Abstract:
An apparatus for generating alkali ion water includes an electrolytic cell. At least two electrodes are disposed in the electrolytic cell. A diaphragm disposed in the electrolytic cell extends between the electrodes. A dc voltage is supplied to the electrodes. A mean value of the dc voltage is varied at a given inclination. A first detecting device operates to detect an ac current and generate a signal representative thereof. The dc voltage is derived from the ac current. A second detecting device operates to detect the mean value of the dc voltage in response to the signal generated by the first detecting device. A third detecting device operates to detect an inclination in a variation in the mean value of the dc voltage in response to the mean value of the dc voltage which is detected by the second detecting device. The mean value of the dc voltage is controlled in response to the inclination detected by the third detecting device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to an apparatus for generating water containing alkali ions. This invention specifically relates to an apparatus for electrolyzing source water such as city water or well water into alkali ion water (water containing alkali ions) and acid ion water (water containing acid ions). 
     2. Description of the Prior Art 
     Water containing alkali ions is used as drink or medical water. Water containing acid ions is used for makeup or sterilizing and cleaning purposes. It is known to electrolyze source water such as city water or well water into alkali ion water and acid ion water. 
     A typical prior-art water adjuster using electrolysis includes a filtering section provided with activated charcoal or a hollow fiber membrane. The filtering section removes impurities, bacteria, and remaining chlorine from source water. The filtering section is followed by a mineral supply section which adds mineral such as calcium glycerophosphate to the source water to increase the electric conductivity of the source water. The mineral supply section is followed by an electrolytic cell having a pair of chambers separated by a diaphragm from each other. Electrodes are disposed in the chambers respectively. The source water flows into the chambers from the mineral supplying section. A dc voltage is applied between the electrodes so that the source water in the chambers is electrolyzed into alkali ion water and acid ion water. 
     In the prior-art water adjuster, the pH of the generated alkali ion water and the pH of the generated acid ion water can be adjusted by changing the magnitude of the dc voltage applied between the electrodes. In the case where the prior-art water adjuster restarts after a long-period suspension of operation, the electrolytic cell tends to be supplied with water containing a large amount of mineral or highly-conductive water so that the electrolytic cell is liable to receive an excessively-great electric current. Such an excessively-great electric current causes an instability in the pH of generated alkali ion water and the pH of generated acid ion water. 
     Japanese published unexamined patent application 53-88666 discloses a potable water generator having an electrolytic cell for changing neutral water into alkali ion water and acid ion water. The prior-art potable water generator includes a circuit for limiting an electric current flowing in the electrolytic cell. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an improved apparatus for generating alkali ion water. 
     A first aspect of this invention provides an apparatus for generating alkali ion water which comprises an electrolytic cell; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; means for supplying a dc voltage to the electrodes; and means for varying a mean value of the dc voltage at a given inclination. 
     A second aspect of this invention provides an apparatus for generating alkali ion water which comprises means for filtering source water; means, connected to the filtering means, for supplying mineral to the source water; an electrolytic cell connected to the mineral supplying means; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; means for supplying a dc voltage to the electrodes; and means for varying a mean value of the dc voltage at a given inclination. 
     A third aspect of this invention provides an apparatus for generating alkali ion water which comprises means for filtering source water; means, connected to the filtering means, for supplying mineral to the source water; an electrolytic cell connected to the mineral supplying means; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; first detecting means for detecting an ac current and generating a signal representative thereof; means for deriving a dc voltage from the ac current and supplying the dc voltage to the electrodes; second detecting means for detecting a mean value of the dc voltage in response to the signal generated by the first detecting means; means for determining a desired mean value of the dc voltage in response to a desired pH of generated ion water; means for comparing the mean value of the dc voltage which is detected by the second detecting means with a given range around the desired mean value; an indicator; and means for controlling the indicator in response to a result of comparison by the comparing means. 
     A fourth aspect of this invention provides an apparatus for generating alkali ion water which comprises means for filtering source water; means, connected to the filtering means, for supplying mineral to the source water; an electrolytic cell connected to the mineral supplying means and having an outlet; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; a discharge passage; a drain passage; means for selectively connecting the outlet of the electrolytic cell to the discharge passage or the drain passage; means for supplying a dc voltage to the electrodes; and means for varying a mean value of the dc voltage at a given inclination. 
     A fifth aspect of this invention provides an apparatus for generating alkali ion water which comprises means for filtering source water; means, connected to the filtering means, for supplying mineral to the source water; an electrolytic cell connected to the mineral supplying means and having an outlet; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; a discharge passage; a drain passage; means for selectively connecting the outlet of the electrolytic cell to the discharge passage or the drain passage; first detecting means for detecting an ac current and generating a signal representative thereof; means for deriving a dc voltage from the ac current and supplying the dc voltage to the electrodes; second detecting means for detecting a mean value of the dc voltage in response to the signal generated by the first detecting means; means for determining a desired mean value of the dc voltage in response to a desired pH of generated ion water; means for comparing the mean value of the dc voltage which is detected by the second detecting means with a given range around the desired mean value; an indicator; and means for controlling the indicator in response to a result of comparison by the comparing means. 
