Abstract:
Tableware (F) put inside a heating chamber ( 20 ) of the disclosed heat cooking device ( 1 ) is heated by means of high-frequency waves, steam, hot air, or a combination thereof. The heating chamber is provided with a circulating fan ( 51 ) and an air supply/emission fan ( 31 ). An air supply tube ( 36 ) to the heating chamber and an air emission tube ( 37 ) from the heating chamber are provided to a blowing duct ( 33 ) that links the air supply/emission fan and an emission port ( 32 ). An ion generator ( 44 ) is disposed at the air supply tube. A duct switching device ( 40 ) that selects whether to introduce positive/negative ions generated by the ion generator into the heating chamber or to release the ions to the outside of the heat cooking device is provided to the air supply tube and the air emission tube.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a cooking device. 
       BACKGROUND ART 
       [0002]    What bothers a user of an oven-type cooking device is, for example, odors remaining in a heating chamber. Odors may come from food to be cooked, or, dirt adhering on surfaces inside the heating chamber may be the source of odors. Such dirt can be hotbeds of various germs. 
         [0003]    There have been proposed cooking devices equipped with means to deal with such odors and dirt. For example, a cooking device disclosed in Patent Literature 1 blows radicalized steam into a heating chamber to act on odors from an object to be cooked, and dirt and germs in the heating chamber, to thereby maintain the quality of the object to be cooked. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1 JP-A-2006-3029 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    A cooking device disclosed in Patent Literature 1 uses radicalized steam to deodorize and sterilize the heating chamber. A portion hit by the steam is heated and humidified. The heating and humidification in this way is not always desirable for all objects to be deodorized or sterilized. It even might be better for some objects to refrain from being heated or humidified. 
         [0006]    The present invention has been made in view of the foregoing, and an object of the present invention is to provide a cooking device capable of deodorizing and sterilizing a heating chamber or an article placed therein without heating and humidification. 
       Solution to Problem 
       [0007]    According to a preferable embodiment of the present invention, a cooking device includes a heating chamber, air inflow path through which air is made to flow into the heating chamber, and an ion generator which emits positive and negative ions into air that flows through the air inflow path. 
         [0008]    According to another preferable embodiment of the present invention, the cooking device having the above configuration further includes a flow path switching device which outwardly discharges air that flows through the air inflow path and includes positive and negative ions. 
         [0009]    According to still another preferable embodiment of the present invention, in the cooking device having the above configuration, an airflow in the air inflow path is generated by a fan, and the fan and the ion generator are able to be driven regardless of whether cooking is performed or not. 
         [0010]    According to still another preferable embodiment of the present invention, in the cooking device having the above configuration, a circulation duct which circulates air in the heating chamber is provided outside the heating chamber, the circulation duct functioning as part of the air inflow path. 
         [0011]    According to still another preferable embodiment of the present invention, in the cooking device having the above configuration, the ion generator is disposed outside the circulation duct. 
         [0012]    According to still another preferable embodiment of the present invention, in the cooking device having the above configuration, the ion generator is disposed inside the circulation duct. 
         [0013]    According to still another preferable embodiment of the present invention, the cooking device having the above configuration further includes a heater which heats gas that flows into the heating chamber. 
         [0014]    According to still another preferable embodiment of the present invention, the cooking device having the above configuration further includes a steam generator which supplies steam into the heating chamber. 
         [0015]    According to still another preferable embodiment of the present invention, the cooking device having the above configuration further includes a microwave generator which supplies a microwave into the heating chamber. 
       Advantageous Effects of Invention 
       [0016]    According to the present invention, positive and negative ions are supplied to air that flows into a heating chamber such that deodorization and sterilization are achieved by actions of positive and negative ions. Thus, it is possible to deodorize and sterilize the heating chamber or an article placed therein while not necessarily applying heat or humidity. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a front view showing a first embodiment of a cooking device according to the present invention; 
           [0018]      FIG. 2  is a vertical sectional view schematically showing the cooking device as viewed from a front side; 
           [0019]      FIG. 3  is a vertical sectional view schematically showing the cooking device as viewed from the front side, in a different state from  FIG. 2 ; 
           [0020]      FIG. 4  is a front view of an operation portion of the cooking device; 
           [0021]      FIG. 5  is a block diagram showing a configuration of the cooking device; 
           [0022]      FIG. 6  is a first flow chart for illustrating an operation of the cooking device; 
           [0023]      FIG. 7  is a second flow chart for illustrating an operation of the cooking device; and 
           [0024]      FIG. 8  is a vertical sectional view schematically showing a second embodiment of a cooking device according to the present invention illustrated in the same manner as  FIG. 3 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    Hereinafter, with reference to the accompanying drawings, a description will be given of a configuration of a cooking device  1 . In  FIG. 1 , the top and the bottom of the sheet coincide with the top and the bottom of the cooking device  1 . As for the right side and the left side of the cooking device  1 , it is defined that the left side and the right side of the sheet coincide with the left side and the right side of the cooking device  1 , respectively. 
