EP3501367A1

EP3501367A1 - Dishwasher and controlling method therefor

Info

Publication number: EP3501367A1
Application number: EP18213884.2A
Authority: EP
Inventors: Changwoo Son; Jaegwang BAE
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2017-12-21
Filing date: 2018-12-19
Publication date: 2019-06-26
Also published as: US20190191960A1; KR102408615B1; KR20190075616A

Abstract

The present invention relates to a dishwasher (1) for washing dishes and cooking utensils by spraying washing water, and a control method thereof. The control method of a dishwasher (1) according to an embodiment of the present invention includes: a water supply step of opening a water supply valve (22) to supply washing water to the sump (100) of the dishwasher; and a variable spray step of spraying the washing water by at least one of a plurality of spray arms (13, 14, 15) by changing the number of revolutions of a washing pump (150) pumping the washing water stored in the sump (100) to the at least one of the plurality spray arms (13, 14, 15) stepwise, so that the washing water can be sprayed evenly.

Description

The present invention relates to a dishwasher and a control method thereof, and more particularly, to a dishwasher for spraying washing water to wash dishes or cooking utensils, and a control method thereof.
A dishwasher is a household appliance for washing up dirt such as food wastes on the dishes or cooking utensils (hereinafter, referred to as 'washing object') by high-pressure washing water sprayed from a spray arm.
The dishwasher generally includes a tub forming a washing chamber and a sump mounted on the bottom of the tub to store washing water. Then, the washing water is moved to the spray arm by the pumping operation of a washing pump installed inside the sump, and the washing water moved to the spray arm is sprayed at high pressure through a spray hole formed in the spray arm. Then, the washing water sprayed at a high pressure impinges against the surface of the washing object, so that the dirt on the washing object falls to the bottom of the tub.
Meanwhile, the dishwasher performs rinsing by spraying washing water to the washing object so that residual dirt is removed. In this rinsing process, when performing a final rinsing of spraying the heated washing water, any residual dirt should be removed as much as possible. Thus, it is required that the washing water is sprayed evenly onto the washing object.
The present invention has been made in view of the above problems, and provides a dishwasher in which a spraying range of washing water varies during rinsing, and a control method thereof, as defined by the independent claims. The dependent claims define embodiments of the present invention.
In accordance with an aspect of the present invention, a method of controlling a dishwasher includes: a water supply step of opening a water supply valve to supply washing water to the sump; and a variable spray step of spraying the washing water by at least one of the plurality of spray arms by changing the number of revolutions of the washing pump stepwise, so that the washing water can be sprayed evenly.
In the variable spray step, the number of revolutions of the washing pump repeatedly decreases stepwise after increasing stepwise.
In the variable spray step, the number of steps in which the number of revolutions of the washing pump is increased is equal to the number of steps in which the number of revolutions is decreased.
In the variable spray step, a period in which the number of revolutions of the washing pump is changed is constant.
Among the plurality of spray arms, a spray arm which sprays the washing water is formed in a bar shape and rotates, and, in the variable spray step, a period of change of the number of revolutions of the washing pump is equal to or larger than a maximum time during which the rotating spray arm rotates once.
Among the plurality of spray arms, a spray arm which sprays the washing water is formed in a bar shape and rotates, and in the variable spray step, a period of change of the number of revolutions of the washing pump is equal to or larger than a time during which the rotating spray arm rotates once at a minimum number of revolutions of the washing pump.
In the variable spray step, the washing pump has a constant increase/decrease width for each step of the number of revolutions.
The plurality of spray arms comprises an upper spray arm which is disposed at an intermediate portion of the tub and sprays the washing water, and in the variable spray step, the washing pump pumps the washing water to the upper spray arm.
The upper spray arm is formed in a bar shape and rotates, and in the variable spray step, a rotation speed of the upper spray arm is changed stepwise.
In the variable spray step, a spray direction of the washing water of the upper spray arm is changed stepwise.
The number of revolutions of the washing pump in the variable spray step is equal to or less than a maximum number of revolutions of the washing pump in the top spray step and is equal to or more than a maximum number of revolutions of the washing pump in the lower spray step.
The method further includes an upper spray step of maintaining the number of revolutions of the washing pump uniformly, after the variable spray step; and a drain step of stopping an operation of the washing pump and draining the washing water stored in the sump to the outside, after the upper spray step.
In the upper spray step, the number of revolutions of the washing pump maintains an average value of the number of revolutions which is changed in the variable spray step.
