Abstract:
A steam generating device comprising: a housing ( 2 ) having a cavity therein; a water supply port ( 3 ) open in the housing ( 2 ); a water supply device ( 21 ) for supplying water into the housing ( 2 ) from the water supply port ( 3 ); a steam generating heater ( 4 ) embedded in the housing ( 2 ) and evaporating the water supplied from the water supply port ( 3 ); a discharge port ( 8 ) open in the housing ( 2 ) and discharging the steam generated by the steam generating heater ( 4 ); and a temperature sensor ( 5 ) for detecting the temperature of the housing ( 2 ). The water supply device ( 21 ) is driven when the temperature of the housing ( 2 ) becomes higher than a predetermined driving temperature (T 1 ), and the water supply device ( 21 ) is stopped when the temperature of the housing ( 2 ) becomes lower than a predetermined stop temperature (T 2 ) that is lower than the predetermined driving temperature (T 1 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a steam generating device that generates steam and a cooker using the same. 
       BACKGROUND ART 
       [0002]    Patent Document 1 discloses a cooker using a steam generating device according to the conventional technique. In this cooker, the steam generating device is installed on an outer wall of a heating chamber that houses an object to be cooked. The steam generating device has a housing made of a die casting of a metal such as aluminum. The housing includes a box-shaped main body portion having an open surface on one surface thereof and a lid portion that covers the open surface, so that a cavity is formed inside the housing. 
         [0003]    In the main body portion, a steam generating heater is embedded by molding in upper and lower wall surfaces thereof, and a water supply port is formed at a center portion of a side wall thereof in the vertical direction. The water supply port is connected to a water supply tank via a water supply pump so that water is supplied into the housing through the water supply port. At an upper portion of the lid portion, an ejection port for ejecting steam is provided so as to face toward the inside of the heating chamber. Furthermore, in the main body portion, a plurality of fins for heat exchange and a temperature sensor that detects the temperature in the housing are provided. Some of the fins are each disposed so as to cover the lower side of the ejection port. 
         [0004]    When water is supplied into the steam generating device through the water supply port, the water is stored in a bottom portion of the housing, and steam is generated by driving of the steam generating heater. The steam thus generated ascends in the housing to come in contact with the highly-heated housing wall surfaces and fins and thus is further heated. As a result, the highly-heated steam is ejected into the heating chamber via the ejection port. Using the steam thus supplied into the heating chamber, an object to be cooked is cooked. 
         [0005]    The steam generating device is continuously supplied with water at a predetermined flow rate by the water supply pump, and the temperature in the housing is monitored by the temperature sensor. Heating by the steam generating heater causes water in the housing to be evaporated, and when the temperature in the housing becomes higher than a predetermined temperature, the steam generating heater is deactivated. When, in consequence of water supply, the temperature in the housing becomes lower than the predetermined temperature, the steam generating heater is driven. These operations are performed in repeated cycles, as a result of which steam is ejected through the ejection port. 
       LIST OF CITATIONS 
     Patent Literature 
       [0000]    
       
         Patent Document 1: JP-A-2006-84059 (pages 3 to 8, FIG. 3, and FIG. 6) 
       
     
       SUMMARY OF THE INVENTION 
     Technical Problems 
       [0007]    According to the above-described conventional steam generating device, however, water is continuously supplied by the water supply pump, and the steam generating heater is turned on/off depending on the temperature in the housing. Because of this, water may accumulate to a large amount in the housing during a time from when the steam generating heater is started to be driven to when a heated state thereof is attained. It has been a problem that, in this case, if the water in the housing comes to a boil and bumping thereof occurs, the water spurts out through the ejection port to leak into the heating chamber. Such water leakage into the heating chamber through the ejection port causes water to adhere to an object to be cooked, resulting in a failure to achieve cooking with a good result. Particularly in a case where hard water is supplied through the water supply port, since bumping thereof is highly likely to occur, spurting out of the water through the ejection port occurs to a considerable degree. 
         [0008]    Furthermore, if power supply to the steam generating heater is reduced, the evaporation amount with respect to the amount of water supplied from the water supply pump is decreased. In such a case, the housing is not heated to a temperature at which the steam generating heater is deactivated and is continuously supplied with water. It has also been a problem that this causes water to overflow through the ejection port to leak into the heating chamber. 
         [0009]    Furthermore, among the fins, the ones each disposed on the lower side of the ejection port are provided in the main body portion having the steam generating heater and thus are maintained at a high temperature. Because of this, when bumping of water accumulated in the housing occurs under heating by the steam generating heater and thus carries the water up on the fins, water droplets thereby formed on the fins are brought to a bumping state again. It has also been a problem that this causes water to spurt out through the ejection port to leak into the heating chamber. 
         [0010]    It is an object of the present invention to provide a steam generating device that can prevent water leakage through an ejection port for ejecting steam and a cooker using the same. 