         [0026]    The cooking device  1  is provided with a housing  10  which is a rectangular parallelepiped structure made of sheet metal. Inside the housing  10 , there is provided a heating chamber  20  which is a rectangular parallelepiped structure made of sheet metal and one size smaller than the housing  10 . The heating chamber  20  has an opening portion formed at a portion thereof corresponding to the front side of the housing  10 . A door  11  made of metal is provided at the front side of the housing  10  to open and close the opening portion of the heating chamber  20 . The door  11  is rotatable in a perpendicular plane around a bottom end thereof, such that the door  11  can be moved by 90° from a perpendicular fully-closed position to a horizontal fully-open position by holding a handle  12  provided at an upper portion thereof to pull the door  11  frontward. 
         [0027]    In the door  11 , a window  13  is formed for seeing inside of the heating chamber  20  therethrough. The window  13  has fitted therein a door screen  14  formed of two glass sheets and a perforated metal sheet held between the two glass sheets, such that it is possible to prevent leakage of the microwave through the window  13  while achieving the visibility of the inside of the heating chamber  20  through the window  13 . Besides the door screen  14 , the door  11  is provided with other measures for preventing leakage of the microwave. A gasket is disposed between the door  11  and the heating chamber  20  for preventing leakage of gas. The door  11  is provided with a biasing device or a locking device which functions to keep the door  11  in a closed state. These configurations are all well-known technologies, and thus, detailed descriptions thereof will be omitted. 
         [0028]    Steam from a food material that is being cooked or steam used for cooking is sometimes condenses on an inner surface of the door  11 . In order to prevent condensed water from dripping down to wet where the cooking device  1  is located, a drip pan  15  is disposed under the door  11 . 
         [0029]    In the housing  10 , there is formed an operation portion  16  to the right of the door  11 . An operation portion cover  16   a  which is part of the housing  10  includes operational interfaces such as a group of operation keys  16   b  and an encoder dial  16   c . A display portion  16   d  is disposed above the operation keys  16   b.    
         [0030]    The operation portion  16  is illustrated in detail in  FIG. 4 . The operation keys  16   b  include the following four kinds of keys. That is, a kitchen sterilization key  16   b   1 , a cancel key  16   b   2 , a return key  16   b   3 , and a start key  16   b   4 . An enter key  16   e  is provided at a center of the encoder dial  16   c . Small circles illustrated inside the kitchen sterilization key  16   b   1 , the start key  16   b   4 , and the enter key  16   e  indicate LED lamps each provided to indicate that an operation started by pressing on the button is going on. 
         [0031]    The housing  10  is supported on a table top or on some platform via leg portions  17 . The leg portions  17  are disposed one at each of right and left sides of both of front and rear sides, whereby four point support is achieved. 
         [0032]    An internal configuration of the cooking device  1  will be described. Two kinds of fans are disposed outside of a side wall on a right side (hereinafter, a “right side wall”) of the heating chamber  20 . One is an air supply/discharge fan  31 , and the other is a circulation fan  51 . The air supply/discharge fan  31  takes in air from outside the housing  10 , and discharges the air through an outlet port  32  which is formed above a top face of the housing  10 . The air is discharged after passing through the heating chamber  20  or without passing through the heating chamber  20 . The circulation fan  51  circulates gas existing inside the heating chamber  20 . 
         [0033]    A description will be given of an air supply/discharge passage  30  which includes the air supply/discharge fan  31  and the outlet port  32  as components. A main part of the air supply/discharge passage  30  is a ventilation duct  33 . The ventilation duct  33  extends vertically so as to couple a fan casing  34 , in which the air supply/discharge fan  31  is housed, to the outlet port  32 . The ventilation duct  33  has an ejector portion  35  which is disposed a little below the outlet port  32 . 
         [0034]    An air supply pipe  36  horizontally extends from a portion of the ventilation duct  33   a  little below the ejector portion  35 , and the air supply pipe  36  functions as an air inflow path through which air flows into the heating chamber  20 . An air discharge pipe  37  horizontally extends from the ejector portion  35 , and the air discharge pipe  37  functions as an air outflow path through which air flows out from the heating chamber  20 . The air supply pipe  36  is connected to an outlet port  21  which is formed in the right side wall of the heating chamber  20 . The air discharge pipe  37  is connected to an inlet port  22  which is also formed in the right side wall of the heating chamber  20 . The outlet port  21  and the inlet port  22  are both formed of a plurality of small holes. 
         [0035]    An air supply damper  38  is provided at some midpoint in the air supply pipe  36 . An air discharge damper  39  is provided at some midpoint in the air discharge pipe  37 . The air supply damper  38  and the air discharge damper  39  are both electrically driven, and together form a flow path switching device  40 . A return pipe  41  is connected to the air supply damper  38 , and the return pipe  41  is also connected to the ejector portion  35 . An inlet pipe  42  is connected to the air discharge damper  39 , and the inlet pipe  42  sucks in air from outside the housing  10 . 
         [0036]    The air supply damper  38  is switchable between first and second states. In the first state, the air supply damper  38  opens a flow path from the ventilation duct  33  to the outlet port  21  and shuts a flow path to the return pipe  41 . In the second state, the air supply damper  38  closes the flow path from the ventilation duct  33  to the outlet port  21  and opens the flow path to the return pipe  41 . The first state is defined as an “open” state of the air supply damper  38 , and the second state is defined as a “closed” state of the air supply damper  38 . 
         [0037]    The air discharge damper  39  is switchable between first and second states. In the first state, the air discharge damper  39  opens a flow path from the inlet port  22  to the ventilation duct  33  and shuts a flow path from the inlet pipe  42 . In the second state, the air discharge damper  39  shuts the flow path from the inlet port  22  to the ventilation duct  33  and opens the flow path from the inlet pipe  42 . The first state is defined as an “open” state of the air discharge damper  39 , and the second state is defined as a “closed” state of the air discharge damper  39 . 
