Patent Publication Number: US-2022233048-A1

Title: Dishwasher and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0011653, filed on Jan. 27, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a dishwasher, and more particularly, to a dishwasher having an air jet generator for generating air bubbles. 
     BACKGROUND 
     A dishwasher is a household appliance that removes food particles remaining on dishes by spraying water on the dishes. 
     The dishwasher includes a tub having a space formed therein, and a sump mounted on the bottom of the tub to store water. The pump is configured to move the water stored in the sump to the inner space of the tub, where the pumped water washes dishes disposed in the inner space of the tub, and then flows into the sumpilters out after foreign substances are filtered out by a filter. The water circulates through the sump and the tub to wash dishes. 
     A conventional dishwasher includes an air jet generator that generates air bubbles in water supplied to a tub by using a part of water that is moved by a pump. 
     However, the air jet generator in the conventional dishwasher may generate noise caused by friction with water when air is sucked in. Such noise is generated during operation of the dishwasher and may provide discomfort to a user. 
     SUMMARY 
     The present disclosure is directed to a dishwasher capable of minimizing noise occurring during an operation of an air jet generator. 
     The present disclosure is also directed to a dishwasher that secures a flow rate of water supplied to an air jet generator. 
     According to one aspect of the subject matter described in this application, a dishwasher can include a tub defining a space that is configured to receive a target object to be washed, a sump disposed below the tub and configured to receive water, a pump connected to the sump and configured to move the water in the sump to the space of the tub, an air jet generator configured to receive a part of the water discharged from the pump and configured generate air bubbles in the water, and a control valve configured to control a flow of the water to the air jet generator. 
     Implementations according to this aspect can include one or more of the following features. For example, the pump can include a housing, a water inlet pipe that protrudes from a first side of a circumferential surface of the housing and that is connected to the sump, a water outlet pipe that protrudes from the first side of the circumferential surface of the housing and that is connected to a spray nozzle disposed inside the space, an impeller rotatably disposed inside the housing and configured to move water inside the housing, and a branch pipe that protrudes from a circumferential surface of the water outlet pipe and that is configured to move a part of water flowing through the water outlet pipe to the air jet generator. The control valve can be configured to control a flow of water to the branch pipe. 
     In some implementations, the dishwasher can include a connection pipe connecting the branch pipe to the air jet generator, where the control valve can be disposed at the connection pipe. In some examples, the pump can further include a heater configured to heat the water inside the housing, and a steam discharge pipe that protrudes from a circumferential surface of the water outlet pipe and that is configured to supply steam to the space of the tub. The branch pipe can protrude below the steam discharge pipe. 
     In some implementations, the control valve can be configured to, based on a main wash cycle of washing the target object using a detergent being completed, block the flow of the water to the air jet generator. In some implementations, the dishwasher can further include a connection pipe configured to move a part of the water discharged from the pump to the air jet generator. The control valve can be configured to, based on a main wash cycle of washing the target object using a detergent being completed, reduce an opening area of a flow path provided inside the connection pipe. 
     In some examples, the air jet generator can have a Venturi tube shape and can be configured to pulverize air introduced through an air inlet hole with water flowing through a flow path perpendicular to a bottom surface of the tub. In some implementations, the spray nozzle can be configured to spray water to the space. 
     In some implementations, the air jet generator can be configured to discharge the water having air bubbles to the space. In some implementations, the air jet generator can include an air crushing pipe including a first pipe providing (i) an inlet at a lower side of the air crushing pipe, (ii) an opening in a water flowing direction, and (iii) a cross-sectional area reducing in the water flowing direction, and a second pipe disposed above the first pipe, the second pipe providing (i) an opening in the water flowing direction and (ii) a cross-sectional area increasing in the water flowing direction, and an air tab disposed at an upper portion of the second pipe and vertically provided with a plurality of air holes. 
     In some examples, an air inlet hole can be provided at a first side of the air crushing pipe. In some examples, the air inlet hole can be provided at an upstream end of the second pipe. 