     A sixth aspect of this invention provides an apparatus for generating alkali ion water which comprises means for filtering source water; means, connected to the filtering means, for supplying mineral to the source water; an electrolytic cell connected to the mineral supplying means and having an outlet; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; a discharge passage; a drain passage; means for selectively connecting the outlet of the electrolytic cell to the discharge passage or the drain passage; first detecting means for detecting an ac current and generating a signal representative thereof; means for deriving a dc voltage from the ac current and supplying the dc voltage to the electrodes; second detecting means for detecting a mean value of the dc voltage in response to the signal generated by the first detecting means; third detecting means for detecting an inclination in a variation in the mean value of the dc voltage in response to the mean value of the dc voltage which is detected by the second detecting means; means for increasing the mean value of the dc voltage at an inclination; and means for controlling the inclination in a range of 18 V/second to 9 V/second in response to the inclination detected by the third detecting means; means for determining a desired mean value of the dc voltage in response to a desired pH of generated ion water: means for comparing the mean value of the dc voltage which is detected by the second detecting means with a given range around the desired mean value; an indicator; and means for controlling the indicator in response to a result of comparison by the comparing means. 
     A seventh aspect of this invention provides an apparatus for generating alkali ion water which comprises an electrolytic cell for electrolyzing source water into alkali ion water and acid ion water; means for supplying a dc voltage to the electrolytic cell; and means for varying a mean value of the dc voltage at a given inclination. 
     An eighth aspect of this invention provides an apparatus for generating alkali ion water which comprises an electrolytic cell for electrolyzing source water into alkali ion water and acid ion water; means for supplying a dc voltage to the electrolytic cell; and means for detecting a rate of a variation in a mean value of the dc voltage. 
     A ninth aspect of this invention provides an apparatus for generating alkali ion water which comprises an electrolytic cell; at least two electrodes disposed in the electrolytic cell; a diaphragm disposed in the electrolytic cell and extending between the electrodes; means for supplying a dc voltage to the electrodes; and means for detecting a rate of a variation in a mean value of the dc voltage. 
     A tenth aspect of this invention provides an apparatus for generating ion water which comprises an electrolytic cell for electrolyzing source water into ion water; means for supplying a dc voltage to the electrolytic cell; means for gradually increasing an effective level of the dc voltage at a rate; and means for limiting the rate to within a predetermined range. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram of an apparatus for generating alkali ion water according to an embodiment of this invention. 
     FIG. 2 is a diagram of an electric portion of the apparatus in FIG.  1 . 
     FIG. 3 is a flowchart of a segment of a program for operating a controller in FIGS. 1 and 2. 
     FIG. 4 is a time-domain diagram of a rate of flow of source water into the apparatus of FIG.  1 . 
     FIG. 5 is a time-domain diagram of the ion concentration in source water in a mineral supply section of the apparatus of FIG.  1 . 
     FIG. 6 is a time-domain diagram of the electric conductivity of water in an electrolytic cell in the apparatus of FIG.  1 . 
     FIG. 7 is a time-domain diagram of a mean value of a dc voltage applied between electrodes in the apparatus of FIG.  1 . 
     FIG. 8 is a time-domain diagram of a mean value of an electric current through electrodes in the apparatus of FIG.  1 . 
     FIG. 9 is a time-domain diagram of the pH of alkali ion water generated by the apparatus of FIG.  1 . 
     FIG. 10 is a time-domain diagram of a mean value of a dc voltage applied between electrodes and a mean value of an electric current through the electrodes in the apparatus of FIG.  1 . 
     FIG. 11 is a time-domain diagram of a mean value of a dc voltage applied between electrodes and a mean value of an electric current through the electrodes which occur in a reference example. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, an apparatus  3  for generating alkali ion water includes a filtering section  4  to which a source water pipe  1  such as a city water pipe or a well water pipe is connected via a cock  2 . When the cock  2  is in an open position, source water is permitted to enter the filtering section  4  from the source water pipe  1 . When the cock  2  is in a closed position, the supply of the source water to the filtering section  4  is inhibited. 
     The filtering section  4  contains activated charcoal and a filter such as a hollow fiber membrane. The activated charcoal removes remaining chlorine from the source water. The filter removes impurities and bacteria from the source water. 
     A mineral supply section  5  following the filtering section  4  receives the source water from the filtering section  4 . The mineral supply section  5  adds minerals such as calcium glycerophosphate and calcium lactate to the source water to increase the electric conductivity of the source water. 
     The mineral supply section  5  is connected to an electrolytic cell  7  via a water passage in which a flow rate sensor  6  is disposed. The source water flows into the electrolytic cell  7  from the mineral supply section  5  via the flow rate sensor  6 . The flow rate sensor  6  detects the rate of the flow of the source water in the water passage, that is, the rate of the flow of the source water into the electrolytic cell  7 . 
     The interior of the electrolytic cell  7  is divided by a diaphragm  8  into a pair of chambers  9 A and  10 A in which electrodes  9  and  10  are disposed respectively. The chambers  9 A and  10 A in the electrolytic cell  7  communicate with each other via a lower opening which extends through the diaphragm  8 . 
