Abstract:
An incubator comprising: a culture chamber configured to accommodate culture; a dish structure configured to contain a liquid; an ultrasonic vibrator provided in a part of the dish structure, the ultrasonic vibrator configured to atomize the liquid; and a gas-liquid contact structure configured to bring the atomized liquid into contact with air in the chamber to be cultured.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Japanese Patent Application No. 2010-222369, filed Sep. 30, 2010, of which full contents are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an incubator, and particularly relates to a technology to enable environment control and sterilization control to be performed efficiently for an inside of a culture chamber. 
     2. Description of the Related Art 
     A carbon dioxide (CO 2 ) incubator (hereinafter referred to as “incubator”) is known, which includes a means to supply a CO 2  gas into a chamber containing culture and a sensor to detect density of the CO 2  gas inside a culture chamber (chamber), and controls a supply amount of the CO 2  gas according to the density of the CO 2  gas. 
     In the case of changing culture after cultivation thereof using such an incubator, since the culture itself such as a cell and a microorganism, or a bacterium, a virus, etc., which are parasitic on the culture, adhere to an inner wall of the chamber or float in the chamber, it is necessary to perform sterilization processing for the inside of the chamber so as to avoid contamination of next culture caused by such matters. 
     With respect to a mechanism to sterilize the inside of the chamber, for example, Patent Document 1 (Japanese Laid-Open Patent Publication No. 2010-154792) discloses the CO 2  incubator including: a fan; an ozone generator; an ozone sensor that measures ozone density in a bypass provided long with the chamber; a bypass heater, provided separately from the heater, to heat the inside of the chamber; a first temperature sensor to measure a temperature inside the chamber; a second temperature sensor to measure a temperature in the bypass; a control unit; a water dish to enhance humidity control of air inside the chamber and sterilizing function of ozone gas; etc. 
     Further, Patent Document 2 (Japanese Laid-Open Patent Publication No. 2010-154793) discloses a CO 2  incubator including: a chamber to accommodate culture and a door to block an opening of the chamber, which can freely be opened or closed; a valve to take CO 2  gas supplied from the outside into the chamber; a fan to circulate air inside the chamber; an ultraviolet lamp to emit ultraviolet rays, etc., and describes that it is provided with a sterilizing gas generating device in the chamber that generate gas having a sterilizing effect (hydrogen peroxide gas, ozone gas) when sterilization processing is performed for an inside of the chamber. 
     In order to properly maintain the humidity of the air inside the chamber using the water dish as described in Patent Document 1, it is necessary to perform control so that a proper amount of water is retained in the water dish. Thus, a user of the incubator is required to access the water dish disposed on the bottom face of the incubator to monitor the remaining amount of the water periodically. To properly control the humidity throughout the inside of the chamber, it is necessary to efficiently evaporate the water in the water dish to be spread throughout the inside of the chamber. 
     In Patent Document 2, the sterilization within the chamber is performed using the sterilizing gas generating device, the sterilizing gas generating device needs to be brought into the chamber, which causes the user to take trouble every time the sterilization processing is performed. 
     The present invention has been conceived in light of such problems and an object thereof is to provide an incubator capable of efficiently performing environment control and sterilization control inside a culture chamber. 
     SUMMARY OF THE INVENTION 
     An incubator according to an aspect of the present invention, includes: a culture chamber configured to accommodate culture; a dish structure configured to contain a liquid; an ultrasonic vibrator provided in a part of the dish structure, the ultrasonic vibrator configured to atomize the liquid; and a gas-liquid contact structure configured to bring the atomized liquid into contact with air in the chamber to be cultured. 
