub), a cover  15  located on the sump  13  to divide the tub  11  and the sump  13  from each other, and a door  16  provided on the cabinet  1  to open and close the washing space. 
     The sump  13  receives washing water through a sump water supply path  131 , washing water in the sump  13  is discharged to the outside of the sump  13  through a sump drain path  133 , and washing water sprayed to the inside of the tub  11  through spray arms  6 ,  7 , and  8 , which will be described alter, is recovered to the sump  13  through recovery holes  151  provided on the cover  15 . 
     Racks to receive objects to be washed, such as dishes, are provided in the tub  11 . The racks may include a first rack  191  and a second rack  193  located below the first rack  191  and, for convenience of description, the first rack  191  is referred to as an upper rack and the second rack  193  is referred to as a lower rack. 
     The upper rack  191  and the lower rack  193  may be withdrawn from the tub  11  when the door  16  opens the washing space. For this purpose, rails  111  may be provided on the inner surface of the tub  11  from the rear surface to the front surface of the dishwasher  100  having the door  16  and wheels  1911  and  1931  to support the respective racks  191  and  193  may be provided on the upper rack  191  and the lower rack  193 . 
     Further, the dishwasher  100  may include a lower arm  6  provided within the tub  11  to wash objects to be washed, received in the lower rack  193 , an upper arm  7  to wash objects to be washed, received in the upper arm  191 , and a top nozzle  8  located above the upper arm  7  and supplying washing water to the upper rack  191  and the lower rack  193 . 
     The lower arm  6 , the upper arm  7 , and the top nozzle  8  may be provided to supply washing water through a water supply pump  18  and a supply path unit  2 . 
     The supply path unit  2  may include a first supply path  21  connected to the lower arm  6  through an arm holder  17 , a second supply path  23  connected to the upper arm  7 , a third supply path  25  connected to the top nozzle  8 , and a supply path switching valve  27  to selectively open the respective supply paths  21 ,  23  and  25 . 
     The water supply pump  18  may include a housing  181  having an impeller  186  provided therein, an inlet part  183  connecting the housing  181  to the sump  13 , an outlet part  182  connecting the housing  181  to the supply path switching valve  27 , and a motor  187  provided at the outside of the housing  181  to rotate the impeller  186 . 
     Therefore, when power is supplied to the motor  187  and the impeller  186  is rotated, water introduced from the sump  13  to the housing  181  moves to the supply path switching valve  27  through the outlet part  182 , and the water supplied to the supply path switching valve  27  is supplied to the supply arms  6  and  7  or the top nozzle  8  through the supply paths  21 ,  23 , and  25  opened by the supply path switching valve  27 . 
     The supply path switching valve  27  may be provided to sequentially open the respective supply paths  21 ,  23 , and  25  or to simultaneously open at least two of the three supply paths  21 ,  23 , and  25 . The supply path switching valve  27  may have any structure which may perform such a function. 
     In some implementations, since objects to be washed, received in the lower rack  193 , may be washed through the lower arm  6  and objects to be washed, received in the upper rack  192 , may be washed through a tower flow path  3 , which will be described later, the above-described upper arm  7  and top nozzle  8  may be omitted. If the upper arm  7  and top nozzle  8  are not provided in the tub  11 , the height of the dishwasher  100  may be minimized. 
     In some implementations, the dishwasher  100  may further include the tower flow path  3  detachably provided on the lower rack  193  and extending in the direction of the upper rack  191  and a tower attachable unit  5  withdrawn from the lower arm  6  according to hydraulic pressure in the lower arm  6  and connected to the tower flow path  3  to supply washing water to the tower flow path  3 . 
     As shown in  FIG. 2 , the tower flow path  3  is fixed to a tower support unit  4  and the tower support unit  4  is detachably fixed to the lower rack  193 . That is, the tower flow path  3  may be detachably attached to the lower rack  193  through the tower support unit  4 . 
     The tower flow path  3  may include a body  31  fixed to the tower support unit  4  and a spray nozzle  33  to spray washing water supplied through the body  31  to the upper rack  191 . 
     The body  31  may have a cylindrical shape, the upper and lower surfaces of which are opened, the spray nozzle  33  is combined with the upper surface of the body  31 , and the tower support unit  4  is combined with the lower surface of the body  31 . 
     The body  31  may have a structure, the diameter of which is decreased in the upward direction and such a structure serves to move washing water introduced through the lower surface of the body  31  to the spray nozzle  31  while maintaining a designated hydraulic pressure. 
     As shown in  FIG. 3A , the spray nozzle  33  may include a connection pipe  331  combined with the upper surface of the body  31  and a plurality of spray holes  333  to discharge washing water, introduced into the spray nozzle  33  through the connection pipe  331 , to the outside of the spray nozzle  33 . 
     The connection pipe  331  may combine the body  31  with the spray nozzle  33  such that the spray nozzle  33  may be rotated, and the spray holes  333  may be provided such that the spray nozzle  33  may be rotated by repulsive force of washing water discharged from the spray nozzle  33 . 
     That is, the spray holes  333  may be disposed on the upper surface of the spray nozzle  33  in a spiral shape and provided to rotate the spray nozzle  33  in the clockwise direction or the counterclockwise direction when the spray holes  333  spray washing water. 
     The tower support unit  4  may include a fixing body  42  to which the body  31  of the tower flow path  3  is fixed and a connector  45  provided on the fixing body  42  so that the tower attachable unit  5  withdrawn from the lower arm  6  is connected to the connector  45 . 
     The fixing body  42  may include a fixing body through hole  421  and rack combination parts  423 . 
     The fixing body through hole  421  may be formed through the fixing body  42  and the rack combination parts  423  may have any shape which may detachably combine the fixing body  42  with the lower rack  193 . 
     The connector  45  may include a connector body  451  having a cylindrical shape inserted into the fixing body through hole  421 , a reception hole  455  formed through the connector body  451  and communicating with the body  31  of the tower flow path  3 , and a connector flange  453  protruding from the circumferential surface of the connector body  451 . 
     The connector flange  453  is supported by a flange arrival groove  425  protruding from the circumferential surface of the fixing body through hole  421  toward the center of the fixing body through hole  421 . 
