Patent Publication Number: US-7905121-B2

Title: Washing machine with ion eluting and imbalance correcting units

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a washing machine that supplies metal ion added water from ion eluting means to a laundry tub (a drum or a washing tub) and performs an antibacterial treatment on the laundry being put in the laundry tub, and more particularly, to a washing machine that corrects imbalance in the laundry tub at the time of rotation for spin-drying. 
     2. Description of the Related Art 
     When laundry is washed in a washing machine, a treatment substance is frequently added to water (in particular, rinsing water). Typical examples of such a treatment substance are a fabric softener and starch. In addition to these, the demand for a finishing treatment to render laundry antibacterial has been increasing in recent years. 
     From the hygienic point of view, it is desirable that laundry be dried in the sun. However, in recent years, with the increase in the number of working women and with the increase in the number of nuclear families, there have been an increasing number of households where no one is at home during the daytime. In these households, there is no choice but to dry laundry indoors. Even in households where someone is at home during the daytime, laundry is dried indoors when it is raining. 
     When laundry is dried indoors, compared to when laundry is dried in the sun, bacteria and mold readily propagate in the laundry. This tendency is marked when laundry drying takes time such as when humidity is high like in a rainy season or when temperature is low. Depending on the propagation condition, there are cases where laundry becomes smelly. 
     Moreover, recently, with growing awareness of thriftiness, more and more households reuse water that is left in the bath tub after bathing, for laundry washing. However, bacteria have increased in water left in the bath tub overnight, and the bacteria adhere to laundry and further propagates to make the laundry smelly. 
     For this reason, there is a strong demand that an antibacterial treatment be performed on clothes to suppress the propagation of bacteria and mold, from households having no other choice but to dry laundry indoors every day and households reusing water left in the bath tub for laundry washing. 
     On the other hand, many clothes having undergone an antibacterial and deodorizing treatment or a microbial control treatment have recently been available. However, it is difficult that the textile goods in a household are all ones having undergone an antibacterial and deodorizing treatment. Moreover, the efficacy of the antibacterial and deodorizing treatment decreases as textile goods are washed repeatedly. 
     Under these circumstances, an idea was conceived of performing an antibacterial treatment on laundry every time it is washed. For example, Patent Document 1 discloses an electric washing machine provided with an ion generator that generates metal ions having sterilizing power such as silver ions or copper ions. Patent Document 2 discloses a washing machine provided with a silver ion adding unit that adds silver ions to cleaning water. In particular, in the washing machine of Patent Document 2, silver ions are added to water in a concentration of 3 to 50 ppb (part per billion) to render the laundry antibacterial. 
     Patent Document 1 is Japanese Unexamined Utility Model Application Publication “Utility Model Laid-Open No. H5-74487 (laid-open on Oct. 12, 1993).” Moreover, Patent Document 2 is Japanese Unexamined Patent Application Publication “Patent Application Laid-Open No. 2001-276484 (laid-open on Oct. 9, 2001).” 
     The washing machines of Patent Documents 1 and 2 are both so-called vertical washing machines (vertical washing) where the washing tub is disposed so that the rotation axis thereof is in the vertical direction. However, in recent years, so-called slanted washing machines (drum washing) where the drum is disposed so that the rotation axis thereof is at an angle with respect to the vertical direction have also been developed. 
     In vertical washing machines, since the rotation axis of the washing tub is in the vertical direction, the gravity acting on the laundry is in a direction parallel to the rotation axis. In this case, leaning does not readily occur in the washing tub, and the center of gravity of the laundry is apt to be on the rotation axis. Consequently, imbalance does not readily occur, either. Here, imbalance refers to a phenomenon in which when the laundry being put in the washing tub is not evenly spread in the washing tub, the washing tub cannot keep its balance at the time of start of rotation for spin-drying and the washing tub and the washing machine body largely shake in the subsequent spin-drying operation. Moreover, in vertical washing machines, the center of gravity of the washing tub is on the rotation axis that is in the vertical direction, and the rotation axis is situated immediately above the motor. For this reason, the load of the washing tub can be sustained by the motor portion. 
     On the other hand, in slanted washing machines, since the rotation axis is not in the vertical direction, the gravity acting on the laundry is not in the direction of the rotation axis. That is, when the drum is stopped, the laundry gathers in a lower part of the drum, and under that condition, the center of gravity of the laundry is not on the rotation axis. When the drum is rotated and the centrifugal force acts on the laundry, the laundry is pressed in the circumferential direction of the drum, and when the laundry is not uniformly pressed, imbalance occurs. Consequently, in slanted washing machines where the rotation axis is not in the vertical direction, the frequency of occurrence of imbalance is extremely high because of its structure. 
     Therefore, it is necessary to correct such imbalance, and a common method of correcting this is to pour water into the drum and agitate it to thereby slightly change the disposition of the laundry. However, only pouring water into the drum cannot make it possible to maintain the efficacy of the antibacterial treatment that is performed with time and trouble being taken, because the metal attached to the laundry in the upstream operation of the spin-drying operation is lost. This problem also arises when imbalance occurs in vertical washing machines. 
     SUMMARY OF INVENTION 
     The present invention is made to solve the above-mentioned problem, and an object thereof is to provide a washing machine capable of correcting imbalance in the laundry tub at the time of rotation for spin-drying without any loss of the antibacterial effect by the metal ion added to the laundry. 
     To achieve the above-mentioned object, according to a washing machine of the present invention, when sensing means senses imbalance in the laundry tub at the time of spin-drying rotation of the laundry tub performed after metal ion added water supplied from ion eluting means to the laundry tub is supplied, imbalance correcting means corrects the imbalance by performing a processing different from a processing performed when imbalance is sensed in a case where the metal ion added water is not supplied. 
     Examples of the imbalance correction in a case where the metal ion added water is not supplied include a processing of supplying water (for example, tap water) to the laundry tub and agitating the laundry. Therefore, as the processing different from this, balance correction rinsing in which the metal ion added water obtained by the ion eluting means is supplied to the laundry tub and agitation is performed can be considered. 
     As described above, when the sensing means senses imbalance in the laundry tub at the time of spin-drying rotation of the laundry tub performed after the metal ion added water is supplied, by performing the processing different from the processing of supplying normal tap water, that is, the supply of the metal ion added water, even if metal ions added to the laundry in the antibacterial treatment by the supply of the metal ion added water are washed away, the metal ions having been washed away can be surely made up for by the supply of the metal ion added water performed later. Consequently, imbalance correction can be performed without any loss of the antibacterial effect added to the laundry in the preceding antibacterial treatment. That is, imbalance correction can be performed while the efficacy of the antibacterial treatment on the laundry is ensured. 
     Moreover, the imbalance correcting means may perform control so that the amount of supply of the metal ion added water to the laundry tub in the balance correction rinsing is smaller than the amount of supply of the metal ion added water in a preceding operation. Since metal ions of an amount necessary for delivering the antibacterial effect on the laundry have already been supplied in the preceding metal ion added water supplying operation (for example, the rinsing operation), it is unnecessary to re-supply metal ions of the amount necessary for delivering the antibacterial effect even if the amount washed away in the succeeding balance correction rinsing is considered. With this, it can be prevented that metal ions are washed away without being used for the antibacterial treatment on the laundry in the balance correction rinsing and useless metal ions appear. 
     Moreover, similar effects as those mentioned above can be obtained when the imbalance correcting means performs control so that the metal ion concentration of the metal ion added water to the laundry tub in the balance correction rinsing is lower than the metal ion concentration of the metal ion added water in a preceding operation. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing the external structure of a slanted drum washing machine according to an embodiment of the present invention; 
         FIG. 2  is a vertical cross-sectional view showing the schematic structure of the washing machine; 
         FIG. 3  is an explanatory view schematically showing the structure of a water supply mouth provided in the washing machine; 
         FIG. 4  is a flowchart showing the entire flow of the laundry washing process of the washing machine; 
         FIG. 5  is a flowchart showing the details of a washing operation in the laundry washing process; 
         FIG. 6  is a flowchart showing the details of a rinsing operation in the laundry washing process; 
         FIG. 7  is a flowchart showing the details of a spin-drying operation in the laundry washing process; 
         FIG. 8  is a horizontal cross-sectional view showing the schematic structure of an ion elution unit provided in the washing machine; 
         FIG. 9  is a vertical cross-sectional view showing the schematic structure of the ion elution unit; 
         FIG. 10  is an explanatory view showing the schematic structure of a driving circuit for driving the ion elution unit; 
         FIG. 11  is a flowchart showing the sequence of the elution of the metal ions from the ion elution unit, and the addition of metal ion added water; 
         FIG. 12  is a timing chart showing the timing of opening and closing of a main water supply valve and a sub water supply valve and the timing of voltage application to electrodes of the ion elution unit in the washing machine; 
         FIG. 13  is a block diagram showing the structure for correcting imbalance in the drum at the time of spin-drying in the washing machine; and 
         FIG. 14  is a graph showing a relationship between the silver ion concentration and the bacteriostasis activation value in the metal ion added water. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Describing an embodiment of the present invention with reference to  FIGS. 1 to 14  is as follows: 
     (1. Structure of the Washing Machine) 
       FIG. 1  is an external perspective view of a slanted drum washing machine  601  according to the present embodiment. FIG.  2  is a vertical cross-sectional view of the slanted drum (slanted) washing machine  601 . The slanted drum washing machine  601  has a box-shaped body  610 . Inside the body  601 , a water tub  620  and a drum  630  in which laundry is put are disposed. The water tub  620  and the drum  630  are both cylindrical, and have laundry putting-in openings  621  and  631  on one end surfaces, respectively. 
     A shaft  632  protrudes outward from the center of the bottom of the drum  630 . By the shaft  632  being held by a bearing  622  provided in the center of the bottom of the water tub  620 , the drum  630  and the water tub  620  are concentrically disposed with the drum  630  inside and the water tub  620  outside. 
     The water tub  620  and the drum  630  are held inside the body  610  by a non-illustrated suspension mechanism so that the axis thereof is substantially horizontal. In the present embodiment, as shown in  FIG. 2 , the axis of the water tub  620  and the drum  630  is inclined at an angle θ (for example, 15°) to horizontal, and the side of the laundry putting-in openings  621  and  631  are slightly lifted up. That is, the water tub  620  and the drum  630  are disposed so that the rotation axis is at an angle with respect to the vertical direction. This is done in order to make it easy to see the inside of the drum  630  and make it easy to put in and out laundry. 