         [0038]    To the ejector portion  35 , there is also connected an air discharge pipe  43  which extends from an outlet port  23  which is provided near the bottom portion of the heating chamber  20 . 
         [0039]    An ion generator  44  is provided in the air supply pipe  36 , at a position between the ventilation duct  33  and the air supply damper  38 . The ion generator  44  emits positive and negative ions into air flowing through the air supply pipe  36 . 
         [0040]    An absolute humidity sensor  45  is provided in the air discharge pipe  37 , at a position between the air discharge damper  39  and the ejector portion  35 . The absolute humidity sensor  45  measures humidity of air flowing through the air discharge pipe  37 . 
         [0041]    A description will be given of a circulation passage  50  which includes the circulation fan  51  as a component. A main part of the circulation passage  50  is a circulation duct  52  which is provided outside the heating chamber  20 . The circulation duct  52  has a start point at an inlet port  24  formed in the right side wall of the heating chamber and has an end point at outlet ports  25 U,  25 D provided in a left side wall of the heating chamber  20 . Part of the circulation duct  52  between the start and end points thereof is located above the top face of the heating chamber  20 . The inlet port  24  and the outlet ports  25 U,  25 D are all formed of a plurality of small holes. 
         [0042]    Inside the circulation duct  52 , at a position facing the inlet port  24 , there is formed a fan casing  53  in which the circulation fan  51  is accommodated. A temperature sensor  54  is disposed between the inlet port  24  and the fan casing  53 . 
         [0043]    The cooking device  1  is capable of performing microwave cooking, hot air cooking, steam cooking, and combination of these. Descriptions will be given of configurations of the various heating means. 
         [0044]    In a space between a bottom portion of the heating chamber  20  and a bottom portion of the housing  10 , there are disposed a magnetron  60  and a waveguide  61  through which microwave from the magnetron  60  is supplied to the heating chamber  20 . The waveguide  61  is connected to an antenna chamber  62  which is formed under the bottom portion of the heating chamber  20 . A bottom tray  63  is fitted to the bottom portion of the heating chamber  20 , the bottom tray being formed of a dielectric substance such as glass or ceramic. The bottom tray  63  separates the antenna chamber  62  from the heating chamber  20 . The bottom tray  63  serves both as a bottom panel of the heating chamber  20  and a top panel of the antenna chamber  62 . 
         [0045]    A rotary antenna  64  is disposed in the antenna chamber  62 . The rotary antenna  64  is attached to a top end of a shaft  65   a  of an antenna motor  65 . The rotary antenna  64  is caused to continuously rotate in a horizontal plane by rotation of the antenna motor  65 , meanwhile controlling the distribution of a microwave in the heating chamber  20 . 
         [0046]    Hot air cooking is achieved by a gas heating heater  56  which is disposed inside the circulation duct  52 . A portion of the circulation duct  52  above the top face of the heating chamber  20  is formed as a gas heating heater chamber  57 , in which the gas heating heater  56  is disposed. A large number of outlet ports  58  are formed in a dispersed manner in the plate member which functions both as a bottom portion of the gas heating heater chamber  57  and a ceiling portion of the heating chamber  20 . 
         [0047]    Steam cooking is achieved by a steam generator  70  which is disposed outside the right side wall of the heating chamber  20 . The steam generator  70  boils water put therein by using a steam generating heater  71  to thereby generate saturated steam. A steam supply pipe  72  which extends from the steam generator  70  is connected to the circulation duct  52 . The connection is made at an upstream side of the fan casing  53 . 
         [0048]    A control system for the cooking device  1  is configured as shown in  FIG. 5 . A control device  80  which controls the entire cooking device  1  is built with a microcomputer as a core. The control device  80  receives output signals from various components, and transmits control signals to various components. 
         [0049]    The components which transmits output signals to the control device  80  include the operation portion  16  (excluding the display portion  16   d ), the absolute humidity sensor  45 , and the temperature sensor  54 , and in addition to these which have already been mentioned above, the following are also included. That is, a door open/closed state sensor  11   a  which detects whether the door  11  is in an open state or in a closed state, a water level sensor  70   a  which measures a water level in the steam generator  70 , and a tank water level sensor  73  which measures a water level in an unillustrated water tank. 
         [0050]    The components which operate by receiving control signals from the control device  80  include the display portion  16   d , the air supply/discharge fan  31 , the air supply damper  38 , the air discharge damper  39 , the ion generator  44 , the circulation fan  51 , the antenna motor  65 , and the gas heating heater  56 , and in addition to these which have already been mentioned above, the following are also included. That is, a microwave drive power supply  66  which energizes the magnetron  60 , and a water supply pump  74  which supplies water from the unillustrated water tank to the steam generator  70 . 
         [0051]    Operations of the cooking device  1  will now be described. First, the door  11  is opened, and food F as a target to be cooked is place in the heating chamber  20 . Then, the door  11  is closed, cooking conditions are input via the operation portion  16 , and the start key  16   b   4  is pressed on, when cooking starts to be performed. 
         [0052]      FIG. 2  shows a situation where microwave cooking is performed. The food F is placed on a plate  26  on the bottom tray  63 . Here, the microwave drive power supply  66 , the air supply/discharge fan  31 , and the antenna motor  65  are turned on. The air supply damper  38  and the air discharge damper  39  are both in the open states. 
         [0053]    When the microwave drive power supply  66  is turned on, the magnetron  60  starts oscillating, and thereby a microwave is generated. The thus generated microwave enters the antenna chamber  62  through the waveguide  61 . On entering the antenna chamber  62 , the microwave is received by the antenna  64 , and then, the microwave is emitted into the heating chamber  20  through the bottom tray  63 , to heat the food F in the heating chamber  20 . 