     In some implementations, the air inlet hole can be provided at a lower end of the second pipe. In some implementations, the air inlet hole can be provided perpendicularly to a direction of a flow path where the water flows into the second pipe. 
     In some implementations, the air jet generator can include an air chamber, and the air inlet hole can provide fluid communication between an inside of the air crushing pipe and an outside of the air crushing pipe through the air chamber. In some examples, the air inlet hole can be defined at a lower end of the air chamber. In some examples, the air chamber can define an external air inlet hole through which external air is introduced. 
     In some implementations, based on the pump being operated, the water can flow upwards from the first pipe towards the second pipe. 
     According to another aspect of the subject matter described in this application, a method for controlling a dishwasher can include receiving water by a sump, operating a pump to move the water in the sump to a space inside a tub disposed in the dishwasher, controlling a control valve so that a part of the water discharged from the pump is supplied to an air jet generator that is configured to generate air bubbles in the water, opening a dispenser to supply a detergent to the space, stopping the pump and operating a drain pump to drain the water from the sump, receiving water by the sump again, operating the pump to move the water in the sump to the space, and controlling the control valve to block the supply of the water discharged from the pump to the air jet generator. 
     According to another aspect of the subject matter described in this application, a method for controlling a dishwasher can include performing a main wash cycle of operating a pump and removing foreign substances from a target object to be washed placed inside a space of the dishwasher using a detergent, and performing a rinse cycle of operating the pump and washing the target object having undergone through the main wash cycle using water. In the main wash cycle, a control valve cam be controlled to cause a part of the water from the pump to move to an air jet generator that is configured to generate air bubbles, and, in the rinse cycle, the control valve can be controlled to block a part of the water from the pump from being introduced to the air jet generator. 
     The dishwasher can have following advantages. 
     First, the dishwasher can minimize noise occurring in the air jet generator by controlling water supplied to the air jet generator according to a washing step. 
     Second, as the branch pipe for supplying water to the air jet generator protrudes from the water outlet pipe downward compared to the steam discharge pipe in the dishwasher, the dishwasher can stably secure the flow rate of water flowing to the air jet generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a schematic cross-sectional view of an exemplary dishwasher. 
         FIG. 2  is a diagram illustrating a perspective view of an exemplary air jet generator. 
         FIG. 3  is a diagram illustrating a cross-sectional perspective view of an exemplary air jet generator. 
         FIG. 4  is a diagram schematically illustrating an exemplary connection between a pump, an air jet generator, and a steam nozzle. 
         FIG. 5  is a diagram illustrating a perspective view of an exemplary pump. 
         FIG. 6  is a diagram illustrating a view for explaining an exemplary arrangement of a steam discharge pipe and a branch pipe disposed in a water outlet pipe. 
         FIG. 7A  is a table showing noise occurring in an exemplary dishwasher in a state in which a control valve is operated according to a wash cycle. 
         FIG. 7B  is a table showing noise occurring in the exemplary dishwasher in a state in which the control valve does not exist. 
         FIG. 8  is a flowchart illustrating a wash cycle of an exemplary dishwasher. 
         FIG. 9  is a flowchart illustrating a detailed method of controlling an exemplary dishwasher in a main wash cycle and a rinse cycle. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a dishwasher  10  can include a cabinet  20  defining an external appearance of the dishwasher, a door  22  coupled to the cabinet  20  and configured to open and close the inside of the cabinet  20 , and a tub  24  disposed inside the cabinet  20  and defining a space  24   s  in which water or steam is applied. 
     The dishwasher  10  can include a dispenser that stores detergent received from a user and that sprays the detergent into the tub  24  in a wash cycle. The dispenser can be disposed at the door  22 . In some implementations, the tub  24  defines the space  24   s  in which the dishes are disposed for washing dishes. 