The method further includes a heating step of heating the washing water supplied to the sump, and, in the variable spray step, at least one of the plurality of spray arms sprays the heated washing water.
The water supply step, the heating step, and the variable spray step are a heat rinsing process, and the method further includes, before the heat rinsing process is performed, a rinsing step of mixing the washing water supplied from an external water source with a rinsing detergent, and spraying the mixed washing water by at least one of the plurality of spray arms and then draining.
In accordance with another aspect of the present invention, a dishwasher includes: a tub which accommodates a washing object; a plurality of spray arms which spray washing water into the tub and are disposed vertically; a sump which stores the washing water; a washing pump which pumps the washing water stored in the sump to at least one of the plurality of spray arms; and a controller which controls the washing pump and a heater, wherein the controller operates the heater and changes the number of revolutions of the washing motor in a stepwise manner to spray the washing water by at least one of the plurality of spray arms.
The controller repeatedly decreases the number of revolutions of the washing pump stepwise after increasing stepwise.
The controller changes the number of revolutions of the washing pump periodically.
The controller changes the number of revolutions of the washing pump with a constant increase/decrease width.
The dishwasher further includes a switching valve for selectively connecting the washing pump with at least one of the plurality of spray arms, wherein the plurality of spray arms includes an upper spray arm disposed at an intermediate portion of the tub and spraying washing water, wherein the controller controls the switching valve to connect the washing pump to the upper spray arm when the number of revolutions of the washing motor is changed stepwise.
The dishwasher further includes a drain pump for draining the washing water stored in the sump to the outside, wherein the controller changes the number of revolutions of the washing motor in a stepwise manner and then maintains uniformly, and stops an operation of the washing motor and then operates the drain pump.
The dishwasher further includes a heater for heating the washing water sprayed by the plurality of spray arms, wherein at least one of the plurality of spray arms sprays the washing water heated by the heater.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a sectional view of a dishwasher according to an embodiment of the present invention;
FIG. 2 is a block diagram of a dishwasher according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating each process in a general washing course of a dishwasher according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a control method during the heat rinsing of a dishwasher according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating a control of the number of revolutions of a washing pump in a control method of a dishwasher according to an embodiment of the present invention; and
FIG. 6 is a perspective view of an upper spray arm of a dishwasher according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are described with reference to the accompanying drawings in detail. The same reference numbers are used throughout the drawings to refer to the same or like parts. Detailed descriptions of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention.
Hereinafter, the present invention will be described with reference to the drawings for explaining a dishwasher and a control method thereof according to embodiments of the present invention.
FIG. 1 is a sectional view of a dishwasher according to an embodiment of the present invention.
The dishwasher 1 according to an embodiment of the present invention includes a case 11 that forms an outer appearance, a tub 12 in which a washing object is accommodated, a door 20 that is provided on the front surface of the tub 12 and opens and closes the tub 12, a sump 100 that is disposed below the tub 12 and stores washing water, a plurality of spray arms 13, 14, 15 that spray washing water into the tub 12, a filter 200 which filters the washing water which is sprayed from at least one of the plurality of spray arms 13, 14, 15 and collected in the sump 100, a washing pump 150 that pumps washing water stored in the sump 100, and a switching valve 130 which flows the washing water pumped by the washing pump 150 to at least one of the plurality of spray arms 13, 14, 15.
The tub 11 is formed in a hexahedron shape having an opened front surface and forms a washing chamber 12a therein. A communication hole 12c through which the washing water flows into the sump 100 is formed in a bottom 12b of the tub 11. The washing chamber 12a is provided with a plurality of racks 16 and 17 for receiving the washing object. The plurality of racks 16 and 17 include a lower rack 16 disposed at a lower portion of the washing chamber 12a and an upper rack 17 disposed at an upper portion thereof. The lower rack 16 and the upper rack 17 are vertically spaced apart and can be slid forwardly of the tub 11 to be drawn out.