         [0054]    When the air supply/discharge fan  31  is turned on, air is sucked into the fan casing  34  from outside the housing  10 . The air is then sent from the fan casing  34  toward the outlet port  32 , but part of the air enters the air supply pipe  36 , to be blown into the heating chamber  20  through the outlet port  21 . Thus, the air supply pipe  36  serves as an air inflow path through which air is made to flow into the heating chamber  20 . 
         [0055]    An airflow toward the outlet port  32  causes negative pressure in the ejector portion  35 , and thanks to the negative pressure, air inside the heating chamber  20  is sucked out from the heating chamber  20 . The air is sucked out from the heating chamber  20  via two routes, that is, a route from the inlet port  22  through the air discharge pipe  37 , and a route from the outlet port  23  through the air discharge pipe  43 . The sucked-out air joins a main stream of the airflow flowing through the ventilation duct  33 , to be discharged to the outside of the casing  10  through the outlet port  32 . 
         [0056]    Thus, fresh air outside the casing  10  is supplied to the heating chamber  20 . Air inside the heating chamber  20  that contains steam and odors from the food F is sucked out from the heating chamber  20  into the ejector portion  35 , and the air is then diluted with outside air that flows upward through the ventilation duct  33 , to be discharged to the outside of the casing  10 . 
         [0057]      FIG. 3  shows a situation where superheated-steam cooking is performed. The food F is supported on a rack  28  made of a metal wire material above a metal tray  27 . The tray  27  has two opposing side edges thereof supported by unillustrated tray holders which are respectively formed on the right and left side walls of the heating chamber  20 . The tray holders are formed at a height between the outlet port  25 U and the outlet port  25 D. 
         [0058]    In this situation, the steam generating heater  71 , the gas heating heater  56 , and the circulation fan  51  are on. The air supply damper  38  and the air discharge damper  39  are each in the closed state. 
         [0059]    When the circulation fan  51  is turned on, a circulating airflow is formed such that air is sucked out from the heating chamber  20  through the inlet port  24  to flow through the circulation duct  52  to return to the heating chamber  20  via the outlet ports  25 U,  25 D. That is, the circulation passage  50  is part of the air inflow path through which air is made to flow into the heating chamber  20 . Saturated steam generated by boiling water in the steam generator  70  is sent to the circulation duct  52  through the steam supply pipe  72  to join the circulating airflow, and flows toward the gas heating heater  56 . 
         [0060]    The saturated steam hits the gas heating heater  56  in a heat generating state to be heated to become superheated steam. Part of the superheated steam is blown downward from the outlet ports  58  into the heating chamber  20  to surround the food F. The rest of the superheated steam is blown from the outlet ports  25 U,  25 D into the heating chamber  20  to surround the food F. The food F surrounded by the superheated steam is cooked by receiving heat both as heat of the superheated steam itself and as latent heat that becomes sensible when the superheated steam comes in contact with a surface of the food F to condense into liquid water. Steam in the heating chamber  20  repeatedly circulates such that it is sucked out from the heating chamber  20  through the inlet port  24  and returns to the heating chamber  20  through the outlet ports  58 ,  25 U, and  25 D. 
         [0061]    Excess air or steam in the heating chamber  20  flows through the air discharge pipe  43  to be discharged from the outlet port  32 . As the air inside the heating chamber  20  is replaced with steam, the inside of the heating chamber  20  becomes hypoxic. This makes it possible to cook the food F without ruining its taste. The superheated steam that comes in contact with the surface of the food F condenses into liquid water and drips down into the tray  27 , meanwhile dissolving oil/fat and salt contained in the food F, and thus it is possible to achieve low-fat, low-salt cooking. 
         [0062]    Steam cooking with saturated steam can be performed by turning on only the steam generating heater  71  and the circulation fan  51  and turning off the gas heating heater  56 . Hot air cooking can be performed by turning on only the steam heating heater  56  and the circulation fan  51  and turning off the steam generating heater  71 . 
         [0063]    Superheated-steam cooking, steam cooking with saturated steam, and hot air cooking can each be performed in combination with microwave cooking. 
         [0064]    In the cases of cooking performed by using superheated steam or saturated steam, if the air supply/discharge fan  31  is turned on, steam that enters the ejector portion  35  from the air discharge pipe  43  is diluted with air flowing in the ventilation duct  33  to be cooled down and thus safe. Furthermore, relative humidity is lowered by the dilution with the air, and this helps reduce dew condensation on surrounding walls. 
         [0065]    After a sequence of microwave cooking, superheated-steam cooking, steam cooking with saturated steam, hot air cooking, or cooking in combination of these, the door  11  is opened. Then, the food F is taken out from the heating chamber  20 . 
         [0066]    When the air supply damper  38  and the air discharge damper  39  are open and the air supply/discharge fan  31  is on, that is, in microwave cooking, if the ion generator  44  is turned on, positive and negative ions are introduced into the heating chamber  20 . In  FIG. 2 , black solid arrows each indicate an airflow containing positive and negative ions. 
         [0067]    When a voltage of an AC waveform or an impulse waveform is applied to an unillustrated electrode in the ion generator  44 , if the applied voltage is a positive voltage, positive ions mainly including H + (H 2 O) n  are generated, while, if the applied voltage is a negative voltage, negative ions mainly including O 2   − (H 2 O) m  are generated. Here, n, m are integer numbers. H + (H 2 O) n  and O 2   − (H 2 O) m  ions surround microorganisms existing in the heating chamber  20 , and collect on surfaces of the microorganisms. 
         [0068]    When H + (H 2 O) n  meets O 2   − (H 2 O) m , they go through chemical reactions represented by the following formulae (1) to (3), to generate [.OH] (hydroxyl radical) and H 2 O 2  (hydrogen peroxide), which are active species. 
         [0000]      H + (H 2 O) n +O 2   − (H 2 O) m →.OH+½O 2 +( n+m )H 2 O  (1)
 