     The dishwasher  10  can further include racks  30  and  32  for accommodating dishes in the tub  24 , a plurality of spray nozzles  34 ,  36 , and  38  for spraying water toward the dishes accommodated in the racks  30  and  32 , a sump  26  disposed below the tub  24  and configured to receive and store water, and a pump  50  for pressurizing the water stored in the sump  26  to move the water to the plurality of spray nozzles  34 ,  36 , and  38 . 
     The dishwasher  10  can further include a motor  58  for driving the pump  50 , and a brushless direct current motor (BLDC) capable of controlling a rotational speed may be used as the motor  58 . 
     The dishwasher  10  can further include a water supply device  70  for supplying water to the sump  26 , a drain device  72  connected to the sump  26  to discharge water to the outside of the dishwasher, and a filter  78  installed in the sump  26  and filters water. 
     The dishwasher  10  can further include a plurality of supply tubes  42 ,  44 , and  46  for moving water pumped by the pump  50  to each of the plurality of spray nozzles  34 ,  36 , and  38 , and a flow path switching part  40  for moving the water pumped by the pump  50  to at least one of the plurality of spray nozzles  34 ,  36 , and  38 . 
     The water supply device  70  can be configured to receive water from the outside of the dishwasher and supply the water to the sump  26 , and opens and closes a water supply valve  71   a  disposed on the water supply flow path  71  to supply external water into the sump  26 . The drain device  72  can discharge the water stored in the sump  26  to the outside of the dishwasher, and can include a drain flow path  74  and a drain pump  76 . 
     The filter  78  can filter out foreign substances such as food particles contained in the water, and can be disposed on a flow path of the water flowing from the tub  24  to the sump  26 . 
     The dishwasher  10  can further includes the pump  50  for pressurizing the water stored in the sump  26  to move the water to the spray nozzles  34 ,  36 , and  38 . The pump  50  can includes a pump housing  51 , a pump impeller  54  disposed in the pump housing  51  and rotating to supply water to the spray nozzles  34 ,  36 , and  38 , a motor  58  for rotating the pump impeller  54 , and a heater  56  for heating the water inside the pump housing  51 . 
     The pump  50  can be connected to the sump  26  through a water supply tube  60  and can be connected to the flow path switching part  40  through a water outlet pipe  62 . A branch pipe  66  can be provided in the water outlet pipe  62 , so that a part of the water flowing from the pump  50  can flow to an air jet generator  100  through the branch pipe  66 . 
     Steam generated by the heater  56  disposed in the pump  50  can flow to a steam nozzle  48  through a steam discharge pipe  64 , and can be supplied into the tub  24  through the steam nozzle  48 . 
     The dishwasher can further include the air jet generator  100  that can generate micro air bubbles in the water. 
     In the dishwasher  10 , a part of the water moved by the pump  50  is supplied to the air jet generator  100  in addition to the spray nozzles  34 ,  36 ,  38  through the branch pipe  66 . In the air jet generator  100 , the water can be supplied through a flow path branched from the pump  50  and air can be introduced into the supplied water, and the air jet generator  100  can crash or pulverize the introduced air to generate micro air bubbles. The air jet generator  100  can be connected to the tub  24  or the sump  26 . In some implementations, when the pump is operated, the water with the air bubbles generated by the air jet generator  100  can be supplied into the sump  26 , so the water pumped to the spray nozzles  34 ,  36 , and  38  includes the air bubbles. 
     A bottom hole can be defined at a bottom of the tub  24  so that a portion of an upper side of the air jet generator  100  can pass the bottom hole. The upper side of an air crushing pipe  110  of the air jet generator  100  (see  FIG. 2 ) can pass through the bottom hole. In some implementations, a portion of the upper side of the air crushing pipe  110  of the air jet generator  100  can be disposed above a bottom of the tub  24 . 
     The water stored in the sump  26  of the dishwasher  10  can be supplied to the spray nozzles  34 ,  36 , and  38  through the pump  50 , and the water supplied to the spray nozzles  34 ,  36 , and  38  can be sprayed into the tub  24 , and the water sprayed into the tub  24  can be introduced to the sump  26  again. In some implementations, a part of the water pumped from the pump  50  can be introduced into the air jet generator  100  that generates air bubbles in the water. A part of the water flowing by the pump  50  can flow to the air jet generator  100  through the branch pipe  66 . 