     In the slanted drum washing machine  601 , while the inclination angle θ is assumed to be in a range of 0° to 30°, it is not limited to this range as long as the rotation axis is at an angle with respect to the vertical direction. 
     On the front side external wall of the body  610 , an opening  611  is provided so as to be opposed to the laundry putting-in openings  621  and  631 , and in front of the opening  611 , a horizontally opening door  612  is provided. The opening  611  and the laundry putting-in opening  621  are coupled together by a door packing  613  made of soft synthetic resin or rubber. The door packing  613  is provided for preventing the inside of the body  610  from being wetted by water splashes caused in the drum  630 , water drops caused when wet laundry is put in or out, and spilled water from the laundry putting-in opening  621 . 
     A ring-shaped lip  614  is integrally formed on the inner surface of the door packing  613 . The lip  614  is in intimate contact with the periphery of a protrusion  615  provided on the inner surface of the door  612  to thereby prevent water from leaking through a gap between the door packing  613  and the door  612 . The protrusion  615  plays a role of preventing the laundry in the drum  630  from being forced out of the laundry putting-in opening  621 . The protrusion  615  may be made of a transparent material so that the inside of the drum  630  is visible. 
     A multiplicity of dewatering holes  633  are formed on the circumferential wall of the drum  630 , and water moves between the drum  630  and the water tub  620  through the dewatering holes  633 . A plurality of baffles  634  are disposed at predetermined intervals on the inner surface of the drum  630 . The baffles  634  pick up the laundry and drop it from above as the drum  630  rotates. 
     A balance weight (balancer)  635  is attached to the external surface of the drum  630  and the laundry putting-in opening  631 .  FIG. 2  shows only a ring-shaped balance weight  635  attached to the laundry putting-in opening  631  and does not show the balance weight attached to the external surface of the drum  630 . The balance weight  635  suppresses shakes caused when the drum  630  rotates at high speed. 
     A motor  640  is attached to the external surface of the bottom of the water tub  620 . The motor  640  is of a direct drive type, and to the rotor thereof, the shaft  632  of the drum  630  is coupled so as to be fixed. The shaft  622  is attached to the housing of the motor  640 , and constitutes a part of the motor  640 . 
     An electromagnetically opening and closing water supply valve  50  is disposed in a space above the water tub  620 . The water supply valve  50  has a connection pipe  51  protruding rearward through the body  610 . To the connection pipe  51 , a water supply hose (not shown) supplying clean water such as tap water is connected. A water supply pipe  52  extends from the water supply valve  50 . An end of the water supply pipe  52  is connected to a container-shaped water supply mouth  53 . The water supply mouth  53  has a structure shown in  FIG. 3 . 
       FIG. 3  is an explanatory view schematically showing the structure of the water supply mouth  53  viewed from the front side. The water supply mouth  53  is open at its top, and the inside thereof is divided into the left and right sections. The left section is a detergent chamber  54  serving as a preparation space for storing a detergent. The right section is a finishing agent chamber  55  serving as a preparation space for storing a finishing agent for laundry washing. A water outlet  56  for pouring water to a catchment measure  653  of a water supply nozzle  652  connected to an upper part of the door packing  613  is provided at the bottom of the detergent chamber  54 . A siphon  57  also for pouring water to the catchment measure  653  is provided in the finishing agent chamber  55 . 
     The siphon  57  comprises an inner pipe  57   a  that extends vertically upward from the bottom surface of the finishing agent chamber  55  and a cap-shaped outer pipe  57   b  with which the inner pipe  57   a  is capped. A gap allowing water to pass therethrough is formed between the inner pipe  57   a  and the outer pipe  57   b . The bottom of the inner pipe  57   a  is open to the inside of the catchment measure  653 . A predetermined gap is kept between the bottom end of the outer pipe  57   b  and the bottom surface of the finishing agent chamber  55 , and this gap serves as a water inlet. When water is poured into the finishing agent chamber  55  up to a level higher than the top end of the inner pipe  57   a , siphonage occurs to cause the water to flow through the siphon  57  out of the finishing agent chamber  55  and drop into the catchment measure  653 . 
     The water supply valve  50  comprises a main water supply valve  50   a  and a sub water supply valve  50   b . The connection pipe  51  is common to the main water supply valve  50   a  and the sub water supply valve  50   b . The water supply pipe  52  comprises a main water supply pipe  52   a  connected to the main water supply valve  50   a  and a sub water supply pipe  52   b  connected to the sub water supply valve  50   a.    
     The main water supply pipe  52   a  is connected to the detergent chamber  54 , and the sub water supply pipe  52   b  is connected to the finishing agent chamber  55 . That is, a path from the main water supply pipe  52   a  through the detergent chamber  54  into the catchment measure  653  and a path from the sub water supply pipe  52   b  through the finishing agent chamber  55  into the catchment measure  653  are formed, and further, these are different paths. 
     The top of the detergent chamber  54  and the top of the finishing agent chamber  55  are both open toward the outside of the body  610 . For each of these openings, a non-illustrated lid is provided. The user lifts the lid as required, and puts a detergent into the detergent chamber  54 , and a finishing agent into the finishing agent chamber  55 . 
     Returning to  FIG. 2 , description will be continued. A drain outlet  623  is provided in the lowest position of the water tub  620 , and an end of a drain pipe  660  is connected thereto. The other end of the drain pipe  660  is connected to a filter casing  661 . A lint filter  662  is inserted in the filter casing  661 . The lint filter  662 , which is made of a net of synthetic resin or cloth, collects lint in the washing water. An end of the filter casing  661  is closed by a detachably attachable cap  663  so that the lint filter  662  can be cleaned or replaced by detaching the cap  663 . 
     A drain pipe  664  is connected to the other end of the filter casing  661 . The drained water having passed through the filter  662  is drained out of the body  610  through the drain pipe  664 . A drain valve  665  is provided in the middle of the drain pipe  664 . 
     An air trap  671  is connected to the filter casing  661 . A water level sensor  673  is provided at the upper end of a connecting pipe  672  extending from the air trap  671 . The water level sensor  673  moves a magnetic substance within a coil in accordance with a pressure change in the air trap  671 , detects the resultant inductance change of the coil as an oscillation frequency change, and reads the water level from the oscillation frequency change. The water level that is read here is the water level in the drum  630 . 
     An operation panel  616  is provided on the top of the front surface of the body  610 . As shown in  FIG. 1 , a display  682  having a liquid crystal panel, a buzzer and the like and an operation switch section  684  including operation buttons of various switches are disposed on the operation portion  616 . 
     Reference numeral  690  shown in  FIG. 2  represents a controller with a microcomputer as a main component. The controller  690 , which includes a necessary storage such as a hard disk, also serves as storing means. The controller  690 , which is disposed close to the operation panel  616  in the body  610 , receives an operation instruction from the user through the operation switch section  684 , and provides an operation instruction to the motor  640 , the water supply valve  50  and the drain valve  665 . Moreover, the controller  690  provides a display instruction to the display  682 . The controller  690  includes a driving circuit  120  (see  FIG. 10 ) for driving an ion elution unit  100  described later. 
     The above-mentioned operation panel  616  is an input portion for the user to set a desired laundry washing mode. The controller  690  selects an individual operation in accordance with the laundry washing mode being set by the operation panel  616 , and executes the selected operation. Examples of the individual operation include a washing operation, a rinsing operation, a spin-drying operation and a drying operation. Thus, the laundry washing process executed by the controller  690  comprises at least one of the washing operation, the rinsing operation, the spin-drying operation and the drying operation, or a combination thereof in accordance with the laundry washing mode. 
     (2. Operation of the Washing Machine) 
     Next, the operation of the slanted drum washing machine  601  having the above-described structure will be described. 
     First, the user opens the door  612 , puts laundry into the drum  630 , and puts a detergent into the detergent chamber  54  of the water supply mouth  53 . When necessary, the user puts a finishing agent into the finishing agent chamber  55 . The finishing agent may be put in the middle of the laundry washing process. 
     After the detergent addition preparation is made, the user closes the door  612 , and operates the operation buttons of the operation switch section  684  of the operation panel  616  to select the laundry washing condition (laundry washing mode) Lastly, when the user pushes the start button, the laundry washing process corresponding to the laundry washing mode is performed in accordance with the flowcharts of  FIGS. 4 to 7 . 
       FIG. 4  is a flowchart of the entire laundry washing process. At step S 201 , it is determined whether a timer-started operation to start laundry washing at a set time is selected or not. If a timer-started operation is selected, the process proceeds to step S 206 . When it is not selected, the process proceeds to step S 202 . 
     When the process proceeds to step S 206 , whether the operation start time has come or not is determined. When the operation start time has come, the process proceeds to step S 202 . 
     At step S 202 , whether the washing operation is selected or not is determined. When it is selected, the process proceeds to step S 300 . The contents of the washing operation of step S 300  will be described later with reference to the flowchart of  FIG. 5 . After the washing operation is finished, the process proceeds to step S 203 . When the washing operation is not selected at step S 202 , the process proceeds directly to step S 203 . 
     At step S 203 , whether the rinsing operation is selected or not is determined. When it is selected, the process proceeds to S 400 . The contents of the rinsing operation of step S 400  will be described later with reference to the flowchart of  FIG. 6 . After the rinsing operation is finished, the process proceeds to step S 204 . When the rinsing operation is not selected at step S 204 , the process proceeds directly to step S 204 . 
     The rinsing operation may be performed a plurality of times. In  FIG. 4 , the rinsing operation is performed three times, and the step numbers of the times of the operation are denoted by branch numbers “S 400 - 1 ,” “S 400 - 2  ” and “S 400 - 3 ,” respectively. The number of times of the rinsing operation can be arbitrarily set by the user. When the metal ions and the finishing agent are added in different rinsing operations, the rinsing operation is necessarily performed at least twice. The metal ions and a different finishing agent may be simultaneously added in the same rinsing operation. In this case, the necessary number of times of the rinsing operation is at least one. 