       Solution to the Problems 
       [0011]    In order to achieve the above-described object, a steam generating device according to the present invention includes: a housing having a cavity inside; a water supply port that is open into the housing; a water supply unit that supplies water into the housing through the water supply port; a steam generating heater that is embedded in the housing and evaporates water supplied through the water supply port; an ejection port that is open into the housing and through which steam generated by the steam generating heater is ejected; and a temperature sensor that detects a temperature in the housing. In the steam generating device, when the temperature in the housing becomes higher than a predetermined driving temperature, the water supply unit is driven, and when the temperature in the housing becomes lower than a predetermined deactivation temperature lower than the driving temperature, the water supply unit is deactivated. 
         [0012]    According to this configuration, when water is supplied into the housing through the water supply port by driving of the water supply unit, the water is stored in a bottom portion of the housing, and steam is generated by driving of the steam generating heater. The steam thus generated ascends in the housing and then is ejected through the ejection port. The temperature in the housing is monitored by the temperature sensor, and when the temperature becomes higher than the driving temperature, water is supplied from the water supply unit. When, in consequence of water supply, the temperature in the housing is decreased and becomes lower than the deactivation temperature, the water supply unit is deactivated. 
         [0013]    Furthermore, in the present invention, in the steam generating device configured as above, the deactivation temperature is set to a temperature higher than 100° C. According to this configuration, steam is generated with the temperature in the housing maintained at a temperature higher than 100° C. 
         [0014]    Furthermore, a steam generating device according to the present invention includes: a housing that includes a box-shaped metallic main body portion having an open surface and a lid portion that covers the open surface, so that a cavity is formed inside the housing; a water supply port through which water is supplied into the housing; a steam generating heater that is embedded in the main body portion and evaporates water supplied through the water supply port; an ejection port that is open into the main body portion at a level above the level of the steam generating heater and through which steam generated by the steam generating heater is ejected; and a blocking portion that is disposed between the ejection port and the steam generating heater so as to extend from the lid portion to the vicinity of an inner wall of the main body portion. 
         [0015]    According to this configuration, when water is supplied into the housing through the water supply port, the water is stored in the bottom portion of the housing, and steam is generated by driving of the steam generating heater. The steam thus generated ascends in the housing and then is ejected through the ejection port. Water, which has been brought to a bumping state in the bottom portion of the housing by the steam generating heater, is blocked by the blocking portion. The blocking portion extends from the lid portion at a temperature lower than the temperature at the main body portion, and thus droplets of water that has been carried up on the blocking portion through bumping drip from there on the blocking portion into the housing. 
         [0016]    Furthermore, in the present invention, in the steam generating device configured as above, the lid portion is joined to the main body portion via a gasket. According to this configuration, the gasket provides sealing between the main body portion and the lid portion. Furthermore, heat transfer from the main body portion having the steam generating heater to the lid portion is suppressed. 
         [0017]    Furthermore, in the present invention, in the steam generating device configured as above, the blocking portion is constituted by an inclined surface. According to this configuration, droplets of water that has been carried up on the blocking portion constituted by an inclined surface flows down from there on the blocking portion to drip into the housing. 
         [0018]    Furthermore, in the present invention, in the steam generating device configured as above, the blocking portion has a side surface portion provided in a standing manner on each lateral side of the ejection port and thus has a U-shape in cross section. According to this configuration, water being in a bumping state is blocked by the blocking portion covering the lower side and lateral sides of the ejection port. 
         [0019]    Furthermore, in the present invention, in the steam generating device configured as above, the ejection port protrudes into the housing and overlaps the blocking portion in a planar view. 
         [0020]    Furthermore, in the present invention, in the steam generating device configured as above, a lower inner wall surface of the ejection port is inclined downward in a direction toward the lid portion. According to this configuration, water droplets produced inside the ejection port by condensation resulting from cooling flow down the lower inner wall surface of the ejection port to drip on the blocking portion and then drip from the blocking portion into the housing. 
         [0021]    Furthermore, in the present invention, in the steam generating device configured as above, the water supply port is provided in the lid portion. According to this configuration, the lid portion is cooled by water passing through the water supply port. 
         [0022]    Furthermore, in the present invention, in the steam generating device configured as above, the lid portion is made of ceramic. According to this configuration, the lid portion is decreased in thermal conductivity, and thus heat transfer from the main body portion having the steam generating device to the lid portion is suppressed. 
         [0023]    Furthermore, a cooker according to the present invention includes: the steam generating device having any one of the above-described configurations; a heating chamber that houses an object to be cooked and is supplied with steam through the ejection port; a circulation fan that circulates steam in the heating chamber; and a convection heater that heats steam being circulated by the circulation fan. According to this configuration, cooking is performed using steam that is supplied from the steam generating device into the heating chamber and is circulated by the circulation fan. The steam being circulated by the circulation fan is heated by the convection heater so as to be maintained at a predetermined temperature. 