     The diameter of the connector body  451  is smaller than the diameter of the fixing body through hole  421  and the diameter of the connector flange  453  is greater than the diameter of the fixing body through hole  421  and smaller than the diameter of the flange arrival groove  425 . 
     Therefore, the connector flange  453  may be arrived in the flange arrival groove  425  and prevent the connector body  451  from being withdrawn from the fixing body  42  through the fixing body through hole  421 , and the connector body  421  may move within the fixing body through hole  421 . 
     That is, since the connector body  451  may move within the fixing body through hole  42  in a radial manner, if the center of an attachable unit body  511  does not coincide with the center of the reception hole  455  by the position of the lower rack  193  or, if the lower rack  6  is rotated while not level, the tower attachable unit  5  and the reception hole  455  may be easily combined. 
     The tower attachable unit  5  withdrawn from the lower arm  6  to supply washing water to the tower flow path  3  includes the attachable unit body  511  provided on the lower arm  6 . 
     The attachable unit body  511  is withdrawn from the lower arm  6  according to the pressure, such as hydraulic pressure, within a lower arm chamber  69 , which will be described later, and connected to the reception hole  455  of the tower support unit  4  and, when the attachable unit body  511  is connected to the reception hole  455 , washing water is supplied to the tower flow path  3  and a detailed description thereof will be given later in detail. 
     The attachable unit body  511  may have a cylindrical shape, the upper and lower surfaces of which are opened. The attachable unit body  511  includes a body through hole  515  formed through the center of the attachable unit body  511  and provided in the height direction of the attachable unit body  511 , and an attachable unit flange  513  protruding from the circumferential surface of the attachable unit body  511 . 
     The attachable unit flange  513  prevents the attachable unit body  511  from being withdrawn from the lower arm  6 . For this purpose, the diameter of the outer circumferential surface of the attachable unit flange  513  is greater than the diameter of a first discharge hole  631  provided on the lower arm  6 . 
     A guider support part  517 , referring to  FIGS. 7A (a),  7 A(b),  7 B(a), and  7 B(b), protruding to the center of the body through hole  515  may be further provided on the upper surface of the attachable unit body  511 . The guider support part  517  assists movement of the attachable unit body  511  and a detailed description thereof will be given later. 
     In some implementations, the lower arm  6  may include the lower arm chamber  69  supported by the arm holder  17  so as to be rotatable, a lower frame  65  having arm flow paths F 1 , F 2 , and F 3  communicating with the lower arm chamber  69 , and an upper frame  63  provided with discharge holes  631 ,  633 , and  635  to discharge washing water introduced into the arm flow paths F 1 , F 2 , and F 3  to the outside of the lower arm  6 , which may be towards the lower rack. 
     The lower frame  65  includes a chamber communication hole  651  to which the lower arm chamber  69  is connected, and diaphragms  652 ,  653 ,  654 , and  655  dividing the inner space of the lower frame  65  to form the arm flow paths F 1 , F 2  and F 3 . 
     The arm flow paths F 1 , F 2 , and F 3  provided in the lower arm  6  may include a first flow path F 1 , second flow paths F 2  and third flow paths F 3 . The first flow path F 1  is formed by the first diaphragm  652  and the second diaphragm  653  and the second flow paths F 2  and the third flow paths F 3  are divided by the third diaphragm  654  and the fourth diaphragm  655 . 
     The first diaphragm  652  and the second diaphragm  653  are provided to divide the chamber communication hole  651  into three regions. 
     As shown in  FIG. 3B , the first diaphragm  652  may include a first flange  6521  located within the chamber communication hole  651  and a first rib  6523 , a second rib  6524  and a third rib  6525  fixing the first flange  6521  to the lower frame  65 . 
     The second diagram  653  may include a second flange  6531  provided within the chamber communication hole  651  opposite the first flange  6521  and a fourth rib  6533 , a fifth rib  6534  and a sixth rib  6535  fixing the second flange  6531  to the lower frame  65 . 
     The first flange  6521  and the second flange  6531  need to be provided so that the attachable unit flange  513  may pass through the first flow path F 1  formed by the first flange  6521  and the second flange  6531 , and  FIG. 3B  illustrates the first flange  6521  and the second flange  6531  as having the same radius of curvature. A distance between the first flange  6521  and the second flange  6531  is greater than the diameter of the outer circumferential surface of the attachable unit flange  513 . 
     The first rib  6523  and the third rib  6525  fix both ends of the first flange  6521  to the lower frame  65 , and the second rib  6524  protrudes from the first flange  6521  to divide a space formed by the first rib  6523  and the third rib  6525  into two parts. 
     When the chamber communication hole  651  formed between the first rib  6523  and the third rib  6525  is divided into two parts by the second rib  6524 , one part becomes a second communication hole  657  communicating the second flow path F 2  and the lower arm chamber  69  with each other, and the other part becomes a third communication hole  658  communicating the third flow path F 3  and the lower arm chamber  69  with each other. 
     Further, the fourth rib  6533  and the sixth rib  6535  fix both ends of the second flange  6531  to the lower frame  65 , and the fifth rib  6534  protrudes from the second flange  6531  to divide a space formed by the fourth rib  6533  and the sixth rib  6535  into two parts. 
     When the chamber communication hole  651  formed between the fourth rib  6533  and the sixth rib  6535  into two parts by the fifth rib  6534 , one part becomes a second communication hole  657  communicating the second flow path F 2  and the lower arm chamber  69  with each other, and the other part becomes a third communication hole  658  communicating the third flow path F 3  and the lower arm chamber  69  with each other. 
     The above-described six ribs  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535  may be separated from one another by the same angle, for example, 60 degrees, based on the center of the chamber communication hole  651 . The reason for this is that the above-described six ribs  6523 ,  6524 ,  6525 ,  6533 ,  6534  and  6535  are combined with upper gears  97  provided on a flow path switching unit  9  and serve as parts to rotate a switching unit body  91 , e.g., upper gear fastening parts. 
     The third diaphragm  654  extends from the second rib  6524  and protrudes from the lower frame  65  to divide the inner surface of the lower frame  65 , and the fourth diaphragm  655  extends from the fifth rib  6534  and protrudes from the lower frame  65  to divide the inner surface of the lower frame  65 . 