     A drain pipe  11   a  is connected via a flow rate adjusting section  12  to the chamber  10 A in the electrolytic cell  7 . Water flows to the drain pipe  11   a  from the chamber  10 A in the electrolytic cell  7 . The rate of the flow of the water to the drain pipe  11   a  is controlled by the flow rate adjusting section  12 . The flow rate adjusting section  12  includes, for example, a restriction or a valve. 
     A discharge pipe  13  is connected to a first outlet of a three-way electromagnetic valve (a three-way solenoid valve)  14 . A second outlet of the three-way valve  14  is connected via a pipe  11   b  to a region of the drain pipe  11   a  downstream of the flow rate adjusting section  12 . An inlet of the three-way valve  14  is connected via a pipe to the chamber  9 A in the electrolytic cell  7 . 
     The three-way valve  14  can be changed between a first position and a second position. When the three-way valve  14  assumes the first position, its inlet is connected to the first outlet and is disconnected from the second outlet so that water flows to the discharge pipe  13  from the chamber  9 A in the electrolytic cell  7 . When the three-way valve  14  assumes the second position, its inlet is connected to the second outlet and is disconnected from the first outlet so that water flows to the drain pipe  11   a  from the chamber  9 A in the electrolytic cell  7 . 
     One end of a pipe  11   c  is connected to the water passage between the flow rate sensor  6  and the electrolytic cell  7 . The other end of the pipe  11   c  is connected to a region of the drain pipe  11   a  downstream of the flow rate adjusting section  12  and the connection with the pipe  11   b . An electromagnetic valve  15  is disposed in the pipe  11   c.    
     A cartridge sensor  16  detects whether a cartridge for the filtering section  4  is present or absent. 
     A power supply  18  can be electrically connected to an ac power line (not shown) via a plug  17 . The power supply  18  can receive an ac voltage from the ac power line via the plug  17 . The power supply  18  is electrically connected to a controller  21 , an operation/display section  22 , and a relay unit  90 . 
     The controller  21  is electrically connected to the flow rate sensor  6 , the three-way valve  14 , the cartridge sensor  16 , the operation/display section  22 , and the relay unit  90 . The relay unit  90  is electrically connected to the electrodes  9  and  10 . Also, the relay unit  90  is electrically connected to the electromagnetic valve  15 . 
     The controller  21  receives output signals of the flow rate sensor  6 , the cartridge sensor  16 , and the operation/display section  22 . The controller  21  outputs signals to the three-way valve  14 , the operation/display section  22 , and the relay unit  90  to control them. 
     The controller  21  also controls the electromagnetic valve  15  via the relay unit  90 . The controller  21  includes a microcomputer or a similar device which has a combination of an I/O port, a CPU, a RAM, and a ROM. The controller  21  operates in accordance with a program stored in the ROM. 
     The operation of the apparatus  3  can be changed among a plurality of different modes including an alkali ion water generating mode, an acid ion water generating mode, a filtered water generating mode, and an electrode cleaning mode. The user or operator can select one of the modes of operation of the apparatus  3  by actuating the operation/display section  22 . In addition, the user or operator can set a desired pH of generated ion water by actuating the operation/display section  22 . The operation/display section  22  indicates operating conditions of the apparatus  3  which include a selected mode of operation thereof and a desired pH of generated ion water. 
     As will be made clear later, the controller  21  can serve as an inclination detector (a slope detector)  19  which detects a rate or an inclination (a slope) of a change in a mean value of a dc voltage applied between the electrodes  9  and  10 . The controller  21  can also serve as a comparator  20  which compares a mean value of a dc voltage applied between the electrodes  9  and  10  with a reference mean voltage value determined by the desired pH of generated ion water. The comparator  20  may also compare the value of a mean electric current through the electrodes  9  and  10  with a reference mean current value determined by the desired pH of generated ion water. 
     As shown in FIG. 2, the power supply  18  includes a transformer  24  having a primary winding  24 A and secondary windings  24 B and  24 C. The primary winding  24 A is connected to the plug  17 . The secondary winding  24 B is connected to a dc power supply  25  including a rectifying circuit. The dc power supply  25  is connected to the controller  21  and the operation/display section  22 . An ac voltage which appears across the secondary winding  24 B is converted by the dc power supply  25  into a dc voltage. The dc power supply  25  feeds the dc voltage to the controller  21  and the operation/display section  22  to power them. 
     The secondary winding  24 C of the transformer  24  is connected via a current transducer or a current sensor  27  to a dc power supply  26  including a rectifying circuit. The dc power supply  26  is connected to the electrodes  9  and  10  via the relay unit  90 . An ac voltage which appears across the secondary winding  24 C is converted by the dc power supply  26  into a dc voltage. The dc voltage generated by the dc power supply  26  can be applied between the electrodes  9  and  10  via the relay unit  90  as an electrolyzing voltage. The dc power supply  26  is also connected to the control winding of the electromagnetic valve  15  via the relay unit  90 . The dc voltage generated by the dc power supply  26  can be applied to the electromagnetic valve  15  via the relay unit  90 . 
