Patent Publication Number: US-9844801-B2

Title: Dishwasher

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2014-0071649 filed on Jun. 12, 2014 in Korea, the entire contents of which is hereby incorporated by reference in its entirety. 
     FIELD 
     The present disclosure relates to a dishwasher and a control method for a dishwasher. 
     BACKGROUND 
     Dishwashers are electric home appliances for washing contaminants such as scraps or leftover food on dishes or cookware (hereinafter, “washing objects”), using washing-up liquid and washing water. 
     A conventional dishwasher usually includes a tub configured to provide a washing space, a dish rack provided in the tub to receive washing objects thereon, and a spraying arm for spraying washing water to the dish rack. 
     Meanwhile, some of the conventional dishwashers further include a storage space for storing the water which will be used in generating the heated-water or steam supplied to the washing objects, and a heater provided in the storage space. 
     SUMMARY 
     According to an innovative aspect of the subject matter described in this application, a control method of a dishwasher that includes a spray arm configured to spray washing water to a washing object, a sump configured to provide a space where washing water is stored and to collect washing water sprayed from the spray arm, a housing configured to connect the sump and the spray arm, a heater located in the housing, an impeller located in the housing and above the heater, and a motor configured to rotate the impeller, includes the actions of supplying washing water to the sump; rotating the impeller by supplying electricity to the motor; measuring an amount of electric current supplied to the motor during the rotating of the impeller; and heating washing water located in the housing by operating the heater based on the amount of electric current supplied to the motor during the rotating of the impeller being greater than or equal to a preset reference amount. 
     The method may include one or more of the following optional features. The impeller rotates at a preset revolutions per minute (RPM) that is higher than an RPM of the impeller to spray washing water from the spray arm and lower than an RPM of the impeller to cause washing water sprayed from the spray arm to contact the washing object. The amount of the electric current supplied to the motor during the rotating of the impeller in a water level that at least contacts with the impeller, is designated as the preset reference amount. The action of measuring the amount of electric current supplied to the motor during the rotating of the impeller includes, during a preset reference time period after beginning to rotate the impeller by supplying electricity to the motor, measuring the amount of electric current supplied to the motor during the rotating of the impeller. 
     The actions further include repeating the rotating of the impeller, using electric current supplied to the motor during the heating of washing water; repeating the measuring of the amount of electric current supplied to the motor during the repeating of the rotating of the impeller using electric current supplied to the motor during the heating of washing water; and repeating the supplying of washing water to the sump, based on the amount of the electric current supplied to the motor during the repeating of the rotating of the impeller using electric current supplied to the motor during the heating of washing water not being equal to the preset reference amount. The actions further include the action of, based on the amount of electric current supplied to the motor during the rotating of the impeller being greater than or equal to the preset reference amount, stopping supply of washing water to the sump and stopping rotation of the impeller. 
     The preset reference amount is a range having a minimum amount and a maximum amount of electric current. The heating of washing water located in the housing and the repeating of the supplying washing water comprise, based on the measured amount of electric current supplied to the motor during the rotating of the impeller being in the range, heating of washing water located in the housing and repeating the supplying of washing water. The amount of electric current supplied to the motor, based on the impeller rotating with a water level at least contacting the impeller, is designated as the minimum amount of electric current. The amount of electric current supplied to the motor, based on the impeller rotating with the water level greater than or equal to a highest level of the housing, is designated as the maximum amount of electric current. 
     According to another innovative aspect of the subject matter described in this application, a dishwasher includes a tub configured to provide a washing space; a rack provided in the tub and configured to hold washing objects; a spray arm located under the rack and configured to spray washing water to the washing objects; a sump configured to provide a space where washing water is stored and to collect washing water sprayed from the spray arm; a housing connected to the sump via an inlet and to the spray arm via an outlet; an impeller rotatably located in the housing and configured to move washing water to the outlet; a motor located outside the housing and configured to rotate the impeller; a heater located in the housing and under the impeller; and a control unit configured to operate the heater based on the amount of electric current supplied to the motor. 