     At step S 204 , whether the spin-drying operation is selected or not is determined. When it is selected, the process proceeds to S 500 . The contents of the spin-drying operation of step S 500  will be described later with reference to the flowchart of  FIG. 7 . After the spin-drying operation is finished, the process proceeds to step S 205 . When the spin-drying operation is not selected at step  204 , the process proceeds directly to step S 205 . 
     At step S 205 , terminating processing by the controller  690 , in particular, an arithmetic unit (microcomputer) included therein is automatically executed according to the procedure. In addition, the controller  690  notifies the user of the completion of the laundry washing process with an end-of-operation beep. After all the processing is finished, the slanted drum washing machine  601  returns to stand-by state in preparation for the next laundry washing process. 
     When the drying operation is selected, the drying operation is performed after step S 204 . In the drying operation, the laundry is dried, for example, by supplying hot air into the drum  630 . The hot and humid air discharged from the drum  630  is cooled by cooling water, and the moisture in the air is converted into water. That is, the drying operation adopts a water-cooling dehumidification method. The water cooled by the cooling water is drained out of the machine through the drain pipe  664 . 
     (3. Details of the Laundry Washing Operations) 
     Next, of the above-mentioned laundry washing operations, details of the individual operations of washing, rinsing and spin-drying will be described with reference to  FIGS. 5 to 7 . 
     (3-1. Washing Operation) 
     First, the washing operation will be described. 
       FIG. 5  is a flowchart of the washing operation. At step S 301 , the data on the water level in the drum  30  sensed by the water level sensor  673  is captured. At step S 302 , whether laundry amount sensing is selected or not is determined. When the selection of the laundry amount sensing is selected, the process proceeds to step S 308 . At step S 308 , the laundry amount sensing to measure the amount of laundry based on the rotation load of the drum  630  is performed. After the laundry amount sensing, the process proceeds to step S 303 . When the laundry amount sensing is not selected at step S 302 , the process proceeds directly to S 303 . 
     At step S 303 , the main water supply valve  50   a  is opened, and water is poured into the drum  630  through the main water supply pipe  52   a  and the water supply mouth  53  (precisely, water is poured into the water tub  620 , and the water enters the drum  630  through the dewatering holes  633 ). The detergent being put in the detergent chamber  54  of the water supply mouth  53  mixes with the water and enters the washing tub  30  together with the water. At this time, the drain valve  665  is closed. When the water level sensor  673  detects the set water level, the main water supply valve  50   a  is closed. Then, the process proceeds to step S 304 . 
     At step S 304 , preparatory tumbling is performed. In the preparatory tumbling, the drum  630  is rotated at low speed to cause the laundry to be raised out of the water and dropped into the water again so that the laundry absorbs an ample amount of water. Moreover, the air trapped in parts of the laundry is allowed to escape. 
     After the preparatory tumbling, the process shifts to step S 306 . At step S 306 , the drum  630  is rotated in a pattern of washing tumbling to raise the laundry high and then, drop it. The shock caused when the laundry is dropped causes a jet stream of water between the fibers of the laundry, whereby the laundry is washed. 
     After the elapse of the washing tumbling period, the process proceeds to step S 307 . At step S 307 , the drum  630  is rotated gently. When the drum  630  is rotated gently, before raised to a high position, the laundry separates from the drum  630  at a low position to drop. 
     When dropped from a high position, the laundry strikes hard against the inner wall of the drum  630 , and sticks to the inner wall. Consequently, imbalance is not readily corrected when the drum  630  starts high-speed spin-drying rotation. 
     On the other hand, when separated from the inner wall of the drum  630  at a low position, the laundry rather rolls than strikes hard, so that the laundry piles up comparatively softly. In this state, the laundry easily scatters in every direction when the drum  630  starts high-speed spin-drying rotation. That is, balance is easily achieved. For this reason, the drum  630  is gently rotated to disentangle the laundry in preparation for spin-drying rotation. 
     (3-2. Rinsing Operation) 
     Next, the contents of the rinsing operation will be described with reference to the flowchart of  FIG. 6 . 
     While the spin-drying operation of step S 500  (referred to as intermediate spin-drying operation here because it is a spin-drying operation performed in the rinsing operation) is executed first, this will be described with reference to the flowchart of  FIG. 7 . After the intermediate spin-drying at step S 500 , the process proceeds to step S 401 . At step S 401 , the main water supply valve  50   a  is opened, and water is supplied up to the set water level. 
     After the water supply, the process proceeds to step S 402 . At step S 402 , preparatory tumbling is performed. The preparatory tumbling is similar to the operation performed at step S 304  of the washing operation. 
     After the preparatory tumbling, the process proceeds to step S 405 . The drum  630  is rotated in a pattern of rinsing tumbling in accordance with the setting by the user. The drum  630  causes, by the rotation, the laundry to soak in the water, rise up and drop down. Thereby, the laundry is rinsed. 
     After the elapse of the rinsing tumbling period, the process shifts to step S 406 . At step S 406 , the drum  630  is rotated gently to disentangle the laundry in preparation for spin-drying rotation. 
     While in the above description, “stored-water rinsing” is performed in which rinsing is performed with rinsing water stored in the drum  630 , “poured-water rinsing” in which new water is always supplied or “shower rinsing” in which water is showered on the laundry may be performed. 
     (3-3. Spin-drying Operation) 
     Next, the contents of the spin-drying operation will be described with reference to the flowchart of  FIG. 7 . 
     First, at step S 501 , the drain valve  665  is opened. Thereby, the washing water or the rinsing water in the drum  630  is drained through the drain valve  665 . The drain valve  665  remains open during the spin-drying operation. 
     When a predetermined time has elapsed and the laundry is mostly dewatered, the drum  630  starts spin-drying rotation. When the drum  630  is rotated at high speed, the laundry is pressed against the inner wall of the drum  630  by the centrifugal force. Thereby, the water contained in the laundry gathers on the inner circumferential wall of the drum  630  and is released through the dewatering holes  633 . The washing water separated from the dewatering holes  633  is struck against the inner surface of the water tub  620 , and flows down to the bottom of the water tub  620  along the inner surface of the water tub  620 . Then, the water is drained out of the casing  610  through the drain outlet  623 , the drain pipe  660 , the filter casing  661 , the drain pipe  664  and the drain valve  665 . 
     In the sequence of  FIG. 7 , after spin-drying at a comparatively low speed is performed at step S 502  and step S 503 , spin-drying at a high speed is performed at step S 504  and step S 505 . After step S 505 , the process shifts to step S 506 . At step S 506 , power supply to the motor  640  is stopped, and the drum  630  is inertially rotated, without the brake being applied, so as to stop spontaneously. 
     (4. Structure of the Ion Elution Unit) 
     Next, the ion elution unit  100  provided in the slanted drum washing machine  601  will be described. 
     As shown in  FIG. 3 , the ion elution unit  100  (ion eluting means) is disposed in the middle of the main water supply pipe  52   a , that is, between the main water supply valve  50   a  and the detergent chamber  54 . Hereinafter, the structure and function of the ion elution unit  100  and the role that it plays by being provided in the slanted drum washing machine  601  will be described with reference to  FIGS. 8 and 9 . 
       FIGS. 8 and 9  are schematic cross-sectional views of the ion elution unit  100 .  FIG. 8  is a horizontal cross-sectional view thereof, and  FIG. 9  is a vertical cross-sectional view thereof. The ion elution unit  100  has a casing  110  made of an insulating material such as synthetic resin. The casing  110  has a water inlet  111  at its one end, and has a water outlet  112  at its other end. In the casing  110 , two plate-shaped electrodes  113  and  114  are disposed parallel to each other with a predetermined spacing in between. The electrodes  113  and  114  are made of a metal from which the metal ions having an antibacterial property derives, that is, silver, copper or zinc. 
     The electrodes  113  and  114  have terminals  115  and  116  at their one ends, respectively. It is desirable that the electrode  113  and the terminal  115 , and the electrode  114  and the terminal  116  be integrated with each other. When these cannot be integrated, the junctions between the electrodes and the terminals and the terminal portion in the casing  110  are coated with a synthetic resin so as not to be in contact with water, thereby preventing electrolytic corrosion. The terminals  115  and  116  protrude out of the casing  110  to connect with the driving circuit  120  (see  FIG. 10 ) in the controller  690 . 
     In the casing  110 , water flows parallel to the direction of the length of the electrodes  113  and  114 . When a voltage is applied to the electrode  113  and  114  while water is flowing in the casing  110 , metal ions of the constituent metal of the electrodes are eluted from the anode side of the electrodes  113  and  114 . The electrodes  113  and  114  are, for example, silver plates each measuring 2 cm by 5 cm and having a thickness of approximately 1 mm, and are disposed with a spacing of approximately 5 mm in between. 
     It is desirable that the constituent metal of the electrodes be silver, copper, zinc or an alloy thereof. Silver ions eluted from silver electrodes and zinc ions eluted from zinc electrodes are excellent in the sterilizing effect, and copper ions eluted from copper electrodes are excellent in the antifungal effect. On the other hand, from alloys thereof, since ions of the constituent metals can be eluted at the same time, excellent sterilizing and antifungal effects can be obtained. 
     Because of the structure of the ion elution unit  100 , the controller  690  (driving circuit  120 ) described later is capable of selecting whether to elute metal ions or not based on the presence or absence of the voltage application to the electrodes  113  and  114 . Moreover, the controller  690  is capable of controlling the metal ion elution amount, in other words, the metal ion concentration in the metal ion added water by controlling the current passed through the electrodes  113  and  114  and the voltage application time. Therefore, compared to a method in which metal ions are eluted from a metal ion carrier such as zeolite, this method is excellent in usability because selection of whether to add metal ions or not and the adjustment of the metal ion concentration can be all electrically performed. Further, the controller  690  is capable of controlling the metal ion concentration in the metal ion added water by changing the amount of water supplied to the ion elution unit  100  per unit time (the water supply flow amount, the water supply speed) by adjusting the opening and closing amount of the water supply valve  50 . 
     This metal ion concentration adjustment will be described in more detail. 
     The amount of metal elution from the electrodes  113  and  114  per unit time is approximately proportional to the current value. Therefore, by passing a large current through the electrodes  113  and  114 , the metal ion concentration in the metal ion added water can be easily made high. 