     Other features of the present invention will become apparent from descriptions of this specification and of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For more thorough understanding of the present invention and advantages thereof, the following description should be read in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an external perspective view of an incubator  1  which is to be described as a first embodiment of the present invention as viewed from a front (+X direction); 
         FIG. 2  is an external perspective view of an incubator  1  which is to be described as a first embodiment of the present invention as viewed from a front (+X direction); 
         FIG. 3  is a cross-sectional view of an incubator  1  which is to be described as a first embodiment of the present invention along a line Y-Y′ of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of an incubator  1  which is to be described as a first embodiment of the present invention along a line X-X′ of  FIG. 2 ; 
         FIG. 5  is a block diagram of a control device  100 ; 
         FIG. 6  is a diagram illustrating an operation of an incubator  1  when humidification is performed in an inner box  3 ; 
         FIG. 7  is a diagram illustrating an operation of an incubator  1  when rapid humidification is performed in an inner box  3 ; 
         FIG. 8  is a diagram illustrating an operation of an incubator  1  when sterilization processing is performed in an inner box  3 ; 
         FIG. 9  is a cross-sectional view of an incubator  1  which is to be described as a second embodiment of the present invention; 
         FIG. 10  is a diagram illustrating an operation of an incubator  1  when humidification is performed in an inner box  3 , in an incubator  1  which is to be described as a second embodiment of the present invention; 
         FIG. 11  is a diagram illustrating an operation of an incubator  1  when rapid humidification is performed in an inner box  3 , in an incubator  1  which is to be described as a second embodiment of the present invention; and 
         FIG. 12  is a diagram illustrating an operation of an incubator  1  when sterilization processing is performed in an inner box  3 , in an incubator  1  which is to be described as a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At least the following details will become apparent from descriptions of this specification and of the accompanying drawings. 
     First Embodiment  
       FIGS. 1 to 4  depict an incubator  1  which is to be described as a first embodiment of the present invention. In the following description, a coordinate system is to be set in directions indicated in these drawings. 
       FIG. 1  is an external perspective view of an incubator  1  as viewed from the front (+X direction).  FIG. 2  is an external perspective view of the incubator  1  as viewed from the same direction as in  FIG. 1 , and depicts the incubator  1  in a state where an outer door  22  and an inner door  32 , which will be described later, are closed and a drawer  11 , which will be described later, is stored in a storage unit  12 , which will be described later, provided in an outer box  2 .  FIG. 3  is a cross-sectional view of the incubator  1  along a line Y-Y′ of  FIG. 2 .  FIG. 4  is a cross-sectional view of the incubator  1  along a line X-X′ of  FIG. 2 . 
     As illustrated in these drawings, the incubator  1  includes the outer box  2 , an inner box  3  provided inside the outer box  2 , and a drawer structure (drawer  11  and storage unit  12 ) provided below (−Z direction) the inner box  3 . 
     The outer box  2  is a box substantially of a rectangular parallelepiped shape, which is made of a material such as stainless steel. The inner box  3  is a box substantially of a rectangular parallelepiped shape, which is slightly smaller than an external form of the outer box  2  and is made of a material such as stainless steel. As illustrated in  FIGS. 3 and 4 , the inner box  3  includes a backboard  311 , two sideboards  312  and  313  opposed to each other, and a ceiling board  314 . A structure to support the inner box  3  in the incubator  1  is omitted from the drawings. 
     A heat insulating material  5  is filled between the outer box  2  and the inner box  3 . An opening  21  is formed on a side face on the +X side of the outer box  2 , and two doors (outer door  22  and inner door  32 ) to block this opening  21  to keep air-tightness inside the incubator  1  are mounted on the outer box  2  by way of hinges, etc. The outer door  22  and the inner door  32  can adopt a structure (reversible structure) capable of opening and closing whether a pivot is positioned on the right side or on the left side thereof. 
     The outer door  22  is made of a material such as stainless steel, is substantially of a rectangular shape slightly greater in external form than the inner door  32 , and has the heat insulating material filled in the inside. Along the inner periphery of the outer door  22 , packing  23  is provided to ensure the air-tightness in the incubator  1 . The inner door  32  is a board made of a transparent material such as resin and glass substantially in a rectangular shape. In such a part of the periphery of the opening  21  of the outer box  2  that abuts on the inner door  32 , packing  33  is provided to ensure the air-tightness inside the incubator  1 . 
     In an internal space (chamber) of the inner box  3 , a plurality of shelf boards  6  are provided to place culture such as cells and microorganisms. Around the shelf boards  6 , a case  41  is provided that is configured including a backboard  411  disposed at the back (−X side) of the shelf boards  6 , two sideboards  412  and  413  disposed on both sides (±Y direction) of the shelf boards  6 , and a ceiling board  414  disposed over (+Z direction) the shelf boards  6 . The case  41  is made of a material such as stainless steel. 
     On the faces of the sideboards  412  and  413 , a large number of air holes  48  are formed by a punching process, etc. In the following description, the space inside the case  41  will be referred to as a culture chamber  40 . A structure to support the case  41  in the incubator  1  is omitted from the drawings. 