     As shown in  FIG. 3A , lower spray holes to spray washing water to the cover  15  may be further provided on the lower frame  65 . The lower spray holes may include first lower spray holes  6591  to spray washing water introduced into the second flow path F 2  to the cover  15  and second lower spray holes  6593  to spray washing water introduced into the third flow path F 3  to the cover  15 . 
     Washing water discharged through the respective lower spray holes  6591  and  6592  prevents the recovery holes  151  from being clogged with foreign substances. 
     The upper frame  63  includes a first discharge hole  631  located above the first communication hole  656 , second discharge holes  633  to discharge washing water introduced into the second flow path F 2  to the outside of the lower arm  6 , and third discharge holes  635  to discharge washing water introduced into the third flow path F 3  to the outside of the lower arm  6 . 
     The first discharge hole  631  provides a space to withdraw the attachable unit body  511  of the tower attachable unit  5  from the lower arm  6 , is located above the first communication hole  656 , and has a smaller diameter than the first communication hole  656 . 
       FIG. 3A  illustrates the first discharge hole  631  as being located above the space formed by the first flange  6521  and the second flange  6531  and having a diameter which is greater than the diameter of the outer circumferential surface of the attachable unit body  511  and smaller than the diameter of the outer circumferential surface of the attachable unit flange  513 . 
     The second discharge holes  633  and the third discharge holes  635  may be provided so that the lower arm  6  is rotated about the arm holder  17  by repulsive force of washing water discharged from the respective discharge holes  633  and  635 . 
     In some implementations, first nozzles to spray washing water supplied to the second discharge holes  633  at a designated inclination angle to a plane parallel with the surface of the upper frame  63  are provided in the second discharge holes  633 , and second nozzles to spray washing water supplied to the third discharge holes  635  at a designated inclination angle to the plane parallel with the surface of the upper frame  63  are provided in the third discharge holes  635 . 
     The spray direction of washing water discharged from the first nozzles and the spray direction of washing water discharged from the second nozzles may be set to be opposite each other. The reason for this is that, if the rotating direction of the lower arm  6  when the second discharge holes  633  discharge washing water and the rotating direction of the lower arm  6  when the third discharge holes  635  discharge washing water are different, washing efficiency may be raised. 
     Further, the flow rate of washing water supplied to objects to be washed through the first flow path F 1 , the flow rate of washing water supplied to objects to be washed through the second flow paths F 2 , and the flow rate of washing water supplied to objects to be washed through the third flow paths F 3  may be different. 
       FIG. 3A  illustrates the second discharge holes  633  and the third discharge holes  635  as being provided in different numbers so that the flow rate of washing water supplied to objects to be washed through the third flow paths F 3  is less than the flow rate of washing water supplied to objects to be washed through the second flow paths F 2 . 
     In some implementations, the flow rate of washing water through the tower flow path  3  receiving washing water supplied through the first flow path  1  and spraying the washing water may be equal to one of the flow rate of washing water through the second discharge holes  633  and the flow rate of washing water through the third discharge holes  635  or be different from the flow rate of washing water through the second discharge holes  633  and the flow rate of washing water through the third discharge holes  635 . 
     As shown in  FIGS. 4A and 4B , the lower arm chamber  69  is fixed to the chamber communication hole  651  provided on the lower frame  65 . The lower arm chamber  69  is combined with the lower frame  65  such that the first communication hole  656 , the second communication holes  657  and the third communication holes  658  are located within the lower arm chamber  69 . That is, the lower arm chamber  69  is provided to surround the first communication hole  656 , the second communication holes  657  and the third communication holes  658 . 
     The lower arm chamber  69  includes a support pipe  697  rotatably combined with the arm holder  17 , an inlet hole  691  formed through the support pipe  697  to introduce washing water into the lower arm chamber  69 , and lower gear fastening parts  695  provided on the inner circumferential surface of the lower arm chamber  69 . 
     The lower gear fastening parts  695  are combined with lower gears  99 , referring to  FIG. 6B ), of the flow path switching unit  9 , which will be described later, and server to rotate the switching unit body  91  by a designated angle. A plurality of lower gear fastening parts  695  may be separated by the same angle along the circumferential surface of the lower arm chamber  69  and  FIG. 4B  illustrates the lower gear fastening parts  695  as being separated by 60 degrees based on the center of the inlet hole  691 . 
     A guider  693 , with which a support body  96  of the flow path switching unit  9  is combined, is provided within the lower arm chamber  69 . The guider  693  needs to be provided at a lower position than the lower gear fastening parts  695 .  FIG. 4B  illustrates the guider  693  as being fixed to the inner circumferential surface of the inlet hole  691 . 
     The guider  693  may be provided in parallel with the third diaphragm  654  and the fourth diaphragm  655 . The reason for this is to easily distribute washing water, introduced into the chamber  69 , to the second communication holes  657  and the third communication holes  658 . 
     The flow path switching unit  9  to sequentially open the first communication hole  656 , the second communication holes  657  and the third communication holes  658  according to pressure, for example, hydraulic pressure, within the lower arm chamber  69  is provided within the lower arm chamber  69 . 
     The flow path switching unit  9  may include a support part reciprocating within the lower arm chamber  69  according to pressure, for example, hydraulic pressure, within the lower arm chamber  69  and a switching part rotatably combined with the support part and located on the upper surface of the support part. 
     That is, the switching part may include a switching unit body  91  being rotatable within the lower arm chamber  69  and the support part may include a support body  96  provided within the lower arm chamber  69  and supporting the support unit body  91 . 
     The support body  96  may reciprocate in the height direction of the lower arm chamber  69 , e.g., a direction from the inlet hole  691  and the chamber communication hole  651 , and thus assist reciprocation of the switching unit body  91  and provide a center of rotation of the switching unit body  91 . 
     As shown in  FIGS. 5A and 5B , the support body  96  may have a disc shape and include support body through holes  965  formed through the support body  96 , a shaft  961  protruding from the upper surface of the support body  96  toward the switching unit body  91 , and a guider combination unit  963  protruding from the lower surface of the support body  96  toward the guider  693  of the lower arm chamber  69 . 
     Two support body through holes  965  may be separated from each other by 180 degrees based on the shaft  961 . The support body through holes  965  are located within the space formed by the first through hole  656 , when the guider combination unit  693  is combined with the guider  693 . 