     The dishwasher may include the following optional feature. The control unit operates the heater based on the amount of the electric current supplied to the motor being greater than or equal to a preset reference amount. 
     It is an object of the subject matter described in this application to provide a dishwasher that may sense a level of the water stored in a space having a heater, using a pump configured to supply washing water to a spray arm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an example dishwasher. 
         FIG. 2  is a diagram of an example pump located in a dishwasher. 
         FIG. 3  is a flow chart for an example control method for a dishwasher. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example dishwasher. The dishwasher  100  includes a cabinet  1  configured to define an exterior appearance of the dishwasher  100 ; a tub  11  provided in the cabinet and configured to provide a washing space; a sump  13 , e.g., a system that re-collects the washing water stored in the tub; and a door  16  coupled to the cabinet to open and close the washing space. 
     The tub  11  and the sump  13  are partitioned off from each other by a cover  15  provided above the sump. A collecting hole  151  is provided in the cover  15  to make the tub  11  and the sup  13  communicate with each other. 
     The sump  13  includes a water supply path  131  configured to supply washing water and a drainage path  133  configured to drain the washing water from the sump. 
     The tub  11  may include racks on which washing objects, e.g., dishes, are placed. The racks include a first rack  191  and a second rack  193  provided under the first rack. For convenience sake, the first rack is called an upper rack and the second rack  193  is called a lower rack. 
     The upper rack  191  and the lower rack  193  are configured to be pulled out of the tub  11 , when the door  16  opens the washing space. For that, a rail may be provided in an inner circumferential surface of the tub from a rear surface of the dishwasher to a front surface where the door  16  is provided. Wheels may be further provided in the upper and lower racks to support the racks, respectively. 
     In some implementations, the dishwasher may include a lower arm  5  provided in the tub  11  and configured to wash the washing objects placed on the lower rack  193  and an upper arm  3  provided in the tub to wash the washing objects placed on the upper rack  191 . 
     The lower arm  5  and the upper arm  3  are provided with the washing water via a pump and a supply path  7 . 
     The supply path  5  includes a first supply path  71  connected to the lower arm  5  via an arm holder  17  provided in the cover  15  and a second supply path  73  connected to the upper arm  3 . The supply paths  71  and  73  are opened and closed by a flow-path transfer valve  75 . 
     A control unit may control the flow-path transfer valve  75  to open the supply path  71  or  73  selectively or to open the supply paths simultaneously. 
     As shown in  FIG. 2 , the pump  9  may include a housing  91  connected to the pump  13  via an inlet  93 , an outlet  92  configured to connect the housing  91  and the path-flow transfer valve  75  with each other, an impeller  96  provided in the housing  91  to flow the washing water stored in the housing to the outlet  92 , and a motor  97  provided outside the housing to rotate the impeller  96 . 
     The impeller  96  may be provided in an impeller accommodating portion  94  provided in the housing  91 . 
     The impeller accommodating portion  94  may define a space where the impeller  96  is provided and provide a path of the washing water held in the housing  91  to the outlet  92 . 
     The impeller accommodating portion  94  may include an accommodating portion inlet hole  95  in communication with an inside of the housing  91  and an accommodating portion outlet hole  99  in communication with the outlet  92 . 
     When the impeller  96  is rotated by the motor  97  provided with the electric power, the washing water supplied to the housing from the sump  13  is flowing to the impeller accommodating portion  95  via the accommodating portion inlet hole  95  and then flowing to the flow-path transfer valve  75  via the accommodating portion outlet hole  99  and the outlet unit  92 . 
     The water supplied to the flow-path transfer valve  75  is flowing to the spray arms  3  and  5  along the supply paths  71  and  73  opened by the path-flow transfer valve  75 . 
     In some implementations, the dishwasher  100  may further a heater  98  configured to heat the water stored in the housing  91  so as to supply heated-water or steam to the spray arms  3  and  5 . 
     The heater  98  may be provided in the housing  91  and, in some implementations, that the heater  98  is provided under the impeller  96 , e.g., under the accommodating portion inlet hole  95 . 