     The drawer  11  is a box substantially of a rectangular parallelepiped shape, which is made of a material such as stainless steel and resin. On both side faces  111  and  112  of the drawer  11  (and in corresponding positions of the storage unit  12 ), a rail structure  13  is provided to support the drawer  11  so as to be able to be pulled out or be pushed in smoothly with respect to the storage unit  12 . 
     On the front side (+X side) of a front panel  113  of the drawer  11 , a handle  114  is provided that serves as a handling part when the user pulls out or pushes in the drawer  11 . Along the periphery of the inner side (−X side) of the front panel  113  of the drawer  11 , packing  36  is provided to ensure air-tightness inside the incubator  1 . 
     As illustrated in  FIG. 3 , a first clearance space  51  is formed between the sideboard  412  of the case  41  and the sideboard  312  of the inner box  3 . A second clearance space  52  connected to the first clearance space  51  is formed between the case  41  (lowermost shelf board  6  of the case  41 ) and the drawer  11 . A third clearance space  53  connected to the second clearance space  52  is formed between the sideboard  413  of the case  41  and the sideboard  313  of the inner box  3 . Further, a fourth clearance space  54  connected to the third clearance space  53  and the first clearance space  51  is formed between the ceiling board  414  and the ceiling board  314  of the inner box  3  described above. Around the shelf boards  6 , a duct  50  through which an air circulating in the inner box  3  flows is formed by the first to the fourth clearance spaces  51  to  54 . 
     As illustrated in the drawing, a fan  42  (fan motor, multi-blade fan, etc.) is provided in a flow path of the duct  50  (in the first clearance space  51  in the same drawing). When performing a cultivation operation using the incubator  1  or the sterilization processing for the inside of the incubator  1 , the rotation of the fan  42  generates an air flow circulating in the duct  50  or in the culture chamber  40 . On the top face side of the ceiling board  414  in the duct  50 , a heater  43  to heat the air flowing through the duct  50  is provided. 
     As illustrated in  FIG. 3  or  4 , a dish structure  18  is provided inside the drawer  11 . The dish structure  18  includes a first containing unit  181  demarcated by a first bottom face  1811  and a first side face  1812  set up around the first bottom face  1811 . The dish structure  18  also includes a second containing unit  182  provided in the first containing unit  181  and demarcated by a second bottom face  1821 , raised up by a predetermined height from the first bottom face  1811  of the first containing unit  181 , and a second side face  1822 , set up around the second bottom face  1821  and having a height shorter than that of the first side face  1811 . 
     The first bottom face  1811  of the first containing unit  181  is provided with a heater  192  to heat a liquid contained in the dish structure  18 . The second bottom face  1821  of the second containing unit  182  is provided with an ultrasonic vibrator  191 . 
     In addition to the above configuration, the incubator  1  includes a control device  100  to perform an operation control, state monitoring, etc., of the incubator  1 . As illustrated in  FIG. 4 , the control device  100  is accommodated in a cover  101  disposed on the back side of the outer box  2 , the outer door  22 , etc., for example. 
       FIG. 5  is a block diagram of the control device  100 . As illustrated in the drawing, the control device  100  includes a central processing device  151 , a memory  152 , a timing device  153 , an input device  154 , a display device  155 , a sensor group  156 , a flow control device  157 , a fan control device  158 , a vibrator control device  159 , and a heater control device  160 . 
     The central processing device  151  is configured using a CPU (Central Processing Unit), an MPU (Microprocessor Unit), etc. The central processing device  151  has a function of performing overall control of the control device  100 . 
     The memory  152  is a volatile or non-volatile memory device that stores programs to be read and executed by the central processing device  151  and data to be referred to by the central processing device  151 . 
     The timing device  153  generates time-related data such as date and time information and elapsed time information. The information generated by the timing device  153  is used for a function of drive control based on the timing information, which the flow control device  157 , the fan control device  158 , the vibrator control device  159 , and the heater control device  160  have, for example. 
     The input device  154  is a user interface that accepts, from the user, input information such as information to set the operation of the incubator  1 , and is a keyboard, a touch panel, etc, for example. The central processing device  151  controls the flow control device  157 , the fan control device  158 , the vibrator control device  159 , and the heater control device  160 , based on the information accepted by the input device  154 . 
     The display device  155  is a user interface that provides the user with an operational status, monitoring information, etc., of the incubator  1  as visual information, and is a liquid crystal display, an organic EL panel, etc. , for example. The central processing device  151  acquires the operational status and the monitoring information from the flow control device  157 , the fan control device  158 , the vibrator control device  159 , and the heater control device  160 , and outputs the acquired information to the display device  155 . 