     A part of the water discharged from the pump  50  can be supplied to the air jet generator  100 . The air jet generator  100  can move the introduced water to pass through an impeller  170 , an air inlet hole  150 , an air crushing pipe  110  including a first tube  120  and a second tube  130 , and an air tab  180  so as to generate air bubbles in the water (see  FIG. 3 ). For example, the water introduced into the air jet generator  100  can spirally flow by the impeller  170 . Thereafter, the water can increase in speed while passing through the first tube  120 , and the air introduced into the air inlet hole can be primarily crushed or pulverized by the water rotating at a high speed by the impeller  170  and the first tube  120 . In addition, the water can be secondarily crushed or pulverized while passing through the second tube  130 . In addition, as the water is tertiarily crushed while passing through the air tab  180 , micro air bubbles can be included in the water. 
     The water including the air bubbles can be introduced into the sump  26  again. The water including the air bubbles can be discharged through the tub  24  and introduced into the sump  26 . Therefore, when the pump  50  is operated upon the operation of the dishwasher  10 , air bubbles can be generated in the water. 
     Hereinafter, the configuration and arrangement of the air jet generator will be described with reference to  FIGS. 2 to 6 . 
     The air jet generator  100  can be disposed at a bottom surface  25  of the tub  24 . The air jet generator  100  can be disposed at an edge of the bottom surface  25  of the tub  24 . 
     A mounting hole through which a part of the air jet generator  100  passes through can be defined at the bottom surface  25  of the tub  24  at a portion where the air jet generator  100  is mounted. 
     Referring to  FIGS. 2 to 3 , the air jet generator  100  can include the air crushing pipe  110  that provides a flow path perpendicular to the bottom surface  25  of the tub  24  or the ground and that has the shape of a Venturi tube, and has the air inlet hole  150  defined at one side of the air crushing pipe  110  to introduce external air, an air tab  180  that is configured to crush or pulverize air contained in the water discharged from the air crushing tube, and an air chamber  152  that is disposed at an outer side of the air crushing tube, that defines a space through which air flows, and that has an air inlet hole defined at one side of the bottom of the air chamber  152  to provide fluid communication with the inside of the air crushing tube. In some implementations, the air jet generator  100  can further include the impeller  170  that applies a centrifugal force to the water flowing into the air crushing tube. 
     Referring to  FIGS. 2 to 3 , the dishwasher  10  can have a connection pipe  68  that moves a part of the water flowing from the pump  50  to the spray nozzles  34 ,  36 ,  38  to the air jet generator  100 . An end of the connecting pipe  68  can be coupled to a lower portion of the air crushing pipe  110 . The connecting pipe  68  and the air crushing pipe  110  can be coupled by fusion bonding. 
     The connection pipe  68  can move a part of the water flowing through the water outlet pipe  62  to the air jet generator  100 . For example, the connection pipe  68  can be branched from the water outlet pipe  62  and can be connected to the air jet generator  100 . 
     The impeller  170  can be configured to apply a centrifugal force to the water flowing into the air crushing pipe  110  and can be disposed at an end of the connection pipe  68 . The impeller  170  can be mounted inside one side of the connection pipe  68 . The impeller  170  can be coupled to the inside of the connection pipe  68  by fusion bonding. 
     Referring to  FIG. 3 , the impeller  170  can include a cylindrical outer wall  172  and a vane  174  disposed within the outer wall  172  to form a swirl flow in the water. The water passing through the impeller  170  can pass through the vane  174  and can thereby be rotated to cause a swirling flow. 
     The vane  174  of the impeller  170  can apply centrifugal force to the water flowing into the first tube  120 . The vane  174  of the impeller  170  can be fixed or rotatable, and the water passing through the vane  174  can be swirled and introduced into the air crushing pipe  110 . 
