Patent Publication Number: US-7708896-B2

Title: Ion eluting unit and device loaded with same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ion elution unit for eluting metal ions having an antimicrobial effect into water, and also relates to an appliance, in particular a washer, that uses water mixed with metal ions generated by such ion elution unit. 
     2. Description of the Related Art 
     When laundry is washed in a washer, it is common to add a treatment substance to water, in particular, to rinsing water. Typical examples of such treatment substances include softening and starching agents. In addition to these, in recent years, the demand has been increasing for treatment whereby laundry is subjected to antimicrobial treatment. 
     From the hygienic point of view, it is desirable to hang laundry in the sun to dry. However, in recent years, with the increase in the number of women who go to work, and with the increase in the number of nuclear families, there have been an increasing number of households where no one is at home in the daytime. In these households, there is no choice but to hang laundry indoors to dry. Even in households where someone is at home in the daytime, in a rainy weather, there is no choice but to hang laundry indoors to dry. 
     As compared with hanging laundry in the sun to dry, hanging it indoors tends to promote growth of bacteria and mold in laundry. This tendency is marked particularly when it takes time to dry laundry, as when humidity is high, such as in a rainy season, or when temperature is low. As the amount of bacteria and mold increases, laundry may become smelly. For this reason, in households where there is usually no choice but to hang laundry indoors to dry, there is a high demand for antimicrobial treatment of textile articles for the purpose of suppressing growth of bacteria and mold. 
     Nowadays, many clothes are available that have previously been treated with antimicrobial/deodorizing or antifungal treatment. However, it is difficult to replace all the textile articles in a household with those previously treated with antimicrobial/deodorizing treatment. Moreover, even with such textile articles, as they are washed repeatedly, the efficacy of antimicrobial/deodorizing treatment wears off. 
     Conceived under these circumstances was the idea of treating laundry with antimicrobial treatment every time it is washed. For example, Japanese Utility Model Laid-Open No. H5-74487 discloses an electric washer furnished with an ion generator that generates metal ions, such as silver ions or copper ions that exert a sterilizing effect. Japanese Patent Application Laid-Open No. 2000-93691 discloses a washer that generates an electric field with which to sterilize cleaning fluid. Japanese Patent Application Laid-Open No. 2001-276484 discloses a washer furnished with a silver ion adding unit that adds silver ions to cleaning water. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an ion elution unit for generating metal ions having an antimicrobial effect in which metal ion generation efficiency is high. Another object of the present invention is to provide an appliance, in particular a washer, that uses water mixed with metal ions generated by such an ion elution unit to avoid adverse effects brought about growth of bacteria, and that permits the ion elution unit to operate efficiently. 
     To achieve the above object, according to the present invention, an ion elution unit is constructed in the following manner. In an ion elution unit generating metal ions by applying a voltage between electrodes, a space is secured between the electrodes and the inner surface of the casing of the ion elution unit. With this construction, the electrodes are supported with a space secured between them and the inner surface of the casing. This prevents a metal layer from growing from the electrodes to the inner surface of the casing and eventually causing short-circuiting between the electrodes themselves. 
     According to the present invention, in the ion elution unit constructed as described above, the interval between the electrodes is so set as to become narrower from the upstream side to the downstream side with respect to the water current flowing through the inside of the casing of the ion elution unit. With this construction, the interval between the electrodes is so tapered as to become increasingly narrow from the upstream to the downstream side. This permits the electrodes to lie along the water current, and thus, even when they wear and become thin, they are not prone to chatter or chip. Moreover, the electrodes are unlikely to be so heavily deformed as to cause short-circuiting therebetween. 
     According to the present invention, in the ion elution unit constructed as described above, terminals that are so laid as to run from the electrodes out of the casing of the ion elution unit are disposed on the upstream side with respect to the water current flowing through the inside of the casing, and a supporting portion for supporting the downstream-side parts of the electrodes is formed on the inner surface of the casing. With this construction, the electrodes are supported firmly both on the upstream and downstream sides, and thus do not vibrate in the water current. This makes the electrodes unlikely to break as a result of vibration. 
     According to the present invention, in the ion elution unit constructed as described above, a water inflow port and a water outflow port are formed in the casing of the ion elution unit, and the outflow port is given a smaller cross-sectional area than the inflow port. With this construction, the outflow port of the ion elution unit has a smaller cross-sectional area, and hence a higher flow passage resistance, than the inflow port thereof. Thus, the water that has entered the casing through the inflow port fills the interior of the casing without leaving a lump of stagnant air, and thus completely immerses the electrodes. This permits no part of the electrodes to be left uninvolved in the generation of metal ions and remain uneluted. 
     According to the present invention, in the ion elution unit constructed as described above, the cross-sectional area of the interior space of the casing gradually decreases from the upstream side to the downstream side. With this construction, not only is the cross-sectional area of the outflow port smaller than that of the inflow port, the cross-sectional area of the interior space of the casing gradually decreases from the upstream to the downstream side. This makes turbulent currents or air bubbles unlikely to form inside the casing, and thus ensures a smooth water current. The electrodes are less likely to remain uneluted under the cover of air bubbles. Metal ions quickly leave the electrodes, and do not return thereto, resulting in enhanced ion elution efficiency. 
     According to the present invention, in the ion elution unit constructed as described above, a water inflow port and a water outflow port are formed in the casing of the ion elution unit, and the water outflow port is located in the lowest position within the interior space of the casing. With this construction, since the outflow port is located in the lowest position within the interior space of the casing, when the supply of water to the ion elution unit is stopped, all the water inside it flows out of it through the outflow port. This prevents water remaining inside the casing from being frozen in cold weather and causing failure or destruction of the ion elution unit. 
     According to the present invention, in the ion elution unit constructed as described above, terminals that are so laid as to run from the electrodes out of the casing of the ion elution unit are formed in a position inward of the ends of the electrodes located on the upstream side with respect to the water current flowing through the inside of the casing. With this construction, the terminals are indeed upstream-side parts of the electrode but are not at the very ends thereof; that is, they are formed inward of the upstream-side ends of the electrode. This prevents the wear that has started at the ends of the electrodes from reaching the terminals and making them break at the bases thereof. 
     According to the present invention, in the ion elution unit constructed as described above, the terminals that are so laid as to run out of the casing of the ion elution unit are formed integrally with the electrodes. With this construction, since the electrodes and the terminals are formed integrally, as opposed to when separate metal components are joined together, no potential difference appears between the electrodes and the terminals, and thus no corrosion occurs there. Moreover, integrally forming these helps simplify the manufacturing process. 
     According to the present invention, in the ion elution unit constructed as described above, the terminals that are so laid as to run from the electrodes out of the casing of the ion elution unit have parts thereof located inside the casing protected with a sleeve made of an insulating material. With this construction, the parts of the terminals located inside the casing are protected with a sleeve made of an insulating material, and thus do not wear as a result of energization. This prevents the terminals from breaking in the middle of use. 
     According to the present invention, in the ion elution unit constructed as described above, the terminals laid from the electrodes are so formed as to penetrate the bottom wall of the case of the ion elution unit and protrude downward. With this construction, even when condensation occurs on the outer surface of the casing as a result of water vapor making contact with the casing or the casing being cooled as water is passed therethrough, the condensed water flows down along the cable connected to the terminals, and thus does not collect at the boundaries between the terminals and the casing. This prevents the terminals from being short-circuited by condensed water. 
     According to the present invention, in an ion elution unit as described above, an anode electrode is made of silver, copper, zinc or an alloy of silver and copper. With this construction, silver ions eluted from a silver electrode, copper ions eluted from a copper electrode and zinc ions eluted from a zinc electrode are exploited their excellent sterilizing effect, even on mold. 
