WO2008016283A1

WO2008016283A1 - Dishwasher and method of controlling the same

Info

Publication number: WO2008016283A1
Application number: PCT/KR2007/003755
Authority: WO
Inventors: Tae-Hwan Cho; Hong-Ki Kang
Original assignee: Lg Electronics Inc.
Priority date: 2006-08-04
Filing date: 2007-08-03
Publication date: 2008-02-07
Also published as: AU2007279512B2; RU2390304C1; AU2007279512A1; EP2046187A1; EP2046187A4

Abstract

Timing for restoring an ion resin of a water softening unit of a dishwasher is determined by detecting hardness of washing water. Therefore, the ion resin can be timely restored.

Description

DISHWASHER AND METHOD OF CONTROLLING THE

SAME

Technical Field

[1] The present disclosure relates to a dishwasher that washes dishes by spraying washing water to food residues adhered to the dishes.

[2]

Background Art

[3] A water softener for softening the washing water is installed in the dishwasher. The water softener includes a water softening unit in which ion resin for removing and adsorbing heavy metals and metal ions and a restoring unit storing salt and improving the water softening performance by restoring the ion resin.

[4]

Disclosure of Invention Technical Problem

[5] However, in the prior art water softener, if the ion resin in which the heavy metals and metal ions are adsorbed is not timely restored, the washing water is not sufficiently softened and thus the washing performance of the dishwasher is significantly deteriorated. Further, a surface of a tub is stained by the heavy metals or metal ions that are still contained in the washing water.

[6] In addition, since a user cannot identify if an amount of salt contained in a restoring container is sufficient, it is difficult to restore the ion resin at the appropriate time. That is, it is difficult for the user to timely refill the restoring container with the salt. Technical Solution

[7] Embodiments provide a dishwasher and a method of controlling the dishwasher, which can restore a water softener at a proper period and maintain a proper concentration of the restoring solution.

[8] In one embodiment, a dishwasher includes a water softening unit storing ion resin, a restoring unit storing restoring solution for restoring the ion resin of the water softening unit, a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit, a hardness detecting unit detecting hardness of the washing water supplied, and a controller opening and closing the restoring valve in accordance with the hardness detected by the hardness detecting unit.

[9] In another embodiment, a dishwasher includes a water softening unit storing ion resin, a restoring unit storing restoring solution for restoring the ion resin of the water softening unit, a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit, a hardness detecting unit that is installed at a softened water outlet side of the water softening unit to detect hardness of the washing water supplied, and a controller opening and closing the restoring valve in accordance with the hardness detected by the hardness detecting unit.

[10] In still another embodiment, a dishwasher includes a water softening unit storing ion resin, a restoring unit storing restoring solution restoring the ion resin of the water softening unit, a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit, first and second hardness detecting units that are respectively installed near an outlet side and an inlet side of the water softening unit to detect hardness of the washing water supplied and discharged, and a controller opening and closing the restoring valve in accordance with a hardness difference between the hardness detected by the first hardness detecting unit and the hardness detected by the second hardness detecting unit.

[11] In still yet another embodiment, a method of controlling a dishwasher includes detecting hardness of washing water discharged from a water softening unit and controlling timing for supplying restoring solution to the water softening unit when the detected hardness is greater than a predetermined valve.

[12] In still further yet another embodiment, a method of controlling a dishwasher includes detecting hardness of washing water at an inlet side and an outlet side of a water softening unit and controlling a timing for supplying restoring solution to the water softening unit when a hardness difference at the inlet side and an outlet side of the waster softening unit.

[13] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

[14]

Advantageous Effects

[15] With the dishwasher and the control method as above, it has an effect that a water softener can be restored at a proper period and maintain a proper concentration of the restoring solution can be maintained in a dishwasher. Brief Description of the Drawings

[16] Fig. 1 is a perspective view of a dishwasher according to an embodiment.

[17] Fig. 2 is a perspective view of a sump, water supply unit, and water softener of FIG.