         [0000]      H + (H 2 O) n +H + (H 2 O) n′ +O 2   − (H 2 O) m +O 2   − (H 2 O) m′ →2.OH+O 2 +( n+n′+m+m′ )H 2 O  (2)
 
         [0000]      H + (H 2 O) n +H + (H 2 O) n′ +O 2   − (H 2 O) m +O 2   − (H 2 O) m′ →H 2 O 2 +( n+n′+m+m′ )H 2 O  (3)
 
         [0069]    [.OH] and H 2 O 2  have extremely high activity, and thus it is possible to perform sterilization by using their activity. 
         [0070]    [.OH] acts on a C—C bond, a C═C bond, a C═O bond, and the like of odor-causing organic compounds to decompose such bonds. This generates a deodorization effect. The following formulae (4) to (6) each represent decomposition of a typical odor-causing substance. 
         [0071]    Reaction with acetic acid: 
         [0000]      CH 3 COOH+8.OH→2CO 2 +6H 2 O  (4)
 
         [0072]    Reaction with acetaldehyde: 
         [0000]      CH 3 CHO+10.OH→2CO 2 +7H 2 O  (5)
 
         [0073]    Reaction with benzene: 
         [0000]      C 6 H 6 +30.OH→6CO 2 +18H 2 O  (6)
 