     According to the present invention, in an ion elution unit as described above, both anode electrode and cathode electrode are made of silver, copper, zinc or an alloy of silver and copper. With this construction, silver ions eluted from a silver electrode, copper ions eluted from a copper electrode and zinc ions eluted from a zinc electrode are exploited their excellent sterilizing effect, even on mold. This effect is unchanged when the polarity of the electrodes is reversed. 
     According to the present invention, in an ion elution unit as described above, the polarity of the electrodes is reversed cyclically. With this construction, a problem that the surface of electrode is covered with a thick layer of scale deposited through the use of long period and current is subjected to be restricted, is avoidable. Also a problem of “one-sided depletion,” in which only one electrode being used as an anode is consumed at a rate faster than the other, is avoidable. 
     According to the present invention, an ion elution unit as described above is incorporated in an appliance so that the appliance uses water mixed with metal ions generated by the ion elution unit. With this construction, it is possible to use water mixed with metal ions generated by the ion elution unit. For example, if the appliance is a dish washing machine, it is possible to treat eating utensils with antimicrobial treatment using metal ions and thereby enhance hygiene. If the appliance is a humidifier, it is possible to prevent proliferation of bacteria and algae in the water stored in its water tank and thereby prevent bacteria and algae spores from being spread into the air and causing an infection or allergy in a person who inhaled them. 
     According to the present invention, in the appliance constructed as described above, the appliance is a washer. With this construction, it is possible to treat with antimicrobial treatment using metal ions and thereby prevent proliferation of bacteria and mold and generation of an offensive smell. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical sectional view of a washer embodying the present invention. 
         FIG. 2  is a schematic vertical sectional view of a water feed mouth. 
         FIG. 3  is a partial top view of an interior of the washer. 
         FIG. 4  is a top view of an ion elution unit. 
         FIG. 5  is a vertical sectional view taken along line A-A shown in  FIG. 4 . 
         FIG. 6  is a vertical sectional view taken along line B-B shown in  FIG. 4 . 
         FIG. 7  is a horizontal sectional view of the ion elution unit. 
         FIG. 8  is a perspective view of an electrode. 
         FIG. 9  is a circuit diagram of a drive circuit of the ion elution unit. 
         FIG. 10  is a flow chart of an entire session of laundry washing; 
         FIG. 11  is a flow chart of a washing process. 
         FIG. 12  is a flow chart of a rinsing process. 
         FIG. 13  is a flow chart of a squeezing process. 
         FIG. 14  is a flow chart of a final rinsing process. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will be described with reference to Figures. 
       FIG. 1  is a vertical sectional view showing the overall construction of a washer  1 . The washer  1  is of an automatic type, and has a cabinet  10 . The box-shaped cabinet  10  is formed of metal or synthetic resin, and has openings at its top and bottom. The top opening of the cabinet  10  is covered with a top plate  11 , which is formed of synthetic resin and is fixed to the cabinet  10  with screws. In  FIG. 1 , front and rear of the washer  1  point leftward and rightward, respectively. A rear portion of a top surface of the top plate  11  is covered with a back panel  12 , which is formed of synthetic resin and is fixed to the cabinet  10  or the top plate  11  with screws. The bottom opening of the cabinet  10  is covered with a base  13 , which is formed of synthetic resin and is fixed to the cabinet  10  with screws. None of the screws mentioned thus far are shown in the figure. 
     Feet  14   a  and  14   b  for supporting the cabinet  10  on a floor are disposed at the four corners of the base  13 . The rear feet  14   b  are fixed feet integrally formed with the base  13 . The front feet  14   a  are height-adjustable screw feet, and turning them levels the washer  1 . 
     The top plate  11  has a laundry inlet opening  15  through which laundry is put in a washing tub described later. The laundry inlet opening  15  is covered with a lid  16  from above. The lid  16  is coupled to the top plate  11  with a hinge  17  so as to be pivotable in a vertical plane. 
     A water tub  20  and a washing tub  30  that serves also as a squeezing tub are disposed inside the cabinet  10 . Both the water tub  20  and the washing tub  30  are shaped in a cylindrical cup open at its top, and the two tubs are arranged concentrically with their axes vertical and with the washing tub  30  placed inside the water tub  20 . The water tub  20  is suspended from the cabinet  10  with suspension members  21 . The suspension members  21  connect a lower outer surface of the water tub  20  to four inner corners of the cabinet  10 , and support the water tub  20  in such a way that it can swing in a horizontal plane. 
     The washing tub  30  has a circumferential wall that widens upward with a gentle taper. This circumferential wall has a plurality of drain holes  31  formed in a ring-shaped arrangement around its topmost portion, and has, other than these drain holes, no opening that permits passage of liquid. The washing tub  30  is of so-called “holeless” type. A ring-shaped balancer  32  is attached to a rim of the top opening of the washing tub  30  to suppress vibration produced by the washing tub  30  when it rotates at high speed for squeezing of laundry. Inside the washing tub  30 , on its bottom surface, a pulsator  33  is disposed to produce a current of washing or rinsing water inside the tub  30 . 
     The water tub  20  has a drive unit  40  fitted to its bottom surface from below. The drive unit  40  includes a motor  41 , a clutch mechanism  42 , and a brake mechanism  43 , and has a squeezing spindle  44  and a pulsator spindle  45  protruding from its center upward. The squeezing spindle  44  and the pulsator spindle  45  form a double-spindle structure, with the pulsator spindle  45  placed inside the squeezing spindle  44 . The two spindles both penetrate the water tub  20 . The squeezing spindle  44  is then connected to the washing tub  30  so as to support it. On the other hand, the pulsator spindle  45  further penetrates the washing tub  30 , and is then connected to the pulsator  33  to support it. Sealing members for preventing leakage of water are disposed between the squeezing spindle  44  and the water tub  20  and between the squeezing spindle  44  and the pulsator spindle  45 . 
     A water feed valve  50 , which is operated electro-magnetically, is disposed inside a space below the back panel  12 . The water feed valve  50  has a connection pipe  51  that penetrates the back panel  12  to extend upward. A water feed hose (not shown) through which to supply clean water such as tap water to the washer is connected to the connection pipe  51 . The water feed valve  50  feeds water to a water feed mouth  53  in a shape of container that is placed above the inside of the water tub  20 . The water feed mouth  53  has a structure as shown in  FIG. 2 . 
       FIG. 2  is a schematic vertical sectional view of the water feed mouth  53 . The water feed mouth  53  has an opening in its front, and through the opening, a drawer  53   a  is inserted. The drawer  53   a  has its interior divided into a plurality of sections (the embodiment of the present has two sections, that is, a left-hand section and a right-hand section). The left-hand section is a detergent chamber  54  that serves as a storage space for detergent. The right-hand section is a treatment agent chamber  55  that serves as a storage space for treatment agent for laundry washing. A bottom of the detergent chamber  54  is provided with a water outlet  54   a  which is open toward an inside of the water feed mouth  53 . A siphon  57  is disposed in the treatment agent chamber  55 . The water feed mouth  53  has, below the bottom of the drawer  53   a , a water outlet  56  through which water is fed into the washing tub  30 . 
     The siphon  57  is composed of an inner pipe  57   a  that extends vertically upward from a bottom surface of the treatment agent chamber  55  and a cap-shaped outer pipe  57   b  with which the inner pipe  57   a  is capped. Between the inner pipe  57   a  and the outer pipe  57   b  is left a gap that permits passage of water. The inner pipe  57   a , at its bottom, is open to a bottom of the water feed mouth  53 . A predetermined gap is kept between a bottom end of the outer pipe  57   b  and a bottom surface of the treatment agent chamber  55  so as to serve as a water inlet. When water is poured into the treatment agent chamber  55  up to a level higher than a top end of the inner pipe  57   a , a principle of siphon works to cause water to flow through the siphon  57  out of the treatment agent chamber  55  and then drop to the bottom of the water feed mouth  53 , water is then poured into the washing tub  30  through the water outlet  56 . 