         [0024]    Furthermore, in the present invention, in the cooker configured as above, respective duty ratios of the steam generating heater and the convection heater are controlled so that a steam generation period in which the steam generating heater is driven and a heating period in which the convection heater is driven are brought about in repeated cycles, and a period in which the water supply unit is driven is synchronized with timing for driving the steam generating heater. 
         [0025]    According to this configuration, the steam generating heater and the convection heater are driven by being supplied with power alternately, so that the steam generation period and the heating period are brought about in repeated cycles. When the temperature in the housing becomes higher than the driving temperature, the water supply unit is driven during the steam generation period in synchronization with the steam generating heater. 
         [0026]    Furthermore, in the present invention, in the cooker configured as above, at a time preceding the completion of cooking by a predetermined length of time, the water supply unit is deactivated regardless of the temperature in the housing. 
         [0027]    Furthermore, in the present invention, in the cooker configured as above, when the temperature in the housing exceeds a predetermined temperature during the predetermined length of time, the steam generating heater is deactivated. 
       Advantageous Effects of the Invention 
       [0028]    According to the present invention, when the temperature in the housing of the steam generating device becomes higher than the predetermined driving temperature, driving of the water supply unit is started, and when the temperature in the housing becomes lower than the predetermined deactivation temperature lower than the driving temperature, the driving of the water supply unit is halted. Thus, water does not accumulate in the housing during a time from when the steam generating heater is started to be driven to when a heated state thereof is attained, so that a phenomenon can be prevented in which the water is brought to a bumping state to spurt out through the ejection port. Furthermore, if power supply to the steam generating heater is reduced and the temperature in the housing thus is decreased, water supply is halted, and thus water can be prevented from overflowing through the ejection port. This can prevent water leakage through the ejection port, thereby allowing cooking to be performed with a good result. 
         [0029]    Furthermore, according to the present invention, the blocking portion is provided that extends from the lid portion covering the open surface of the main body portion in which the steam generating heater is embedded, and the blocking portion is disposed between the ejection port and the steam generating heater so as to extend to the vicinity of an inner wall of the main body portion, and thus water being in a bumping state in a bottom portion of the housing can be blocked by the blocking portion. Furthermore, the blocking portion is provided on the lid portion at a temperature lower than the temperature at the main body portion, and thus droplets of water that has been carried up on the blocking portion through bumping of the water caused in the bottom portion of the housing are not brought to a bumping state on the blocking portion but drip into the housing. This can prevent water leakage through the ejection port, thereby allowing cooking to be performed with a good result. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0030]      FIG. 1  A right side view showing an inside of a cooker according to an embodiment of the present invention. 
           [0031]      FIG. 2  A front view showing the inside of the cooker according to the embodiment of the present invention. 
           [0032]      FIG. 3  A cross-sectional front view showing a steam generating device in the cooker according to the embodiment of the present invention. 
           [0033]      FIG. 4  A cross-sectional view taken on line A-A of  FIG. 3 . 
           [0034]      FIG. 5  A block diagram showing the configuration of the cooker according to the embodiment of the present invention. 
           [0035]      FIG. 6  A timing chart showing respective driving pulses of the steam generating heater, a water supply pump, and a convection heater in the cooker according to the embodiment of the present invention. 
           [0036]      FIG. 7  A flow chart showing the operation of the cooker according to the embodiment of the present invention. 
           [0037]      FIG. 8  A diagram showing variations in temperature in a housing of the steam generating device in the cooker according to the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    Hereinafter, an embodiment of the present invention will be described with reference to the appended drawings.  FIGS. 1 and 2  are a right side view and a front view showing an inside of a cooker according to one embodiment, respectively. A cooker  10  has, in a main body casing  22 , a heating chamber  11  that has substantially a rectangular parallelepiped shape and houses an object to be cooked. The side walls and ceiling wall of the heating chamber  11  are covered with a heat shield plate  23  so as to be thermally shielded, and the front surface of the heating chamber  11  is opened/closed by a door  11   b.    
         [0039]    A temperature sensor  11   c  that detects the room temperature in the heating chamber  11  is provided on the top surface of the heating chamber  11 . Based on a temperature detected by the temperature sensor  11   c , an after-mentioned convection heater  15  is controlled. A tray  17  on which a rack  17   a  is placed is disposed in the heating chamber  11 . An object W to be cooked is placed on the rack  17   a.    
         [0040]    An outside air inflow duct  34  is formed between the heating chamber  11  and the main body casing  22  so as to extend on the lower side and right lateral side of the heating chamber  11 . The outside air inflow duct  34  has a suction port  34   a  that is open on the bottom surface of the main body casing  22 . In a lower portion of the outside air inflow duct  34 , a cooling fan  35 , an electrical equipment portion  33 , and a magnetron  30  are disposed. In a side portion of the outside air inflow duct  34 , an air supply duct  36  having an air supply fan  37  is disposed. The air supply duct  36  has an air supply port  38  that is open at a front portion of a side wall  11   a  that is one of the side walls of the heating chamber  11 . 