     Referring to  FIG. 3 , the air crushing pipe  110  can have a Venturi tube shape. The air crushing pipe  110  can crush or pulverize air introduced into the air inlet hole  150  with the water flowing therein. 
     The air crushing pipe  110  can include the first tube  120  in which the cross-sectional area of a flow path decreases in a flow direction of the water to depressurize the water flowing therein, and the second tube  130  in which the cross-sectional area of a flow path increases in a flow direction of the water to pressurize the water containing air. The first tube  120  and the second tube  130  can each provide a flow path opened in a vertical direction. The first tube  120  can be disposed at the upstream of the second tube  130 . The first tube  120  can be disposed at a position lower than that of the second tube  130 . 
     The air inlet hole  150  for introducing external air into the air crushing pipe  110  by applying negative pressure occurring in the tube can be defined at a circumferential surface of a lower end of the second tube  130 . The air inlet hole  150  can be defined at an upstream end of the second tube  130 . 
     The air crushing pipe  110  can be disposed below the bottom surface  25  of the tub  24 . The air crushing pipe  110  can be disposed to be perpendicular to the ground or the bottom surface  25  of the tub  24 . 
     Referring to  FIG. 3 , in the air crushing pipe  110 , the first tube  120  and the second tube  130  can be disposed in order in a direction in which the water flows. 
     Referring to  FIG. 3 , the air tab  180  can be mounted at a discharge end of the air crushing pipe  110  from which the water is discharged. The air tab  180  can be disposed above the air crushing pipe  110 . 
     Referring to  FIG. 3 , the second tube  130  can be disposed above the first tube  120 . The second tube  130  can be disposed at the downstream of the first tube  120 . In the second tube  130 , the cross-sectional area of the flow path of increases in the flow direction of the water, thereby pressurizing the water. As the water flowing along the second tube  130  is pressurized, the air introduced into the air crushing pipe  110  through the air inlet hole  150  can be secondarily crushed. 
     The second tube  130  can be longer than the first tube  120 . The second tube  130  can be divided into a second tube lower part  132  for primarily pressurizing the water introduced from the first tube and a second tube upper part  134  for secondarily pressurizing the water passing through the second tube lower part  132 . The second tube lower part  132  can pressurize the water gradually compared to the second tube upper part  134 . The second tube lower part  132  can have a smaller rate of change of the flow path cross-sectional area than that of the second tube upper part  134 . 
     For example, referring to  FIG. 3 , a flow path length formed in the vertical direction of the second tube lower part  132  is longer than a flow path length of the second tube upper part  134 . A difference in inner diameter between both ends of the second tube lower part  132  in the vertical direction can be less than a difference in inner diameter between both ends of the second tube upper part  134  in the vertical direction. 
     In the second tube lower part  132 , the air introduced into the air inlet hole  150  can be crushed or pulverized by the flow velocity of the water and the centrifugal force. The second tube upper part  134  can pressurize the water due to the rapid expansion of the flow path cross-sectional area, so that the air contained in the water can be effectively crushed. 
     The air inlet hole  150  can be defined at an upstream end of the second tube  130 . The air inlet hole  150  can be defined at a lower end  132   a  of the second tube  130 . 
     Referring to  FIG. 3 , the air inlet hole  150  can be defined between the first tube  120  and the second tube  130 . The air inlet hole  150  can be defined at a portion where the flow path cross-sectional area of the first tube  120  is reduced. The air inlet hole  150  can be defined at an upstream end of the second tube  130 . The air inlet hole  150  can be defined at a point where depressurization by the first tube  120  ends. The air inlet hole  150  can be defined at a point where pressurization by the second tube  130  starts. 
     The air inlet hole  150  can provide fluid communication between the inside of the air crushing pipe  110  and the outside of the air crushing pipe  110  through the air chamber  152 . In the air crushing pipe  110 , external air may be introduced into the air crushing pipe  110  through the air inlet hole  150 . For example, the term “external air” may refer to the external air of the air crushing tube. Accordingly, “external air” may include internal air of a cabinet  20  or internal air of a tub  24 . 