     The sensor group  116  includes a temperature sensor to measure a temperature inside the inner box  3 , a humidity sensor to measure a humidity inside the inner box  3 , a water level sensor to detect a level of the liquid retained in the first containing unit  181  and the second containing unit  182 , and a carbon dioxide (hereinafter referred to as CO 2 ) sensor to measure a density of CO 2  inside the inner box  3 . The group may further include an oxygen (hereinafter referred to as  0   2 ) sensor to measure a density of O 2  inside the inner box  3 , a nitrogen (hereinafter referred to as N 2 ) sensor to measure a density of N 2  inside the inner box  3 , a hydrogen peroxide (hereinafter described as H 2 O 2 ) sensor to measure a density of H 2 O 2  inside the inner box  3 , etc. 
     The flow control device  157  controls (PID (Proportional Integral Derivative) control, etc.) a solenoid valve (not shown) provided in a pathway of a gas supply tube (not shown), having one end thereof provided to run through from the outside of the outer box  2  into the inner box  3  and having the other end thereof connected to a gas supply source such as a gas bomb; and controls the supply of gas  8  (CO 2 ,  0   2 , etc.) from a nozzle into the inner box  3 . Based on the information acquired from the sensor group  116 , the central processing device  151  controls the flow control device  157  so that a gas density (CO 2  density, O 2  density, etc.) inside the culture chamber  40  becomes appropriate. 
     The fan control device  158  controls (PID control, etc.) the number of rotations of the fan  42 . Based on the information acquired from the sensor group  116 , the central processing device  151  controls the fan control device  158  so that the speed of the air flowing through the duct  50  becomes appropriate. 
     The vibrator control device  159  controls (PID control, etc.) an operation (on/off, frequency, etc.) of the ultrasonic vibrator  191 . Based on the information acquired from the sensor group  116 , the central processing device  151  controls the vibrator control device  159  so that the humidity and the density of H 2 O 2  inside the culture chamber  40  become appropriate. 
     The heater control device  160  controls (PID control, thermistor control, etc.) operations (on/off, temperature, etc.) of the heater  43  and the heater  192 . Based on the information acquired from the sensor group  116 , the central processing device  151  controls the heater control device  160  so that the temperature of the liquid retained in the dish structure  18 , the humidity inside the culture chamber  40 , the temperature of the air flowing through the duct  50 , etc., become appropriate. 
     &lt;Operation when Humidification is Performed&gt; 
       FIG. 6  is a cross-sectional view of the incubator  1  along a line Y-Y′ of  FIG. 2  and also is a diagram illustrating an operation of the incubator  1  when the humidification is performed in the inner box  3 . The operation illustrated in the drawing is performed when the humidity inside the culture chamber  40  is lower than an appropriate value (target value), for example. 
     When the humidification is performed in the inner box  3 , firstly, a necessary amount of water is to be supplied beforehand to the first containing unit  181  of the dish structure  18 . The user can conveniently supply water to the first containing unit  181  by pulling out the drawer  11 . The user can easily check the remaining amount of the water retained in the first containing unit  181  by pulling out the drawer  11 . 
     As illustrated in  FIG. 6 , when the humidification is performed in the inner box  3 , the fan  42  is rotated to circulate the air. As indicated by an arrow in the drawing, this air current causes the air to continuously flow from the first clearance space  51  into the second clearance space  52 , and the air flowing into the second clearance space  52  gets in contact with the water retained in the first containing unit  181 . The air moisturized by getting in contact with the water is pressed by the air subsequently flowing from the first clearance space  51 , thereby flowing into the third clearance space  53 . 
     As described above, a large number of air holes  48  are formed on the face of the sideboard  413 . For this reason, a portion of the air flowing into the third clearance space  53  flows upward in the third clearance space  53  toward the fourth clearance space  53 , while other portion of the air flowing therein flows into the culture chamber  40  through the air holes  48  formed on the sideboard  413 . Here, in the first clearance space  51 , a downward current is generated by an operation of the fan  42 , and thus the first clearance space  51  has a negative pressure as compared with the third clearance space  52 . Therefore, the air in the third clearance space  53  is efficiently taken into the culture chamber  40  thereby generating an air current (air current in the +Y→−Y direction) in the culture chamber  40 , and such an air is discharged to the first clearance space  51  thereby joining the downward current flowing in the first clearance space  51 . 