     The water feed valve  50  is composed of a main water feed valve  50   a  and a sub water feed valve  50   b . The main water feed valve  50   a  allows relatively large flow of water, while the sub water feed valve  50   b  allows relatively small flow of water. Setting the flow of water large or small is achieved by making the internal structure of the main water feed valve  50   a  and that of the sub water feed valve  50   b  be different from each other, or by making the internal structures of both valves same and combining them with flow-limiting members having different throttling ratio. The connection pipe  51  is shared between the main and sub water feed valves  50   a  and  50   b.    
     The main water feed valve  50   a  is connected to an opening in a ceiling of the water feed mouth  53  by way of a main water feed passage  52   a . This opening is open toward the detergent chamber  54 , so that a large amount of water flow from the main water feed valve  50   a  is poured into the detergent chamber  54  through the main water feed passage  52   a . The sub water feed valve  50   b  is connected to the opening in the ceiling of the water feed mouth  53  by way of a sub water feed passage  52   b . This opening is open toward the treatment agent chamber  55 , so that a small amount of water flow from the sub water feed valve  50   b  is poured into the treatment agent chamber  55  through the sub water feed passage  52   b . That is, a passage that runs from the main water feed valve  50   a  through the detergent chamber  54  to the washing tub  30  is separate from a passage that runs from the sub water feed valve  50   b  through the treatment agent chamber  55  to the washing tub  30 . 
     Back in  FIG. 1 , to the bottom of the water tub  20  is fitted a drain hose  60  through which water is drained out of the water tub  20  and the washing tub  30 . Water flows into the drain hose  60  from drain pipes  61  and  62 . The drain pipe  61  is connected to a rather peripheral portion of the bottom surface of the water tub  20 , and the drain pipe  62  is connected to a rather central portion of the bottom surface of the water tub  20 . 
     Inside the water tub  20 , on its bottom surface, there is fixed a ring-shaped partition wall  63  in such a way as to enclose the portion of the water tub  20  where the drain pipe  62  is connected to it. The partition wall  63  is fitted with a circular sealing member  64  at its top. The sealing member  64  is kept in contact with a circumferential surface of a disk fixed to an outer bottom surface of the washing tub  30  so as to form a separate drain space  66  between the water tub  20  and the washing tub  30 . The drain space  66  communicates with an interior of the washing tub  30  through a drain outlet  67  formed in the bottom of the washing tub  30 . 
     The drain pipe  62  is provided with a drain valve  68  that is operated electro-magnetically. In a portion of the drain pipe  62 , on the upstream side of the drain valve  68 , an air trap  69  is disposed. A lead pipe  70  extends from the air trap  69 . The lead pipe  70  is, at its top end, connected to a water level switch  71 . 
     A controller  80  is disposed in a front portion of the cabinet  10 , beneath the top plate  11 . The controller  80  receives instructions from users via an operation/display panel  81  disposed on the top surface of the top plate  11 , and sends operation commands to the drive unit  40 , the water feed valve  50 , and the drain valve  68 . The controller  80  also sends display commands to the operation/display panel  81 . The controller  80  includes a drive circuit for driving an ion elution unit described later. 
     How the washer  1  operates will now be described. First, the lid  16  is opened, and laundry is put into the washing tub  30  through the laundry inlet opening  15 . The drawer  53   a  is pulled out from the water feed mouth  53  and a detergent is put in the detergent chamber  54  in the drawer  53   a . A treatment agent (softening agent) is put in the treatment agent chamber  55 . The treatment agent (softening agent) can be put there in the middle of a laundry washing session, or may not be put when unnecessary. After the detergent and the treatment agent (softening agent) are set, the drawer  53   a  is pushed back into the water feed mouth  53 . 
     After the detergent and the treatment agent (softening agent) are made ready for addition in this way, the lid  16  is closed, and a desired course of laundry washing is selected by operating a group of operation buttons on the operation/display panel  81 . By pressing a start button subsequently, a session of laundry washing is executed according to the flow charts shown in  FIGS. 10 through 13 . 
       FIG. 10  is a flow chart showing the entire session of laundry washing. In step S 201 , laundry washing is started at a previously set time. Whether a timer-started operation is selected or not is checked. If a timer-started operation is selected, the flow proceeds to step S 206 ; if not, the flow proceeds to step S 202 . 
     In step S 206 , whether the operation start time has come or not is checked. If the operation start time has come, the flow proceeds to step S 202 . 
     In step S 202 , whether a washing process is selected or not is checked. If a washing process is selected, the flow proceeds to S 300 . How the washing process in step S 300  is executed will be described later with reference to the flow chart shown in  FIG. 11 . On completion of the washing process, the flow proceeds to step S 203 . If no washing process is selected, the flow proceeds directly from step S 202  to step S 203 . 
     In step S 203 , whether a rinsing process is selected or not is checked. If a rinsing process is selected, the flow proceeds to S 400 . How the rinsing process in step S 400  is executed will be described later with reference to the flow chart shown in  FIG. 12 . In  FIG. 10 , the rinsing process is repeated three times, and each step of the process is shown with a step number with a suffix number added such as “S 400 - 1 ,” “S 400 - 2 ” and “S 400 - 3 .” The number of times of the rinsing process is set at users&#39; discretion. In this case, “S 400 - 3 ” is a final rinsing process. 
     On completion of the rinsing process, the flow proceeds to step S 204 . If no rinsing process is selected, the flow proceeds directly from step S 203  to step S 204 . 
     In step S 204 , whether a squeezing process is selected or not is checked. If a squeezing process is selected, the flow proceeds to S 500 . How the squeezing process in step S 500  is executed will be described later with reference to the flow chart shown in  FIG. 13 . On completion of the squeezing process, the flow proceeds to step S 205 . If no squeezing process is selected, the flow proceeds directly from step S 204  to step S 205 . 
     In step S 205 , termination of operation of the controller  80 , in particular a processing unit (microcomputer) therein, is automatically executed in accordance with a predetermined procedure. In addition, the completion of laundry washing session is indicated by sounding an operation-completion beep. On completion of all the operations, the washer  1  goes back into a stand-by state in preparation for a new session of laundry washing. 
     Next, with reference to  FIGS. 11 through 13 , the individual processes of washing, rinsing, and squeezing will be described. 
       FIG. 11  is a flow chart of the washing process. In step S 301 , the water level inside the washing tub  30  as sensed by the water level switch  71  starts being monitored. In step S 302 , whether laundry amount sensing is selected or not is checked. If laundry amount sensing is selected, the flow proceeds to step S 308 ; if not, the flow proceeds directly from step S 302  to S 303 . 
     In step S 308 , the amount of laundry is measured on the basis of load of rotation of the pulsator  33 . On completion of laundry amount sensing, the flow proceeds to step S 303 . 
     In step S 303 , the main water feed valve  50   a  is opened, and water is poured into the washing tub  30  through the water feed mouth  53 . The detergent agent put into the detergent chamber  54  is mixed with water, and enters the washing tub  30 . The drain valve  68  remains closed. When the water level switch  71  detects the set water level, the main water feed valve  50   a  is closed. The flow then proceeds to step S 304 . 