     The water flowing through the air crushing pipe  110  can be depressurized while passing through the first tube  120 . Since negative pressure is formed due to the depressurization of the water passing through the first tube, external air can be suctioned into the air crushing pipe  110  through the air inlet hole  150 . The air introduced into the air crushing pipe  110  through the air inlet  150  hole can be primarily crushed or pulverized by a swirl flow of water flowing at a high speed along the first tube  120 . 
     Referring to  FIG. 3 , the air chamber  152  for reducing noise occurring in the air crushing pipe  110  can be disposed at one side of the air crushing pipe  110 . The air chamber  152  can reduce noise that propagates to the outside through the air inlet hole  150 . 
     The air chamber  152  can provide a space in which noise propagates. The air chamber  152  can be disposed at the outside of the air crushing pipe  110  in which the air inlet hole  150  is defined. The air inlet hole  150  that is in fluid communication with the inside of the air crushing pipe  110  is defined at one side of the lower end of the air chamber  152 . 
     Referring to  FIG. 3 , the air inlet hole  150  can be defined at a lower end of the air chamber  152 . Therefore, even if the water flows into the air chamber  152 , the water may not be allowed to flow to the air inlet hole  150  defined at the lower end of the air chamber  152 , so that the water is not pooled in the air chamber  152 . In the air chamber  152 , an external air inlet hole  154  through which external air is introduced into the air chamber  152  can be defined. The external air inlet hole  154  can be defined at an upper end of the air chamber  152 . Therefore, the water introduced into the air chamber  152  can be blocked from escaping to the outside of the air chamber  152 . 
     The air chamber  152  can be disposed at an outside of the air crushing pipe  110  in which the air inlet hole  150  is defined. 
     Referring to  FIG. 3 , the air crushing pipe  110  can include a tub mounting part that is coupled to the bottom surface  25  of the tub  24 . The tub mounting part can be defined at an outer circumference of the air crushing pipe  110  at an upper side of the second tube  130 . The tub mounting part can include a lower fixing plate  138  protruding in a circumferential direction from an outer circumferential surface of the air crushing pipe  110 , and a upper fixing part  140  protruding upward from the bottom surface of the tub  24  and coupled to a fixing ring  190 . 
     The bottom surface of the tub  24  can be disposed between the lower fixing plate  138  and the fixing ring  190  coupled to the upper fixing part  140 . The upper fixing part  140  can be combined with the fixing ring  190  to reduce downward movement of the air crushing pipe  110 . 
     The fixing ring  190  can have a ring shape and can be coupled to the upper fixing part  140  of the air crushing pipe  110 . An inner circumferential surface of the fixing ring  190  can provide a thread corresponding to the upper fixing part  140 . 
     The bottom surface  25  of the tub  24  can be disposed between the lower fixing plate  138  and the fixing ring  190  of the air crushing pipe  110 . A sealer for reducing leakage of the water flowing on the bottom surface  25  of the tub  24  from leaking downward can be disposed between the lower fixing plate  138  of the air crushing pipe  110  and the fixing ring  190 . The sealer can be disposed below and/or above the bottom surface  25  of the tub  24 . 
     The air tab  180  can have a disk shape, and a plurality of holes  182  penetrating the air tab  180  can be provided. The water passing through the second tube  130  can pass through the air tab  180 . Air in the water can be tertiarily crushed while passing through the plurality of holes  182  provided in the air tab  180 . 
     The larger the contact area with the air bubbles, the greater the shear force can be applied to the air bubbles, which can increase the amount of air bubbles. Thus, the holes  182  provided in the air tab  180  can be a long hole type compared to a through hole type. 
     A nozzle  200  can be disposed above the air crushing pipe  110 . The nozzle  200  can be disposed above the air jet generator  100  and configured to discharge the water passing through the air jet generator  100  into the tub  24 . The nozzle  200  can be disposed above the air tab  180 . The nozzle  200  can be coupled to the air tab  180  by fusion bonding. 