     The guider combination unit  963  may include a first combination part  9631  and a second combination part  9632  protruding from the lower surface of the support body  96 , and the first combination part  9631  and the second combination part  9632  are separated from each other by a sufficient distance to receive the guider  693 . 
     Further, the first combination part  9631  and the second combination part  9632  have a sufficient length to prevent separation of the first combination part  9631  and the second combination part  9632  from the guider  693  even if the support body  96  is raised to the maximum height within the lower arm chamber  69 . 
     Therefore, when washing water is introduced into the lower arm chamber  69 , the support body  96  is guided by the guider  693  and the guider combination unit  963  and raised in the height direction of the lower arm chamber  69  and, when washing water is not supplied to the lower arm chamber  69 , the support body  96  is only lowered in the height direction of the lower arm chamber  69 . 
     As shown in  FIGS. 6A and 6B , the switching unit body  91  may have a disc shape and reciprocate between the inlet hole  691  of the lower arm chamber  69  and the chamber communication hole  651  according to hydraulic pressure in the lower arm chamber  69 . 
     That is, the switching unit body  91  moves from the inlet hole  691  to the chamber communication hole  651 , when the hydraulic pressure in the lower arm chamber  69  is high, e.g., when washing water is supplied to the lower arm chamber  69 , and moves from the chamber communication hole  651  to the inlet hole  691 , when the hydraulic pressure in the lower arm chamber  69  is low, e.g., when washing water is not supplied to the lower arm chamber  69 . 
     The attachable unit flange  513  provided on the tower attachable unit  5  is seated on the upper surface of the switching unit body  91 . 
     The switching unit body  91  includes a shaft through hole  92  formed through the switching unit body  91  so that the shaft  961  of the support body  92  passes through the shaft through hole  92 , first openings  93  and second openings  95  formed through the switching unit body  91 , and gear parts  97  and  99  respectively combined with the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535  and the lower gear fastening parts  695  to rotate the switching unit body  91  in only one of the clockwise direction and the counterclockwise direction. 
     The shaft  961  of the support body  96  inserted into the shaft through hole  92  forms a center of rotation of the switching unit body  91 . 
     The first openings  93  serve to open the support body through holes  965  provided on the support body  96  according to the rotation angle of the switching unit body  91 , and the second openings  95  serve to open one of the second communication holes  657  and the third communication holes  658  according to the rotation angle of the switching unit body  91 . 
     For this purpose, a distance from the shaft through hole  92  to the first openings  3  needs to be shorter than a distance from the shaft through hole  92  to the second opening  95 . 
     The second openings  95  may open a space formed by the first rib  6523  and the sixth rib  6535  and a space formed by the third rib  6525  and the fourth rib  6533  within the space of the first communication hole  656  when the first openings  93  open the support body through holes  965 , referring to  FIGS. 7B (a) and  7 B(b). 
     For this purpose, the center of the first openings  93  and the center of the second openings  95  are located on a straight line passing through the center of the shaft through hole  92  and the first openings  93  and the second openings  95  have sizes to be located within the space formed by the first diaphragm  652  and the second diaphragm  653 . 
     Attachable unit guiders  94  inserted into the body through hole  515  of the attachable unit body  511  may be further provided on the upper surface of the switching unit body  91 . When the switching unit body  91  is raised within the lower arm chamber  69 , the attachable unit guiders  94  apply pressure to the guider support part  517  so that the attachable unit body  511  may be withdrawn from the lower arm  6 . 
     The gear parts may include upper gears  97  provided on the upper surface of the switching unit body  91  and combined with the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535 , and lower gears  99  provided on the lower surface of the switching unit body  91  and combined with the lower gear fastening parts  695 . 
     The upper gears  97  are combined with the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534  and  6535  and rotate the switching unit body  91  by a designated angle, for example, 30 degrees, in the clockwise direction or counterclockwise direction, and the lower gears  99  are combined with the lower gear fastening parts  695  and rotate the switching unit body  91  by a designated angle, for example, 30 degrees, in the clockwise direction or counterclockwise direction. 
     The lower gears  99  and the lower gear fastening parts  695  are provided so as to rotate the switching unit body  91  in the same direction as the rotation direction of the switching unit body  91  when the upper gears  97  and the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535  are combined. 
     Hereinafter, an operating process of the lower arm  6  with reference to  FIGS. 7A (a),  7 A(b),  7 B(a), and  7 B(b) and  FIGS. 8A, 8B and 8C  will be described. 
     As shown in  FIGS. 7A (a) and  7 A(b), if washing water is not supplied to the lower arm chamber  69 , the seated state of the support body  96  on the guider  693  is maintained and the combined state of the lower gears  99  of the switching unit body  91  with the lower gear fastening parts  695  is maintained. 
     Here, the support body through holes  965  is located under the space formed by the first flange  6521  and the second flange  6531  within the space formed by the first communication hole  656 , the centers of the first openings  93  are separated from the centers of the support body through holes  965  by 30 degrees, e.g., only the half of each of the support body through holes  965  is opened by the first opening  93 , and the second openings  95  are located between the first communication hole  656  and the third communication holes  658 . In some implementations, only a part of the first communication hole  656  and only a part of each of the third communication holes  658  are opened. 
     When the first supply path  21  is opened through the supply path switching valve  27  and power is supplied to the motor  187  to operate the water supply pump  18 , washing water is supplied to the lower arm chamber  69 . 
     As shown in  FIGS. 7B (a) and  7 B(b), when washing water is supplied to the lower arm chamber  69  and the hydraulic pressure within the lower arm chamber  69  is increased, the support body  96  moves from the inlet hole  691  toward the chamber communication hole  651  and, thus, the switching unit body  91  also moves toward the chamber communication hole  651 . 
     Since the guider combination parts  9631  and  9633  are combined with the guider  693 , the support body  96  is not rotated and is raised within the lower arm chamber  69  and the switching unit body  91  is rotated by 30 degrees in the clockwise direction based on the shaft  691  when the upper gears  97  are combined with the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535 . 
     Further, the attachable unit body  511  located on the upper surface of the switching unit body  91  is withdrawn from the inside of the lower arm  6  toward the tower flow path  3  by the attachable unit guiders  94  pushing the guider support part  517  and inserted into the reception hole  455  of the connector  45 . 