1. [18] Fig. 3 is a perspective view of a water softener of a dishwasher according to a first embodiment. [19] Fig. 4 is a block diagram of a control unit of a dishwasher according to an embodiment. [20] Fig. 5 is a flowchart illustrating a control method of a dishwasher according to a first embodiment. [21] Fig. 6 is a perspective view of a water softener of a dishwasher according to a second embodiment. [22] Fig. 7 is a flowchart illustrating a control method of a dishwasher according to a second embodiment. [23] Fig. 8 is a perspective view of a water softener of a dishwasher according to a third embodiment. [24] Fig. 9 is a block diagram of a control unit of a dishwasher according to another embodiment. [25] Fig. 10 is a flowchart of a control method of a dishwasher according to a third embodiment. [26]

Mode for the Invention [27] Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. [28] The following will describe a dishwasher according to a first embodiment.

[29] Fig. 1 is a perspective view of a dishwasher according to a first embodiment.

[30] Referring to Fig. 1, a dishwasher includes a case 10 defining an outer appearance and a tub 20 that is installed in the case 10 to define a washing chamber 21. [31] A control unit 150 is disposed above the case 10. The control unit 150 includes a display 155 displaying a current operation state, a sound generation unit 156, and an input unit 151. The control unit 150 will be described later. [32] Guide rails 40 are disposed on inner opposite walls of the washing chamber 21.

Upper and lower racks slide along the guide rails 40 to go in and out of the washing chamber 21.

[33] A door 50 is disposed on a front portion of the washing chamber 21 to be capable of being opened and closed. At this point, the door 50 is hingedly coupled to a lower portion of the case 10 to open and close the front portion of the washing chamber 21.

[34] An exhausting unit 51 having an exhausting fan (not shown) is installed on the door

50. The exhausting unit 51 removes humidity from the washing chamber 21 when the dishwasher is performing a drying operation.

[35] A spraying nozzle 60 is connected in the tub 20. The spraying nozzle 60 sprays the water toward the racks while rotating. The spraying nozzle 60 is connected to the sump 110.

[36] The sump 110 is disposed at a bottom of the tub 20. A filter 111 defining the bottom surface of the tub 20 is disposed above the sump 110. The sump 110 collects washing water and filters off food residues contained in the washing water.

[37] A water softener 120 is disposed on the bottom of the tub 20. The water softener 120 is exposed at the bottom of the tub 20 so that the user can refill a restoring material in the water softener 120.

[38] Fig. 2 is a perspective view of the sump, water supply unit, and water softener of

FIG. 1, and Fig. 3 is a water softener of a dishwasher according to a first embodiment.

[39] Referring to Figs. 2 and 3, a base 30 is disposed on the bottom of the tub 20. The sump 110 and the water softener 120 are disposed on the base 30.

[40] A washing pump 112 pumping the washing water toward the spraying nozzle 60 and a drain pump 113 for draining the washing water recovered to the sump 110 to an external side are connected to the sump 110. In Fig. 2, the sump is shown in a state where the filter is opened.

[41] The softener 120 is disposed at a side of the sump 110. The water softener 120 includes a water softening unit 121 for softening the washing water and a restoring unit that is formed at a side of the water softener and a restoring unit 125 formed at a side of the softening unit. Ion resin (not shown) for softening the washing water is contained in the softening unit 121 and a restoring material is contained in the storing unit 125. In the following description, the restoring material that is dissolved in the washing water in the restoring unit 125 will be referred to as a restoring solution.

[42] A water supply unit 130 is disposed at a side of the sump 110. The water supply unit

130 may be disposed between a sidewall of the tub 20 and a sidewall of the case 10.

[43] A drain passage 131 is formed on a portion of the water supply unit 130. A drain hose and the drain pump 113 are connected to the opposite ends of the drain passage 131. A natural drain preventing unit (not shown) for preventing the natural water drain is formed on the drain passage, thereby preventing the natural water drain other than the drain cycle.

[44] The water supply unit 130 is provided with a washing water inlet 132 through which the washing water is introduced from the external side. A flow meter 133 for detecting a water flow rate of the washing water introduced from the external side is disposed near the washing water inlet 132.