The plurality of spray arms 13, 14, and 15 are disposed in the vertical direction. The plurality of spray arms 13, 14, and 15 include a lower spray arm 13 which is disposed in the lower end of the washing chamber 12a and sprays washing water from the lower side to the upper side toward the lower rack 16, an upper spray arm 14 which is disposed in a middle portion of the height direction of the washing chamber 12a that is the upper side of the lower spray arm 13, and sprays washing water from the lower side to the upper side toward the upper rack 17, and a top spray arm 15 which is disposed in the upper end of the washing chamber 12a that is the upper side of the upper spray arm 14, and sprays washing water from the upper side to the lower side toward the upper rack 17.
The lower spray arm 13 is disposed below the lower rack 16, the upper spray arm 14 is disposed between the upper rack 17 and the lower rack 16, and the top spray arm 15 is disposed above the upper rack 17. According to an embodiment, the upper spray arm 14 may spray downward toward the lower rack 16, and spray upwardly and downwardly toward both the upper rack 17 and the lower rack 16.
Each of the lower spray arm 13 and the upper spray arm 14 rotates about the center of a bar in the form of a bar. Each of the lower spray arm 13 and the upper spray arm 14 rotates by the supply of washing water. Each of the lower spray arm 13 and the upper spray arm 14 is provided with a nozzle (not shown) on the upper surface of the bar.
The plurality of spray arms 13, 14, and 15 are supplied with the washing water from the washing pump 150 through a plurality of spray arm connecting flow paths 18, 19, and 21. The plurality of spray arm connecting flow paths 18, 19, and 21 include a lower spray arm connecting flow path 18 connected to the lower spray arm 13, an upper spray arm connecting flow path 19 connected to the upper spray arm 14, and a top spray arm connecting flow path 21 connected to the top spray arm 15.
The lower spray arm 13, the upper spray arm 14, and the top spray arm 15 are supplied with the washing water from the washing pump 150 through the lower spray arm connecting flow path 18, the upper spray arm connecting flow path 19, and the top spray arm connecting flow path 21.
The sump 100 is disposed below the bottom 12b of the tub 12 to collect washing water. The sump 100 is connected to a water supply flow path 23 through which washing water supplied from an external water source flows. The water supply flow path 23 is provided with a water supply valve 22 for controlling washing water supplied from the external water source. When the water supply valve 22 is opened, the washing water supplied from the external water source flows into the sump 100 through the water supply flow path 23.
The sump 100 is connected to a drain flow path 24 for guiding the stored washing water to the outside of the dishwasher 1. The drain flow path 24 is provided with a drain pump 25 for draining the washing water in the sump 100 through the drain flow path 24. The drain pump 25 includes a drain motor (not shown) for generating a rotational force. When the drain pump 25 is operated, the washing water stored in the sump 100 flows to the outside of the case 11 through the drain flow path 24.
A filter 26 is installed in the communication hole 12c to filter the dirt from the washing water moving from the tub 12 to the sump 100. In the filter 200, a lower portion where mesh is formed is inserted into the sump 100, and an opened upper portion protrudes to the upper side of the tub 12. The washing water sprayed through the plurality of spray arms 13, 14, 15 falls to the bottom 12b of the tub 12 together with the dirt on the washing object. The washing water flowing on the bottom 12b of the tub 12 flows into the upper portion of the filter 200, passes through the mesh of lower portion, and is stored in the sump 100 after being filtered. The level of the washing water stored in the sump 100 needs to be maintained above the lower end of the filter 200, in order for filtration of the filter 200 to be smoothly performed.
The switching valve 130 selectively supplies the washing water pumped by the washing pump 150 to at least one of the lower spray arm 13, the upper spray arm 14, and the top spray arm 15. The switching valve 130 selectively connects a washing water supply path 180 and at least one of the plurality of spray arm connecting flow paths 18, 19 and 21.
The washing pump 150 supplies washing water stored in the sump 100 to at least one of the plurality of spray arms 13, 14, 15. The washing pump 150 includes a washing motor 157 that generates a rotational force and an impeller 155 that is rotated by the washing motor 157 to pump the washing water. The washing motor 157 is a motor whose RPM can be varied, and a change of the number of revolutions of the washing pump 150 (the number of revolutions per time) means a change of the RPM of the washing motor 157. The number of revolutions of the washing pump 150 can be maintained or the number of revolutions of the washing pump 150 can be changed during operation. The number of revolutions of the washing pump 150 is proportional to the flow rate of the washing water that is pumped by the washing pump 150. When the number of revolutions of the washing pump 150 is changed, the spray direction of the washing water sprayed from at least one of the plurality of spray arms 13, 14, 15 connected to the washing pump 150 is changed. When the washing pump 150 is connected to at least one of the lower spray arm 13 and the upper spray arm 14, if the number of revolutions of the washing pump 150 is changed, the rotation speed of the lower spray arm 13 and/or the upper spray arm 14 is changed.