     Referring to  FIGS. 2 and 3 , in the nozzle  200 , a plurality of discharge holes  204  can be defined above the inlet hole  206  in a downward direction from a radially outer side of the inlet hole  206 . 
     Referring to  FIG. 2 , the plurality of discharge holes  204  can be spaced apart from each other by a predetermined distance along a circumferential surface of the nozzle  200 . As the nozzle  200  has the plurality of discharge holes  204  defined along the circumferential surface, water containing air bubbles can be discharged to the bottom surface  25  of the tub  24  in various directions. 
     In the air jet generator  100 , a flow path through which the water flows can be disposed perpendicular to the ground or the bottom surface of the tub  24 . Therefore, an area in which the water flowing through the second tube  130  does not flow due to the rapid expansion of the flow path in the second tube upper part  134  can be minimized. 
     Referring to  FIG. 4 , the pump  50  can include the pump housing  51 , the water supply tube  60  protruding outward from a circumferential surface of the pump housing  51 , and the water outlet pipe  62 . The steam discharge pipe  64  for supplying steam to the steam nozzle  48  and the branch pipe  66  for supplying a part of water to the air jet generator  100  can protrude from the circumferential surface of the water outlet pipe  62 . 
     Referring to  FIG. 4 , a control valve  69  that provides or blocks a flow of water flowing from the pump  50  to the air jet generator  100  can be disposed in the branch pipe  66 . The branch pipe  66  and the air jet generator  100  can be connected to the connection pipe  68 . The control valve  69  can be disposed at the connection pipe  68  to open and close a flow path provided in the connection pipe  68 . 
     A solenoid valve can be used for the control valve  69 . Therefore, the inside of the connection pipe  68  can be closed or opened according to a current signal. When the solenoid valve is used, the control valve  69  can be controlled to open or close the inside of the connection pipe  68  according to a cycle of the dishwasher. 
     A flow control valve for controlling an opening area of the flow path provided in the connection pipe  68  can also be used as the control valve  69 . Therefore, when the flow control valve is used, the control valve  69  can control the opening area of the inside of the connection pipe  68  according to a cycle of the dishwasher. 
     The steam discharge pipe  64  can protrude upward from the circumferential surface of the water outlet pipe  62 . A direction in which the branch pipe  66  extends from the water outlet pipe  62  can be disposed to be downward compared to a direction in which the steam discharge pipe  64  extends from the water outlet pipe  62 . Referring to  FIGS. 5 to 6 , the steam discharge pipe  64  can be connected to the water outlet pipe  62  at a higher position compared to the branch pipe  66 . 
     Referring to  FIG. 8 , the dishwasher can wash dishes while sequentially or selectively performing a preliminary wash cycle S 100 , a main wash cycle S 200 , a rinse cycle S 300 , and a dry cycle S 400 . 
     The entire operation of the dishwasher will be described briefly as follows. The preliminary wash cycle S 100  is a step of removing foreign substances mainly of protein with water at room temperature without heating the water, and water supply, washing, and drainage can be performed in the preliminary wash cycle S 100 . 
     The main wash cycle S 200  is a step of removing foreign substances remaining on dishes and the like using dishwashing detergent, and water supply, washing, and drainage can be performed in the main wash cycle S 200 . In the main wash cycle S 200 , water can be heated by a heater to remove foreign substances. In addition, in the process of the main wash cycle S 200 , steam can be supplied into the space  24   s  through the steam nozzle  48 . In the process of the main wash cycle S 200 , the dispenser can be opened to put detergent into the space  24   s.    
     The rinse cycle S 300  is a step of washing dishes having undergone through the main wash cycle using water, and water supply, rinsing, and drainage can be performed. An operation of heating water may be added in the rinse cycle. 
     The dry cycle S 400  is a step of removing water from dishes that have been washed and rinsed, and water remaining on the dishes can be removed using air heated by a heater in the dry cycle S 400 . 