         [0074]    Thus, by introducing highly concentrated positive and negative ions exclusively into the heating chamber  20  by the flow path switching device  40  which is composed of the air supply damper  38  and the air discharge damper  39 , it is possible to remove microorganisms floating in an interior space of the heating chamber  20  or adhering on surfaces of the heating chamber  20  and the food F. Furthermore, it is possible to perform deodorization by decomposing odor-causing substances floating in the interior space of the heating chamber  20  or adhering on the surfaces of the heating chamber  20  and the food F. Incidentally, the concentrations of the positive and negative ions measured at a center portion of the interior space of the heating chamber  20  in this case were each approximately 400,000 ions/cc, which is sufficiently high for sterilization and deodorization. 
         [0075]    Table 1 below shows results of experiments conducted to confirm the deodorization effect. In the experiments, a clove of garlic was heated in a heating chamber for two minutes by using a microwave at power of 600 W. The heating was followed by continuous 10-minute ventilation of air into the heating chamber, with or without supply of positive and negative ions into the air. Subsequently, sensory tests were conducted to evaluate odors remaining in the heating chamber after the 10-minute ventilation, with respect to cases both with and without the supply of positive and negative ions. According to the results of the sensory tests, no odor remained in the cases where the positive and negative ions were supplied, but some odors remained in the cases where the positive and negative ions were not supplied. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Residual odor in the heating chamber 
               
               
                 Positive and negative ions were continuously supplied to the heating 
               
               
                 chamber for 10 minutes, then after 5 minutes of rest thereafter, sensory 
               
               
                 tests were conducted to compare the cases with respect to remaining odors. 
               
             
          
           
               
                   
                 Heating a garlic clove in 
                 With vinegar 
               
               
                   
                 a range at 
                 thinly applied inside a 
               
               
                   
                 600 W for 2 minutes 
                 heating chamber 
               
               
                   
                   
               
             
          
           
               
                 Ion generator: ON 
                 Hardly any odors remained. 
                 Hardly any odors 
               
               
                   
                   
                 remained. 
               
               
                 Ion generator: OFF 
                 Odors slightly remained. 
                 Odors remained. 
               
               
                   
               
             
          
         
       
     