     In step S 304 , a preparatory operation is performed. The pulsator  33  is rotated repeatedly in forward and then reverse directions to agitate the laundry and water so that the laundry is fully dipped in water. This permits the laundry to absorb an ample amount of water, and permits air trapped in many parts of the laundry to escape. If, as a result of the preparatory operation, the water level as detected by the water level switch  71  becomes lower than at the beginning, then, in step S 305 , the main water feed valve  50   a  is opened to supply additional water to recover the set water level. 
     If a course of laundry washing including “cloth type sensing” is selected, when the preparatory operation is performed, the type of cloth is sensed. On completion of the preparatory operation, the change of the water level from the set water level is detected, and, if the drop in the water level is greater than a predetermined amount, the laundry is judged to be of the highly water-absorbent cloth type. 
     When, in step S 305 , the set water level is stably obtained, the flow proceeds to step S 306 . According to the settings made by users, the motor  41  rotates the pulsator  33  in a predetermined pattern so as to produce, in the washing tub  30 , a main current of water for washing. With this main current of water, the laundry is washed. The squeezing spindle  44  remains braked by the brake mechanism  43  so that, even when the washing water and the laundry move, the washing tub  30  does not rotate. 
     On completion of the period in which the laundry is washed with the main current of water, the flow proceeds to step S 307 . In step S 307 , the pulsator  33  is rotated repeatedly in the forward and then reverse directions at short time intervals. This permits the laundry to loosen, and thereby permits it to spread evenly in the washing tub  30 . This is done in preparation for squeezing rotation of the washing tub  30 . 
     Next, with reference to the flow chart shown in  FIG. 12 , the rinsing process will be described. First, in step S 500 , the squeezing process is executed, of which a description will be given later with reference to the flow chart shown in  FIG. 13 . On completion of squeezing, the flow proceeds to step S 401 . In step S 401 , the main water feed valve  50   a  is opened, and water is supplied up to the set water level. 
     On completion of the supply of water, the flow proceeds to step S 402 . In step S 402 , a preparatory operation is performed. During the preparatory operation performed in step S 402 , laundry getting attached to the washing tub  30  in step S 500  (squeezing process) is separated, soaked into water so that the laundry thoroughly absorbs water. 
     On completion of the preparatory operation, the flow proceeds to step S 403 . If, as a result of the preparatory operation, the water level as detected by the water level switch  71  becomes lower than at the beginning, the main water feed valve  50   a  is opened to supply additional water to recover the set water level. 
     After recovering the set water level in step S 403 , the flow then proceeds to step S 404 . According to the settings made by users, the motor  41  rotates the pulsator  33  in a predetermined pattern so as to produce, in the washing tub  30 , a main current of water for rinsing. With this main current of water, the laundry is rinsed. The squeezing spindle  44  remains braked by the brake mechanism  43  so that, even when the rinsing water and the laundry move, the washing tub  30  does not rotate. 
     On completion of the period in which the laundry is rinsed with the main current of water, the flow proceeds to step S 406 . In step S 406 , the pulsator  33  is rotated repeatedly in the forward and then reverse directions at short time intervals. This permits the laundry to loosen, and thereby permits it to spread evenly in the washing tub  30 . This is done in preparation for squeezing rotation. 
     In the above description, rinsing is assumed to be performed with rinsing water stored in the washing tub  30 . This is called “rinsing with stored water.” It is, however, also possible to perform rinsing with always replenishing fresh water, which is called “rinsing with pouring water,” or to perform rinsing with water kept supplied from the water feed mouth  53  while the washing tub  30  is rotated at a low speed, which is called “shower rinsing.” 
     In the final rinsing process, different sequence from the above is executed. This will be described in details later. 
     Next, with reference to the flow chart shown in  FIG. 13 , the squeezing process will be described. First, in step S 501 , the drain valve  68  is opened. The washing water in the washing tub  30  is drained through the drain space  66 . The drain valve  68  remains open during the squeezing process. 
     When most of the washing water has exited from the laundry, the clutch mechanism  42  and the brake mechanism  43  are switched over. The timing for switching over of the clutch mechanism  42  and the brake mechanism  43  is either before or at the same time of starting of draining of water. The motor  41  now rotates the squeezing spindle  44 . This causes the washing tub  30  to start squeezing rotation. The pulsator  33  rotates together with the washing tub  30 . 
     When the washing tub  30  rotates at a high speed, the laundry is pressed against the inner circumferential wall of the washing tub  30  by the centrifugal force. The washing water present in the laundry also gathers on the inner surface of the circumferential wall of the washing tub  30 , and, since the washing tub  30  widens upward in a tapered shape as described earlier, the washing water driven by the centrifugal force rises along the inner surface of the washing tub  30 . When the washing water reaches the top end of the washing tub  30 , it is drained through the drain holes  31 . The washing water that has exited from the drain holes  31  hits the inner surface of the water tub  20 , and then flows down along the inner surface of the water tub  20  to the bottom of the water tub  20 . The washing water is then drained out of the cabinet  10  through the drain pipe  61  and then through the drain hose  60 . 
     In the flow shown in  FIG. 13 , after squeezing is performed at a relatively low speed in step S 502 , squeezing is performed at high speed in step S 503 . On completion of step S 503 , the flow proceeds to step S 504 . In step S 504 , the supply of electric power to the motor  41  is stopped and termination operation is done for stopping. 
     The washer  1  is furnished with an ion elution unit  100 . The ion elution unit  100  is connected to the downstream side of the main water feed pipe  52   a . Now, with reference to  FIGS. 3 through 9 , the structure and functions of the ion elution unit  100  and the purpose for which it is incorporated in the washer  1  will be described. 
       FIG. 3  is a partial top view indicating the layout of the ion elution unit  100  and the water feed mouth  53 . The ion elution unit  100  is connected directly to the main water feed valve  50   a  and the water feed mouth  53  on both ends. In other words, the ion elution unit  100  independently composes the entire main water feed passage  52   a . The sub water feed passage  52   b  is constructed by connecting the pipe, which protrudes from the water feed mouth  53 , to the sub water feed valve  50   b  with a hose. In the schematic view of  FIG. 1 , the water feed valve  50 , the ion elution unit  100  and the water feed mouth  53  are arranged in line with front-to-rear axis of the washer  1 . However, in an actual washer, they are not arranged in that way but arranged in line with left-to-right axis of the washer  1 . 
       FIG. 4  through  FIG. 8  shows the structure of the ion elution unit.  FIG. 4  is a top view.  FIG. 5  is a vertical sectional view taken along line A-A shown in  FIG. 4 .  FIG. 6  is also a vertical sectional view taken along line B-B shown in  FIG. 4 .  FIG. 7  is a horizontal sectional view.  FIG. 8  is a perspective view of an electrode. 
     The ion elution unit  100  has a casing  110  formed of transparent or translucent, colorless or colored synthetic resin or opaque synthetic resin. The casing  110  is composed of a casing body  110   a  having an opening at the top and a lid  110   b  which closes the opening at the top. (See  FIG. 5 .) The casing  110   a  is shaped as long and narrow, containing a water inlet  111  at one end of the longitudinal direction and a water outlet  112  at the other end. The water inlet  111  and the water outlet  112  are pipe-shaped. Cross-sectional area of the water outlet  112  is smaller than that of the water inlet  111 . 
     The casing  110  is arranged with its longitudinal direction being horizontal. The casing body  110   a  arranged horizontally in this way has a bottom that inclines gradually toward the water outlet  112 . (See  FIG. 5 .) In other words, the water outlet  112  is located at the lowest level in an internal space of the casing  110 . 
     The lid  110   b  is fixed to the casing body  110   a  with four screws  170 . (See  FIG. 4 .) A seal ring  171  is inserted between the casing body  110   a  and the lid  110   b . (See  FIG. 5 .) 