     When the value of the current passed through the electrodes  113  and  114  is fixed, since the metal elution amount per unit time is fixed, a larger amount of metal can be eluted by increasing the time for which the current is passed (voltage application time). Specifically, when the ion elution unit  100  is disposed on the water supply path, until metal of a predetermined mass calculated from a predetermined water amount and a predetermined concentration is eluted, metal elution is performed while water is supplied, and when metal of the predetermined mass is eluted, the metal elution is stopped, and water supply is continued until the predetermined water amount is reached. 
     By thus increasing the time for which metal elution is performed, the metal elution amount can be increased to increase the metal concentration. However, since the time for which current is passed through the electrodes  113  and  114  cannot exceed the time required for the washing machine  601  to supply water to the drum  630 , it is necessary to control the water supply flow amount (water supply speed) so as to be appropriate. For example, in a case where the current value is 29 mA, when the water supply speed is 19 L/min, the metal ion concentration can be increased to only 95 ppb at the maximum. However, by setting the water supply speed to 10 L/min, the metal ion concentration can be increased to 180 ppb at the maximum. 
     While the water supply amount varies among households, this causes no problem because the maximum water supply amount can be controlled by selection of the water supply valve and when the flow amount is lower than that, the time required for water supply is longer than that and the concentration can be more easily increased. 
     (5. Structure of the Driving Circuit of the Ion Elution Unit) 
     Next, the driving circuit  120  that drives the ion elution unit  100  will be described. 
       FIG. 10  is an explanatory view showing the schematic structure of the driving circuit  120 . A transformer  122  is connected to a commercial electric power source  121 , and the transformer  122  steps down a voltage of 100 V to a predetermined voltage. The output voltage of the transformer  122  is rectified by a full-wave rectifier circuit  123 , and is then converted into a constant voltage by a constant voltage circuit  124 . To the constant voltage circuit  124 , a constant current circuit  125  is connected. The constant current circuit  125  operates so as to supply a constant current to an electrode driving circuit  150  described later irrespective of variations in the value of the resistance through the electrode driving circuit  150 . 
     To the commercial electric power source  121 , a rectifying diode  126  is connected in shunt with the transformer  122 . The output voltage of the rectifying diode  126  is smoothed by a capacitor  127 , is then converted into a constant voltage by a constant voltage circuit  128 , and is then supplied to a microcomputer  130 . The microcomputer  130  controls the starting of a triac  129  connected between one end of the primary coil of the transformer  122  and the commercial electric power source  121 . 
     The electrode driving circuit  150  comprises NPN-type transistors Q 1  to Q 4 , diodes D 1  and D 2 , and resistors R 1  to R 7  which are interconnected as shown in the figure. The transistor Q 1  and the diode D 1  form a photocoupler  151 , and the transistor Q 2  and the diode D 2  form a photocoupler  152 . That is, the diodes D 1  and D 2  are photodiodes, and the transistors Q 1  and Q 2  are phototransistors. 
     Assuming now that the microcomputer  130  applies a high-level voltage to a line L 1  and a low-level voltage or OFF (zero voltage) to a line L 2 , the diode D 2  turns on, and this causes the transistor Q 2  to turn on. When the transistor Q 2  turns on, current flows through the resistors R 3 , R 4 , and R 7 , and this causes a bias to be applied to the base of the transistor Q 3 , so that the transistor Q 3  turns on. 
     On the other hand, since the diode D 1  is off, the transistors Q 1  is off, and the transistor Q 4  is also off. In this state, current flows from the anode-side electrode  113  to the cathode-side electrode  114 . Consequently, in the ion elution unit  100 , metal ions as positive ions, and negative ions are generated. 
     When current is passed through the ion elution unit  100  in one direction for a long time, the electrode  113  which is on the anode side in  FIG. 10  is depleted, and on the electrode  114  which is on the cathode side, impurities such as calcium in water are deposited in the form of scales. Moreover, chloride and sulfide of the constituent metal of the electrodes are generated on the surfaces of the electrodes. Since this degrades the performance of the ion elution unit  100 , in the present embodiment, the electrode driving circuit  150  is structured so as to be capable of being operated with the electrode polarity being reversed. 
     In reserving the electrode polarity, the microcomputer  130  switches the control so as to reverse the voltages of the lines L 1  and L 2  so that current flows in the opposite direction through the electrodes  113  and  114 . In this case, the transistors Q 1  and Q 4  are on, and the transistors Q 2  and Q 3  are off. The microcomputer  130  has a counter function, and performs the above-described switching every time a predetermined count is reached. 
     When a situation occurs such that the value of the current flowing between the electrodes is decreased by a change of the resistance in the electrode driving circuit  150 , in particular, a change of the resistance of the electrodes  113  and  114 , the constant current circuit  125  increases its output voltage to prevent the current reduction. However, when the cumulative time of use becomes long, the ion elution unit  100  reaches its end of life. When this happens, the current reduction cannot be prevented even if the electrode polarity is reversed, switching is made to an electrode cleaning mode to forcibly remove the impurities adhering to the electrodes by setting the time for which the polarity is a specific one so as to be longer than that in normal times, or the output voltage of the constant current circuit  125  is increased. 
     Therefore, in the present circuit, the current flowing between the electrodes  113  and  114  of the ion elution unit  100  is monitored by a voltage caused across the resistor R 7 , and when the current reaches a predetermined minimum current value, this is sensed by current sensing means. A current sensing circuit  160  is the current sensing means. Information indicating that the minimum current value is sensed is transmitted from a photodiode D 3  constituting a photocoupler  163  to the microcomputer  130  through a phototransistor Q 5 . The microcomputer  130  drives notification means through a line L 3  to cause it to make a predetermined warning notification. Warning notification means  131  is the notification means. The warning notification means  131  is disposed on the operation panel  616  or the controller  690 . 
     For accidents such as a short circuit in the electrode driving circuit  150 , current sensing means for detecting that the current becomes not less than a predetermined maximum value is provided, and based on the output of the current sensing means, the microcomputer  130  drives the warning notification means  131 . A current sensing circuit  161  is the current sensing means. Further, when the output voltage of the constant current circuit  125  becomes not more than the predetermined minimum value, a voltage sensing circuit  162  senses this, and at the same time, the microcomputer  130  drives the warning notification means  131 . 
     (6. Metal Ion Elution and Addition Operation) 
     Next, the operation of elution and addition of the metal ions generated by the ion elution unit  100  will be described. 
       FIG. 11  is a flowchart showing the sequence of metal ion elution and addition. The sequence of  FIG. 11  is executed, for example, in the stage of step S 401  (water supply) of the flow of the rinsing operation of  FIG. 6 . That is, when rinsing is started, at step S 411 , it is determined whether “metal ion addition” is selected by a selection operation on the operation panel  616  or not. This determination step may be executed earlier. When “metal ion addition” is selected at step S 411 , the process proceeds to step S 412 , and when it is not selected, the process proceeds to step S 412 ′ described later. 
     At step S 412 , the main water supply valve  50   a  is opened, and a predetermined flow amount of water is poured through the ion elution unit  100 . At the same time, the driving circuit  120  of the controller  690  applies a voltage between the electrodes  113  and  114  to cause ions of the constituent metal of the electrodes to be eluted into the water. At this time, the current flowing between the electrodes is direct current. The metal ion added water is added from the water supply mouth  53  into the drum  630 . 
     The controller  690  adds a predetermined amount of metal ion added water, and when determining that the metal ion concentration of the rinsing water reaches a predetermined value, stops the voltage application to the electrodes  113  and  114 . 
     When the metal ion added water is added, a finishing agent is also added. The finishing agent is added by opening the sub water supply valve  50   b  and pouring water into the finishing agent chamber  55  of the water supply mouth  53 . When a finishing agent is put in the finishing agent chamber  55 , the finishing agent is added into the washing tub  30  together with water from the siphon  57 . Since the siphon effect is not produced until the water level in the finishing agent chamber  55  reaches a predetermined level, a liquid finishing agent can be held in the finishing agent chamber  55  until water is poured into the finishing agent chamber  55  when the time comes. In the present embodiment, an operation on the precondition that a finishing agent is always added is performed without the selection of the addition of a finishing agent being made. When the user intends not to add a finishing agent, no finishing agent is set in the finishing agent chamber  55 . 
     However, in the present embodiment, the main water supply valve  50   a  and the sub water supply valve  50   b  are structured so as not to be opened at the same time. This is because if these are opened at the same time, the total water supply amount is large and this can cause overflow of water from the detergent addition box. 
     Specifically, as shown in  FIG. 12 , the controller  690  first repeats four times an operation to open only the sub water supply valve  50   b  for 5 seconds and then open only the main water supply valve  50   a  for 10 seconds, then, opens only the sub water supply valve  50   b  for 20 seconds, and then, opens only the main water supply valve  50   a  until a predetermined water level is sensed. With this operation, the finishing agent can be stably added without water overflowing from the detergent addition box. 
     At this time, as shown in the figure, the controller  690  performs the voltage application to the electrodes  113  and  114  of the ion elution unit  100  only when the main water supply valve  50   a  is open. This is because the ion elution unit  100  is disposed on the water supply path from the main water supply valve  50   a . That is, when the main water supply valve  50   a  is closed, hardly any water is present in the ion elution unit  100 , and when a voltage is applied under that condition, how much current flows is not known and consequently, the metal ion elution amount is unknown, which is undesirable. 
     Moreover, in the present embodiment, the power source of the driving circuit  120  of the controller  690  of the ion elution unit  100  and the power source of the solenoid valve of the main water supply valve  50   a  are in shunt with each other so as to branch from the same power source. By separately providing the power sources like this, the power on and off can be independently controlled, so that the voltage application to the ion elution unit  100  can be more reliably prevented from being performed other than when the main water supply valve  50   a  is open. 
     Moreover, in the present embodiment, as shown in the figure, the controller  690  applies a voltage to the electrodes  113  and  114  so that their polarities are reversed every 20 seconds. In the figure, a case where one electrode becomes an anode is represented by +, and a case where it becomes a cathode is represented by −. 