The washing pump 150 is connected to the sump 100 and a water collecting path 170. The washing pump 150 is connected to the switching valve 130 and the washing water supply path 180. When the washing pump 150 is operated, the washing water stored in the sump 100 flows into the washing pump 150 through the water collecting path 170 and then is pumped to the switching valve 130 through the washing water supply path 180. Since the water collecting path 170 is connected to the lateral side of the washing pump 150, it is necessary that the level of the washing water stored in the sump 100 is maintained above a connection portion of the water collecting path 170 in order for the washing water to flow into the washing pump 150 during operation of the washing pump 150.
The heater 140 is coupled to the lower side of the washing pump 150 to heat the washing water in the washing pump 150. The heater 140 generates hot water by heating the washing water flowing in the washing pump 150 when the washing pump 150 operates. The washing water heated by the heater 140 is sprayed into the tub 12 through at least one of the plurality of spray arms 13, 14 and 15. According to an embodiment, the heater 140 may be disposed within the sump 100.
FIG. 2 is a block diagram of a dishwasher according to an embodiment of the present invention, and FIG. 3 is a diagram illustrating each process in a general washing course of a dishwasher according to an embodiment of the present invention.
The controller 29 controls the water supply valve 22, the washing pump 150, the drain pump 25, the switching valve 130, and the heater 140 to perform washing on the washing object. The controller 29 performs each process according to the washing course selected by the user.
The controller 29 sequentially performs a preliminary washing 1 P310, a preliminary washing 2 P320, a preliminary washing 3 P330, a main washing P340, a rinsing P350, and a heat rinsing P360.
The plurality of preliminary washings P310, P320, P330 is a process for spraying washing water on the washing object to remove dirt attached to the washing object. In each of the plurality of preliminary washings P310, P320, P330, the controller 29 controls the water supply valve 22 to supply the washing water from an external water source into the sump 100. After the water supply, the controller 29 operates the washing pump 150 to pump the washing water in the sump 100 and controls the switching valve 130 to spray washing water through at least one of the plurality of spray arms 13. The washing water sprayed through at least one of the plurality of spray arms 13, 14, 15 drops the dirt attached to the washing object onto the bottom 12b of the tub 12 so that the dirt can be collected by the filter 26. After spraying the washing water, the controller 29 operates the drain pump 25 to drain the washing water in the sump 100 to the outside.
In the present embodiment, it is illustrated that the preliminary washing P310, P320, P330 is performed three times. However, according to an embodiment, it may be performed various times, e.g., once or more.
The main washing P340 is a process for spraying heated washing water onto the washing object so as to heat the washing object, and removing the dirt attached to the washing object. The controller 29 controls the water supply valve 22 to supply the washing water from an external water source to the sump 100, controls the heater 140 to heat the washing water, operates the washing pump 150 to spray the heated washing water through at least one of the plurality of spray arms 13, 14, 15, and operates the drain pump 25 to drain the washing water in the sump 100 to the outside. During the main washing P340, the washing detergent may be mixed with the washing water.
The rinsing P350 is a process for removing residual dirt attached to the washing object. In the rinsing process P350, the controller 29 controls the water supply valve 22 to supply the washing water from an external water source to the sump 100, operates the washing pump 150 to spray the washing water through at least one of the plurality of spray arms 13, 14, 15, and operates the drain pump 25 to drain the washing water in the sump 100 to the outside. During the rinsing P350, the rinsing detergent may be mixed with the washing water.
The heat rinsing P360 is a process for heating the washing object by spraying the heated washing water onto the washing object, and finally removing the residual dirt attached to the washing object. In the heat rinsing process P360, the controller 29 controls the water supply valve 22 to supply the washing water from the external water source to the sump 100, controls the heater 140 to heat the washing water, operates the washing pump 150 to spray the heated washing water through at least one of the plurality of spray arms 13, 14, 15, and operates the drain pump 25 to drain the washing water in the sump 100 to the outside.
FIG. 4 is a diagram illustrating a control method during the heat rinsing of a dishwasher according to an embodiment of the present invention.
The controller 29 performs water supply P361 of the heat rinsing P360. The controller 29 controls the water supply valve 22 to supply the sump 100 with washing water from an external water source. When the controller 29 opens the water supply valve 22, the washing water supplied from the external water source flows into the sump 100 through the water supply flow path 23. The controller 29 controls the water supply valve 22 such that the level of the washing water supplied to the sump 100 at the maximum rotation speed of the washing pump 150 is equal to or higher than the water level (filterable water level) at which the filtration of the dirt can be smoothly performed in the filter 200 and the water level (washing water circulatable level) at which the washing water can be flowed by the washing pump 150. The controller 29 closes the water supply valve 22 and terminates the water supply P361 when the washing water is supplied to a target water level.