     Since the diameter of the attachable unit flange  513  is greater than the diameter of the first discharge hole  631  provided on the upper frame  63 , the attachable unit body  511  is not separated from the lower arm  6 . 
     When the switching unit body  91  is rotated by 30 degrees in the clockwise direction, the first openings  93  completely open the support body through holes  965  and the second openings  95  are located within the space formed by the first diaphragm  652  and the second diaphragm  653 . In some implementations, the second openings  95  are located within the space formed by the first rib  6523  and the sixth rib  6535  and the space formed by the third rib  6525  and the fourth rib  6533 . 
     Therefore, the closed state of the second communication holes  657  communicating with the second flow paths F 2  and the third communication holes  658  communicating with the third flow paths F 3  by the switching unit body  91  is maintained. 
     When the first openings  93  and the second openings  95  are located within the first communication hole  656 , referring to  FIGS. 7B (a) and  7 B(b), washing water introduced into the lower arm chamber  69  is supplied only to the tower flow path  3  through the attachable unit body  511  and, thus, the tower flow path  3  sprays the washing water toward the lower rack  193 . 
     Thereafter, when power supply to the motor  187  of the water supply pump  18  is intercepted, the hydraulic pressure within the lower arm chamber  69  is lowered and the support body  96  and the switching unit body  91  move toward the inlet hole  691  located on the bottom surface of the lower arm chamber  69 . 
     The support body  96  moves toward the inlet hole  691  without rotation due to the guider  693  and the guide combination unit  963 , but the switching unit body  91  is rotated by 30 degrees in the clockwise direction when the lower gears  99  are combined with the lower gear combination parts  695 . 
     That is, as shown in  FIG. 8A , the first openings  93  of the switching unit body  91  is separated from the support body through holes  965  by 30 degrees and the second openings  95  are located between the first communication holes  656  and the second communication holes  657 , e.g., the second opening  95  opens a part of the first communication hole  656  and a part of the second communication hole  657 . 
     Since the switching unit body  91  moves toward the inlet hole  691 , the attachable unit body  511  is separated from the connector  45  and moves toward the lower arm  6 . 
     Thereafter, when power is re-supplied to the motor  187  of the water supply pump  18 , the support body  96  and the switching unit body  91  move again from the inlet hole  691  to the chamber communication hole  651  by the hydraulic pressure within the lower arm chamber  69 . 
     When washing water is re-supplied to the lower arm chamber  69 , as shown in  FIG. 8B , the switching unit body  91  is rotated by 30 degrees in the clockwise direction and, thus, the support body through holes  965  of the support body  96  are closed by the switching unit body  91  and the second openings  95  open the second communication holes  657  communicating with the second flow paths F 2 . 
     When the second communication holes  657  are opened, the washing water in the lower arm chamber  69  is supplied to the second flow paths F 2  and the washing water in the second flow paths F 2  is sprayed to the lower rack  193  through the second discharge holes  633 . 
     However, since the closed state of the support body through holes  965  and the third communication holes  658  by the switching unit body  91  is maintained, washing water is not supplied to the tower flow path  3  and the third flow paths F 3 . 
     Thereafter, when power supply to the motor  187  of the water supply pump  18  is intercepted, the hydraulic pressure within the lower arm chamber  69  is lowered and the support body  96  and the switching unit body  91  move toward the inlet hole  691  located on the bottom surface of the lower arm chamber  69 . 
     The support body  96  moves toward the inlet hole  691  without rotation due to the guider  693  and the guide combination unit  963 , but the switching unit body  91  is rotated by 30 degrees in the clockwise direction when the lower gears  99  are combined with the lower gear fastening parts  695 . 
     Here, the closed state of the support body through holes  965  by the switching unit body  91  is maintained and the second openings  95  of the switching unit body  91  are located between the second communication holes  657  and the third communication holes  658 . 
     When washing water is re-supplied to the lower arm chamber  69 , the support body  96  and the switching unit body  91  move from the inlet hole  691  toward the chamber communication hole  651  and, thus, reach the state of  FIG. 8C . 
     That is, since the switching unit body  91  is rotated by 30 degrees in the clockwise direction, the third communication holes  658  communicating with the third flow paths F 3  are opened by the second openings  95  and the closed state of the support through holes  965  and the second communication holes  657  by the switching unit body  91  is maintained. 
     Since the third communication holes  658  are opened, the washing water within the lower arm chamber  69  is sprayed to the lower rack  193  through the third flow paths F 3  and the third discharge holes  635 . However, the closed state of the support body through holes  965  and the second communication holes  657  by the switching unit body  91  is maintained and, thus, washing water is not supplied to the tower flow path  3  and the second flow paths F 2 . 
     Thereafter, when power supply to the motor  187  of the water supply pump  18  is intercepted, the support body  96  and the switching unit body  91  move toward the inlet hole  691  located on the bottom surface of the lower arm chamber  69  and reach the state of  FIGS. 7A (a) and  7 B(b). 
     Although the above-described implementation describes the flow path switching unit  9  as being rotated only in the clockwise direction, in some implementations, the upper gears  97 , the lower gears  99 , the upper gear fastening parts  6523 ,  6524 ,  6525 ,  6533 ,  6534 , and  6535  and the lower gear fastening parts  695  may be provided so as to rotate the flow path switching unit  9  in the counterclockwise direction. 
       FIGS. 9A, 9B, and 9C  are illustrate one example of the upper arm  7  provided in the dishwasher. The upper arm  7  shown in  FIGS. 9A, 9B and 9C  includes two flow paths F 4  and F 5  separated from each other and the first upper arm flow paths F 4  and the second upper arm flow paths F 5  receive washing water supplied by an upper arm flow path switching unit  76 . 
     In some implementations, the upper arm  7  may include an upper arm chamber  70  receiving washing water supplied through the second supply path  23 , an upper arm lower frame  75  communicating with the upper arm chamber  79  and having communication holes  755  and  757  communicating with the first upper arm flow paths F 4  and the second upper arm lower flow paths F 5 , and an upper arm upper frame  73  having discharge holes  731  and  733  to discharge washing water introduced through the respective flow paths F 4  and F 5  to the outside of the upper rack  191 . 