     The reasons why such electrode polarity reversal control is performed are as follows: 
     {circle around (1)} Since metal ions are eluted from the anode, if one electrode is always an anode, only that electrode is depleted. 
     {circle around (2)} Scales made of calcium or the like are apt to be deposited on a cathode. Although these scales can be removed by changing the scale deposited electrode to an anode, when one electrode is always a cathode, the amount of scale deposit is large, so that it is difficult to remove the scales even if the electrode is changed to an anode. 
     To avoid these problems, in the present embodiment, the control to periodically reverse the electrode polarity is performed. 
     On the other hand, at step S 412 ′, metal ion addition is not performed. That is, although step S 412 ′ is the same in that the controller  690  opens the main water supply valve  50   a  and a predetermined flow amount of water is poured through the ion elution unit  100 , the voltage application to the electrodes  113  and  114  in the ion elution unit  100  is not performed. Except this, step S 412 ′ is the same as step S 412 . 
     (7. Imbalance Correction) 
     Next, imbalance correction in the spin-drying operation will be described. 
     As shown in  FIG. 13 , the washing machine  601  of the present embodiment has sensing means  701  and imbalance correcting means  702 . 
     The sensing means  701 , which senses imbalance when the drum  630  is rotated, comprises, for example, physical sensing means such as a touch sensor, a shock sensor or an acceleration sensor, or sensing means in the form of software such as analyzing the voltage/current pattern of the motor. 
     The imbalance correcting means  702 , when the sensing means  701  senses imbalance at the time of spin-drying rotation of the drum  630  performed after metal ion added water is supplied to the drum  630 , corrects the imbalance by performing a processing different from that performed when imbalance is sensed in a case where no metal ion added water is supplied. While the imbalance correcting means  702  may comprise, for example, the controller  690 , it may comprise a different microprocessor. Moreover, in the present embodiment, the above-mentioned different processing is balance correction rinsing to supply the metal ion added water to the drum  630  and perform agitation. 
     In the spin-drying operation, when the sensing means  701  senses imbalance, in a case where that is the first sensing of imbalance, the imbalance correcting means  702  disentangles the laundry by performing tumbling without performing the supply of metal ion added water to the drum  630  as balance correction, and again starts spin-drying. When the sensing means  701  again senses imbalance in the spin-drying performed after balance correction is performed once and balance correction is again required, the imbalance correcting means  702  disentangles the laundry by performing tumbling while supplying metal ion added water to the drum  630 . 
     When metal ion added water is supplied to the drum  630  and the antibacterial treatment is performed on the laundry in the preceding rinsing operation, there is a possibility that some of the metal ions adhering to the laundry are lost because of the water supply to the drum  630  and this decreases the antibacterial property. However, the effect of entangling the laundry by supplying water is higher than the effect of enabling the antibacterial property of the laundry to be maintained by not supplying water, and the balance correction effect is high. 
     Therefore, the imbalance correcting means  702  uses metal ion added water also in the water supply at the time of balance correction, and prevents the reduction in the antibacterial property of the laundry by supplying the metal ion added water to the drum  630 . 
     When metal ion addition is not selected before spin-drying is performed and no antibacterial treatment is performed at the time of rinsing, the imbalance correcting means  702  does not supply metal ion added water but supplies normal tap water to the drum  630  at the time of balance correction. 
     As described above, in the present embodiment, the imbalance correcting means  702  performs balance correction rinsing to supply metal ion added water to the drum  630  and perform agitation when imbalance correction is performed at the time of spin-drying rotation of the drum  630  after the antibacterial treatment. When imbalance is sensed in a case where no metal ion added water is supplied, imbalance correction is performed by supplying normal tap water as described above, whereas when the antibacterial treatment has already been performed, by performing, as described above, a processing different from that performed when no metal ion added water is supplied which processing is called balance correction rinsing, even if metal ions added to the laundry in the preceding antibacterial treatment are washed away, the metal ions having been washed away can be surely made up for by supplying metal ion added water in the succeeding imbalance correction. Thus, imbalance correction can be performed without any loss of the antibacterial effect added to the laundry in the preceding antibacterial treatment. That is, imbalance correction can be performed while the efficacy of the antibacterial treatment on the laundry is ensured. 
     Moreover, when the antibacterial treatment by metal ions has already been performed in the preceding rinsing operation, in the balance correction rinsing, the imbalance correcting means  702  may be set the amount of metal ion added water supply to the drum  630  so as to be smaller than that in the preceding operation (rinsing operation). This is because even if such control is performed, the metal ions lost in the water supply at the time of spin-drying can be sufficiently made up for by the supply of the metal ion added water in the balance correction rinsing. 
     That is, since metal ions of an amount necessary for delivering the antibacterial effect on the laundry have already been supplied in the preceding metal ion added water supplying operation (rinsing operation), it is unnecessary to re-supply metal ions of the amount necessary for delivering the antibacterial effect even if the amount washed away in the succeeding balance correction rinsing is considered. With this, it can be prevented that metal ions are washed away without being used for the antibacterial treatment on the laundry in the balance correction rinsing and useless metal ions appear. 
     For the same reason, when the antibacterial treatment by metal ions has already been performed in the preceding rinsing operation, in the balance correction rinsing, the imbalance correcting means  702  may be set the metal ion concentration of the metal ion added water supplied to the drum  630  so as to be smaller than that of the metal ion added water supplied in the preceding operation (rinsing operation). 
     The above-described balance correction is applicable to vertical washing machines. Moreover, the adjustment of the metal ion added water supply amount can be performed by the imbalance correcting means  702  that adjusts the opening and closing of the water supply valve  50 . 
     (8. Setting of Silver Ion Concentration) 
     Next, the setting of the silver ion concentration of the metal ion added water generated by the ion elution unit  100  will be described. 
     In the slanted drum washing machine  601 , since the amount of water used for laundry washing is smaller than that of vertical washing machines, if the silver ion concentration is equal to that of the vertical washing machine, the amount of silver ions used for the antibacterial treatment is smaller than that of vertical washing machines, so that the antibacterial treatment on the laundry cannot be made effective. 
     Therefore, in the present embodiment, a relationship between the silver ion concentration of the metal ion added water (first metal ion added water) used for the antibacterial treatment in the slanted drum washing machine  601  and the antibacterial effect on the laundry at that time was examined, thereby examining the silver ion concentration necessary for obtaining the antibacterial effect in the slanted drum washing machine  601 . 
     The antibacterial effect was evaluated by a quantitative test method (bacterial liquid absorbing method) based on JIS (Japanese Industrial Standards) L1902:2002. More specifically, a bacterial liquid (Staphylococcus aureus) was inoculated on each of a cloth A 1  having undergone normal rinsing at the time of laundry washing and a cloth A 2  having undergone an antibacterial treatment (silver ion coating), and after these were held at a temperature of 37° C. for 18 hours, the number of bacteria on each cloth was counted. With the difference between the log fluctuation values thereof as bacteriostasis activation values, the antibacterial effect was evaluated based on the bacteriostasis activation value. Laundry washing was performed with the cloth load being 7 kg and the rinsing water amount being 30 L. For example, when the number of bacteria after 18 hours is 1.9×10 7 /ml on the cloth A 1  and 2.4×10 6 /ml on the cloth A 2 , the bacteriostasis activation value is log(1.9×10 7 )−log(2.4×10 6 )=0.9. Table 1 shows the relationship between the silver ion concentration and the bacteriostasis activation value at this time. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 Silver ion concentration (ppb) 
                 0 
                 90 
                 120 
               
               
                   
                 Bacteriostasis activation value 
                 0.1 
                 1.1 
                 2.5 
               
               
                   
                   
               
            
           
         
       
     
     From the result of Table 1, it is found that the bacteriostasis activation value monotonously increases as the silver ion concentration monotonously increases. Moreover, it is generally recognized that the antibacterial effect is achieved when the bacteriostasis activation value is not less than 2. Therefore, from Table 1, it can be said that the antibacterial effect is achieved when the silver ion concentration is not less than 120 ppb because the bacteriostasis activation value is not less than 2.5. 
     To further examine the relationship between the silver ion concentration and the bacteriostasis activation value, from the result of Table 1, the relationship between the silver ion concentration and the bacteriostasis activation value was graphed.  FIG. 14  shows the relationship between the silver ion concentration and the bacteriostasis activation value which relationship is graphed based on the result of Table 1. 
     As shown in  FIG. 14 , when the horizontal axis (x-axis) represents the silver ion concentration and the vertical axis (y-axis) represents the bacteriostasis activation value, it is found that the curved line smoothly connecting three points whose coordinates are the silver ion concentration and the bacteriostasis activation value of Table 1 can be approximated by y=0.0998 exp(0.0268x) which is a monotonously increasing function. Obtaining from this function the silver ion concentration where the bacteriostasis activation value is 2, that is, the value of x when y=2, x=112. 
     Therefore, since it is recognized that the antibacterial effect is achieved when the bacteriostasis activation value is not less than 2, from  FIG. 14 , it can be said that the antibacterial effect is achieved when the silver ion concentration is not less than 112 ppb. 
     Moreover, a test in a case where the sensing means  701  senses imbalance at the time of spin-drying and balance correction by the imbalance correcting means  702  is performed was also performed. While the water supply amount at the time of balance correction was 12.4 L and the concentration was 48 ppb, the bacteriostasis activation value was held at not les than 2, and it was confirmed that the antibacterial property was maintained. 
     Moreover, for the washing machine  601  of the same structure, the antibacterial property for diphtheroids was also performed with the silver ion concentration being 120 ppb, the cloth load being 7 kg and the rinsing water amount being 30 L. As the evaluation method, with the bacteria changed to Corynebacteriumxerosis which is a kind of diphtheroids, a test was performed with reference to the quantitative test method (bacterial liquid absorbing method) based on JIS (Japanese Industrial Standards) L1902:2002. As a result, the logarithmic value of the difference in the number of bacteria after 18 hours between a cloth having undergone the antibacterial treatment (silver ion coating) and a control cloth determined by the bacterial liquid absorbing method of JIS L1902 was 2.1. 