     When it is provided under the impeller  96 , the heater  98  may measure the repulsive power of the washing water which acts for the impeller  96  rotated by the motor, e.g., the load of the impeller or the load of the motor so as to determine whether the heater  98  is submerged in the washing water or not. 
     As a water level inside the housing  91  is getting higher, the load of the impeller  96  is increasing more. Accordingly, the load of the impeller  96  measured when the water level in the housing  91  is a reference level (L 1 ) which contacts with a bottom surface of the impeller  96  may be set as a reference load. When the reference load is compared with the load of the impeller  96  measured during the operation of the dishwasher after that, the water level in the housing  91  may be kept above the reference water level (L 1 ) such that the overheat of the heater  98  can be prevented. 
     According to a method for measuring the load of the impeller  96 , the load of the impeller  96  is determined based on the amount of electricity supplied to the motor  97  after the motor  97  is operated for the impeller  96  to keep a uniform revolutions per minute (RPM). 
     When the water level in the housing  91  is substantially high, the load of the impeller  96  is increasing and the amount of the electricity, or electric currents, that has to be supplied to the impeller  96  is also increasing. When the water level in the housing  91  is substantially low, the load of the impeller  96  is decreasing and the amount of the electricity, or electric currents, that have to be supplied to the impeller  96  is also decreasing. 
     In case the motor  97  is provided with the uniform-sized electricity continuously, the load of the impeller  96  may be determined based on the measured RPM of the impeller  96  to measure the load of the impeller. 
       FIG. 3  illustrates an example control method for a dishwasher. The control method is characterized in that the water level in the housing  91  where the heater  98  is provided may be measured, using the pump  9  configured to supply the washing water to the spray arms  3  and  5 . 
     The control method includes a water supply step (S 11 ) of supplying the washing water to the sump  13  via the water supply path  131 . Once the washing water is supplied to the sump  13  in the water supply step (S 11 ), the washing water inside the sump  13  may be supplied to the housing  91  via the inlet  93 . 
     In a preset time period when the water supply step (S 11 ) starts, the control method includes a driving step (S 12 ) of rotating the impeller  96 , using the electricity supplied to the motor  97 . 
     The driving step (S 12 ) is a step for rotating the impeller  96  so as to detect the water level in the housing  91 , so that the control unit may control the flow-path transfer valve  75  to supply the washing water to the lower arm  5 . 
     The path for collecting the water in the sump after the lower arm  5  is shorter than the path for collecting the water in the sump after the upper arm  3 . Accordingly, the time taken to collect the water in the sump  13  after passing the lower arm  5  is shorter than the time taken to collect the water in the sump  13  after passing the upper arm  3 . The water level in the housing  91  may be measured more precisely when the pump  9  supplies the washing water to the lower arm  5  than when it supplies the washing water to the upper arm  3 . 
     Meanwhile, an object of the driving step (S 12 ) is not to spray the washing water so as to wash the washing objects but to spray the washing water to the spray arm so as to detect the water level in the housing  91 . Accordingly, in some implementations, the driving step (S 12 ) that the impeller  96  is driven at a preset RPM which is higher than the RPM at which the impeller is driven to drain the washing water from the lower arm  5  and lower than the RPM at which the impeller is driven so as to make the washing water sprayed from the lower arm  5  to the washing objects that may be held in the lower rack  193 . 
     The driving step (S 12 ) mentioned above may be performed for a preset measurement reference time period. In a preset reference time period after the driving step (S 12 ) starts (S 13 , the reference time period is less than the measurement reference time), the control method includes a measuring step (S 14 ) of measuring the amount of the electric currents supplied to the motor  97 . 
     In an initial stage of the operation of the pump  9 , air could remain in the first supply path  21  or the second supply path  23  and the air could be sucked into the impeller  96  according to the water level in the housing  91 . 
     When air remains in the supply path  21  or  23  or air is sucked into the impeller  96 , the load of the impeller could fails to be uniform and it could be difficult to measure the amount of the electric currents supplied to the motor  97 . Accordingly, when the measuring step (S 14 ) is performed in a reference time period after the electricity starts to be supplied to the pump  9 , the load of the motor  97  may be measured precisely and the load of the impeller may be then determined precisely and effectively. 