         [0076]    Part of positive and negative ions introduced into the heating chamber  20  is sucked out from the heating chamber  20  into the ejector portion  35 , to join the main stream of the airflow flowing through the ventilation duct  33  to be discharged to the outside of the housing  10  through the outlet port  32 . By the rest of the positive and negative ions, odors adhered to the air discharge passage are also removed. However, some of positive and negative ions in the air discharged from the heating chamber  20  to an outside space via the air discharge passage were lost on their way, and thus the concentrations of positive and negative ions were both reduced to approximately 8,000 ions/cc when measured immediately after the air was discharged from the outlet port  32 . The concentrations of positive and negative ions are high enough to sterilize the discharged gas itself, but not high enough to sterilize an entire kitchen. 
         [0077]    Radicals generated when positive ions meet negative ions are safer and live longer than such radicals as ozone, superoxide anion, hypochlorous acid, and the like. Thus, it is possible to supply radicals to every corner inside the heating chamber  20 . 
         [0078]    When cooking is performed, moisture evaporating from the food F causes the humidity inside and outside the heating chamber  20  to rise. Moisture, which causes humidity, functions to carry radicals, making it easier for the radicals to be delivered to every corner. 
         [0079]    Introduction of positive and negative ions into the heating chamber  20  may be automatically performed along with heating by the microwave, or may be performed by being selected through a key operation on the operation portion  16 . For example, the kitchen sterilization key  16   b   1  can be assigned to it. 
         [0080]      FIG. 6  shows an operation flow of introducing positive and negative ions into the heating chamber  20  while performing microwave cooking. Now, a description will be given of the operation flow. 
         [0081]    In step # 101 , the air supply damper  38  and the air discharge damper  39  are each in an open state. 
         [0082]    In step # 102 , the air supply/discharge fan  31 , the ion generator  44 , and the microwave drive power supply  66  are turned on, such that the food F starts to be heated and positive and negative ions start to be introduced into the heating chamber  20 . 
         [0083]    In step # 103 , it is checked whether a predetermined time (t 1 ) set as a microwave heating time has passed or not. When the predetermined period time is found to have passed, the flow proceeds to step # 104 . 
         [0084]    In step # 104 , it is notified that the cooking is finished. Also, the microwave drive power supply  66  is turned off. The air supply/discharge fan  31  and the ion generator  44  remain on. Thus, the following operations continue to be performed, that is, discharging air in the heating chamber  20  containing steam and odors from the food F, eliminating microorganisms floating in the interior space of the heating chamber  20  or adhering on the surfaces of the heating chamber  20  and of the food F, and decomposing odor-causing substances floating in the interior space of the heating chamber  20  or adhering on the surfaces of the heating chamber  20  and of the food F. 
         [0085]    In step # 105 , it is checked whether a predetermined time (t 2 ) set as an on-state lasting time for the air supply/discharge fan  31  and the ion generator  44  has passed or not. When the predetermined (t 2 ) is found to have passed, the flow proceeds to step # 106 . 
         [0086]    In step # 106 , the air supply/discharge fan  31  and the ion generator  44  are turned off. Thereby, the microwave cooking is completely finished. 
         [0087]    The ion generator  44  and the air supply/discharge fan  31  can be turned on while cooking is performed with the air supply damper  38  and the air discharge damper  39  each in the closed state, that is, while superheated-steam cooking, steam cooking with saturated steam, or hot air cooking is performed. As shown in  FIG. 3 , in this mode, positive and negative ions are introduced not into the heating chamber  20  but into the ejector portion  35 , to join the main stream of the airflow flowing through the ventilation duct  33  to be discharged through the outlet port  32 . That is, positive and negative ions are discharged into a space outside the cooking device  1  to sterilize and deodorize the space. In  FIG. 3 , black solid arrows indicate an airflow containing positive and negative ions, while shaded arrows indicate a circulating airflow. 
         [0088]    In the mode shown in  FIG. 3 , positive and negative ions are supplied only to the space outside the cooking device  1  by the flow path switching device  40  composed of the air supply damper  38  and the air discharge damper  39 . Thus, it is possible to discharge highly concentrated positive and negative ions into the space outside the cooking device  1 . Incidentally, the concentrations of positive and negative ions contained in air measured immediately after the air was discharged from the outlet port  32  were each approximately 200,000 ions/cc. These concentrations of positive and negative ions are higher than those obtained in the mode shown in  FIG. 2 , and high enough not only to sterilize and deodorize the discharged air itself, but also to sterilize and deodorize the entire kitchen. 
         [0089]    Radicals generated when positive ions meet negative ions are safer and live longer than such radicals as ozone, superoxide anion, hypochlorous acid, and the like. Thus, if the cooking device  1  is located in a kitchen, radical can be supplied to every corner of the kitchen. 
         [0090]    The provision of the flow path switching device  40  makes it possible to supply positive and negative ions exclusively into the heating chamber  20 , or, exclusively to the space outside the cooking device  1 . As a result, it is possible to make the concentrations of positive and negative ions higher than those in a case without the flow path switching device  40  where positive and negative ions are dividedly supplied simultaneously into the heating chamber  20  and to the space outside the cooking device  1 . Therefore, it is possible to achieve enhanced sterilization and deodorization both in the heating chamber  20  and in the space outside the cooking device  1 . 
         [0091]    The discharge of positive and negative ions to the space outside the cooking device  1  is preferably performed automatically along with the superheated-steam cooking, the steam cooking with saturated steam, and the hot air cooking. Or, the discharge may be selected by operating a key in the operation portion  16 . In the case where the discharge can be selected by a key operation on the operation portion  16 , the kitchen sterilization key  16   b   1  can be assigned to it, for example. 
         [0092]    In this embodiment, even when cooking is not performed, the ion generator  44  and the air supply/discharge fan  31  can be turned on by pressing on the kitchen sterilization key  16   b   1 . That is, regardless of the cooking state, it is possible to discharge positive and negative ions to the space outside the cooking device  1  at any desired timing to thereby sterilize and deodorize the space. 
         [0093]      FIG. 7  shows an operation flow of sterilization and deodorization of the space outside the cooking device  1  when cooking is not performed. Now, a description will be given of the operation flow. 