When the water supply P361 is completed, the controller 29 performs a first top spray P362. In the first top spray P362, the controller 29 operates the heater 140 to heat the washing water. In addition, the controller 29 controls the switching valve 130 to connect the washing water supply path 180 and the top spray arm connecting flow path 21 so that the washing pump 150 is connected to the top spray arm 15. The controller 29 operates the washing pump 150 to pump the washing water stored in the sump 100 to the top spray arm 15. The controller 29 sprays the heated washing water through the top spray arm 15 downward toward the upper rack 17.
The controller 29 gradually increases the rotation speed of the washing pump 150 until the level of the washing water supplied to the sump 100 in the first top spray P362 is lowered to reach the filterable water level and the washing water circulatable level (the highest target rotation speed). When the number of revolutions of the washing pump 150 reaches the maximum target number of revolutions, the controller 29 maintains this number of revolutions for a predetermined time and then completes the first top spray P362.
When the first top spray P362 is completed, the controller 29 performs a first lower spray P363. In the first lower spray P363, the controller 29 continuously operates the heater 140, and controls the switching valve 130 to connect the washing water supply path 180 and the lower spray arm connecting flow path 18 so that the washing pump 150 is connected to the lower spray arm 13. The controller 29 lowers the number of revolutions of the washing pump 150 to the extent that the washing water can be sprayed through the lower spray arm 13 (the minimum target number of revolutions). The controller 29 operates the washing pump 150 without stopping after the first top spray P362 while reducing only the number of revolutions of the washing pump 150 so that the washing water stored in the sump 100 is pumped to the lower sandstone 13. The controller 29 sprays the heated washing water through the lower spray arm 13 upwardly toward the lower rack 16.
When the number of revolutions of the washing pump 150 reaches the minimum target number of revolutions, the controller 29 maintains this number of revolutions for a predetermined time and temporarily stops the operation of the washing pump 150, operates the washing pump 150 again, and controls the number of revolutions of the washing pump 150 to be the minimum target number of revolutions. When the number of revolutions of the washing pump 150 reaches the minimum target number of revolutions, the controller 29 maintains this number of revolutions for a predetermined time and then terminates the first lower spray P363.
When the first lower spray P363 is completed, the controller 29 performs a first variable spray P364. In the first variable spray P364, the controller 29 continuously operates the heater 140, and controls the switching valve 130 to connect the washing water supply path 180 and the upper spray arm connecting flow path 19 so that the washing pump 150 is connected to the upper spray arm 14. The controller 29 changes the number of revolutions of the washing pump 150 in a stepwise manner. In the first variable spray P364, the controller 29 repeats the stepwise decrease of the number of revolutions of the washing pump 150 after a stepwise increase. In the first variable spray P364, when the controller 29 changes the number of revolutions of the washing pump 150 in a stepwise manner, the number of revolutions of the upper spray arm 14 is changed in a stepwise manner, and the spray direction of the washing water is also changed in a stepwise manner.
The controller 29 changes the number of revolutions of the washing pump 150 to be equal to or lower than the maximum target number of revolutions of the washing pump 150 in the first top spray P362 and to be equal to or higher than the minimum target number of revolutions of the washing pump 150 in the first lower spray (P363). The controller 29 controls the number of revolutions of the washing pump 150 to vary between the maximum number of revolutions of the washing pump 150 in the first top spray P362 and the maximum number of revolutions of the washing pump 150 in the first lower spray P363.
A detailed description of the first variable spray P364 will be given later with reference to FIG. 5 and the following.
The controller 29 changes only the number of revolutions of the washing pump 150 and operates the washing pump 150 without stopping after the first lower spray P363 so that the washing water stored in the sump 100 is pumped to the upper spray arm 14. The controller 29 sprays the heated washing water through the upper spray arm 14 upwardly toward the upper rack 17. The controller 29 changes the number of revolutions of the washing pump 150 in a stepwise manner for a predetermined time and then terminates the first variable spray P364.
When the first variable spray P364 is completed, the controller 29 performs a second top spray P365. In the second top spray P365, similarly to the first top spray P362, the controller 29 continuously operates the heater 140 and controls the switching valve 130 such that the washing pump 150 is connected to the top spray arm 15 and the number of revolutions of the washing pump 150 is increased to the maximum target number of revolutions.