     A first upper arm diaphragm  751  and a second upper arm diaphragm  753  are provided on the upper arm lower frame  75 . The first upper arm diaphragm  751  and a second upper arm diaphragm  753  are orthogonal to each other to form the first upper arm flow paths F 4  and the second upper arm flow paths F 5 . 
     The upper arm lower frame  75  includes the first upper arm communication holes  755  and the second upper arm communication holes  757  communicating the respective flow paths F 4  and F 5  with the upper arm chamber  79 . 
     The first upper arm communication holes  755  serve to communicate the first upper arm flow paths F 4  with the upper arm chamber  79 , and the second upper arm communication holes  757  serve to communicate the second upper arm flow paths F 5  with the upper arm chamber  79 . 
     One first upper arm communication hole  755  is separated from the other first upper arm communication hole  755  by 180 degrees, and one second upper arm communication hole  757  is separated from the other second upper arm communication hole  757  by 180 degrees. 
     The upper arm upper frame  73  is located above the upper arm lower frame  75  and includes the discharge holes  731  and  733  to discharge washing water supplied to the respective flow paths F 4  and F 5  to the upper rack  191 . 
     The first upper arm discharge holes  731  serve to discharge washing water supplied to the first upper arm flow paths F 4  to the upper rack  191 , and the second upper arm discharge holes  733  serve to discharge washing water supplied to the second upper arm flow paths F 5  to the upper rack  191 . 
     The flow rate of washing water supplied to objects to be washed through the first upper arm flow paths F 4  may differ from the flow rate of washing water supplied to objects to be washed through the second upper arm flow paths F 5 . 
       FIGS. 9A, 9B, and 9C  illustrate that the number of the first upper arm discharge holes  731  is greater than the number of the second upper arm discharge hole  733  so that the flow rate of washing water supplied to objects to be washed through the first upper arm flow paths F 4  and the flow rate of washing water supplied to objects to be washed through the second upper arm flow paths F 5  may be different. 
     Washing water discharged from the first upper arm discharge holes  731  needs to be sprayed at a designated inclination angle to a plane parallel with the surface of the upper arm upper frame  73  and washing water discharged from the second upper arm discharge holes  733  needs to be sprayed at a designated inclination angle to the plane parallel with the surface of the upper arm upper frame  73 . 
     Further, the spray direction of washing water discharged through the first upper arm discharge holes  731  and the spray direction of washing water discharged through the second upper arm discharge holes  733  may be set to be opposite each other. The reason for this is that, if the rotating direction of the upper arm  7  when the first upper arm discharge holes  731  discharge washing water and the rotating direction of the upper arm  7  when the second upper arm discharge holes  733  discharge washing water are different, washing efficiency may be raised. 
     The upper arm chamber  79  is fixed to the upper arm lower frame  75  so as to surround the respective communication holes  755  and  757 . 
     The upper arm chamber  79  is rotatably combined with the second supply path  23  through a supply path connector  795 , and an inlet hole  797  to supply washing water supplied through the second supply path  23  to the upper arm chamber  79  is provided on the flow path connector  795 . 
     The upper arm flow path switching unit  76  to selectively open and close the first upper arm communication holes  755  and the second upper arm communication holes  757  is provided within the upper arm chamber  79 . 
     The upper arm flow path switching unit  76  is rotated within the upper arm chamber  79  by a first fastening part  791  provided on the upper surface of the upper arm chamber  79  and a second fastening part  793  provided on the lower surface of the upper arm chamber  79 . 
     The upper arm flow path switching unit  76  includes an upper arm switching body  761  reciprocating within the upper arm chamber  79  and a gear unit  771 ,  773  and  775  combined with the first fastening part  791  and the second fastening part  793  to rotate the upper arm switching body  761 . 
     As shown in  FIGS. 10A and 10B , the upper arm switching body  761  may have a cylindrical shape having a closed upper surface and an opened lower surface, and flow path openings  763  may be provided on the closed surface of the upper arm switching body  761 . Two flow path openings  763  are separated from each other by 180 degrees. 
     The gear unit includes a gear body  771  fixed to the circumferential surface of the upper arm switching body  761 , a first gear  773  provided on the upper surface of the gear body  771  and combined with the first fastening part  791 , and a second gear  775  provided on the lower surface of the gear body  771  and combined with the second fastening part  793 . 
     The gear body  771  may be fixed to the upper arm switching body  761  through a flange  777 . 
     The first gear  773  is combined with the first fastening part  791  and rotates the upper arm switching body  761  by a designated angle in the clockwise direction or counterclockwise direction, and the first gear  775  is combined with the second fastening part  793  and rotates the upper arm switching body  761  by a designated angle in the clockwise direction or counterclockwise direction. 
     That is, the second gear  775  and the second fastening part  793  are provided so as to rotate the upper arm switching body  761  in the same direction as the rotation direction of the switching body  761  when the first gear  773  and the first fastening part  791  are combined. 
     The upper arm  7  having the above-described structure supplies washing water to the first upper arm flow paths F 4  and the second upper arm flow paths F 5  via a process shown in  FIGS. 11A to 11D . 
     If washing water is not supplied to the upper arm chamber  79 , the second gear  775  of the upper arm flow path switching unit  76  is combined with the second fastening part  793  and the upper arm switching body  761  maintains the state of  FIG. 11A . 
     That is, the separated state of the flow path openings  763  from the first upper arm communication holes  755  by 45 degrees, e.g., the separated state of the flow path openings  763  from the second upper arm communication holes  757  by 45 degrees, is maintained. 
     When the second supply path  23  is opened through the supply path switching valve  27  and power is supplied to the motor  187  of the water supply pump  18 , washing water stored in the sump  13  is supplied to the upper arm chamber  79 . 
     When washing water is supplied to the upper arm chamber  79 , the hydraulic pressure within the upper arm chamber  79  is raised and the upper arm switching body  761  moves from the inlet hole  797  toward the upper arm lower frame  75 , e.g., toward the first fastening part  791 . 
     When the upper arm switching body  761  is raised within the upper arm chamber  79 , the first gear  773  is combined with the first fastening part  791  and rotates the upper arm switching body  761  by 45 degrees in the clockwise direction. Therefore, as shown in  FIG. 11B , the first upper arm communication holes  755  are opened by the flow path openings  763  but the second upper arm communication holes  757  are closed by the upper arm switching body  761 . 