         [0094]    In step # 111 , the air supply damper  38  and the air discharge damper  39  are each in the closed state. 
         [0095]    In step # 112 , the air supply/discharge fan  31  and the ion generator  44  are turned on. Thereby, positive and negative ions start to be discharged to the space outside the cooking device  1 . 
         [0096]    In step # 113 , it is checked whether the door  11  has been opened or not. If the door  11  has been opened, the flow proceeds to step # 117 . 
         [0097]    The fact that the door  11  has been opened means that a user has an intention to do cooking. Therefore, in step # 117 , the air supply/discharge fan  31  and the ion generator  44  are turned off. Then the flow proceeds to step # 118 . 
         [0098]    In step # 118 , it is checked whether a predetermined time has passed or not, or, whether a key other than the kitchen sterilization key  16   b   1  has been operated. If the answer is “YES,” the discharge of positive and negative ions to the space outside the cooking device  1  is finished. 
         [0099]    If the door  11  has not been opened in step # 113 , the flow proceeds to step # 114 . In step # 114 , it is checked whether the cancel key  16   b   2  has been pressed on or not. If the cancel key  16   b   2  has been pressed on, the flow proceeds to step # 116 , but if not, the flow proceeds to step # 115 . 
         [0100]    In step # 115 , it is checked whether a predetermined time set as a positive and negative ions discharging time has passed or not. If the predetermined time has passed, the flow proceeds to step # 116 . 
         [0101]    In step # 116 , the air supply/discharge fan  31  and the ion generator  44  are turned off, and the discharge of positive and negative ions to the space outside the cooking device  1  is finished. 
         [0102]    It is also possible to introduce positive and negative ions into the heating chamber  20  when cooking is not performed. This can be achieved by keeping the air supply damper  38  and the air discharge damper  39  each in the open state and turning on the ion generator  44  and the air supply/discharge fan  31 . By selecting this mode, it is possible to sterilize and deodorize the heating chamber  20  when cooking is not performed. It is also possible to sterilize and deodorize the food F or other articles placed in the heating chamber  20  without any application of heat at all. 
         [0103]    In the first embodiment shown in  FIG. 1  to  FIG. 6 , the ion generator  44  is disposed outside the circulation passage  50 . By being thus disposed, the ion generator  44  is protected against heat from the airflow flowing in the circulation passage  50 , or greasy fumes or moisture included in the airflow. However, with provision of sufficient safeguards against heat, greasy fumes, and moisture, it is possible to dispose the ion generator  44  in the circulation passage  50 . An example having such a configuration is shown in  FIG. 8  as a second embodiment. 
         [0104]    In the second embodiment, the ion generator  44  is placed at a slightly upstream side of the gas heating heater chamber  57  inside the circulation duct  52 . It is possible to introduce positive and negative ions into the heating chamber  20  when the circulation fan  51  is in operation, that is, during any of the superheated-steam cooking, the steam cooking with saturated steam, and hot air cooking, 
         [0105]    As in the superheated-steam cooking, the steam cooking with saturated steam, and hot air cooking, if the air supply damper  38  and the air discharge damper  39  are each kept in the closed state and the ion generator  44  inside the circulation duct  52  is driven in the mode where the circulation fan  51  is driven, positive and negative ions are supplied exclusively into the heating chamber  20 . As a result, highly concentrated positive and negative ions can be introduced into the heating chamber  20 . 
         [0106]    When the superheated-steam cooking or the steaming cooking with saturated steam is performed, moisture stays inside the heating chamber  20 , and in addition, ambient humidity around the cooking device  1  rises. Even in such a situation, if positive and negative ions are discharged and generate radicals, it is possible to reduce growth of mold inside and outside the heating chamber  20 . 
         [0107]    In the microwave cooking as well, by turning on the ion generator  44  and the circulation fan  51 , it is possible to introduce positive and negative ions into the heating chamber  20 . Part of positive and negative ions introduced into the heating chamber  20  is sucked out of the heating chamber  20  into the ejector portion  35 , and joins the main stream of the airflow flowing through the ventilation duct  33  to be discharged to the outside of the housing  10  through the outlet port  32 . By the thus discharged positive and negative ions, the space outside the cooking device  1  is also sterilized and deodorized. 
         [0108]    In the second embodiment, even when cooking is not performed, the air supply damper  38  and the air discharge damper  39  can be brought into the open state, and the ion generator  44 , the circulation fan  51 , and the air supply/discharge fan  31  can be turned on, by pressing on the kitchen sterilization key  16   b   1 . That is, regardless of whether cooking is performed or not, it is possible to discharge positive and negative ions to the space outside the cooking device  1  at any desired timing to thereby sterilize and deodorize the space. 
         [0109]    In the second embodiment as well, it is possible to introduce positive and negative ions into the heating chamber  20  when cooking is not performed. This can be achieved, for example, by keeping the air supply damper  38  and the air discharge damper  39  each in the closed state and turning on the ion generator  44  and the circulation fan  51 . By selecting this mode, it is possible to sterilize and deodorize the heating chamber  20  when cooking is not performed. It is also possible to sterilize and deodorize the food F or other articles placed in the heating chamber  20  without any application of heat at all. 
         [0110]    It should be understood that the embodiments specifically described above are not meant to limit the present invention, and that many variations and modifications can be made within the spirit of the present invention. 
       INDUSTRIAL APPLICABILITY 
       [0111]    The present invention is widely applicable to cooking devices. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
         
           
               1  cooking device 
               10  housing 
               11  door 
               20  heating chamber 
               30  air supply/discharge passage 
               31  air supply/discharge fan 
               32  outlet port 
               33  ventilation duct 
               35  ejector portion 
               36  air supply pipe (air inflow path) 
               37  air discharge pipe 
               38  air supply damper 
               39  air discharge damper 
               40  flow path switching device 
               44  ion generator 
               50  circulation passage (air inflow path) 
               51  circulation fan 
               52  circulation duct 
               56  gas heating heater 
               60  magnetron 
               70  steam generator