When the second top spray P365 is completed, the controller 29 performs the second lower spray P366. In the second lower spray P366, similarly to the second lower spray P366, the controller 29 continuously operates the heater 140 and controls the switching valve 130 to connect the washing pump 150 to the lower spray arm 13, and reduces the number of revolutions of the washing pump 150 to the minimum target number of revolutions. In the second lower spray P366, the controller 29 temporarily stops the operation of the washing pump 150 in the middle of maintaining the minimum target number of revolutions of the washing pump 150.
When the second lower spray P366 is completed, the controller 29 performs a second variable spray P367. In the second variable spray P367, similarly to the first variable spray P364, the controller 29 continuously operates the heater 140 and controls the switching valve 130 to connect the washing pump 150 to the upper spray arm 14, and changes the number of revolutions of the washing pump 150 in a stepwise manner.
When the second variable spray P367 is completed, the controller 29 performs an upper spray P368. In the upper spray P368, the controller 29 stops the operation of the heater 140 and terminates the heating of the washing water. The stop of the operation of the heater 140 may be accomplished at the beginning or at the end of the upper spray P368. In the upper spray P368, the controller 29 maintains the switching valve 130 to connect the washing pump 150 and the upper spray arm 14 after the second variable spray P367. In the upper spray P368, the controller 29 operates the washing pump 150 without stopping after the second variable spray P367, but maintains the number of revolutions of the washing pump 150 uniformly. The controller 29 controls the number of revolutions of the washing pump 150 to be the average value (or the intermediate value between the maximum number of revolutions and the minimum number of revolutions) of the number of revolutions of the washing pump 150 in the second variable spray P367 (or in the first variable spray P364) and then maintains this number of revolutions. In the upper spray P368, the controller 29 maintains the number of revolutions of the washing pump 150 so that the filterable water level, the washing water circulatable water level, and the washing water spray flow amount through the upper spray P368 can be ensured, and collects dirt into the filter 200 and collects washing water into the sump 100. The controller 29 maintains the number of revolutions of the washing pump 150 for a predetermined time, and then stops the operation of the washing pump 150 to terminate the upper spray P368.
When the upper spray P368 is completed, the controller 29 performs a drain (P369). The controller 29 operates the drain pump 25 to drain the washing water stored in the sump 100 to the outside. When the controller 29 operates the drain pump 25, the washing water stored in the sump 100 flows to the outside of the case 11 through the drain flow path 24. When all of the washing water stored in the sump 100 is drained, the controller 29 stops the operation of the drain pump 25 and terminates the heat rinsing P360.
In the above-described embodiment, the second top spray P365, the second low spray P366, and the second variable spray P367 may be omitted. In this case, after the first variable spray P364, the upper spray P368, and the drain P369 may be performed sequentially.
In the embodiment described above, it is illustrated that the upper spray arm 14 sprays the washing water in the steps of the first variable spray P364 and the second variable spray P367. However, according to an embodiment, the lower spray arm 13 may spray the washing water.
FIG. 5 is a diagram illustrating a control of the number of revolutions of a washing pump in a control method of a dishwasher according to an embodiment of the present invention, and FIG. 6 is a perspective view of an upper spray arm of a dishwasher according to an embodiment of the present invention.
FIG. 5 shows the number of revolutions of the washing pump 150 depending on time in the first variable spray P364 and the second variable spray P367. In FIG. 5, x denotes a period in which the number of revolutions of the washing pump 150 is changed, and y denotes a stepwise increase/decrease width in which the number of revolutions of the cleaning pump 150 is changed. yz denotes the total increase/decrease width of the change in the number of revolutions of the washing pump 150. z denotes the number of the increasing and decreasing steps of the number of revolutions of the washing pump 150, and is not shown in the Fig.
It is preferable that the period x of change of the number of revolutions of the washing pump 150 is equal to or larger than a maximum time during which the upper spray arm 14 rotates once. The rotation speed w of the upper spray arm 14 is changed according to the number of revolutions the washing pump 150, and the rotation speed w of the upper spray arm 14 becomes the lowest when the number of revolutions of the washing pump 150 is the lowest. The time for one rotation of the upper spray arm 14 becomes the maximum when the rotation speed w of the upper spray arm 14 is the lowest. It is preferable that the period x of change of the number of revolutions is equal to or larger than the time of one revolution at the minimum number of revolutions of the washing pump 150.