         [0041]    The electrical equipment portion  33  has driving circuits that respectively drive various parts of the cooker  10 , a control portion  50  (see  FIG. 5 ) that controls the driving circuits, etc., and a multitude of heat generating elements are mounted in the electrical equipment portion  33 . The magnetron  30  supplies microwaves into the heating chamber  11  via a waveguide  31 . An antenna  32  that is rotated by an antenna motor  32   a  is disposed in the waveguide  31 , and thus microwaves are supplied to the heating chamber  11  in a uniform manner. 
         [0042]    The cooling fan  35  takes outside air into the outside air inflow duct  34  via the suction port  34   a  and thereby cools the electrical equipment portion  33  and the magnetron  30 , which generate heat. The outside air taken into the outside air inflow duct  34  flows out through an opening (not shown) formed on the back surface or the like of the main body casing  22 . Furthermore, driving the air supply fan  37  causes part of the outside air to flow into the air supply duct  36  so as to be supplied to the heating chamber  11  through the air supply port  38 . 
         [0043]    In a back portion of the side wall  11   a  of the heating chamber  11 , an air discharge duct  40  is led out via an air discharge port  41 . The air discharge duct  40  is formed so as to extend to a back side of the heating chamber  11  and has an open end  40   a  that is open on the top surface of the main body casing  22 . Furthermore, a humidity sensor  42  that detects the humidity of exhaust air at the air discharge port  41  is provided in the air discharge duct  40 . 
         [0044]    A steam generating device  1  that supplies steam to the heating chamber  11  via an ejection port  8  is installed at an upper portion of the side wall  11   a  of the heating chamber  11 . A demountable water supply tank  20  is disposed on a lateral side of the steam generating device  1 . A water supply pump  21  (water supply unit) connected to a water supply port  3  (see  FIG. 3 ) of the steam generating device  1  is disposed on a back side of the water supply tank  20 . 
         [0045]    The steam generating device  1  is disposed at the upper portion of the side wall  11   a  of the heating chamber  11 , and the water supply tank  20  is disposed in a lower portion of the main body casing  22 . This prevents water from flowing, under its own weight, from the water supply tank  20  into the steam generating device  1 . The water supply pump  21  is made up of a tube pump and delivers water through a tube  112 . The water supply tank  20  is connected to the water supply pump  21  via a fitting (not shown). Driving the water supply pump  21  causes water to be supplied from the water supply tank  20  into a housing  2  (see  FIG. 3 ) of the steam generating device  1 . 
         [0046]    A circulation duct  12  is provided behind the heating chamber  11 . The circulation duct  12  has an air suction port  14  at a center portion of the back wall of the heating chamber  11  and a plurality of blow-out ports  13  at a portion of the back wall of the heating chamber  11  around the center portion. In the circulation duct  12 , a circulation fan  16  and the convection heater  15  are provided. The circulation fan  16  is driven to be rotated by a fan motor  16   a . The circulation fan  16  sucks steam in the heating chamber  11  into the circulation duct  12  through the air suction port  14  and blows the steam out through the blow-out ports  13 . The convection heater  15  is made up of a ring-shaped sheathed heater disposed around the circulation fan  16  and maintains steam flowing through the circulation duct  12  at a predetermined temperature. 
         [0047]      FIG. 3  shows a cross-sectional front view of the steam generating device  1 .  FIG. 4  shows a cross-sectional view taken on line A-A of  FIG. 3 . The steam generating device  1  has the housing  2  made of a metal die casting. In the housing  2 , an open surface of a box-shaped main body portion  2   a  is closed by a lid portion  2   b  that is joined with a screw  2   c  to the main body portion  2   a , so that a cavity is formed inside the housing  2 . It is preferable that aluminum or an aluminum alloy be used as a material of the housing  2  since they provide good casting performance and have high thermal conductivities. 
         [0048]    A ring-shaped groove  2   d  is formed around the open surface of the main body portion  2   a . A ring-shaped gasket  9  is disposed in the groove  2   d  so as to provide sealing between the main body portion  2   a  and the lid portion  2   b . Since sealing of the housing  2  is achieved with the gasket  9 , respective surfaces of the lid portion  2   b  and the main body portion  2   a  opposed to each other have been processed to have a predetermined degree of roughness, so that minute gaps are formed between the lid portion  2   b  and the main body portion  2   a . This suppresses heat transfer from the main body portion  2   a  having an after-mentioned steam generating heater  4  to the lid portion  2   b.    
         [0049]    In a lower portion of the main body portion  2   a , the steam generating heaters  4  made up of sheathed heaters are arranged in two upper and lower rows. The water supply port  3  connected to the water supply pump  21  (see  FIG. 2 ) is open between the steam generating heaters  4  in the upper and lower rows. The steam generating heaters  4  are embedded by molding in the housing  2  and thus are in close contact with the main body portion  2   a , so that heat of the steam generating heaters  4  is conducted efficiently to the main body portion  2   a . Thus, using heat conducted from the steam generating heaters  4  to the housing  2 , water that is allowed to drip from the water supply port  3  and accumulates in a bottom portion of the housing  2  is evaporated to form steam. 