     Inside the casing  110 , two plate electrodes  113  and  114  are arranged so as to be parallel to the water current flowing from the water inlet  111  toward the water outlet  112 , facing each other. When a predetermined voltage is applied to the electrodes  113  and  114  with the casing  110  filled with water, metal ions of the metal of which the electrodes  113  and  114  are formed are eluted from whichever of them is at the anode side at the moment. For an example, the electrodes  113  and  114  may be so constructed that plates of silver each measuring 2 cm×5 cm and about 1 mm thick are arranged about 5 mm apart from each other. 
     Material of the electrodes  113  and  114  is not limited to silver. Any metal can be the material as long as it is a source for antimicrobial metal ions. Other than silver, copper, an alloy of silver and copper, zinc or the like can be selected. Silver ions eluted from a silver electrode, copper ions eluted from a copper electrode and zinc ions eluted from a zinc electrode show an excellent sterilizing effect, even on mold. From an alloy of silver and copper, silver and copper ions can be eluted simultaneously. 
     As for the ion elution unit  100 , it is possible to select either elution or non-elution by whether a voltage is applied or not. Moreover, an amount of elution of metal ions can be controlled by controlling electric current or the time for applying a voltage. Compared with a method of eluting metal ions from zeolite or other metal ion carriers, it is convenient because it is possible to electrically select whether the metal ions are added or not and to electrically adjust the concentration of the metal ions. 
     The electrodes  113  and  114  are not arranged completely in parallel. In the plane view, they are arranged to be tapered, having the space between them becomes narrower from the upstream toward the downstream along the water current flowing through the inside of the casing  110 , in other words, from the water inlet  111  toward the water outlet  112 . (See  FIG. 7 .) 
     The plan-view shape of the casing body  110   a  is also narrowed from one end having the water inlet  111  to the other end having the water outlet  112 . Namely, the cross-sectional area in the internal space of the casing  110  gradually decreases from the upstream side toward the downstream side. 
     The electrodes  113  and  114  have both rectangular profile, and terminals  115  and  116  are provided thereto respectively. The terminals  115  and  116  are disposed at portions inside of the edges of the electrodes  113  and  114  on the upstream side, hanging down from the lower edge of the electrodes  113  and  114  respectively. 
     The electrode  113  and the terminal  115  are formed integrally from the same metal, and the electrode  114  and the terminal  116  are formed integrally from the same metal. The electrodes  115  and  116  are led to the bottom of the casing body  110   a  through a hole formed in a bottom wall of the casing body  110   a . Where the terminals  115  and  116  protrude out of the casing  110   a , as shown in an enlarged figure in  FIG. 6 , a watertight seal  172  is installed. The watertight seal  172  forms a double sealing construction together with a second sleeve  175  described later so as to prevent water from leaking from this portion. 
     At the bottom of the casing  110   a , an insulating wall  173 , which isolates the terminals  115  and  116 , is integrally formed. (See  FIG. 6 .) The terminals  115  and  116  are connected to a drive circuit within the controller  80  by way of a cable (not shown). 
     Of the terminals  115  and  116 , portions remaining in the casing  110  are protected by a sleeve made of insulation material. Two types of sleeves are used. One sleeve  174  is made of synthetic resin and engaged into the roots of the terminals  115  and  116 . A part of the first sleeve  174  spreads to one side of the electrodes  113  and  114 , forming projections on the side of these portions and fitting these projections to the through holes made in the electrodes  113  and  114 . This helps prevent the electrodes  113  and  114  from coming out of the sleeve  174 . The second sleeve  175  is made of soft rubber and fills the gap between the first sleeve  174  and the bottom wall of the casing body  110   a , thus preventing water from leaking through the gap between the second sleeve  175  and the casing body  110   a  and through the gaps between the second sleeve  175  and the electrodes  113  and  114 . 
     As mentioned above, the terminals  115  and  116  are located on the upstream side of the electrodes  113  and  114 . The upstream sides of the electrodes  113  and  114  are supported by the first sleeve  174 , which is engaged to the terminals  115  and  116 . On the inner surface of the lid  110   b , a support  176  in a shape of a fork is formed so as to fit to the position of the first sleeve  174 . (See  FIG. 6 .) This support  176  catches the upper edge of the first sleeve  174  and becomes a rigid support, together with the second sleeve  175  filling the gap between the first sleeve  174  and the casing body  110   a . The fork-shaped support  176  catches the electrodes  113  and  114  with long and short fingers, by which the electrodes  113  and  114  can maintain an appropriate space between each other on the side of the lid  110   b.    
     The downstream sides of the electrodes  113  and  114  are also supported by the support formed on the inner surface of the casing  110 . A fork-shaped support  177  rises from the bottom surface of the casing body  110   a . Also, a fork-shaped support  178  hangs down from the ceiling of the lid  110   b  to face the support  177 . (See  FIGS. 5 and 8 .) The electrodes  113  and  114  are caught by the supports  177  and  178  at the lower and upper edges on the downstream side respectively so as not to move. 
     As shown in  FIG. 7 , the electrodes  113  and  114  are so arranged that the surfaces opposite to the surfaces that are facing each other keep a space from the inner surface of the casing  110 . Moreover, as shown in  FIG. 5 , the electrodes  113  and  114  are so arranged as to keep a space between their upper and lower edges and the inner surface of the casing  110 . (Portions which are in contact with the supports  176 ,  177  and  178  are exceptions.) Additionally, as shown in either of  FIG. 7  and  FIG. 5 , a space is made between the upstream and downstream side edges of the electrodes  113  and  114  and the inner surface of the casing  110 . 
     When it is necessary to make the width of the casing  110  much smaller, it is possible to construct the electrodes  113  and  114  in such a manner that the surfaces opposite to the surfaces that are facing each other are attached firmly to the inner wall of the casing  110 . 
     In order to prevent foreign objects from getting contact with the electrodes  113  and  114 , a strainer of a metal mesh is mounted on the upstream side of the electrodes  113  and  114 . As shown in  FIG. 2 , a strainer  180  is placed in the connection pipe  51 . The strainer  180  is for the purpose of preventing foreign objects from intruding into the water feed valve  50 , and it also serves as an upstream strainer of the ion elution unit  100 . 
     A strainer of a metal mesh  181  is mounted to the downstream side of the electrodes  113  and  114 . The strainer  181  prevents broken pieces of the electrodes  113  and  114  from flowing out when they are thinned out and broken due to being used for a long time. The water outlet  112  can be selected as a site for mounting the strainer  181 , for example. 
     The locations of the strainers  180  and  181  are not limited to the above. As long as the conditions of mounting on “the upstream side of the electrode” and on “the downstream side of the electrode” are satisfied, they can be placed at any location in the water feed passage. The strainers  180  and  181  are removable so that foreign objects they catch can be removed or substances contributing to clogging can be cleared of. 
       FIG. 9  shows the drive circuit  120  for the ion elution unit  100 . A transformer  122  is connected to commercially distributed electric power  121  so as to step down 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 formed into a constant voltage by a constant voltage circuit  124 . To the constant voltage circuit  124  is connected a constant current circuit  125 . The constant current circuit  125  operates in such a way as to supply a constant current to the electrode drive circuit  150  described later without being influenced by variation in the resistance through the electrode drive circuit  150 . 
     To the commercially distributed electric power  121  is also connected, in parallel with the transformer  122 , a rectifying diode  126 . The output voltage of the rectifying diode  126  is smoothed by a capacitor  127 , is then formed 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 commercially distributed electric power  121 . 
     The electrode drive circuit  150  is composed of NPN-type transistors Q 1  to Q 4 , diodes D 1  and D 2 , and resistors R 1  to R 7 . These 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 . The diodes D 1  and D 2  are photodiodes, and the transistors Q 1  and Q 2  are phototransistors. 