     The current transducer  27  detects an ac current which flows into the dc power supply  26  from the secondary winding  24 C of the transformer  24 . The current transducer  27  is followed by a rectifying/smoothing circuit  28 . An output signal of the current transducer  27  is converted by the rectifying/smoothing circuit  28  into a signal having a voltage which varies as a function of the magnitude or amplitude of the ac current detected by the current transducer  27 . The rectifying/smoothing circuit  28  outputs the voltage signal to the controller  21 . 
     The relay unit  90  includes a voltage adjuster  29 , and relays  30  and  31 . A first output terminal of the dc power supply  26  is directly connected to the relay  30 . A second output terminal of the dc power supply  26  is connected to the relay  30  via the voltage adjuster  29 . The relay  30  is connected to the relay  31 . The relay  30  is also connected to the control winding of the electromagnetic valve  15 . The relay  31  is connected to the electrodes  9  and  10 . Control terminals of the voltage-adjuster  29  and the relays  30  and  31  are connected to the controller  21 . 
     The dc voltage outputted from the dc power supply  26  can be applied between the electrodes  9  and  10  via the voltage adjuster  29  and the relays  30  and  31 . The dc voltage outputted from the dc power supply  26  can be applied to the electromagnetic valve  15  via the voltage adjuster  29  and the relay  30 . The relay  30  functions to selectively transmit the dc voltage to the electrodes  9  and  10  or to the electromagnetic valve  15 . The relay  30  is controlled by an output signal from the controller  21 . The relay  31  functions to change the polarity of the dc voltage applied between the electrodes  9  and  10 . Specifically, the relay  31  can change between a first state and a second state. When the relay  31  assumes the first state, the electrode  9  receives a negative potential and the electrode  10  receives a positive potential. When the relay  31  assumes the second state, the electrode  9  receives a positive potential and the electrode  10  receives a negative potential. The relay  31  is controlled by an output signal from the controller  21 . 
     The electrolyzing voltage generated by the power supply  26  is preferably held constant. The voltage adjuster  29  includes a switch which can change between an on state (a closed state) and an off state (an open state). The voltage adjuster  29  functions to vary a mean level (a mean magnitude or an effective level) of the dc voltage applied between the electrodes  9  and  10 . The voltage adjuster  29  is controlled by an output signal from the controller  21 . Specifically, the output signal from the controller  21  to the voltage adjuster  29  is a pulse signal having a predetermined constant frequency and a variable duty cycle (duty factor). To this end, the I/O port in the controller  21  includes a combination of a pulse signal generator and a pulse-width modulator. The frequency of the pulse signal fed to the voltage adjuster  29  is preferably equal to a value in the range of 100 Hz to 1,000 Hz. The switch in the voltage adjuster  29  changes between the on state and the off state in response to the pulse signal fed from the controller  21 . As the duty cycle of the pulse signal fed to the voltage adjuster  29  increases, the mean level (the mean magnitude or the effective level) of the dc voltage applied between the electrodes  9  and  10  rises. 
     The apparatus  3  operates as follows. When the cock  2  is changed to the open position, source water enters the filtering section  4  from the source water pipe  1 . The filtering section  4  removes remaining chlorine, impurities, and bacteria from the source water. The source water flows from the filtering section  4  to the mineral supply section  5 . The mineral supply section  5  adds minerals such as calcium glycerophosphate and calcium lactate to the source water to increase the electric conductivity of the source water. The source water flows from the mineral supply section  5  to the electrolytic cell  7  via the flow rate sensor  6 . The flow rate sensor  6  detects the rate of the flow of the source water in the water passage, that is, the rate of the flow of the source water into the electrolytic cell  7 . The chambers  9 A and  10 A in the electrolytic cell  7  are filled with the source water. 
     The power supply  18  feeds the dc voltage to the controller  21  and the operation/display section  22  to power them. The power supply  18  generates the dc voltage for electrolysis which is fed to the relay unit  90 . 
     The controller  21  receives an output signal from the flow rate sensor  6  which represents the rate of the flow of the source water into the electrolytic cell  7 . Thus, the controller  21  is informed of the detected rate of the flow of the source water into the electrolytic cell  7 . The controller  21  decides whether or not the detected rate of the flow of the source water into the electrolytic cell  7  exceeds a predetermined reference flow rate. When the detected flow rate exceeds the reference flow rate, the controller  21  detects that the water supply to the electrolytic cell  7  is currently present. In this case, the controller  21  executes subsequent processes which will be indicated later. On the other hand, when the detected flow rate does not exceed the reference flow rate, the controller  21  detects that the water supply to the electrolytic cell  7  is currently absent. In this case, the controller  21  falls into a stand-by state for waiting the occurrence of the water supply to the electrolytic cell  7 . 
     When the controller  21  detects the presence of the water supply to the electrolytic cell  7 , the controller  21  detects the selected mode of operation of the apparatus  3  by referring to an output signal from the operation/display section  22 . 