     The control valve  69  can open the connection pipe  68  so that the water flows to the air jet generator  100  in the main wash cycle S 200 . For example, in the preliminary wash cycle S 100  or the rinse cycle S 300 , the control valve  69  can close the flow path inside the connection pipe  68 . 
     When the water is supplied to the air jet generator  100 , noise may be transferred to the outside of the dishwasher as the introduced air is crushed. Therefore, by reducing an operating time of the air jet generator  100 , the transfer of the noise to the outside can be reduced. In the case of the main wash cycle, when water including air bubbles is supplied toward dishes, food particles on the dishes can be effectively removed. Therefore, in the main wash cycle S 200 , the control valve  69  can open the connection pipe  68  so that the water is supplied to the air jet generator  100 . 
     Referring to  FIG. 7A , in the entire cycles, it may be understood that noise of about 50 dB is generated even in the preliminary wash cycle S 100  or the rinse cycle S 300  when water is supplied to the air jet generator  100 . However, referring to  FIG. 7B , it may be understood that the noise is at approximately 45 dB in the preliminary wash cycle S 100  or the rinse cycle S 300 , which indicates the reduction of the noise by about 10%. 
     However, in the rinse cycle S 300 , the control valve  69  can be controlled to block the water supplied to the air jet generator  100 . In this case, noise occurring in the rinse cycle can be reduced. Similarly, in the preliminary wash cycle S 100 , the control valve  69  can be controlled to block the water supplied to the air jet generator  100 . 
     In addition, in the rinse cycle S 300  and the preliminary wash cycle S 100 , the control valve  69  can also be controlled to reduce the area of the flow path formed in the connection pipe  68 . When the flow rate of the water flowing to the air jet generator  100  decreases, the amount of air introduced into the air jet generator  100  can also decrease, thereby reducing noise. 
     Referring to  FIG. 9 , the main wash cycle S 200  and the rinse cycle S 300  will be described in detail. 
     First, an operation S 210  of supplying water to the sump  26  is performed. The water can be supplied to the sump  26  from an external water source. 
     An operation S 220  of operating the pump  50  so that the water is supplied to the space  24   s  through the spray nozzles  34 ,  36 , and  38  can be performed. In addition, an operation S 230  of controlling the control valve  69  so that the connection pipe  68  or the branch pipe  66  connecting the pump  50  and the air jet generator  100  is opened can be performed. The operation S 220  of operating the pump  50  and the operation S 230  of controlling the control valve  69  can be performed simultaneously or sequentially, and the order of the operations S 220  and S 230  can be changed. 
     A part of the water supplied from the pump  50  flows to the air jet generator  100  and is then supplied to the space  24   s . As the water circulates, the air bubbles generated by the air jet generator  100  can be supplied to the dishes through the spray nozzles  34 ,  36 , and  38 . 
     In addition, an operation of S 240  of opening the dispenser to supply detergent into the space  24   s  can be performed. 
     Thereafter, the operation of the pump  50  can be stopped in operation S 250 , and the drain pump  76  can operate to discharge the water inside the sump  26  in operation S 260 . Then, as the drain pump  76  can be stopped in operation S 270 , the main wash cycle S 200  can be finished. 
     Then, an operation S 310  of re-supplying water to the sump  26  can be performed. 
     An operation S 320  of operating the pump  50  to supply the water to the space  24   s  through the spray nozzles  34 ,  36 , and  38  can be performed. In addition, an operation S 330  of controlling the control valve  69  to close the connection pipe  68  or the branch pipe  66  can be performed. The operation S 320  of operating the pump  50  and the operation S 330  of controlling the control valve  69  can be performed simultaneously or sequentially, and the order of the operations S 320  and S 330  can be changed. 
     In this case, even when the pump  50  is operated, the water does not flow to the air jet generator  100 , and thus, no noise is generated in the air jet generator  100 . 
     Then, the pump  50  is stopped in operation S 340 , and the drain pump  76  is operated in operation S 350  to drain the water in the sump  26 . When the drainage is completed, the drain pump  76  can be stopped in operation S 360 .