     The microcomputer  130  feeds a high-level voltage to a line L 1  and a low-level voltage (or zero voltage, namely, “off”) to a line L 2 . Then, the diode D 2  turns on, and this causes the transistor Q 2  to turn on. When the transistor Q 2  turns on, a 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 . Thus, the transistor Q 3  turns on. 
     On the other hand, the diode D 1  is off, and thus the transistors Q 1  is off, and accordingly the transistor Q 4  is off. In this state, a current flows from the anode-side electrode  113  to the cathode-side electrode  114 . As a result, in the ion elution unit  100 , there are produced metal ions as positively-charged ions together with negatively-charged ions. 
     When an electric current is passed through the ion elution unit  100  in one direction for a long time, the electrode  113 , which is at the anode side in  FIG. 9 , wears off, while the electrode  114 , which is at the cathode side, collects impurities in water in the form of scales deposited on it. This degrades the performance of the ion elution unit  100 . In order to avoid this, the electrode drive circuit  150  can be operated in a compulsory electrode-cleaning mode. 
     In the compulsory electrode-cleaning mode, the microcomputer  130  switches modes of control so as to invert the voltage applied between the lines L 1  and L 2  and thereby reverse the current that flows between the electrodes  113  and  114 . In this mode, 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 capability, and switches modes of control as described above every time a predetermined count is reached. 
     When the resistance through the electrode drive circuit  150 , in particular, the resistance of the electrodes  113  and  114 , varies and as a result, for example, the current that flows between the electrodes decreases, the constant current circuit  125  raises its output voltage to compensate for the decrease. However, as the total time of use increases, the ion elution unit  100  eventually reaches the end of its service life. When this happens, even if the mode of control is switched to the forcible electrode cleaning mode, or if the output voltage of the constant current circuit  125  is raised, it is no longer possible to compensate for the decrease in the current. 
     In order to cope with this, in the circuit under discussion, the current that flows between the electrodes  113  and  114  of the ion elution unit  100  is monitored on the basis of the voltage that it produces across the resistor R 7 . When the current becomes equal to a predetermined minimum current, a current detection circuit  160  detects it. The fact that the minimum current has been detected is transmitted from a photodiode D 3 , which is a part of a photocoupler  163 , through a phototransistor Q 5  to the microcomputer  130 . The microcomputer  130  then drives, by way of a line L 3 , a warning indicator  131  to make it indicate a predetermined warning. The warning indicator  131  is provided in the operation/display panel  81  or in the controller  80 . 
     Moreover, in order to cope with a fault such as short-circuiting within the electrode drive circuit  150 , there is provided a current detection circuit  161  that detects the current being larger than a predetermined maximum current. On the basis of the output of this current detection circuit  161 , the microcomputer  130  drives the warning indicator  131 . Furthermore, when the output voltage of the constant current circuit  125  becomes lower than a previously set minimum voltage, a voltage detection circuit  162  detects it, and the microcomputer  130  likewise drives the warning indicator  131 . 
     The metal ions generated by the ion elution unit  100  are poured into the washing tub in the following manner. 
     Metal ions and a softening agent to be used as a treatment agent are added in the final rinsing process.  FIG. 14  is a flow chart showing the sequence of the final rinsing. In the final rinsing process, after the squeezing process of step S 500 , the flow proceeds to step S 420 . In step  420 , whether addition of the treatment material is selected or not is checked. When “addition of a treatment agent” is selected through a selection operation performed by way of the operation/display panel  81 , the flow proceeds to step S 421 . If not, the flow proceeds to step S 401  in  FIG. 12 , and the final rinsing is executed in the same manner as in the previous rinsing processes. 
     In step S 421 , whether the treatment materials to be added are two types, that is metal ions and a softening agent, or not, is checked. When “metal ions and a softening agent” is selected through a selection operation performed by way of the operation/display panel  81 , the flow proceeds to step S 422 ; if not, the flow proceeds to step S 426 . 
     In step S 422 , both of the main water feed valve  50   a  and the sub water feed valve  50   b  are opened, and water flows into both of the main water feed passage  52   a  and the sub water feed passage  52   b.    
     Step S 422  is a process for elution of metal ions. A predetermined amount of water, which is set to be more than the volume of water set for the sub water feed valve  50   b , is flowing, filling the internal space of the ion elution unit  100 . Simultaneously, the drive circuit  120  applies a voltage between the electrodes  113  and  114 , so that ions of the metal of which they are formed are eluted into the water. When the metal forming the electrodes  113  and  114  is silver, reaction of Ag→Ag + +e −  occurs on the anode side and silver ions Ag +  are eluted into the water. The electric current flowing between the electrodes  113  and  114  is direct current. Water to which the metal ions are added flows into the detergent chamber  54  and then is poured into the washing tub  30  from the water outlet  54   a  by way of the water outlet  56 . 
     From the sub water feed valve  50   b , smaller amount of water than that from the main water feed valve  50   a  flows out and is poured into the treatment agent chamber  55  by way of the sub water feed passage  52   b . If a treatment agent (softening agent) has been supplied into the treatment agent chamber  55 , the treatment agent (softening agent) is fed into the washing tub  30  through the siphon  57  together with water. This addition is performed simultaneously when the metal ions are added. The effect of a siphon does not occur until the water level inside the treatment agent chamber  55  reaches a predetermined level. This permits the liquid treatment agent (softening agent) to be held in the treatment agent chamber  55  until the time comes when water is poured into the treatment agent chamber  55 . 
     When a predetermined amount of water (so much as or more than the amount to cause the effect of a siphon to occur in the siphon  57 ) is poured into the treatment agent chamber  55 , the sub water feed valve  50   b  is closed. This step of feeding water, namely, adding a treatment agent, is performed automatically, irrespective of whether or not a treatment agent (softening agent) has been put into the treatment agent chamber  55  so long as “addition of a treatment agent” is selected. 
     When a predetermined amount of water containing metal ions has been poured into the washing tub  30 , and the concentration of metal ions in the rinsing water is expected to be a predetermined level when water containing no metal ions is fed to the set water level, the application of a voltage between the electrodes  113  and  114  is stopped. After the ion elution unit  100  stops generation of metal ions, the main water feed valve  50   a  continues supplying water and stops water supply when the water level in the washing tub  30  reaches the set level. 
     As described above, in step S 422 , metal ions and a treatment agent (softening agent) are added simultaneously. However, this does not necessarily mean that the time during which a treatment agent (softening agent) is poured into the washing tub through an effect of a siphon completely overlaps the time while the ion elution unit  100  is generating metal ions. Either of the above time may be shifted to be earlier or later than the other. After the ion elution unit  100  stops generation of the metal ions and while water containing no metal ions is additionally fed, the treatment agent (softening agent) may be added. The point is that it is sufficient so long as the addition of metal ions and the addition of a treatment agent (softening agent) are executed respectively in one sequence. 
     As described before, the terminal  115  is formed to the electrode  113  integrally and the terminal  116  is formed to the electrode  114  integrally, from the same metal. Therefore, different from a case where different metals are connected, potential difference does not occur between the electrodes and terminals, thus preventing corrosion from occurring. Additionally, being formed integrally simplifies the manufacturing process. 
     The space between the electrodes  113  and  114  is set to be in a tapered manner, becoming narrower from the upstream side toward the downstream side. This makes the electrodes  113  and  114  be in line with the flow, and the electrodes  113  and  114  are more likely not generating vibration, thereby even when they wear off and are thinned, they hardly are chipped off. Moreover, there is no concern for excessive deformation of electrodes that might result in a short circuit. 