     In the case where the selected mode of operation agrees with the alkali ion water generating mode, the controller  21  sets the relays  30  and  31  in the relay unit  90  so that a positive potential is applied to the electrode  10  and −  a negative potential is applied to the electrode  9 . The application of the dc voltage between the electrodes  9  and  10  causes electrolysis in the electrolytic cell  7 . Specifically, the source water in the electrolytic cell  7  is electrolyzed into alkali ion water and acid ion water. In the electrolytic cell  7 , the alkali ion water occurs in the chamber  9 A while the acid ion water occurs in the chamber  10 A. The controller  21  derives information of a desired pH of the generated ion water from an output signal of the operation/display section  22 . In addition, the controller  21  derives information of the rate of the source water supply to the electrolytic cell  7  from an output signal of the flow rate sensor  6 . The controller  21  calculates or determines a desired mean dc voltage applied between the electrodes  9  and  10  in response to the desired pH of the generated ion water and the rate of the source water supply to the electrolytic cell  7 . During an initial stage, the controller  21  gradually increases the actual mean dc voltage applied between the electrodes  9  and  10  to the desired mean dc voltage. The increase in the actual mean dc voltage is realized by increasing the duty cycle of the output pulse signal to the voltage adjuster  29 . Until the actual mean dc voltage reaches the desired mean dc voltage, the controller  21  judges an actual pH of the generated ion water to be different from the desired pH thereof. Accordingly, the controller  21  changes the three-way valve  14  so that the chamber  9 A in the electrolytic cell  7  communicates with the drain pipe  11   a  and hence the water flows from the chamber  9 A to the drain pipe  11   a.  The water is removed from the apparatus  3  via the drain pipe  11   a.  On the other hand, when the actual mean dc voltage reaches the desired mean dc voltage, the controller  21  judges the actual pH of the generated ion water to be equal to the desired pH thereof. Accordingly, the controller  21  changes the three-way valve  14  so that the chamber  9 A in the electrolytic cell  7  communicates with the discharge pipe  13  and hence the alkali ion water flows from the chamber  9 A to the discharge pipe  13 . The alkali ion water is continuously discharged from the apparatus  3  via the discharge pipe  13 . When the detected rate of the flow of the source water into the electrolytic cell  7  drops to or below the reference flow rate, the controller  21  changes and sets the voltage adjuster  29  so that the application of the dc voltage between the electrodes  9  and  10  is continuously inhibited. Thus, the alkali ion water generating mode of operation terminates. 
     In the case where the selected mode of operation agrees with the acid ion water generating mode, the controller  21  sets the relays  30  and  31  in the relay unit  90  so that a positive potential is applied to the electrode  9  and a negative potential is applied to the electrode  10 . The application of the dc voltage between the electrodes  9  and  10  causes electrolysis in the electrolytic cell  7 . Specifically, the source water in the electrolytic cell  7  is electrolyzed into alkali ion water and acid ion water. In the electrolytic cell  7 , the alkali ion water occurs in the chamber  10 A while the acid ion water occurs in the chamber  9 A. The controller  21  derives the information of the desired pH of the generated ion water from the output signal of the operation/display section  22 . In addition, the controller  21  derives the information of the rate of the source water supply to the electrolytic cell  7  from the output signal of the flow rate sensor  6 . The controller  21  calculates or determines the desired mean dc voltage applied between the electrodes  9  and  10  in response to the desired pH of the generated ion water and the rate of the source water supply to the electrolytic cell  7 . During an initial stage, the controller  21  gradually increases the actual mean dc voltage applied between the electrodes  9  and  10  to the desired mean dc voltage. The increase in the actual mean dc voltage is realized by increasing the duty cycle of the output pulse signal to the voltage adjuster  29 . Until the actual mean dc voltage reaches the desired mean dc voltage, the controller  21  judges the actual pH of the generated ion water to be different from the desired pH thereof. Accordingly, the controller  21  changes the three-way valve  14  so that the chamber  9 A in the electrolytic cell  7  communicates with the drain pipe  11   a  and hence the water flows from the chamber  9 A to the drain pipe  11   a.  The water is removed from the apparatus  3  via the drain pipe  11   a.  On the other hand, when the actual mean dc voltage reaches the desired mean dc voltage, the controller  21  judges the actual pH of the generated ion water to be equal to the desired pH thereof. Accordingly, the controller  21  changes the three-way valve  14  so that the chamber  9 A in the electrolytic cell  7  communicates with the discharge pipe  13  and hence the acid ion water flows from the chamber  9 A to the discharge pipe  13 . The acid ion water is continuously discharged from the apparatus  3  via the discharge pipe  13 . When the detected rate of the flow of the source water into the electrolytic cell  7  drops to or below the reference flow rate, the controller  21  changes and sets the voltage adjuster  29  so that the application of the dc voltage between the electrodes  9  and  10  is continuously inhibited. Thus, the acid ion water generating mode of operation terminates. After the end of the acid ion water generating mode of operation, the controller  21  changes the relay  30  and thereby opens the electromagnetic valve  15  so that the water flows from the electrolytic cell  7  to the drain pipe  11   a.  The water is removed from the apparatus  3  via the drain pipe  11   a  so that the acid ion water can be prevented from being used as drink. 