[45] The water supply unit 130 is provided with a chamber 134 communicating with the washing water inlet 132. The chamber 134 functions to temporarily store a part of the washing water introduced into the washing water inlet 132.

[46] A communication hole 135 communicating with the tub 20 is formed on an upper portion of the chamber 134. In addition, a water softening unit connector 136 connected to the water softening unit 121 is formed on a lower portion of the chamber 134. A restoring unit connector 137 connected to the restoring unit 125 is also formed on the lower portion of the chamber 134. At this point, an opening/closing valve (not shown) may be installed on each of the water softening unit connector 136 and the restoring unit connector 137.

[47] In addition, the water softening unit 121 is provided with a water softening unit inlet

122 to which the water softening unit connector 136 is connected. A water softening unit outlet 123 through which the softened washing water is discharged from the water softening unit 121 to the sump is formed on an upper portion of the water softening unit 122. The water softening unit 121 and the restoring unit 125 communicate with each other as the restoring valve 127 is opened.

[48] A hardness detecting unit 140 for detecting the hardness of the washing water may be disposed the water softening unit inlet side. For example, the hardness detecting unit 140 may be disposed on the chamber 134 or, although not shown in the drawings, on the water softening unit inlet 122. As the hardness detecting unit 140, a hardness sensor that measures the hardness of the washing water by detecting an amount of current of voltage that varied in accordance with an amount of metal ions contained in the washing water.

[49] The washing water introduced through the washing water inlet 132 is partly supplied to the tub 20 through the communication hole 135, partly supplied to the water softening unit 121 through the water softening unit connector 136, and partly supplied to the restoring unit 125 through the restoring unit connector 137. In addition, when the restoring valve 127 is opened, the restoring solution of the restoring unit 125 is directed to the water softening unit 121. The restoring solution removes the metal ions adsorbed in the ion resin, thereby restoring the ion resin.

[50] A cap 128 is installed on the upper portion of the restoring unit 125 such that the cap

128 is exposed to the upper portion of the tub 20. Therefore, the user opens the cap 128 and refills the restoring material such as salt in the restoring unit 125.

[51] Fig. 4 is a control unit of a dishwasher according to an embodiment.

[52] Referring to Fig. 4, the control unit 150 includes a controller 152 controlling the dishwasher. The input unit 152 is connected to the controller 152 so that the user can select a mode. Further, the hardness detecting unit 140 measuring the hardness of the washing water and a memory unit 153 storing data on an amount of restoring solution of the restoring unit 125, which corresponds to a hardness value detected are connected to the controller 152.

[53] The controller 152 opens and closes the restoring valve 127 in accordance with the hardness detected by the hardness detecting unit 140. For example, the controller 152 opens the restoring valve 127 when the hardness detected by the hardness detecting unit 140 is greater than a reference value.

[54] A driving unit 154 for driving the water supply valve, display 155, sound generating unit 156, and restoring valve 127 in accordance with a control signal from the controller 152 is connected to the controller 152.

[55] The hardness detecting unit 140 detects an amount of current or voltage by heavy metals or metal ions of the washing water and transmits a corresponding signal to the controller 152. The controller 152 reads an amount of the restoring solution, which corresponds to the hardness detected by the hardness detecting unit 140 and transmits a corresponding signal to the driving unit 154. At this point, the driving unit 154 controls a degree of the opening and opening duration of the restoring valve 127 in accordance with the control signal from the controller 152.

[56] The following will describe an operation of the above -described dishwasher.

[57] When the user inputs a washing mode through the input unit 151, the dishwasher selectively or sequentially performs a washing operation and a drying operation in accordance with a signal from the controller 152. Here, the washing operation includes at least one of a preliminary washing operation, a main washing operation, and a heating washing operation. In the following description, the preliminary, main, and heating washing operations will be referred to as washing operation.

[58] When the washing operation starts, the water supply valve is opened and thus the washing water is supplied to the chamber 134 through the washing water inlet 132 of the waster supply unit 130.

[59] The washing water supplied through the washing water inlet 132 is partly directed into the tub 20 through the communication hole 135 and stored in the sump 110. The washing water supplied through the washing water inlet 132 is partly directed to the water softening unit 121 through the water softening unit connector 136 and partly directed to the restoring unit 125 through the restoring unit connector 137.