     The electrodes  113  and  114  are supported in a manner that a space is made between them and the inner surface of the casing  110 . This helps prevent a metal layer from growing from the electrodes  113  and  114  to the inner surface of the casing  110  and causing a short circuit between electrodes. 
     Although the terminals  115  and  116  are formed integrally to the electrodes  113  and  114  respectively, the electrodes  113  and  114  are eventually depleted as a result of use. However, the terminals  115  and  116  should be kept from depletion. In an embodiment of the present, the portions of the terminals  115  and  116  located inside the casing  110  are protected by the sleeves  174  and  175  made of insulating material, and are guarded from depletion caused by electric conduction. This helps prevent such situation as the terminals  115  and  116  are broken in midway of their use. 
     In the electrodes  113  and  114 , the portions where the terminals  115  and  116  are formed are rather deep inside from the edge on the upstream side. The electrodes  113  and  114  wear off, starting at a portion where the space between them has become narrow. In general, depletion occurs at the edge portion. Although the terminals  115  and  116  are located in the upstream side of the electrodes  113  and  114 , they are not completely at the edges, but at rather deep inside portions from the edges. Therefore, it is not necessary to be worried about a situation that the depletion starting at the edge of an electrode reaches the terminal to cause a breakage of the terminal at its root. 
     The electrodes  113  and  114  are supported by the first sleeve  174  and the support  176  on their upstream sides. On the other hand, the downstream sides of the electrodes  113  and  114  are supported by the supports  177  and  178 . Since they are supported rigidly on both upstream side and downstream sides in this way, the electrodes  113  and  114  do not vibrate although they are in the water current. As a result, the electrodes  113  and  114  do not get broken due to vibration. 
     The terminals  115  and  116  go through the bottom wall of the casing body  110   a  to be protruded downward. Therefore, although the external surface of the casing  110  is subjected to dew concentration because steam gets contact with the casing  110   a  (When warm water in a bath tub is used for washing, stream is easy to intrude into the interior of the washer  1 .) or because the casing  110  is cooled by feeding of water, the water from dew condensation flows down the cables connected to the terminals  115  and  116  and do not stay on the border between the terminals  115  and  116  and the casing  110 . Therefore, no situation is developed in which a short circuit occurs between the terminals  115  and  116  due to the water caused by dew condensation. The casing body  110   a  is arranged with the longitudinal direction on the horizontal line, it is easy to make it constructed in a manner that the terminals  115  and  116  formed on the sides of the electrodes  113  and  114  protrude downward through the bottom wall of the casing body  110   a.    
     The cross-sectional area of the water outlet  112  of the ion elution unit  100  is smaller than that of the water inlet  111  and has larger resistance to the flow than the water inlet  111 . This makes water entering the casing  110  through the water inlet  111  fill the interior of the casing  110  without causing stagnant air and soak the electrodes  113  and  114  completely. Therefore, such situation as the electrodes  113  and  114  have portions that are unrelated to the generation of metal ions but remain un-melted does not occur. 
     Not only the cross-sectional area of the water outlet  112  is smaller than that of the water inlet  111  but also the cross-sectional area of the inner space of the casing  110  is gradually decreasing from the upstream side toward the downstream side. This makes generation of turbulence or air bubble inside the casing  110  be reduced, thereby making water flow smoothly. Also, this prevents the electrodes partially not melted by the existence of air bubble. The metal ions come off the electrodes  113  and  114  quickly and do not go back to the electrodes  113  and  114 , thus increasing the efficiency of ion elution. 
     The ion elution unit  100  is arranged in the main water feed passage  52   a  for a large volume of flow where a large amount of water flows. This permits the metal ions to be carried out of the casing  110  quickly and prevents them from going back to the electrodes  113  and  114 , thus increasing the efficiency of ion elution. 
     The water outlet  112  is placed at the lowest level in the inner space of the casing  110 . Therefore, when feeding of water to the ion elution unit  100  is stopped, all the water in the ion elution unit  100  flows out through the water outlet  112 . In consequence, no such a case occurs as water remaining in the casing  110  is frozen at a cold time and the ion elution unit  100  fails or breaks. 
     A strainer  180  is placed on the upstream side of the electrodes  113  and  114 . This makes it possible that although solid foreign object exists in water fed to the ion elution unit  100 , the foreign object is caught by the strainer  180 , which prevents it from reaching the electrodes  113  and  114 . Consequently, a foreign object does not damage the electrodes  113  and  114 , nor cause a short circuit between the electrodes to cause an excessive electric current or to lead to metal ion generation shortage. 
     A strainer  181  is placed on the downstream sides of the electrodes  113  and  114 . If the electrodes  113  and  114  are depleted and become fragile due to a long-time use and get broken into pieces and the broken pieces flow, the strainer  181  catches these broken pieces so as to prevent them from flowing toward the downstream from that point. As a result, broken pieces of the electrodes  113  and  114  do not damage an object on the downstream side. 
     As the embodiment of the present invention, when a washer  1  is furnished with the ion elution unit  100 , foreign objects or broken pieces of electrodes may be attached to laundry if there are no strainers  180  and  181 . There is a possibility that foreign objects or broken pieces of electrodes may spoil or damage laundry, and if laundry where foreign objects or broken pieces of electrodes remain attached is subjected to squeezing and drying, a person who wears the laundry later may touch them and feel uncomfortable or in the worst case, he may get hurt. However, installation of the strainers  180  and  181  can avoid such a situation. 
     Both of the strainers  180  and  181  do not have to be placed. When it is determined that no installation of a strainer causes a problem, one or both of them can be abolished. 
     Back in  FIG. 14 , in step S 423 , the rinsing water to which the metal ions and the treatment agent (softening agent) are added is agitated by a powerful water flow (powerful swirl) and thus promotes contact of the laundry with the metal ions and attachment of the treatment agent (softening agent) to the laundry. 
     By thoroughly agitating by the powerful swirl, the metal ions and the treatment agent (softening agent) can be melted uniformly in water and spread to every corner of the laundry. After agitation by the powerful swirl for a predetermined time, the flow proceeds to step S 424 . 
     In step S 424 , the situation is completely changed. Agitation is executed by weak water flow (mild swirl). Its aimed purpose is to make the metal ions attached to the surface of laundry to exert their effect. As long as there is a water flow although it is mild, there is no possibility of users&#39; misunderstanding that the operation of the washer  1  has been over. Therefore, agitation is executed mildly. However, if there is a method to make users realize that the rinsing process is still in progress, for example, by displaying an indication on the operation/display panel  81  to evocate the users&#39; attention, it is permissible to stop agitation and place the water at a standstill. 
     After a period of mild swirl, which is set to be sufficient for laundry to absorb the metal ions, the flow proceeds to step S 425 . Here, agitation for ensuring is executed again with using a powerful water flow (powerful swirl). This helps distribute the metal ions to the portions of laundry where the metal ions have not been spread and make them attached firmly. 
     After step S 425 , the flow proceeds to step S 406 . In step S 406 , the pulsator  33  rotates repeatedly in the forward and then reverse directions at short time intervals. This permits the laundry to loosen, and thereby permits it to spread evenly in the washing tub  30 . This is done in preparation for squeezing rotation. 
     An example is given to show the distribution of time for each step: four minutes for step S 423  (powerful swirl); four minutes and fifteen seconds for step S 424  (mild swirl), five seconds for step S 425  (powerful swirl) and one minute and forty seconds for step S 406  (even spreading of laundry). Total time from step S 423  to step  406  is ten minutes. 