     During the execution of the alkali ion water generating mode of operation or the acid ion water generating mode of operation except the initial stage, the controller  21  maintains the actual mean dc voltage applied between the electrodes  9  and  10  at essentially the desired mean dc voltage. As previously described, the level of the voltage signal outputted from the rectifying/smoothing circuit  28  to the controller  21  depends on the magnitude or amplitude of the ac current detected by the current transducer  27 , that is, depends on the magnitude or amplitude of the ac current flowing into the dc power supply  26 . Since the magnitude or amplitude of the ac current flowing into the dc power supply  26  varies as a function of the mean value of the dc voltage applied between the electrodes  9  and  10 , the voltage signal outputted from the rectifying/smoothing circuit  28  to the controller  28  represents the mean value of the dc voltage applied between the electrodes  9  and  10 . The voltage signal outputted from the rectifying/smoothing circuit  28  to the controller  28  also represents the mean value of the dc current driven through the electrodes  9  and  10 . The controller  21  detects the actual mean dc voltage applied to the electrodes  9  and  10  by referring to the output signal from the rectifying/smoothing circuit  28 . The controller  21  compares the actual mean dc voltage with the desired mean dc voltage. This process corresponds to the operation of the comparator  20 . When the actual mean dc voltage exceeds the desired mean dc voltage (this condition corresponds to an over current through the electrodes  9  and  10 ), the controller  21  operates the voltage adjuster  29  so that the actual mean dc voltage applied between the electrodes  9  and  10  will drop. When the actual mean dc voltage decreases below the desired mean dc voltage (this condition corresponds to an insufficient current through the electrodes  9  and  10 ), the controller  21  operates the voltage adjuster  29  so that the actual mean dc voltage applied between the electrodes  9  and  10  will increase. As a result, the actual mean dc voltage applied between the electrodes  9  and  10  is maintained at essentially the desired mean dc voltage. This state corresponds to the fact that an actual mean electric current through the electrodes  9  and  10  is maintained at essentially a desired mean electric current. When the actual mean dc voltage is approximately equal to the desired mean dc voltage, the pH of the discharged alkali ion water or the discharged acid ion water substantially agrees with the desired pH. As the desired pH is varied, the desired mean dc voltage is changed. Therefore, the actual pH of the-discharged alkali ion water or the discharged acid ion water follows the desired pH. 
     During the execution of the alkali ion water generating mode of operation or the acid ion water generating mode of operation except the initial stage, the controller  21  or the comparator  20  decides whether or not the actual mean dc voltage applied between the electrodes  9  and  10  is in a given acceptable range ΔV (see FIG. 7) around the desired mean dc voltage. When the actual mean dc voltage is decided to be in the acceptable range ΔV, the controller  21  or the comparator  20  controls an indicator in the operation/display section  22  to inform the user of the acceptable condition. When the actual mean dc voltage is decided to be outside the acceptable range ΔV, the controller  21  or the comparator  20  controls the indicator in the operation/display section  22  to inform the user of the unacceptable condition. In addition, the controller  21  or the comparator  20  decides whether or not the actual mean electric current through the electrodes  9  and  10  is in a given acceptable range ΔI (see FIG. 8) around the desired mean electric current. When the actual mean electric current is decided to be in the acceptable range ΔI, the controller  21  or the comparator  20  controls the indicator in the operation/display section  22  to inform the user of the acceptable condition. When the actual mean electric current is decided to be outside the acceptable range ΔI, the controller  21  or the comparator  20  controls the indicator in the operation/display section  22  to inform the user of the unacceptable condition. 
     In the case where the selected mode of operation agrees with the filtered water generating mode, the controller  21  sets the voltage adjuster  29  so that the application of the dc voltage between the electrodes  9  and  10  is continuously inhibited. As a result, electrolysis does not occur in the electrolytic cell  7 . The filtered water flows into the electrolytic cell  7  from the filtering section  4 . The controller  21  changes the three-way valve  14  so that the chamber  9 A in the electrolytic cell  7  communicates with the discharge pipe  13  and hence the filtered water flows from the chamber  9 A to the discharge pipe  13 . The filtered water is continuously discharged from the apparatus  3  via the discharge pipe  13 . 
     During the alkali ion water generating mode of operation, scales deposit on at least one of the electrodes  9  and  10 . The electrode cleaning mode of operation is executed to remove the scales from at least one of the electrodes  9  and  10 . In the case where the selected mode of operation agrees with the electrode cleaning mode, the controller  21  detects whether the water supply to the electrolytic cell  7  is currently present or absent by referring to the output signal from the flow rate sensor  6 . When the water supply to the electrolytic cell  7  is detected to be absent, the controller  21  sets the relays  30  and  31  in the relay unit  90  so that a positive potential is applied to the electrode  9  and a negative potential is applied to the electrode  10 . The application of the dc voltage between the electrodes  9  and  10  dissolves scales on at least one of the electrodes  9  and  10  back into the water in the electrolytic cell  7 . During an initial stage, the controller  21  gradually increases the mean dc voltage applied between the electrodes  9  and  10  as in the alkali ion water generating mode. After the removal of the scales from at least one of the electrodes  9  and  10  has been completed, the controller  21  changes the relay  30  and thereby opens the electromagnetic valve  15  so that the water flows from the electrolytic cell  7  to the drain pipe  11   a  via the electromagnetic valve  15 . The water is removed from the apparatus  3  via the drain pipe  11   a.    