         [0050]    Furthermore, in a side portion between the steam generating heaters  4  in the upper and lower rows, a temperature sensor  5  that detects the temperature in the housing  2  is embedded by molding. 
         [0051]    In an upper portion of the main body portion  2   a , a plurality of the ejection ports  8  that eject steam are provided so as to face the side wall  11   a  of the heating chamber  11 . Each of the ejection ports  8  protrudes into the housing  2  and has a lower inner wall surface inclined downward in a direction toward the lid portion  2   b . The ejection ports  8  are formed on a plane protruding with respect to a lower portion of the housing  2  in which the steam generating heaters  4  are embedded. Thus, the lower portion of the housing  2 , which is heated to a high temperature by the steam generating heaters  4 , is disposed away from the wall surface  11   a  of the heating chamber  11 . This can simplify a heat-resistant structure of the heating chamber  11 . 
         [0052]    A blocking portion  7  is provided integrally with the lid portion  2   b  so as to protrude toward the inside of the housing  2 . The blocking portion  7  is formed so as to extend to the vicinity of a wall surface of the main body portion  2   a , which is opposed thereto, and a bottom surface  7   a  of the blocking portion  7  is disposed between the ejection ports  8  and the steam generating heaters  4 . Furthermore, the blocking portion  7  has a side surface portion  7   b  provided in a standing manner on each lateral side of the ejection ports  8  and thus has a U-shape in cross section. The bottom surface  7   a  of the blocking portion  7  is formed so as to be inclined downward in a direction away from the lid portion  7   a  and disposed so as to overlap, in a planar view, the ejection ports  8  protruding into the housing  2 . 
         [0053]      FIG. 5  is a block diagram showing the configuration of the cooker  10 . The cooker  10  has the control portion  50  that is disposed in the electrical equipment portion  33  and controls the various parts. The circulation fan  16 , the convection heater  15 , the magnetron  30 , the antenna motor  32   a , the cooling fan  35 , the air supply fan  37 , an operation portion  51 , a display portion  52 , a storage portion  53 , the temperature sensor  11   c , the humidity sensor  42 , and a timer  55  are connected to the control portion  50 . Furthermore, the steam generating heaters  4  of the steam generating device  1 , the water supply pump  21 , and the temperature sensor  5  are controlled by the control portion  50 . 
         [0054]    The timer  55  measures a cooking time, etc. The operation portion  51  is provided on a lateral side of the heating chamber  11  and performs a cooking menu selecting operation, a cooking starting operation, etc. The display portion  52  is made up of a liquid crystal panel, etc. disposed on the lateral side of the heating chamber  11  and displays operation menus, an operating state of the cooker  10 , etc. The storage portion  53  stores databases on operation programs and cooking menus of the cooker  10  and temporarily stores a result of a computation performed by the control portion  50 . 
         [0055]      FIG. 6  is a schematic timing chart showing respective driving pulses of the steam generating heaters  4 , the water supply pump  21 , and the convection heater  15 . Respective duty ratios of the steam generating heaters  4  and the convection heater  15  are controlled. Thus, a steam generation period to in which the steam generating heaters  44  are driven during a predetermined on-time and a heating period tb in which the convection heater  15  is driven during a predetermined on-time are brought about in repeated cycles. 
         [0056]    Furthermore, the water supply pump  21  is driven during the steam generation period ta in synchronization with the steam generating heater  4  and, as will be described later, is deactivated when the temperature in the housing  2  of the steam generating device  1  becomes high. The circulation fan  16  is driven during the heating period tb in synchronization with the convection heater  15 . The circulation fan  16  may also be driven during the heating period tb and during the steam generation period ta in a continuous manner. 
         [0057]    In the cooker  10  configured as above, upon starting of cooking using microwaves, the magnetron  30  and the antenna motor  32   a  are driven. Furthermore, the cooling fan  35  and the air supply fan  37  are also driven. The magnetron  30  supplies microwaves into the heating chamber  11  via the waveguide  31 , and the object W to be cooked is heated using the microwaves. 
         [0058]    Driving the cooling fan  35  causes outside air to flow into the outside air inflow duct  34  through the suction port  34   a . The outside air that has flowed into the outside air inflow duct  34  cools the electrical equipment portion  33  and the magnetron  30  and then is discharged to the outside. Part of the outside air heated as a result of having cooled the electrical equipment portion  33  and the magnetron  30  is guided to the air supply duct  36  by the air supply fan  37 . 
         [0059]    The outside air flowing through the air supply duct  36  is supplied to the heating chamber  11  through the air supply port  38 . At this time, since the air supply port  38  is disposed at a front portion of the heating chamber  11 , the airflow blown out through the air supply port  38  flows along the door  11   b . Thus, using air heated as a result of having cooled the electrical equipment portion  33  and the magnetron  30 , the occurrence of condensation on the door  11   b  can be prevented. 