     According to the bacterial liquid absorbing method of JIS L1902, although the bacteria ( Staphylococcus aureus ) are different from  Corynebacterium xerosis , the antibacterial property is regarded as being obtained when the logarithmic value of the difference in the number of bacteria is not less than 2.0. Moreover, in JIS Z2801 and a test to measure the antibacterial performance and the disinfection performance such as a “criterion for use of terms associated with suppression of bacteria and the like” of the Home Electric Appliances Fair Trade Conference, that the logarithmic value of the difference in the number of bacteria is not less than 2.0 is also an index of the evaluation of the antibacterial power and the disinfecting power. Therefore, from the above-mentioned test result, it can be said that the antibacterial power for diphtheroids is also obtained under the above-mentioned condition. 
     On the other hand, the laundry was repetitively rinsed with water with a silver ion concentration of more than 900 ppb (metal ion added water), and although no change was recognized on the appearance of the laundry when the rinsing was repeated three times, the reflectance after sun drying was lower by 3% than that before rinsing when the rinsing was performed five times. It is considered that this is because black discolored substances derived from a silver compound adhere to the laundry. On white laundry, the adhesion of such blackened substances is conspicuous, and even on laundry that is not white, blackened substances can become conspicuous when the laundry is repetitively washed. From this, it can be considered that the upper limit of the silver ion concentration is 900 ppb. 
     From the above, in the slanted drum washing machine  601 , it is desirable that the silver ion concentration in the metal ion added water to which metal ions (silver ions) eluted from the ion elution unit  100  are added be not less than 112 ppb and not more than 900 ppb and it is more desirable that it be not less than 120 ppb and not more than 900 ppb. 
     As described above, the slanted drum washing machine  601  of the present embodiment is a washing machine having the ion elution unit  100  that elutes metal ions from the electrodes  113  and  114  and adds them to water, and the drum  630  disposed so that the rotation axis thereof is at an angle with respect to the vertical direction and in which laundry is put. The metal ions are silver ions, and the silver ion concentration of the metal ion added water (first metal ion added water) is not less than 112 ppb. 
     With this structure, since the amount of silver ions contained in the same amount of water is larger than, for example, that of a second metal ion added water (with a silver ion concentration of 3 to 50 ppb) used for the antibacterial treatment on the laundry in vertical washing machines, even in the slanted drum washing machine  601  designed to use a small amount of water, at least the necessary amount of silver ions (the amount of silver ions where the bacteriostasis activation value is not less than 2) for delivering the antibacterial effect on the laundry can be secured. Consequently, the antibacterial effect equal to or higher than that obtained in the antibacterial treatment in vertical washing machines can be obtained also in the slanted drum washing machine  601 , so that the antibacterial effect can be surely delivered by surely performing the antibacterial treatment on the laundry. 
     In particular, when the silver ion concentration in the first metal ion added water is not less than 120 ppb, a larger amount of silver ions can be contained in the water than when the silver ion concentration is 112 ppb. Therefore, when the amount of first metal ion added water is the same as that when the silver ion concentration is 112 ppb, the antibacterial effect by silver ions can be further delivered compared to when the first metal ion added water having such a silver ion concentration (112 ppb ) is used. Moreover, since even when the amount of first metal ion added water is smaller than that when the silver ion concentration is 112 ppb, a silver ion amount equal to that can be secured, the amount of water can be further reduced while the antibacterial effect is obtained, so that water saving effect is obtained. 
     Moreover, in the slanted drum washing machines  601  of the present embodiment, the silver ion concentration in the first metal ion added water is not more than 900 ppb. With this structure, it can be prevented that a silver compound (blackened substance) is generated by an excessive silver ion amount and adheres to the laundry and this makes the laundry dirty. 
     Since a metal ion amount necessary for the antibacterial treatment can be secured even if there is a change in water amount by controlling the metal ion concentration as described above, the slanted drum washing machine  601  of the present embodiment can be expressed as follows: 
     The slanted drum washing machine  601  of the present embodiment is a washing machine having the laundry tub (drum  630 ) in which the laundry is put, and the ion elution unit  100  that elutes metal ions from the electrodes  113  and  114 , adds them to water and supplies metal ion added water to the laundry tub. The controller  690  (controlling means) is provided that changes the metal ion concentration of the metal ion added water in accordance with the amount of metal ion added water supplied from the ion elution unit  100  to the drum  630 . 
     For example, in a case where the amount of laundry is the same, when the amount of metal ion added water supplied to the drum  630  is decreased, the controller  690  increases the metal ion concentration of the metal ion added water, for example, to not less than 112 ppb. With this concentration control, even when the amount of metal ion added water supply is small, the metal ion amount necessary for delivering the antibacterial effect on the laundry can be secured, so that the antibacterial effect can be surely delivered by surely performing the antibacterial treatment on the laundry. 
     On the other hand, when the amount of metal ion added water supplied to the drum  630  is increased, the controller  690  decreases the metal ion concentration of the metal ion added water, for example, in a range where the concentration is not less than 112 ppb. In a case where the metal ion concentration is the same, when the amount of metal ion added water is increased, the amount of metal ions contained therein is increased accordingly. When the amount is excessively increased, excessive metal ions are not used for the antibacterial treatment on the laundry but are flown as drained water to be wasted. Moreover, it occurs that the amount of metal adhering to the laundry increases and this makes the laundry dirty. Therefore, such a problem can be avoided by the above-described concentration control. 
     The controller  690  may change the metal ion concentration of the metal ion added water in accordance with the supply water level of the metal ion added water supplied from the ion elution unit  100  to the drum  630 . In this case, effects similar to the above-mentioned ones can be obtained. 
     Moreover, when the amount of metal ion added water supplied from the ion elution unit  100  to the drum  630  changes, the liquid ratio also changes. Here, the liquid ratio refers to the ratio (L/kg) between the laundry amount (kg) and the amount (L) of water supplied to the drum  630 , in other words, refers to the amount of water used per kg of laundry. Therefore, it can be said that the controller  690  may change the metal ion concentration of the metal ion added water in accordance with the liquid ratio. For example, it is considered that the controller  690  performs control to increase the metal ion concentration to not less than 112 ppb when the liquid ratio is decreased and decrease the metal ion concentration, for example, in a range where the bacteriostasis activation value is not less than 2 when the liquid ratio is increased. 
     The amount (the total weight, the amount of load) of laundry put in the drum  630  can be sensed by non-illustrated sensing means. Consequently, the controller  690  calculates the liquid ratio based on the amount of laundry sensed by the sensing means and the amount of water usage set by the operation panel  616 , and changes the metal ion concentration in accordance with the liquid ratio. 
     Even with this structure, a necessary amount of metal ions can be always secured in accordance with the amount of laundry irrespective of changes in liquid ratio. Consequently, even when the liquid ratio is changed by a change in the amount of metal ion added water supplied to the laundry tub, the antibacterial effect can be surely delivered by surely performing the antibacterial treatment on a predetermined amount of laundry. Also, it can be prevented that a necessary amount or more of metal ions are flown as drained water to be wasted without being used for the antibacterial treatment on the laundry and that the amount of metal adhering to the laundry increases and this makes the laundry dirty. 
     Moreover, various tests were performed under a condition where the cloth load was 7 kg and the water amount at the time of rinsing was 30 L, that is, under a condition where the cloth load of the laundry was 7 kg and the liquid ratio was 4.3 L/kg, and from these results, it can be said that in a washing machine that performs laundry washing and rinsing with the cloth load of the laundry being 7 kg and the liquid ratio being not more than 4.3 L/kg, by setting the metal ion concentration to not less than 112 ppb (more desirably, not less than 120 ppb ), the bacteriostasis activation value of the metal ion added laundry can be made not less than 2, so that an excellent antibacterial effect can be exerted on the laundry. Therefore, in a washing machine that performs laundry washing with the liquid ratio being 5 L/kg (the cloth load of the laundry being 7 kg), it is considered that the bacteriostasis activation value of the laundry is not less than 2 or a value close thereto, and it is considered that an excellent antibacterial effect is obtained. 
     That is, it is considered that the antibacterial effect can be surely exerted on the laundry by the controller  690  performing control so that when the liquid ratio of the metal ion added water used for the laundry is not more than 5 L/kg (the cloth load of the laundry 7 kg), the metal ion concentration of the metal ion added water supplied from the ion elution unit  100  is not less than 112 ppb (desirably, when the liquid ratio is not more than 4.3 L/kg (the cloth load of the laundry 7 kg), the metal ion concentration is not less than 120 ppb ). By doing this, metal ions with which a sufficient bacteriostasis activation value is obtained can be added to the laundry without an unnecessary amount of metal ions being consumed. 
     In other words, by setting a minimal metal ion concentration necessary for a washing machine that operates with a low liquid ratio, the following problem particular to washing machines can be solved: When the metal ion concentration is low, a sufficient antibacterial effect cannot be exerted on laundry where ones with high water absorbency and ones with low water absorbency are mixed, and when the metal ion concentration is excessively high, unnecessary metal ions are consumed. Consequently, an antibacterial effect by metal ions with efficiency can be exerted on the laundry. 
     While the control of the metal ion concentration is performed by the controller  690  in the above, the metal ion concentration may be preset in a range where the metal ion concentration is not less than 112 ppb (desirably, not less than 120 ppb ) and not more than 900 ppb. 
     Moreover, when the liquid ratio of the metal ion added water of a predetermined concentration and a predetermined amount (for example, 90 ppb and 42 L) used for a predetermined amount of laundry (for example, 7 kg) which metal ion added water is suitable for obtaining an effective bacteriostasis activation value (for example, not less than 2) is the reference liquid ratio (6 L/kg) in a case where metal ions are added, and the metal ion concentration (90 ppb ) is the concentration (reference concentration) in a case where a bacteriostasis activation value is obtained where it can be evaluated that an antibacterial effect is exerted at the reference liquid ratio, according to the present invention, the following control may be performed: 
     In controlling the amount of metal ion elution by the ion elution unit  100  so that the metal ion concentration is a predetermined reference concentration, when the liquid ratio of the amount of water used in at least one of the washing, rinsing, spin-drying and drying operations becomes lower than the reference liquid ratio for laundry of the amount (the total weight, the amount of load) the same as this, the controller  690  may perform control to increase the metal ion concentration to be higher than the reference concentration, and when the liquid ratio in the above-mentioned operation becomes higher than the reference liquid ratio for laundry of the amount the same as this, the controller  690  may perform control to maintain the metal ion concentration at the predetermined reference concentration or decrease it so as to be lower than the reference concentration. 