     As such, with the incubator  1  according to an embodiment of the present invention, when the humidification is performed, the water is efficiently supplied to the air circulating in the duct  50  as well as the moisturized air containing a moisture content can efficiently be sent into the culture chamber  40 , thereby being able to efficiently control the humidity in the culture chamber  40 . 
     &lt;Operation when Rapid Humidification is Performed&gt; 
       FIG. 7  is, similarly to  FIG. 3 , a cross-sectional view of the incubator  1  along the line Y-Y′ of  FIG. 2  and is a diagram illustrating an operation of the incubator  1  when rapid humidification is performed in the inner box  3 . The rapid humidification operation is performed when the humidity inside the culture chamber  40  is lower than the appropriate value (target value) and the rapid humidification in the inner box  3  is desired. This is, for example, a case where the humidity inside is lowered by the opening and closing of the door. 
     When rapid humidification is performed in the inner box  3  in the same manner as in the case of the humidification described above, the water is supplied beforehand to the first containing unit  181  of the dish structure  18 . When the rapid humidification is performed, unlike the case of the humidification, the water is to be supplied to the first containing unit  181  to such an extent that a sufficient amount of water flows in the second containing unit  182 . That is to say, when the humidification is performed, the water is supplied to both of the first containing unit  181  and the second containing unit  182 . When the water level sensor detects that the water level of the second containing unit  182  has dropped to a predetermined water level, the ultrasonic vibrator  191  stops operating so as not to operate with no water therein. 
     Similarly to the case where the humidification is performed, when the rapid humidification is performed, the fan  42  is rotated to circulate the air in the duct  50  and the culture chamber  40 . Additionally, the ultrasonic vibrator  191  is operated when the rapid humidification is performed. When the ultrasonic vibrator  191  is operated, the water retained in the second containing unit  182  is atomized (turned into mist) to form a water column at a water surface of the second containing unit  182 , and the air flowing in the second clearance space  52  gets in contact with water drops (mist) of the water column. 
     Thus, since the incubator  1  according to an embodiment of the present invention includes a structure in which the air circulating in the duct  50  and the water atomized by the ultrasonic vibrator  191  are brought into contact with each other (gas-liquid contact structure), thereby increasing an area of contact between the air flowing in the second clearance space  52  and the water, so that moisture can be supplied efficiently and positively to the air flowing in the second clearance space  52 . This makes it possible to efficiently send the moisturized air containing the water to the culture chamber  40 , thereby being able to efficiently perform the humidity control inside the culture chamber  40 . 
     &lt;Operation when Sterilization Processing is Performed&gt; 
       FIG. 8  is, similarly to  FIG. 3 , a cross-sectional view of the incubator  1  along the line Y-Y′ of  FIG. 2 , and is a diagram illustrating an operation of the incubator  1  when sterilization processing is performed in the inner box  3 . 
     As illustrated in the drawing, when the sterilization processing is performed, a processing liquid for sterilization such as an aqueous solution of hydrogen peroxide is retained in the second containing unit  182  of the dish structure  18 . The user can conveniently supply the processing liquid for sterilization to the second containing unit  182  by pulling out the drawer  11  from the storage unit  12 . If a volume of the second containing unit  182  is determined so as to be equal to an amount required for one time of the sterilization processing, for example, a measuring work can be omitted. 
     Similarly to the case where the humidification is performed or the case where the rapid humidification is performed, when the sterilization processing is performed, the fan  42  is rotated to circulate the air in the duct  50  and the culture chamber  40 . Similarly to the case where the rapid humidification is performed, the ultrasonic vibrator  191  is operated to positively bring the processing liquid for sterilization retained in the second containing unit  182  into contact with the air flowing in the second clearance space  51 . 
     Similarly to the case where the rapid humidification is performed, a water column of the processing liquid for sterilization is formed by the ultrasonic vibrator  191 , thereby increasing the area of contact between the air flowing in the second clearance space  52  and the processing liquid for sterilization, which makes it possible to efficiently supply the processing liquid for sterilization to the air flowing in the second clearance space  52 . 