The period x of change of the number of revolutions of the washing pump 150 is equal to the period of time during which the number of revolutions of the washing pump 150 is maintained. Since the spray direction of the washing water sprayed from a nozzle 14a of the upper spray arm 14 is maintained uniformly when the number of revolutions of the washing pump 150 is maintained, the upper spray arm 14 is rotated at least one revolution in the same spray direction so that the washing water is uniformly sprayed on the horizontal plane. In the present embodiment, the period x of change of the number of revolutions of the washing pump 150 is 5 seconds.
The spray direction of the washing water may be evenly changed during a stepwise change in which the number of revolutions of the washing pump 150 is maintained uniformly and then rapidly changed and maintained uniformly again. The spray direction of the washing water is related not only to the opening direction of the nozzle 14a and the flow rate of washing water depending on the number of revolutions of the washing pump 150 but also to the rotation speed of the upper spray arm 14. According to such a complex factor, the inventors of the present invention have experimentally found that the spray direction of the washing water is changed evenly to be evenly applied to the washing object, when the number of revolutions of the washing pump 150 is changed to the period x of change of the number of revolutions of the washing pump 150 in a stepwise manner in comparison with the case where the number of revolutions of the washing pump 150 is gradually changed linearly or curvedly.
The washing pump 150 repeats the stepwise decrease in the number of revolutions after the stepwise increase. The number z of steps of increasing the number of revolutions of the washing pump 150 is preferably equal to the number z of steps of decreasing the number of revolutions. It is preferable that the number z of steps of increasing or decreasing the number of revolutions is an even number such that the number of revolutions of the washing pump 150 is maintained for the period x of change at the average value (intermediate value between the maximum number of revolutions and the minimum number of revolutions) for the number of revolutions of the washing pump 150.
It is preferable that all the increase/decrease width y of each step is constant when the number of revolutions of the washing pump 150 is increased and decreased. It is preferable that the total increase/decrease width yz of the change in the number of revolutions of the washing pump 150 is constant when the number of revolutions of the washing pump 150 is repeatedly increased or decreased in a stepwise manner. In the present embodiment, the number z of steps for increasing or decreasing the number of revolutions is 4, and the increase/decrease width y for each step is 200 RPM. Accordingly, in the present embodiment, the total increase/decrease width yz is 800 RPM.
The inventors of the present invention have experimentally found that when the number of revolutions of the washing pump 150 is changed ununiformly in a stepwise manner, the water level drops sharply so that the filterable water level and the washing water circulatable water level are not ensured or the washing water is not sprayed through the nozzle 14a. However, as described above, it has been found that when the number of revolutions of the washing pump 150 is changed uniformly in a stepwise manner by making the increase/decrease width y for each step to be equal to the number z of steps of increase, the washing water is continuously sprayed through the nozzle 14a while ensuring the filterable water level and the washing water circulatable water level.
According to the dishwasher of the present invention and the control method thereof, one or more of the following effects can be obtained.
First, the number of revolutions of the washing pump that pumps the washing water to the spray arm is varied stepwise so that the spray range of the washing water can be varied stepwise, thereby uniformly spraying the washing water to the washing object.
Second, the number of revolutions of the washing pump can be varied in the same period and in the same increase/decrease width, thereby ensuring the filterable water level and the washing water circulatable water level.
Third, the number of revolutions of the washing pump is changed, but the number of revolutions is maintained while the washing arm rotates at least once, so that the washing arm can rotate at least once in a certain washing water spray direction.
Fourth, the rinsing performance can be improved by repeatedly increasing and decreasing the number of revolutions of the washing pump in a stepwise manner between the spray pressure at which the washing water is sprayed to the washing arm and the spray pressure at which the lowest water level can be ensured.
Fifth, the number of revolutions of the washing pump is changed stepwise and then the number of revolutions is kept constant, thereby collecting the dirt in the filter before draining, and collecting the washing water stably in the sump.
Sixth, the washing water is sprayed evenly onto the washing object in a final process in which the heated washing water is sprayed, thereby completely removing the residual dirt in the washing object.
Hereinabove, although the present invention has been described with reference to exemplary embodiments and the accompanying drawings, the present invention is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present invention pertains without departing from the scope of the present invention claimed in the following claims.