     By such metal ion concentration control, whatever change the liquid ratio makes, the metal ion amount necessary for delivering the antibacterial effect which amount depends on the amount of laundry being used (for example, the metal ion amount where the bacteriostasis activation value is not less than 2) can be substantially sufficiently secured. Consequently, even if the liquid ratio changes, the antibacterial effect can be surely exerted on the laundry being used while metal ions being used are prevented from being wasted, so that liquid ratio change can be sufficiently handled. 
     From the above, in the washing machine  1  of the present embodiment, the controller  690  performs control to change the metal ion concentration of the metal ion added water supplied from the ion elution unit  100  so that the bacteriostasis activation value of the metal ion added laundry is not less than 2 whatever changes the amount of supplied water, the water level of the supplied water and the liquid ratio make. 
     Moreover, from the above, the following can be said: The slanted drum washing machine  601  is a washing machine having the ion elution unit  100  that elutes metal ions from the electrodes  113  and  114  and adds them to water, and the drum  630  disposed so that the rotation axis thereof is at an angle with respect to the vertical direction and in which laundry is put, the metal ions are silver ions, and the silver ion concentration of the first metal ion added water is set so that the amount of silver ions contained in the first metal ion added water used for the antibacterial treatment on the laundry in the drum  630  is not less than the amount of silver ions contained in the second metal ion added water of an amount necessary for the antibacterial treatment on the laundry by vertical washing machines where the washing tub is disposed so that the rotation axis thereof is in the vertical direction. 
     Moreover, the following can also be said: The slanted drum washing machine  601  is a washing machine having the ion elution unit  100  that elutes metal ions from the electrodes  113  and  114  and adds them to water, and the drum  630  disposed so that the rotation axis thereof is at an angle with respect to the vertical direction and in which laundry is put, the metal ions are silver ions, and the silver ion concentration of the first metal ion added water used for the antibacterial treatment on the laundry in the drum  630  is set to a concentration where an antibacterial effect similar to that obtained by the second metal ion added water can be obtained with an amount of water smaller than the amount of second metal ion added water necessary for the antibacterial treatment on the laundry by vertical washing machines where the washing tub is disposed so that the rotation axis thereof is in the vertical direction. 
     While an example in which silver ions are mainly used as the metal ions is described in the present embodiment, it is to be noted that the structure of the present invention in which the metal ion concentration of the metal ion added water is changed according to the water amount and the liquid ratio may be adopted to a case where copper ions or zinc ions are used as the metal ions. Even in that case, the appropriate range of the metal ion concentration change is considered to be not less than 112 ppb and not more than 900 ppb, preferably, not less than 120 ppb and not more than 900 ppb. 
     (9. Control of the Amount of Metal Ion Added Water) 
     Next, the control of the amount of metal ion added water supplied from the ion elution unit  100  will be described. 
     It is as described above that the laundry washing process of the slanted drum washing machine  601  comprises a plurality of individual operations: the washing operation, the rinsing operation, the spin-drying operation, and when required, the drying operation. In the present embodiment, the controller  690  as the controlling means elutes metal ions (silver ions) from the ion elution unit  100  in any of the individual operations, and performs control so that the water amount in the individual operation in which the metal ion elution is perfumed is larger than that in the other operations. 
     In the present invention, the metal ion elution is performed in the rinsing operation as one of the individual operations as mentioned above, and at this time, the controller  690  performs control so that the water amount in the rinsing operation is larger than the water amount in the preceding washing operation. For example, when the water amount in the washing operation is 20 L, the water amount in the rinsing operation is, for example, 30 L. 
     This water amount control can be performed by the controller  690  adjusting the opening and closing of the water supply valve  50  for each individual operation. Specifically, the controller  690  causes the water supply valve  50  to be open until a water level sensor (not shown) detects a predetermined water level, and when the predetermined water level is detected, the controller  690  closes the water supply valve  50  to thereby adjust the water amount. Moreover, in this example, the silver ion concentration of the water (metal ion added water) to which metal ions (silver ions) eluted in the metal ion elution operation are added is the above-mentioned not less than 112 ppb and not more than 900 ppb which is a range suitable for the antibacterial treatment. 
     By the controller  690  performing control so that the water amount in an individual operation where silver ion elution is performed (for example, the rinsing operation) is larger than that in another individual operation (for example, the washing operation) as described above, the laundry (for example, cloth) in the drum  630  is more easily soaked in water in the individual operation (rinsing operation). Consequently, the eluted silver ions are apt to more uniformly adhere to the laundry. As a result, the antibacterial effect on the laundry can be more uniformly obtained on the entire laundry, and the antibacterial treatment can be made more effective. 
     In particular, by the controller  690  performing silver ion elution in the rinsing operation and performing control so that the water amount in the rinsing operation is larger than that in the preceding washing operation, the laundry is uniformly soaked in rinsing water (metal ion added water) at the time of rinsing of the laundry whose dirt has been removed in the washing operation, and the silver ions contained in the rinsing water more uniformly adhere to the entire laundry. Consequently, an antibacterial effect that is uniform on the entire laundry can be surely obtained by the antibacterial treatment at the time of rinsing. 
     (10. Rotation Control of the Drum) 
     Next, the rotation control of the drum  630  in the rinsing operation will be described. 
     In the present embodiment, as shown in the flowchart of  FIG. 11 , the elution of the metal ions (silver ions) from the ion elution unit  100  is performed, for example, in the water supply stage of step S 401 , that is, after the intermediate spin-drying of step S 500  in the flow of the rinsing operation of  FIG. 6 . At this time, the controller  690  performs control to soak the laundry sticking to the inner surface of the drum  630  in the metal ion added water by supplying the metal ion added water to the drum  630  and rotating the drum  630  after the intermediate spin-drying. 
     In the case of vertical washing machines, since the laundry (for example, cloth) after spin-drying sticks to the entire area of the inner surface of the washing tub because the washing tub rotates at high speed at the time of spin-drying, when silver ion processing is performed on the entire laundry thereafter, it is necessary to increase the water level of the silver ion water in the washing tub so that the laundry is all soaked in the silver ion water and strongly agitate the laundry so as to be separated from the inner surface of the washing tub. 
     For this reason, in vertical washing machines, when silver ion water is supplied and silver ion rinsing is performed, for example, for ten minutes after the intermediate spin-drying in the rinsing operation, for example, for the first four minutes, the pulsator is turned on for 1.9 second, whereas it is turned off for 0.7 second to strongly agitate the laundry. Since the agitation by the pulsator which can largely damage cloth (laundry) and puts a heavy load on the motor cannot be performed for ten minutes, it is customary to perform agitation only for the first four minutes. 
     On the contrary, in the slanted drum washing machine  601  of the present embodiment, since the drum  630  makes slanted axis rotation or rotation close to that, by the intermediate spin-drying by rotation of the drum  630 , even if the laundry sticks to the inner surface of the drum  630 , the laundry can be soaked in the metal ion added water supplied in the drum  630  only by rotating the drum  630 . When the drum  630  continues rotating, the laundry sticking to the inner surface of the drum  630  is repetitively soaked into the metal ion added water and separated from the water. 
     Since the laundry after the intermediate spin-drying sticks to the inner surface of the drum  630  and is not bulky, it is easily soaked in the silver ion water (metal ion added water) even if the water level of the silver ion water in the drum  630  is low. Therefore, water may be saved by performing control to set the liquid ratio at the time of the rinsing using the metal ion added water after the intermediate rinsing so as to be lower than that at the time of normal rinsing not using the metal ion added water and increase the silver ion concentration. 
     Therefore, in the slanted drum washing machine  601 , it is unnecessary to rotate the drum  630  at a speed as high as the washing tub of vertical washing machines. Consequently, it is unnecessary to strongly agitate the laundry in the drum  630 , so that the drum  630  can be rotated at a comparatively gentle rotation speed (for example, 50 rotations/min), for example, for ten minutes. As a result, damages (for example, wear and tear on cloth) due to laundry agitation can be suppressed. Moreover, the low-speed rotation of the drum  630  can reduce the load on the driving means (for example, a motor) thereof, so that the power consumption by not only the driving means but also the slanted drum washing machine  601  can be reduced. 
     In particular, by the controller  690  rotating the drum  630  at a comparative low rotation speed of not less than 10 rotations/min and not more than 120 rotations/min to thereby soak the laundry sticking to the inner surface of the drum  630  in the metal ion added water, the above-mentioned effect can be surely obtained. 
     Since the above-described advantages are produced, it can be said that the washing machine  601  of the present embodiment has a structure where the laundry tub in which laundry is put is the drum  630  disposed so that the rotation axis thereof is at an angle with respect to the vertical direction, the above-described laundry washing process includes the rinsing operation, metal ion elution by the controller  690  (controlling means) and the ion elution unit  100  is performed in the rinsing operation, and the laundry sticking to the inner surface of the drum  630  is soaked in the metal ion added water by supplying the metal ion added water to the drum  630  and rotating the drum  630  after the intermediate spin-drying in the rinsing operation. 
     (11. Antibacterial and Antifungal Effects in the Machine) 
     Next, the antibacterial and antifungal effects in the slanted drum washing machine  601  will be described. 
     In the slanted drum washing machine  601 , since the drum  630  and the water tub  620  are substantially laterally disposed, laundry is frequently put in from the front of the washing machine  601 . For this reason, the door  612  serving as the lid for putting laundry into the drum  630  is normally provided on the front of the washing machine  601 . 
     However, when the door  612  is provided on a surface other than the top surface of the washing machine  601  like this, there is a possibility that water leaks therefrom. Therefore, in the washing machine  601 , the door packing  613  is provided, and when the door  612  is closed, the performance of sealing between the door  612  and the body  610  is high and the body  610  can be sealed off. Moreover, in the slanted drum washing machine  601 , unlike vertical washing machines, because of space limitation, it is difficult to keep the door  612  open when the washing machine is not in use. 
     Therefore, in the slanted drum washing machine  601 , the water remaining in the washing machine  601  after laundry washing is finished does not easily vaporize. In some slanted drum washing machines  601 , water is drained by a pump because of demands for incorporation into built-in kitchens, and particularly in this case, the amount of remaining water is large compared to natural water draining by the gravity. 