     It is preferable that the controller  21  counts the number of times of execution of the alkali ion water generating mode and measures the total time of use of the electrodes  9  and  10  in the alkali ion water generating mode after the end of preceding execution of the electrode cleaning mode. In this case, the controller  21  compares the counted number of times and the measured total time with a predetermined reference number of times and a predetermined reference time respectively. When the counted number of times reaches the reference number of times and also the water supply to the electrolytic cell  7  is detected to be absent, the controller  21  automatically starts the electrode cleaning mode of operation of the apparatus  3 . When the measured total time reaches the reference time and also the water supply to the electrolytic cell  7  is detected to be absent, the controller  21  automatically starts the electrode cleaning mode of operation of the apparatus  3 . 
     As previously described, the controller  21  operates in accordance with a program stored in the internal ROM. FIG. 3 is a flowchart of a segment of the program which provides the gradual increase in the actual mean dc voltage applied between the electrodes  9  and  10  during the initial stage of the alkali ion water generating mode of operation, the acid ion water generating mode of operation, or the electrode cleaning mode of operation. 
     As shown in FIG. 3, a first step S 1  of the segment of the program derives information of a desired pH of generated ion water from the output signal of the operation/display section  22 . In addition, the step Si derives information of the rate of the source water supply to the electrolytic cell  7  from the output signal of the flow rate sensor  6 . Then, the step calculates or determines a final desired mean dc voltage V 0  applied between the electrodes  9  and  10  in response to the desired pH of the generated ion water and the rate of the source water supply to the electrolytic cell  7 . 
     A step S 2  following the step S 1  sets a variable V 1  to a predetermined initial value. The variable V 1  indicates a first desired mean dc voltage applied between the electrodes  9  and  10 . The initial value of the desired mean dc voltage V 1  corresponds to, for example, a zero voltage “0”. After the step S 2 , the program advances to a step S 3 . 
     The step S 3  periodically detects the actual mean dc voltage applied between the electrodes  9  and  10  at predetermined short intervals by referring the output signal from the rectifying/smoothing circuit  28 . Then, the step S 3  detects an inclination (a rate or a slope) “k” of a change in the actual mean dc voltage by referring to the results of the periodical detection of the actual mean dc voltage. The step S 3  corresponds to the inclination detector  19 . 
     A step S 4  following the step S 3  decides whether or not the detected inclination “k” lies in a predetermined range between limit inclinations K 1  and K 2 . When the detected inclination “k” lies in the predetermined range, the program advances from the step S 4  to a step S 5 . Otherwise, the program advances from the step S 4  to a step S 7 . 
     The step S 5  detects the actual mean dc voltage V 2  applied between the electrodes  9  and  10  by referring the output signal from the rectifying/smoothing circuit  28 . Then, the step S 5  decides whether or not the actual mean dc voltage V 2  is equal to the final desired mean dc voltage V 0 . When the actual mean dc voltage V 2  is different from the final desired mean dc voltage V 0 , the program advances from the step S 5  to a step S 6 . When the actual mean dc voltage V 2  is equal to the final desired mean dc voltage V 0 , the program advances from the step S 5  to a step S 8 . 
     The step S 6  increases the actual mean dc voltage applied to the electrodes  9  and  10  at a given inclination (a given slope or rate) by controlling the voltage adjuster  29 . For example, the step S 6  increments the first desired mean dc voltage V 1  by a small value ΔV 1  according to the program statement as “V 1 =V 1 +ΔV 1 ”. Then, the step S 6  controls the voltage adjuster  29  in response to the first desired mean dc voltage V 1  so that the actual mean dc voltage will increase at a rate corresponding to the small value ΔV 1 . After the step S 6 , the program returns to the step S 3 . 
     The step S 7  adjusts an inclination factor (an inclination coefficient or a slope coefficient) so that the inclination or rate “k” of the increase in the actual mean dc voltage will fall into the predetermined range (between K 1  and K 2 ). For example, when the detected inclination “k” exceeds the upper limit K 2 , the step S 7  decreases the small value ΔV 1  used in the step S 6 . When the detected inclination “k” is smaller than the lower limit K 1 , the step S 7  increases the small value ΔV 1  used in the step S 6 . After the step S 7 , the program advances to the step S 5 . As a result of the process executed by the step S 7 , the inclination or rate “k” of the increase in the actual mean dc voltage will be essentially maintained in the predetermined range (between K 1  and K 2 ). 
     The step S 8  controls the voltage adjuster  29  in response to the final desired mean dc voltage V 0  so that the actual mean dc voltage will be essentially equal to the final desired mean dc voltage V 0 . After the step S 8 , the current execution cycle of the segment of the program ends. 