         [0060]    Upon reception of the air supplied through the air supply port  38 , air in the heating chamber  11  is discharged through the air discharge port  41  to flow through the air discharge duct  40  and then is emitted to the atmosphere through the open end  40   a . The humidity of the air flowing through the air discharge duct  40  is detected by the humidity sensor  42 . Under heating by microwaves, steam is generated from the object W to be cooked, and when the humidity in the heating chamber  11  attains a predetermined value, upon detection thereof by the humidity sensor  42 , it is determined that timing for completing the cooking has come. The cooking using microwaves thus is completed. 
         [0061]    When cooking using steam is performed, the water supply tank  20  storing water is mounted. Then, the object W to be cooked is placed on the rack  17   a , and upon selection of a cooking menu, the cooking is started.  FIG. 7  is a flow chart showing the operation of performing cooking using steam. Furthermore,  FIG. 8  is a diagram showing an example of how the temperature in the housing  2  of the steam generating device  1  varies during cooking. In this figure, the vertical axis indicates a temperature in the housing  2  denoted H (unit: ° C.), and the horizontal axis indicates a time (unit: second). In the figure, P represents a driving pulse of the water supply pump  21 . 
         [0062]    Upon starting of the cooking, at step # 11 , the steam generating heaters  4  are driven. The temperature in the housing  2  thus is increased. At step # 12 , it is determined whether or not the on-time of the steam generating heaters  4  has elapsed. In a case where the on-time of the steam generating heaters  4  has not elapsed yet, steps # 12  to # 18  are performed in repeated cycles, i.e. the steam generation period ta continues. In a case where the on-time of the steam generating heaters  4  has elapsed, a transition is made to step # 21  where switching to the heating period tb is performed. 
         [0063]    At step # 21 , the steam generating heaters  4  and the water supply pump  21  are deactivated. At step # 22 , the convection heater  15  and the circulation fan  16  are driven. At step # 23 , it is determined whether or not the on-time of the convection heater  15  has elapsed. In a case where the on-time of the convection heater  15  has elapsed, at step # 25 , the convection heater  15  and the circulation fan  16  are deactivated, and a transition is made to step # 11  where switching to the steam generation period ta is performed. 
         [0064]    In a case where the on-time of the convection heater  15  has not elapsed yet, at step # 24 , it is determined whether or not a cooking period G 1  (see  FIG. 8 ) has been completed. In a case where the cooking period G 1  has not been completed yet, steps # 23  and # 24  are performed in repeated cycles, i.e. the heating period tb continues. 
         [0065]    In the case where, at step # 12 , it is determined that the on-time of the steam generating heaters  4  has not elapsed yet, a transition is made to step # 13 . At step # 13 , it is determined whether or not a time preceding the completion of the cooking period G 1  by a predetermined length of time (for example, by one minute) has been reached. When the time preceding the completion of the cooking period G 1  by the predetermined length of time is reached, a transition is made to step # 17 . 
         [0066]    In a case where the time preceding the completion of the cooking period G 1  by the predetermined length of time has not been reached yet, a transition is made to step # 14  where it is determined whether or not the temperature in the housing  2  is higher than a predetermined driving temperature T 1  (for example, 125° C.). In a case where the temperature in the housing  2  is not higher than the driving temperature T 1 , a transition is made to step # 16 . When the temperature in the housing  2  becomes higher than the driving temperature T 1  (point E in  FIG. 8 ), at step # 15 , driving of the water supply pump  21  is started. 
         [0067]    Driving the water supply pump  21  causes water to be supplied into the housing  2  of the steam generating device  1  through the water supply port  3  as shown by an arrow B (see  FIG. 3 ). The water supplied to the housing  2  accumulates in the bottom portion of the housing  2  and then is evaporated by the steam generating heaters  4  to form steam. At this time, the water, which has been brought to a bumping state in the bottom portion of the housing  2  by the steam generating heaters  4 , is blocked by the blocking portion  7 . The blocking portion  7  extends from the lid portion  2   b  at a temperature lower than the temperature at the main body portion  2   a . Thus, droplets of water that has been carried up on the blocking portion  7  through bumping are not brought to a bumping state again but flow down from there on the blocking portion  7  along the bottom surface  7   a  as shown by an arrow D 1  (see  FIG. 3 ) to drip into the housing  2 . 
         [0068]    The steam generated in the lower portion of the housing  2  ascends in the housing  2  to exchange heat with the main body portion  2   a  and then is supplied to the heating chamber  11  through the ejection ports  8  as shown by an arrow C (see  FIG. 3 ). At this time, condensation water produced at the ejection ports  8  by condensation resulting from cooling flows down the inclined lower inner wall surface of each of the ejection ports  8  as shown by an arrow D 2  (see  FIG. 3 ) and is allowed to drip on the blocking portion  7  and then into the housing  2 . 