     Basically, it is preferable to add metal ions and a treatment agent (softening agent) separately. This is because when the metal ions come to contact with a component of the softening agent, they change into chemical compounds, thus losing the antimicrobial effect of the metal ions. However, quite an amount of metal ions remain in the rinsing water till the last of rinsing process. Also, the loss of the effect of the metal ions can be compensated to a certain degree by setting the concentration of the metal ions appropriately. Therefore, by adding the metal ions and the treating agent (softening agent) simultaneously, the rinsing time is shortened compared with the case that the metal ions and the treating agent (softening agent) are separately added for separate processes of rinsing, leading to the promotion of household efficiency, although the efficacy of addition of resistance to microbes is reduced slightly. 
     Although it is inevitable that the metal ions and the treatment agent (softening agent) meet in the washing tub  30 , it is desirable to prevent them from getting in contact with each other until they enter the washing tub  30 . In the embodiment of the present invention, metal ions are added to the washing tub  30  from the main water feed passage  52   a  through the detergent chamber  54 . The treatment agent (softening agent) is added to the washing tub  30  from the treatment agent chamber  55 . Since the passage for adding the metal ions to the rinsing water is thus separated from the passage for adding the treatment agent to the rinsing water, the metal ions and the treatment agent (softening agent) do not get in contact with each other until they meet in the washing tub  30 . Consequently, the metal ions do not change into chemical components by getting contact with the treatment agent (softening agent) of high concentration and lose their antimicrobial effect. 
     In the description, the final rinsing is assumed to be performed with rinsing water stored in the washing tub  30 . However, it is also possible to perform the final rinsing by water being poured, namely, in the manner of “rinsing with pouring water.” In this case, the poured water contains metal ions. 
     If the laundry does not spread evenly in step S 406  and water is poured again for “rinsing for correcting uneven spreading of laundry,” metal ions are added to the water. 
     Either of the addition of the metal ions, the first treatment substance, and the addition of a treatment agent (softening agent), the second treatment substance, is optional. It is possible not to carry out either of the additions or both of the additions. When both additions are not to be executed, the flow proceeds from step S 420  to step S 401 , and this has already been described. From now on, addition of either of the two types of treatment substances will be described. 
     In step S 421 , when the treatment substance to be added is not both of the two types, the metal ions and the softening agent, it means that only one of them is selected for addition. In this case, the flow proceeds to step S 426 . 
     In step S 426 , whether the treatment substance to be added is metal ion or not is checked. When it is determined to be metal ions, the flow proceeds to step S 427 ; if not, the flow proceeds to step S 428 . 
     In step S 427 , the main water feed valve  50   a  is opened and water flows into the main water feed passage  52   a . The sub water feed valve  50   b  is not opened. When water flows through the ion elution unit  100 , the drive circuit  120  applies a voltage between the electrodes  113  and  114 , which elutes ions of the metal composing the electrodes into the water. When it is determined that a predetermined amount of water containing metal ions has been poured into the washing tub  30 , and a predetermined concentration of metal ions in the rinsing water can be obtained by adding water containing no metal to a set water level, application of a voltage to the electrodes  113  and  114  is stopped. After the ion elution unit  100  stops generation of the metal ions, the main water feed valve  50   a  continues to feed water until the water level inside the washing tub  30  reaches the set level. 
     After step S 427 , the flow proceeds to step S 423 . After that, in the same manner as when the metal ions and the treatment agent (softening agent) are added simultaneously, the flow proceeds from S 423  (powerful swirl) to step S 424  (mild swirl) and then to step S 425  (powerful swirl) and to step S 406  (even spreading of laundry.) The mild swirl period can be replaced with a still period. 
     If, in step S 426 , the treatment substance to be added is not metal ions, then the treatment substance is treatment agent (softening agent). In this case, the flow proceeds to step  428 . 
     In step  428 , both the main water feed valve  50   a  and the sub water feed valve  50   b  are opened and water is fed to both of the main water feed passage  52   a  and the sub water feed passage  52   b . However, the ion elution unit  100  is not operated and metal ions are not generated. After sufficient water for causing an effect of siphon is supplied to the treatment agent chamber  55  and the treatment agent (softening agent) is put into the washing tub  30  by way of the siphon  57 , the sub water feed valve  50   b  is closed. 
     After the sub water feed valve  50   b  is closed, the main water feed valve  50   a  continues to feed water and stops feeding when the water level inside the washing tub  30  reaches a set level. 
     After step S 428 , the flow proceeds to step S 423 . After that, in the same manner as when metal ions and treatment agent (softening agent) are added simultaneously, the flow proceeds from S 423  (powerful whirl), to step S 424  (mild swirl) and then to step S 425  (powerful swirl) and to step S 406  (even spreading of the laundry). The mild swirl period can be replaced with a still period. 
     In this way, even when only one type of treatment substances is added, each of the steps from the powerful whirl to the mild swirl and then to the powerful whirl is to be taken to ensure that the treatment substance is attached to the laundry. However, since it is not necessary to equal the step-time distribution for metal ions and that for treatment agent (softening agent), the step-time distribution is adjusted to fit the type of treatment substance. 
     In case of a treatment agent (softening agent), it does not take a long time to attach to the laundry, unlike the case of the metal ions. Therefore, it is possible that after step S 428 , only step S 423  (powerful whirl) and step S 406  (even spreading of laundry) are taken and step S 423  (powerful whirl) can be finished within a short time such as two minutes, for example. 
     In order to operate the ion elution unit  100 , constant current circuit  125  of the drive circuit  120  controls the voltage, so that the current flowing between the electrodes  113  and  114  is constant. By this, the amount of eluted metal ions per unit time becomes constant. When the amount of eluted metal ions per unit time is constant, it is possible to control the concentration of metal ions in the washing tub  30  by controlling the volume of water flowing through the ion elution unit  100  and the time of metal ion elution, thereby the expected concentration of metal ions is easily achieved. 
     The current flowing between the electrodes  113  and  114  is direct current. If the current is alternating current, the following phenomenon occurs. Namely, when the metal ions are silver ions, for example, the silver ions that have once been eluted go back to the electrodes by reverse reaction, i.e. Ag + +e − →Ag, when the polarity of the electrodes is reversed. However, in case of direct current, such phenomenon does not occur. 
     On either one of the electrodes  113  and  114 , if it acts as a cathode, scale is deposited. When direct current continues to flow without reversing the polarity and, as a result, the amount of scale deposit become larger, the current is subjected to be restricted, and the metal ion elution does not proceed at the predetermined rate. Moreover, a phenomenon of “one-sided depletion,” in which only one electrode being used as an anode is consumed at a rate faster than the other. Therefore, the polarity of the electrodes  113  and  114  is reversed cyclically. 
     Being used for metal ion elution, the electrodes  113  and  114  are gradually depleted, resulting in drop in metal ion elution rate. When they are used for a long time, the metal ion elution rate becomes unstable and the predetermined metal ion elution rate is not obtained. Therefore, the ion elution unit  100  is made replaceable, and when the duration of electrodes  113  and  114  expires, it can be replaced with a new unit. Moreover, users are notified, through the operation/display panel  81 , the fact that the duration of electrodes  113  and  114  almost expires and therefore appropriate countermeasures, for example, replacement of the ion elution unit  100 , should be adapted. 
     It is to be understood that the present invention may be carried out in any other manner than specifically described above as an embodiment, and many modifications and variations are possible within the scope of the invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention finds wide application in situations wherein exploitation of the antimicrobial effect of metal ions is attempted. An ion elution unit according to the present invention can be effectively combined not only with a washer but also with a dish-washer, a humidifier, or any other type of appliance where growth of bacteria and mold needs to be suppressed. As for washers, to all types of washer than those of automatic type like the one, such as those having horizontal drums (e.g. tumbler type), those having slanted drums, those which function also as dryers, and those with two separated tubs, the present invention can be applied.