     During the initial stage of the alkali ion water generating mode of operation, the acid ion water generating mode of operation, or the cleaning mode of operation, the actual mean dc voltage applied between the electrodes  9  and  10  gradually increases to the desired mean dc voltage as a result of the processes by the program segment of FIG.  3 . The steps S 4  and S 7  in FIG. 3 enable the inclination (rate) of the increase in the actual mean dc voltage to be maintained in the predetermined range (between K 1  and K 2 ). Accordingly, the increase in the-actual mean dc voltage from the initial mean voltage (for example, 0 V) to the desired mean dc voltage takes a given time. In the case where the predetermined range for the inclination is 18 V/sec to 9 V/sec and the desired mean dc voltage is 36 V, the increase in the actual mean dc voltage from the initial mean voltage to the desired mean dc voltage takes a time of 2 seconds to 4 seconds. 
     Experiments were performed in connection with the apparatus  3 . During the experiments, measurements were given of an actual mean dc voltage applied between the electrodes  9  and  10 , an actual mean electric current through the electrodes  9  and  10 , and other parameters. 
     During the experiments, the apparatus  3  was operated in the alkali ion water generating mode, and the supply of source water to the apparatus  3  was interrupted at a moment t 0  as shown in FIG. 4 so that the alkali ion water generating mode of operation stopped. The supply of source water to the apparatus  3  remained interrupted for an interval between the moment t 0  and a subsequent moment t 1  as shown in FIG.  4 . At the moment t 1 , the supply of source water to the apparatus  3  was started as shown in FIG. 4 so that the alkali ion water generating mode of operation was restarted. 
     Under these conditions, the ion concentration in source water in the mineral supply section  5  varied as shown in FIG. 5, and the electric conductivity of water in the electrolytic cell  7  varied as shown in FIG.  6 . As shown in FIG. 5, during the interruption of the supply of source water to the apparatus  3 , the ion concentration in source water in the mineral supply section  5  increased since calcium ions and other ions dissolved in the source water. At the start of the supply of source water to the apparatus  3  after the interruption of the supply of source water to the apparatus  3 , the source water having a high ion concentration flowed into the electrolytic cell  7  so that the electric conductivity of water in the electrolytic cell  7  temporarily increased as shown in FIG.  6 . 
     As shown in FIG. 7, during an interval Δt corresponding to the start of the supply of source water to the apparatus  3  after the interruption of the supply of source water to the apparatus  3 , the actual mean dc voltage applied between the electrodes  9  and  10  gradually increased to the desired mean dc voltage. The inclination (rate) of the increase in the actual mean dc voltage was maintained in the predetermined range (between K 1  and K 2 ). This control of the actual mean dc voltage prevented the actual mean electric current through the electrodes  9  and  10  from reaching an over-current level as shown in FIG.  8 . In addition, as shown in FIG. 9, the pH of generated alkali ion water gradually increased to the desired pH. 
     In a reference example, an actual mean dc voltage applied between electrodes abruptly increased to a desired mean dc voltage at a start of source water supply as shown in FIG.  7 . The abrupt increase in the actual mean dc voltage caused an actual mean electric current through the electrodes from exceeding an over-current level as shown in FIG.  8 . In addition, as shown in FIG. 9, the pH of generated alkali ion water exceeded a desired pH. According to the embodiment of this invention, in the case where the desired mean dc voltage was 36 V, the actual mean dc voltage applied between the electrodes  9  and  10  gradually increased to the desired mean dc voltage as shown in FIG. 10 during a start of the alkali ion generating mode of operation of the apparatus  3 . About 4 seconds were spent in the increase of the actual mean dc voltage from the initial mean voltage to the desired mean dc voltage. As the actual mean dc voltage gradually increased, the actual mean electric current through the electrodes  9  and  10  gradually increased. It was understood from FIG. 10 that the actual mean electric current was prevented from reaching an over-current level, and that the actual mean electric current moved into a stable state at a moment which followed the start of the electrolysis by 3 seconds to 4 seconds. 
     According to a reference example, in the case where a desired mean dc voltage was 36 V, an actual mean dc voltage applied between electrodes abruptly increased to the desired mean dc voltage as shown in FIG. 11 during a start of alkali ion generating operation. It was understood from FIG. 11 that the abrupt increase in the actual mean dc voltage caused an actual mean electric current to exceed an over-current level, and that the actual mean electric current moved from an unstable state to a stable state at a moment which followed the start of the electrolysis by at least 10 seconds. The unstable actual mean electric current results in an unstable pH of generated ion water. 
     According to a modification of the embodiment of this invention, during a given interval from the start of electrolysis, the controller  21  controls the indicator in the operation/display section  22  to inform the user that the pH of generated ion water is unstable. After the given interval elapses from the start of electrolysis, the controller  21  controls the indicator in the operation/display section  22  to inform the user that the pH of generated ion water is stable. 
     In another modification of the embodiment of this invention, the actual dc voltage applied between the electrodes  9  and  10  is detected by a voltage sensor directly coupled with voltage feed lines to the electrodes  9  and  10 . In addition, the voltage sensor is followed by an averaging circuit (a smoothing circuit) which informs the controller  21  of a mean value of the actual dc voltage.