Claims

A method of controlling a dishwasher including a tub (12) receiving a washing object, a plurality of spray arms (13, 14, 15) for spraying washing water, a sump (100) storing the washing water, and a washing pump (150) pumping the washing water stored in the sump (100) to the plurality of spray arms (13, 14, 15), the method comprising:
a water supply step of opening a water supply valve (22) to supply the washing water to the sump (100); and

a variable spray step of spraying the washing water by at least one of the plurality of spray arms (13, 14, 15) by changing the number of revolutions of the washing pump (150) stepwise.
The method of claim 1, wherein, in the variable spray step, the number of revolutions of the washing pump (150) repeatedly decreases stepwise after increasing stepwise,
wherein the number of steps in which the number of revolutions of the washing pump (150) is increased is preferably equal to the number of steps in which the number of revolutions is decreased.
The method of claim 1 or 2, wherein, in the variable spray step, a period in which the number of revolutions of the washing pump (150) is changed is constant.
The method of claim 3, wherein, among the plurality of spray arms (13, 14, 15), a spray arm which sprays the washing water is formed in a bar shape and rotates, and
wherein, in the variable spray step, a period of change of the number of revolutions of the washing pump (150) is equal to or larger than a maximum time during which the rotating spray arm rotates once, or
wherein, in the variable spray step, a period of change of the number of revolutions of the washing pump is equal to or larger than a time during which the rotating spray arm rotates once at a minimum number of revolutions of the washing pump.
The method of any one of the preceding claims, wherein, in the variable spray step, the washing pump (150) has a constant increase/decrease width for each step of the number of revolutions.
The method of any one of the preceding claims, wherein the plurality of spray arms (13, 14, 15) comprises an upper spray arm which is disposed at an intermediate portion of the tub (12) and sprays the washing water,
wherein, in the variable spray step, the washing pump (150) pumps the washing water to the upper spray arm,
wherein the upper spray arm is preferably formed in a bar shape and rotates, and
a rotation speed of the upper spray arm is changed stepwise, and/or
a spray direction of the washing water of the upper spray arm is changed stepwise in the variable spray step.
The method of any one of the preceding claims, wherein the plurality of spray arms (13, 14, 15) further comprises:
a top spray arm which is disposed in an upper end of the tub and sprays the washing water downwardly; and

a lower spray arm which is disposed in a lower end of the tub (12) and sprays the washing water upwardly,

further comprising:
a top spray step of operating the washing pump (150) to pump the washing water stored in the sump (100) to the top spray arm; and

a lower spray step of operating the washing pump (150) to pump the washing water stored in the sump (100) to the lower spray arm,

wherein the number of revolutions of the washing pump (150) in the variable spray step is equal to or less than a maximum number of revolutions of the washing pump in the top spray step and is equal to or more than a maximum number of revolutions of the washing pump (150) in the lower spray step.
The method of any one of the preceding claims, further comprising:
an upper spray step of maintaining the number of revolutions of the washing pump (150) uniformly, after the variable spray step; and

a drain step of stopping an operation of the washing pump (150) and draining the washing water stored in the sump (100) to the outside, after the upper spray step,

wherein, in the upper spray step, the number of revolutions of the washing pump (150) preferably maintains an average value of the number of revolutions which is changed in the variable spray step.
The method of any one of the preceding claims, further comprising a heating step of heating the washing water supplied to the sump (100),
wherein, in the variable spray step, at least one of the plurality of spray arms (13, 14, 15) sprays the heated washing water.
The method of claim 9, wherein the water supply step, the heating step, and the variable spray step are a heat rinsing process,
further comprising, before the heat rinsing process is performed, a rinsing step of mixing the washing water supplied from an external water source with a rinsing detergent, and spraying the mixed washing water by at least one of the plurality of spray arms (13, 14, 15) and then draining.
A dishwasher comprising:
a tub (12) which accommodates a washing object;

a plurality of spray arms (13, 14, 15) which spray washing water into the tub (12) and are disposed vertically;

a sump (100) which stores the washing water;

a washing pump (150) which pumps the washing water stored in the sump (100) to at least one of the plurality of spray arms (13, 14, 15); and

a controller (29) which controls the washing pump (150) and a heater (140),

wherein the controller (19) operates the heater (140) and changes the number of revolutions of the washing pump (150) in a stepwise manner to spray the washing water by at least one of the plurality of spray arms (13, 14, 15).
The dishwasher of claim 11, wherein the controller (29) repeatedly decreases the number of revolutions of the washing pump (150) stepwise after increasing stepwise, and/or
wherein the controller (29) changes the number of revolutions of the washing pump (150) periodically, and/or
wherein the controller (29) changes the number of revolutions of the washing pump (150) with a constant increase/decrease width.
The dishwasher of claim 11 or 12, further comprising a switching valve (130) for selectively connecting the washing pump (150) with at least one of the plurality of spray arms (13, 14, 15),
wherein the plurality of spray arms (13, 14, 15) includes an upper spray arm disposed at an intermediate portion of the tub and spraying washing water,
wherein the controller (29) controls the switching valve (130) to connect the washing pump (150) to the upper spray arm when the number of revolutions of the washing pump (150) is changed stepwise.
The dishwasher of any one of claims 11 to 13, further comprising a drain pump (25) for draining the washing water stored in the sump (100) to the outside,
wherein the controller (29) changes the number of revolutions of the washing pump (150) in a stepwise manner and then maintains uniformly, and stops an operation of the washing pump (150) and then operates the drain pump (25).
The dishwasher of any one of claims 11 to 14, further comprising a heater (140) for heating the washing water sprayed by the plurality of spray arms (13, 14, 15),
wherein at least one of the plurality of spray arms (13, 14, 15) sprays the washing water heated by the heater (140).