[60] At this point, in the water softening unit 121, the metal ions contained in the washing water is adsorbed by the ion resin and thus the washing water is softened. The softened washing water is directed into the sump 110 through the water softening unit outlet 123. At this point, the ion resin increases in a volume as the metal ions are adsorbed therein.

[61] When it is determined by the flow meter 133 that a sufficient amount of washing water is supplied, the washing pump 112 is driven. The washing pump 112 pumps out the washing water introduced into the sump 110 toward the spraying nozzle 60. The spraying nozzle 60 sprays the washing water to the racks 41 and 42 while rotating, thereby washing the dishes. The washing water falls down to be recovered to the sump 110. At this point, the filter 111 of the sump 111 filters off the food residues. The washing water recovered to the sump 110 is pumped again to the spraying nozzle 60 by the washing pump 112.

[62] The washing operation is performed for a predetermined time, after which a drain cycle is performed. The washing operation and the drain cycle are repeated by predetermined times, after which a drying operation is performed.

[63] When the drying operation is performed, a heater (not shown) disposed in the tub 20 is driven. In addition, as the exhaust unit 51 of the door 50 is driven, the moisture is discharged to the external side. By performing the drying operation for a predetermined time set in the controller 152, the dishes are dried.

[64] The following will describe a control method of the dishwasher according to a first embodiment.

[65] Fig. 5 is a flowchart illustrating a control method of the dishwasher according to a first embodiment.

[66] Referring to Fig. 5, when the washing operation starts, the water supply valve is opened and thus the water supply unit 130 supplies the washing water (Sl 1). At this point, the hardness detecting unit 140 detects the hardness of the washing water and transmits corresponding information to the controller 152 (S 12). The controller 152 determines an amount of a supply amount of the restoring solution corresponding to the hardness detected by the hardness detecting unit 140.

[67] At this point, the controller 152 opens and closes the restoring valve 127 in accordance with the washing water hardness detected by the hardness detecting unit 140. For example, the controller 152 controls the restoring valve 127 such that the restoring valve 127 is more frequently opened as the washing water hardness detected by the hardness detecting unit 140 increases.

[68] As described above, since an amount of the metal ions adsorbed by the ion resin varies in accordance with the hardness of the washing water, the opening period of the restoring valve 127 can be adjusted in accordance with the amount of the metal ions adsorbed by the ion resin. Therefore, an amount of the restoring material such as the salt used for the restoring the ion resin can be reduced. In addition, by timely restoring the water softening unit 121, the stain formed on the tub 20 and the sump 110 by the metal ions can be minimized.

[69] Further, the control unit 152 may open the restoring valve 127 only in the drying operation. For example, the controller 152 determines if the drying operation is being performed (S 14). When it is determined that the drying operation is not being performed, the restoring valve 127 maintains its closed state. On the other hand, when it is determined that the drying operation is being performed, the restoring valve 127 is opened (S 15). At this point, by controlling the restoring valve such that it is opened by a predetermined degree for a predetermined opening duration, a predetermined amount of the restoring solution stored in the restoring unit 125 is directed to the water softening unit 121. At this point, the ion resin of the water softening unit 121 is stored by the restoring solution.

[70] The controller 152 determined if it reaches a point of the restoring completion time

(S 16). When it is determined that it reaches the point of the restoring completion time, the restoring valve 127 is closed (S 17).

[71] The following will describe a water softener according to a second embodiment.

[72] Fig. 6 is a perspective view of a water softener according to a second embodiment.

[73] A water softener 120 of the second embodiment is substantially identical to that of the first embodiment except for a location of the hardness detecting unit. Therefore, in the first and second embodiments, like reference numbers refer to like parts. A description of the like parts will be omitted in this second embodiment.

[74] Referring to Fig. 6, the water softener 120 includes a hardness detecting unit disposed an outlet side of the water softening unit 121. The hardness detecting unit 240 disposed the outlet side of the water softening unit 121 is connected to the controller 152. Therefore, the hardness detecting unit 140 detects the hardness of the washing water discharged through the outlet of the water softening unit 121 and transmits the corresponding information to the controller 152.