     When the first upper arm communication holes  755  are opened, washing water is supplied to the first upper arm flow paths F 4  and the washing water within the first upper arm flow paths F 4  is sprayed to the upper rack  191  through the first upper arm discharge holes  731 . 
     Thereafter, when power supply to the motor  187  of the water supply pump  18  is intercepted, the hydraulic pressure within the upper arm chamber  79  is lowered and the upper arm switching body  761  moves toward the inlet hole  797  on which the second fastening part  793  is located. 
     When the upper arm switching body  761  moves toward the inlet hole  797 , the second gear  775  is combined with the second fastening part  793  and rotates the upper arm switching body  761  by 45 degrees in the clockwise direction. That is, as shown in  FIG. 11C , the flow path openings  763  are separated from each of the first upper arm communication holes  755  and the second upper arm communication holes  757  by 45 degrees. 
     In such a state, when washing water is re-supplied to the upper arm chamber  79 , the upper arm switching body  761  moves toward the upper surface of the upper arm chamber  79  and, thus, the first gear  733  is combined with the first fastening part  791  and rotates the upper arm switching body  761  by 45 degrees in the clockwise direction. 
     In this case, the closed state of the first upper arm communication holes  755  by the upper arm switching body  761  is maintained and the second upper arm communication holes  757  are opened by the flow path openings  763 , referring to  FIG. 11D . Therefore, washing water in the upper arm chamber  79  is supplied to the second upper arm flow paths F 5  and then discharged to the upper rack  191  through the second upper arm discharge holes  733 . 
     Thereafter, when power supply to the motor  187  of the water supply pump  18  is intercepted, the upper arm switching body  761  returns to the state of  FIG. 11A . 
     Although the above-described implementation describes the upper arm flow path switching unit  76  as being rotated in the clockwise direction, in some implementations, the first gear  773 , the second gear  775 , the first fastening part  791 , and the second fastening part  793  may be provided so as to rotate the upper arm flow path switching unit  76  in the counterclockwise direction. 
       FIG. 12  illustrates an example control method of a dishwasher including at least two flow paths having different flow paths to spray washing water objects to be washed. 
     Such a control method is characterized in that, when power is supplied to the motor  187  of the water supply pump  18  and the upper arm  7  or the lower arm  6  sprays washing water to objects to be washed, the state of the flow path switching unit  9  of the lower arm  6  or the upper arm flow path switching unit  76  and the positions of the respective flow path switching units  9  and  76  may be judged by measuring repulsive force of washing water acting on the impeller  186 , a load of the impeller  186 , or a load of the motor  187 . 
     When flow rates of washing water sprayed through the flow paths F 1 , F 2 , F 3 , F 4 , and F 5  provided on the respective arms  6  an d 7  are different, the load of the impeller  186  is varied. The load of the impeller  186  may be judged by operating the motor  187  so that the impeller  186  maintains a designated RPM and then measuring the amount of power or the amount of current supplied to the motor  187 . 
     However, if power of a designated intensity continues to be supplied to the motor  187 , the load of the impeller  186  may be judged by measuring the RPM of the impeller  186 . 
     Hereinafter, the control method, when the load of the impeller  186  is judged through the amount of current supplied to the lower arm  6  having three flow paths F 1 , F 2 , and F 3  and the motor  187  will be described. 
     First, power is supplied to the motor  187  of the water supply pump  18  under the condition that the first supply path  21  is opened by the supply path switching valve  27  (S 11 ). 
     When power is supplied to the motor  187 , the amount of current supplied to the motor  187  is measured (S 13 ). 
     In some implementations, the lower arm  6  has three flow paths F 1 , F 2 , and F 3  separated from one another and at least two of the three flow paths F 1 , F 2 , and F 3  have different flow rates. 
     The amount of current supplied to the motor  187  to supply washing water to one of the flow paths having different flow rates differs from the amount of current supplied to the water supply pump  18  to supply washing water to another of the flow paths having different flow rates. Because the load of the motor  187  is varied according to the amount, or flow rate, of washing water discharged each of the flow paths per unit time. 
     That is, as the amount, or flow rate, of washing water to be supplied to a flow path per unit time increases, the load of the motor  187  increases. Therefore, the amount of current supplied to the water supply pump  18  is varied according to the flow rate of the flow path. 
     Although the measurement (S 13 ) may be carried out simultaneously with the supply of power to the motor  187  (S 11 ), the measurement (S 13 ) may be carried out after a predetermined reference time from time when power supply to the motor  187  is started has elapsed (S 12 ). 
     At the initial stage of operation of the water supply pump  18 , air may remain within the first supply path  21  connecting the lower arm  6  to the water supply pump  18  or air may be introduced into the water supply pump  18  according to the water level of the sump  13 . 
     When air remains within the first supply path  21  or air is introduced into the water supply pump  18 , the load of the motor  187  may not be precisely measured through the amount of current supplied to the motor  187 . 
     Therefore, if the measurement of the amount of current (S 13 ) is carried out after the predetermined reference time from time when power supply to the motor  187  is started has elapsed (S 12 ), the amount of current supplied to the motor  187  may be precisely measured. 
     The measurement of the amount of current (S 13 ) may be carried out for a predetermined measurement reference time, and data measured in the measurement of the amount of current (S 13 ) may be set to be the sum of the amount of current measured for the measurement reference time or the mean amount of current (the sum of the amount of current/the measurement reference time). 
     When the measurement of the amount of current (S 13 ) has been completed, the measured amount of current is compared with predetermined reference current amounts (S 14 , S 15  and S 16 ). 
     The amounts of current supplied to the motor  187  when washing water is normally supplied to the flow paths F 1 , F 2 , and F 3  may be set as the reference current amounts. 
     That is, if the lower arm  6  has three flow paths F 1 , F 2 , and F 3 , a first reference current amount experimentally measured when washing water is normally supplied to the first flow path F 1  (connected to the tower flow path  31 ), a second reference current amount experimentally measured when washing water is normally supplied to the second flow paths F 2  (connected to the second discharge holes  633 ), and a third reference current amount experimentally measured when washing water is normally supplied to the third flow paths F 3  (connected to the third discharge holes  635 ) may be set as reference current amounts. 