         [0069]    During the heating period tb, the circulation fan  16  is driven to cause the steam supplied into the heating chamber  11  to flow into the circulation duct  12  via the air suction port  14 . The steam flowing through the circulation duct  12  is heated by the convection heater  15  and then is blown out into the heating chamber  11  through the blow-out ports  13 . Thus, steam in the heating chamber  11  is maintained at a predetermined temperature, and the object W to be cocked on the tray  17  is cooked using saturated steam or superheated steam. 
         [0070]    At step # 16 , it is determined whether or not the temperature in the housing  2  is lower than a predetermined deactivation temperature T 2 . The deactivation temperature T 2  is set to be a temperature (for example, 105° C.) lower than the driving temperature T 1 . In a case where the temperature in the housing  2  is not lower than the deactivation temperature T 2 , a transition is made to step # 18 . When the temperature in the housing  2  becomes lower than the deactivation temperature T 2  (point F in  FIG. 8 ), at step # 17 , driving of the water supply pump  21  is halted. This can suppress an increase in the amount of water stored in the housing  2 . 
         [0071]    Furthermore, when the deactivation temperature T 2  is set to a temperature higher than 100° C., which is the boiling point of water, the housing  2  is maintained at a temperature higher than 100° C. This prevents the occurrence of condensation at the ejection ports  8 , thereby allowing prevention of leakage of condensation water to the heating chamber  11 . 
         [0072]    At step # 18 , it is determined whether or not the cooking period G 1  has been completed. In a case where the cooking period G 1  has not been completed yet, steps # 12  to # 18  are preformed in repeated cycles. 
         [0073]    Furthermore, when, at step # 13 , it is determined that the time preceding the completion of the cooking period G 1  by the predetermined length of time has been reached, at step # 17 , the water supply pump  21  is deactivated regardless of the temperature in the housing  2 . This brings about an evaporation period G 2  (see  FIG. 8 ) in which water in the housing  2  is evaporated and thus can prevent the water from remaining in the housing  2 . In this case, a configuration is possible in which if, during the evaporation period G 2 , the temperature in the housing  2  becomes higher than a predetermined temperature (for example, 300° C.), the steam generating heaters  4  are deactivated. This can improve the safety of the cooker  10 . 
         [0074]    When it is determined, at step # 18  or at step # 24 , that the cooking period G 1  has been completed, the steam generating heaters  4 , the convection heater  15 , and the circulation fan  16  are deactivated, and the cooking thus is completed. 
         [0075]    According to this embodiment, when the temperature in the housing  2  of the steam generating device  1  becomes higher than the driving temperature T 1 , driving of the water supply pump  21  (water supply unit) is started, and when the temperature in the housing  2  becomes lower than the deactivation temperature T 2 , the driving of the water supply pump  21  is halted. Thus, water does not accumulate in the housing  2  during a time from when the steam generating heaters  4  are started be driven to when a heated state thereof is attained, so that a phenomenon can be prevented in which the water is brought to a bumping state to spurt out through the ejection ports  8 . Particularly in a case where water stored in the water supply tank  20  is hard water, bumping thereof is highly likely to occur. Even in such a case, however, it is possible to securely prevent the water from spurting out through the ejection ports  8 . 
         [0076]    Furthermore, if power supply to the steam generating heaters  4  is reduced and the temperature in the housing  2  thus becomes lower than the deactivation temperature T 2 , water supply is halted, and thus water can be prevented from overflowing through the ejection ports  8 . This can prevent water leakage through the ejection ports  8 , thereby allowing cooking to be performed with a good result. 
         [0077]    Furthermore, since the deactivation temperature T 2  is set to a temperature higher than 100° C., the occurrence of condensation at the ejection ports  8  is prevented, and thus it is possible to further prevent leakage of condensation water to the heating chamber  11 . 
         [0078]    Furthermore, since respective duty ratios of the steam generating heaters  4  and the convection heater  15  are controlled so that the steam generation period to and the heating period tb are brought about in repeated cycles, steam generation and steam heating can be preformed consecutively, thereby allowing cooking to be performed using steam maintained at a stable temperature. 
         [0079]    Furthermore, since during the evaporation period G 2  preceding the completion of cooking by the predetermined length of time, the water supply pump  21  is deactivated regardless of the temperature in the housing  2 , water can be prevented from remaining in the housing  2 . 
         [0080]    Furthermore, since if, during the evaporation period G 2 , the temperature in the housing  2  exceeds a predetermined temperature, the steam generating heaters  4  are deactivated, and thus the safety of the cooker  10  can be improved. 