[75] In addition, the control unit 152 opens and closes the restoring valve 127 in accordance with the hardness detected by the hardness detecting unit 240. For example, when the hardness detected by the hardness detecting unit 240 is greater than a reference value, the control unit 152 may open the restoring valve 127. That is, since the hardness of the washing water discharged from the water softening unit 121 is reduced as the metal ion adsorption capability of the water softening unit 121 becomes higher, there is not need to restore the ion resin of the water softening unit 121 when the hardness of the washing water discharged from the water softening unit 121 is less than the reference value.

[76] The following will describe a control method of the dishwasher according to a second embodiment.

[77] Fig. 7 is a flowchart illustrating a control method of the dishwasher according to a second embodiment.

[78] Referring to Fig. 7, when the washing operation starts, the water supply valve is opened and thus the water supply unit 130 supplies the washing water (S21). The washing water from the water supply unit 130 is partly supplied to the tub 20 through the communication hole 135 and partly supplied to the water softening unit 121 through the water softening connector 136. The washing water from the water supply unit 130 may be partly supplied to the restoring unit 125 through the restoring unit connector 121 when needed.

[79] The washing water supplied to the water softening unit 121 is softened by the ion resin and introduced into the sump 110 through the outlet of the water softening unit 121. The hardness detecting unit 140 detects the hardness of the softened washing water and transmits the corresponding information to the controller 152 (S22). The controller 152 determines an amount of restoring solution that will be supplied in accordance with the information from the hardness detecting unit 140.

[80] At this point, the controller 152 opens and closes the restoring valve 127 in accordance with the washing water hardness detected by the hardness detecting unit 140. For example, the controller 152 controls the restoring valve 127 such that the restoring valve 127 is more frequently opened as the washing water hardness detected by the hardness detecting unit 140 increases. Here, if the washing water discharged from the softening unit 121 is well softened by the ion resin, the hardness of the washing water will be reduced, and otherwise, the hardness will be high.

[81] As described above, since it can be determined that the adsorption capability of the ion resin of the water softening unit 121 is deteriorated as the hardness of the washing water discharged from the water softening unit 121 increases, the opening period of the restoring valve 127 can be further shortened as the hardness of the washing water discharged from the water softening unit 121 increases. Therefore, by timely restoring the water softening unit 121, the stain formed on the tub 20 and the sump 110 by the metal ions can be minimized.

[82] Further, the control unit 152 may open the restoring valve 127 only in the drying operation. For example, when it is determined by the controller 152 that the hardness of the washing water discharged from the water softening unit 121 is greater than the reference value (S23), it is determined if the drying operation is being performed. When it is determined by the controller 152 that the drying operation is not being performed, the restoring valve 127 maintains its closed state. On the other hand, when it is determined that the drying operation is being performed, the restoring valve 127 is opened so that the restoring solution contained in the restoring unit 125 can be directed to the water softening unit 121 (S25). At this point, At this point, the ion resin of the water softening unit 121 is stored by the restoring solution.

[83] Further, it is determined if the drying operation is completed (S26). When it is determined that the drying operation is completed, the restoring valve 127 is closed (S27). Needless to say, it is also possible to control the restoring valve 127 such that the restoring valve 127 is closed after the restoring valve 127 is opened for a predetermined time.

[84] The following will describe a water softener according to a third embodiment.

[85] Fig. 8 is a perspective view of a water softener according to a third embodiment.

[86] A water softener 120 of the third embodiment is substantially identical to that of the first embodiment except for a location and the number of the hardness detecting units. Therefore, in the first and second embodiments, like reference numbers refer to like parts. A description of the like parts will be omitted in this second embodiment.

[87] Referring to Fig. 8, the water softener 120 includes a first hardness detecting unit 341 disposed the outlet side of the water softening unit 121 and a second hardness detecting unit 342 disposed an inlet side of the water softening unit 121.

[88] Fig. 9 is a control unit of a dishwasher according to another embodiment.