     Moreover, recently, some vertical washing machines have a structure with high sealing performance where a drying function is provided and neither heat and moisture at the time of drying nor produced dust leaks out. In this type of washing machines, water easily remains in the machine like in the slanted drum washing machine  601 . 
     When water remains in the machine, the remaining water can become rotten to emit an offensive smell and mold easily propagates, so that the hygienic condition is degraded. In particular, in the machine, since nutritive substances such as dirt that adhered to the laundry and detergent residues are abundant, bacteria and mold readily propagate. Moreover, when such bacteria adhere to the laundry, the laundry becomes dirty, and the skin can be adversely affected when the washed cloths are worn. 
     Therefore, in the present embodiment, this problem is avoided by adopting the following structure: 
     In the slanted drum washing machine  601  of the present embodiment, the water remaining in the machine after all the individual operations (the washing operation, the rinsing operation, the spin-drying operation, and when required, the drying operation) in the laundry washing process are finished (more specifically, water remaining in the drain path from the ion elution unit  100  through the drain pipe  664 ) is the metal ion added water (silver ion water) containing metal ions (silver ions) eluted from the ion elution unit  100 . This can be realized by the controller  690  performing control to elute metal ions from the ion elution unit  100  and add them to the water in, of the laundry washing process, the last individual operation that requires water. 
     For example, when the drying operation is not performed in accordance with the laundry washing mode, as shown in the flowchart of  FIG. 4 , the controller  690  performs the above-described silver ion water supply in the last operation, that requires water, of the individual operations (the final rinsing operation (step S 400 - 3  of  FIG. 4 ) of the rinsing operation). In this case, the silver ion water supplied to the drum  630  is used for the antibacterial treatment on the laundry, and is then removed from the laundry in the spin-drying operation and drained out of the machine. At this time, the silver ion water is not completely drained out of the machine but a slight amount thereof normally remains in the drum  603  and in the drain path (for example, in the drain pipe  664 ) without being drained. Moreover, after the last individual operation that requires water is finished, it never occurs that different water flows in the drum  63  and the drain path. 
     Moreover, when the last operation is the drying operation by water-cooling dehumidification, in the drying operation, the controller  690  performs control to add the metal ions eluted from the ion elution unit  100  to the cooling water for cooling the air discharged from the drum  630 . In this case, after the cooling of the air is finished, the cooling water is drained out of the machine through a drain path (for example, the drain pipe  664 ). Even in this case, the cooling water is not completely drained out of the machine but a slight amount thereof normally remains in the drain path without being drained. Moreover, since the drying operation is the last operation of the laundry washing process, it never occurs that different water flows in the drain path. 
     Since the drying operation employing the water-cooling dehumidification method requires the cooling water and the drying operation is the individual operation performed lastly in the laundry washing process, it can be said that the drying operation is the last individual operation, that requires water, of the laundry washing process. 
     As described above, when at least one individual operation of the laundry washing process is performed, the controller  690  (controlling means) performs control to elute metal ions from the ion elution unit  100  and add them to water in, of the individual operations, the last individual operation that requires water. With this, after all the individual operations of the laundry washing process are finished, even if water remains in the machine (in the drain path from the ion elution unit  100  through the drain pipe  664 ), the remaining water is metal ion added water. 
     When the water remaining in the machine is normal tap water, there are cases where the water becomes rotten to emit an offensive smell and mold propagates. In particular, in the slanted drum washing machine  601 , since it is necessary to prevent water from leaking from the door  612  or the like on the front, the sealing performance is high compared to vertical washing machines and therefore, the water remaining in the drum  630  in the machine particularly does not easily vaporize and an offensive smell and mold are readily generated as mentioned above. 
     However, by employing the above-described structure of the present embodiment, since the water remaining in the machine after the last operation is finished is antibacterial metal ion water, even in the highly hermetically sealed machine, by the antibacterial performance of the metal ions (silver ions) contained in the metal ion water, it can be surely prevented that an offensive smell is emitted from the remaining water and mold propagates in the machine because of the remaining water. Consequently, a slanted drum washing machine  601  excellent in hygienic condition can be realized. 
     Moreover, when the last individual operation that requires water is the rinsing operation in which the laundry put in the laundry tub is rinsed, the controller  690  adds the metal ions eluted from the ion elution unit  100  to the water supplied to the laundry tub in the rinsing operation. With this, the hygienic condition can be surely improved by suppressing the generation of an offensive smell and mold by the metal ion added water remaining in the machine after the rinsing operation is finished. 
     Moreover, when the last individual operation is the drying operation in which the laundry is dried by supplying hot air to the laundry tub in which the laundry is put and the air discharged from the laundry tub is cooled by the cooling water, the controller  690  adds the metal ions eluted from the ion elution unit  100  to the cooling water in the drying operation. With this, the hygienic condition can be surely improved by suppressing the generation of an offensive smell and mold by the metal ion added water remaining in the machine after the drying operation is finished. 
     While the above description is given based on the premise that the drain path through which water is drained from the laundry tub (drum  630 ) (hereinafter, referred to also as a first drain path) and the drain path of the cooling water used in the drying operation (hereinafter, referred to also as a second drain path) are common, there are cases where it is difficult that such drain paths are common because of the structure of the washing machine  601 . That is, there are cases where the first drain path and the second drain path are partly or totally different. 
     In a case where the first drain path and the second drain path are thus at least partly different, when (1) the drying operation in which hot air is supplied to the laundry tub to dry the laundry and the air discharged from the laundry tub is cooled by cooling water and (2) an operation (for example, the rinsing operation) in which water is supplied to the laundry tub immediately before the drying operation are both performed as the individual operations constituting the laundry washing process in accordance with the selected laundry washing mode, the last individual operation that requires water is the operation of (1). Therefore, even if metal ions are added only to the cooling water used in the last individual operation, the metal ion added water cannot be left in the first drain path although the metal ion added water can be left in the second drain path. 
     Therefore, in a case where the first drain path and the second drain path are at least partly different and the operations of (1) and (2) are both performed, the controller  690  performs control to add the metal ions eluted from the ion elution unit  100  to both the water supplied to the laundry tub in the operation of (2) and the cooling water used in the drying operation of (1). 
     By doing this, after the operations of (1) and (2) are finished, the metal ion added water can be left in each of the first and second drain paths in the end. Consequently, the generation of an offensive smell due to rotting of the water remaining in the drain paths in the machine and the propagation of mold can be suppressed, so that a washing machine excellent in hygienic condition can be realized. 
     (12. Others) 
     While an embodiment of the present invention has been described, the scope of the invention is not limited thereto, but the present invention may be embodied with various modifications added thereto without departing from the spirit of the invention. 
     For example, the position of disposition of the ion elution unit  100  is not limited to between the water supply valve  50  and the water supply mouth  53 . The ion elution unit  100  may be disposed anywhere between the connection pipe  51  and the water supply mouth  53 . That is, it may be disposed on the upstream side of the water supply valve  50 . When the ion elution unit  100  is disposed on the upstream side of the water supply valve  50 , the ion elution unit  100  is always soaked in water, so that it can be prevented that water leakage is caused by the sealing member being changed in quality by being dried. 
     Moreover, the ion elution unit  100  may be disposed outside an outer case  10 . For example, a structure is considered such that the ion elution unit  100  is formed as an interchangeable cartridge and attached to the connection pipe  51  by means such as screwing and a water supply hose is connected to the cartridge. 
     Aside from whether the ion elution unit  100  is in the form of a cartridge or not, when the ion elution unit  100  is disposed outside the outer case  10 , the ion elution unit  100  can be replaced without the door provided on a part of the washing machine  1  being opened or the panel being detached, which facilitates maintenance. Further, the charging portion inside the washing machine  1  cannot be touched, which ensures safety. 
     To the ion elution unit  100  disposed outside the outer case  10  as described above, electric current is supplied by connecting a cable extending from the driving circuit  120  through a waterproof connector. Without resort to power supply from the driving circuit  120 , the machine may be driven with a battery as a power source, or may be driven with a hydraulic power unit having a water wheel so as to be in contact with the flow of the supplied water, as a power source. 
     The ion elution unit  100  may be sold as an independent product so that mounting of the ion elution unit  100  on apparatuses other than washing machines is promoted. 
     Moreover, the ion elution unit  100  may be disposed in a position in the water tub  620  which position is soaked in water when water is supplied to a predetermined water level: By doing this, when the ion elution unit  100  is soaked in the water in the water tub  620 , metal ions can be eluted at any time irrespective of the water supply timing. Consequently, a sufficient time can be taken to elute metal ions, so that metal ions can be used in a high concentration and the current and voltage can be low to obtain a predetermined concentration. 
     Moreover, since it is unnecessary to provide a water supply sequence in the laundry washing process for ion elution, it is unnecessary that the time required for performing all the operations of laundry washing be long. Further, when metal ions are added to the water supplied to the drum  630 , it is necessary to reduce the water supply flow amount in order to secure the time necessary for metal ion elution. Although this leads to an increase in the time required for laundry washing, this structure unnecessitates such a consideration. 
     While the slanted washing machine  601  having the drum  630  disposed so that the rotation axis thereof is at an angle with respect to the vertical direction as the laundry tub in which laundry is put is described in the present embodiment, it is to be noted that the structures described in the present embodiment such as the structure in which the metal ion concentration of the metal ion added water is changed according to the water amount and the liquid ratio are applicable to vertical washing machines having a washing tub as the laundry tub so that the rotation axis thereof is in the vertical direction. 
     Moreover, the ion eluting means for eluting metal ions is not limited to the above-described structure (ion elution unit  100 ). The ion eluting means may comprise a structure in which a metal ion eluting material (in the case of a silver eluting material, silver sulfide or the like) is filled in a cartridge and water is passed through the cartridge to thereby elute metal ions. The above-described ion elution unit  100  or one capable of performing metal ion concentration control equal thereto is suitable in that the metal ion concentration of a limited amount of supplied water can be finely controlled in a short time. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to a washing machine having ion eluting means for generating metal ion added water used for correcting imbalance in the laundry tub (the drum, the washing tub) at the time of spin-drying rotation.