     As such, with the incubator  1  according to an embodiment of the present invention, when the rapid humidification is performed, the processing liquid for sterilization can be supplied efficiently and positively to the air circulating inside the duct  50  as well as the air containing the processing liquid for sterilization can efficiently be sent into the duct  50  and the culture chamber  40 , thereby being able to efficiently perform the sterilization securely and efficiently inside the duct  50  and the culture chamber  40 . 
     The incubator  1  according to an embodiment of the present invention is capable of flexibly responding to the need for supply to the incubator  1  of a plurality of types of liquids with required supply quantities different from on another. The same ultrasonic vibrator can be used for the atomization of both a first liquid and a second liquid. Thus, it is unnecessary to provide the ultrasonic vibrator  191  separately for each of the liquids, thereby being able to simplify a configuration and a manufacturing process, and reduce manufacturing costs, etc., in the incubator  1 . 
     In the incubator  1  according to an embodiment of the present invention, either the humidification or the rapid humidification can be selected to perform humidification processing in the culture chamber  40 , thereby being able to respond to the user&#39;s needs in a flexible manner. Further, power consumption when the incubator  1  is operated can be reduced by not performing unnecessary rapid humidification. 
     Second Embodiment  
       FIG. 9  is a cross-sectional view of the incubator  1  which is to be described as a second embodiment of the present invention. The incubator  1  according to a second embodiment of the present invention differs from the incubator  1  according to a first embodiment of the present invention in a structure inside the inner box  3  and an air circulation path inside the inner box  3 , but is the same as the incubator  1  according to a first embodiment of the present invention in other configurations. 
     As illustrated in the drawing, the incubator  1  according to a second embodiment of the present invention does not include a configuration corresponding to the case  41  in the incubator  1  according to a first embodiment of the present invention. In the incubator  1  according to a second embodiment of the present invention, a back face board  45  is provided on the back face side (−Y side) of the inner box  3  and is disposed in parallel with the backboard  311  of the inner box  3 , extending over the shelf boards  6  as a whole. As illustrated in the drawing, the duct  50  is formed on the back face side in the inner box  3  by this back face board  45 . 
     On the upper (+Z direction) part of the back face board  45 , a large number of air holes  451  are formed by the punching process, etc. At the end portion of the upper (+x direction) part of the duct  50 , the fan  42  (fan motor, multi-blade fan, etc.) is provided that takes in a gas from the space in which the shelf boards  6  are disposed (hereinafter this space is referred to as the culture chamber  40 ) through the air holes  451 , and sends out the taken-in gas downward inside the duct  50 . 
     The lower end of the back board  411  is distanced from the dish structure  18  by a predetermined space, thereby connecting the duct  50  with the culture chamber  40  below the back face board  45 . A cover  47  is provided between the lowermost shelf board  6  and the drawer  11 . A large number of air holes  471  are formed on the substantially horizontal face of the cover  47 . In the incubator  1  according to a second embodiment of the present invention, the cover  47  is not necessarily an indispensable constituent element. On a face of each of the shelf boards  6 , a large number of air holes  49  to allow the air current to pass therethrough in the vertical direction (±Z direction) are formed by the punching process, etc. 
     &lt;Operation when Humidification is Performed&gt; 
       FIG. 10  is a diagram illustrating an operation of the incubator  1  according to a second embodiment of the present invention when humidification is performed. The operation illustrated in the drawing is performed, when the humidity inside the culture chamber  40  is lower than the appropriate value (target value), for example. Similarly to the incubator  1  according to a first embodiment of the present invention, when the humidification is performed in the inner box  3 , a necessary amount of water is to be supplied beforehand to the first containing unit  181  of the dish structure  18 . 
     As illustrated in the drawing, when the humidification is performed, the fan  42  is rotated to generate a downward air current in the dust  50 . This causes the air of the culture chamber  40  to be taken into the duct  50  from the upper part of the duct  50  and the taken-in air goes downward in the duct  50  to be sent to the lower part of the duct  50 . 
     The air sent to the lower part of the duct  50  flows down from the lower part of the duct  50  toward the liquid surface of the first containing unit  181 , and the air flowing down from the duct  50  gets in contact with the water retained in the first containing unit  181 . Through contact with the water, the air contains moisture and the air containing the moisture pushed out by the air subsequently flowing down from the duct  50 , to be changed into an upward current, thereby flowing into the culture chamber  40  through the air holes  471  of the cover  47 . The air flowing into the culture chamber  40  goes upward through the air holes  49  of the shelf boards  6 , is sent to the upper part of the inner box  3 , and is taken in again through the air holes  451  of the back face board  45  to flow downward. 