[89] Referring to Fig. 9, the first and second hardness detecting units 31 and 342 are connected to the controller. Therefore, the first hardness detecting unit 341 detects hardness of the washing water discharged from the water softening unit 121 and the second hardness detecting unit 342 detects hardness of the washing water introduced into the water softening unit 121. The information on the hardness detected by the first and second hardness detecting units 341 and 342 are transmitted to the control unit 152.

[90] The control unit 152 opens and closes the restring valve 127 in accordance with a difference between the hardness detected by the first hardness detecting unit 341 and the hardness detected by the second hardness detecting unit 342. For example, when the difference is less than a reference value, the controller 152 opens the restoring valve 127. That is, since it can be regarded that the washing water is not sufficiently softened in the water softening unit 121 when the difference is less than the reference value, the restoring valve 127 is opened to restore the ion resin of the water softening unit 121.

[91] The following will describe a control method of the dishwasher according to a second embodiment.

[92] Fig. 10 is a flowchart illustrating a control method of the dishwasher according to a third embodiment.

[93] Referring to Fig. 10, when the washing operation starts, the water supply valve is opened and thus the water supply unit 130 supplies the washing water (S31). The washing water from the water supply unit 130 is partly supplied to the tub 20 through the communication hole 135 and partly supplied to the water softening unit 121 through the water softening connector 136.

[94] In addition, the washing water from the water supply unit 130 may be partly supplied to the restoring unit 125 through the restoring unit connector 121 when needed.

[95] At this point, the second hardness detecting unit 241 detects hardness of the washing water introduced into the water softening unit 121 through the inlet of the water softening unit 121 (S32). The second hardness detecting unit 342 transmits the information on the detected hardness to the controller 152.

[96] The washing water of the water softening unit 121 is softened by the ion resin and directed to the sump 110 through the outlet of the water softening unit 121. At this point, the first hardness detecting unit 341 detects the hardness of the softened washing water discharged from the water softening unit 121 and transmits the corresponding information to the controller 152 (S32).

[97] When the water is supplied for a predetermined time or up to a predetermined water level, the water supply valve is closed (S33). [98] The controller 152 compares the difference between the hardness detected by the first hardness detecting unit 341 and the hardness detected by the second hardness detecting unit 342 with the reference value (S34). When the difference is smaller than the reference value, it is determined that there is no need to supply the restoring solution to the water softening unit 121 as a small amount of the metal ions is adsorbed in the ion resin.

[99] When the difference is greater than the reference value, it is determined that an amount of the restoring solution in the restoring unit 125 is insufficient. At this point, the controller 152 outputs a message letting the user know that there is a need to refill the restoring solution through the display 155 and/or the sound generation unit (S35).

[100] The controller 152 opens and closes the restoring valve 127 in accordance with the hardness difference detected by the first and second hardness detecting units 341 and 342. For example, the controller 152 controls the restoring valve 127 such that the restoring valve 127 is more frequently opened as the hardness difference between the inflow washing water and the outflow washing water increases.

[101] As described above, as the hardness difference between the inflow washing water and the outflow washing water increases, it can be regarded that the ion adsorption capability of the ion resin. Therefore, the opening period of the restoring valve 127 may be prolonged. Therefore, by timely restoring the water softening unit 121, the stain formed on the tub 20 and the sump 110 by the metal ions can be minimized.

[102] Further, the control unit 152 may open the restoring valve 127 only in the drying operation. For example, when it is determined by the controller 152 that the hardness difference is greater than the reference value, the controller 152 determines if the drying operation is being performed (S36). When it is determined that the restoring valve 127 is opened to direct the restoring solution of the restoring unit 125 to the water softening unit 121 (S37). When it is determined that the restoring of the ion resin of the water softening unit 121 is completed (S38), the restoring valve 127 is closed (S39).

[103] Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifi cations and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. Industrial Applicability

[104] With the dishwasher and the control method according to the implementation of the present invention, it has an effect that a water softener can be restored at a proper period and maintain a proper concentration of the restoring solution can be maintained in a dishwasher and industrial applicability is very high.