     Once the measuring step (S 14 ) is completed, the control method may include a comparing step (S 15 ) of comparing the measured amount of the electric currents with the reference amount of electric currents. 
     The experimental number of the electricity, or electric currents, supplied to the motor  97 , when the driving step (S 12 ) is performed in a state where the water level in the housing  91  is the water level (the reference water level, L 1 ) or higher at which the water contacts with the impeller  96 , may be set as the reference amount of the electric currents. 
     Meanwhile, the reference amount of the electric currents may be set in a range having the minimum amount and the maximum amount of the electric currents. 
     In this instance, the experimental number of the electricity, or electric currents, supplied to the motor  97  when the driving step (S 12 ) is performed in a state where the water level in the housing  91  is the reference level (L 1 ) may be set as the minimum amount of the electric currents. The experimental number of the electricity, or electric currents, supplied to the motor  97  when the driving step (S 12 ) is performed in a state where the water level in the housing  91  is the highest water level (L 2 ) in the housing  91 . 
     When the amount of the electric currents measured in the measuring step (S 14 ) is equal to the reference amount, the control method may include a water-supply stopping step (S 16 ), a pump stopping step (S 17 ) and a heating step (S 21 ) of operating the heater  98  after the water-supply stopping step (S 16 ) and the pump stopping step (S 17 ) so as to heat the washing water. 
     In case the reference amount of the electric currents is set in a range having the minimum amount and the maximum amount of the electric currents, the water-supply stopping step (S 16 ), the pump stopping step (S 17 ) and the heating step (S 21 ) starts when the amount of the electric currents measured in the measuring step (S 14 ) is the minimum amount or more and the maximum amount of lower. 
     The heating step (S 21 ) is the step of heating the washing water stored in the housing  91  so as to generate heated-water or steam. 
     The heated-water or steam generated in the heating step (S 21 ) may be supplied to the washing objects via the spray arms along the supply paths  71  and  73  selectively open by the flow-path transfer valve  75 . At this time, the steam may be supplied to the washing objects via a steam supply pipe configured to connect the housing  91  and the tub  11  with each other. 
     The heating step (S 21 ) is performed for a preset time period. In other words, when it is determined (S 22 ) that the duration time of the heating step (S 21 ) passes the preset time period, the control method stops the operation of the heater  98  (S 31 ) and ends the control of the dishwasher after that. 
     Meanwhile, during the heating step, the water level in the housing might decrease. The control method may further include a second driving step (S 23 ) and a second measuring step (S 24 ) to as to measure the water level in the housing  91  during the heating step (S 21 ). 
     The second driving step (S 23 ) is the step of rotating the impeller  96 , using the electricity supplied to the motor  97  during the heating step. The second measuring step (S 24 ) is the step of measuring the electric currents supplied to the motor  97  to perform the second driving step. 
     The RPM of the impeller in the second driving step (S 23 ) may be equal to the RPM of the impeller in the driving step (S 12 ) mentioned above. 
     In other words, in some implementations, that the RPM of the impeller  96  in the second driving step (S 23 ) is higher than the RPM of the impeller driven to spray the washing water from the lower arm  5  and lower than the RPM of the impeller driven to make the washing water sprayed from the lower arm  5  contact with the washing objects which may be held in the lower rack  193 . 
     Once the mount of the electric currents supplied to the motor  97  in the second driving step (S 23 ) is measured in the second measuring step (S 24 ), the control method performs a comparing step (S 25 ) of comparing the amount of the electric currents measured in the second measuring step with the reference amount. 
     When the amount of the electric currents measured in the second measuring step (S 24 ) is equal to the reference amount, the supply of the electricity to the motor  97  is cut off (S 41 ) and it is determined whether a preset time set in the heating step passes. 
     However, when the amount of the electric currents measured in the second measuring step (S 24 ) is not equal to the reference amount, the control method may perform an additional water supply (S 26 ) of supplying washing water to the sump  13  and then a comparing step (S 25 ) of comparing the measured amount with the reference amount of the electric currents.