     If the amount of current measured in the measurement (S 13 ) is set to be the sum of the amount of current measured for the measurement reference time, the respective reference current amounts are set to be the sums of the amounts of current supplied to the motor  187  for the measurement reference time when washing water is normally supplied to the respective flow paths F 1 , F 2 , and F 3 . 
     However, if the amount of current measured in the measurement (S 13 ) is set to be the mean amount of current, the respective reference current amounts may be set to be the mean values of the amounts of current supplied to the motor  187  for the measurement reference time when washing water is normally supplied to the respective flow paths F 1 , F 2 , and F 3 . 
     Further, each reference current amount may be set to be data, e.g., a range value, having the maximum amount of current and the minimum amount of current. 
     The comparison of the amount of current measured thorough the measurement (S 13 ) with the reference current amounts is carried out by sequentially comparing the measured amount of current with the first reference current amount, the second reference current amount and the third reference current amount (S 14 , S 15 , and S 16 ). 
     In case of the lower arm  6  of the dishwasher, since the flow path F 1 , F 2 , or F 3  to which washing water is supplied is changed according to the position of the flow path switching unit  9 , the state of the flow path switching unit  9  as well as the flow path F 1 , F 2 , or F 3  to which washing water is supplied may be judged, e.g., the current position of the flow path switching unit  9  may be judged, by comparing the amount of current measured in the measurement (S 13 ) with the respective reference current amounts. 
     That is, when the amount of current measured in the measurement (S 13 ) is equal to the first reference current amount (S 14 ), a controller may judge that washing water is sprayed to the upper rack  191  by the tower flow path  3  through the first flow path F 1 . 
     However, when the amount of current measured in the measurement (S 13 ) is equal to the second reference current amount (S 15 ) or the third reference current amount (S 16 ), the controller may judge that washing water is sprayed to the lower rack  193  through the second flow paths F 2  or the third flow paths F 3 . 
     On the other hand, when the amount of current measured in the measurement (S 13 ) is not equal to any one of the three reference current amounts, a user is notified of a warning through a character signal or a sound signal (S 17 ). 
     The notification (S 17 ) is carried out through an alarm unit controlled by the controller, and the alarm unit may include at least one of a display device and a speaker. 
     Through the notification (S 17 ), the user is notified of malfunction of the dishwasher and, thus, induced to find reasons for malfunction of the dishwasher. 
     Non-coincidence of the amount of current measured in the measurement (S 13 ) with any one of the three reference current amounts may be generated by various reasons, such as if the flow path switching unit  9  is not normally operated, if the tower flow path  3  is located at a position causing a difficulty in combination with the tower attachable unit  5 , if the tower attachable unit  5  is not withdrawn from the lower arm  6 , if the respective flow paths of the lower arm  6  are clogged with foreign substances, and the like. 
     Upon judging that the amount of current measured in the measurement (S 13 ) is equal to any one of the first reference current amount, the second reference current amount and the third reference current amount (S 14 , S 15 , and S 16 ), the flow path switching unit  9  may be moved to a predetermined initial position (S 21  to S 26 ). 
     Whether or not the flow path switching unit  9  is located at the initial position is judged through judgment as to whether or not the amount of current measured in the measurement (S 13 ) is equal to a reference current amount for position judgment (S 21 ). 
     One of the above-described reference current amounts may be set as the reference current amount for position judgment. 
     If the flow path switching unit  9  is set to sequentially open the first flow path F 1 , the second flow paths F 2  and the third flow paths F 3  and a position to supply washing water to the tower flow path  31  through the first flow path F 1  is set as the initial position of the flow switching unit  9 , the third reference current amount may be set as the reference current amount for position judgment. 
     However, if a position to spray washing water to the lower rack  193  through the second flow paths F 2  is set as the initial position of the flow switching unit  9 , the first reference current amount may be set as the reference current amount for position judgment and, if a position to spray washing water to the lower rack  193  through the third flow paths F 3  is set as the initial position of the flow switching unit  9 , the second reference current amount may be set as the reference current amount for position judgment. 
     In any case, when the amount of current measured in the measurement (S 13 ) is not equal to the reference current amount for position judgment (S 21 ), power supply to the motor  187  of the water supply pump  18  is intercepted (S 22 ), power is re-supplied to the motor  187  of the water supply pump  18  (S 23 ), the amount of current supplied to the motor  187  during the re-supply of power is additionally measured (S 25 ), and whether or not the amount of current measured in the additional measurement (S 25 ) is equal to the reference current amount for position judgment (S 26 ). 
     When the interception (S 22 ) and the re-supply of power (S 23 ) are carried out, the flow path switching unit  9  sequentially opens the first flow path F 1 , the second flow paths F 2  and the third flow paths F 3 . 
     Therefore, when the interception (S 22 ), the re-supply of power (S 23 ) and the additional measurement (S 25 ) are repeated until the amount of current measured in the additional measurement (S 25 ), executed during the re-supply of power (S 23 ), is equal to the reference current amount for position judgment (S 26 ), the flow path switching unit  9  may be moved to the initial position. 
     Although  FIG. 12  illustrates the process for judging the position of the flow path switching unit  9  of the lower arm  6  and the state of the flow path switching unit  9 , in some implementations, the control method shown in  FIG. 12  may be applied to a control method for judging the position of the upper arm flow path switching unit  76  of the upper arm  7  and the state of the upper arm flow path switching unit  76 . 
     If the control method of  FIG. 12  is applied to the upper arm  7 , only comparison of the amount of current measured in the measurement with the third reference current amount (S 16 ) is omitted and a detailed description of the control method applied to the upper arm  7  will thus be omitted. 
     As apparent from the above description, the subject matter described may provide a dishwasher having improved washing ability and a control method thereof. 
     Further, the subject matter described may provide a dishwasher in which a plurality of washing water flow paths is provided on one spray arm to spray washing water, and a control method thereof. 
     Further, the subject matter described may provide a dishwasher having a flow path switching unit to selectively open a plurality of flow paths provided on one spray arm, and a control method thereof. 
     Moreover, the subject matter described may provide a dishwasher which may judge the position a flow path switching unit and the state of the flow path switching unit, and a control method thereof.