     As such, with the incubator  1  according to an embodiment of the present invention, when the humidification is performed, the moisture is efficiently supplied to the air flowing down from the duct  50  as well as the moisturized air containing the water is efficiently sent into the culture chamber  40 , thereby being able to efficiently control the humidity in the culture chamber  40 . 
     Further, with the incubator  1  according to a second embodiment of the present invention, the duct  50  to circulate the gas can be configured only by the back board  411 , without the sideboards  412  and  413 , the ceiling board  414 , etc., being provided as in the incubator  1  according to a first embodiment of the present invention. 
     &lt;Operation when Rapid Humidification is Performed&gt; 
       FIG. 11  is a diagram illustrating an operation of the incubator  1  according to a second embodiment of the present invention when the rapid humidification is performed. The operation illustrated in the drawing is performed when the humidity inside the culture chamber  40  is lower than the appropriate value (target value) and the rapid humidification in the inner box  3  is desired, for example. 
     When the rapid humidification is performed in the inner box  3 , similarly to the case of the humidification described above, the water is to be supplied beforehand to the first containing unit  181  of the dish structure  18 . When the rapid humidification is performed, unlike the case of the humidification, the water is to be supplied to the first containing unit  181  to such an extent that a sufficient amount of water flows in the second containing unit  182 . 
     Similarly to the case where the humidification is performed, when the rapid humidification is performed, the fan  42  is rotated to circulate the air in the duct  50  and the culture chamber  40 . Additionally, the ultrasonic vibrator  191  is operated when the rapid humidification is performed. The ultrasonic vibrator  191  is operated, to form a water column on the water surface of the second containing unit  182 , and the air flowing down from the duct  50  gets in contact with water drops (mist) of this water column. Thus, an area of contact between the air flowing down from the duct  50  and the water is increased, thereby being able to efficiently supply moisture to the air flowing down from the duct  50 . 
     As such, with the incubator  1  according to an embodiment of the present invention, when the rapid humidification is performed, moisture is supplied efficiently and positively to the air flowing down from the duct  50 . Therefore, the moisturized air containing the water can be efficiently sent to the culture chamber  40 , thereby being able to efficiently perform the humidity control inside the culture chamber  40 . 
     &lt;Operation when Sterilization Processing is Performed&gt; 
       FIG. 12  is a diagram illustrating the operation of the incubator  1  according to a second embodiment of the present invention when the sterilization processing is performed. As illustrated in the drawing, when the sterilization processing is performed, the processing liquid for sterilization such as the aqueous solution of hydrogen peroxide is retained in the second containing unit  182 . The user can conveniently supply the processing liquid for sterilization to the second containing unit  182  by pulling out the drawer  11 . If a volume of the second containing unit  182  is set so as to be equal to an amount required for one time of the sterilization processing, for example, a measuring work can be omitted. 
     Similarly to the case where the humidification is performed or the case where the rapid humidification is performed, when the sterilization processing is performed, the fan  42  is rotated to circulate the air in the duct  50  and the culture chamber  40 . Similarly to the case where the rapid humidification is performed, the ultrasonic vibrator  191  is operated to positively bring the processing liquid for sterilization retained in the second containing unit  182  into contact with the air flowing down from the duct  50 . 
     Similarly to the case where the rapid humidification is performed, a water column of the processing liquid for sterilization is formed by the ultrasonic vibrator  191 , thereby increasing the area of contact between the air flowing down from the duct  50  and the processing liquid for sterilization, which makes it possible to efficiently supply the processing liquid for sterilization to the air flowing down from the duct  50 . 
     As such, with the incubator  1  according to an embodiment of the present invention, when the rapid humidification is performed, the processing liquid for sterilization is supplied efficiently and positively to the air circulating inside the duct  50  as well as the air containing the processing liquid for sterilization is efficiently sent into the duct  50  and the culture chamber  40 , thereby being able to efficiently perform the sterilization processing securely and efficiently inside the duct  50  and the culture chamber  40 . 
     The above embodiments of the present invention are simply for facilitating the understanding of the present invention and are not in any way to be construed as limiting the present invention. The present invention may variously be changed or altered without departing from its spirit and encompass equivalents thereof. 
     For example, in order to prevent contamination inside the culture chamber  40  more securely, the incubator  1  may be provided with an ultraviolet germicidal lamp, an ozone generator, etc.