[105]

Claims

[ 1 ] A dishwasher comprising : a water softening unit storing ion resin; a restoring unit storing restoring solution for restoring the ion resin of the water softening unit; a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit; a hardness detecting unit detecting hardness of the washing water supplied; and a controller opening and closing the restoring valve in accordance with the hardness detected by the hardness detecting unit.

[2] The dishwasher according to claim 1, wherein the hardness detecting unit is disposed of an inlet side of the water softening unit.

[3] The dishwasher according to claim 1, wherein the controller opens the restoring valve in a drying operation.

[4] A dishwasher comprising: a water softening unit storing ion resin; a restoring unit storing restoring solution for restoring the ion resin of the water softening unit; a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit; a hardness detecting unit that is disposed at a softened water outlet side of the water softening unit to detect hardness of the washing water supplied; and a controller opening and closing the restoring valve in accordance with the hardness detected by the hardness detecting unit.

[5] The dishwasher according to claim 4, wherein the controller opens the restoring valve when the hardness detected by the hardness detecting unit is greater than a predetermined value.

[6] The dishwasher according to claim 4, wherein the restoring valve is opened in the drying operation.

[7] The dishwasher according to claim 4, further comprising a sound generation unit that lets a user know that an amount of the restoring solution is insufficient in the water softening unit when the hardness detected by the hardness detecting unit is greater than the reference value.

[8] The dishwasher according to claim 4, wherein the controller varies an amount of the restoring solution supplied to the water softening unit in accordance with a difference between the detected hardness detected and the reference value.

[9] A dishwasher comprising: a water softening unit storing ion resin; a restoring unit storing restoring solution for restoring the ion resin of the water softening unit; a restoring valve selectively directing the restoring solution of the restoring unit to the water softening unit to restore the ion resin of the water softening unit; first and second hardness detecting units that are respectively installed an outlet side and an inlet side of the water softening unit to detect hardness of the washing water supplied and discharged; and a controller opening and closing the restoring valve in accordance with a hardness difference between the hardness detected by the first hardness detecting unit and the hardness detected by the second hardness detecting unit.

[10] The dishwasher according to claim 9, wherein the controller opens the restoring valve when the hardness difference is less than a reference value.

[11] The dishwasher according to claim 9, wherein the restoring valve is opened in the drying operation.

[12] The dishwasher according to claim 9, wherein farther comprising a sound generation unit that lets a user know that an amount of the restoring solution is insufficient in the water softening unit when the hardness difference is less than a reference value.

[13] The dishwasher according to claim 9, wherein an amount of the restoring solution supplied to the water softening unit is determined in accordance with the hardness difference.

[14] The dishwasher according to claim 9, wherein farther comprising a water supply unit supplying the washing water to the restoring unit, wherein the second hardness detecting unit is disposed on the water supply unit.

[15] A method of controlling a dishwasher, comprising: detecting hardness of washing water discharged from a water softening unit; and controlling timing for supplying restoring solution to the water softening unit when the detected hardness is greater than a predetermined valve.

[16] The method according to claim 15, wherein the controlling the timing includes supplying the restoring solution of the restoring unit to the water softening unit when the detected hardness is greater than the reference value. [17] The method according to claim 15, further comprising letting a user know that an amount of the restoring solution is insufficient in the water softening unit when the detected hardness is greater than the reference value. [18] The method according to claim 15, wherein the restoring solution of the restoring unit is supplied to the water softening unit in a drying operation. [19] A method of controlling a dishwasher, comprising: detecting hardness of washing water at an inlet side and an outlet side of a water softening unit; and controlling timing for supplying restoring solution to the water softening unit when a hardness difference at the inlet side and the outlet side of the waster softening unit. [20] The method according to claim 19, wherein the controlling the timing includes supplying the restoring solution of the restoring unit to the water softening unit when the hardness difference is less than a predetermined valve. [21] The method according to claim 19, further comprising letting a user know that an amount of the restoring solution is insufficient in the water softening unit when the hardness difference is greater than the reference value, [22] The method according to claim 19, wherein the restoring solution of the restoring unit is supplied to the water softening unit in a drying operation.