         [0081]    Furthermore, since the blocking portion  7  is provided that extends from the lid portion  2   b  covering the open surface of the main body portion  2   a  in which the steam generating heaters  4  are embedded, and the blocking portion  7  is disposed between the ejection ports  8  and the steam generating heaters  4  so as to extend to the vicinity of the inner wall of the main body portion  2   a , water being in a bumping state in the bottom portion of the housing  2  can be blocked by the blocking portion  7 . Furthermore, since the blocking portion  7  is provided on the lid portion  2   b  at a temperature lower than the temperature at the main body portion  2   a , droplets of water that has been carried up on the blocking portion  7  through bumping of the water caused in the bottom portion of the housing  2  are not brought to a bumping state again on the blocking portion  7  but drip into the housing  2 . This can prevent water leakage through the ejection ports  8 , thereby allowing cooking to be performed with a good result. 
         [0082]    Particularly in a case where hard water is supplied through the water supply port  3 , bumping thereof is highly likely to occur. Even in such a case, however, the blocking portion  7  provided on the lid portion  2   b  can securely prevent water from spurting out through the ejection ports  8 . 
         [0083]    Furthermore, since the lid portion  2   b  is joined to the main body portion  2   a  via the gasket  9 , sealing between the lid portion  2   b  and the main body portion  2   b  is provided, and heat transfer from the main body portion  2   a  to the lid portion  2   b  is suppressed. This maintains the blocking portion  7  at a further decreased temperature, and thus it is possible to securely prevent water from spurting out through the ejection ports  8 . 
         [0084]    Furthermore, since the blocking portion  7  has the side surface portion  7   b  provided in a standing manner on each lateral side of the ejection ports  8  and thus has a U-shape in cross section, it is possible to more securely block water being in a bumping state in the bottom portion of the housing  2 . 
         [0085]    Furthermore, since the bottom surface  7   a  of the blocking portion  7  is an inclined surface, droplets of water that has been carried up on the blocking portion  7  can be allowed to drip swiftly into the housing  2 . The bottom surface  7   a  may also be formed so as to be inclined downward toward the lid portion  2   b  or toward lateral sides (horizontal direction as facing the lid portion  2   b ). 
         [0086]    Furthermore, since the ejection ports  8  protrude into the housing  2  and overlap the blocking portion  7  in a planar view, it is possible to more securely block water being in a bumping state in the bottom portion of the housing  2 . 
         [0087]    Furthermore, since the lower inner wall surface of each of the ejection ports  8  is inclined downward in a direction toward the lid portion  2   b , condensation water produced at the ejection ports  8  is collected in the housing  2 , and thus water leakage through the ejection ports  8  can be prevented. 
         [0088]    In this embodiment, the water supply port  3  may be provided in the lid portion  2   b . In such a configuration, the lid portion  2   b  is cooled by water passing through the water supply port  3 , so that the blocking portion  7  is maintained at a further decreased temperature, and thus it is possible to securely prevent water from spurting out through the ejection ports  8 . 
         [0089]    Furthermore, the lid portion  2   b  may be made of a material, such as ceramic, having a thermal conductivity lower than that of metal. In such a configuration, heat transfer from the main body portion  2   a  having the steam generating heaters  4  to the lid portion  2   b  is suppressed, so that the blocking portion  7  is maintained at a further decreased temperature, and thus it is possible to securely prevent water from spurting out through the ejection ports  8 . Furthermore, the ejection ports  8  may be provided in the lid portion  2   b.    
         [0090]    A configuration is also possible in which the lid portion  2   b  is divided into an upper portion having the blocking portion  7  and a lower portion opposed to the steam generating heaters  4 , and the lower portion of the lid portion  2   b  is attached to the main body portion  2   a  via heat transfer grease or the like. This configuration improves thermal conduction between the lower portion of the lid portion  2   b  and the main body portion  2   a  and thus allows the lower portion of the lid portion  2   b  heated to a high temperature by heat transfer from the main body portion  2   a  to contribute to the evaporation of water. Thus, improved steam generation efficiency can be obtained. 
       INDUSTRIAL APPLICABILITY 
       [0091]    The present invention can be applied to a steam generating device that generates steam and a cooker using the same. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
         
           
               1  Steam generating device 
               2  Housing 
               2   a  Main body portion 
               2   b  Lid portion 
               3  Water supply port 
               4  Steam generating heater 
               5 ,  11   c  Temperature sensor 
               7  Blocking portion 
               8  Ejection port 
               9  Gasket 
               10  Cooker 
               11  Heating chamber 
               12  Circulation duct 
               13  Blow-out port 
               14  Air suction port 
               15  Convection heater 
               16  Circulation fan 
               20  Water supply tank 
               21  Water supply pump 
               22  Main body casing 
               23  Heat shield plate 
               30  Magnetron 
               31  Waveguide 
               32  Antenna 
               33  Electrical equipment portion 
               34  Cooling duct 
               35  Cooling fan 
               36  Air supply duct 
               37  Air supply fan 
               38  Air supply port 
               40  Air discharge duct 
               41  Air discharge port 
               42  Humidity sensor 
               50  Control portion 
               51  Operation portion 
               52  Display portion 
               53  Storage portion 
               54  Timer